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Sexual differences and early eruption timing of the permanent dentition in Mexican adolescents- a comparison with the Caucasian standards

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Sexual differences and early eruption timing of the permanent dentition in Mexican adolescents- a comparison with the Caucasian standards

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SEXUAL DIFFERENCES AND EARLY ERUPTION TIMING OF THE PERMANENT
DENTITION IN MEXICAN ADOLESCENTS- A COMPARISON WITH THE
CAUCASIAN STANDARDS

by

Jenniffer Rojas

A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(CRANIOFACIAL BIOLOGY)

May 2008

Copyright 2008 Jenniffer Rojas
ii
TABLE OF CONTENTS

List of Tables iii

List of Figures xi

Abstract xv

Chapter 1: Introduction 1

Chapter 2: Review of Literature 5

Chapter 3: Research questions 14

Chapter 4: Materials and Methods 15

Chapter 5: Results 19
Females age 8,9 19
Males age 8,9 34
Females age 10 50
Males age 10 66
Females age 11 83
Males age 11 99
Females age 12 115
Males age 12 132

Chapter 6: Limitations 148

Chapter 7: Discussion 149

Chapter 8: Summary 163

Chapter 9: Conclusions 166

Bibliography 167

iii
LIST OF TABLES
Table 1. Chronology of tooth development, Permanent dentition. 3
Table 2: Sample data collection sheet 18
Table 3: Case Processing Summary- Upper canines; Females age 8,9 19
Table 4: Chi-Square Test- Upper canines, Females age 8,9 20
Table 5: Crosstabulation- Upper canines; Females age 8,9 20
Table 6: Case Processing Summary- Lower canines; Females age 8,9 21
Table 7: Crosstabulation- Lower canines; Females age 8,9 22
Table 8: Chi-Square Test- Lower canines, Females age 8,9 22
Table 9: Case Processing Summary- Upper premolars; Females age 8,9 23
Table 10: Crosstabulation- Upper premolars; Females age 8,9 24
Table 11: Chi-Square Test- Upper premolars, Females age 8,9 24
Table 12: Case Processing Summary- Lower premolars; Females age 8,9 25
Table 13: Crosstabulation- Lower premolars; Females age 8,9 26
Table 14: Chi-Square Test- Lower premolars, Females age 8,9 26
Table 15: Case Processing Summary- All premolars; Females age 8,9 27
Table 16: Crosstabulation- All premolars; Females age 8,9 28
Table 17: Chi-Square Test- All premolars, Females age 8,9 28
Table 18: Case Processing Summary- Upper second molars; Females age 8,9 29
Table 19: Crosstabulation- Upper second molars; Females age 8,9 30
Table 20: Chi-Square Test- Upper second molars, Females age 8,9 30
Table 21: Case Processing Summary- Lower second molars; Females age 8,9 31
Table 22: Crosstabulation- Lower second molars; Females age 8,9 32
iv
Table 23: Chi-Square Test- Lower second molars, Females age 8,9 32
Table 24: Case Processing Summary- Upper canines; Males age 8,9 34
Table 25: Crosstabulation- Upper canines; Males age 8,9 35
Table 26: Chi-Square Test- Upper canines, Males age 8,9 35
Table 27: Case Processing Summary- Lower canines; Males age 8,9 36
Table 28: Crosstabulation- Lower canines; Males age 8,9 37
Table 29: Chi-Square Test- Lower canines, Males age 8,9 37
Table 30: Case Processing Summary- Upper premolars; Males age 8,9 38
Table 31: Crosstabulation- Upper premolars; Males age 8,9 39
Table 32: Chi-Square Test- Upper premolars, Males age 8,9 39
Table 33: Case Processing Summary- Lower premolars; Males age 8,9 40
Table 34: Crosstabulation- Lower premolars; Males age 8,9 41
Table 35: Chi-Square Test- Lower premolars, Males age 8,9 41
Table 36: Case Processing Summary- All premolars; Males age 8,9 43
Table 37: Crosstabulation- All premolars; Males age 8,9 43
Table 38: Chi-Square Test- All premolars, Males age 8,9 44
Table 39: Case Processing Summary- Upper second molars; Males age 8,9 45
Table 40: Crosstabulation- Upper second molars; Males age 8,9 45
Table 41: Chi-Square Test- Upper second molars, Males age 8,9 46
Table 42: Case Processing Summary- Lower second molars; Males age 8,9 47
Table 43: Crosstabulation- Lower second molars; Males age 8,9 47
Table 44: Chi-Square Test- Lower second molars, Males age 8,9 48
Table 45: Chi-Square Test- All erupted teeth; Females and Males age 8,9 49
v
Table 46: Case Processing Summary- Upper canines; Females age 10 50
Table 47: Crosstabulation- Upper canines; Females age 10 51
Table 48: Chi-Square Test- Upper canines, Females age 10 51
Table 49: Case Processing Summary- Lower canines; Females age 10 52
Table 50: Crosstabulation- Lower canines; Females age 10 53
Table 51: Chi-Square Test- Lower canines, Females age 10 53
Table 52: Case Processing Summary- Upper premolars; Females age 10 55
Table 53: Crosstabulation- Upper premolars; Females age 10 55
Table 54: Chi-Square Test- Upper premolars, Females age 10 56
Table 55: Case Processing Summary- Lower premolars; Females age 10 57
Table 56: Crosstabulation- Lower premolars; Females age 10 57
Table 57: Chi-Square Test- Lower premolars, Females age 10 58
Table 58: Case Processing Summary- All premolars; Females age 10 59
Table 59: Crosstabulation- All premolars; Females age 10 60
Table 60: Chi-Square Test- All premolars, Females age 10 60
Table 61: Case Processing Summary- Upper second molars; Females age 10 61
Table 62: Crosstabulation- Upper second molars; Females age 10 62
Table 63: Chi-Square Test- Upper second molars, Females age 10 62
Table 64: Case Processing Summary- Lower second molars; Females age 10 63
Table 65: Crosstabulation- Lower second molars; Females age 10 64
Table 66: Chi-Square Test- Lower second molars, Females age 10 64
Table 67: Case Processing Summary- Upper canines; Males age 10 66
Table 68: Crosstabulation- Upper canines; Males age 10 67
vi
Table 69: Chi-Square Test- Upper canines, Males age 10 67
Table 70: Case Processing Summary- Lower canines; Males age 10 68
Table 71: Crosstabulation- Lower canines; Males age 10 69
Table 72: Chi-Square Test- Lower canines, Males age 10 69
Table 73: Case Processing Summary- Upper premolars; Males age 10 70
Table 74: Crosstabulation- Upper premolars; Males age 10 71
Table 75: Chi-Square Test- Upper premolars, Males age 10 71
Table 76: Case Processing Summary- Lower premolars; Males age 10 72
Table 77: Crosstabulation- Lower premolars; Males age 10 73
Table 78: Chi-Square Test- Lower premolars, Males age 10 73
Table 79: Case Processing Summary- All premolars; Males age 10 75
Table 80: Crosstabulation- All premolars; Males age 10 75
Table 81: Chi-Square Test- All premolars, Males age 10 76
Table 82: Case Processing Summary- Upper second molars; Males age 10 77
Table 83: Crosstabulation- Upper second molars; Males age 10 78
Table 84: Chi-Square Test- Upper second molars, Males age 10 78
Table 85: Case Processing Summary- Lower second molars; Males age 10 79
Table 86: Crosstabulation- Lower second molars; Males age 10 80
Table 87: Chi-Square Test- Lower second molars, Males age 10 80
Table 88: Chi-Square Test- All erupted teeth; Females and Males age 10 82
Table 89: Case Processing Summary- Upper canines; Females age 11 83
Table 90: Crosstabulation- Upper canines; Females age 11 84
Table 91: Chi-Square Test- Upper canines, Females age 11 84
vii
Table 92: Case Processing Summary- Lower canines; Females age 11 85
Table 93: Crosstabulation- Lower canines; Females age 11 86
Table 94: Chi-Square Test- Lower canines, Females age 11 86
Table 95: Case Processing Summary- Upper premolars; Females age 11 87
Table 96: Crosstabulation- Upper premolars; Females age 11 88
Table 97: Chi-Square Test- Upper premolars, Females age 11 88
Table 98: Case Processing Summary- Lower premolars; Females age 11 89
Table 99: Crosstabulation- Lower premolars; Females age 11 90
Table 100: Chi-Square Test- Lower premolars, Females age 11 90
Table 101: Case Processing Summary- All premolars; Females age 11 92
Table 102: Crosstabulation- All premolars; Females age 11 92
Table 103: Chi-Square Test- All premolars, Females age 11 93
Table 104: Case Processing Summary- Upper second molars; Females age 11 94
Table 105: Crosstabulation- Upper second molars; Females age 11 95
Table 106: Chi-Square Test- Upper second molars, Females age 11 95
Table 107: Case Processing Summary- Lower second molars; Females age 11 97
Table 108: Crosstabulation- Lower second molars; Females age 11 97
Table 109: Chi-Square Test- Lower second molars, Females age 11 98
Table 110: Case Processing Summary- Upper canines; Males age 11 99
Table 111: Crosstabulation- Upper canines; Males age 11 100
Table 112: Chi-Square Test- Upper canines, Males age 11 100
Table 113: Case Processing Summary- Lower canines; Males age 11 102
Table 114: Crosstabulation- Lower canines; Males age 11 102
viii
Table 115: Chi-Square Test- Lower canines, Males age 11 103
Table 116: Case Processing Summary- Upper premolars; Males age 11 104
Table 117: Crosstabulation- Upper premolars; Males age 11 104
Table 118: Chi-Square Test- Upper premolars, Males age 11 105
Table 119: Case Processing Summary- Lower premolars; Males age 11 106
Table 120: Crosstabulation- Lower premolars; Males age 11 106
Table 121: Chi-Square Test- Lower premolars, Males age 11 107
Table 122: Case Processing Summary- All premolars; Males age 11 108
Table 123: Crosstabulation- All premolars; Males age 11 108
Table 124: Chi-Square Test- All premolars, Males age 11 109
Table 125: Case Processing Summary- Upper second molars; Males age 11 110
Table 126: Crosstabulation- Upper second molars; Males age 11 110
Table 127: Chi-Square Test- Upper second molars, Males age 11 111
Table 128: Case Processing Summary- Lower second molars; Males age 11 112
Table 129: Crosstabulation- Lower second molars; Males age 11 112
Table 130: Chi-Square Test- Lower second molars, Males age 11 113
Table 131: Chi-Square Test- All erupted teeth; Females and Males age 11 114
Table 132: Case Processing Summary- Upper canines; Females age 12 116
Table 133: Crosstabulation- Upper canines; Females age 12 117
Table 134: Chi-Square Test- Upper canines, Females age 12 117
Table 135: Case Processing Summary- Lower canines; Females age 12 118
Table 136: Crosstabulation- Lower canines; Females age 12 119
Table 137: Chi-Square Test- Lower canines, Females age 12 119
ix
Table 138: Case Processing Summary- Upper premolars; Females age 12 120
Table 139: Crosstabulation- Upper premolars; Females age 12 121
Table 140: Chi-Square Test- Upper premolars, Females age 12 121
Table 141: Case Processing Summary- Lower premolars; Females age 12 122
Table 142: Crosstabulation- Lower premolars; Females age 12 123
Table 143: Chi-Square Test- Lower premolars, Females age 12 123
Table 144: Case Processing Summary- All premolars; Females age 12 124
Table 145: Crosstabulation- All premolars; Females age 12 125
Table 146: Chi-Square Test- All premolars, Females age 12 125
Table 147: Case Processing Summary- Upper second molars; Females age 12 127
Table 148: Crosstabulation- Upper second molars; Females age 12 127
Table 149: Chi-Square Test- Upper second molars, Females age 12 128
Table 150: Case Processing Summary- Lower second molars; Females age 12 129
Table 151: Crosstabulation- Lower second molars; Females age 12 130
Table 152: Chi-Square Test- Lower second molars, Females age 12 130
Table 153: Case Processing Summary- Upper canines; Males age 12 132
Table 154: Crosstabulation- Upper canines; Males age 12 133
Table 155: Chi-Square Test- Upper canines, Males age 12 133
Table 156: Case Processing Summary- Lower canines; Males age 12 134
Table 157: Crosstabulation- Lower canines; Males age 12 135
Table 158: Chi-Square Test- Lower canines, Males age 12 135
Table 159: Case Processing Summary- Upper premolars; Males age 12 136
Table 160: Crosstabulation- Upper premolars; Males age 12 137
x
Table 161: Chi-Square Test- Upper premolars, Males age 12 137
Table 162: Case Processing Summary- Lower premolars; Males age 12 138
Table 163: Crosstabulation- Lower premolars; Males age 12 139
Table 164: Chi-Square Test- Lower premolars, Males age 12 139
Table 165: Case Processing Summary- All premolars; Males age 12 140
Table 166: Crosstabulation- All premolars; Males age 12 141
Table 167: Chi-Square Test- All premolars, Males age 12 141
Table 168: Case Processing Summary- Upper second molars; Males age 12 142
Table 169: Crosstabulation- Upper second molars; Males age 12 143
Table 170: Chi-Square Test- Upper second molars, Males age 12 143
Table 171: Case Processing Summary- Lower second molars; Males age 12 144
Table 172: Crosstabulation- Lower second molars; Males age 12 145
Table 173: Chi-Square Test- Lower second molars, Males age 12 145
Table 174: Chi-Square Test- All erupted teeth; Females and Males age 12 147
Table 175: Summary of permanent tooth eruption timing 150
Table 176: Results summary 154

xi
LIST OF FIGURES

Fig 1. Primary teeth eruption chart 1

Fig 2. Permanent teeth eruption chart 2

Fig 3. Distribution graph: Females age 8,9 19

Fig 4. Females age 8,9: Upper canines 21

Fig 5. Females age 8,9: Lower canines 23

Fig 6. Females age 8,9: Upper bicuspids 25

Fig 7. Females age 8,9: Lower bicuspids 27

Fig 8. Females age 8,9: At least one upper and one lower bicuspids 29

Fig 9. Females age 8,9: Upper second molars 31

Fig 10. Females age 8,9: Lower second molars 33

Fig 11. Distribution graph: Males age 8,9 34

Fig 12. Males age 8,9: Upper canines 36

Fig 13. Males age 8,9: Lower canines 38

Fig 14. Males age 8,9: Upper bicuspids 40

Fig 15. Males age 8,9: Lower bicuspids 42

Fig 16. Males age 8,9: At least one upper and one lower bicuspids 44

Fig 17. Males age 8,9: Upper second molars 46

Fig 18. Males age 8,9: Lower second molars 48

Fig 19. Differences in dental eruption for Mexican patients age 8,9 49

Fig 20. Distribution graph: Females age 10 50

Fig 21. Females age 10: Upper canines 52

xii
Fig 22. Females age 10: Lower canines 54

Fig 23. Females age 10: Upper bicuspids 56

Fig 24: Females age 10: Lower bicuspids 58

Fig 25. Females age 10: At least one upper and one lower bicuspids 61

Fig 26. Females age 10: Upper second molars 63

Fig 27. Females age 10: Lower second molars 65

Fig 28. Distribution graph: Males age 10 66

Fig 29. Males age 10 :Upper canines 68

Fig 30. Males age 10: Lower canines 70

Fig 31. Males age 10: Upper bicuspids 72

Fig 32. Males age 10: Lower bicuspids 74

Fig 33. Males age 10: At least one upper and one lower bicuspids 76

Fig 34. Males age 10: Upper second molars 79

Fig 35. Males age 10: Lower second molars 81

Fig 36. Differences in dental eruption for Mexican patients age 10 82

Fig 37. Distribution graph: Females age 11 83

Fig 38. Females age 11: Upper canines 85

Fig 39. Females age 11: Lower canines 87

Fig 40. Females age 11: Upper bicuspids 89

Fig 41. Females age 11: Lower bicuspids 91

Fig 42. Females age 11: At least one upper and one lower bicuspid 93

Fig 43. Females age 11: Upper second molars 96

Fig 44. Females age 11: Lower second molars 98
xiii

Fig 45. Distribution graph: Males age 11 99

Fig 46. Males age 11: Upper canines 101

Fig 47. Males age 11: Lower canines 103

Fig 48. Males age 11: Upper bicuspids 105

Fig 49. Males age 11: Lower bicuspids 107

Fig 50. Males age 11: At least one upper and one lower bicuspids 109

Fig 51. Males age 11: Upper second molars 111

Fig 52. Males age 11: Lower second molars 113

Fig 53. Differences in dental eruption for Mexican patients age 11 115

Fig 54. Distribution graph: Females age 12 116

Fig 55. Females age 12: Upper canines 118

Fig 56. Females age 12: Lower canines 120

Fig 57. Females age 12: Upper bicuspids 122

Fig 58. Females age 12: Lower bicuspids 124

Fig 59. Females age 12: At least one upper and one lower bicuspids 126

Fig 60. Females age 12: Upper second molars 128

Fig 61. Females age 12: Lower second molars 131

Fig 62. Distribution graph: Males age 12 132

Fig 63: Males age 12: Upper canines 134

Fig 64: Males age 12: Lower canines 136

Fig 65. Males age 12: Upper bicuspids 138

Fig 66. Males age 12: Lower bicuspids 140

xiv
Fig 67. Males age 12: At least one upper and one lower bicuspids 142

Fig 68. Males age 12: Upper second molars 144

Fig 69. Males age 12: Lower second molars 146

Fig 70. Differences in dental eruption for Mexican patients age 12 147

xv
ABSTRACT

The purpose of this study was to compare the eruption timing of the posterior
permanent dentition in Mexican adolescents in reference to the current standards, and to
determine if sexual dimorphism is present in the Mexican sample. 257 consecutive
records were obtained from a university orthodontic program in Mexico City using
established criteria. The eruption of the posterior secondary dentition was recorded for
subjects from 8 to 12 years of age, and the data compared statistically to the Caucasian
data from a previous study. Significant differences in eruption timing start showing in 8
year old females (p=.044, lower premolars) and 10-year-old males (p=.001, upper
bicuspids). For all age groups, the posterior permanent dentition erupts earlier in
Mexican patients. For the Mexican sample, evidence of sexual differences in eruption
timing was present by age 10, however differences were not statistically significant.
Effective diagnosis and treatment planning for patients of Mexican heritage may require
assessment at an earlier age.

1
CHAPTER 1: INTRODUCTION
The human primary dentition is composed of 20 teeth, which erupt from the age
of 6 months up to 30 months. The permanent dentition comprises 32 teeth, which erupt
generally after 6 years of age. Teeth do not appear simultaneously in either dentition, and
in general, more variation is observed in the timing of eruption of the permanent teeth,
rather than the primary. [1]
The sequence of permanent tooth eruption in humans can be described in three
stages. The first stage is the eruption of the first permanent molars alongside the
substitution of primary incisors for permanent incisors. The second stage is the eruption
of the permanent cuspids and bicuspids in exchange for the primary cuspids and molars
and the eruption of the second molars. The third stage is the eruption of the third molars.

Fig 1. Primary teeth eruption chart [2]
2

Fig 2. Permanent teeth eruption chart [2]

Currently, throughout the orthodontic community, the accepted standard timings
of tooth eruption are described by Proffit [1]. However, studies have suggested that
Caucasians have a delayed time of eruption when compared to other ethnic groups
[3],[4]. A variety of factors influence the eruption of teeth and therefore standards for
eruption timing of permanent teeth are most useful when derived from the population to
which they will be applied.

3

Table 1. Chronology of tooth development, Permanent dentition. [1]

It is generally accepted that the development and maturation of Hispanic
adolescents occurs at a faster pace when compared to Caucasian adolescents. However,
dental eruption timing for the Hispanic population has not been widely studied and
eruption timing tables have not yet been described. It is important for the practitioner to
have a clear understanding of the average age of eruption of different populations for
diagnostic purposes and for the determination of correct treatment timing.
In California the most predominant minority is the Mexican ethnic group
comprising 32% of the population as of the year 2000[5] and it is a reasonable
assumption that a considerable percentage of patients in any given practice will belong to
this group. It is therefore relevant to attempt the description of guideline tables for the
eruption timing of permanent teeth in the Mexican population.
Permanent tooth eruption timing is extremely important in the planning of
orthodontic treatment. The prescription of orthodontic treatment as well as certain
sequencing decisions depend on the status of dental development in cases where
crowding, arch length discrepancies, impactions, and arch width (among others) exist.
4
Canines, premolars and second molars are usually the last permanent teeth to erupt into
the oral cavity, and as such discrepancies in eruption patterns are common.
In order to be able to manage discrepancies in eruption and its complications, the
clinician must have an accurate understanding of dental development and tooth eruption
sequence and timing.

5
CHAPTER 2: REVIEW OF THE LITERATURE

Many studies have been published on the topic of dental eruption patterns in
several areas such as clinical, epidemiological, anthropological and developmental
among others. Most of these reports describe a specific ethnic population, as many
variances to the accepted norms can be found. The timing of eruption of primary teeth is
variable; however, the eruption sequence is usually preserved and the entire primary
dentition is complete at 24 to 30 months. The transition from the primary to the
permanent dentition begins at age 6 and continues until 20 years of age with the eruption
of the third molars. For an orthodontist, it is essential to evaluate dental eruption in order
to determine treatment needs and appropriate treatment timing for each patient. As
mentioned previously, currently the standards of tooth eruption accepted in the United
States are those reported by Proffit.[1] The reported values were ascertained by Gron in
1962, who analyzed data gathered for 874 Caucasian children from the Boston area.[6]
In this study dental development was assessed by intraoral radiographs and emergence
timing was recorded at the time when teeth had pierced gingival but presented no more
than 3mm of clinical crown. Generally, girls were slightly ahead of boys in dental
development, but the author did not report any significant differences. Also, dental
eruption appeared to be more closely related to the stage of root formation than with the
chronologic or skeletal age of a child. Additional studies on eruption timing have been
published for different ethnic groups and the following is a review of the most recent
literature on the subject.

6
Physiological variables, ethnicity and dental age
Dental development has been linked to different physiological variables such as
skeletal maturity, body height and weight. It has also been established that dental
development correlates with chronologic age but occurs independently of it. In a study
by Anderson et al. [7] dental development related more strongly to morphological
development than to skeletal development in both sexes. Also, skeletal age and body size
related most strongly to late stages of tooth formation. It was also determined that in
males skeletal and dental mineralization were more closely related to height than weight;
the opposite is true for females. The authors found these relationships to be significant in
both pre-adolescent and adolescent years.
In another study by Wu et al, it was reported that Black and Mexican American
girls developed earlier and achieved menarche at an earlier age when compared with
Caucasian girls. The mean ages of onset of puberty for the three groups were 12.1, 12.2
and 12.7 years of age for Blacks, Mexican Americans and Caucasians respectively and
the ethnic differences remained after adjustment for body mass index and various
economic and social variables. The study concluded that Black girls enter puberty first
followed by Mexican American and Caucasian girls.[8] Chumlea et al. reported also
similar results; African American girls reach menarche earlier, followed by Mexican girls
and lastly, Caucasian girls. However overall, US girls were not found to be gaining
reproductive potential earlier than in the past. [9]
Several authors have attempted to describe the eruption times of permanent teeth
in children and adolescent. In a study published in 2004 in India, Agarwal et al. [10]
studied the permanent dentition in Indian boys of age 5-14 years old. The authors found
7
that the earliest teeth to erupt were the lower first molar followed by lower incisors. The
sequence for eruption that the authors described is the following (in orthodontic
notation): U6,1,2,4,3,5,7 and L6,1,2,3,4,5,7. Also, the eruption of teeth was significantly
positively related to height, weight and sexual maturity. A similar study by Eskeli, was
designed to study the differences in emergence timing and pattern of eruption of
permanent teeth in various parts of Finland.[11] The authors reported that all permanent
teeth, except the maxillary left second premolar, erupted earlier in girls than in boys and
some of the differences were statistically significant. Also, teeth in the incisor and canine
regions where more advanced in the mandible for both sexes. Some tooth groups erupted
earlier than the reported standards and other later and therefore no generalization could
be made regarding the timing of eruption of the total dentition. The authors did not find
any significant regional variations in terms of eruption timing.
Many other articles have been published that report ethnic and regional
characteristics of eruption of the permanent dentition. Blankenstein and others studied
the eruption of permanent incisors and first molars in South African black children and
found that the youngest age of eruption of any permanent tooth was 4.5 and 4.3 years old
for girls and boys respectively. They also reported that eruption ages were delayed
compared to most African studies, but similar to Kenyan and American blacks.[12] In a
similar study, De Melo and others reported that black subjects were more precocious in
dental development than were white subjects from the same Brazilian population.[13]
Rousset studied a sample of French children and found that all permanent
maxillary teeth varied by at least three months from the reported means. Also, compared
to earlier reports for other French populations, there appeared to be a secular trend for
8
later eruption of premolars and second molars. The authors attributed these changes to an
evolutionary reduction in the size of the maxilla, genetic changes and progress in dental
preventive measures to conserve the deciduous dentition.[14] Diamanti published a
similar article in 2003 for an Australian population and it was reported that mandibular
teeth preceeded maxillary teeth. Also, dental eruption was more advanced in girls than
boys, and in general, emergence times of children were delayed compared to the current
standards.[15]
In 2005 Wedl et al[16] described the sequence of eruption in Greek children and
adolescents. They found that the sequence of tooth eruption differed significantly when
comparing maxilla and mandible with a tendency towards earlier eruption in the lower
jaw and also that the upper second premolars erupt before the upper canines. Otherwise,
no major difference were observed when comparing with the establish norms for other
European populations.
Olze et al. published an interesting study on the effect of ethnicity on wisdom
tooth eruption from a forensic point of view.[17] Currently, wisdom tooth mineralization
has been the main criterion used for forensic dental age determination in adolescents. In
this study the authors compared the estimated age based on radiographic analyses and the
known date of birth of 2,482 patients of Caucasian, Asian and African ethnicities. The
authors concluded that African patients were more advanced in the mineralization stages
of wisdom teeth than were Caucasians. Caucasians were more advanced than were
Asians.
In an interesting study by Uysal et al, the authors evaluated dental panoramic
radiographs and hand-wrist radiographs of an extensive sample of orthodontic patients in
9
order to determine the relationships between the stages of calcification of various teeth
and skeletal maturity stages.[18] The authors reported that because of the high
correlation coefficients, tooth calcification stages from panoramic radiographs might be
clinically useful as a maturity indicator of the pubertal growth period. This study
demonstrates that even though sexual maturation indicators are typically used to estimate
remaining growth and dental stages, the opposite also applies. It is possible to estimate
pubertal stage by careful measurements of dental radiographs.
In many instances sexual maturity has been linked to dental development, with
one positively correlating to the other. In a study by So et al. the authors described a
correlation of stature and body weight and the eruption of permanent teeth with four
sexual maturity criteria (menarche, pubic hair, axillary hair and breast development).
With respect to all four selected criteria, girls who matured earlier were significantly
taller and heavier and had more erupted permanent teeth than girls who reached sexual
maturity later.[19] Filipsson on the other hand found a low correlation between the
dental maturity and the different measures of sexual development. [20] Demirjian and
others also found that there was no direct correlation between sexual and dental
development. The authors reported that the age at which French-Canadian girls attain
90% of their dental development showed no significant relationships with the sexual
maturity indicators evaluated.[21]
It is generally accepted among practitioners that earlier physical maturation is
observed in Hispanics when compared to Caucasians, a tendency that can also be seen
with the dental eruption timing. This occurrence has been described in the literature. In a
study by Sun et al [22] the authors reported a trend toward earlier maturation over a
10
period of 30 years in Caucasian boys and Mexican American boys and girls. There was
no evidence of a trend towards earlier maturation in African American boys and girls or
Caucasian girls with the passing of time. It has been reported in the literature that
Hispanics, and more specifically Mexicans, start sexual development earlier than do
Caucasians. Irwin discussed in an article in 2005 the evidence of sexual maturation
occuring earlier in Mexican females as well as males, when compared to Caucasians.[23]
It is therefore expected that Mexicans would present with a more advanced dental
development, and earlier dental eruption than their Caucasian counterparts of the same
age group.
Some investigators have associated the earlier onset of puberty with the increased
prevalence of obesity in the child population.[24, 25] Factors other than obesity,
however, i.e. genetic and/or environmental ones could also possibly play a role. Wang in
his article describes an opposite relationship in boys and in girls. In females, a higher
BMI correlates to earlier sexual maturation and in males the opposite is true; there is a
negative correlation between early high BMI and sexual maturity. The phenomenon of
earlier sexual maturity in the Hispanic population and its association to a higher BMI in
childhood has also been described.[23, 26]
It has been extensively reported that Mexican adolescents are generally more
overweight, and present a higher BMI, than do Caucasian adolescents.[27, 28] It is
reasonable to consider that this affects dental development and that it would be one factor
influencing earlier dental eruption is observed in the Mexican population. However, it is
important to mention that an extensive study conducted by Karpati et. al, using the US
National Health and Nutrition Examination Survey, indicated that there is no relationship
11
between a higher BMI and earlier sexual maturation.[29] One important factor to
consider is that most of the reported studies on increased BMI in Mexicans are based on
people living currently in the United States and do not take into account Mexico
residents, who might be exposed to different influencing factors.

Dental development and sexual dimorphism
Sexual dimorphism in the eruption of permanent teeth has been described in the
literature. In a longitudinal study, Holman and Jones examined the pattern of sexual
dimorphism in the emergence of deciduous teeth for four ethnically distinct
populations.[30] The authors found sexual differences for three of the populations and
described a crossover pattern in which males lead females in the anterior dentition and
females lead males in the posterior dentition. As for the ethnic differences in sexual
dimorphism, all four populations examined showed the same emergence sequence by sex.
The same pattern of sexual dimorphism was also described by Demirjian in 1980 for a
genetically homogeneous French-Canadian group of children.[31]
Nizam et al, in an article published in 2003, described the age and sequence of
eruption of permanent teeth in Malaysian patients. [32] The findings of this study were
as follows: the median age of eruption of each tooth was earlier in girls than in boys and
all mandibular teeth, with the exception of first and second bicuspids in both males and
females, tended to erupt earlier than their maxillary counterparts. An article published by
Leroy et al. in 2003 described the emergence of permanent teeth in Flemish children.[33]
They found that there are significantly earlier emergence ages in girls than in boys but
that the eruption pattern was symmetrical in both sexes. Mandibular teeth were found to
12
erupt earlier than maxillary counterparts. These findings are in accordance with other
studies using Caucasian samples. Hägg and Taranger previously mentioned this
crossover pattern in another study. They reported that boys were consistently ahead of
girls during most of the primary dentition emergence and that from the 17
th
deciduous
tooth on through the permanent dentition, girls are consistently ahead of boys.[34] In
another study designed to described the chronology of permanent tooth eruption in
Argentinean children it was found that all teeth emerged earlier in girls [35].
Moslemi [36], in 2004, defined the average time of eruption of permanent teeth,
the range of variation for each tooth and the sequence of eruption for boys and girls in
Iran. The findings of this study were that the average age of eruption of permanent teeth
in girls is less than in boys. Also, mandibular teeth have earlier eruption timing than
maxillary teeth in both boys and girls and lastly, that amongst girls maxillary canines
erupt earlier than maxillary second premolars. Similar results were published by
Hoffding et al, for a sample of Japanese children.[37]
Few studies have been published on dental eruption timing with population
samples from the United States. In one study, Savara and Steen examined a sample of
children from Oregon to determine the timing and sequence of eruption of the permanent
dentition.[38] The authors determined that girls showed more variability in age at
eruption than boys, and that eruption was generally earlier in girls. They also determined
that the most accepted sequence of eruption was observed in less than 15% of the cases.
Chronology and sequence of eruption has also been described for a complete
unilateral cleft lip and palate population with the finding that the females present a
tendency toward earlier mineralization and eruption of the permanent dentition.[39]
13
Anthropological considerations in dental development

Some authors recognize that in the absence of a birth certificate, the best way to
estimate the chronological age of a growing child is from his/her teeth. [40]
Folayan et al also described age estimation based on radiographic analysis as
important in aiding demographic surveys, in helping to age children in populations
without recorded birthdates, for reference standards, for clinical diagnosis of delayed or
advanced tooth eruption, and for comparison of life histories. [41] In this study, no
relationship was found between sex, socioeconomic status or breastfeeding status on the
timing or pattern of dental eruption in Nigerian children.
In another study by Gillet, the author described a standard of permanent tooth
emergence to be used in identifying Zambian children’s age when no birth record was
available.[42] The author gathered dental eruption timing data from children ages 4-14
whose birth date was documented and described eruption tables for that population,
which differed greatly from the published standards. The observed timing of eruption for
African children from this population was earlier than the previously described standards.

14
CHAPTER 3: RESEARCH QUESTIONS
Research Hypotheses:

1. A significant difference in the timing of secondary tooth (canines,
bicuspids, and second molars) eruption exists between Mexican adolescents and
Caucasian adolescents; that is, the permanent teeth of Mexican adolescents erupt
significantly (p < .05) earlier than in Caucasian adolescents.
2. Furthermore, sexual dimorphism exists in the Mexican sample; for any
age group, the eruption of the permanent dentition occurs earlier in female subjects.
3. There is a difference in eruption timing between the Mexican sample
and the reported standards.

Null Hypotheses:

1. No significant difference in the timing of secondary tooth eruption
exists between the Mexican adolescents and the Caucasian adolescents; that is, the
permanent teeth of Mexican adolescents erupt at relatively similar times than a sample of
Caucasian adolescents.
2. Furthermore, no sexual dimorphism exists; there is no significant
difference in timing of secondary tooth eruption between the males and females within
the Mexican sample.
3. There is no difference in eruption timing between the Mexican sample and the
reported standards of dental eruption.
15
CHAPTER 4: MATERIALS AND METHODS

To evaluate secondary tooth eruption in Mexican adolescents, 247 records were
evaluated from a Mexican dental school, Universidad Autónoma Nacional de Mexico
(UNAM). Subjects were age-matched to the comparison study [43].
Selection criteria:

1. Ethnicity: Mexican ethnicity. All patients at UNAM are of Mexican
ethnicity.
2. Age: Patient must have been between the ages of 8 and 12 years of age at
the time of records.
a. Age 8,9
i. Females n=15
ii. Males n= 8
b. Age 10
i. Females n=27
ii. Males n=23
c. Age 11
i. Females n=71
ii. Males n=66
d. Age 12
i. Females n=23
ii. Males n=24
16
3. Complete medical history: Patient must have had a current and complete
medical history at the time of records.
4. Sufficient records: Any dated record with a clear indication of the total
number of teeth clinically present in the mouth was deemed reliable and used. Such
records consisted of any combination of the following:
a. Paper chart
b. Photographs
c. Study models
5. Radiographic evidence of the existence of all secondary dentition: For
those subjects with unerupted permanent dentition, radiographic records providing
evidence of its existence were required.

Exclusion criteria:

Those records not meeting the previously identified selection criteria or having
any one of the following characteristics were excluded from the study:

1. Inadequate records
2. Records in which there was contradicting evidence of erupted dentition.
3. Any record in which the patient indicated on their medical history a
positive for any condition, which may influence eruption of the secondary dentition.
17
4. Any record with incomplete secondary dentition. Exception: If patient
had had previous extraction/loss of secondary teeth; i.e., lower first molars extracted due
to decay. In these situations, it was assumed that the teeth were extracted.
5. Any record in which the date was not recorded or a contradiction in dates
was apparent.

Once a record was proven to meet all of above criteria, the following information
was recorded into an Excel spreadsheet using a personal laptop computer:
1. Ethnicity: Mexican
2. Gender: Male or Female (M/F)
3. Age at the time of record in year and month (Yr-Mo)
4. Medical history: The patient’s medical history was screened for any
conditions, which have been linked to eruption disturbances. Any medical condition
disqualified the chart for the purpose of this study.
5. Number of teeth presents (n/28): Ignoring upper and lower third molars,
the total number of permanent teeth clinically present at the time of record. A tooth was
considered erupted if any portion of the crown had emerged through the gingiva and was
clinically visible at the time of record.
6. Teeth unerupted (permanent cuspids, bicuspids, and second molars):
Ignoring third molars, those teeth listed above (all patients were assumed to have all
incisors and first molars present) not clinically present at the time of record were listed
using Palmer notation in the following order:
a. Upper right quadrant
18
b. Upper left quadrant
c. Lower right quadrant
d. Lower left quadrant

2. Source of eruption data: Three types of records were used (radiographs,
models, photos) to determine the emergence of permanent teeth.
3. Radiographic check: To confirm the existence of the teeth being studied if
they were unerupted.
Table 2: Sample data collection sheet

Using SPSS® software, Pearson chi square tests were performed to determine any
significant differences between the eruption times of the specific tooth groups and the
ethnic groups. The significance limit was set at P<0.05. Cross-tabulations were also
calculated for each tooth group and ethnic group.
ID# Eth(M/C) Gen(M/F) Age Mdhx #tth(n/28) unerupted record Xray
1
2
3
4
5
6
7
8
9
10
11
12
13
14
19
CHAPTER 5: RESULTS

Emergence of specific secondary teeth (cuspids, bicuspids, and second molars)
was compared between Mexican patients from one location in Mexico City and the data
for Caucasian patients obtained from a previous study involving three locations in the
Los Angeles area. The following statistical analyses (Pearson chi square tests) were
performed to determine any significant differences (P < .05) between the eruption times
of these specific teeth between the ethnic groups.

Females age 8,9 (n=28)

Fig 3. Distribution graph: Females age 8,9

Upper Canines (u3s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 28 100.0% 0 .0% 28 100.0%
Table 3: Case Processing Summary- Upper canines; Females age 8,9
20

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.867
a
1 .172

Continuity
Correction
b

.398 1 .528

Likelihood Ratio 2.630 1 .105

Fisher's Exact Test

.484 .278
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .93.
b. Computed only for a 2x2 table

Table 4: Chi-Square Test- Upper canines, Females age 8,9

ethnic * u3s Crosstabulation

u3s

no yes Total
Count 13 0 13
% within ethnic 100.0% .0% 100.0%
% within u3s 50.0% .0% 46.4%
C
% of Total 46.4% .0% 46.4%
Count 13 2 15
% within ethnic 86.7% 13.3% 100.0%
% within u3s 50.0% 100.0% 53.6%
MEX
% of Total 46.4% 7.1% 53.6%
Count 26 2 28
% within ethnic 92.9% 7.1% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 92.9% 7.1% 100.0%
Table 5: Crosstabulation- Upper canines; Females age 8,9
21

Fig 4. Females age 8,9: Upper canines

In the Mexican sample, 2 of 15 patients (13.3%) had erupted upper canines. In
the Caucasian sample, 0 of 13 (0%) had erupted upper canines. A P value = 0.172
indicates no significant difference in upper canine eruption between female Mexican and
Caucasian patients of ages 8 and 9.

Lower Canines (l3s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 28 100.0% 0 .0% 28 100.0%
Table 6: Case Processing Summary- Lower canines; Females age 8,9
22
ethnic * l3s Crosstabulation

l3s

no yes Total
Count 7 6 13
% within ethnic 53.8% 46.2% 100.0%
% within l3s 46.7% 46.2% 46.4%
C
% of Total 25.0% 21.4% 46.4%
Count 8 7 15
% within ethnic 53.3% 46.7% 100.0%
% within l3s 53.3% 53.8% 53.6%
MEX
% of Total 28.6% 25.0% 53.6%
Count 15 13 28
% within ethnic 53.6% 46.4% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 53.6% 46.4% 100.0%
Table 7: Crosstabulation- Lower canines; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig. (2-
sided)
Exact Sig. (1-
sided)
Pearson Chi-Square .001
a
1 .978

Continuity Correction
b
.000 1 1.000

Likelihood Ratio .001 1 .978

Fisher's Exact Test

1.000 .638
N of Valid Cases 28

a. 0 cells (.0%) have expected count less than 5. The minimum expected count is 6.04.
b. Computed only for a 2x2 table

Table 8: Chi-Square Test- Lower canines, Females age 8,9

23

Fig 5. Females age 8,9: Lower canines

In the Mexican sample, 7 of 15 patients (46.7%) had erupted lower canines. In
the Caucasian sample, 6 of 13 (46.2%) had erupted lower canines. A P value = 0.978
indicates no significant difference in lower canine eruption between female Mexican and
Caucasian patients of ages 8 and 9.
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
28 100.0% 0 .0% 28 100.0%
Table 9: Case Processing Summary- Upper premolars; Females age 8,9

24
ethnic * u45s Crosstabulation

u45s

no yes Total
Count 12 1 13
% within ethnic 92.3% 7.7% 100.0%
% within u45s 54.5% 16.7% 46.4%
C
% of Total 42.9% 3.6% 46.4%
Count 10 5 15
% within ethnic 66.7% 33.3% 100.0%
% within u45s 45.5% 83.3% 53.6%
MEX
% of Total 35.7% 17.9% 53.6%
Count 22 6 28
% within ethnic 78.6% 21.4% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 78.6% 21.4% 100.0%
Table 10: Crosstabulation- Upper premolars; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.720
a
1 .099

Continuity
Correction
b

1.410 1 .235

Likelihood Ratio 2.950 1 .086

Fisher's Exact Test

.173 .117
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 2.79.
b. Computed only for a 2x2 table

Table 11: Chi-Square Test- Upper premolars, Females age 8,9
25

Fig 6. Females age 8,9: Upper bicuspids

In the Mexican sample, 5 of 15 patients (33.3%) had erupted upper bicuspids. In
the Caucasian sample, 1 of 13 (7.7%) had erupted upper bicuspids. A P value = 0.099
indicates no significant difference in upper bicuspid eruption between female Mexican
and Caucasian patients of ages 8 and 9.

Lower Bicuspids (l45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 28 100.0% 0 .0% 28 100.0%
Table 12: Case Processing Summary- Lower premolars; Females age 8,9
26

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 13 0 13
% within ethnic 100.0% .0% 100.0%
% within l45s 54.2% .0% 46.4%
C
% of Total 46.4% .0% 46.4%
Count 11 4 15
% within ethnic 73.3% 26.7% 100.0%
% within l45s 45.8% 100.0% 53.6%
MEX
% of Total 39.3% 14.3% 53.6%
Count 24 4 28
% within ethnic 85.7% 14.3% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 85.7% 14.3% 100.0%
Table 13: Crosstabulation- Lower premolars; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
4.044
a
1 .044

Continuity
Correction
b

2.160 1 .142

Likelihood Ratio 5.569 1 .018

Fisher's Exact Test

.102 .067
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 1.86.
b. Computed only for a 2x2 table

Table 14: Chi-Square Test- Lower premolars, Females age 8,9
27

Fig 7. Females age 8,9: Lower bicuspids

In the Mexican sample, 4 of 15 patients (26.7%) had erupted lower bicuspids. In
the Caucasian sample, 0 of 13 (0%) had erupted lower bicuspids. A P value = 0.044
indicates that a significant difference exists in lower bicuspid eruption between female
Mexican and Caucasian patients of ages 8 and 9.
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
28 100.0% 0 .0% 28 100.0%
Table 15: Case Processing Summary- All premolars; Females age 8,9

28

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 13 0 13
% within ethnic 100.0% .0% 100.0%
% within ul45s 54.2% .0% 46.4%
C
% of Total 46.4% .0% 46.4%
Count 11 4 15
% within ethnic 73.3% 26.7% 100.0%
% within ul45s 45.8% 100.0% 53.6%
MEX
% of Total 39.3% 14.3% 53.6%
Count 24 4 28
% within ethnic 85.7% 14.3% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 85.7% 14.3% 100.0%
Table 16: Crosstabulation- All premolars; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
4.044
a
1 .044

Continuity
Correction
b

2.160 1 .142

Likelihood Ratio 5.569 1 .018

Fisher's Exact Test

.102 .067
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 1.86.
b. Computed only for a 2x2 table

Table 17: Chi-Square Test- All premolars, Females age 8,9
29

Fig 8. Females age 8,9: At least one upper and one lower bicuspids

In the Mexican sample, 4 of 15 patients (26.7%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 0 of 13 (0%) had erupted upper and
lower bicuspids. A P value = 0.044 indicates that a significant difference exists in upper
and lower bicuspid eruption between female Mexican and Caucasian patients of ages 8
and 9.
Upper Second Molars (u7s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 28 100.0% 0 .0% 28 100.0%
Table 18: Case Processing Summary- Upper second molars; Females age 8,9
30

ethnic * u7s Crosstabulation

u7s

no yes Total
Count 13 0 13
% within ethnic 100.0% .0% 100.0%
% within u7s 48.1% .0% 46.4%
C
% of Total 46.4% .0% 46.4%
Count 14 1 15
% within ethnic 93.3% 6.7% 100.0%
% within u7s 51.9% 100.0% 53.6%
MEX
% of Total 50.0% 3.6% 53.6%
Count 27 1 28
% within ethnic 96.4% 3.6% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 96.4% 3.6% 100.0%
Table 19: Crosstabulation- Upper second molars; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.899
a
1 .343

Continuity
Correction
b

.000 1 1.000

Likelihood Ratio 1.280 1 .258

Fisher's Exact Test

1.000 .536
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .46.
b. Computed only for a 2x2 table

Table 20: Chi-Square Test- Upper second molars, Females age 8,9
31

Fig 9. Females age 8,9: Upper second molars

In the Mexican sample, 1 of 15 patients (6.7%) had erupted upper second molars.
In the Caucasian sample, 0 of 13 (0%) had erupted upper second molars. A P value =
0.343 indicates that no significant difference exists in upper second molar eruption
between female Mexican and Caucasian patients of ages 8 and 9. The same values were
evident for lower second molars.
Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 28 100.0% 0 .0% 28 100.0%
Table 21: Case Processing Summary- Lower second molars; Females age 8,9
32

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 13 0 13
% within ethnic 100.0% .0% 100.0%
% within l7s 48.1% .0% 46.4%
C
% of Total 46.4% .0% 46.4%
Count 14 1 15
% within ethnic 93.3% 6.7% 100.0%
% within l7s 51.9% 100.0% 53.6%
MEX
% of Total 50.0% 3.6% 53.6%
Count 27 1 28
% within ethnic 96.4% 3.6% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 96.4% 3.6% 100.0%
Table 22: Crosstabulation- Lower second molars; Females age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.899
a
1 .343

Continuity
Correction
b

.000 1 1.000

Likelihood Ratio 1.280 1 .258

Fisher's Exact Test

1.000 .536
N of Valid Cases 28

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .46.
b. Computed only for a 2x2 table

Table 23: Chi-Square Test- Lower second molars, Females age 8,9
33

Fig 10. Females age 8,9: Lower second molars

In the Mexican sample, 1 of 15 patients (6.7%) had erupted lower second molars.
In the Caucasian sample, 0 of 13 (0%) had erupted lower second molars. A P value =
0.343 indicates that no significant difference exists in lower second molar eruption
between female Mexican and Caucasian patients of ages 8 and 9.

34
Males age 8,9 (n=15)

Fig 11. Distribution graph: Males age 8,9

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 15 100.0% 0 .0% 15 100.0%
Table 24: Case Processing Summary- Upper canines; Males age 8,9

35

ethnic * u3s Crosstabulation

u3s

no Total
Count 7 7
% within ethnic 100.0% 100.0%
% within u3s 46.7% 46.7%
C
% of Total 46.7% 46.7%
Count 8 8
% within ethnic 100.0% 100.0%
% within u3s 53.3% 53.3%
MEX
% of Total 53.3% 53.3%
Count 15 15
% within ethnic 100.0% 100.0%
% within u3s 100.0% 100.0%
ethnic
Total
% of Total 100.0% 100.0%
Table 25: Crosstabulation- Upper canines; Males age 8,9

Chi-Square Tests

Value
Pearson Chi-
Square
.
a

N of Valid Cases 15
a. No statistics are
computed because u3s is a
constant.
Table 26: Chi-Square Test- Upper canines, Males age 8,9
36

Fig 12. Males age 8,9: Upper canines

In the Mexican sample, 0 of 8 (0%) had erupted upper canines. In the Caucasian
sample, 0 of 7 (0%) had erupted upper canines. No P value was obtained, as upper
cuspids were not erupted for either ethnic group. The same results were evident for the
lower cuspids.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 15 100.0% 0 .0% 15 100.0%
Table 27: Case Processing Summary- Lower canines; Males age 8,9
37

ethnic * l3s Crosstabulation

l3s

no Total
Count
7 7
% within ethnic 100.0% 100.0%
% within l3s 46.7% 46.7%
C
% of Total 46.7% 46.7%
Count 8 8
% within ethnic 100.0% 100.0%
% within l3s 53.3% 53.3%
MEX
% of Total 53.3% 53.3%
Count 15 15
% within ethnic 100.0% 100.0%
% within l3s 100.0% 100.0%
ethnic
Total
% of Total 100.0% 100.0%
Table 28: Crosstabulation- Lower canines; Males age 8,9

Chi-Square Tests

Value
Pearson Chi-
Square
.
a

N of Valid Cases 15
a. No statistics are
computed because l3s is a
constant.
Table 29: Chi-Square Test- Lower canines, Males age 8,9
38

Fig 13. Males age 8,9: Lower canines

In the Mexican sample, 0 of 8 (0%) had erupted lower canines. In the Caucasian
sample, 0 of 7 (0%) had erupted lower canines. No P value was obtained, as lower
cuspids were not erupted for either ethnic group.

Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
15 100.0% 0 .0% 15 100.0%
Table 30: Case Processing Summary- Upper premolars; Males age 8,9
39

ethnic * u45s Crosstabulation

u45s

no yes Total
Count 7 0 7
% within ethnic 100.0% .0% 100.0%
% within u45s 53.8% .0% 46.7%
C
% of Total 46.7% .0% 46.7%
Count 6 2 8
% within ethnic 75.0% 25.0% 100.0%
% within u45s 46.2% 100.0% 53.3%
MEX
% of Total 40.0% 13.3% 53.3%
Count 13 2 15
% within ethnic 86.7% 13.3% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 86.7% 13.3% 100.0%
Table 31: Crosstabulation- Upper premolars; Males age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.019
a
1 .155

Continuity
Correction
b

.435 1 .509

Likelihood Ratio 2.783 1 .095

Fisher's Exact Test

.467 .267
N of Valid Cases 15

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .93.
b. Computed only for a 2x2 table

Table 32: Chi-Square Test- Upper premolars, Males age 8,9
40

Fig 14. Males age 8,9: Upper bicuspids

In the Mexican sample, 2 of 8 patients (25.0%) had erupted upper bicuspids. In
the Caucasian sample, 0 of 7 (0%) had erupted upper bicuspids. A P value = 0.155
indicates no significant difference in upper bicuspid eruption between male Mexican and
Caucasian patients of ages 8 and 9.

Lower Bicuspids (l45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 15 100.0% 0 .0% 15 100.0%
Table 33: Case Processing Summary- Lower premolars; Males age 8,9
41

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 7 0 7
% within ethnic 100.0% .0% 100.0%
% within l45s 50.0% .0% 46.7%
C
% of Total 46.7% .0% 46.7%
Count 7 1 8
% within ethnic 87.5% 12.5% 100.0%
% within l45s 50.0% 100.0% 53.3%
MEX
% of Total 46.7% 6.7% 53.3%
Count 14 1 15
% within ethnic 93.3% 6.7% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 93.3% 6.7% 100.0%
Table 34: Crosstabulation- Lower premolars; Males age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.938
a
1 .333

Continuity
Correction
b

.000 1 1.000

Likelihood Ratio 1.320 1 .251

Fisher's Exact Test

1.000 .533
N of Valid Cases 15

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .47.
b. Computed only for a 2x2 table

Table 35: Chi-Square Test- Lower premolars, Males age 8,9
42

Fig 15. Males age 8,9: Lower bicuspids

In the Mexican sample, 1 of 8 patients (12.5%) had erupted lower bicuspids. In
the Caucasian sample, 0 of 7 (0%) had erupted lower bicuspids. A P value = 0.333
indicates no significant difference in lower bicuspid eruption between male Mexican and
Caucasian patients of ages 8 and 9.

43

All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
15 100.0% 0 .0% 15 100.0%
Table 36: Case Processing Summary- All premolars; Males age 8,9

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 7 0 7
% within ethnic 100.0% .0% 100.0%
% within ul45s 50.0% .0% 46.7%
C
% of Total 46.7% .0% 46.7%
Count 7 1 8
% within ethnic 87.5% 12.5% 100.0%
% within ul45s 50.0% 100.0% 53.3%
MEX
% of Total 46.7% 6.7% 53.3%
Count 14 1 15
% within ethnic 93.3% 6.7% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 93.3% 6.7% 100.0%
Table 37: Crosstabulation- All premolars; Males age 8,9

44

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.938
a
1 .333

Continuity
Correction
b

.000 1 1.000

Likelihood Ratio 1.320 1 .251

Fisher's Exact Test

1.000 .533
N of Valid Cases 15

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is .47.
b. Computed only for a 2x2 table

Table 38: Chi-Square Test- All premolars, Males age 8,9

Fig 16. Males age 8,9: At least one upper and one lower bicuspids
45
In the Mexican sample, 1 of 8 patients (12.5%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 0 of 7 (0%) had erupted upper and
lower bicuspids. A P value = 0.333 indicates no significant difference in total bicuspid
eruption between male Mexican and Caucasian patients of ages 8 and 9.
Upper Second Molars (u7s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 15 100.0% 0 .0% 15 100.0%
Table 39: Case Processing Summary- Upper second molars; Males age 8,9

ethnic * u7s Crosstabulation

u7s

no Total
Count 7 7
% within ethnic 100.0% 100.0%
% within u7s 46.7% 46.7%
C
% of Total 46.7% 46.7%
Count 8 8
% within ethnic 100.0% 100.0%
% within u7s 53.3% 53.3%
MEX
% of Total 53.3% 53.3%
Count 15 15
% within ethnic 100.0% 100.0%
% within u7s 100.0% 100.0%
ethnic
Total
% of Total 100.0% 100.0%
Table 40: Crosstabulation- Upper second molars; Males age 8,9

46
Chi-Square Tests

Value
Pearson Chi-
Square
.
a

N of Valid Cases 15
a. No statistics are
computed because u7s is a
constant.
Table 41: Chi-Square Test- Upper second molars, Males age 8,9

Fig 17. Males age 8,9: Upper second molars

In the Mexican sample, 0 of 8 (0%) had erupted upper second molars. In the
Caucasian sample, 0 of 7 (0%) had erupted upper second molars. No P value was
obtained, as upper molars were not erupted for either ethnic group. The same results
were evident for the lower second molars.
47
Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 15 100.0% 0 .0% 15 100.0%
Table 42: Case Processing Summary- Lower second molars; Males age 8,9

ethnic * l7s Crosstabulation

l7s

no Total
Count 7 7
% within ethnic 100.0% 100.0%
% within l7s 46.7% 46.7%
C
% of Total 46.7% 46.7%
Count 8 8
% within ethnic 100.0% 100.0%
% within l7s 53.3% 53.3%
MEX
% of Total 53.3% 53.3%
Count 15 15
% within ethnic 100.0% 100.0%
% within l7s 100.0% 100.0%
ethnic
Total
% of Total 100.0% 100.0%
Table 43: Crosstabulation- Lower second molars; Males age 8,9

48
Chi-Square Tests

Value
Pearson Chi-
Square
.
a

N of Valid Cases 15
a. No statistics are
computed because l7s is a
constant.
Table 44: Chi-Square Test- Lower second molars, Males age 8,9

Fig 18. Males age 8,9: Lower second molars

In the Mexican sample, 0 of 8 (0%) had erupted lower second molars. In the
Caucasian sample, 0 of 7 (0%) had erupted lower second molars. No P value was
obtained, as lower second molars were not erupted for either ethnic group.
49

Sexual comparison for Mexican patients age 8,9

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Pearson Chi-
Square
4.947
a
6 .551
Likelihood Ratio 6.780 6 .342
N of Valid Cases 23

a. 13 cells (92.9%) have expected count less than
5. The minimum expected count is .35.
Table 45: Chi-Square Test- All erupted teeth; Females and Males age 8,9

Fig 19. Differences in dental eruption for Mexican patients age 8,9

50

There is no significant difference in eruption timing between male and female
Mexican patients age 8,9. However, females presented with more erupted teeth than did
the males.

Females age 10 (n=54)

Fig 20. Distribution graph: Females age 10

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 54 100.0% 0 .0% 54 100.0%
Table 46: Case Processing Summary- Upper canines; Females age 10

51

ethnic * u3s Crosstabulation

u3s

no yes Total
Count 20 7 27
% within ethnic 74.1% 25.9% 100.0%
% within u3s 66.7% 29.2% 50.0%
C
% of Total 37.0% 13.0% 50.0%
Count 10 17 27
% within ethnic 37.0% 63.0% 100.0%
% within u3s 33.3% 70.8% 50.0%
MEX
% of Total 18.5% 31.5% 50.0%
Count 30 24 54
% within ethnic 55.6% 44.4% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 55.6% 44.4% 100.0%
Table 47: Crosstabulation- Upper canines; Females age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
7.500
a
1 .006

Continuity
Correction
b

6.075 1 .014

Likelihood Ratio 7.694 1 .006

Fisher's Exact Test

.013 .006
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 12.00.
b. Computed only for a 2x2 table

Table 48: Chi-Square Test- Upper canines, Females age 10
52

Fig 21. Females age 10: Upper canines

In the Mexican sample, 17 of 27 patients (63.0%) had erupted upper canines. In
the Caucasian sample, 7 of 27 (25.9%) had erupted upper canines. A P value = 0.006
indicates a significant difference in upper canine eruption between female Mexican and
Caucasian patients of age 10. 70.8% of all eruptions were found in the Mexican
population.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 54 100.0% 0 .0% 54 100.0%
Table 49: Case Processing Summary- Lower canines; Females age 10
53
ethnic * l3s Crosstabulation

l3s

no yes Total
Count 11 16 27
% within ethnic 40.7% 59.3% 100.0%
% within l3s 78.6% 40.0% 50.0%
C
% of Total 20.4% 29.6% 50.0%
Count 3 24 27
% within ethnic 11.1% 88.9% 100.0%
% within l3s 21.4% 60.0% 50.0%
MEX
% of Total 5.6% 44.4% 50.0%
Count 14 40 54
% within ethnic 25.9% 74.1% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 25.9% 74.1% 100.0%
Table 50: Crosstabulation- Lower canines; Females age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
6.171
a
1 .013

Continuity
Correction
b

4.725 1 .030

Likelihood Ratio 6.471 1 .011

Fisher's Exact Test

.028 .014
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 7.00.
b. Computed only for a 2x2 table

Table 51: Chi-Square Test- Lower canines, Females age 10
54

Fig 22. Females age 10: Lower canines

In the Mexican sample, 24 of 27 patients (88.9%) had erupted lower canines. In
the Caucasian sample, 16 of 27 (59.3%) had erupted lower canines. A P value = 0.013
indicates a significant difference in lower canine eruption between female Mexican and
Caucasian patients of age 10. 60.0% of all eruptions were found in the Mexican
population.

55
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
54 100.0% 0 .0% 54 100.0%
Table 52: Case Processing Summary- Upper premolars; Females age 10

ethnic * u45s Crosstabulation

u45s

no yes Total
Count 24 3 27
% within ethnic 88.9% 11.1% 100.0%
% within u45s 82.8% 12.0% 50.0%
C
% of Total 44.4% 5.6% 50.0%
Count 5 22 27
% within ethnic 18.5% 81.5% 100.0%
% within u45s 17.2% 88.0% 50.0%
MEX
% of Total 9.3% 40.7% 50.0%
Count 29 25 54
% within ethnic 53.7% 46.3% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 53.7% 46.3% 100.0%
Table 53: Crosstabulation- Upper premolars; Females age 10

56

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.689E1 1 .000

Continuity
Correction
b

24.132 1 .000

Likelihood Ratio 29.851 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 12.50.
b. Computed only for a 2x2 table

Table 54: Chi-Square Test- Upper premolars, Females age 10

Fig 23. Females age 10: Upper bicuspids

57
In the Mexican sample, 22 of 27 patients (81.5%) had erupted upper bicuspids. In
the Caucasian sample, 3 of 27 (11.1%) had erupted upper bicuspids. A P value = 0.000
indicates a significant difference in upper bicuspid eruption between female Mexican and
Caucasian patients of age 10. 88.0% of all eruptions were found in the Mexican patient
population.
Lower Bicuspids (l45s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 54 100.0% 0 .0% 54 100.0%
Table 55: Case Processing Summary- Lower premolars; Females age 10

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 22 5 27
% within ethnic 81.5% 18.5% 100.0%
% within l45s 78.6% 19.2% 50.0%
C
% of Total 40.7% 9.3% 50.0%
Count 6 21 27
% within ethnic 22.2% 77.8% 100.0%
% within l45s 21.4% 80.8% 50.0%
MEX
% of Total 11.1% 38.9% 50.0%
Count 28 26 54
% within ethnic 51.9% 48.1% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 51.9% 48.1% 100.0%
Table 56: Crosstabulation- Lower premolars; Females age 10
58

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.899E1 1 .000

Continuity
Correction
b

16.690 1 .000

Likelihood Ratio 20.307 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 13.00.
b. Computed only for a 2x2 table

Table 57: Chi-Square Test- Lower premolars, Females age 10

Fig 24: Females age 10: Lower bicuspids

59
In the Mexican sample, 21 of 27 patients (77.8%) had erupted lower bicuspids. In
the Caucasian sample, 5 of 27 (18.5%) had erupted lower bicuspids. A P value = 0.000
indicates a significant difference in lower bicuspid eruption between female Mexican and
Caucasian patients of age 10. 80.8% of all eruptions were found in the Mexican patient
population.

All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
54 100.0% 0 .0% 54 100.0%
Table 58: Case Processing Summary- All premolars; Females age 10

60
ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 24 3 27
% within ethnic 88.9% 11.1% 100.0%
% within ul45s 80.0% 12.5% 50.0%
C
% of Total 44.4% 5.6% 50.0%
Count 6 21 27
% within ethnic 22.2% 77.8% 100.0%
% within ul45s 20.0% 87.5% 50.0%
MEX
% of Total 11.1% 38.9% 50.0%
Count 30 24 54
% within ethnic 55.6% 44.4% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 55.6% 44.4% 100.0%
Table 59: Crosstabulation- All premolars; Females age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.430E1 1 .000

Continuity
Correction
b

21.675 1 .000

Likelihood Ratio 26.751 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 12.00.
b. Computed only for a 2x2 table

Table 60: Chi-Square Test- All premolars, Females age 10
61

Fig 25. Females age 10: At least one upper and one lower bicuspids

In the Mexican sample, 21 of 27 patients (77.8%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 3 of 27 (11.1%) had erupted upper and
lower bicuspids. A P value = 0.000 indicates that a significant difference exists in total
bicuspid eruption between female Mexican and Caucasian patients of age 10.

Upper Second Molars (u7s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 54 100.0% 0 .0% 54 100.0%
Table 61: Case Processing Summary- Upper premolars; Females age 10

62
ethnic * u7s Crosstabulation

u7s

no yes Total
Count 27 0 27
% within ethnic 100.0% .0% 100.0%
% within u7s 57.4% .0% 50.0%
C
% of Total 50.0% .0% 50.0%
Count 20 7 27
% within ethnic 74.1% 25.9% 100.0%
% within u7s 42.6% 100.0% 50.0%
MEX
% of Total 37.0% 13.0% 50.0%
Count 47 7 54
% within ethnic 87.0% 13.0% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 87.0% 13.0% 100.0%
Table 62: Crosstabulation- Upper second molars; Females age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
8.043
a
1 .005

Continuity
Correction
b

5.909 1 .015

Likelihood Ratio 10.751 1 .001

Fisher's Exact Test

.010 .005
N of Valid Cases 54

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 3.50.
b. Computed only for a 2x2 table

Table 63: Chi-Square Test- Upper second molars, Females age 10
63

Fig 26. Females age 10: Upper second molars

In the Mexican sample, 7 of 27 (25.9%) had erupted upper second molars. In the
Caucasian sample, 0 of 27 (0%) had erupted upper second molars. . A P value = 0.005
indicates that a significant difference exists in upper second molar eruption between
female Mexican and Caucasian patients of age 10.

Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 54 100.0% 0 .0% 54 100.0%
Table 64: Case Processing Summary- Lower second molars; Females age 10
64

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 24 3 27
% within ethnic 88.9% 11.1% 100.0%
% within l7s 60.0% 21.4% 50.0%
C
% of Total 44.4% 5.6% 50.0%
Count 16 11 27
% within ethnic 59.3% 40.7% 100.0%
% within l7s 40.0% 78.6% 50.0%
MEX
% of Total 29.6% 20.4% 50.0%
Count 40 14 54
% within ethnic 74.1% 25.9% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 74.1% 25.9% 100.0%
Table 65: Crosstabulation- Lower second molars; Females age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
6.171
a
1 .013

Continuity
Correction
b

4.725 1 .030

Likelihood Ratio 6.471 1 .011

Fisher's Exact Test

.028 .014
N of Valid Cases 54

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 7.00.
b. Computed only for a 2x2 table

Table 66: Chi-Square Test- Lower second molars, Females age 10
65

Fig 27. Females age 10: Lower second molars

In the Mexican sample, 11 of 27 (40.7%) had erupted lower second molars. In the
Caucasian sample, 3 of 27 (11.1%) had erupted upper second molars. A P value = 0.013
indicates that a significant difference exists in lower second molar eruption between
female Mexican and Caucasian patients of age 10.

66
Males age 10 (n=46)

Fig 28. Distribution graph: Males age 10

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 46 100.0% 0 .0% 46 100.0%
Table 67: Case Processing Summary- Upper canines; Males age 10

67
ethnic * u3s Crosstabulation

u3s

no yes Total
Count 16 7 23
% within ethnic 69.6% 30.4% 100.0%
% within u3s 51.6% 46.7% 50.0%
C
% of Total 34.8% 15.2% 50.0%
Count 15 8 23
% within ethnic 65.2% 34.8% 100.0%
% within u3s 48.4% 53.3% 50.0%
MEX
% of Total 32.6% 17.4% 50.0%
Count 31 15 46
% within ethnic 67.4% 32.6% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 67.4% 32.6% 100.0%
Table 68: Crosstabulation- Upper canines; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.099
a
1 .753

Continuity
Correction
b

.000 1 1.000

Likelihood Ratio .099 1 .753

Fisher's Exact Test

1.000 .500
N of Valid Cases 46

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 7.50.
b. Computed only for a 2x2 table

Table 69: Chi-Square Test- Upper canines, Males age 10
68

Fig 29. Males age 10 :Upper canines

In the Mexican sample, 8 of 23 patients (34.8%) had erupted upper canines. In
the Caucasian sample, 7 of 23 (30.4%) had erupted upper canines. A P value = 0.753
indicates no significant difference in upper canine eruption between male Mexican and
Caucasian patients of age 10.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 46 100.0% 0 .0% 46 100.0%
Table 70: Case Processing Summary- Lower canines; Males age 10
69

ethnic * l3s Crosstabulation

l3s

no yes Total
Count 12 11 23
% within ethnic 52.2% 47.8% 100.0%
% within l3s 57.1% 44.0% 50.0%
C
% of Total 26.1% 23.9% 50.0%
Count 9 14 23
% within ethnic 39.1% 60.9% 100.0%
% within l3s 42.9% 56.0% 50.0%
MEX
% of Total 19.6% 30.4% 50.0%
Count 21 25 46
% within ethnic 45.7% 54.3% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 45.7% 54.3% 100.0%
Table 71: Crosstabulation- Lower canines; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.789
a
1 .375

Continuity
Correction
b

.350 1 .554

Likelihood Ratio .791 1 .374

Fisher's Exact Test

.554 .277
N of Valid Cases 46

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 10.50.
b. Computed only for a 2x2 table

Table 72: Chi-Square Test- Lower canines, Males age 10
70

Fig 30. Males age 10: Lower canines

In the Mexican sample, 14 of 23 patients (60.9%) had erupted lower canines. In
the Caucasian sample, 11 of 23 (47.8%) had erupted lower canines. A P value = 0.375
indicate no significant difference in lower canine eruption between male Mexican and
Caucasian patients of age 10.
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
46 100.0% 0 .0% 46 100.0%
Table 73: Case Processing Summary- Upper premolars; Males age 10

71
ethnic * u45s Crosstabulation

u45s

no yes Total
Count 17 6 23
% within ethnic 73.9% 26.1% 100.0%
% within u45s 73.9% 26.1% 50.0%
C
% of Total 37.0% 13.0% 50.0%
Count 6 17 23
% within ethnic 26.1% 73.9% 100.0%
% within u45s 26.1% 73.9% 50.0%
MEX
% of Total 13.0% 37.0% 50.0%
Count 23 23 46
% within ethnic 50.0% 50.0% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 50.0% 50.0% 100.0%
Table 74: Crosstabulation- Upper premolars; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.052E1 1 .001

Continuity
Correction
b

8.696 1 .003

Likelihood Ratio 10.965 1 .001

Fisher's Exact Test

.003 .001
N of Valid Cases 46

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 11.50.
b. Computed only for a 2x2 table

Table 75: Chi-Square Test- Upper premolars, Males age 10
72

Fig 31. Males age 10: Upper bicuspids

In the Mexican sample, 17 of 23 patients (73.9%) had erupted upper bicuspids. In
the Caucasian sample, 6 of 23 (26.1%) had erupted upper bicuspids. A P value = 0.001
indicates a significant difference in upper bicuspid eruption between male Mexican and
Caucasian patients of age 10. 73.9% of all eruptions were found in the Mexican patient
population.
Lower Bicuspids (l45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 46 100.0% 0 .0% 46 100.0%
Table 76: Case Processing Summary- Lower premolars; Males age 10
73

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 21 2 23
% within ethnic 91.3% 8.7% 100.0%
% within l45s 72.4% 11.8% 50.0%
C
% of Total 45.7% 4.3% 50.0%
Count 8 15 23
% within ethnic 34.8% 65.2% 100.0%
% within l45s 27.6% 88.2% 50.0%
MEX
% of Total 17.4% 32.6% 50.0%
Count 29 17 46
% within ethnic 63.0% 37.0% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 63.0% 37.0% 100.0%
Table 77: Crosstabulation- Lower premolars; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.577E1 1 .000

Continuity
Correction
b

13.436 1 .000

Likelihood Ratio 17.292 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 46

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 8.50.
b. Computed only for a 2x2 table

Table 78: Chi-Square Test- Lower premolars, Males age 10
74

Fig 32. Males age 10: Lower bicuspids

In the Mexican sample, 15 of 23 patients (65.2%) had erupted lower bicuspids. In
the Caucasian sample, 2 of 23 (8.7%) had erupted lower bicuspids. A P value = 0.000
indicates a significant difference in lower bicuspid eruption between male Mexican and
Caucasian patients of age 10. 88.2% of all eruptions were found in the Mexican patient
population.

75
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
46 100.0% 0 .0% 46 100.0%
Table 79: Case Processing Summary- All premolars; Males age 10

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 21 2 23
% within ethnic 91.3% 8.7% 100.0%
% within ul45s 70.0% 12.5% 50.0%
C
% of Total 45.7% 4.3% 50.0%
Count 9 14 23
% within ethnic 39.1% 60.9% 100.0%
% within ul45s 30.0% 87.5% 50.0%
MEX
% of Total 19.6% 30.4% 50.0%
Count 30 16 46
% within ethnic 65.2% 34.8% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 65.2% 34.8% 100.0%
Table 80: Crosstabulation- All premolars; Males age 10

76
Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.380E1 1 .000

Continuity
Correction
b

11.596 1 .001

Likelihood Ratio 15.061 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 46

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 8.00.
b. Computed only for a 2x2 table

Table 81: Chi-Square Test- All premolars, Males age 10

Fig 33. Males age 10: At least one upper and one lower bicuspids

77
In the Mexican sample, 14 of 23 patients (60.9%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 2 of 23 (8.7%) had erupted upper and
lower bicuspids. A P value = 0.000 indicates that a significant difference exists in total
bicuspid eruption between male Mexican and Caucasian patients of age 10. 87.5% of all
eruptions were found in the Mexican population.

Upper Second Molars (u7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 46 100.0% 0 .0% 46 100.0%
Table 82: Case Processing Summary- Upper second molars; Males age 10

78

ethnic * u7s Crosstabulation

u7s

no yes Total
Count 21 2 23
% within ethnic 91.3% 8.7% 100.0%
% within u7s 52.5% 33.3% 50.0%
C
% of Total 45.7% 4.3% 50.0%
Count 19 4 23
% within ethnic 82.6% 17.4% 100.0%
% within u7s 47.5% 66.7% 50.0%
MEX
% of Total 41.3% 8.7% 50.0%
Count 40 6 46
% within ethnic 87.0% 13.0% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 87.0% 13.0% 100.0%
Table 83: Crosstabulation- Upper second molars; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.767
a
1 .381

Continuity
Correction
b

.192 1 .662

Likelihood Ratio .780 1 .377

Fisher's Exact Test

.665 .333
N of Valid Cases 46

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 3.00.
b. Computed only for a 2x2 table

Table 84: Chi-Square Test- Upper second molars, Males age 10
79

Fig 34. Males age 10: Upper second molars

In the Mexican sample, 4 of 23 (17.4%) had erupted upper second molars. In the
Caucasian sample, 2 of 23 (8.7%) had erupted upper second molars. . A P value = 0.381
indicates that no significant difference exists in upper second molar eruption between
male Mexican and Caucasian patients of age 10.

Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 46 100.0% 0 .0% 46 100.0%
Table 85: Case Processing Summary- Lower second molars; Males age 10
80

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 21 2 23
% within ethnic 91.3% 8.7% 100.0%
% within l7s 55.3% 25.0% 50.0%
C
% of Total 45.7% 4.3% 50.0%
Count 17 6 23
% within ethnic 73.9% 26.1% 100.0%
% within l7s 44.7% 75.0% 50.0%
MEX
% of Total 37.0% 13.0% 50.0%
Count 38 8 46
% within ethnic 82.6% 17.4% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 82.6% 17.4% 100.0%
Table 86: Crosstabulation- Lower second molars; Males age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.421
a
1 .120

Continuity
Correction
b

1.362 1 .243

Likelihood Ratio 2.515 1 .113

Fisher's Exact Test

.243 .121
N of Valid Cases 46

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 4.00.
b. Computed only for a 2x2 table

Table 87: Chi-Square Test- Lower second molars, Males age 10
81

Fig 35. Males age 10: Lower second molars

In the Mexican sample, 6 of 23 (26.1%) had erupted lower second molars. In the
Caucasian sample, 2 of 23 (8.7%) had erupted upper second molars. A P value = 0.120
indicates that no significant difference exists in upper second molar eruption between
male Mexican and Caucasian patients of age 10.

82
Sexual comparison for Mexican patients age 10

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Pearson Chi-
Square
1.915E1 15 .207
Likelihood Ratio 25.290 15 .046
N of Valid Cases 50

a. 32 cells (100.0%) have expected count less
than 5. The minimum expected count is .46.
Table 88: Chi-Square Test- All erupted teeth; Females and Males age 10

Fig 36. Differences in dental eruption for Mexican patients age 10

There is no significant difference in eruption timing between male and female
Mexican patients age 10.

83
Females age 11 (n=138)

Fig 37. Distribution graph: Females age 11

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 138 100.0% 0 .0% 138 100.0%
Table 89: Case Processing Summary- Upper canines; Females age 11

84
ethnic * u3s Crosstabulation

u3s

no yes Total
Count 34 40 74
% within ethnic 45.9% 54.1% 100.0%
% within u3s 69.4% 44.9% 53.6%
C
% of Total 24.6% 29.0% 53.6%
Count 15 49 64
% within ethnic 23.4% 76.6% 100.0%
% within u3s 30.6% 55.1% 46.4%
MEX
% of Total 10.9% 35.5% 46.4%
Count 49 89 138
% within ethnic 35.5% 64.5% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 35.5% 64.5% 100.0%
Table 90: Crosstabulation- Upper canines; Females age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
7.593
a
1 .006

Continuity
Correction
b

6.642 1 .010

Likelihood Ratio 7.750 1 .005

Fisher's Exact Test

.007 .005
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 22.72.
b. Computed only for a 2x2 table

Table 91: Chi-Square Test- Upper canines, Females age 11
85

Fig 38. Females age 11: Upper canines

In the Mexican sample, 49 of 64 patients (76.6%) had erupted upper canines. In
the Caucasian sample, 40 of 74 (54.1%) had erupted upper canines. A P value = 0.006
indicates a significant difference in upper canine eruption between female Mexican and
Caucasian patients of age 11. 55.1% of all eruptions were found in the Mexican
population.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 138 100.0% 0 .0% 138 100.0%
Table 92: Case Processing Summary- Lower canines; Females age 11
86

ethnic * l3s Crosstabulation

l3s

no yes Total
Count 14 60 74
% within ethnic 18.9% 81.1% 100.0%
% within l3s 77.8% 50.0% 53.6%
C
% of Total 10.1% 43.5% 53.6%
Count 4 60 64
% within ethnic 6.2% 93.8% 100.0%
% within l3s 22.2% 50.0% 46.4%
MEX
% of Total 2.9% 43.5% 46.4%
Count 18 120 138
% within ethnic 13.0% 87.0% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 13.0% 87.0% 100.0%
Table 93: Crosstabulation- Lower canines; Females age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
4.856
a
1 .028

Continuity
Correction
b

3.804 1 .051

Likelihood Ratio 5.159 1 .023

Fisher's Exact Test

.041 .024
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 8.35.
b. Computed only for a 2x2 table

Table 94: Chi-Square Test- Lower canines, Females age 11
87

Fig 39. Females age 11: Lower canines

In the Mexican sample, 60 of 64 patients (93.8%) had erupted lower canines. In
the Caucasian sample, 60 of 74 (81.1%) had erupted lower canines. A P value = 0.028
indicates a significant difference in lower canine eruption between female Mexican and
Caucasian patients of age 11.
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
138 100.0% 0 .0% 138 100.0%
Table 95: Case Processing Summary- Upper premolars; Females age 11

88
ethnic * u45s Crosstabulation

u45s

no yes Total
Count 39 35 74
% within ethnic 52.7% 47.3% 100.0%
% within u45s 88.6% 37.2% 53.6%
C
% of Total 28.3% 25.4% 53.6%
Count 5 59 64
% within ethnic 7.8% 92.2% 100.0%
% within u45s 11.4% 62.8% 46.4%
MEX
% of Total 3.6% 42.8% 46.4%
Count 44 94 138
% within ethnic 31.9% 68.1% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 31.9% 68.1% 100.0%
Table 96: Crosstabulation- Upper premolars; Females age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.184E1 1 .000

Continuity
Correction
b

29.810 1 .000

Likelihood Ratio 35.311 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 20.41.
b. Computed only for a 2x2 table

Table 97: Chi-Square Test- Upper premolars, Females age 11
89

Fig 40. Females age 11: Upper bicuspids

In the Mexican sample, 59 of 64 patients (92.2%) had erupted upper bicuspids. In
the Caucasian sample, 35 of 74 (47.3%) had erupted upper bicuspids. A P value = 0.000
indicates a significant difference in upper bicuspid eruption between female Mexican and
Caucasian patients of age 11. 62.8% of all eruptions were found in the Mexican patient
population.
Lower Bicuspids (l45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 138 100.0% 0 .0% 138 100.0%
Table 98: Case Processing Summary- Lower premolars; Females age 11
90

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 41 33 74
% within ethnic 55.4% 44.6% 100.0%
% within l45s 91.1% 35.5% 53.6%
C
% of Total 29.7% 23.9% 53.6%
Count 4 60 64
% within ethnic 6.2% 93.8% 100.0%
% within l45s 8.9% 64.5% 46.4%
MEX
% of Total 2.9% 43.5% 46.4%
Count 45 93 138
% within ethnic 32.6% 67.4% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 32.6% 67.4% 100.0%
Table 99: Crosstabulation- Lower premolars; Females age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.773E1 1 .000

Continuity
Correction
b

35.531 1 .000

Likelihood Ratio 42.614 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 20.87.
b. Computed only for a 2x2 table

Table 100: Chi-Square Test- Lower premolars, Females age 11
91

Fig 41. Females age 11: Lower bicuspids

In the Mexican sample, 60 of 64 patients (93.8%) had erupted lower bicuspids. In
the Caucasian sample, 33 of 74 (44.6%) had erupted lower bicuspids. A P value = 0.000
indicates a significant difference in lower bicuspid eruption between female Mexican and
Caucasian patients of age 11. 64.5% of all eruptions were found in the Mexican patient
population.

92
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
138 100.0% 0 .0% 138 100.0%
Table 101: Case Processing Summary- All premolars; Females age 11

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 46 28 74
% within ethnic 62.2% 37.8% 100.0%
% within ul45s 86.8% 32.9% 53.6%
C
% of Total 33.3% 20.3% 53.6%
Count 7 57 64
% within ethnic 10.9% 89.1% 100.0%
% within ul45s 13.2% 67.1% 46.4%
MEX
% of Total 5.1% 41.3% 46.4%
Count 53 85 138
% within ethnic 38.4% 61.6% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 38.4% 61.6% 100.0%
Table 102: Crosstabulation- All premolars; Females age 11

93

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.807E1 1 .000

Continuity
Correction
b

35.933 1 .000

Likelihood Ratio 41.471 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 24.58.
b. Computed only for a 2x2 table

Table 103: Chi-Square Test- All premolars, Females age 11

Fig 42. Females age 11: At least one upper and one lower bicuspid

94
In the Mexican sample, 57 of 64 patients (89.1%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 28 of 74 (37.8%) had erupted upper
and lower bicuspids. A P value = 0.000 indicates that a significant difference exists in
total bicuspid eruption between female Mexican and Caucasian patients of age 11.
67.1% of all eruptions were found in the Mexican patient population.

Upper Second Molars (u7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 138 100.0% 0 .0% 138 100.0%
Table 104: Case Processing Summary- Upper second molars; Females age 11

95
ethnic * u7s Crosstabulation

u7s

no yes Total
Count 53 21 74
% within ethnic 71.6% 28.4% 100.0%
% within u7s 56.4% 47.7% 53.6%
C
% of Total 38.4% 15.2% 53.6%
Count 41 23 64
% within ethnic 64.1% 35.9% 100.0%
% within u7s 43.6% 52.3% 46.4%
MEX
% of Total 29.7% 16.7% 46.4%
Count 94 44 138
% within ethnic 68.1% 31.9% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 68.1% 31.9% 100.0%
Table 105: Crosstabulation- Upper second molars; Females age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.903
a
1 .342

Continuity
Correction
b

.588 1 .443

Likelihood Ratio .902 1 .342

Fisher's Exact Test

.365 .221
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 20.41.
b. Computed only for a 2x2 table

Table 106: Chi-Square Test- Upper second molars, Females age 11
96

Fig 43. Females age 11: Upper second molars

In the Mexican sample, 23 of 64 (35.9%) had erupted upper second molars. In the
Caucasian sample, 21 of 74 (28.4%) had erupted upper second molars. A P value = 0.342
indicates that no significant difference exists in upper second molar eruption between
female Mexican and Caucasian patients of age 11, however, 52.3% of all U7 eruptions
occurred in the Mexican sample.

97
Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 138 100.0% 0 .0% 138 100.0%
Table 107: Case Processing Summary- Lower second molars; Females age 11

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 49 25 74
% within ethnic 66.2% 33.8% 100.0%
% within l7s 65.3% 39.7% 53.6%
C
% of Total 35.5% 18.1% 53.6%
Count 26 38 64
% within ethnic 40.6% 59.4% 100.0%
% within l7s 34.7% 60.3% 46.4%
MEX
% of Total 18.8% 27.5% 46.4%
Count 75 63 138
% within ethnic 54.3% 45.7% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 54.3% 45.7% 100.0%
Table 108: Crosstabulation- Lower second molars; Females age 11

98

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
9.059
a
1 .003

Continuity
Correction
b

8.057 1 .005

Likelihood Ratio 9.145 1 .002

Fisher's Exact Test

.004 .002
N of Valid Cases 138

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 29.22.
b. Computed only for a 2x2 table

Table 109: Chi-Square Test- Lower second molars, Females age 11

Fig 44. Females age 11: Lower second molars

99

In the Mexican sample, 38 of 64 (59.4%) had erupted lower second molars. In the
Caucasian sample, 25 of 74 (33.8%) had erupted upper second molars. A P value = 0.003
indicates that a significant difference exists in lower second molar eruption between
female Mexican and Caucasian patients of age 11. 60.3% of all eruptions were found in
the Mexican patient population.

Males age 11 (n=123)

Fig 45. Distribution graph: Males age 11

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 123 100.0% 0 .0% 123 100.0%
Table 110: Case Processing Summary- Upper canines; Males age 11

100
ethnic * u3s Crosstabulation

u3s

no yes Total
Count 39 21 60
% within ethnic 65.0% 35.0% 100.0%
% within u3s 55.7% 39.6% 48.8%
C
% of Total 31.7% 17.1% 48.8%
Count 31 32 63
% within ethnic 49.2% 50.8% 100.0%
% within u3s 44.3% 60.4% 51.2%
MEX
% of Total 25.2% 26.0% 51.2%
Count 70 53 123
% within ethnic 56.9% 43.1% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 56.9% 43.1% 100.0%
Table 111: Crosstabulation- Upper canines; Males age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.126
a
1 .077

Continuity
Correction
b

2.515 1 .113

Likelihood Ratio 3.143 1 .076

Fisher's Exact Test

.101 .056
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 25.85.
b. Computed only for a 2x2 table

Table 112: Chi-Square Test- Upper canines, Males age 11
101

Fig 46. Males age 11: Upper canines

In the Mexican sample, 32 of 63 patients (50.8%) had erupted upper canines. In
the Caucasian sample, 21 of 60 (35.0%) had erupted upper canines. A P value = 0.077
indicates a tendency towards earlier eruption of upper cuspids in the Mexican population,
however, no significant difference was evident in upper canine eruption between male
Mexican and Caucasian patients of age 11.

102
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 123 100.0% 0 .0% 123 100.0%
Table 113: Case Processing Summary- Lower canines; Males age 11

ethnic * l3s Crosstabulation

l3s

no yes Total
Count 18 42 60
% within ethnic 30.0% 70.0% 100.0%
% within l3s 64.3% 44.2% 48.8%
C
% of Total 14.6% 34.1% 48.8%
Count 10 53 63
% within ethnic 15.9% 84.1% 100.0%
% within l3s 35.7% 55.8% 51.2%
MEX
% of Total 8.1% 43.1% 51.2%
Count 28 95 123
% within ethnic 22.8% 77.2% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 22.8% 77.2% 100.0%
Table 114: Crosstabulation- Lower canines; Males age 11

103
Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.488
a
1 .062

Continuity
Correction
b

2.731 1 .098

Likelihood Ratio 3.521 1 .061

Fisher's Exact Test

.085 .049
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 13.66.
b. Computed only for a 2x2 table

Table 115: Chi-Square Test- Lower canines, Males age 11

Fig 47. Males age 11: Lower canines

104
In the Mexican sample, 53 of 63 patients (84.1%) had erupted lower canines. In
the Caucasian sample, 42 of 60 (70.0%) had erupted lower canines. A P value = 0.062
indicates a trend towards earlier lower canine eruption in male Mexican patients,
however no significant difference exists.
Upper Bicuspids (u45s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
123 100.0% 0 .0% 123 100.0%
Table 116: Case Processing Summary- Upper premolars; Males age 11

ethnic * u45s Crosstabulation

u45s

no yes Total
Count 43 17 60
% within ethnic 71.7% 28.3% 100.0%
% within u45s 79.6% 24.6% 48.8%
C
% of Total 35.0% 13.8% 48.8%
Count 11 52 63
% within ethnic 17.5% 82.5% 100.0%
% within u45s 20.4% 75.4% 51.2%
MEX
% of Total 8.9% 42.3% 51.2%
Count 54 69 123
% within ethnic 43.9% 56.1% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 43.9% 56.1% 100.0%
Table 117: Crosstabulation- Upper premolars; Males age 11
105

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.667E1 1 .000

Continuity
Correction
b

34.497 1 .000

Likelihood Ratio 38.800 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 26.34.
b. Computed only for a 2x2 table

Table 118: Chi-Square Test- Upper premolars, Males age 11

Fig 48. Males age 11: Upper bicuspids

106
In the Mexican sample, 52 of 63 patients (82.5%) had erupted upper bicuspids. In
the Caucasian sample, 17 of 60 (28.3%) had erupted upper bicuspids. A P value = 0.000
indicates a significant difference in eruption between male Mexican and Caucasian
patients of age 11. 75.4% of all eruptions were found in the Mexican patient population.
Lower Bicuspids (l45s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 123 100.0% 0 .0% 123 100.0%
Table 119: Case Processing Summary- Lower premolars; Males age 11

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 38 22 60
% within ethnic 63.3% 36.7% 100.0%
% within l45s 80.9% 28.9% 48.8%
C
% of Total 30.9% 17.9% 48.8%
Count 9 54 63
% within ethnic 14.3% 85.7% 100.0%
% within l45s 19.1% 71.1% 51.2%
MEX
% of Total 7.3% 43.9% 51.2%
Count 47 76 123
% within ethnic 38.2% 61.8% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 38.2% 61.8% 100.0%
Table 120: Crosstabulation- Lower premolars; Males age 11

107
Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.131E1 1 .000

Continuity
Correction
b

29.270 1 .000

Likelihood Ratio 33.078 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 22.93.
b. Computed only for a 2x2 table

Table 121: Chi-Square Test- Lower premolars, Males age 11

Fig 49. Males age 11: Lower bicuspids

In the Mexican sample, 54 of 63 patients (85.7%) had erupted lower bicuspids. In
the Caucasian sample, 22 of 60 (36.7%) had erupted lower bicuspids. A P value = 0.000
108
indicates a significant difference in lower bicuspid eruption between male Mexican and
Caucasian patients of age 11. 71.1% of all eruptions were found in the Mexican patient
population
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
123 100.0% 0 .0% 123 100.0%
Table 122: Case Processing Summary- All premolars; Males age 11

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 48 12 60
% within ethnic 80.0% 20.0% 100.0%
% within ul45s 78.7% 19.4% 48.8%
C
% of Total 39.0% 9.8% 48.8%
Count 13 50 63
% within ethnic 20.6% 79.4% 100.0%
% within ul45s 21.3% 80.6% 51.2%
MEX
% of Total 10.6% 40.7% 51.2%
Count 61 62 123
% within ethnic 49.6% 50.4% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 49.6% 50.4% 100.0%
Table 123: Crosstabulation- All premolars; Males age 11
109

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
4.332E1 1 .000

Continuity
Correction
b

40.983 1 .000

Likelihood Ratio 46.314 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 29.76.
b. Computed only for a 2x2 table

Table 124: Chi-Square Test- All premolars, Males age 11

Fig 50. Males age 11: At least one upper and one lower bicuspids

110
In the Mexican sample, 50 of 63 patients (79.4%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 12 of 60 (20.0%) had erupted upper
and lower bicuspids. A P value = 0.000 indicates that a significant difference exists in
total bicuspid eruption between male Mexican and Caucasian patients of age 11.
Upper Second Molars (u7s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 123 100.0% 0 .0% 123 100.0%
Table 125: Case Processing Summary- Upper second molars; Males age 11

ethnic * u7s Crosstabulation

u7s

no yes Total
Count 53 7 60
% within ethnic 88.3% 11.7% 100.0%
% within u7s 60.2% 20.0% 48.8%
C
% of Total 43.1% 5.7% 48.8%
Count 35 28 63
% within ethnic 55.6% 44.4% 100.0%
% within u7s 39.8% 80.0% 51.2%
MEX
% of Total 28.5% 22.8% 51.2%
Count 88 35 123
% within ethnic 71.5% 28.5% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 71.5% 28.5% 100.0%
Table 126: Crosstabulation- Upper second molars; Males age 11

111
Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.622E1 1 .000

Continuity
Correction
b

14.648 1 .000

Likelihood Ratio 17.127 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 17.07.
b. Computed only for a 2x2 table

Table 127: Chi-Square Test- Upper second molars, Males age 11

Fig 51. Males age 11: Upper second molars

In the Mexican sample, 28 of 63 (44.4%) had erupted upper second molars. In the
Caucasian sample, 7 of 60 (11.7%) had erupted upper second molars. A P value = 0.000
112
indicates that a significant difference exists in upper second molar eruption between male
Mexican and Caucasian patients of age 11. 80.0% of all possible eruptions occurred in
the Mexican population.

Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 123 100.0% 0 .0% 123 100.0%
Table 128: Case Processing Summary- Lower second molars; Males age 11

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 48 12 60
% within ethnic 80.0% 20.0% 100.0%
% within l7s 60.0% 27.9% 48.8%
C
% of Total 39.0% 9.8% 48.8%
Count 32 31 63
% within ethnic 50.8% 49.2% 100.0%
% within l7s 40.0% 72.1% 51.2%
MEX
% of Total 26.0% 25.2% 51.2%
Count 80 43 123
% within ethnic 65.0% 35.0% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 65.0% 35.0% 100.0%
Table 129: Crosstabulation- Lower second molars; Males age 11
113

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.153E1 1 .001

Continuity
Correction
b

10.280 1 .001

Likelihood Ratio 11.841 1 .001

Fisher's Exact Test

.001 .001
N of Valid Cases 123

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 20.98.
b. Computed only for a 2x2 table

Table 130: Chi-Square Test- Lower second molars, Males age 11

Fig 52. Males age 11: Lower second molars

114
In the Mexican sample, 31 of 63 (49.2%) had erupted upper second molars. In the
Caucasian sample, 12 of 60 (20.0%) had erupted upper second molars. A P value = 0.001
indicates that a significant difference exists in upper second molar eruption between male
Mexican and Caucasian patients of age 11. 72.1% of all possible eruptions occurred in
the Mexican population.

Sexual comparison for Mexican patients age 11

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Pearson Chi-
Square
1.515E1 15 .441
Likelihood Ratio 17.527 15 .288
N of Valid Cases 126

a. 26 cells (81.3%) have expected count less than
5. The minimum expected count is .49.
Table 131: Chi-Square Test- All erupted teeth; Females and Males age 11
115

Fig 53. Differences in dental eruption for Mexican patients age 11

There is no significant difference in total eruptions between Mexican males and
females age 11, as indicated by P=0.441.

116
Females age 12 (n=50)

Fig 54. Distribution graph: Females age 12

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 50 100.0% 0 .0% 50 100.0%
Table 132: Case Processing Summary- Upper canines; Females age 12

117

ethnic * u3s Crosstabulation

u3s

no yes Total
Count 8 19 27
% within ethnic 29.6% 70.4% 100.0%
% within u3s 72.7% 48.7% 54.0%
C
% of Total 16.0% 38.0% 54.0%
Count 3 20 23
% within ethnic 13.0% 87.0% 100.0%
% within u3s 27.3% 51.3% 46.0%
MEX
% of Total 6.0% 40.0% 46.0%
Count 11 39 50
% within ethnic 22.0% 78.0% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 22.0% 78.0% 100.0%
Table 133: Crosstabulation- Upper canines; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.991
a
1 .158

Continuity
Correction
b

1.142 1 .285

Likelihood Ratio 2.064 1 .151

Fisher's Exact Test

.189 .143
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 5.06.
b. Computed only for a 2x2 table

Table 134: Chi-Square Test- Upper canines, Females age 12
118

Fig 55. Females age 12: Upper canines

In the Mexican sample, 20 of 23 patients (87.0%) had erupted upper canines. In
the Caucasian sample, 19 of 27 (70.4%) had erupted upper canines. A P value = 0.158
indicates no significant difference in upper canine eruption between female Mexican and
Caucasian patients of age 12.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 50 100.0% 0 .0% 50 100.0%
Table 135: Case Processing Summary- Lower canines; Females age 12
119

ethnic * l3s Crosstabulation

l3s

no yes Total
Count 3 24 27
% within ethnic 11.1% 88.9% 100.0%
% within l3s 75.0% 52.2% 54.0%
C
% of Total 6.0% 48.0% 54.0%
Count 1 22 23
% within ethnic 4.3% 95.7% 100.0%
% within l3s 25.0% 47.8% 46.0%
MEX
% of Total 2.0% 44.0% 46.0%
Count 4 46 50
% within ethnic 8.0% 92.0% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 8.0% 92.0% 100.0%
Table 136: Crosstabulation- Lower canines; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
.772
a
1 .380

Continuity
Correction
b

.126 1 .722

Likelihood Ratio .813 1 .367

Fisher's Exact Test

.614 .368
N of Valid Cases 50

a. 2 cells (50.0%) have expected count less than 5. The minimum expected
count is 1.84.
b. Computed only for a 2x2 table

Table 137: Chi-Square Test- Lower canines, Females age 12
120

Fig 56. Females age 12: Lower canines

In the Mexican sample, 22 of 23 patients (95.7%) had erupted lower canines. In
the Caucasian sample, 24 of 27 (88.9%) had erupted lower canines. A P value = 0.380
indicates no significant difference in lower canine eruption between female Mexican and
Caucasian patients of age 12.
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
50 100.0% 0 .0% 50 100.0%
Table 138: Case Processing Summary- Upper premolars; Females age 12

121
ethnic * u45s Crosstabulation

u45s

no yes Total
Count 11 16 27
% within ethnic 40.7% 59.3% 100.0%
% within u45s 91.7% 42.1% 54.0%
C
% of Total 22.0% 32.0% 54.0%
Count 1 22 23
% within ethnic 4.3% 95.7% 100.0%
% within u45s 8.3% 57.9% 46.0%
MEX
% of Total 2.0% 44.0% 46.0%
Count 12 38 50
% within ethnic 24.0% 76.0% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 24.0% 76.0% 100.0%
Table 139: Crosstabulation- Upper premolars; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
9.018
a
1 .003

Continuity
Correction
b

7.134 1 .008

Likelihood Ratio 10.382 1 .001

Fisher's Exact Test

.003 .003
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 5.52.
b. Computed only for a 2x2 table

Table 140: Chi-Square Test- Upper premolars, Females age 12
122

Fig 57. Females age 12: Upper bicuspids

In the Mexican sample, 22 of 23 patients (95.7%) had erupted upper bicuspids. In
the Caucasian sample, 16 of 27 (59.3%) had erupted upper bicuspids. A P value = 0.003
indicates a significant difference in upper bicuspid eruption between female Mexican and
Caucasian patients of age 12. 57.9% of all eruptions were found in the Mexican patient
population.
Lower Bicuspids (l45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 50 100.0% 0 .0% 50 100.0%
Table 141: Case Processing Summary- Lower premolars; Females age 12
123

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 10 17 27
% within ethnic 37.0% 63.0% 100.0%
% within l45s 90.9% 43.6% 54.0%
C
% of Total 20.0% 34.0% 54.0%
Count 1 22 23
% within ethnic 4.3% 95.7% 100.0%
% within l45s 9.1% 56.4% 46.0%
MEX
% of Total 2.0% 44.0% 46.0%
Count 11 39 50
% within ethnic 22.0% 78.0% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 22.0% 78.0% 100.0%
Table 142: Crosstabulation- Lower premolars; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
7.734
a
1 .005

Continuity
Correction
b

5.946 1 .015

Likelihood Ratio 8.870 1 .003

Fisher's Exact Test

.006 .006
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 5.06.
b. Computed only for a 2x2 table

Table 143: Chi-Square Test- Lower premolars, Females age 12
124

Fig 58. Females age 12: Lower bicuspids

In the Mexican sample, 2 of 23 patients (95.7%) had erupted lower bicuspids. In
the Caucasian sample, 17 of 27 (63.0%) had erupted lower bicuspids. A P value = 0.005
indicates a significant difference in lower bicuspid eruption between female Mexican and
Caucasian patients of age 12. 56.4% of all eruptions were found in the Mexican patient
population.
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
50 100.0% 0 .0% 50 100.0%
Table 144: Case Processing Summary- All premolars; Females age 12
125

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 12 15 27
% within ethnic 44.4% 55.6% 100.0%
% within ul45s 92.3% 40.5% 54.0%
C
% of Total 24.0% 30.0% 54.0%
Count 1 22 23
% within ethnic 4.3% 95.7% 100.0%
% within ul45s 7.7% 59.5% 46.0%
MEX
% of Total 2.0% 44.0% 46.0%
Count 13 37 50
% within ethnic 26.0% 74.0% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 26.0% 74.0% 100.0%
Table 145: Crosstabulation- All premolars; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.038E1 1 .001

Continuity
Correction
b

8.399 1 .004

Likelihood Ratio 11.983 1 .001

Fisher's Exact Test

.001 .001
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 5.98.
b. Computed only for a 2x2 table

Table 146: Chi-Square Test- All premolars, Females age 12
126

Fig 59. Females age 12: At least one upper and one lower bicuspids

In the Mexican sample, 22 of 23 patients (95.7%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 15 of 27 (55.6%) had erupted upper
and lower bicuspids. A P value = 0.001 indicates that a significant difference exists in
total bicuspid eruption between female Mexican and Caucasian patients of age 12.
59.5% of all eruptions were found in the Mexican patient population.

127
Upper Second Molars (u7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 50 100.0% 0 .0% 50 100.0%
Table 147: Case Processing Summary- Upper second molars; Females age 12

ethnic * u7s Crosstabulation

u7s

no yes Total
Count 17 10 27
% within ethnic 63.0% 37.0% 100.0%
% within u7s 70.8% 38.5% 54.0%
C
% of Total 34.0% 20.0% 54.0%
Count 7 16 23
% within ethnic 30.4% 69.6% 100.0%
% within u7s 29.2% 61.5% 46.0%
MEX
% of Total 14.0% 32.0% 46.0%
Count 24 26 50
% within ethnic 48.0% 52.0% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 48.0% 52.0% 100.0%
Table 148: Crosstabulation- Upper second molars; Females age 12

128
Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
5.265
a
1 .022

Continuity
Correction
b

4.042 1 .044

Likelihood Ratio 5.373 1 .020

Fisher's Exact Test

.027 .022
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 11.04.
b. Computed only for a 2x2 table

Table 149: Chi-Square Test- Upper second molars, Females age 12

Fig 60. Females age 12: Upper second molars

129

In the Mexican sample, 16 of 23 (69.6%) had erupted upper second molars. In the
Caucasian sample, 10 of 27 (37.0%) had erupted upper second molars. A P value = 0.022
indicates that a significant difference exists in upper second molar eruption between
female Mexican and Caucasian patients of age 12. 61.5% of all eruptions were found in
the Mexican patient population.

Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 50 100.0% 0 .0% 50 100.0%
Table 150: Case Processing Summary- Lower second molars; Females age 12

130
ethnic * l7s Crosstabulation

l7s

no yes Total
Count 11 16 27
% within ethnic 40.7% 59.3% 100.0%
% within l7s 73.3% 45.7% 54.0%
C
% of Total 22.0% 32.0% 54.0%
Count 4 19 23
% within ethnic 17.4% 82.6% 100.0%
% within l7s 26.7% 54.3% 46.0%
MEX
% of Total 8.0% 38.0% 46.0%
Count 15 35 50
% within ethnic 30.0% 70.0% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 30.0% 70.0% 100.0%
Table 151: Crosstabulation- Lower second molars; Females age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
3.224
a
1 .073

Continuity
Correction
b

2.208 1 .137

Likelihood Ratio 3.334 1 .068

Fisher's Exact Test

.121 .067
N of Valid Cases 50

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 6.90.
b. Computed only for a 2x2 table

Table 152: Chi-Square Test- Lower second molars, Females age 12
131

Fig 61. Females age 12: Lower second molars

In the Mexican sample, 19 of 23 (82.6%) had erupted lower second molars. In the
Caucasian sample, 16 of 27 (59.3%) had erupted upper second molars. A P value = 0.073
indicates that no significant difference exists in lower second molar eruption between
female Mexican and Caucasian patients of age 12.

132
Males age 12 (n=55)

Fig 62. Distribution graph: Males age 12

Upper Canines (u3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u3s 55 100.0% 0 .0% 55 100.0%
Table 153: Case Processing Summary- Upper canines; Males age 12

133
ethnic * u3s Crosstabulation

u3s

no yes Total
Count 21 10 31
% within ethnic 67.7% 32.3% 100.0%
% within u3s 87.5% 32.3% 56.4%
C
% of Total 38.2% 18.2% 56.4%
Count 3 21 24
% within ethnic 12.5% 87.5% 100.0%
% within u3s 12.5% 67.7% 43.6%
MEX
% of Total 5.5% 38.2% 43.6%
Count 24 31 55
% within ethnic 43.6% 56.4% 100.0%
% within u3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 43.6% 56.4% 100.0%
Table 154: Crosstabulation- Upper canines; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.678E1 1 .000

Continuity
Correction
b

14.613 1 .000

Likelihood Ratio 18.282 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 10.47.
b. Computed only for a 2x2 table

Table 155: Chi-Square Test- Upper canines, Males age 12
134

Fig 63: Males age 12: Upper canines

In the Mexican sample, 21 of 24 patients (87.5%) had erupted upper canines. In
the Caucasian sample, 10 of 31 (32.3%) had erupted upper canines. A P value = 0.000
indicates that a significant difference exists in upper canine eruption between male
Mexican and Caucasian patients of age 12. 67.7% of all possible eruptions occurred in
the Mexican population.
Lower Canines (l3s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l3s 55 100.0% 0 .0% 55 100.0%
Table 156: Case Processing Summary- Lower canines; Males age 12
135

ethnic * l3s Crosstabulation

l3s

no yes Total
Count 7 24 31
% within ethnic 22.6% 77.4% 100.0%
% within l3s 77.8% 52.2% 56.4%
C
% of Total 12.7% 43.6% 56.4%
Count 2 22 24
% within ethnic 8.3% 91.7% 100.0%
% within l3s 22.2% 47.8% 43.6%
MEX
% of Total 3.6% 40.0% 43.6%
Count 9 46 55
% within ethnic 16.4% 83.6% 100.0%
% within l3s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 16.4% 83.6% 100.0%
Table 157: Crosstabulation- Lower canines; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
2.006
a
1 .157

Continuity
Correction
b

1.100 1 .294

Likelihood Ratio 2.136 1 .144

Fisher's Exact Test

.271 .147
N of Valid Cases 55

a. 1 cells (25.0%) have expected count less than 5. The minimum expected
count is 3.93.
b. Computed only for a 2x2 table

Table 158: Chi-Square Test- Lower canines, Males age 12
136

Fig 64: Males age 12: Lower canines

In the Mexican sample, 22 of 24 patients (91.7%) had erupted lower canines. In
the Caucasian sample, 24 of 31 (77.4%) had erupted lower canines. A P value = 0.157
indicates no significant difference in lower canine eruption between male Mexican and
Caucasian patients of age 12.
Upper Bicuspids (u45s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
u45s
55 100.0% 0 .0% 55 100.0%
Table 159: Case Processing Summary- Upper premolars; Males age 12
137

ethnic * u45s Crosstabulation

u45s

no yes Total
Count 15 16 31
% within ethnic 48.4% 51.6% 100.0%
% within u45s 100.0% 40.0% 56.4%
C
% of Total 27.3% 29.1% 56.4%
Count 0 24 24
% within ethnic .0% 100.0% 100.0%
% within u45s .0% 60.0% 43.6%
MEX
% of Total .0% 43.6% 43.6%
Count 15 40 55
% within ethnic 27.3% 72.7% 100.0%
% within u45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 27.3% 72.7% 100.0%
Table 160: Crosstabulation- Upper premolars; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.597E1 1 .000

Continuity
Correction
b

13.621 1 .000

Likelihood Ratio 21.512 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 6.55.
b. Computed only for a 2x2 table

Table 161: Chi-Square Test- Upper premolars, Males age 12
138

Fig 65. Males age 12: Upper bicuspids

In the Mexican sample, 24 of 24 patients (100.0%) had erupted upper bicuspids.
In the Caucasian sample, 16 of 31 (51.6%) had erupted upper bicuspids. A P value =
0.000 indicates a significant difference in upper bicuspid eruption between male Mexican
and Caucasian patients of age 12. 60.0% of all eruptions were found in the Mexican
patient population.
Lower Bicuspids (l45s)
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l45s 55 100.0% 0 .0% 55 100.0%
Table 162: Case Processing Summary- Lower premolars; Males age 12
139

ethnic * l45s Crosstabulation

l45s

no yes Total
Count 18 13 31
% within ethnic 58.1% 41.9% 100.0%
% within l45s 90.0% 37.1% 56.4%
C
% of Total 32.7% 23.6% 56.4%
Count 2 22 24
% within ethnic 8.3% 91.7% 100.0%
% within l45s 10.0% 62.9% 43.6%
MEX
% of Total 3.6% 40.0% 43.6%
Count 20 35 55
% within ethnic 36.4% 63.6% 100.0%
% within l45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 36.4% 63.6% 100.0%
Table 163: Crosstabulation- Lower premolars; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.446E1 1 .000

Continuity
Correction
b

12.388 1 .000

Likelihood Ratio 16.170 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 8.73.
b. Computed only for a 2x2 table

Table 164: Chi-Square Test- Lower premolars, Males age 12
140

Fig 66. Males age 12: Lower bicuspids

In the Mexican sample, 22 of 24 patients (91.7%) had erupted lower bicuspids. In
the Caucasian sample, 13 of 31 (41.9%) had erupted lower bicuspids. A P value = 0.000
indicates a significant difference in lower bicuspid eruption between male Mexican and
Caucasian patients of age 12. 62.9% of all eruptions were found in the Mexican patient
population.
All Bicuspids (ul45s)- at least one upper and one lower bicuspid present
Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic *
ul45s
55 100.0% 0 .0% 55 100.0%
Table 165: Case Processing Summary- All premolars; Males age 12
141

ethnic * ul45s Crosstabulation

ul45s

no yes Total
Count 19 12 31
% within ethnic 61.3% 38.7% 100.0%
% within ul45s 90.5% 35.3% 56.4%
C
% of Total 34.5% 21.8% 56.4%
Count 2 22 24
% within ethnic 8.3% 91.7% 100.0%
% within ul45s 9.5% 64.7% 43.6%
MEX
% of Total 3.6% 40.0% 43.6%
Count 21 34 55
% within ethnic 38.2% 61.8% 100.0%
% within ul45s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 38.2% 61.8% 100.0%
Table 166: Crosstabulation- All premolars; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
1.607E1 1 .000

Continuity
Correction
b

13.907 1 .000

Likelihood Ratio 17.995 1 .000

Fisher's Exact Test

.000 .000
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 9.16.
b. Computed only for a 2x2 table

Table 167: Chi-Square Test- All premolars, Males age 12
142

Fig 67. Males age 12: At least one upper and one lower bicuspids

In the Mexican sample, 22 of 24 patients (91.7%) had at least one upper and one
lower bicuspid erupted. In the Caucasian sample, 12 of 31 (38.7%) had erupted upper
and lower bicuspids. A P value = 0.000 indicates that a significant difference exists in
total bicuspid eruption between male Mexican and Caucasian patients of age 12. 64.7%
of all eruptions were found in the Mexican population.
Upper Second Molars (u7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * u7s 55 100.0% 0 .0% 55 100.0%
Table 168: Case Processing Summary- Upper second molars; Males age 12
143

ethnic * u7s Crosstabulation

u7s

no yes Total
Count 19 12 31
% within ethnic 61.3% 38.7% 100.0%
% within u7s 73.1% 41.4% 56.4%
C
% of Total 34.5% 21.8% 56.4%
Count 7 17 24
% within ethnic 29.2% 70.8% 100.0%
% within u7s 26.9% 58.6% 43.6%
MEX
% of Total 12.7% 30.9% 43.6%
Count 26 29 55
% within ethnic 47.3% 52.7% 100.0%
% within u7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 47.3% 52.7% 100.0%
Table 169: Crosstabulation- Upper second molars; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
5.600
a
1 .018

Continuity
Correction
b

4.386 1 .036

Likelihood Ratio 5.727 1 .017

Fisher's Exact Test

.029 .018
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 11.35.
b. Computed only for a 2x2 table

Table 170: Chi-Square Test- Upper second molars, Males age 12
144

Fig 68. Males age 12: Upper second molars

In the Mexican sample, 17 of 24 (70.8%) had erupted upper second molars. In the
Caucasian sample, 12 of 31 (38.7%) had erupted upper second molars. A P value = 0.018
indicates that a significant difference exists in upper second molar eruption between male
Mexican and Caucasian patients of age 12. 58.6% of all possible eruptions occurred in
the Mexican population.
Lower Second Molars (l7s)

Case Processing Summary

Cases

Valid Missing Total

N Percent N Percent N Percent
ethnic * l7s 55 100.0% 0 .0% 55 100.0%
Table 171: Case Processing Summary- Lower second molars; Males age 12
145

ethnic * l7s Crosstabulation

l7s

no yes Total
Count 18 13 31
% within ethnic 58.1% 41.9% 100.0%
% within l7s 78.3% 40.6% 56.4%
C
% of Total 32.7% 23.6% 56.4%
Count 5 19 24
% within ethnic 20.8% 79.2% 100.0%
% within l7s 21.7% 59.4% 43.6%
MEX
% of Total 9.1% 34.5% 43.6%
Count 23 32 55
% within ethnic 41.8% 58.2% 100.0%
% within l7s 100.0% 100.0% 100.0%
ethnic
Total
% of Total 41.8% 58.2% 100.0%
Table 172: Crosstabulation- Lower second molars; Males age 12

Chi-Square Tests

Value df
Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-
Square
7.707
a
1 .006

Continuity
Correction
b

6.252 1 .012

Likelihood Ratio 8.038 1 .005

Fisher's Exact Test

.007 .006
N of Valid Cases 55

a. 0 cells (.0%) have expected count less than 5. The minimum expected count
is 10.04.
b. Computed only for a 2x2 table

Table 173: Chi-Square Test- Lower second molars, Males age 12
146

Fig 69. Males age 12: Lower second molars

In the Mexican sample, 19 of 24 (79.2%) had erupted upper second molars. In the
Caucasian sample, 13 of 31 (41.9%) had erupted upper second molars. A P value = 0.006
indicates that a significant difference exists in upper second molar eruption between male
Mexican and Caucasian patients of age 12. 59.4% of all possible eruptions occurred in
the Mexican population.

147
Sexual comparison for Mexican patients age 12

Chi-Square Tests

Value df
Asymp. Sig. (2-
sided)
Pearson Chi-Square 1.102E1 10 .356
Likelihood Ratio 14.928 10 .135
N of Valid Cases 47

a. 20 cells (90.9%) have expected count less than 5. The minimum
expected count is .49.
Table 174: Chi-Square Test- All erupted teeth; Females and Males age 12

Fig 70. Differences in dental eruption for Mexican patients age 12

There is no significant difference in eruption timing between male and females
Mexican patients as indicated by P=0.356.

148
CHAPTER 6: LIMITATIONS

Information obtained from the patient’s history was deemed reliable. Although
all medical histories were screened for conditions that may affect the eruption of teeth, it
is possible that the patient withheld information or that the patient remains undiagnosed
for any of these conditions.
Data collected for this study was compared with data collected by another
practitioner for a different study. Both researchers were calibrated with the same mentor
but not with each other. Although not likely, inter-researcher errors of calibration may be
present in the data collection process.
The assumption was made that the sample of subjects is representative of the
general population. However, because this study was limited to subjects living in two
geographical areas, Mexico City and the Los Angeles areas, the results of this study may
only be applicable to these regions’ populations. Because the two study populations
originate from different geographical areas, the possibility exists that other variables
might have been introduced. Variables such as socioeconomic and nutritional status were
not controlled and the possibility exists that these factors are related to the rate of growth
and development and therefore eruption of teeth.

149
CHAPTER 7: DISCUSSION

Many factors play a role in dental development and eruption. Demerjian in 1986
advised that observed racial variations need to take into account powerful environmental
factors that are widespread in the communities, e.g. nutritional factors, before
conclusively attributing the observed age differences to genetics alone.[31, 44] Others
have suggested that socioeconomic status, and the associated quality of nutrition, could
also play a role in dental development, with underprivileged children showing
comparative retarded eruption relative to their ethnic counterparts. [46] Breastfeeding
has also been suggested as a factor that contributes to earlier dental development, but this
occurrence has been described for the primary dentition and not for the permanent
dentition. [47]
A considerable percentage of the population in the United States, and more
specifically in the Los Angeles area, is of Mexican descent. It is important for practicing
orthodontists to take into account the different populations and their development when
planning for growth and development modification and also for general orthodontic
treatment. Dental development has been linked to chronologic age, and to different
physiological variables such as skeletal maturity, body height and weight. Many authors
have described the earlier development seen in Hispanic patients when compared with
Caucasian patients. [22, 48]

150
The purpose of this study was to compare permanent eruption timing in a
Caucasian sample of patients from the Los Angeles area to a Mexican sample of patients
from the Mexico City area, and to compare the results with those reported previously for
a Hispanic sample.
As previously mentioned, the accepted standard timings of eruption are as
follows:
Age Dental eruption
6 years 1
st
molars
6-8 yrs Upper and lower incisors
10 yrs 1
st
premolars and mandibular canines
11 yrs 2
nd
premolars and maxillary canines
12 yrs 2
nd
molars
Table 175: Summary of permanent tooth eruption timing

Dental eruption differences in patients age 8,9
At this age, patients should have the permanent first molars and all upper and
lower incisors.
Females
There were no significant differences between Mexican and Caucasian females of
8 and 9 years. However, a trend towards earlier eruption is evident for the Mexican
patients when comparing upper canines (13.3% of Mexican patients had at least one
upper canine erupted, 0% of Caucasian patients), lower bicuspids (26.7% of Mexican, 0%
of Caucasian patients), at least one upper and one lower bicuspids (13.3% of Mexican,
151
0% of Caucasian patients), and upper and lower second molars (6.7% of Mexican, 0% of
Caucasian patients). For all other tooth groups, the percentage of patients with erupted
teeth was similar between both ethnic groups.
Males
There were no significant differences between Mexican and Caucasian males of 8
and 9 years. Earlier eruption was seen in Mexican patients for several tooth groups;
upper bicuspids (25.0% of Mexican, 0% of Caucasian), lower bicuspids (12.5% of
Mexican, 0% of Caucasian), and at least one upper and one lower bicuspid (12.5% of
Mexican, 0% of Caucasian). All other tooth groups were unerupted for both ethnic
groups.

Dental eruption differences in patients age 10
At this age, patients should have the permanent first molars, all upper and lower
incisors, all first premolars and the mandibular canines.
Females
Significant differences appear in 10-year-old female group. All tooth groups
evaluated erupt earlier in the Mexican population than in the Caucasian. At this age 63%
of Mexican females had erupted upper canines, compared to only 25.9% of Caucasians
(p=.006). Earlier eruption in the Mexican population is also seen for all other tooth
groups: lower canines (p=.014), upper bicuspids (p=0.00), lower bicuspids (p=0.00), any
upper and any lower bicuspids (p=0.00), upper second molars (p=0.05), and lower second
molars (p=0.014).

152
Males
For males of age ten significant differences exist, with Mexicans presenting with
earlier eruption, for the following tooth groups: upper bicuspids (p=.001), lower
bicuspids (p=0.00), and any upper and any lower bicuspid (p=0.00). For all other tooth
groups Mexicans presented with more eruptions indicating a tendency towards earlier
eruption of canines and second molars, however no significant differences were present.

Dental eruption differences in patients age 11
At this age, patients should have the permanent first molars, all upper and lower
incisors, all first premolars, all second premolars and all canines.
Females
Mexican females of age 11 presented with significant earlier eruption in all tooth
groups, except for the upper second molars (p=0.221). At this age 76.6% of Mexicans
had at least one upper canine, compared to 54.1% of Caucasians (p=0.005). The same is
evident for all other tooth groups; lower canines (p=0.024), upper bicuspids (p=0.00),
lower bicuspids (p=0.00), any upper and any lower bicuspid (p=0.00), and lower second
molars (p=0.002).
Males
For 11-year-old males significant differences exist for lower canines, with 84.1%
of Mexicans presenting with erupted canines compared to 70.0% of Caucasians
(p=0.049). For all three bicuspid groups (upper, lower and any upper and any lower) and
for upper second molars, p=0.00, indicating earlier eruption for Mexican patients. A
significant difference also exists for lower second molars with 49.2% of Mexican patients
153
presenting with eruptions, compared to 20% of Caucasian patients (p=0.001). The only
tooth group that does not present a significant difference is upper canines group
(p=0.056).
Dental eruption differences in patients age 12
At this age, patients should have the permanent first molars, all upper and lower
incisors, all first premolars, all second premolars, all canines and all second molars.
Females
Significant differences exist for 12-year-old females, with Mexican patients
presenting with earlier eruption, in the following tooth groups: upper bicuspids
(p=0.003), lower bicuspids (p=0.006), at least one upper and one lower bicuspid
(p=0.001), and upper second molars (p=0.022). No significant differences exist for the
remaining tooth groups.
Males
Significant differences exist for 12-year-old males, with Mexican patients
presenting with earlier eruption, in the following tooth groups: upper canines (p=0.00),
upper bicuspids, lower bicuspids, and at least one upper and one lower bicuspids (all
p=0.00), upper second molars (p=0.018) and finally, lower second molars (p=0.006). No
significant differences exist for the lower canines.
Gender comparison
There was no significant difference in eruption timing between Mexican males
and females of any age group. However, more eruptions were present in the female
sample than in the male sample for any age group. The following is a summary of the
results.
154
Table 176: Results summary
Sex Age Tooth group P value
F 8,9 U canines .172
L canines .978
U premolars .099
L premolars .044
U/L premolars .044
U 2
nd
molars .343
L 2
nd
molars .343
M 8,9 U canines n//a
L canines n/a
U premolars .155
L premolars .333
U/L premolars .333
U 2
nd
molars n/a
L 2
nd
molars n/a
F 10 U canines .006
L canines .013
U premolars .000
L premolars .000
U/L premolars .000
U 2
nd
molars .005
L 2
nd
molars .013
M 10 U canines .753
L canines .375
U premolars .001
L premolars .000
U/L premolars .000
U 2
nd
molars .381
L 2
nd
molars .120
F 11 U canines .006
L canines .028
U premolars .000
L premolars .000
U/L premolars .000
U 2
nd
molars .342
L 2
nd
molars .003
M 11 U canines .077
L canines .062
U premolars .000
L premolars .000
U/L premolars .000
U 2
nd
molars .000
L 2
nd
molars .001
F 12 U canines .158
L canines .380
U premolars .003
L premolars .005
U/L premolars .001
U 2
nd
molars .022
L 2
nd
molars .073
M 12 U canines .000
L canines .157
U premolars .000
L premolars .000
U/L premolars .000
U 2
nd
molars .018
L 2
nd
molars .006
*Numbers in red indicate a significant difference.

155
The results of the present study can be compared to those from a previous study
that evaluated the difference between Caucasian and Hispanic patients in the Los Angeles
area.[43] In the present study, the data from the same Caucasian sample used previously
by Kennedy, was compared statistically to the data pertaining a Mexican sample of
patients from a different geographical location, Mexico City. The same data collection
process was used for both studies, patients were age-matched and the same tooth groups
evaluated.
In Kennedy’s study, significant differences were evident in females by age 8,9.
At this age, Hispanic females presented with significantly more upper canine eruptions.
In our study, lower premolars erupted significantly earlier in Mexican females. No
significant differences were found for male patients age 8,9 in either study.
According to Kennedy, 10 year old Hispanic females presented with significantly
earlier eruption in all tooth groups except for the lower second molars. In our study, all
tooth groups erupted significantly earlier in Mexican females. No significant differences
were found between Caucasian and Hispanic 10 year old males in the previous study.
However, in the present study, upper and lower premolars were found to erupt
significantly earlier in Mexican patients, when compared to Caucasian patients.

156
In the present study, 11 year old Mexican females presented with significantly
earlier eruption of all tooth groups except for the upper second molars. In Kennedy’s
study all tooth groups erupted significantly earlier in Hispanic females. In the case of 11
year old males, in our study Mexicans presented with significantly earlier eruption of all
tooth groups except for the canines. In the previous study, Hispanic males presented with
significantly earlier eruption of all tooth groups except for the lower canines and
premolars.
All tooth groups except lower canines were found to erupt significantly earlier in
12 year old Hispanic females from the previous study. In the present study, premolars
and upper second molars were found to erupt significantly earlier in the Mexican sample.
As for 12 year old males, canines and bicuspids erupted significantly earlier in Hispanics.
All tooth groups except for lower canines erupted significantly earlier in the Mexican
sample.
Although some differences exist in the results of these two studies, the general
trend of earlier dental development in the Hispanic sample is observed. This
phenomenon of earlier maturation in the Hispanic population has also been widely
reported when evaluating physical and sexual development. In a study by Sun et al [22]
the authors reported a trend toward earlier maturation over a period of 30 years in
Mexican American boys and girls. In another study by Wu et al, it was reported that
Black and Mexican American girls developed earlier and achieved menarche at an earlier
age when compared with Caucasian girls.[8] The mean ages of onset of puberty were
12.2 and 12.7 years of age for Mexican Americans and Caucasians respectively and the
ethnic differences remained after adjustment for body mass index and various economic
157
and social variables. The study concluded that Black girls enter puberty first followed by
Mexican American and Caucasian girls. Chumlea et al. also reported similar results;
African American girls reach menarche earlier, followed by Mexican girls and lastly,
Caucasian girls.[9]
Studies have linked positively sexual maturation to dental development. In a
study published by Agarwal et al, the eruption of teeth was significantly positively related
to height, weight and sexual maturity.[10] Another study reported that there is a
correlation of stature and body weight and the eruption of permanent teeth with sexual
maturity criteria in females. With respect to the selected criteria, those who reached
sexual maturity earlier were significantly taller and heavier and had significantly more
erupted permanent teeth than those who reach sexual maturity later.[19] The opposite,
no correlation between sexual maturity and dental development, has also been reported.
In an earlier study, Filipsson et al. reported a low correlation between dental maturity and
the different measures of sexual development, i.e. the age at menarche, the ages at breast
and pubic hair development, and the age of peak height velocity. [20]
Demirjian also reported that the age at which French-Canadian show advanced
dental development showed no significant relationships with the other maturity indicators
considered (i.e. menarche, peak height velocity, skeletal maturity and appearance of the
ulnar sesamoid.[21] Based on those results the authors concluded that the mechanisms
controlling dental development are independent of sexual maturity.

158
In a study by Anderson et al. dental development related more strongly to
morphological development than to skeletal development in both sexes.[7] Also, skeletal
age and body size related most strongly to late stages of tooth formation. It was also
determined that in males skeletal and dental mineralization were more closely related to
height than weight; the opposite is true for females.
The correlation of sexual maturation with dental development might be a possible
explanation to the observed results of the present study. As previously mentioned it has
been reported that Hispanics, and more specifically Mexicans, start sexual development
earlier than do Caucasians. As Irwin mentions in an article in the Journal of Adolescent
Health, it is now evident that sexual maturation occurs earlier in Mexican females as well
as males, when compared to Caucasians.[23] It is therefore expected that Mexicans
would present with a more advanced dental development, and earlier dental eruption than
their Caucasian counterparts of the same age group. In our study, this trend is evident for
all age groups and for all tooth groups. All measured tooth groups erupted earlier in
Mexican patients, and in no instance the opposite was observed. Although the results of
this study are not exact with the results obtained by Kennedy, the same trend of earlier
dental maturation in Hispanic patients was documented.
The differences found between the two studies can be attributed to various
factors. Although the same Caucasian data was used for both studies, this data was
compared to two different populations. In Kennedy’s study, the Caucasian data was
compared to a sample of patients, comprised of a mix of all Hispanic nationalities, that
was compiled in the Los Angeles area. In the present study, the Caucasian data from
patients in the Los Angeles area was compared to data gathered for Mexican patients
159
from Mexico City. The difference in the observed results can therefore be explained by
the fact that the same sample of Caucasian patients was compared to two compositionally
different populations. Both comparison populations are of Hispanic ethnicity, however
our study only considered Mexican patients from Mexico City, rather than a mixed
sample of Hispanics. Any Hispanic sample from Los Angeles will be most likely
composed primarily of Mexican patients based on the fact that that is the largest Hispanic
group present in the area.[5] Nonetheless, it is possible that the Mexican patients in that
sample are not from the Mexico City area, but from other localities in Mexico.
It is also possible that different results were obtained in both studies due to
inherent differences in the populations. Tooth eruption is

a complex process that involves
the timely action and interaction

of cells of the dental enamel organ, follicle, and
osteoclasts and osteoblasts in the alveolus. Many articles have been published on the
biology of the eruptive process but

the precise relationship of molecules involved in
signaling

cascades has not been completely elucidated. As an example, there are over 20
different known human syndromic conditions that involve

disruptions in the eruption
process but the genetic mutation is only known for half of those. [48] It is possible that
the timing of normal dental eruption for different populations is also genetically affected
in a non-detrimental fashion.
Dental eruption has also been linked to several socio-economic factors. Glick, in
the Journal of the American Dental Association in 2005, mentioned that with the advent
of better dental care and the wider availability of these services to the general public, the
primary dentition is retained longer and therefore permanent tooth eruption is delayed.
[49] A possible explanation to the finding of the present study is that health and dental
160
care are different and not equally available to the two study populations. Our study
sample was selected from two different populations, Caucasian patients from Los
Angeles and Mexican patients from Mexico City. Based on Glick’s statement and an
article by Beltran et al, the possibility exists that the eruption patterns observed in the
present study are a reflection of the different diets, dental and health care of the two
populations.
Both study populations present different genetic compositions, different
influencing environmental factors, exposure to different dietary factors, and different
dental care. An important consideration is that tooth loss is more common among those
with less education and less income and this could be another contributing factor to the
observed results of this present study. [49, 50]Caucasian patients in this study might have
received better dental education and care from an earlier age, maintaining the integrity of
the primary dentition and thus, retaining it longer.
Another interesting factor to consider is the possibility that a correlation exists
between weight and sexual maturation, and therefore weight and dental development. It
has been extensively reported that Mexican adolescents are generally more overweight,
and present a higher BMI, than do Caucasian adolescents.[27, 28] It is reasonable to
consider that this affects dental development and that it would be one reason why earlier
dental eruption is observed in the Mexican population. However, an extensive study
conducted by Karpati et. al, using the US National Health and Nutrition Examination
Survey, indicated that there is no relationship between a higher BMI and earlier sexual
maturation.[29]

161
In addition, most of the reported studies on increased BMI in Mexicans are based
on people living currently in the United States and do not consider Mexico residents, who
might be exposed to different influencing factors.
Sexual dimorphism in the eruption of permanent teeth has been described in the
literature. In a longitudinal study, Holman and Jones found sexual differences for three
of their study populations and described a crossover pattern in which males lead females
in the anterior dentition and females lead males in the posterior dentition.[30] The same
pattern of sexual dimorphism was also described by Demirjian in 1980 for a genetically
homogeneous French-Canadian group of children.[31] Nizam in 2003 reported that the
median age of eruption of each tooth was earlier in girls than in boys and all mandibular
teeth, with the exception of first and second bicuspids in both males and females, tended
to erupt earlier than their maxillary counterparts. Leroy in 2003 determined that there are
significantly earlier emergence ages in girls than in boys.[33] Hägg and Taranger
reported that throughout the permanent dentition, girls are consistently ahead of boys.[34]
In another study designed to described the chronology of permanent tooth eruption in
Argentinean children it was found that all teeth emerged earlier in girls.[35] Moslemi in
2004, defined the average time of eruption of permanent teeth, the range of variation for
each tooth and the sequence of eruption for boys and girls in Iran.[36] The findings of
this study were that the average age of eruption of permanent teeth in girls is less than in
boys. Also, mandibular teeth have earlier eruption timing than maxillary teeth in both
boys and girls and lastly, that amongst girls maxillary canines erupt earlier than maxillary
second premolars.
162
Sexual differences were observed in our study, however those differences were
not significant. As reported previously in the literature, teeth generally erupt earlier in
females than in males, and significant differences start showing between females of both
ethnic groups earlier than in males. These findings are in agreement with previous
reports.

163
CHAPTER 8: SUMMARY

Orthodontist frequently design evaluation and recall visit schedules based on
initial diagnosis, and skeletal and dental development guidelines. The present guidelines
are used by practitioners in order to make treatment decisions, and also for public
information on when to schedule the first visit to an orthodontist. Many treatment
decisions, including initiation of treatment and growth modification, depend on the dental
development of the patients. Although standard guidelines for dental eruption timing
exist in the literature, differences exist when comparing ethnic groups. Numerous articles
have been published that ascertain earlier dental development for different ethnic groups
when compared with the Caucasian standards described in landmark orthodontic
textbooks. This study was undertaken to describe variances in eruption timing when
comparing Mexican patients with Caucasian patients and the current standards.
In the Los Angeles area, a large portion of the population is of Hispanic descent
and as of the year 2000, 32% of the total population of California is of Mexican ethnicity.
Any given orthodontic practice will evaluate patients of Mexican ethnicity on a regular
basis and recommendations should be tailored to each individual.
The findings of this study suggest that the tooth groups evaluated (canines,
bicuspids, and second molars) erupt earlier in Mexicans than they do in Caucasians.
Significant differences begin to appear by age ten in females and males, but tendencies
towards earlier eruption in Mexican patients are evident by age 8. In no instance did
Caucasian patients present with more eruptions than Mexican patients. Discrepancies
persist until age 12 for most tooth groups in both sexes. Sexual dimorphism is also
164
present; Mexican female patients generally are more dentally advanced that their male
counterparts.
The implications of this study are several. Understanding ethnic differences in
dental development and eruption timing is critical for accurate assessment and diagnosis
in orthodontics; many treatment decisions rely on the stage of dental development of the
patient. Early orthodontic treatment in the mixed dentition is geared towards assuring
timely eruption of the permanent dentition as well as intervention for various skeletal
problems. Practitioners who see a large number of Mexican patients should be aware of
the earlier dental development presented by these patients and possibly start certain
treatment modalities earlier than they would for Caucasian patients.
This information is pertinent for pediatric dentists who can treat the permanent
dentition earlier with preventive measures. Also, recommendations for the first
orthodontic encounter for the general public should be made based on the most accurate
information available and these recommendations tailored to different ethnic groups. In
the case of the Mexican population, a recommendation should be made by the pediatric
dentist to visit the orthodontist earlier who in turn should consider the patient’s
background when making treatment decisions.
Most orthodontic practitioners prescribe full orthodontic appliances after patients
have the entire permanent dentition. In the case of Mexican patients, this could be as
early as 10-years-old. For Caucasian patients, full orthodontic treatment usually cannot
start before age 12.
165
The results of this study should be used strictly as guidelines and orthodontic
treatment should be prescribed and designed after careful clinical evaluation of each
individual patient.

166
CHAPTER 9: CONCLUSIONS
1. For all ages, Mexican patients presented with more eruptions in all tooth groups,
than Caucasian patients.
2. For eight and nine year old females, the only significant difference was in lower
premolar eruption. This tooth group erupts significantly earlier in Mexican
patients. A trend towards earlier eruption in Mexican patients was evident for
both male and female patients.
3. For ten year old females, all tooth groups erupted significantly earlier in Mexican
females. For ten-year-old males, bicuspids erupted earlier in the Mexican
patients.
4. Mexican females of age 11 presented with significant earlier eruption in all tooth
groups, except for the upper second molars. Mexican males of age 11 presented
with significant earlier eruption in all tooth groups, except for the canines.
5. Mexican females of age 12 presented with significant earlier eruption of bicuspids
and upper second molars. Mexican males of age 12 presented with significant
earlier eruption of all tooth groups except lower canines.
6. Sexual dimorphism was not significant, however, a trend towards earlier eruption
was seen in Mexican females.
7. Significant differences start showing earlier than in a previous study by Kennedy,
where the eruption timing between Caucasians and Hispanics was compared.

167
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Abstract (if available)

Abstract The purpose of this study was to compare the eruption timing of the posterior permanent dentition in Mexican adolescents in reference to the current standards, and to determine if sexual dimorphism is present in the Mexican sample. 257 consecutive records were obtained from a university orthodontic program in Mexico City using established criteria. The eruption of the posterior secondary dentition was recorded for subjects from 8 to 12 years of age, and the data compared statistically to the Caucasian data from a previous study. Significant differences in eruption timing start showing in 8 year old females (p=.044, lower premolars) and 10-year-old males (p=.001, upper bicuspids). For all age groups, the posterior permanent dentition erupts earlier in Mexican patients. For the Mexican sample, evidence of sexual differences in eruption timing was present by age 10, however differences were not statistically significant. Effective diagnosis and treatment planning for patients of Mexican heritage may require assessment at an earlier age.

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Asset Metadata

Creator Rojas, Jenniffer (author)

Core Title Sexual differences and early eruption timing of the permanent dentition in Mexican adolescents- a comparison with the Caucasian standards

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Degree Conferral Date 2008-05

Publication Date 03/06/2008

Defense Date 02/11/2008

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag eruption timing,OAI-PMH Harvest

Place Name Mexico (countries), Mexico City (city or populated place)

Language English

Advisor Sameshima, Glenn T. (committee chair), Moon, Holly (committee member), Paine, Michael (committee member)

Creator Email jenniffr@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1045

Unique identifier UC1135330

Identifier etd-Rojas-20080306 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-23896 (legacy record id),usctheses-m1045 (legacy record id)

Legacy Identifier etd-Rojas-20080306.pdf

Dmrecord 23896

Document Type Thesis

Rights Rojas, Jenniffer

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu