University of Southern California Dissertations and Theses

A cone beam-ct evaluation of the availability of bone for the placement of miniscrews

(USC Thesis Other)

A cone beam-ct evaluation of the availability of bone for the placement of miniscrews

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content

A CONE BEAM-CT EVALUATION OF THE AVAILABILITY

OF BONE FOR THE PLACEMENT OF MINISCREWS

by

Sharon Mia Kim

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 Sharon Mia Kim

DEDICATION

To my family and friends who have kept me going.

ii

ACKNOWLEDGEMENTS
A special thank you to:
Dr. Glenn Sameshima
Dr. Holly Moon
Dr. Michael Paine
My Co-Residents
Zheng Chen

iii

TABLE OF CONTENTS

Dedication ii

Acknowledgements iii

List of Tables v

List of Figures vii

Abstract x

Chapter 1: Introduction 1

Chapter 2: Review of Literature 4

Chapter 3: Hypothesis 40

Chapter 4: Materials and Methods 42

Chapter 5: Results 50

Chapter 6: Discussion 93

Chapter 7: Assumptions 98

Chapter 8: Limitations 99

Chapter 9: Summary 100

Chapter 10: Conclusions 101
Bibliography 103

iv

LIST OF TABLES

TABLE 1: Space Available categories 48
TABLE 2: Frequency distribution of space available category by site 52
TABLE 3: Space available category by ethnicity, Site 1 54
TABLE 4: Space available category by ethnicity, Site 2 55
TABLE 5: Space available category by ethnicity, Site 3 56
TABLE 6: Space available category by ethnicity, Site 4 57
TABLE 7: Space available category by ethnicity, Site 5 58
TABLE 8: Space available category by ethnicity, Site 6 59
TABLE 9: Space available category by ethnicity, Site 7 60
TABLE 10: Space available category by ethnicity, Site 8 61
TABLE 11: Space available category by ethnicity, Site 9 62
TABLE 12: Space available category by ethnicity, Site 10 63
TABLE 13: Space available category by ethnicity, Site 11 64
TABLE 14: Space available category by ethnicity, Site 12 65
TABLE 15: Space available category by ethnicity, Site 13 66
TABLE 16: Space available category by ethnicity, Site 14 67
TABLE 17: Space available category by ethnicity, Site 15 68
TABLE 18: Space available category by ethnicity, Site 16 69
TABLE 19: Space available category by ethnicity, Site 17 70
TABLE 20: Space available category by ethnicity, Site 18 71
TABLE 21: Space available category by gender, Site 1 73
v

TABLE 22: Space available category by gender, Site 2 74
TABLE 23: Space available category by gender, Site 3 75
TABLE 24: Space available category by gender, Site 4 76
TABLE 25: Space available category by gender, Site 5 77
TABLE 26: Space available category by gender, Site 6 78
TABLE 27: Space available category by gender, Site 7 79
TABLE 28: Space available category by gender, Site 8 80
TABLE 29: Space available category by gender, Site 9 81
TABLE 30: Space available category by gender, Site 10 82
TABLE 31: Space available category by gender, Site 11 83
TABLE 32: Space available category by gender, Site 12 84
TABLE 33: Space available category by gender, Site 13 85
TABLE 34: Space available category by gender, Site 14 86
TABLE 35: Space available category by gender, Site 15 87
TABLE 36: Space available category by gender, Site 16 88
TABLE 37: Space available category by gender, Site 17 89
TABLE 38: Space available category by gender, Site 18 90
vi

LIST OF FIGURES

FIGURE 1: Schematic diagram of the 18 sites evaluated 44
FIGURE 2: Schematic diagram of the horizontal and vertical 44
measurements made

FIGURE 3: Original volume rendering of patient 45
FIGURE 4: Cut tool used to remove extraneous structures 45
FIGURE 5: Alignment of volume section 46
FIGURE 6: Example of horizontal and vertical measurements made 46
FIGURE 7: Example of space always available 47
FIGURE 8: Example of space available at a vertical distance 47
FIGURE 9: Example of space never available 48
FIGURE 10: Space available category by ethnicity, Site 1 54
FIGURE 11: Space available category by ethnicity, Site 2 55
FIGURE 12: Space available category by ethnicity, Site 3 56
FIGURE 13: Space available category by ethnicity, Site 4 57
FIGURE 14: Space available category by ethnicity, Site 5 58
FIGURE 15: Space available category by ethnicity, Site 6 59
FIGURE 16: Space available category by ethnicity, Site 7 60
FIGURE 17: Space available category by ethnicity, Site 8 61
FIGURE 18: Space available category by ethnicity, Site 9 62
FIGURE 19: Space available category by ethnicity, Site 10 63
vii

FIGURE 20: Space available category by ethnicity, Site 11 64
FIGURE 21: Space available category by ethnicity, Site 12 65
FIGURE 22: Space available category by ethnicity, Site 13 66
FIGURE 23: Space available category by ethnicity, Site 14 67
FIGURE 24: Space available category by ethnicity, Site 15 68
FIGURE 25: Space available category by ethnicity, Site 16 69
FIGURE 26: Space available category by ethnicity, Site 17 70
FIGURE 27: Space available category by ethnicity, Site 18 71
FIGURE 28: Space available category by gender, Site 1 73
FIGURE 29: Space available category by gender, Site 2 74
FIGURE 30: Space available category by gender, Site 3 75
FIGURE 31: Space available category by gender, Site 4 76
FIGURE 32: Space available category by gender, Site 5 77
FIGURE 33: Space available category by gender, Site 6 78
FIGURE 34: Space available category by gender, Site 7 79
FIGURE 35: Space available category by gender, Site 8 80
FIGURE 36: Space available category by gender, Site 9 81
FIGURE 37: Space available category by gender, Site 10 82
FIGURE 38: Space available category by gender, Site 11 83
FIGURE 39: Space available category by gender, Site 12 84
FIGURE 40: Space available category by gender, Site 13 85
viii

FIGURE 41: Space available category by gender, Site 14 86
FIGURE 42: Space available category by gender, Site 15 87
FIGURE 43: Space available category by gender, Site 16 88
FIGURE 44: Space available category by gender, Site 17 89
FIGURE 45: Space available category by gender, Site 18 90
FIGURE 46: Least Squares Means for Space Available Category 92

ix

ABSTRACT

Introduction: The purpose of this study was to determine the most coronally
located interradicular sites for miniscrew placement, and to compare gender, ethnic
and insertion site groups. Methods: CBCT images from 60 patients were rendered
using InVivo Dental
TM
Software. A vertical measurement was recorded from the
most coronal presence of 3 mm of interradicular space to a horizontal line connecting
the CEJs of adjacent teeth at 18 sites. Results: No significant differences were found
between the right and left sides of the mouth. Statistically significant differences (p
< .0001) existed between sites, and upper vs. lower sites. Statistically significant
differences between gender and ethnic groups existed between lower left bicuspids
and lower right molars. Conclusion: Sufficient bone for placement of miniscrews
through attached gingiva existed primarily between mandibular molars. Sites mesial
to mandibular and maxillary molars had bone stock located further apically, which
would make miniscrew placement through attached gingiva unlikely.

x

Chapter 1: INTRODUCTION
Miniscrews for orthodontic anchorage are now widely accepted and are
revolutionizing the way orthodontists treat their patients. They are rapidly gaining
popularity as temporary anchorage devices (TADs) because they provide an
operator-friendly, low cost means of achieving absolute anchorage without
dependence upon patient compliance. Advantages of this system include ease of
insertion and removal of the screws, immediate/early loading, low cost, adequate
anchorage support for orthodontic tooth movement, and versatility in intraoral
placement.
An abundance of recent literature on the subject of miniscrews can be
attributed to their wide acceptance over the past decade. Much research has focused
on providing guidelines for the safe placement of miniscrews by locating
interradicular sites with sufficient space to avoid damage to adjacent teeth, regardless
of whether or not these sites were located in attached gingiva or movable mucosa.
Because soft tissue irritation is the most frequently cited clinical complication and is
highly correlated with miniscrew failure, it is advantageous for these miniscrews to
be placed in attached mucosa.
[1]
It is crucial to determine whether sufficient bone
stock for miniscrew placement exists at the level of attached gingiva, because soft
tissue irritation, infection, and premature loosening of the screw are greatly reduced
when miniscrews are placed through attached gingiva
In 2004, Schnelle et al.
[1]
conducted a study on panoramic radiographs to
determine if sufficient interradicular divergence for miniscrew placement exists at
1

the level of the buccal mucogingival junction. They concluded that sites with
sufficient bone stock for miniscrew placement existed at 9 of 14 sites they
investigated around the mouth (bone stock is a term used to indicate the amount of
bone available for implant insertion). They defined sufficient bone stock for
miniscrew placement as 3 and 4 mm of interradicular space to allow for a minimum
of 1 mm of bone on either side of the miniscrew. They stated that sufficient bone
stock for miniscrew placement existed mesial to the maxillary 1
st
molars and mesial
and distal to the mandibular 1
st
molars. Of these, they believed the only site likely to
have bone stock available in areas of attached gingiva was distal to the mandibular
first molars. Their study provided important initial guidelines in the evaluation of
bone stock availability within attached gingiva. However, they evaluated panoramic
radiographs in which distortion and magnification error is inherent.
In order to determine which interradicular sites had enough space for
miniscrew placement in regions that would likely be covered with attached gingiva,
CBCT data of 60 patients from an archival database at the University of Southern
California, Department of Orthodontics was analyzed, using methods similar to the
ones presented by Schnelle, et al. This study utilized data acquired from the
NewTom (DVT9000) Volume Scanner QRsr1 Verona CBCT, which provides
dimensionally accurate 1:1 images that are not subject to the distortion seen in
traditional digital panoramic radiographs. By presenting this data, this study will
help identify buccal alveolar miniscrew insertion sites that would allow optimum
screw insertion through attached gingiva.
2

Purpose of the Study
- Locate interradicular sites with sufficient room for miniscrew placement and
determine which of these are likely to be located in areas of attached gingiva.
- Determine whether significant differences exist between ethnic (Hispanics
and Caucasians) and gender groups.
- Determine whether significant differences exist between left and right and
upper and lower sites.

3

Chapter 2: REVIEW OF THE LITERATURE
Orthodontic Anchorage Needs and the Development of Skeletal Anchorage
Orthodontic anchorage, defined as the resistance to unwanted tooth
movement, has been long understood by orthodontists as the key to successful
treatment. Clinical orthodontics and satisfactory treatment results are dependent
upon the availability and control of anchorage. According to Newton’s third law, for
every action, there is an equal and opposite reaction. This means that, inevitably,
other teeth move if the orthodontic appliance engages them. Anchorage is the source
of resistance to the forces generated by the active components of an appliance which
are provided by other teeth or devices.
[2-4]
Therefore, orthodontic treatment planning
entails understanding anchorage concerns and accounting for them. As stated by
Proffit, “it is simply not possible to consider only the teeth whose movement is
desired. Reciprocal effects throughout the dental arches must be carefully analyzed,
evaluated, and controlled. An important aspect of treatment is maximizing the tooth
movement that is desired, while minimizing undesirable side effects.”
[2, 5]
In the orthodontic movement of teeth, groups or segments of teeth are used as
anchors to resist movement and pull other teeth into their desired position. Anchor
segments usually include more teeth or more root surface area than the moving
segment.
[2, 6]
Often, complex orthodontic cases have anchorage requirements that are
difficult to satisfy. Additionally, an increasing number of adult patients and patients
with compromised dentitions, e.g. the partially edentulous patient or periodontally

4

compromised patient, are seeking orthodontic treatment, prompting the need for a
means to supplement anchorage in patients without adequate dentitions for
orthodontic anchorage.
[2, 7]

The role of anchorage in orthodontic treatment was appreciated early on, as
prominent orthodontists such as Angle realized the limitations of moving teeth
against other teeth used for anchorage.
[8]
He initially described anchorage as
intraoral, extraoral, simple, stationary, reciprocal, or intermaxillary. Giannelly and
Goldman
[9]
quantified the amount of movement to be expected of the active and
reactive units and described anchorage needs as “minimum”, “moderate”, and
“maximum”. In 1990, Marcotte defined three categories of anchorage in extraction
cases: Group A—maintenance of posterior tooth position during anterior retraction,
Group B—reciprocal space closure, and Group C—maintenance of anterior tooth
position during posterior protraction.
[3, 10]
Regardless of its classification, the importance of anchorage control led
orthodontists to develop various extra-oral devices to reinforce anchorage.
[10]

Headgear, intermaxillary elastics, and other extra-oral devices were all developed to
control anchorage, but require excellent cooperation from the patient. In patients
who fail to comply, anchorage demands may not be met, and result in treatment
outcomes which are compromised.
In order to meet anchorage demands without relying on patient compliance,
orthodontists have searched for an alternative and effective means of providing the
anchorage necessary to treat a case without the typical constraints of moving teeth
5

against other teeth. Skeletal anchorage provided the solution in the search for
absolute or infinite anchorage in which zero anchorage loss is possible.
Clinicians and researchers have tried to use implants as orthodontic
anchorage units for over a half century. The earliest attempts at achieving skeletal
anchorage were documented in 1945, when Gainsforth and Higley placed vitallium
screws placed in dog mandibles and applied orthodontic forces with elastics. All the
screws failed within 16 to 31 days.
[2, 8]
In 1964, Branemark discovered the
biocompatibility of titanium screws in bone tissue. He observed firm anchorage of
titanium to bone with no adverse tissue response, as well as bone-to-implant contact
with light microscopy. From this, he developed the concept of “osseointegration”.
[2]

Titanium implants soon became the focus of much research in the dental field, and
orthodontists began taking an interest in the potential of using implants for providing
orthodontic anchorage for moving teeth.
In 1969, Linkow successfully placed mandibular blade implants as anchors
for class II elastics for retraction of maxillary incisors.
[2, 11]
Then in 1984, Roberts et
al
[4]
documented the successful loading of orthodontic force on titanium screws
placed in rabbit femurs. The screws remained stable and developed osseous contact.
His results proved that titanium implants could be used as skeletal anchorage for
orthodontics and led to the successful use of dental implants for skeletal anchorage.
Despite the advantages of using traditional dental implants as a source of
absolute anchorage for orthodontics, its disadvantages are many: they can only be
placed in limited areas, they are limited in the direction of force they can apply,
6

they require more invasive surgery for placement, healing time to allow for
osseointegration is usually advocated, they are expensive, and limited in placement
sites.
[2, 12]
It is not a viable option in the majority of orthodontic patients who do not
have edentulous spaces in which to place implants. Therefore, the placement of
endosseous implants for orthodontic anchorage is indicated when edentulous spaces
exist and when prosthodontic replacement of missing teeth will complete the
treatment. In 1988, Shapiro and Kokich
[13]
stressed that such treatment requires
careful multidisciplinary treatment planning in order to be successful because the
implant must be placed in the desired final position.
[6]
Palatal implants were
developed soon after to reinforce anchorage in patients not requiring endosseous
dental implants. However, palatal implants still require a difficult and more
traumatic surgical procedure for both placement and removal.
[2, 6]

The search for cost effective, compliance free and less invasive forms of
anchorage brought orthodontists to the use of titanium screws, originally used for
fixation in orthognathic surgery. In the 1970’s, Brons and Boering introduced the
use of lag screws for orthognathic fixation. By 1984, miniaturized titanium bone
screws, 2.0 mm in diameter, were being used as the sole source of fixation. These
small screws used in orthognathic fixation laid the groundwork for the successful
development of orthodontic mini screws as temporary anchorage devices.
[14]
In
1997, Kanomi
[12]
described a mini-implant specifically made for orthodontic use, and
in 1998, Costa et al
[15]
presented a miniscrew with a bracket head for orthodontic
anchorage. Over the past decade, many different miniscrew designs have been
7

proposed by clinicians from all over the world.
[8]

Temporary anchorage devices, or TADs, have become the current focus of
research in the search for absolute anchorage. A TAD is a device that is temporarily
fixed to bone for the purpose of enhancing orthodontic anchorage, and is removed
after use. To classify what constitutes temporary anchorage, Cope described the
available methods for skeletal anchorage as either biological or biocompatible.
[8]

The biological category includes ankylosed and dilacerated teeth. The biocompatible
group includes all forms of temporary anchorage devices, and is further subdivided
into biochemical (osseointegrated) and mechanical (cortically stabilized) groups,
based upon how the anchorage device attaches to bone. Osseointegrated devices
include dental, palatal or retromolar implants as well as onplants. Devices which
rely upon mechanical retention and are temporarily retained include miniscrews and
miniplates.
[14]

Miniscrews have gained tremendous popularity over the past decade. The
recent rise in popularity of miniscrews as TADs can be attributed to their ease of
insertion, ability to be immediately loaded, relative patient comfort, ease of removal,
and versatility in usage.
[8]
In recent years, the use of miniscrews has been heavily
investigated in vitro and in vivo. This barrage of research information has increased
clinician and patient acceptance. The integration of skeletal anchorage, particularly
that provided by miniscrews, offers a cost efficient way of increasing orthodontic
anchorage, eliminating reliance upon patient compliance with extraoral anchorage
devices, decreasing treatment time, and occasionally permitting orthodontic
8

treatments that were previously thought impossible without the aid of surgery.
[6]

The use of miniscrews and skeletal anchorage, has created a paradigm shift in the
understanding of which cases can or cannot be treated orthodontically.
Celenza and Hochman described two different forms of anchorage that can be
provided by skeletal anchorage: direct and indirect anchorage. In direct anchorage,
the segment of teeth to be moved is directly connected to the miniscrew or implant
which acts as the anchor to the reactive force. In indirect anchorage, the miniscrew
or implant is anchored through bars or wires to a segment of teeth that is to remain
stationary, thereby enhancing their anchorage. Then the segment to be moved is
connected to the anchored segment.
[6]
Miniscrews offer a huge advantage by their
ability to easily be adapted to either form of anchorage.
Orthodontic miniscrews are made of medical type IV or type V titanium and
range from 1.2-2 mm in diameter and 4-14 mm in length.
[2]
Their diminutive size
has made them ideal for placement in the maxilla and mandible, even in
interradicular spaces. Histologic studies have revealed that miniscrews do not
completely osseointegrate, making them easy to remove, while proving to be an
adequate source of absolute anchorage for orthodontic purposes. Because complete
osseointegration would be unfavorable, miniscrews are manufactured with a smooth
surface, thereby minimizing osseointegration.
Studies by Creekmore and Eklund, Melsen and Costa
[15, 16]
, as well as
Freudenthaler et al
[3]
and Ohmae
[17]
have found no statistical difference in the
success of miniscrews that were immediately loaded and those that were loaded
9

after a waiting period.
Over the past few years, the application of miniscrews has expanded
exponentially. It has been documented in assisting in the treatment of many difficult
cases, in a variety of situations. They are particularly useful in patients with
compromised dentitions, such as the partially edentulous patient or patients with
periodontally involved teeth.
[18]
Their use has been indicated for patients requiring
maximum anchorage, en-masse retraction of anterior teeth, upper and/or lower molar
distalization, molar uprighting, retraction or protraction of one arch, closure of
extraction spaces, asymmetric tooth movement, alignment of dental midlines,
intermaxillary anchorage for the correction of sagittal discrepancies, anchorage for
rapid palatal expansion in older patients, correction of single tooth crossbites,
correction of deep overbites, intrusion and extrusion of teeth, correction of occlusal
cants, and correction of other vertical skeletal discrepancies that would otherwise
require orthognathic surgery.
[6, 8]
Whether intruding posterior teeth to correct
anterior openbite, or intruding anterior teeth to correct VME, miniscrews are opening
new realms of possibility in orthodontic treatment and relieving the clinician from
their dependence on patient compliance which is often inadequate. Miniscrews have
demonstrated the ability to move individual teeth, groups of teeth, or even entire
arches without the compromising side effects on the reactive units.

10

Miniscrew Placement
Site selection
In order to locate the best site for miniscrew placement in each patient, the
type of orthodontic movement that is desired must first be determined.
Understanding the desired tooth movements to be accomplished will aid in
establishing a general location for insertion of the miniscrew. The miniscrew may be
placed in a location which will allow for direct anchorage, or may also be placed as a
means of indirect anchorage.
Possible sites for miniscrew implant placement in the maxilla include the area
below the nasal spine, the midpalate area, the infrazygomatic crest, and the
interproximal areas on the buccal and palatal alveolar process.
[8]
While maxillary
tuberosities were often recommended as a site for miniscrew insertion, a recent study
by Poggio et al
[19]
has indicated that the least amount of bone in the maxilla was
located in the tuberosity area. They found in 70% of the maxillae measured, the
sinus or impacted wisdom teeth were present in the tuberosity, thus explaining the
limited amount of bone in this area. Therefore it should no longer be considered as a
possible site for the insertion of a miniscrew.
Possible sites for miniscrew implant placement in the mandible include the
symphasis or parasymphasis, the retromolar area, and the interproximal areas on the
buccal alveolar process.
[8]
A study by Berens et al
[20]
indicated that the lingual
alveolar process in the mandible is an unfavorable site for miniscrew insertion.
11

To attain safe placement, the potential site must be evaluated for the
availability of sufficient bone, amount of space between adjacent teeth, and
avoidance of other vital structures such as the maxillary sinus, nerves, and vessels.
[3,
19, 21]
While a standard panoramic radiograph has been reported to be adequate for
safe placement in extra-alveolar sites, it is recommended that serial periapical
radiographs is taken prior to insertion of a miniscrew in the alveolar process.
[21]
The
introduction of cone beam computed tomography now allows precise evaluation of
the insertion site, however, results in increased radiation exposure to the patient. The
use of various brass wires or guide bars is recommended for an accurate evaluation
of the insertion site. These are placed prior to radiographic visualization of the area
and are retained during miniscrew insertion, which helps in the exact placement at
the desired location.
[21, 22]
If enough interradadicular space is not available, the roots
may be moved apart orthodontically prior to miniscrew insertion,
[21]
or, in extraction
cases, may be placed after the removal of teeth. In this case, while avoidance is not
as crucial as in the avoidance of adjacent roots, care should still be taken to avoid the
extraction socket to maintain stability of the miniscrew.
[3]

Recent studies involving miniscrew placement have attempted to identify
which sites in the mouth are optimum for miniscrew insertion.
[1, 19]
In 2004,
Schnelle et al
[1]
used panoramic radiographs to measure the vertical distance from
the CEJ to the location of adequate amount of bone for miniscrew placement. Using
the guideline of maintaining at least 1 mm of bone around the miniscrew, they
looked for sites in the mouth with 3 and 4 mm of space available between
12

adjacent roots, which they referred to as “bone stock”. They located sites with 3 mm
and 4 mm of “bone stock” available and then measured the vertical distance from
this location to the CEJ, in order to attempt to characterize which sites in the mouth
would allow miniscrew insertion through attached gingiva. They found that bone
stock for miniscrew placement existed primarily in the maxilla mesial to the first
molars and in the mandible both mesial and distal to the first molars. They also
postulated that bone stock availability was typically located too apical to allow for
miniscrew insertion through attached gingiva, with the possible exception of the area
distal to the mandibular first molars. Therefore, they concluded that design
modifications in the screw head of miniscrews or in placement techniques were
necessary to prevent the soft tissue irritation that would be caused by placement of
miniscrews in areas of unattached mucosa.
[1]

Carano et al
[23]
investigated optimal locations for miniscrew placement in the
maxilla, and concluded that the safest interradicular sites for miniscrew insertion
were the buccal and palatal locations between the canine and lateral incisors,
maxillary second bicuspid and first molar, and maxillary first and second molars.
However, they recommended caution in inserting miniscrews too high in the
vestibule in this area because of the presence of the maxillary sinus.
In 2006, Poggio et al
[19]
evaluated the mesiodistal and the buccolingual
dimensions of interradicular sites from the CBCT images of 21 subjects to identify
sites with adequate amounts of bone for miniscrew placement. According to their
study, sufficient interradicular space for the buccal placement of miniscrews in
13

the maxilla was available between the maxillary cuspid and first bicuspid and
maxillary first and second bicuspids. They suggested caution in the area between the
first molar and second bicuspid because of the presence of the maxillary sinus. In
the mandible, they found that the safest interproximal sites for miniscrew insertion
existed between the first and second bicuspids and between the first and second
molars.

Insertion Procedure
If it is decided that the placement of a miniscrew is necessary to achieve the
desired tooth movements on a patient, the treatment plan must be discussed with the
patient. The procedure for miniscrew placement should be explained to the patient
and any possible risks or complications should be described in detail. The patient
should be asked to read and sign a TAD consent form.
Once an adequate site for miniscrew insertion has been determined and the
patient has consented for TAD placement, the surgical placement of the miniscrew is
simple. A small amount of local anesthetic is infiltrated into the area of insertion.
While some protocols have indicated that topical anesthesia of the site is sufficient
for miniscrew insertion, patient comfort should be carefully monitored. Most
protocols insist that profound anesthesia of the tooth is contraindicated because the
tooth will only respond if the miniscrew or bone drill approaches their roots, in
which case they must be redirected away.
[21]
Patient sensitivity during insertion
should prompt the clinician to verify that the angle of insertion is correct and that
14

contact of an adjacent root is not the cause of sensitivity.
[21]

Prior to placement, the patient may rinse with chlorhexidine and/or the site of
insertion may be swabbed with betadine solution. Some protocols recommend a
small incision or soft tissue punch to be used prior to placement, particularly when
the screw must be placed in movable mucosa,
[21]
to prevent “wrapping” of the
mucosa around the screw as it is being inserted.
The procedure for insertion varies according to the type of miniscrew being
used. Currently, screws are either self tapping or self drilling. When placing self
tapping screws, an initial pilot hole must be drilled before screw insertion. While
this technique is helpful in areas with dense cortical bone, such as the mandible, it
increases the risk of iatrogenic damage to adjacent teeth and the potential for
overheating the surrounding bone. In order to decrease risks associated with pre-
drilling, it has been suggested to use drills operated at a slow speed.
[21]
While Kyung
et al suggested that self drilling systems increased the risk of iatrogenic damage to
adjacent roots because these screws could be drilled easily through roots,
[21]

proponents of self drilling systems insist that by eliminating the need for pre-drilling
it reduces the potential risk of iatrogenic damage to adjacent teeth, though it does not
eliminate the risk completely. Self drilling systems are usually placed with hand
drivers, allowing for operator tactile sensation and therefore the ability to sense
increased resistance if an adjacent root is being challenged. Self drilling systems
require careful and steady placement, without “wobble”
[24]
for good mechanical
retention required in successful placement. In studies comparing screw design
15

and self drilling versus self tapping screws, it has been determined that self drilling
screws and conical screws require greater insertion torque, which contributes to their
better primary stability.
[25, 26]
However, because of this increased amount of torque
necessary for placement of the screw in bone, self drilling systems are also
associated with a higher risk of screw breakage.
[25]
Therefore, it has been
recommended that a small pilot hole still be made in areas of dense cortical bone to
reduce the risk of screw fracture.
If a pilot hole is necessary, it should be made with a slow speed handpiece
with saline irrigation.
[21]
A depth gauge should be used on the bur to insure proper
depth is achieved. The diameter of the pilot hole should not exceed the diameter of
the miniscrew in order to achieve stability of the miniscrew. Whether a pilot hole is
being drilled or the minscrew itself is being placed, the clinician should visualize the
insertion angle from the occlusal surface with an intraoral mirror to ensure that the
direction of insertion avoids adjacent teeth and other vital structures. When the
miniscrew is being placed interproximally, the miniscrew should look as if it is being
inserted through the contact point of the teeth, and not toward either one of the
adjacent teeth.
During placement of the miniscrew, the clinician should take care to keep the
screw steady, and reduce the amount of “wobble” that occurs.
[24]
Any such eccentric
motion could result in a widening of the screw hole, reducing the amount of
mechanical retention and primary stability that is achieved. Because miniscrews
depend almost entirely on mechanical retention within the bone for their success,
16

they must have a tight fit to avoid jeopardizing their retention.
[21]
Absence of an
initial tight fit could in turn lead to instability of the miniscrew and eventual failure.
The screw is advanced into the bone until only the head remains out of the
tissue. Excessive force should never be used to insert the miniscrew or bone drill. If
the miniscrew touches the root of an adjacent tooth during insertion, the clinician
will detect a strong resistance during placement and the patient may complain of a
dull pain. In this situation, the miniscrew should be backed up and reinserted at a
different angle
[21]
. If the implant is not stable immediately following placement, it
should be removed and another site chosen for placement. Studies have indicated
that primary stability is the most important predictor of miniscrew success.
[27-29]

Therefore, it is unlikely that a screw without primary stability will become stable
over time. Deguchi et al
[27]
indicated that once an implant was rigidly fixed within
supporting bone, or that primary stability was attained, orthodontic loads were no
threat to its osseous integration.
Most protocols indicate some degree of oblique insertion of the miniscrew.
For maxillary sites, the miniscrew needs a 30-60° angulation to the long axes of the
teeth for interproximal insertion. This increases the surface contact between the
miniscrew and the bone
[21]
, improving retention and reducing the risk of root contact.
In the mandible, because of the thicker cortical bone, usually only 10-20° of
angulation is required. Perpendicular insertion should be used only when there is
plenty of space between the roots of adjacent teeth.
Post operative instructions should be given to the patient before and after
17

the placement of the miniscrews. The patient should understand the importance of
maintaining hygiene around the miniscrew to ensure success. Excellent home care
greatly increases the chances of success.
[3, 21, 30, 31]
The miniscrews should be brushed
with a toothbrush and the surrounding tissues should be kept free of inflammation.
Chlorhexidine rinses have been recommended in some protocols to help ward off
inflammation and infection, and to control soft tissue inflammation around the
miniscrew.
[21]
Loading can be done immediately and can continue as long as the
screw is stable.
Once treatment is complete, removal of the screw usually does not require the
application of local anesthesia. In very sensitive patients, topical may be applied to
maintain their comfort. Then the screw can be backed out with the hand driver until
completely removed. Alternatively, as suggested by Kim et al, the screw can be
removed quickly and easily by initially loosening the miniscrew with the hand
driver, then by touching the miniscrew with a bur in a slow speed hand piece.
[32]

Orthodontic Loading of the Miniscrew
Many studies have investigated the influence of orthodontic loading on
miniscrew stability and success. Certain protocols have recommended a healing
period of various lengths,
[4, 12, 16, 33]
however, other studies indicate that there is no
correlation between immediate loading of miniscrew implants and increased failure
rates.
[3, 4, 16, 19, 24, 27, 30, 34, 35]
Most of these studies have suggested that there is no
difference between osseointegration amounts as well as clinical mobility between
18

immediately loaded and unloaded implants.
[3, 16, 17, 19, 27, 36, 37]
Ohmae et al,
[17]

demonstrated that loading did not increase failure rate, but could have an effect on
the percentage of osseointegration that occurs at the miniscrew bone interface. In
fact, his findings suggested that immediate loading increased bone remodeling
around the miniscrew, thereby enhancing its stability. Studies by Freudenthaler et
al
[3]
documented that single screws could be immediately loaded with orthodontic
forces without increasing failure, allowing for shorter treatment times and higher
patient acceptance. Therefore, according to current literature, miniscrews depend on
a mechanical lock in cortical bone, giving them primary stability and the ability to be
loaded immediately.
[15]
Forces can be applied either directly or indirectly to the
miniscrew, with no detrimental effects, as long as the screw remains stable. Screw
stability should be verified periodically by the clinician.
Wang et al
[25]
demonstrated that screws are clinically stable, but not
absolutely stationary when forces are loaded on them because they are not
completely osseointegrated. Although there is some displacement by the screws,
however, they have enough stability to complete orthodontic treatment.
Varying percentages of osseointegration with the miniscrew surface have
been reported by Melsen and Costa,
[16]
Owens
[37]
, and Vannet.
[38]
Increased amounts
of osseointegration have been associated with increased amount of time in the
mouth. However, lack of 100% osseointegration makes the miniscrew ideal for
temporary skeletal anchorage by allowing easy removal once treatment is complete.

19

Complications and Failure
The most obvious complication of miniscrew placement is iatrogenic damage
to dental or other vital structures such as the maxillary sinus, nerves, or blood
vessels.
[39]
Careful selection of sites for miniscrew placement, visualization of the
site with radiographs, and insertion with minimal force can help to minimize such
complications. More serious damage to tooth roots was documented by Coburn in
2002 in the placement of intermaxillary fixation screws for bony fixation following
maxillofacial surgery. He reported one case of tooth loss as a consequence of
burring into the apical region of teeth as well as multiple screw fractures.
[40]

Fortunately, severe damage resulting in tooth loss has not been documented in
orthodontic miniscrew placement, probably because of better tactile feel during
placement which allows the operator to redirect the miniscrew before causing serious
irreversible damage to adjacent teeth. Multiple studies documented that even severe
contact by titanium screws had little consequence on the teeth and that roots typically
recuperate fully, even when severely challenged.
[2, 21, 27, 41]
Fabbroni et al,
[41]

evaluated complications following contact of screws placed for fixation of fractured
mandibles. They observed that even when screw contact occurred, the incidence of
clinically significant damage was very low. From these findings, they concluded the
contact of sterile titanium on the root surface of a healthy tooth was of little
consequence and resulted in very few complications. Asscherickx et al
[42]
observed
that upon accidental damage to tooth roots of beagle dogs caused by miniscrew
insertion, an almost complete repair of the cementum lining the root occurred in a
20

period of 12 to 18 weeks after the screw was removed. In situations where
iatrogenic damage of adjacent teeth has been caused, the periodontal ligament space
is usually reestablished upon removal of the miniscrew, and the created lesion is
repaired with a narrow zone of cellular cementum on the root surface, with few other
complications.
[43]

Miniscrew fracture during insertion or removal is another complication that
must avoided. According to Carano et al,
[44]
forces associated with the placement
and removal of miniscrews can cause microscrew failure, especially if partial
osseointegration has occurred. They indicated that thinner screws were more likely
to fracture, therefore, the size of the miniscrew used should be carefully selected. In
order to minimize fractures, excessive force should never be used for insertion or
removal of miniscrews. If the clinician encounters difficulty removing the screw, a
second attempt should be made a few days after the initial attempt to avoid putting
excessive force on the screw and risking fracture. In the case of screw fracture, the
remaining piece may be trephined out, or, if the fragment is small enough, left in the
patient indefinitely with few complications.
[45]

Screw failure is perhaps the most troublesome complication because it results
in compromised anchorage. If a miniscrew is mobile and no longer provides
absolute anchorage, it should be removed and a new site for miniscrew placement
can be selected. Luzi et al observed a reduction in failure rates with an increase in
the experience of the clinician placing the miniscrew.
[24]
Chen et al
[46]46]
concluded
that miniscrews placed in younger patients or in the mandibular arch are at greater
21

risk of falling out. Motoyoshi et al
[47]
recommended a latent period of 3 months
before loading of miniscrews in adolescent patients. In another study in 2006, Chen
et al
[43]
noticed increased failure rates for miniscrews that contacted adjacent roots, a
finding that was also observed by Kuroda et al
[48]
in 2007. In 2003, Miyawaki et
al
[30]
conducted a study on miniscrew failure rates and concluded that three factors
were associated with increased failure of miniscrew implants placed in the buccal
alveolar bone of the posterior region for orthodontic anchorage: 1) the diameter of a
screw of 1.0 mm or less, 2) inflammation of the peri-implant tissue, and 3) a high
mandibular plane angle (which is associated with thinner cortical bone than in low
mandibular plane angle patients). Similar findings were reported by Poggio et al.
[19]

Miyawaki et al reported that miniscrews with inflammation of the peri-implant tissue
showed significantly lower success rates than those without inflammation. Therefore
he concluded that the prevention of inflammation is extremely important to prevent
mobility and subsequent failure of the miniscrew.
[30]
His results on inflammation
being highly correlated with implant failure coincided with other studies
.[16, 19, 24, 29, 34,
49-51]
. Cheng et al
[52]
reported that failure was more likely when screws were placed
in movable mucosa, possibly because of increased inflammation in these sites.
Tseng et al
[31]
found that the level of oral hygiene maintained by patients following
placement of miniscrews influenced their success rate. They observed that poor oral
hygiene led to inflammation of the tissues around the miniscrew which accelerated
their loss.
Soft tissue inflammation is a complication that is highly correlated to
22

screw failure and should be prevented when possible. Inflammation of the peri-
implant soft tissue has been associated with a 30% increase in failure rate.
[21, 37, 39]

Usually postoperative peri-implant mucositis is observed when the miniscrew is
placed in movable mucosa.
[2]
When miniscrews are placed in movable mucosa, they
are usually rapidly covered by tissue.
[39]
Therefore, most protocols suggest the use
of steel ligature wires attached to the miniscrew head and protruding from the tissue
when the miniscrew must be placed in movable mucosa.
[21]
However, whenever
possible, miniscrews should be placed in attached gingiva to avoid soft tissue
inflammation as well as increased chance of failure.

Width of Attached Gingiva
The gingiva consists of free and attached gingiva. The attached gingiva is the
portion of the gingiva that is firm, dense, stippled, and tightly bound to the
underlying periodontium, tooth, and bone. The mucogingival junction represents the
junction between the keratinized attached gingiva and the non-keratinized alveolar
mucosa.
[53]

In 1963, Bowers
[54]
measured the widths of the facial attached gingiva in 240
subjects to determine the normal width of attached gingiva in patients with healthy
gingiva. Extremes in the width of attached gingiva ranged from 1 to 9 mm. Values
were greatest in the incisor regions, and the least in the canine and first premolar
sites. The maxilla usually exhibited a broader zone of attached gingiva than the
mandible. He also concluded that the malposition of teeth affects the width of
23

attached gingiva. When a tooth was in buccoversion, it had a narrower zone of
attached gingiva than a tooth in proper alignment. When the tooth was in
linguoversion, it had a wider zone of attached gingiva than a tooth in proper
alignment. While his study provides general information on the width of attached
gingiva, the wide variation between patients and different malocclusions requires
that the width of attached gingiva is evaluated in each patient and site before
miniscrew placement.

Evolution of HumanTeeth and their Genetic Basis of Inheritance
The study of dental morphological characteristics has been a useful tool for
dentists as well as anthropologists. Teeth are a well preserved part of the body, and
accordingly constitute a large proportion of human fossil remains. They are easy to
measure, both in living and in fossil forms. Dental traits have a strong genetic
component responsible for their occurrence and expression. They are a close
reflection of the genotype and they are affected by the forces of natural selection.
Studies on dental morphological traits have provided information regarding
population origins, affinities and relationships, microevolutionary patterns, and
migrations patterns. Dental variability provides information on dental traits,
genetics, nutrition and evolution.
[55]

Tooth size has experienced a gradual reduction since the rise of modern man
during the Upper Paleolithic at the rate of roughly 1% per 2,000 years until the end
of the Pleistocene about 10,000 years ago. Beginning about 10,000 years ago, the
24

rate of reduction seems to have doubled to about 1% every 1,000 years. This
reduction in the size of the dentition has exceeded the reduction in body bulk
dramatically.
[56]

There is no single explanation of the mechanisms in dental reduction. Some
have suggested that dental reduction is a result of facial reduction, implying that the
forces of selection do not affect teeth directly. Some have suggested that smaller
teeth conserve precious biological resources, thereby providing an evolutionary
advantage. Others have suggested that as early humans acquired culinary skills,
teeth ceased to have survival value and they are just dwindling away due to the
Probable Mutation Effect (PME). This hypothesis attributes the reduction of teeth in
size and number to cultural factors.
[57]
The PME, proposed by Brace in 1963, has
provoked plenty of discussion and criticism. Brace proposed that the mechanism for
such change is through periodic mutations, which will gradually reduce an unneeded
structure, until it simply fades away.
[58]

Whatever was the cause of dental reduction in modern man, different
populations throughout the world were subjected to different selective pressures
from the environment. This resulted in differences in tooth size between the living
populations of the world, demonstrating genetic as well as environmental
components controlling tooth size.
Several factors can affect tooth size: sex, race, environment, and genetics. It
is generally agreed that inheritance of tooth dimensions is considered to be
multifactorial. The normal variation exhibited in the dentition is a result of a
25

polygenic mode of inheritance.
[59]
Tooth dimensions are not only dictated by genes,
but also by many environmental factors such as the mother’s health during
pregnancy, size and weight of offspring at birth, and nutrition and disease at the time
of ameloblast activity during crown formation.
[60]

Dempsey et al
[61]
studied 596 subjects, including 149 monozygotic twins and
149 dizygotic twins, to quantify the relative contributions of various genetic and
environmental factors to the variation in mesiodistal and buccolingual dimensions of
permanent teeth. The range of additive genetic variation was found to be from 56-
92% with most over 80%. The environmental effects ranged from 8-29%. A
significant shared or common environmental influence on maxillary first molar
crown size (22-27%) is consistent with their early development. Osborne et al
[62]

studied anterior teeth in twins and determined that tooth size variability in the
incisors is greater in dizygotic twins than in monozygotic twins. However, less
variation was shown in the canines, showing a strong hereditary component in the
mesiodistal size of the incisors and less in the canines. Lundstrom
[63]
also found that
monozygotic twins had a stronger correlation of mesiodistal tooth size than dizygotic
twins.
Garn et al has conducted several studies on heredity and tooth size. In 1978,
Garn et al proposed that 90% of tooth variation was genetically determined.
[64]
In
another study, he evaluated tooth size differences between siblings of the same and
opposite sex. The strongest correlation between tooth sizes existed between sister-
sister, followed by brother-brother, and then sister-brother siblings. This pattern
26

suggested X-linked inheritance of tooth size. Garn proposed that sexual dimorphism
in tooth size could be the caused by a possible role played by the Y-chromosome.
Garn et al
[65]
then found that tooth shape was more variable in males, adding to the
evidence that tooth size and shape are X-linked. He attributed greater variability in
tooth size and shape in males than females to a “less effective genetic control of
tooth size in the XY as compared to the XX.”

Gender and Ethnic Differences in Tooth size
Ethnic and gender differences in tooth size and shape have been studied by
researchers worldwide, on every continent, including Asia, Africa, Australia, Europe,
South America, and North America. In 1991, Harris and Rathbun
[66]
studied ethnic
differences in the apportionment of tooth sizes. Mesiodistal and buccolingual
measurements of teeth from a worldwide human sample were used to ascertain
dental patterns in different populations. The samples were categorized into six
geographic/cultural groups: Subsaharan Africa, Western Europe and Mideast,
Aboriginal Australia, Melanesia, Asia and the Pacific, and the Aboriginal
Americans. He identified Caucasians, Africans, and Asians as possessing relatively
small teeth and he characterized Australians as megadonts.
Differences between Caucasian and Hispanic groups have been far less
documented than differences between Caucasian and black samples, or even between
Caucasian and Asian samples. Caucasian and Hispanic groups are more similar in
tooth width than Caucasian and black groups, with Caucasian teeth being slightly
27

smaller than Hispanic teeth.
Upatham
[67]
studied tooth size differences between Caucasian, Hispanic,
African American and Asian samples. He found that Hispanics had significantly
larger maxillary and mandibular 1
st
molars than Asians and Caucasians, and less
significantly larger than African Americans. He found that Hispanics had
significantly larger maxillary lateral incisors, mandibular canines, and mandibular
incisors than Caucasians, but significantly smaller maxillary canines and maxillary
2
nd
bicuspids. Upatham also found that teeth were significantly larger in males than
females across both arches.
Smith et al
[68]
studied three populations: African Americans, Hispanics, and
Caucasians. 30 male and 30 female pre-orthodontic casts were evaluated in each
population. Significant differences in anterior, posterior, and overall ratios were
found among ethnic groups, especially between Caucasians and African Americans.
Overall ratios for Caucasians were the smallest at 92.3%, followed by Hispanics at
93.1%, then African Americans at 93.4%. In addition, there were significant
posterior and overall ratio differences between males and females caused by larger
mandibular posterior segments in males.
Lavelle
[69]
studied 120 models of English dental patients consisting of 40
Caucasians from England, 40 immigrant Negroids from Africa, and 40 immigrant
Mongoloids from Hong Kong. He found that average tooth size was greatest in
Negroids, followed by Mongoloids, then Caucasians. He also found tooth widths
were greater for males than females. Keene
[70]
studied tooth size differences
28

between 56 black and 387 white Americans from a wide geographic area and
confirmed that blacks had larger teeth when compared to Caucasians. Merz et al
[71]

compared study model measurements of 51 black and 50 white preorthodontic
patients and found that black patients had larger lower canines, premolars and first
molars than white patients. They found no significant differences in the size of the
incisors.
Gender differences have also been studied by researchers. In general,
researchers have found that mesiodistal tooth size tends to be larger in males than in
females. In most human populations, the lower canines show the greatest
dimorphism (up to 7.3%), followed by the upper canine. Garn et al
[65]
studied 243
subjects from southwestern Ohio. He measured mesiodistal widths of teeth and
determined that dimorphism was greatest for canines, next first molars, and lastly
mandibular incisors. He found there was 4% overall dimorphism and 6%
dimorphism in canine size. Then he compared nine populations and found that the
largest percentage of dimorphism was up to 7.3%, and magnitude and patterning
differed for each population.
Richardson and Malhotra
[72]
examined 162 study models and found
mesiodistal tooth sizes were greater in African American males than females. Gillen
et al
[73]
made measurements on maxillary anterior teeth of black and white males and
females. His results showed males had significantly longer incisors than females.
He also found that blacks had significantly wider canines than whites, and males had
significantly wider canines than females. No racial or gender differences were
29

found for incisor widths. Cumulative widths from canine to canine did not differ for
ethnicity or gender although individual measurements varied. Length to width ratios
for individual teeth showed no significant differences for race or gender. Santoro et
al
[74]
found that Dominican American males had on average larger teeth than
females.
While differences in tooth size between different ethnicities and gender are
well documented, inconsistencies between studies could be attributed to other factors
that affect tooth size, thereby making clear cut distinctions difficult. While teeth are
subject to sexual dimorphism, there has been a substantial decrease in sexual
dimorphism in modern day. This trend for decreased sexual dimorphism has been
associated with the overall trend for dental reduction. The evidence suggests that
reduction in sexual dimorphism is more related to changes in male dentitions than to
changes in female tooth size.
Another factor affecting tooth size is the relationship of tooth size to body
size. It is widely accepted that there is a low but positive correlation between tooth
size and body size within any given population.
[75-77]
While some authors argue that
tooth size has become “decoupled” from body size during the recent evolutionary
past as the rate of tooth size decline has accelerated, distinguishing tooth size by
ethnicity or gender is still difficult.
[78]

\
30

Other Factors Affecting Interradicular Space
No previous study has evaluated differences in interradicular space
availability between ethnicity and gender. Factors that could potentially affect the
amount of interradicular space available other than mesiodistal tooth size are dental
crowding, eruption patterns, size of arches, and the location of interproximal contact
points.
In 2003, Buschang and Shulman
[79]
evaluated data derived from a random
sample of 9044 subjects whose data was collected in a National survey. By gender,
the sample consisted of 49% male and 51% female subjects. By ethnicity, the
sample consisted of 35% Hispanic, 34% African American, and 31% Caucasian
subjects, between 15 to 50 years of age. They found that males had significantly
greater incisor crowding than females. African Americans had significantly less
crowding than Caucasians and Hispanics. Hispanics had more crowding than
Caucasians, but this difference was not significant. The presence of more crowding
would decrease interproximal and interradicular space.
In 2006, Kennedy
[80]
evaluated differences in eruption times between 527
Caucasian and Hispanic patients. He found that teeth erupted significantly earlier in
Hispanic patients than in Caucasian patients. Early eruption could potentially
decrease crowding by reducing the probability that primary teeth will be lost
prematurely due to caries, resulting in the loss of arch length by mesial tipping of the
mandibular 1
st
molar.
In 2007, Gimlen
[81]
studied gender differences in arch width. She found
31

that with the exception of canine depth, Hispanic arches were significantly larger in
all dimensions when compared to the Caucasian sample. She found that this held
true for all malocclusion types.
Soon after the alignment of all of the teeth in their respective positions in the
jaws takes place, there should be a positive contact relation mesially and distally of
one tooth with another in the arch. Although the areas of contact are still very
circumscribed, especially on anterior teeth, these are areas and not mere points of
contact. Proper contact and alignment of adjoining teeth will allow proper spacing
between them for the normal bulk of gingival tissue attached to the bone and
teeth.
[82]

In a healthy mouth the proximal contact area formed is small enough to
prevent a buildup of excessive amounts of bacteria, food, or proximal debris, but
large enough to be an effective barrier and to prevent food from packing between the
teeth. Because the teeth do slightly touch, they offer support and anchorage to one
another as well as resistance to displacement from traumatic forces.
[83]

The proximal contact areas are located at the widest portion and at the
greatest curvature on the mesial and distal surfaces of each tooth. Since the teeth are
narrower at the cervix mesiodistally than they are toward the occlusal surfaces and
since the outline of the root continues to taper from that point to the apices of the
roots, considerable spacing is created between the roots of one tooth and another,
anchoring the teeth securely in the jaws. Over time, restorations and occlusal forces
causing interproximal wear can broaden and flatten contact areas, reducing the
32

interproximal and interradicular space.
[82, 83]

The shape of the tooth has a bearing upon the interproximal space. Some
individuals have teeth that are wide at the cervices, constricting the space at the base.
Others have teeth that are more slender at the cervices than usual; this type of tooth
widens the space. Teeth that are oversized or unusually small will likewise affect the
interproximal spacing. Similarly, the shape of the root will also affect the amount of
space available between roots. Nevertheless, this spacing will conform to a plan that
is fairly uniform in each patient, provided that the anatomic form is normal and teeth
are in good alignment.

Cone Beam Computed Tomography
Computed Tomography (CT) was developed by Hounsfield and first put to
practical use in 1972.
[84]
Over years, the technology introduced by Hounsfield has
been modified and improved to increase scanning speed, reduce radiation exposure
to the patient, and improve image quality. The use of CT allows three dimensional
imaging of craniofacial structures without the magnification distortion and
superimposition errors inherent in traditional forms of radiography. It provides
excellent tissue contrast, and eliminates blurring and overlapping of adjacent
teeth.
[85]
However, the use of CT for visualization of craniofacial structures was
limited because of their high cost, increased levels of radiation exposure and
complexity.
[86]

With the introduction of cone beam computed tomography (CBCT), three
33

dimensional imaging of craniofacial structures for dentistry became much more
practical. CBCT machines could be manufactured at more reasonable costs, and
exposed the patient to much smaller amounts of radiation than traditional CT
scans.
[86, 87]
CBCT allows dimensionally accurate, 1:1 imaging of craniofacial
structures. A single scan can produce images in any plane of space, and a 3D graphic
rendering of the object allows the clinician to zoom, rotate, and pan through voxels
of the image.
[88]
Its use was quickly accepted into implant dentistry for precise
imaging in implant placement. Recent advancements in image production has
allowed secondary reconstructions of CBCT data into panoramic, lateral
cephalometric, and anterior-posterior cephalometric images, making it a viable
imaging modality in other aspects of dentistry, including orthodontics.
[89]

In CBCT, a conical beam of X-rays that is sized to encompass a region of
interest rotates about the patient in a circular path. Image data is acquired in a single
revolution of a paired source and set of detector arrays and collects a volume of
information, as opposed to a stack of multiple slices of the scanned object as in
conventional CT.
[87]

CBCT vs. Traditional Radiography
Studies which have directly compared CBCT images to traditional imaging
techniques have shown that magnification and distortion errors are prevalent in
traditional radiographs.
[89, 90]
Peck et al
[89]
compared the accuracy of panoramic
radiographs with CBCT in assessing mesiodistal root angulations. They found
34

measurements made on CBCT images obtained from NewTom scans were more
similar to the measurements obtained from models than panoramic radiographs.
They also found that panoramic radiographs both overestimated and underestimated
root angulation of teeth around the arch. They concluded that panoramic radiographs
were sufficient as a screening tool, however did not offer the precision and reliability
that CBCT did in assessing mesiodistal root angulations.
[89]

Xie et al
[90]
stated that panoramic radiographs provide a distorted two-
dimensional representation of a three-dimensional object. Because large
discrepancies exist between ideal and actual beam direction in the capture of a
panoramic radiograph, distortion is unavoidable.
[90]
Ideal beam projection angles
required to open interproximal contacts changes throughout the arch, causing
magnification and distortion of the resulting panoramic image. This sort of
discrepancy is especially prominent in the premolar region, causing overlapping of
teeth in this region of panoramic radiographs.
[89, 90]

Additionally, head positioning and geometry of the patient can further distort
the panoramic representation of a patient.
[89]
While changes in head position
drastically effect the images produced by traditional methods, CBCT images can be
controlled to minimize distortions caused by changes in head position.
[84, 89]

One disadvantage in the orthodontic use of the highly accurate images
produced by CBCT is the fact that all previous cephalometric standards are based on
conventional two-dimensional representations of the head.
[88, 89]
In order to account
for this, most software for analyzing data from CBCT scans include the option of
35

simulating a beam projection like that of a traditional lateral cephalometric machine,
producing the perspective and magnification of a traditional two-dimensional
cephalogram to allow for comparisons to the populational norms available from
previous standards.
[88]

Another area of concern regarding the use of CBCT images for orthodontics
has been the difficulty of superimposing images in order to evaluate patient growth
and/or facial change induced by orthodontic movement. Cevidanes et al
[88]

addressed this issue by describing superimposition methods which do not depend on
landmarks or planes, but instead compare the cranial base structures voxel by voxel.
He stated that 3D models allow superimposition along the whole surface of the
cranial base for adults or in the anterior cranial fossae for growing children. The
automation of these methods by software programs like Valamet allows image
analysis procedures to be largely independent of operator error. Valamet can even
color code the magnitude of displacement to clearly demonstrate the changes that
have occurred with growth and treatment. The continuous development of new
software like this will make the implementation of CBCT images in orthodontics
more practical.

Accuracy of CBCT Derived Measurements
With the rapid induction of CBCT into various fields of dentistry, the
accuracy of measurements derived from CBCT images was a popular topic of
investigation. In 2004, Lascala et al
[91]
compared 13 linear measurements made
36

on dry skulls measured with a digital caliper to the same measurements made after
the skulls were scanned with NewTom 9000 CBCT and analyzed using the
NewTom’s software. They showed that the NewTom images consistently
underestimated the true distances. However, these differences were significant only
for the internal structures of the skull base. They concluded that linear
measurements from CBCT images were reliable for structures more closely
associated with the dentomaxillofacial complex.
[91]

In 2005, Marmulla et al
[92]
tested the geometric accuracy of a NewTom 9000
by scanning an geometric object with 216 measuring points. They found a
maximum deviation of 0.3 mm from the original object and concluded that the
images from the NewTom 9000 were geometrically correct.
In 2008, Stratemann et al
[87]
compared measurements of length from the
NewTom 9000 and Hitachi MercuRay to physical measurements with a caliper taken
off the dry skull. Landmarks were identified with chromium steel balls embedded at
32 cranial and 33 mandibular sites. They found minor compression relative to the
caliper measurement, however, they concluded that images acquired from CBCT
were highly accurate with less than 1% relative error.
A study by Togashi et al
[84]
measured the influence of head position on the
accuracy of linear measurements. They plotted 18 points on a dry skull which was
then scanned. The skull was then tilted in different planes by 10°. They found that
errors in all linear measurements were less than 5% compared to the actual length
measured on the skull when a slice thickness of 1 mm or 3 mm was used.
37

However, a slice thickness of 5 mm or 7 mm resulted in larger measurement errors.
Therefore, they concluded that errors from head inclination could be minimized by
reducing slice thickness.

NewTom 9000 CBCT System
The NewTom 9000 (Quantitative Radiology, Verona, Italy) is a CBCT
volume imaging machine designed specifically for dental and maxillofacial imaging,
and received FDA approval in April 2001.
[89, 91]
It uses cone-beam radiation to
gather three-dimensional information with drastically reduced radiation exposure
that approaches the levels of traditional dental radiography. The effective absorbed
radiation dose for a scan with the NewTom 9000 is approximately 50 µSv, an
amount similar to the adsorbed radiation dose of a full mouth series.
[89]
In
comparison, a traditional medical CT can result in an effective absorbed radiation
dose as high as 656.9 µSv, while the effective dose of a panoramic radiograph ranges
from 2.9 – 9.6 µSv and that of a full mouth series ranges from 33 – 100 µSv.
[85]

38
The NewTom 9000 uses a cone-shaped X-ray beam centered on an X-ray
detector which rotates 360° around the head and acquires one image for each degree
in an exposure time of 17 seconds. The images acquired through the scan undergo
primary reconstruction into a 3D volume comprised of voxels. Voxel thickness and
therefore image resolution is determined by the slice thickness and field size selected
by the operator. For this study, both 9 and 12 inch sensors were used and scans were
taken in the small field setting. According to the manufacturer, these settings yield
voxel sizes of 0.25 mm and 0.36 mm respectively.
[88, 93]

Software allows for the production of secondary reconstructions that show
structures of interest from many viewpoints. In this study, InVivoDental Software
was used for viewing and measuring distances and angles on the images in 3D
volume rendering. InVivo Dental
TM
3.1 software is a volumetric imaging software
designed specifically for dental clinicians that was made by Anatomage, Inc. With
InVivo Dental’s volume rendering, clinicians can easily manipulate, enhance, and
slice the volume in any orientation or shape for quick and effective diagnosis. For
this study, linear and angular measurement tools in the software were used to
evaluate interradicular sites.

39

Chapter 3: HYPOTHESES
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* significantly differs between interradicular sites
measured.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* significantly differs between Caucasians and Hispanics.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* significantly differs between males and females.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* is coronally located to allow miniscrew placement
through attached gingiva.
* Adequate bone stock for miniscrew placement was considered to be 3 mm
40

NULL HYPOTHESES
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* does not significantly differ between interradicular sites
measured.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* does not significantly differ between Caucasians and
Hispanics.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* does not significantly differ between males and females.
- The vertical distance from the CEJ to adequate amount of bone stock for
miniscrew placement* is not coronally located to allow miniscrew placement
through attached gingiva.
* Adequate bone stock for miniscrew placement was considered to be 3 mm

41

Chapter 4: MATERIALS AND METHODS
Pretreatment CBCT data of 60 orthodontic patients treated at the University
of Southern California, Graduate Orthodontic Clinic were selected for evaluation.
Scans were taken with the department’s NewTom 9000 Volume Scanner QRsr1
Verona CBCT unit. Patients were selected according to the following inclusion
criteria: (1) no manifestation of positioning errors, (2) complete eruption of all
second permanent molars, (3) presence of complete dentitions and (4) minimal
refraction from dental restorations. The availability of bone for the placement of
miniscrews was evaluated at 18 interradicular sites (Fig. 1).
The diameter of screws used in clinical practice range from 1.2 to 2mm. The
requisites of successful miniscrew placement dictate 1 mm of bone between the
screw and the periodontal ligament/root structures, as well as placement in attached
gingiva. Accounting for the tapered nature of many miniscrews, as well as the
oblique insertion angle that is frequently implemented in placement, 3 mm of bone
available mesio-distally between roots was determined to be adequate bone stock for
placement of a miniscrew.
Each site was evaluated for the most coronal presence of 3 mm of bone
available mesiodistally between roots. When 3 mm of bone was located, a
subsequent vertical measurement was made from a line connecting the CEJs of the
adjacent teeth to this site. (Fig 2) InVivo Dental
TM
software was used to evaluate the
18 sites in 3-dimensional volume rendering. For each site, the “cut” tool in InVivo
Dental
TM
software was used to remove extraneous structures in order to
42

accurately visualize the tooth segment and interproximal area of interest (Fig 3 & 4).
Next, this segment was vertically aligned so that the CEJs of adjacent teeth were
parallel to a true horizontal line. Then the segment was horizontally manipulated
until the contact point between adjacent teeth of the interproximal area of interest
was broken. (Fig. 5) The measurement tool in InVivo Dental
TM
software was then
used to measure the distance between roots. These horizontal linear measurements
were made parallel to the CEJ line. Once the most coronal location of 3 mm of
space between adjacent teeth was located, a vertical measurement from the CEJ line
to this location was made. The angle measurement tool on InVivo Dental
TM

software was used for this purpose in order to obtain a vertical line that was
perpendicular to the CEJ line. (Fig. 6)
Three situations were observed while recording the vertical measurements
from the CEJ to the most coronal location of 3 mm of interradicular space. In
situation 1, the most coronal location of 3 mm of space existed at the CEJ and
subsequently all the way down to the root apices. Therefore 3 mm of interradicular
space was always available. (Fig 7) In situation 2, the most coronal location of 3
mm of space was located at some vertical distance apical to the CEJ. (Fig 8) In
situation 3, 3 mm of space was never located between the roots of the interproximal
space in question. (Fig 9)
In order to allow for statistical evaluation of the data, vertical distance
measurements were organized into 7 “space available” categories. (Table 1) The
categories were: A—3mm of interradicular space was always available for the site
43

from the CEJ down to the root apices; B—3 mm of interradicular space was
available at a vertical distance between 0-3 mm away from the CEJ; C—3 mm of
interradicular space was available at a vertical distance between 3-6 mm away from
the CEJ; D—3 mm of interradicular space was available at a vertical distance
between 6-9 mm away from the CEJ; E—3 mm of interradicular space was available
at a vertical distance between 9-12 mm away from the CEJ; F—3 mm of
interradicular space was available at a vertical distance greater than 12 mm away
from the CEJ; and N—3mm of interradicular space was never available anywhere
between the roots from the CEJ down to the root apices. The frequency of
occurrence for each category was analyzed for each site, as well as for differences
between sites, gender groups, and ethnic groups.
Method error was measured by statistically analyzing the difference between
duplicate measurements collected 2 weeks apart on 12 patients randomly selected
from the sample.

FIGURE 1: Schematic diagram of the 18 sites evaluated

FIGURE 2: Schematic
diagram of the horizontal
and vertical measurements
made

44

FIGURE 3: Original volume rending of patient

FIGURE 4: Cut function used to remove extraneous structures

45

FIGURE 5: Section aligned vertically (so CEJs of adjacent teeth surrounding site of interest are
parallel with a true horizontal line) and horizontally, so that contact point of site of interest is
broken). Site of interest in this example is between the 2
nd
bicuspid and 1
st
molar

FIGURE 6: Example of horizontal and vertical measurements made. First, the most coronal
location of 3 mm of space was found. Then the angular measuring tool was used to measure
the vertical distance from the CEJ line to the location of 3 mm of space at a 90° angle (±1°).
In this example, the vertical distance measurement was 7.88 mm

46

FIGURE 7: space always available

FIGURE 8: space available at a vertical distance from CEJ

47

FIGURE 9: space never available

TABLE 1: Space Available Categories

Space
Available
Category
Vertical measurement to
3 mm of interradicular
space available
A 3 mm of interradicular
space was always available
B 3 mm space located 0-3
mm from the CEJ
C 3 mm of space located 3-6
mm from the CEJ
D 3 mm of space located 6-9
mm from the CEJ
E 3 mm of space located 9-12
mm from the CEJ
F 3 mm of space located >12
mm from the CEJ
N 3 mm of interradicular
space was never available

48

ANALYSIS OF DATA
Descriptive statistics were calculated for the sample. The Fisher Exact test
was used to assess the difference of space availability between gender groups and
ethnic groups as well as at each site. For all the tests, α< .05 is defined as the
significance level.
Next, the original 7 categories were reassigned numerical values from 0 to 6,
with 0 indicating that there was always 3 mm of interradicular space and 6 indicating
that there was never 3 mm of space. This was done in order to analyze general
trends within the data. A General Linear Model (GLM) was used to evaluate the
“average” space available category after adjusting ethnic groups and gender.
All measurements were made by one examiner. Method error was assessed
by statistically analyzing the difference between duplicate measurements made by
the same examiner collected 2 weeks apart on 12 patients randomly selected from the
sample. Because the data does not hold the assumption of normality, Spearman’s
Rank Correlation test was used to examine the reliability of the repeated
measurements.
49

Chapter 5: RESULTS
The availability of sufficient interradicular bone stock of 3 mm for miniscrew
placement was evaluated at 18 interradicular locations by evaluating images derived
from NewTom 9000 CBCT data on 60 patients and a statistical analysis was
completed.

SAMPLE CHARACTERISTICS
A total of 60 patients evaluated and were equally divided into gender and
ethnic groups. 30 patients (50%) were males and 30 patients (50%) were females.
For each gender group, 15 patients were Caucasian (total of 30 Caucasian patients,
50% of study population) and 15 patients were Hispanic (total of 30 Hispanic
patients, 50% of study population). Therefore, gender and ethnic categories divided
the sample into 4 equal groups of 15 patients, consisting of 25% of the total sample.
The age for the males ranged from 14-29 years old, with a median of 18 years old.
The age for the females ranged from 15-46 years old, with a median of 26 years old.

RELIABILITY OF MEASUREMENTS
50
The reliability of measurements was assessed by analyzing the difference
correlation between repeated measurements made by the same examiner, collected 2
weeks apart on 12 patients randomly selected from the sample. Because the data
does not hold the assumption of normality, Spearman’s Rank Correlation test was
used to examine the reliability of the repeated measurements.

The correlation coefficient ρ was 0.96 (p-value < .0001), indicating the two
measures are highly correlated. As a ρ > .8 is generally regarded as the threshold for
reliability, the measurements of this study were found to be fairly reliable.

ANALYSIS OF DATA—DESCRIPTIVE STATISTICS
A total of 18 sites were evaluated in each patient. The availability of 3 mm
of interradicular bone was evaluated, followed by a vertical measurement when 3
mm of bone was located. Vertical measurements were then sorted into “space
available” categories A, B, C, D, E, F, and N for statistical analysis. Table 2 shows a
frequency distribution for all patients according to site. In the cells of this table, the
first number is the number of patients with that space available category at that site
(n). The second number is the percent that n is of the total number of patients, 60.
Sites 1, 9, between upper 1
st
and 2
nd
molars, and sites 13, 14, and 15, between
lower incisors and cuspids, are the least likely sites to have 3mm of space available.
Sites 10 and 18, between the lower 1
st
and 2
nd
molars, were the most likely to have 3
mm of space available coronally. Sites 11 and 17, between the lower 2
nd
bicuspids
and 1
st
molars, were the next most likely sites to have 3 mm of space available
coronally. Sites 12 and 16, between lower 1
st
and 2
nd
bicuspids, were the next most
likely to have 3 mm of space available coronally. The frequency of space available
shows a symmetrical pattern in both the maxilla and mandible.
51

TABLE 2: Distribution of space availability by site
Table 2: Frequency Distribution of all patients by Site
Site Space Available Category
Frequency
Row Pct A B C D E F N Total
1 0
0.00
1
1.67
3
5.00
1
1.67
5
8.33
1
1.67
49
81.67
60
2 6
10.00
1
1.67
3
5.00
13
21.67
22
36.67
2
3.33
13
21.67
60
3 6
10.00
0
0.00
5
8.33
5
8.33
13
21.67
4
6.67
27
45.00
60
4 1
1.67
1
1.67
5
8.33
6
10.00
14
23.33
1
1.67
32
53.33
60
5 2
3.33
0
0.00
8
13.33
12
20.00
16
26.67
2
3.33
20
33.33
60
6 0
0.00
0
0.00
7
11.67
10
16.67
7
11.67
5
8.33
31
51.67
60
7 7
11.67
0
0.00
5
8.33
5
8.33
10
16.67
4
6.67
29
48.33
60
8 12
20.00
1
1.67
2
3.33
8
13.33
17
28.33
6
10.00
14
23.33
60
9 1
1.67
0
0.00
0
0.00
2
3.33
8
13.33
2
3.33
47
78.33
60
10 30
50.00
1
1.67
3
5.00
15
25.00
2
3.33
1
1.67
8
13.33
60
11 17
28.33
0
0.00
7
11.67
11
18.33
15
25.00
4
6.67
6
10.00
60
12 12
20.00
4
6.67
14
23.33
16
26.67
3
5.00
3
5.00
8
13.33
60
13 0
0.00
0
0.00
0
0.00
5
8.33
5
8.33
1
1.67
49
81.67
60
14 0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
60
100.00
60
15 1
1.67
0
0.00
0
0.00
6
10.00
6
10.00
1
1.67
46
76.67
60
16 9
15.00
1
1.67
15
25.00
9
15.00
8
13.33
4
6.67
14
23.33
60
17 19
31.67
2
3.33
6
10.00
13
21.67
12
20.00
3
5.00
5
8.33
60
18 25
41.67
0
0.00
7
11.67
13
21.67
7
11.67
2
3.33
6
10.00
60

52

DESCRIPTIVE STATISTICS OF INDIVIDUAL SITES MEASURED
COMPARISON OF SITES MEASURED: HISPANIC VS. CAUCASIAN
Since most of the cells have expected counts less than 5, the Chi-square test
is not a valid statistic. Therefore, the Fisher Exact test was used instead to test
differences at each site between different ethnic groups. There are statistically
significant differences in space availability between Caucasians and Hispanics at site
12, the space between lower left 1
st
and 2
nd
bicuspids (p-value=0.0069), and site 18,
the space between the lower right 1
st
and 2
nd
molars (p-value=0.0065). At sites 12
and 18, Hispanics were more likely to have space available coronally than
Caucasians.

53

TABLE 3: Space available category by ethnicity, Site 1

Site 1: Upper right 1
st
molar—2
nd
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct B C D E F N Total
Caucasian 1
1.67
3.33
100.00
3
5.00
10.00
100.00
1
1.67
3.33
100.00
1
1.67
3.33
20.00
0
0.00
0.00
0.00
24
40.00
80.00
48.98
30
50.00

Hispanic 0
0.00
0.00
0.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
4
6.67
13.33
80.00
1
1.67
3.33
100.00
25
41.67
83.33
51.02
30
50.00

Total 1
1.67
3
5.00
1
1.67
5
8.33
1
1.67
49
81.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0027
Pr <= P 0.1240

FIGURE 10: Space available category by ethnicity, Site 1

54

TABLE 4: Space available category by ethnicity, Site 2

Site 2: Upper right 1
st
bicuspid—1
st
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 3
5.00
10.00
50.00
1
1.67
3.33
100.00
1
1.67
3.33
33.33
6
10.00
20.00
46.15
10
16.67
33.33
45.45
1
1.67
3.33
50.00
8
13.33
26.67
61.54
30
50.00

Hispanic 3
5.00
10.00
50.00
0
0.00
0.00
0.00
2
3.33
6.67
66.67
7
11.67
23.33
53.85
12
20.00
40.00
54.55
1
1.67
3.33
50.00
5
8.33
16.67
38.46
30
50.00

Total 6
10.00
1
1.67
3
5.00
13
21.67
22
36.67
2
3.33
13
21.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0014
Pr <= P 0.9500

FIGURE 11: Space available category by ethnicity, Site 2

55

TABLE 5: Space available category by ethnicity, Site 3

Site 3: Upper right 1
st
bicuspid—2
nd
bicuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Caucasian 1
1.67
3.33
16.67
3
5.00
10.00
60.00
3
5.00
10.00
60.00
8
13.33
26.67
61.54
2
3.33
6.67
50.00
13
21.67
43.33
48.15
30
50.00

Hispanic 5
8.33
16.67
83.33
2
3.33
6.67
40.00
2
3.33
6.67
40.00
5
8.33
16.67
38.46
2
3.33
6.67
50.00
14
23.33
46.67
51.85
30
50.00

Total 6
10.00
5
8.33
5
8.33
13
21.67
4
6.67
27
45.00
60
100.00
Fisher's Exact Test
Table Probability (P) 7.858E-04
Pr <= P 0.5988

FIGURE 12: Space available category by ethnicity, Site 3

56

TABLE 6: Space available category by ethnicity, Site 4

Site 4: Upper right lateral incisor—cuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 0
0.00
0.00
0.00
0
0.00
0.00
0.00
2
3.33
6.67
40.00
4
6.67
13.33
66.67
7
11.67
23.33
50.00
1
1.67
3.33
100.00
16
26.67
53.33
50.00
30
50.00

Hispanic 1
1.67
3.33
100.00
1
1.67
3.33
100.00
3
5.00
10.00
60.00
2
3.33
6.67
33.33
7
11.67
23.33
50.00
0
0.00
0.00
0.00
16
26.67
53.33
50.00
30
50.00

Total 1
1.67
1
1.67
5
8.33
6
10.00
14
23.33
1
1.67
32
53.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0026
Pr <= P 0.8827

FIGURE 13: Space available category by ethnicity, Site 4

57

TABLE 7: Space available category by ethnicity, Site 5

Site 5: Upper central incisors
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Caucasian 1
1.67
3.33
50.00
3
5.00
10.00
37.50
6
10.00
20.00
50.00
10
16.67
33.33
62.50
1
1.67
3.33
50.00
9
15.00
30.00
45.00
30
50.00

Hispanic 1
1.67
3.33
50.00
5
8.33
16.67
62.50
6
10.00
20.00
50.00
6
10.00
20.00
37.50
1
1.67
3.33
50.00
11
18.33
36.67
55.00
30
50.00

Total 2
3.33
8
13.33
12
20.00
16
26.67
2
3.33
20
33.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0024
Pr <= P 0.9012

FIGURE 14: Space available category by ethnicity, Site 5

58

TABLE 8: Space available category by ethnicity, Site 6

Site 6: Upper left lateral incisor—cuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct C D E F N Total
Caucasian 4
6.67
13.33
57.14
4
6.67
13.33
40.00
5
8.33
16.67
71.43
1
1.67
3.33
20.00
16
26.67
53.33
51.61
30
50.00

Hispanic 3
5.00
10.00
42.86
6
10.00
20.00
60.00
2
3.33
6.67
28.57
4
6.67
13.33
80.00
15
25.00
50.00
48.39
30
50.00

Total 7
11.67
10
16.67
7
11.67
5
8.33
31
51.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0020
Pr <= P 0.4853

FIGURE 15: Space available category by ethnicity, Site 6

59

TABLE 9: Space available category by ethnicity, Site 7

Site 7: Upper left 1
st
bicuspid—2
nd
bicuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Caucasian 3
5.00
10.00
42.86
1
1.67
3.33
20.00
3
5.00
10.00
60.00
5
8.33
16.67
50.00
1
1.67
3.33
25.00
17
28.33
56.67
58.62
30
50.00

Hispanic 4
6.67
13.33
57.14
4
6.67
13.33
80.00
2
3.33
6.67
40.00
5
8.33
16.67
50.00
3
5.00
10.00
75.00
12
20.00
40.00
41.38
30
50.00

Total 7
11.67
5
8.33
5
8.33
10
16.67
4
6.67
29
48.33
60
100.00
Fisher's Exact Test
Table Probability (P) 7.741E-04
Pr <= P 0.5813

FIGURE 16: Space available category by ethnicity, Site 7

60

TABLE 10: Space available category by ethnicity, Site 8

Site 8: Upper left 2
nd
bicuspid—1
st
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 4
6.67
13.33
33.33
1
1.67
3.33
100.00
2
3.33
6.67
100.00
5
8.33
16.67
62.50
8
13.33
26.67
47.06
4
6.67
13.33
66.67
6
10.00
20.00
42.86
30
50.00

Hispanic 8
13.33
26.67
66.67
0
0.00
0.00
0.00
0
0.00
0.00
0.00
3
5.00
10.00
37.50
9
15.00
30.00
52.94
2
3.33
6.67
33.33
8
13.33
26.67
57.14
30
50.00

Total 12
20.00
1
1.67
2
3.33
8
13.33
17
28.33
6
10.00
14
23.33
60
100.00
Fisher's Exact Test
Table Probability (P) 2.567E-04
Pr <= P 0.5072

FIGURE 17: Space available category by ethnicity, Site 8

61

TABLE 11: Space available category by ethnicity, Site 9

Site 9: Upper left 1
st
molar—2
nd
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A D E F N Total
Caucasian 0
0.00
0.00
0.00
1
1.67
3.33
50.00
4
6.67
13.33
50.00
1
1.67
3.33
50.00
24
40.00
80.00
51.06
30
50.00

Hispanic 1
1.67
3.33
100.00
1
1.67
3.33
50.00
4
6.67
13.33
50.00
1
1.67
3.33
50.00
23
38.33
76.67
48.94
30
50.00

Total 1
1.67
2
3.33
8
13.33
2
3.33
47
78.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0382
Pr <= P 1.0000

FIGURE 18: Space available category by ethnicity, Site 9

62

TABLE 12: Space available category by ethnicity, Site 10

Site 10: Lower left 1
st
molar—2
nd
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 12
20.00
40.00
40.00
0
0.00
0.00
0.00
2
3.33
6.67
66.67
11
18.33
36.67
73.33
2
3.33
6.67
100.00
0
0.00
0.00
0.00
3
5.00
10.00
37.50
30
50.00

Hispanic 18
30.00
60.00
60.00
1
1.67
3.33
100.00
1
1.67
3.33
33.33
4
6.67
13.33
26.67
0
0.00
0.00
0.00
1
1.67
3.33
100.00
5
8.33
16.67
62.50
30
50.00

Total 30
50.00
1
1.67
3
5.00
15
25.00
2
3.33
1
1.67
8
13.33
60
100.00
Fisher's Exact Test
Table Probability (P) 1.677E-04
Pr <= P 0.1014

FIGURE 19: Space available category by ethnicity, Site 10

63

TABLE 13: Space available category by ethnicity, Site 11

Site 11: Lower left 2
nd
bicuspid—1
st
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Caucasian 5
8.33
16.67
29.41
3
5.00
10.00
42.86
7
11.67
23.33
63.64
10
16.67
33.33
66.67
2
3.33
6.67
50.00
3
5.00
10.00
50.00
30
50.00

Hispanic 12
20.00
40.00
70.59
4
6.67
13.33
57.14
4
6.67
13.33
36.36
5
8.33
16.67
33.33
2
3.33
6.67
50.00
3
5.00
10.00
50.00
30
50.00

Total 17
28.33
7
11.67
11
18.33
15
25.00
4
6.67
6
10.00
60
100.00
Fisher's Exact Test
Table Probability (P) 2.178E-04
Pr <= P 0.3503

FIGURE 20: Space available category by ethnicity, Site 11

64

TABLE 14: Space available category by ethnicity, Site 12

Site 12: Lower left 1
st
bicuspid—2
nd
bicuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 4
6.67
13.33
33.33
1
1.67
3.33
25.00
3
5.00
10.00
21.43
13
21.67
43.33
81.25
2
3.33
6.67
66.67
1
1.67
3.33
33.33
6
10.00
20.00
75.00
30
50.00

Hispanic 8
13.33
26.67
66.67
3
5.00
10.00
75.00
11
18.33
36.67
78.57
3
5.00
10.00
18.75
1
1.67
3.33
33.33
2
3.33
6.67
66.67
2
3.33
6.67
25.00
30
50.00

Total 12
20.00
4
6.67
14
23.33
16
26.67
3
5.00
3
5.00
8
13.33
60
100.00
Fisher's Exact Test
Table Probability (P) 8.600E-07
Pr <= P 0.0069
* A statistically significant difference between ethnic groups exists at site 12.

FIGURE 21: Space available category by ethnicity, Site 12

65

TABLE 15: Space available category by ethnicity, Site 13

Site 13: Lower left lateral incisor--cuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct D E F N Total
Caucasian 2
3.33
6.67
40.00
3
5.00
10.00
60.00
1
1.67
3.33
100.00
24
40.00
80.00
48.98
30
50.00

Hispanic 3
5.00
10.00
60.00
2
3.33
6.67
40.00
0
0.00
0.00
0.00
25
41.67
83.33
51.02
30
50.00

Total 5
8.33
5
8.33
1
1.67
49
81.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0534
Pr <= P 1.0000

FIGURE 22: Space available category by ethnicity, Site 13

66

TABLE 16: Space available category by ethnicity, Site 14

Site 14: Lower central incisors
Ethnicity
Space
Available
Category
Frequency
Percent
Row Pct
Col Pct N Total
Caucasian 30
50.00
100.00
50.00
30
50.00
Hispanic 30
50.00
100.00
50.00
30
50.00
Total 60
100.00
60
100.00
* No statistically significant differences between ethnic groups exist at site 14. At
this site, 100% of the sites evaluated were part of the N category and therefore
statistics were not computed because site 14 was a constant

FIGURE 23: Space available category by ethnicity, Site 14

67

TABLE 17: Space available category by ethnicity, Site 15

Site 15: Lower right lateral incisor—cuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A D E F N Total
Caucasian 1
1.67
3.33
100.00
3
5.00
10.00
50.00
2
3.33
6.67
33.33
1
1.67
3.33
100.00
23
38.33
76.67
50.00
30
50.00

Hispanic 0
0.00
0.00
0.00
3
5.00
10.00
50.00
4
6.67
13.33
66.67
0
0.00
0.00
0.00
23
38.33
76.67
50.00
30
50.00

Total 1
1.67
6
10.00
6
10.00
1
1.67
46
76.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0209
Pr <= P 0.8909

FIGURE 24: Space available category by ethnicity, Site 15

68

TABLE 18: Space available category by ethnicity, Site 16

Site 16: Lower right 1
st
bicuspid—2
nd
bicuspid
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 3
5.00
10.00
33.33
1
1.67
3.33
100.00
7
11.67
23.33
46.67
5
8.33
16.67
55.56
6
10.00
20.00
75.00
2
3.33
6.67
50.00
6
10.00
20.00
42.86
30
50.00

Hispanic 6
10.00
20.00
66.67
0
0.00
0.00
0.00
8
13.33
26.67
53.33
4
6.67
13.33
44.44
2
3.33
6.67
25.00
2
3.33
6.67
50.00
8
13.33
26.67
57.14
30
50.00

Total 9
15.00
1
1.67
15
25.00
9
15.00
8
13.33
4
6.67
14
23.33
60
100.00
Fisher's Exact Test
Table Probability (P) 2.905E-04
Pr <= P 0.6448

FIGURE 25: Space available category by ethnicity, Site 16

69

TABLE 19: Space available category by ethnicity, Site 17

Site 17: Lower right 2
nd
bicuspid—1
st
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Caucasian 10
16.67
33.33
52.63
1
1.67
3.33
50.00
2
3.33
6.67
33.33
7
11.67
23.33
53.85
7
11.67
23.33
58.33
1
1.67
3.33
33.33
2
3.33
6.67
40.00
30
50.00

Hispanic 9
15.00
30.00
47.37
1
1.67
3.33
50.00
4
6.67
13.33
66.67
6
10.00
20.00
46.15
5
8.33
16.67
41.67
2
3.33
6.67
66.67
3
5.00
10.00
60.00
30
50.00

Total 19
31.67
2
3.33
6
10.00
13
21.67
12
20.00
3
5.00
5
8.33
60
100.00
Fisher's Exact Test
Table Probability (P) 9.554E-04
Pr <= P 0.9611

FIGURE 26: Space available category by ethnicity, Site 17

70

TABLE 20: Space available category by ethnicity, Site 18

Site 18: Lower right 1
st
molar—2
nd
molar
Ethnicity Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Caucasian 6
10.00
20.00
24.00
6
10.00
20.00
85.71
10
16.67
33.33
76.92
4
6.67
13.33
57.14
1
1.67
3.33
50.00
3
5.00
10.00
50.00
30
50.00

Hispanic 19
31.67
63.33
76.00
1
1.67
3.33
14.29
3
5.00
10.00
23.08
3
5.00
10.00
42.86
1
1.67
3.33
50.00
3
5.00
10.00
50.00
30
50.00

Total 25
41.67
7
11.67
13
21.67
7
11.67
2
3.33
6
10.00
60
100.00
Fisher's Exact Test
Table Probability (P) 4.197E-06
Pr <= P 0.0065
* A statistically significant difference between ethnic groups exists at site 18.

FIGURE 27: Space available category by ethnicity, Site 18

71

COMPARISON OF SITES MEASURED: MALE VS. FEMALE
For comparison of males and females at each site, since most of the cells
have expected counts less than 5, the Chi-square test is not a valid statistic.
Therefore, the Fisher Exact test was used instead to test differences at each site
between different gender groups. There is a statistically significant difference in
space availability between males and females at site 12, the space between lower left
1
st
and 2
nd
bicuspids, (p-value=0.0266) and site 18, to the space between the lower
right 1
st
and 2
nd
molars, (p-value=0.0209). These p-values indicate that the
difference between gender groups at these sites is less significant than the difference
between ethnic groups at these sites. At sites 12 and 18, females had space available
more coronally than males.

72

TABLE 21: Space available category by gender, Site 1

Site 1: Upper right 1
st
molar—2
nd
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct B C D E F N Total
Female 1
1.67
3.33
100.00
1
1.67
3.33
33.33
1
1.67
3.33
100.00
4
6.67
13.33
80.00
1
1.67
3.33
100.00
22
36.67
73.33
44.90
30
50.00

Male 0
0.00
0.00
0.00
2
3.33
6.67
66.67
0
0.00
0.00
0.00
1
1.67
3.33
20.00
0
0.00
0.00
0.00
27
45.00
90.00
55.10
30
50.00

Total 1
1.67
3
5.00
1
1.67
5
8.33
1
1.67
49
81.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0063
Pr <= P 0.3372

FIGURE 28: Space available category by gender, Site 1

73

TABLE 22: Space available category by gender, Site 2

Site 2: Upper right 1
st
bicuspid—1
st
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 3
5.00
10.00
50.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
8
13.33
26.67
61.54
12
20.00
40.00
54.55
1
1.67
3.33
50.00
6
10.00
20.00
46.15
30
50.00

Male 3
5.00
10.00
50.00
1
1.67
3.33
100.00
3
5.00
10.00
100.00
5
8.33
16.67
38.46
10
16.67
33.33
45.45
1
1.67
3.33
50.00
7
11.67
23.33
53.85
30
50.00

Total 6
10.00
1
1.67
3
5.00
13
21.67
22
36.67
2
3.33
13
21.67
60
100.00
Fisher's Exact Test
Table Probability (P) 4.830E-04
Pr <= P 0.6072

FIGURE 29: Space available category by gender, Site 2

74

TABLE 23: Space available category by gender, Site 3

Site 3: Upper right 1
st
bicuspid—2
nd
bicuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Female 3
5.00
10.00
50.00
3
5.00
10.00
60.00
3
5.00
10.00
60.00
8
13.33
26.67
61.54
1
1.67
3.33
25.00
12
20.00
40.00
44.44
30
50.00

Male 3
5.00
10.00
50.00
2
3.33
6.67
40.00
2
3.33
6.67
40.00
5
8.33
16.67
38.46
3
5.00
10.00
75.00
15
25.00
50.00
55.56
30
50.00

Total 6
10.00
5
8.33
5
8.33
13
21.67
4
6.67
27
45.00
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0015
Pr <= P 0.8260

FIGURE 30: Space available category by gender, Site 3

75

TABLE 24: Space available category by gender, Site 4

Site 4: Upper right lateral incisor—cuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 0
0.00
0.00
0.00
0
0.00
0.00
0.00
3
5.00
10.00
60.00
2
3.33
6.67
33.33
7
11.67
23.33
50.00
0
0.00
0.00
0.00
18
30.00
60.00
56.25
30
50.00

Male 1
1.67
3.33
100.00
1
1.67
3.33
100.00
2
3.33
6.67
40.00
4
6.67
13.33
66.67
7
11.67
23.33
50.00
1
1.67
3.33
100.00
14
23.33
46.67
43.75
30
50.00

Total 1
1.67
1
1.67
5
8.33
6
10.00
14
23.33
1
1.67
32
53.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0021
Pr <= P 0.7244

FIGURE 31: Space available category by gender, Site 4

76

TABLE 25: Space available category by gender, Site 5

Site 5: Upper central incisors
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Female 1
1.67
3.33
50.00
5
8.33
16.67
62.50
6
10.00
20.00
50.00
6
10.00
20.00
37.50
1
1.67
3.33
50.00
11
18.33
36.67
55.00
30
50.00

Male 1
1.67
3.33
50.00
3
5.00
10.00
37.50
6
10.00
20.00
50.00
10
16.67
33.33
62.50
1
1.67
3.33
50.00
9
15.00
30.00
45.00
30
50.00

Total 2
3.33
8
13.33
12
20.00
16
26.67
2
3.33
20
33.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0024
Pr <= P 0.9012

FIGURE 32: Space available category by gender, Site 5

77

TABLE 26: Space available category by gender, Site 6

Site 6: Upper left lateral incisor—cuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct C D E F N Total
Female 4
6.67
13.33
57.14
2
3.33
6.67
20.00
5
8.33
16.67
71.43
1
1.67
3.33
20.00
18
30.00
60.00
58.06
30
50.00

Male 3
5.00
10.00
42.86
8
13.33
26.67
80.00
2
3.33
6.67
28.57
4
6.67
13.33
80.00
13
21.67
43.33
41.94
30
50.00

Total 7
11.67
10
16.67
7
11.67
5
8.33
31
51.67
60
100.00
Fisher's Exact Test
Table Probability (P) 2.884E-04
Pr <= P 0.1097

FIGURE 33: Space available category by gender, Site 6

78

TABLE 27: Space available category by gender, Site 7

Site 7: Upper left 1
st
bicuspid—2
nd
bicuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Female 4
6.67
13.33
57.14
2
3.33
6.67
40.00
2
3.33
6.67
40.00
5
8.33
16.67
50.00
2
3.33
6.67
50.00
15
25.00
50.00
51.72
30
50.00

Male 3
5.00
10.00
42.86
3
5.00
10.00
60.00
3
5.00
10.00
60.00
5
8.33
16.67
50.00
2
3.33
6.67
50.00
14
23.33
46.67
48.28
30
50.00

Total 7
11.67
5
8.33
5
8.33
10
16.67
4
6.67
29
48.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0035
Pr <= P 1.0000

FIGURE 34: Space available category by gender, Site 7

79

TABLE 28: Space available category by gender, Site 8

Site 8: Upper left 2
nd
bicuspid—1
st
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 7
11.67
23.33
58.33
0
0.00
0.00
0.00
2
3.33
6.67
100.00
4
6.67
13.33
50.00
7
11.67
23.33
41.18
3
5.00
10.00
50.00
7
11.67
23.33
50.00
30
50.00

Male 5
8.33
16.67
41.67
1
1.67
3.33
100.00
0
0.00
0.00
0.00
4
6.67
13.33
50.00
10
16.67
33.33
58.82
3
5.00
10.00
50.00
7
11.67
23.33
50.00
30
50.00

Total 12
20.00
1
1.67
2
3.33
8
13.33
17
28.33
6
10.00
14
23.33
60
100.00
Fisher's Exact Test
Table Probability (P) 6.258E-04
Pr <= P 0.8132

FIGURE 35: Space available category by gender, Site 8

80

TABLE 29: Space available category by gender, Site 9

Site 9: Upper left 1
st
molar—2
nd
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A D E F N Total
Female 1
1.67
3.33
100.00
2
3.33
6.67
100.00
4
6.67
13.33
50.00
1
1.67
3.33
50.00
22
36.67
73.33
46.81
30
50.00

Male 0
0.00
0.00
0.00
0
0.00
0.00
0.00
4
6.67
13.33
50.00
1
1.67
3.33
50.00
25
41.67
83.33
53.19
30
50.00

Total 1
1.67
2
3.33
8
13.33
2
3.33
47
78.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0176
Pr <= P 0.7300

FIGURE 36: Space available category by gender, Site 9

81

TABLE 30: Space available category by gender, Site 10

Site 10: Lower left 1
st
molar—2
nd
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 16
26.67
53.33
53.33
0
0.00
0.00
0.00
1
1.67
3.33
33.33
9
15.00
30.00
60.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
4
6.67
13.33
50.00
30
50.00

Male 14
23.33
46.67
46.67
1
1.67
3.33
100.00
2
3.33
6.67
66.67
6
10.00
20.00
40.00
2
3.33
6.67
100.00
1
1.67
3.33
100.00
4
6.67
13.33
50.00
30
50.00

Total 30
50.00
1
1.67
3
5.00
15
25.00
2
3.33
1
1.67
8
13.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0013
Pr <= P 0.6540

FIGURE 37: Space available category by gender, Site 10

82

TABLE 31: Space available category by gender, Site 11

Site 11: Lower left 2
nd
bicuspid—1
st
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Female 12
20.00
40.00
70.59
2
3.33
6.67
28.57
5
8.33
16.67
45.45
7
11.67
23.33
46.67
1
1.67
3.33
25.00
3
5.00
10.00
50.00
30
50.00

Male 5
8.33
16.67
29.41
5
8.33
16.67
71.43
6
10.00
20.00
54.55
8
13.33
26.67
53.33
3
5.00
10.00
75.00
3
5.00
10.00
50.00
30
50.00

Total 17
28.33
7
11.67
11
18.33
15
25.00
4
6.67
6
10.00
60
100.00
Fisher's Exact Test
Table Probability (P) 2.613E-04
Pr <= P 0.3989

FIGURE 38: Space available category by gender, Site 11

83

TABLE 32: Space available category by gender, Site 12

Site 12: Lower left 1
st
bicuspid—2
nd
bicuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 7
11.67
23.33
58.33
2
3.33
6.67
50.00
11
18.33
36.67
78.57
5
8.33
16.67
31.25
0
0.00
0.00
0.00
0
0.00
0.00
0.00
5
8.33
16.67
62.50
30
50.00

Male 5
8.33
16.67
41.67
2
3.33
6.67
50.00
3
5.00
10.00
21.43
11
18.33
36.67
68.75
3
5.00
10.00
100.00
3
5.00
10.00
100.00
3
5.00
10.00
37.50
30
50.00

Total 12
20.00
4
6.67
14
23.33
16
26.67
3
5.00
3
5.00
8
13.33
60
100.00
Fisher's Exact Test
Table Probability (P) 3.578E-06
Pr <= P 0.0266
* A statistically significant difference between gender groups exists at site 12.

FIGURE 39: Space available category by gender, Site 12

84

TABLE 33: Space available category by gender, Site 13

Site 13: Lower left lateral incisor--cuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct D E F N Total
Female 4
6.67
13.33
80.00
3
5.00
10.00
60.00
0
0.00
0.00
0.00
23
38.33
76.67
46.94
30
50.00

Male 1
1.67
3.33
20.00
2
3.33
6.67
40.00
1
1.67
3.33
100.00
26
43.33
86.67
53.06
30
50.00

Total 5
8.33
5
8.33
1
1.67
49
81.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0247
Pr <= P 0.4738

FIGURE 40: Space available category by gender, Site 13

85

TABLE 34: Space available category by gender, Site 14

Site 14: Lower central incisors
Gender
Space
Available
Category
Frequency
Percent
Row Pct
Col Pct N Total
Female 30
50.00
100.00
50.00
30
50.00
Male 30
50.00
100.00
50.00
30
50.00
Total 60
100.00
60
100.00
* No statistically significant differences between gender groups exist at site 14. At
this site, 100% of the sites evaluated were part of the N category and therefore
statistics were not computed because site 14 was a constant

FIGURE 41: Space available category by gender, Site 14

86

TABLE 35: Space available category by gender, Site 15

Site 15: Lower right lateral incisor—cuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A D E F N Total
Female 1
1.67
3.33
100.00
2
3.33
6.67
33.33
1
1.67
3.33
16.67
1
1.67
3.33
100.00
25
41.67
83.33
54.35
30
50.00

Male 0
0.00
0.00
0.00
4
6.67
13.33
66.67
5
8.33
16.67
83.33
0
0.00
0.00
0.00
21
35.00
70.00
45.65
30
50.00

Total 1
1.67
6
10.00
6
10.00
1
1.67
46
76.67
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0053
Pr <= P 0.1657

FIGURE 42: Space available category by gender, Site 15

87

TABLE 36: Space available category by gender, Site 16

Site 16: Lower right 1
st
bicuspid—2
nd
bicuspid
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 3
5.00
10.00
33.33
1
1.67
3.33
100.00
10
16.67
33.33
66.67
2
3.33
6.67
22.22
3
5.00
10.00
37.50
2
3.33
6.67
50.00
9
15.00
30.00
64.29
30
50.00

Male 6
10.00
20.00
66.67
0
0.00
0.00
0.00
5
8.33
16.67
33.33
7
11.67
23.33
77.78
5
8.33
16.67
62.50
2
3.33
6.67
50.00
5
8.33
16.67
35.71
30
50.00

Total 9
15.00
1
1.67
15
25.00
9
15.00
8
13.33
4
6.67
14
23.33
60
100.00
Fisher's Exact Test
Table Probability (P) 5.165E-05
Pr <= P 0.2221

FIGURE 43: Space available category by gender, Site 16

88

TABLE 37: Space available category by gender, Site 17

Site 17: Lower right 2
nd
bicuspid—1
st
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A B C D E F N Total
Female 10
16.67
33.33
52.63
1
1.67
3.33
50.00
2
3.33
6.67
33.33
7
11.67
23.33
53.85
6
10.00
20.00
50.00
1
1.67
3.33
33.33
3
5.00
10.00
60.00
30
50.00

Male 9
15.00
30.00
47.37
1
1.67
3.33
50.00
4
6.67
13.33
66.67
6
10.00
20.00
46.15
6
10.00
20.00
50.00
2
3.33
6.67
66.67
2
3.33
6.67
40.00
30
50.00

Total 19
31.67
2
3.33
6
10.00
13
21.67
12
20.00
3
5.00
5
8.33
60
100.00
Fisher's Exact Test
Table Probability (P) 0.0011
Pr <= P 0.9785

FIGURE 44: Space available category by gender, Site 17

89

TABLE 38: Space available category by gender, Site 18

Site 18: Lower right 1
st
molar—2
nd
molar
Gender Space Available Category
Frequency
Percent
Row Pct
Col Pct A C D E F N Total
Female 13
21.67
43.33
52.00
0
0.00
0.00
0.00
9
15.00
30.00
69.23
5
8.33
16.67
71.43
0
0.00
0.00
0.00
3
5.00
10.00
50.00
30
50.00

Male 12
20.00
40.00
48.00
7
11.67
23.33
100.00
4
6.67
13.33
30.77
2
3.33
6.67
28.57
2
3.33
6.67
100.00
3
5.00
10.00
50.00
30
50.00

Total 25
41.67
7
11.67
13
21.67
7
11.67
2
3.33
6
10.00
60
100.00
Fisher's Exact Test
Table Probability (P) 1.320E-05
Pr <= P 0.0209
* A statistically significant difference between gender groups exists at site 18.

FIGURE 45: Space available category by gender, Site 18

90

DESCRIPTIVE STATISTICS: OVERALL TRENDS WITHIN DATA
In order to analyze overall trends within the data, space available categories
were reassigned numerical values from 0 to 6, with 0 indicating that there was
always 3 mm of interradicular space and 6 indicating that there was never 3 mm of
space. A general linear model adjusted for site was used to evaluate the “average”
space available category according to gender. There is a statistically significant
difference in space available category by each site (F=34.86, p<.0001). Least
squares means for space available category for Hispanic patients was 3.88 and for
Caucasians was 4.15 (site-adjusted F = 6.89, p = .0088), indicating that Hispanics
had significantly more space available than Caucasians, and that this space was
available more coronally in Hispanic patients than in Caucasian patients. Least
squares means for space available category for female patients was 3.97 and for male
was 4.06 (site-adjusted F = .72, p = .39), indicating that there was no significant
difference between males and females. Least squares means for space available
category for upper teeth was 4.48 and for lower teeth was 3.55 (F =55.12, p<.0001),
showing a highly significant difference between upper and lower teeth. Least
squares means for space available category for right teeth (site=1,2,3,4,15,16,17,18)
was 4.09 and for left teeth (6,7,8,9,10,11,12,13) was 3.92 (F =1.69, p=.19), showing
no significant difference between left and right teeth. (Figure 46)

91

FIGURE 46: Least Squares Means for Space Available Category comparing
Ethnicity, Gender, Upper vs. Lower sites, and Right vs. Left sites
_

*Significant differences existed between ethnicity and between upper vs. lower teeth.
92

Chapter 6: DISCUSSION
The purpose of this study was to determine if sites with adequate space
between roots for miniscrew placement were likely to be located coronally enough
for miniscrew insertion in attached gingiva. Additionally, we wanted to determine if
any significant differences existed between gender and ethnic groups, as well as
between left vs. right and upper vs. lower teeth.
We did not find any significant differences between gender and ethnic groups
when comparing the 7 categories of space availability, except at sites 12, between
lower left 1
st
and 2
nd
bicuspids, and 18, between the lower right 1
st
and 2
nd
molars.
At these two sites, significant differences existed between both gender and ethnic
groups, however, differences between ethnic groups was more significant than
between gender groups. At these sites, we found that Hispanics were likely to have
space available more coronally than Caucasians, and females were likely to have
space available more coronally than males. While there are no previous studies that
have compared the amount of interradicular space availability for miniscrew
placement between gender or ethnic groups, perhaps these differences can be
explained by previous studies evaluating gender and ethnic differences in tooth size.
Puri et al
[94]
found that larger mesiodistal crown dimensions were associated with
increased crowding. According to studies conducted on gender differences in tooth
size, males generally have larger teeth than females.
[65, 72, 73, 75, 95]
Perhaps this could
result in more crowding and less interradicular space in males than females.
However, many researchers are now recognizing that sexual dimorphism is
93

becoming less pronounced in modern populations,
[58, 96]
making it difficult to
attribute gender differences in interradicular space availability to one factor.
Ethnic differences between Caucasians and Hispanics in tooth size have not
been evaluated as often as gender differences or ethnic differences between
Caucasians and other ethnic groups. Upatham
[67]
found that Hispanic patients had
significantly larger incisors and mandibular cuspids, but significantly smaller
maxillary cuspids and 2
nd
bicuspids. Therefore, differences in interradicular space
availability cannot be explained solely by tooth size differences between Hispanic
and Caucasian patients. This indicates that the amount of interradicular space
available is influenced by multiple factors.
When analyzing the general trends for space availability, significant
differences existed between sites, between upper and lower teeth, and between
ethnicities. Posterior mandibular sites were significantly more likely to have 3 mm
of space available for the placement of miniscrews, and these sites were likely to be
located more coronally than maxillary sites. Hispanic patients were significantly
more likely to have 3 mm of space available for the placement of miniscrews, and
these sites were likely to be located more coronally than in Caucasian patients.
Posterior sites in the mandible between the mandibular 2
nd
bicuspids to 2
nd

molars had the most interradicular space, and these spaces were located most
coronally, making them ideal sites for miniscrew placement based on the criteria of
bone stock availability within attached gingiva. These findings agree with those
found previously by Schnelle et al
[1]
, who found that the most space for miniscrew
94

placement existed mesial and distal to the mandibular 1
st
molars.
We found that the most favorable maxillary site for miniscrew placement was
either between maxillary 2
nd
bicuspids and 1
st
molars, or between maxillary central
incisors. However, 3 mm of space at these sites became available more apically, and
insertion of a miniscrew through attached gingiva at these sites seems unlikely.
Schnelle et al
[1]
also stated that the maxillary sites with enough bone for miniscrew
placement existed mesial to the maxillary 1
st
molars, and that this space was not
likely to be located in attached gingiva.
The sites that were least likely to have space available for miniscrew
insertion were in the anterior mandible, between lower cuspids and incisors, and
between upper 1
st
and 2
nd
molars. These spaces typically had very little
interradicular space, indicating that these sites should be avoided when selecting a
site for miniscrew placement. According to our findings, the site between lower
central incisors never had enough interradicular space. Therefore, miniscrew
implants should never be placed here. Very little interradicular space was found
between maxillary 1
st
and 2
nd
molars because of root divergence of the maxillary
molars and because the maxillary 2
nd
molar appeared to erupt down the distal root of
the 1
st
molar.
Interestingly, while some studies have advocated the interradicular space
between maxillary 1
st
and 2
nd
molars as adequate site for miniscrew placement
[23]
, we
found that this site typically did not have enough interradicular space to support a
miniscrew. However, Poggio et al
[19]
indicated that the usefulness of this site for
95

miniscrew placement is not due to sufficient interradicular space, but rather
increased thickness of buccal bone over the underlying roots.
[19]

Schnelle et al,
[1]
reported that the only sites they believed to have bone stock
located in areas that would be covered by attached gingiva were sites distal to the
mandibular 1
st
molars. They stated that at this site, placement of a miniscrew ~2.5
mm from the CEJ would likely be in the attached gingiva of healthy patients. They
concluded that adequate bone for miniscrew placement at other sites was located
more than halfway down the root, which they believed would be covered with
movable mucosa. Our study also found the site between mandibular 1
st
and 2
nd

molars had the most coronally located bone stock which would probably allow the
placement of a miniscrew through attached gingiva.
Other possible insertion sites with enough interradicular space existed mesial
to the maxillary and mandibular 1
st
molars, as well as between maxillary central
incisors. However, the bone stock at these sites became available more apically,
which would make miniscrew insertion through attached gingiva less likely.
However, it must also be understood that adequate bone stock for miniscrew
insertion that is located apical to the level of attached gingiva could still theoretically
allow for miniscrew insertion through attached gingiva. This is possible because
most miniscrew placement protocols suggest that the miniscrew is inserted in a
diagonal or oblique direction, at an angle to the long axes of the teeth. This angle
typically ranges from 10-20° for the mandible and 30-60° for the maxilla.
Perpendicular insertion is only recommended for sites where there is plenty of
96

space available to avoid damage to adjacent roots.
According to the findings of this study, each site should be carefully
evaluated radiographically and clinically by the clinician prior to miniscrew
placement. For each patient, the amount of attached gingiva available will be
different. If the site selected for miniscrew placement will not allow the miniscrew
to be inserted through attached gingiva, then design modifications in the miniscrew
head or with miniscrew attachments will be necessary.

97

Chapter 7: ASSUMPTIONS
There were several assumptions made for this study. First, that the patient
pool at the University of Southern California, Graduate Orthodontics Clinic is
representative of the general population in Southern California. Second, that all
measurements made were accurate and reproducible. Third, that any distortion the
images acquired from the NewTom® 9000 were statistically insignificant. Forth,
that patients were correctly assigned to their respective ethnic and gender groups.

98

Chapter 8: LIMITATIONS
There were several potential limitations to this study. First, there was a
limited number of dicom data from NewTom® scans in the department archives that
met study inclusion criteria. Second, subjects consisted only of orthodontic patients,
without controls from the general population. Third, any measurements made were
subject to human error. Fourth, our study was limited by the fact that the location of
the mucogingival junction is highly variable and cannot be accurately predicted.

99

Chapter 9: SUMMARY
While many studies have investigated which interradicular sites in the mouth
have enough space between roots to support the insertion of a miniscrew implant,
many of these studies never studied differences between gender or ethnic groups, and
they did not relate their measurements to the location of the mucogingival junction.
Although it is widely known that insertion of the miniscrew through attached gingiva
is strongly correlated with the successful retention of the miniscrew implant, little
has been done to try and correlate which interradicular sites have both enough bone
and attached gingiva to allow for successful miniscrew placement. This study sought
to investigate which buccoalveolar sites would allow miniscrew placement in
attached gingiva.

100

Chapter 10: CONCLUSIONS
1. Sufficient bone stock for miniscrew placement (3 mm) that was located
coronally enough for miniscrew insertion through attached gingiva was most
likely to be found between mandibular 1
st
and 2
nd
molars.
2. Other sites that had enough bone stock for miniscrew placement, but this
bone stock was located more apically were:
a. Between mandibular 2
nd
bicuspids and 1
st
molars
b. Between mandibular 1
st
and 2
nd
bicuspids
c. Between maxillary 2
nd
bicuspids and 1
st
molars
d. Between maxillary centrals
3. Sites without adequate bone stock for miniscrew placement were:
a. Between maxillary 1
st
and 2
nd
molars
b. Between mandibular centrals
c. Between mandibular lateral incisors and cuspids.
4. Significant differences existed in bone stock availability by each site
5. Significant differences existed between gender and ethnic groups at sites 12,
between lower left bicuspids, and 18, between lower right molars
101

a. At these sites, ethnic differences were more significant than gender
differences
6. When general trends of space availability were analyzed, significant
differences existed between ethnic groups and between upper and lower sites.
No significant differences were found between gender groups and between
left vs. right sides.

102

BIBLIOGRAPHY

96. Alt, K.W., et al., Comparative anatomy of teeth from past to present. Indian J
Dent Res, 1997. 8(1): p. 5-8.

82. Ash, M.M. and S.J. Nelson, Wheeler's dental anatomy, physiology, and
occlusion. 8th ed. 2003, Philadelphia: Saunders. xiv, 523 p.

42. Asscherickx, K., et al., Root repair after injury from mini-screw. Clin Oral
Implants Res, 2005. 16(5): p. 575-8.

59. Bailit, H.L., Dental variation among populations. An anthropologic view.
Dent Clin North Am, 1975. 19(1): p. 125-39.

20. Berens, A., D. Wiechmann, and R. Dempf, Mini- and micro-screws for
temporary skeletal anchorage in orthodontic therapy. J Orofac Orthop, 2006.
67(6): p. 450-8.

35. Borbely, P., et al., Primary loading of palatal implants for orthodontic
anchorage - A pilot animal study. J Craniomaxillofac Surg, 2007.

54. Bowers, G.M., A study of the width of the attached gingiva. J Periodontol,
1963;34:201-209.

78. Brace, C.L. and M. Nagai, Japanese tooth size: past and present. Am J Phys
Anthropol, 1982. 59(4): p. 399-411.

58. Brace, C.L. and P.E. Mahler, Post-Pleistocene changes in the human
dentition. Am J Phys Anthropol, 1971. 34(2): p. 191-203.

83. Brand, R.W. and D.E. Isselhard, Anatomy of orofacial structures. 7th ed.
2003, St. Louis, Mo.: Mosby. xiii, 567 p.

34. Buchter, A., et al., Load-related implant reaction of mini-implants used for
orthodontic anchorage. Clin Oral Implants Res, 2005. 16(4): p. 473-9.

79. Buschang, P.H. and J.D. Shulman, Incisor crowding in untreated persons 15-
50 years of age: United States, 1988-1994. Angle Orthod, 2003. 73(5): p.
502-8.

103
57. Calcagno, J.M. and K.R. Gibson, Human dental reduction: natural selection
or the probable mutation effect. Am J Phys Anthropol, 1988. 77(4): p. 505-
17.

44. Carano, A., et al., Mechanical properties of three different commercially
available miniscrews for skeletal anchorage. Prog Orthod, 2005. 6(1): p. 82-
97.

23. Carano, A., et al., Clinical applications of the Mini-Screw-Anchorage-System
(M.A.S.) in the maxillary alveolar bone. Prog Orthod, 2004. 5(2): p. 212-35.

59. Cevidanes, L.H., M.A. Styner, and W.R. Proffit, Image analysis and
superimposition of 3-dimensional cone-beam computed tomography models.
Am J Orthod Dentofacial Orthop, 2006. 129(5): p. 611-8.

43. Chen, Y.H., et al., Root contact during insertion of miniscrews for
orthodontic anchorage increases the failure rate: an animal study. Clin Oral
Implants Res, 2008. 19(1): p. 99-106.

46. Chen, Y.J., et al., A retrospective analysis of the failure rate of three different
orthodontic skeletal anchorage systems. Clin Oral Implants Res, 2007. 18(6):
p. 768-75.

52. Cheng, S.J., et al., A prospective study of the risk factors associated with
failure of mini-implants used for orthodontic anchorage. Int J Oral
Maxillofac Implants, 2004. 19(1): p. 100-6.

51. Cho, H.J., Clinical applications of mini-implants as orthodontic anchorage
and the peri-implant tissue reaction upon loading. J Calif Dent Assoc, 2006.
34(10): p. 813-20.

40. Coburn, D.G., D.W. Kennedy, and S.C. Hodder, Complications with
intermaxillary fixation screws in the management of fractured mandibles. Br
J Oral Maxillofac Surg, 2002. 40(3): p. 241-3.

14. Cope, J., Temporary anchorage devices in orthodontics: a paradigm shift.
Semin Orthod 2005;11:3-9.

29. Cornelis, M.A., et al., Systematic review of the experimental use of temporary
skeletal anchorage devices in orthodontics. Am J Orthod Dentofacial Orthop,
2007. 131(4 Suppl): p. S52-8.

15. Costa, A., M. Maric, and P. Danesino, Comparison between two orthodontic
skeletal anchorage devices: osseointegrated implants and miniscrews -
Medical-Legal Considerations. Prog Orthod, 2006. 7(1): p. 24-31.

27. Deguchi, T., et al., The use of small titanium screws for orthodontic
anchorage. J Dent Res, 2003. 82(5): p. 377-81.
104

61. Dempsey, P.J. and G.C. Townsend, Genetic and environmental contributions
to variation in human tooth size. Heredity, 2001. 86(Pt 6): p. 685-93.

41. Fabbroni, G., et al., Transalveolar screws and the incidence of dental
damage: a prospective study. Int J Oral Maxillofac Surg, 2004. 33(5): p. 442-
6.

49. Forna, N., et al., Peri-implantitis. Rev Med Chir Soc Med Nat Iasi, 1998.
102(3-4): p. 74-9.

36. Freire, J.N., et al., Histomorphologic and histomophometric evaluation of
immediately and early loaded mini-implants for orthodontic anchorage. Am
J Orthod Dentofacial Orthop, 2007. 131(6): p. 704 e1-9.

3. Freudenthaler, J.W., R. Haas, and H.P. Bantleon, Bicortical titanium screws
for critical orthodontic anchorage in the mandible: a preliminary report on
clinical applications. Clin Oral Implants Res, 2001. 12(4): p. 358-63.

65. Garn, S.M., et al., Genetic control of sexual dimorphism in tooth size. J Dent
Res, 1967. 46(5): p. 963-72.

75. Garn, S.M., A.B. Lewis, and R.S. Kerewsky, The relationship between sexual
dimorphism in tooth size and body size as studied within families. Arch Oral
Biol, 1967. 12(2): p. 299-301.

95. Garn, S.M., A.B. Lewis, and R.S. Kerewsky, Sex difference in tooth shape. J
Dent Res, 1967. 46(6): p. 1470.

76. Garn, S.M., A.B. Lewis, and R.S. Kerewsky, The magnitude and implications
of the relationship between tooth size and body size. Arch Oral Biol, 1968.
13(1): p. 129-31.

64. Garn, S.M., P.E. Cole, and W.L. Van Alstine, Sex discriminatory
effectiveness using combinations of root lengths and crown diameters. Am J
Phys Anthropol, 1978. 50(1): p. 115-8.

9. Gianelly, A.A. and H.M. Goldman, Biologic basis of orthodontics [by]
Anthony A. Gianelly [and] Henry M. Goldman. 1971, Philadelphia,: Lea &
Febiger. xvii, 414 p.

73. Gillen, R.J., et al., An analysis of selected normative tooth proportions. Int J
Prosthodont, 1994. 7(5): p. 410-7.

105

81. Gimlen, A. Comparative study of Caucasian and Hispanic Mandibular
Clinical Arch Forms. Thesis presented for Master of Science Craniofacial
Biology, University of Southern California; May, 2007.

66. Harris, A.M., Rathbun, T.A. Ethnic differences in the apportionment of tooth
sizes. Advances in Dental Anthropology, 1991:121-142.

55. Haydenblit, R., Dental variation among four prehispanic Mexican
populations. Am J Phys Anthropol, 1996. 100(2): p. 225-46.

6. Heymann, G.C. and J.F. Tulloch, Implantable devices as orthodontic
anchorage: a review of current treatment modalities. J Esthet Restor Dent,
2006. 18(2): p. 68-79; discussion 80.

60. Hillson, S., Archaeology and the study of teeth. Endeavour, 1986. 10(3): p.
145-9.

2. Huang, L.H., J.L. Shotwell, and H.L. Wang, Dental implants for orthodontic
anchorage. Am J Orthod Dentofacial Orthop, 2005. 127(6): p. 713-22.

12. Kanomi, R., Mini-implant for orthodontic anchorage. J Clin Orthod, 1997.
31(11): p. 763-7.

70. Keene, H.J., Mesiodistal crown diameters of permanent teeth in male
American Negroes. Am J Orthod, 1979. 76(1): p. 95-9.

80. Kennedy, D. Early Eruption of Permanent Dentition in Hispanic
Adolescents. Thesis presented for Master of Science Craniofacial Biology,
University of Southern California; May, 2006.

32. Kim, H., T.K. Kim, and S.J. Lee, Convenient removal of orthodontic mini-
implants. Am J Orthod Dentofacial Orthop, 2007. 131(4 Suppl): p. S90-1.

50. Kozlovsky, A., et al., Impact of implant overloading on the peri-implant bone
in inflamed and non-inflamed peri-implant mucosa. Clin Oral Implants Res,
2007. 18(5): p. 601-10.

39. Kravitz, N.D. and B. Kusnoto, Risks and complications of orthodontic
miniscrews. Am J Orthod Dentofacial Orthop, 2007. 131(4 Suppl): p. S43-51.

48. Kuroda, S., et al., Root proximity is a major factor for screw failure in
orthodontic anchorage. Am J Orthod Dentofacial Orthop, 2007. 131(4
Suppl): p. S68-73.

106

21. Kyung, H.M., et al., Development of orthodontic micro-implants for intraoral
anchorage. J Clin Orthod, 2003. 37(6): p. 321-8; quiz 314.

62. Lascala, C.A., J. Panella, and M.M. Marques, Analysis of the accuracy of
linear measurements obtained by cone beam computed tomography (CBCT-
NewTom). Dentomaxillofac Radiol, 2004. 33(5): p. 291-4.

77. Lavelle, C.L., Relationship between tooth and long bone size. Am J Phys
Anthropol, 1977. 46(3): p. 423-5.

69. Lavelle, C.L., Maxillary and mandibular tooth size in different racial groups
and in different occlusal categories. Am J Orthod, 1972. 61(1): p. 29-37.

53. Lindhe, J., A.D. Haffajee, and S.S. Socransky, Progression of periodontal
disease in adult subjects in the absence of periodontal therapy. J Clin
Periodontol, 1983. 10(4): p. 433-42.

11. Linkow, L.I., The endosseous blade implant and its use in orthodontics. Int J
Orthod, 1969. 7(4): p. 149-54.

22. Ludwig, B., et al., Radiological Location Monitoring in Skeletal Anchorage:
Introduction of a Positioning Guide. J Orofac Orthop, 2008. 69(1): p. 59-65.

63. Lundstrom, A. Size of teeth and jaws in twins.. Br Dent J 1964; 117: p 321-
326.

24. Luzi, C., Verna, C., and B. Melsen, A prospective clinical investigation of the
failure rate of immediately loaded mini-implants used for orthodontic
anchorage. Prog Orthod, 2007. 8(1): p. 192-201.

63. Marmulla, R., et al., Geometric accuracy of the NewTom 9000 Cone Beam
CT. Dentomaxillofac Radiol, 2005. 34(1): p. 28-31.

45. Melsen, B.,Verna, C., Miniscrew Implants: the Aarhus Anchorage System.
Semin Orthod, 2005.; 11:24-31.

45. Melsen, B., Mini-implants: Where are we? J Clin Orthod, 2005. 39(9): p.
539-47; quiz 531-2.

16. Melsen, B. and A. Costa, Immediate loading of implants used for orthodontic
anchorage. Clin Orthod Res, 2000. 3(1): p. 23-8.

71. Merz, M.L., et al., Tooth diameters and arch perimeters in a black and a
white population. Am J Orthod Dentofacial Orthop, 1991. 100(1): p. 53-8.
107

30. Miyawaki, S., et al., Factors associated with the stability of titanium screws
placed in the posterior region for orthodontic anchorage. Am J Orthod
Dentofacial Orthop, 2003. 124(4): p. 373-8.

47. Motoyoshi, M., M. Matsuoka, and N. Shimizu, Application of orthodontic
mini-implants in adolescents. Int J Oral Maxillofac Surg, 2007. 36(8): p. 695-
9.

57. Mozzo, P., et al., A new volumetric CT machine for dental imaging based on
the cone-beam technique: preliminary results. Eur Radiol, 1998. 8(9): p.
1558-64.

17. Ohmae, M., et al., A clinical and histological evaluation of titanium mini-
implants as anchors for orthodontic intrusion in the beagle dog. Am J Orthod
Dentofacial Orthop, 2001. 119(5): p. 489-97.

7. Ong, M.M. and H.L. Wang, Periodontic and orthodontic treatment in adults.
Am J Orthod Dentofacial Orthop, 2002. 122(4): p. 420-8.

62. Osborne, R.H., S.L. Horowitz, and F.V. De George, Genetic variation in
tooth dimensions: a twin study of the permanent anterior teeth. Am J Hum
Genet, 1958. 10(3): p. 350-6.

37. Owens, S.E., et al., Experimental evaluation of tooth movement in the beagle
dog with the mini-screw implant for orthodontic anchorage. Am J Orthod
Dentofacial Orthop, 2007. 132(5): p. 639-46.

8. Papadopoulos, M.A. and F. Tarawneh, The use of miniscrew implants for
temporary skeletal anchorage in orthodontics: a comprehensive review. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod, 2007. 103(5): p. e6-15.

60. Peck, J.L., et al., Mesiodistal root angulation using panoramic and cone
beam CT. Angle Orthod, 2007. 77(2): p. 206-13.

19. Poggio, P.M., et al., "Safe zones": a guide for miniscrew positioning in the
maxillary and mandibular arch. Angle Orthod, 2006. 76(2): p. 191-7.

5. Proffit, W.R., H.W. Fields, and D.M. Sarver, Contemporary orthodontics. 4th
ed. 2007, St. Louis, Mo.: Mosby Elsevier. xii, 751 p.

94. Puri, N., et al., Biometric study of tooth size in normal, crowded, and spaced
permanent dentitions. Am J Orthod Dentofacial Orthop, 2007. 132(3): p. 279
e7-14.

108

72. Richardson, E.R. and S.K. Malhotra, Mesiodistal crown dimension of the
permanent dentition of American Negroes. Am J Orthod, 1975. 68(2): p. 157-
64.

4. Roberts, W.E., et al., Rigid endosseous implants for orthodontic and
orthopedic anchorage. Angle Orthod, 1989. 59(4): p. 247-56.

74. Santoro, M., et al., Mesiodistal crown dimensions and tooth size discrepancy
of the permanent dentition of Dominican Americans. Angle Orthod, 2000.
70(4): p. 303-7.

1. Schnelle, M.A., et al., A radiographic evaluation of the availability of bone
for placement of miniscrews. Angle Orthod, 2004. 74(6): p. 832-7.

13. Shapiro, P.A. and V.G. Kokich, Uses of implants in orthodontics. Dent Clin
North Am, 1988. 32(3): p. 539-50.

68. Smith, S.S., P.H. Buschang, and E. Watanabe, Interarch tooth size
relationships of 3 populations: "does Bolton's analysis apply?". Am J Orthod
Dentofacial Orthop, 2000. 117(2): p. 169-74.

87. Stratemann, S., et al., Comparison of cone beam computed tomography
imaging with physical measures. Dentomaxillofac Radiol, 2008. 37(2): p. 80-
93.

93. Swennen, G.R., et al., A new method of 3-D cephalometry Part I: the
anatomic Cartesian 3-D reference system. J Craniofac Surg, 2006. 17(2): p.
314-25.

84. Togashi, K., et al., Three-dimensional cephalometry using helical computer
tomography: measurement error caused by head inclination. Angle Orthod,
2002. 72(6): p. 513-20.

31. Tseng, Y.C., et al., The application of mini-implants for orthodontic
anchorage. Int J Oral Maxillofac Surg, 2006. 35(8): p. 704-7.

67. Upatham, E.S. and V. Viyanant, Opisthorchis viverrini and opisthorchiasis:
a historical review and future perspective. Acta Trop, 2003. 88(3): p. 171-6.

38. Vande Vannet, B., et al., Osseointegration of miniscrews: a
histomorphometric evaluation. Eur J Orthod, 2007. 29(5): p. 437-42.

85. Walker, L., R. Enciso, and J. Mah, Three-dimensional localization of
maxillary canines with cone-beam computed tomography. Am J Orthod
Dentofacial Orthop, 2005. 128(4): p. 418-23.
109

25. Wang, Y.C. and E.J. Liou, Comparison of the loading behavior of self-
drilling and predrilled miniscrews throughout orthodontic loading. Am J
Orthod Dentofacial Orthop, 2008. 133(1): p. 38-43.

33. Wehrbein, H. and P. Gollner, Skeletal Anchorage in Orthodontics - Basics
and Clinical Application. J Orofac Orthop, 2007. 68(6): p. 443-461.

10. Weinberger, B.W., Orthodontics; an historical review of its origin and
evolution, including an extensive bibliography of orthodontic literature up to
the time of specialization. 1926, St. Louis,: The C. V. Mosby company. 2 v.

26. Wilmes, B., et al., Impact of Implant Design on Primary Stability of
Orthodontic Mini-implants. J Orofac Orthop, 2008. 69(1): p. 42-50.

56. Wood, B.A., Tooth size and shape and their relevance to studies of hominid
evolution. Philos Trans R Soc Lond B Biol Sci, 1981. 292(1057): p. 65-76.

28. Yano, S., et al., Tapered orthodontic miniscrews induce bone-screw cohesion
following immediate loading. Eur J Orthod, 2006. 28(6): p. 541-6.

18. Young, K.A., C.A. Melrose, and J.E. Harrison, Skeletal anchorage systems in
orthodontics: absolute anchorage. A dream or reality? J Orthod, 2007. 34(2):
p. 101-10.

90. Xie, Q., et al., Effect of head positioning in panoramic radiography on
vertical measurements: an in vitro study. Dentomaxillofac Radiol, 1996.
25(2): p. 61-6.

110

Abstract (if available)

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

A cone beam-CT evaluation of the proximity of the maxillary sinus to commonly used TAD sites

PDF

Detrimental effects of dental encroachment on secondary alveolar bone graft outcomes in the treatment of patients with cleft lip and palate: a cone-beam computed tomography study

PDF

A cone beam-CT evaluation of the availability of space for complete arch retraction in the mandible with TADs

PDF

Rate of bone loss in furcation-involved molars: a retrospective analysis

PDF

Mandibular plane angle changes with or without premolar extraction treatment in adult orthodontics measured using 3-D cone beam technology

PDF

Cone beam computed tomographic measurements of buccal alveolar bone widths overlying the maxillary premolars

PDF

A cone beam CT evaluation of the maxillary dento skeletal complex after rapid palatal expansion

PDF

Cone-beam computed tomography images: applications in endodontics

PDF

The effect of vertical level discrepancy of adjacent dental implants on crestal bone resorption: a retrospective radiographic analysis

PDF

Comparison of cortical bone thickness between second premolars and first molars in the maxilla and mandible in four ethnic groups

PDF

The effect of cone beam computed tomography (CBCT) imaging on orthodontic diagnosis and treatment planning

PDF

Mental foramina variations: a retrospective analysis using cone-beam computed tomography

PDF

A randomized controlled clinical trial evaluating the efficacy of grafting the facial gap at immediately placed implants in the anterior maxilla: 3D analysis of bone and soft tissue changes

PDF

Prevalence and distribution of facial alveolar bone fenestrations in the anterior dentition: a cone beam computed tomography analysis

PDF

Proper mesio-distal angulation and bucco-lingual inclination of the whole tooth in three-dimensional space -- a standard for orthodontic patients

PDF

Operator-determined and reoriented natural head position in three-dimensional imaging

PDF

Healing of extraction sockets treated with anorganic bovine bone minerals: a micro-CT analysis

PDF

Dimensional changes in alveolar bone following extraction of maxillary molars in humans: a retrospective CBCT analysis

PDF

3D volumetric changes of tissue contour after immediate implant placement with and without xenograft in the horizontal gap: a randomized controlled clinical trial

PDF

Reprogramming the NiTi expander: an alternative to conventional rapid and slow maxillary expansion modalities for the treatment of patients with cleft lip and palate

Asset Metadata

Creator Kim, Sharon Mia (author)

Core Title A cone beam-ct evaluation of the availability of bone for the placement of miniscrews

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 04/15/2008

Defense Date 03/10/2008

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

Tag bone availability,bone stock,cone-beam CT,interradicular space,miniscrew,mucogingival junction,NewTom,OAI-PMH Harvest,tad insertion sites,tads

Language English

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

Creator Email sharonki@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1128

Unique identifier UC1420757

Identifier etd-KimS-20080415 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-57564 (legacy record id),usctheses-m1128 (legacy record id)

Legacy Identifier etd-KimS-20080415.pdf

Dmrecord 57564

Document Type Thesis

Rights Kim, Sharon Mia

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