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Comparison of premolar extraction rates between one-phase and two-phase class II malocclusion
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Comparison of premolar extraction rates between one-phase and two-phase class II malocclusion
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COMPARISON OF PREMOLAR EXTRACTION RATES BETWEEN ONE-PHASE AND Copyright 2012 TWO-PHASE CLASS II MALOCCLUSION by Laura Harshbarger A Thesis Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (CRANIO-FACIAL BIOLOGY) May 2012 Laura Harshbarger DEDICATION To my family for all of their love and support: jason Deyo, ND Gregory Harshbarger, MD Ellen Harshbarger Mark Harshbarger ii ACKNOWLEDGMENTS A special thank you to: Dr. Glenn Sameshima Dr. Harry Dougherty Jr. iii TABLE OF CONTENTS Dedication Acknowledgments List of tables List of figures Abstract Chapter 1: Introduction Chapter 2: Literature Review Class II Malocclusion Studies University of Florida University of North Carolina University of Michigan University of Pennsylvania The Cochrane Review O'Brien, United Kingdom Breman, Germany Baccetti, Italy University of Southern California Chapter 3: Hypothesis Secondary Hypothesis Chapter 4: Materials and Methods Subject Screening and Inclusion Criteria Two-phase treatment group - Case Selection Single-phase treatment group - Case Selection Patient Sample, Distribution, and Premolar Extraction Rate Cephalometric Tracings and Measurements Statistical Methods Institutional Review Board Approval Chapter 5: Results Premolar Extraction Rate Cephalometric Measurements Molar Severity ii iii vi viii ix 1 5 8 10 12 14 15 17 18 19 20 20 24 25 26 26 28 28 29 30 31 32 33 33 34 41 iv Headgear 42 Treatment Time 43 Age and Gender 47 Chapter 6: Discussion 49 Overall 49 Premolar Extraction so Cephalometric Measurements 52 Molar Severity 54 Headgear 54 Treatment Time 55 Age and Gender 56 Chapter 7: Conclusions 58 Primary Conclusions 58 Secondary Conclusions 60 Chapter 8: Limitations 61 References 62 v LIST OF TABLES TABLE 1: Inclusion Criteria for Previous Early vs. Late Class II Studies 10 TABLE 2: Extraction rates in single- and two-phase treatment groups 29 TABLE 3: Frequency of males vs. females in single- or two-phase treatment 29 TABLE 4: Frequency of headgear use in treatment 30 TABLE 5: Cephalometric measurements 31 TABLE 6: Extraction rates in single- vs. two-phase treatment groups 33 TABLE 7: Comparison of cephalometric measurements at initial and final time points for two-phase treatment group 35 TABLE 8: Comparison of cephalometric measurements at initial and final time points for single-phase treatment group 36 TABLE 9: Comparison of change in cephalometric measurements between single- and two-phase treatment groups 37 TABLE 10: Comparison on cephalometric measures at initial and final time points in extraction cases 38 TABLE 11: Comparison on cephalometric measures at initial and final time points in non-extraction cases 39 TABLE 12: Comparison of cephalometric measurements at initial and final time points between single-and two-phase treatment groups 40 TABLE 13: Definition of molar severity score 42 TABLE 14: Molar severity 42 TABLE 15: Change in ANB with and without headgear 43 TABLE 16: Total treatment time in single- vs. two-phase treatment groups 44 TABLE 17: Total treatment time in extraction vs. non-extraction cases 46 vi TABLE 18: Total treatment time in male vs. female subjects 47 TABLE 19: Gender specific mean age in single- vs. two-phase treatment Groups 48 vii LIST OF FIGURES FIGURE 1: Design of University of Florida clinical trial 12 FIGURE 2: Design of UNC clinical trial 14 FIGURE 3: Patient selection criteria 27 FIGURE 4: Bar graph of patients with premolar extractions 34 FIGURE 5: Initial ANB angles for single- and two-phase groups 40 FIGURE 6: Final ANB angles for single- and two-phase groups 41 FIGURE 7: Bar graph depicting extractions with headgear or no headgear 43 FIGURE 8: Total treatment time in single- vs. two-phase treatment groups 45 FIGURE 9: Single phase/ second phase of two-phase treatment time 46 viii ABSTRACT INTRODUCTION: The timing of treatment for Class II malocclusion has been heavily studied yet still remains to be a controversial clinical issue. This study specifically evaluates the ability of Class II growth modification to prevent the need for premolar extraction and the effect it has on cephalometric measurements. MATERIALS AND METHODS: Patient records from the private practice office of an American Board of Orthodontics diplomate in Southern California were evaluated for this study. A total of 106 patient records were examined, 36 were treated in two phases and 70 were treated in a single-phase. The complete records of each patient were analyzed to compare premolar extraction rates between the two treatment groups and their resulting cephalometric measurements. RESULTS: There was no significant difference in extraction rate between two-phase and single-phase treatment. The single-phase treatment group had an extraction rate of 18.6% (13 out of 70 patients) while the extraction rate for the two-phase group was 13.9% (5 of the 36 patients)(p-value 0.543). The change in ANB was the only significant cephalometric difference between two-phase and single-phase treatment with more change occurring in two-phase treatment. CONCLUSION: The results of this study conclude that two-phase Class II treatment does not reduce the rate of premolar extraction by a significant amount. In addition, early orthodontic treatment does not affect cephalometric outcomes, with the exception of ANB. ix CHAPTER 1: INTRODUCTION The timing of treatment for Class II malocclusion has been heavily studied yet still remains to be a controversial clinical issue. The difficulty in deciding when to begin treatment lies in the unknown. The variability between patients and the uncertainty about each individual patient's growth, response to treatment, and cooperation, have prevented a consensus from being established. In order to determine the ideal timing for Class II treatment two important points must be considered: effectiveness and efficiency. It is known that a Class II malocclusion can be corrected at various times for a developing child, so the debate is really whether early treatment provides a superior enough result to justify the likely burden of increased treatment time and financial expense.1.2.3.4.S.6 The three collective approaches to treating Class II malocclusions are: 1. TWO-PHASE: Treatment completed in two phases begins with the first phase during the preadolescent years with limited goals including correction to Class I molar, growth modification with an orthopedic appliance, reduction in overbite and overjet, and incisor alignment. The second phase consists of detailing and finishing of the permanent dentition. 2. SINGLE-PHASE: Treatment completed in one phase comprehensively addresses the patient's problem list during their adolescent years. Skeletal disharmonies 1 are often camouflaged through dental compensation due to diminished growth potential that decreases the ability to manipulate growth. 3. ORTHOGNATHIC SURGERY: This treatment approach has the ability to achieve ideal skeletal positions of the maxilla and mandible once growth of the craniofacial complex is complete. Early treatment advocates believe that the first phase of a two-phase treatment provides a more efficient and simpler second phase thereby decreasing the need for premolar extraction andjor orthognathic surgery.7·8 Better cooperation with extra oral appliances, decreased risk of injury to protrusive upper incisors9.1 ° .11, and improved psychosocial effects are some additional benefits of early treatment.12,13,14JS.16.17.18 However, orthodontists who prefer to treat Class II malocclusions in a single-phase believe that the first-phase does not deliver an improved final outcome nor does it have any more efficient skeletal or dental outcomes.1.19,20 ,21,22,23,24 Single-phase treatment provides a more effective monetary option in many orthodontists' opinions. Since a consensus on the optimal treatment time for Class II correction has not been reached, most orthodontists rely on their own clinical judgment when decided when to begin treatment. Several major studies have been conducted to analyze the 2 difference in treatment outcomes between single- and two-phase treatment, in effort to determine the more effective and efficient pathway to Class II correction.13,15,16,2S These studies collectively indicated that early treatment should not be considered an efficient method to treat most Class II children. Early treatment as a standard of care can be justified only if it will provide additional benefits to the patients. Various special circumstances include psychosocial distress, accident potential, or general convenience to the family.1.2.3.4.12,13,16,17 Significant findings of two-phase treatment included increased treatment time, increased monetary expense, and similar ABO and PAR score in final cast evaluation to single phase treatment.13.15·16·17 Although it has been established that early treatment for most Class II children is no more effective, and considerably less efficient than a later single-phase,1.2.3.4. 12,13,16,17 several of these studies found a correlation bordering on significance between two phase treatment and fewer premolar extractions when compared to single-phase treatment.26 If a causal relationship can be drawn between early treatment and a reduction of premolar extractions as well as improved or similar skeletal and dental outcomes, the decision to begin Class II correction early may be advantageous for many patients. This study researches questions about whether two-phase treatment of Class II malocclusions through growth modification reduces the need for premolar 3 extraction while providing more ideal final cephalometric outcomes such as a decrease in ANB, than single-phase treatment. Cephalometric analysis provides an accurate measure of skeletal-dental relations and is commonly used in diagnosis and treatment planning as well as to evaluate treatment outcomes for orthodontic patients. In order to investigate these predictions, 600 consecutively treated cases provided by a private practice in Southern California were screened resulting in 106 cases that met all inclusion criteria. PURPOSE OF STUDY The purposes of this study are to: 1. Compare premolar extraction rates between single- and two-phase treatment of Class II malocclusions. 2. Compare final cephalometric outcomes between single- and two-phase treatments of Class II malocclusions. 4 CHAPTER 2: LITERATURE REVIEW Determining the best timing for treatment of Class II malocclusion has been a controversial topic for decades. The decision to forgo the early treatment phase is complex because the clinician must consider numerous issues such as psychosocial, behavioral, financial, risks of tissue damage, treatment complexity, duration, stability, and final outcome27·28. In effort to decide the best treatment protocol for Class II correction, various studies have analyzed the differences between single and two-phase treatments; 1.2.3.4.12,13,16,17,29 however, a consensus still has not been decided. Class II malocclusions present with multiple combinations of dental, skeletal, and esthetic problems, each with its own set of solutions. To address each and often several of these important issues, orthodontists have implemented a wide variety of mechanical approaches such as headgear, functional appliances, tissue-and implant-supported intra-arch molar distalization, and intermaxillary traction. Evidence of extra-oral forces, such as headgear, has been applied to the maxilla as early as the late 1800s. The headgear has been extensively studied and has gained widespread acceptance as an effective mean for correcting anteroposterior discrepancies by applying posteriorly directed extaoral forces to the maxilla during a time of facial growth. 30,31.32.33,34,35,36 5 Stahl conducted a longitudinal study to compare the craniofacial growth changes in untreated subjects with Class II Division 1 malocclusion with those in subjects with normal (Class I) occlusion from the pre-pubertal through the post-pubertal stages of development. Both groups, the Class II Division 1 and the Class I, consisted of 17 subjects. The lateral cephalograms were analyzed at 6 consecutive stages of development. The results of the study showed craniofacial growth in subjects with untreated Class II malocclusion is essentially similar to that in untreated subjects with normal occlusion at all developmental intervals, with the exception of significantly smaller increases in mandibular length at the growth spurt as well as during the overall observation period. It was concluded that the Class II dentoskeletal disharmony does not tend to self-correct with growth but rather is associated with worsening of the deficiency in total mandibular length and mandibular ramus height.37 In attempt to solve the issue of insufficient mandibular growth in Class II patients, functional appliances such as Frankel, Activator, Bionator, and Twin Blocks have become increasingly popular in the modern orthodontic office. Functional appliances were designed to reposition the mandible forward and to restrict maxillary growth in effort to develop a more balanced skeletal growth pattern.38·39 A significant amount of mandibular growth in response to Frankel and activator therapy has been demonstrated in many human trial studies.40.41.42.43.44.4S.46 Some argue that it is difficult to determine whether the amount of "additional" growth was 6 in fact stimulated by these appliances or simply the expression of the individual's own natural growth potentiaJ .47.4 B Although many studies have shown that much of the change encouraged by functional appliance therapy is largely dentoalveolar and only mildly skeletal, there is a good consensus on the ability of functional appliances to restrict forward growth of the maxilla.36.49.so.S1.52 A study by O'Brien aimed to assess whether early Twin-block appliance treatment improves the attractiveness of Class II profiles and to determine the orofacial features of a profile that most influence the perception of attractiveness. He found that early orthodontic treatment resulted in improved perceptions of facial profile attractiveness. It was concluded that profile silhouettes of children who had received early orthodontic treatment for Class II malocclusion were perceived to be more attractive by peers than those of children who did not receive treatment. 53 There is good agreement that headgear and functional appliances do produce favorable anteroposterior apical base, molar relation, and overjet changes. However, disagreement exists over the mechanism of AP changes with these appliances. The clearest consensus concerns the inhibitory effect of the headgear on maxillary anterior displacement. Most studies have concluded that activator therapy also inhibits maxillary anteroposterior displacement but that the headgear is more effective. The effect of these appliances on mandibular anteroposterior displacement is less clear, with most authors suggesting no effect.S4,SS,S6,SS 7 Tizziano Baccetti compared the effects of two protocols (bonded Herbst followed by fixed appliances BH +FA, and headgear followed by fixed appliances, HG +FA) for single-phase comprehensive treatment of Class II Division 1 malocclusion at the pubertal growth spurt. The study concluded that Class II treatment with either protocol during the pubertal growth spurt induces significant favorable dentoskeletal and occlusal changes, however the Herbst appliance had a greater favorable impact on the advancement of the chin while retrusion of maxillary incisors and mesial movement of mandibular molars was more significant in the headgear group. 57 Headgear and functional appliances both have many studies confirming their effectives in treating Class II malocclusions and clinicians have had great success with both methods.ss.s9,6o The major question therefore is not which type of appliance to use, but whether the changes achieved by growth modification in the first phase of treatment can be maintained to facilitate a more ideal final outcome. CLASS II MALOCCLUSION STUDIES In 1987 the National Institute of Dental and Craniofacial Research (NIDCR) funded a prospective randomized clinical trial to investigate the timing of treatment of Class II malocclusions, conducted by the University of Florida, the University of North Carolina, the University of Pennsylvania, and the University of Michigan. Each study sought to more clearly define the potential benefits of early treatment when 8 compared to later single-phase treatment of Class II malocclusions. All studies were completed independently of one another with no collaboration among the principle investigators. Each of the studies was designed to determine whether early treatment in mixed dentition followed by a second phase of treatment in the permanent dentition provided superior results to a single phase of treatment. Subsequently, efforts were made by each investigator to analyze the perceived benefits of early treatment, and also to analyze possible risks or burdens. All studies included an experimental group that included patients treated with a two-phase approach as well as a control group who were observed initially and later treated in a single phase during adolescence. The particulars of the inclusion criteria were varied slightly between each of these studies, and will be discussed in detail separately below. The schools' objective was to determine whether growth modification would affect treatment outcomes enough to warrant the additional stage of treatment. These studies provided interesting and valuable information but had the limitations of a university setting, which may not accurately represent the clinical conditions of a private practice. 3.4.5 ,6,18,212 3,26,27 9 TABLE 1: INCLUSION CRITERIA FOR PREVIOUS EARL Y VS LATE CLASS II STUDIES USC. Fagin and USC. Le e . North Carolina Florida Pe nn s y J\r an i a Michigan Fi e. l d s. Yang f\ • l a cf a rl a n e Overjet 2:7mm >Omm >3mm ... 2:4mm Pos it i ve . ov e. rje t Overbite -· > 0 nun ·- ... ... Positive. B il atera l� Va Cia..;$ ll molar cusp Class II Bilateral Class relationship of Bilateral V: step II Bilateral Class Molars I r one side < 'h II, Division I � any degree Class II or - (excluding unilateral% cusp, the. other No unilateral �cusp side> Y.: ClL�P Class I bilateral Class step Class II C la ss II I) All pe rmane nt incisors and Fully erupted first molars Nl) ankylosed erupt e.<! permanem first Ph 1: � 5 teeth molars primary teeth or Teeth ·- ... All permanent 5 3 pem1anen1 520 pennanent No missing teeth (excluding teeth teeth (except third molars, cuspi d..; / 1hird molars) dtweloping as bicuspids set' . n on pa n ore . x Cephalomerric I ye a r pr e - PH Y judge.d by h a n d/ ... ANB 2: 4 . 5• ANB�5o Crileri:l w r i sl film Boys < 14.5 at 7-12.511 3 stan of phase II Age - ... years Girls< 13.5 m stan of phase II h oflrealing I for pha.� e I 4 f or p ha se I 3 t O r ph a se I Ollhl)dOnti.SIS ·- and phase II 4 for phase II I for phase II No surgic al treatment pl an s. no overtmlked Othe r ·- restorations. no previous space m ai nte n ance 1herapy UNIVERSITY OF FLORIDA The Department of Orthodontics at the University of Florida conducted a prospective, randomized clinical trial between 1990 and 2000. The goal of their study was to report on the skeletal changes from phases 1 and 2 to determine 10 whether 2-phase treatment provides a more ideal cephalometric result than single phase treatment. The results from this study for the end of phase 1 treatment were: SNA angle increased in the bionator and observation groups and decreased in the headgear group, whereas SNB angle increased in all 3 groups. ANB angle remained unchanged in the observation group until the start of phase 2 treatment and then decreased in all treatment groups. Although these important cephalometric variables were significantly improved, the differences compared to the control group were nonexistent by the end of phase 2 treatment. 5 ,6,5o 11 FIGURE 1: DESIGN OF UNIVERSITY OF FLORIDA CLINICAL TRIAL ' I � Obsecvanon '- '- .... UNIVERSITY OF NORTH CAROLINA '· BIOf'latOI' I ,-- ______)__ Phase 1 (24 mooths) I Dr."A" Or."&" Or. "C" Dr. "Oy Phase II 1'reatmen.t (Pa tief'lt Treated Sy Ali nnni'\K) � � lieadgear/ Btteplane '-' The objectives of the 2-phased, parallel, randomized trial of early versus later treatment for children with Class II malocclusions at the Department of Orthodontics, School of Dentistry, University of North Carolina, were to assess whether growth modification inf luenced the end of phase 2 skeletal and dental positions and relationships, and the time in comprehensive treatment or the proportion of children receiving or recommended for more complex treatment. 12 Favorable growth changes were observed in about 75% of those receiving early treatment with either a headgear or a functional appliance. However, after a second phase of fixed appliances for both the previously treated children and the untreated controls, early treatment had little effect on the subsequent treatment outcomes measured as skeletal change, alignment, and occlusion of the teeth, or length and complexity of treatment such as need for extractions or surgery. The authors concluded that early treatment should not be thought of as an efficient way to treat most Class II children, but may be indicated in special circumstances such as psychosocial distress, accident potential, or general convenience to the family. 3,4,21,23 13 FIGURE 2: DESIGN OF UNC CLINICAL TRIAL O!l\tH"<•:Il10n UNIVERSITY OF MICHIGAN O<W!tl � 71ntll I hlldoml::mOI'I (Gender) funulonlll App$.1ru::o I IIC!'f&mf(lr!'lilltl!on (Ci!!lllk'r ltm:l Tr�&�l'f!E'n(l I or. '"A� or . . . s-. Dt. "C. Ot; "0" f'tl;.w!.aJtc.:�tmerc IS� Treo1tlftlSOOCIOt) J.Wll�ur This retrospective study examined the benefits of a 2-stage bionator /edgewise treatment plan in comparison to the more conventional single-phase edgewise alternative in non-extraction patients. Discriminate analysis identified two sub- samples of patients who were relatively similar before treatment and thus equally appropriate for the two treatments. Based on each patient's discriminate score, the extreme 25% were subsequently discarded, leaving a central 75% that were similar 14 at the outset and thus relatively free of susceptibility bias. The Michigan study did not have any cephalometric criteria relating the maxillary-mandibular position or angle of the mandibular plane as part of their selection criteria. Also with the extremes of the sample population discarded, some of the most severe Class II malocclusions were not treated in this study. The conclusions of this study showed that despite a slight post-treatment difference in age, the patients in each of the two groups experienced skeletal changes that were essentially indistinguishable by the end of treatment. In both groups, skeletal changes were largely responsible for molar and overjet corrections that were found to be nearly identical in the two groups. Thus, early functional appliance treatment conferred no obvious, measurable benefits on the central 75% over single-phase treatment. 61.62 UNIVERSITY OF PENNSYLVANIA The University of Pennsylvania conducted a prospective randomized clinical trial evaluating early treatment of Class II division I malocclusions in pre-pubertal children with support by the National Institute of Dental Research. The principle goals of this study were to compare extra oral traction and functional appliance therapy in the early correction of Class II molars, and to establish whether treatment in early to mid-childhood is necessary or whether intervention in late childhood is timely enough to correct the malocclusion. 15 Inclusion criteria included: Class II division I malocclusion of any severity, a minimum ANB angle of 4.5, between 7 and 12.5-13 years of age, no prior orthodontic treatment, and expected residential stability of 3 years. Early treatment protocols were undertaken either with a headgear or a Frankel functional regulator. Dental casts were taken every two months and evaluated for occlusal changes, and cephalometric radiographs were taken annually. Results from phase I indicated that both headgear and Frankel's function regulator were effective in correcting the malocclusion. However, while both appliances seem to have a similar effect on mandibular length, the appliances tended to affect the position of the jaws in a differential manner. Headgear had a distal effect on the maxilla and the first molars, but not the maxillary incisors. The Frankel regulator restrained the growth of the maxilla resulting in a retroclination of the maxillary incisors, and encouraged a more forward position of the mandible with proclination of the mandibular incisors. Conclusions from this study indicate that while appliances appeared to generate differential growth of the jaws in the early phase of two phase treatment, single phase treatment in late childhood was shown to be just as effective on treatment outcomes as those treated in mid-childhood.2o.21.22 16 THE COCHRANE REVIEW 2007 The Cochrane review titled, "Orthodontic treatment for prominent upper front teeth in children" examined the efficiency of 2-phase treatment when initiated in patients between the ages of seven and nine years to correct Class II malocclusions. The studies included in the review had to be randomized or controlled clinical trials, the subjects were children or adolescents (16 years or younger) who received treatment to correct prominent maxillary front teeth. Eight trials fit the criteria with a total of 592 patients who had received Class II treatment. The treatments used included various fixed or removable appliances or headgear and, for comparison, an untreated control group. The expected outcomes were 1) The prominence of the maxillary front teeth and the relationship of the two jaws; and 2) self-esteem, any injury to these teeth, jaw joint problems, patient satisfaction, and the overall number of appointments required to complete treatment. The headgear treatment group compared to the control showed a small but significant effect on overjet and a significant reduction in final ANB angle. Differences in overjet, final ANB angle, or peer assessment rating (PAR) scores between the early treatment group and children who had not received early treatment were not significant at the end of phase II. Additionally, with regard to final ANB, PAR score, and final overjet, the headgear group and functional appliance group had similar results. 17 This Cochrane review concluded that early orthodontic treatment for children with prominent maxillary incisors is no more effective than one course of treatment when the child is in early adolescence.63 O'BRIEN, United Kingdom The study conducted by O'Brien aimed to evaluate the effectiveness of early orthodontic treatment with the Twin-block appliance for the treatment of Class II Division 1 malocclusion. !t was a multi-center, randomized, controlled trial with 174 subjects aged 8 to 10 years with Class II Division 1 malocclusions from 14 orthodontic clinics in the United Kingdom. The study consisted of two groups: early treatment with a Twin-block appliance and initially untreated control. All subjects were then followed until all orthodontic treatment was completed. Final skeletal pattern, number of appointments, duration of treatment, extraction rate, cost of treatment, and the child's self-concept were considered. The results of their study revealed no difference between those who received early Twin-block treatment and those who had a single-phase of treatment in adolescence with respect to skeletal pattern, extraction rate, and self-esteem. The early treatment group had more appointments, longer treatment time, and incurred more financial costs than the adolescent group. They concluded that Twin-block treatment at the ages of 8 to 9 years of age has no advantages over treatment started at an average age of 12.4 years, and also has the disadvantages of increased 18 burden for the patient in terms of attendance, costs, length of treatment, and an inferior final occlusal result. Their study reinforced similar conclusions of other randomized controlled trials previously mentioned.64 BREMAN, Germany Breman of Giessen, Germany conducted a study to assess the efficiency of early and late Class II Division 1 treatment in the mixed and permanent dentition. For the study efficiency was defined as a better result in a shorter treatment time. 2 04 patients were divided into early mixed, late mixed, and permanent dentition. The orthodontic appliances used during active treatment were of 4 types: functional, combination (functional and fixed appliances in combination), Herbst (in combination with multi-bracket appliance), and multi-bracket appliances alone. The pretreatment and post treatment dental casts were evaluated using the PAR index. The results of the study were as follows: duration of treatment decreased with progressing dental development, patients treated exclusively with fixed appliances had a shorter treatment duration than did patients treated with functional appliances or a combination of appliances, the PAR score reduction increased with progressing dental development, patients treated exclusively with fixed appliances had a greater PAR score reduction than did patients treated with functional appliances or a combination. Bremen concluded that treatment of Class II Division 1 malocclusions is more efficient in the permanent dentition than it is in the mixed dentition.65 19 BACCE TTI, Italy The aim of this cephalometric study was to evaluate the role of timing in relation to skeletal maturity on the outcomes of nonextraction comprehensive Class II therapy. Three groups of patients with Class II Division 1 malocclusions were divided by skeletal maturity at time of treatment (before pubertal growth spurt, during pubertal growth spurt, and at a post-pubertal stage of development) and were treated with headgear combined with fixed appliances and Class II elastics. The lateral cephalograms were taken on each patient before therapy at time Tl and at an average interval of six months after the completion of treatment, T2. The results of this study showed that Class II treatment before or during the pubertal growth spurt induced significant favorable skeletal changes by restricting maxillary advancement in pre-pubertal patients and enhanced mandibular growth in pubertal patients. Only dentoalveolar changes were found to be significant for patients treated after the pubertal growth spurt. In conclusion, the greatest amount of dentoskeletal correction of Class II malocclusion with single-phase nonextraction treatment occurred in patients treated during the pubertal growth spurt.66 UNIVERSITY OF SOUTHERN CALIFORNIA STUDIES The University of California studies gathered patient records from private practices throughout the United States, with the intention of minimizing the inevitable treatment bias of a teaching institution. Fagin and Yang67 compared outcomes of 20 early two-phase versus single-phase treatment of moderate to high angle Class II patients, and Lee6 B, Fields24, and MacFarlane69 separately compared the premolar extraction rate between single- and two-phase Class II treatment modalities. - Fagin and Yang Fagin and Yang, two former USC residents, collected patient records from three offices of ABO diplomates in Los Angeles, Vancouver, and Seattle, to examine for their retrospective study on early treatment of high-angle Class II malocclusion patients. Patients included in this study were required to have a minimum of 4mm overjet, Class II molar relationship, ANB angle greater than 5 degrees, and either an Sn-G oGn angle greater than 37 degrees or an FMA angle greater than 30 degrees. Patients were randomly grouped into a headgear, functional appliance, or an observation group. Their study concluded that there was no significant difference in vertical and antero-posterior relationship change, initial PAR, final PAR, or PAR change between the early treatment group and the single-phase treatment groups. There was a significant difference in pre-and post-treatment IMPA angle between the two groups, the early treatment group had fewer extraction but not by statistically significant amount, and treatment time for the early treatment group was significantly longer than the later treatment group.67 21 -L ee Lee, another former resident of USC, was interested in determining whether private practice treatment would produce similar results to the findings of the UNC and UF studies. Patient records were collected from a private practice office of an ABO diplomat in Yorba Linda, CA. The purpose of the study was to compare extraction rates between patients with Class II malocclusions treated in two-phases and those treated in a single-phase. Inclusion criteria were: bilateral half-step or unilateral three-quarter step Class II molar, positive overbite and overjet, no ankylosed teeth, and no surgical treatment plan. The study concluded that the use of headgear in either treatment group reduced the number of premolar extractions but not by a statistically significant amount. The two-phase treatment group had fewer premolar extractions than the single-phase treatment group, but the difference was not significant. The skeletal and dental cephalometric analysis was also not significant, confirming the findings of UNC and UF.6 B - Fields Fields from USC investigated the difference in premolar extraction rates in Class II patients between single-phase and two-phase treatment groups. Records were collected from the private practice of an ABO diplomat in Yorba Linda, CA. The inclusion criteria were the same as the previous study conducted by Lee. Fields' study concluded that premolar extraction rates were significantly less in the two phase treatment compared to the single-phase treatment group. This result 22 interestingly was in direct opposition of the University of Florida and the University of North Carolina studies. The cephalometric measurement changes between time points were not significant between the two treatment groups, similar to the UF and UNC studies. Fields analyzed the molar severity after the first phase of treatment but since the treating orthodontist treated phase I patients for 12-13months regardless of molar change, this finding was difficult to assess. This study also concluded that the total treatment time for the two-phase group lasted six months longer than single-phase group, however, the two-phase treatment group spent seven months less in fixed appliances. King et a! also observed this particular finding.26 - MacFarlane The purpose of the retrospective study conducted by MacFarlane at the University of Southern California was the same as the Fields' study with the same inclusion criteria. The records were collected were from the private practice of an ABO diplomat located in Covina, CA. MacFarlane's study concluded there is no statistically significant advantage to either single- or two-phase Class II treatment with regard to cephalometric outcomes. Different from the results of Fields' study, MacFarlane found the premolar extraction rate for the two-phase treatment group was not significant when compared to the single-phase treatment group. The overall treatment time for the two-phase group was significantly longer than the single phase treatment group, confirming the findings of previous studies.69 23 CHAPTER 3: HYPOTHESIS 1. There is a statistically significant difference in premolar extraction rates between single-phase and two-phase treatment 2. There is a statistically significant difference in cephalometric outcomes between single-phase and two-phase treatment groups a. Single-phase i. Compare initial and final cephalometric outcomes b. Two-phase i. Compare initial and end of phase I cephalometric outcomes ii. Compare end of phase I and final cephalometric outcomes iii. Compare initial and final cephalometric outcomes 3. That there are statistically significant differences in cephalometric outcomes to extraction rates a. Compare single-to two-phase extractions patients b. Compare single-to two-phase non-extraction patients 4. There is a statistically significant reduction in molar severity for two-phase treatment when comparing initial molar severity and molar severity at the beginning of phase II. 5. There is a statistically significant difference in total treatment time and time spent wearing fixed appliances between single- and two-phase treatment groups 24 6. There is a statistically significant correlation between patients wearing headgear and a more ideal ANB and fewer extractions, compared to the non-headgear group of patients SECONDARY HYPOTHESES 1. There is a statistically significant difference between length of treatment time and gender, with female patients treating in a shorter period of time than male patients 2. There is a statistically significant difference in age at the start of treatment between male and female patients, with female patients beginning treatment earlier than male 3. There is a statistically significant difference between length of treatment time and treatment plan, with non-extraction cases treating more quickly than cases requiring premolar extractions 25 CHAPTER 4: MATERIALS AND METHODS SUBJECT SCREENING AND INCLUSION CRITERIA The records used for this retrospective study were collected from a private practice of an USC trained American Board of Orthodontics (ABO) Diplomate in Van Nuys, California. This orthodontist has been practicing for over 28 years and is currently teaches courses in surgical orthodontics and biomechanics at UCLA, cephalometries at USC, is on the Board of the Pacific Coast Society of Orthodontics, and he is soon to become the president of the American Association of Orthodontists Foundation (an organization that raises money to fund research in orthodontics and support orthodontic education). 600 consecutively treated cases were screened for Class II malocclusions that were treated immediately following diagnosis regardless of age at presentation. All initial patient models from january 2003 to December 2008 were examined. Screening for qualified cases was conducted in two rounds. The first set of inclusion criteria was as follows: a minimum of a bilateral quarter-step or unilateral half-step Class II molar relation and under the age of 16 years 0 months. Patients with abnormally contoured restorations, ankylosed teeth, andjor surgical treatment plans were excluded from this study. This initial screening resulted in 242 cases that were eligible for the second round of the selection process. 26 The se c ond set of inclusion criteria required patients to have a full pe rman ent denlition with the excepti on of third mo lars, a minim um of bilateral half- step or unilateral thre e- quarter- step Class II mo lar relati on, po sitive o verbite, po sitive overj et, and c omplete ortho donlic re cords including initial and final radi o graphs. pho to graphs, andmo dels . There was no criterio n for mandibular plan angle (MPA ) or numb er of eru pte d pe nnane nt teeth. The c ompletio n of the two rowtd scre ening pro ce ss re sulte d in 106 case s for this study. FIGURE 3: PIITIENTSEI.ECT/ON CRI TERIA ConseCtltively Treated Cases [ 600 Patients I • Clas s II Molar ( min bilat era l X s t ep ) • P os itive Ove t blt e Pos iti ve Ov e rje t • [ Full Records I • No Missing or Ankytosed Teeth • I 106 Patients Non·surgical Treatment Plan 27 TWO-PHASE TREATMENT GROUP- CASE SELECTION Subjects of the two-phase treatment group were required to have a minimum bilateral half-step or unilateral three-quarter-step Class II molar classification, positive overbite, and positive overjet, no missing teeth other than third molars, no ankylosed teeth, and a non-surgical treatment plan. No minimum amount of overjet was established to allow inclusion of Class II Division 2 malocclusions. The first phase of treatment at this particular orthodontic office was determined by age of patient and severity of malocclusion. Treatment consisted of a headgear with a 2x4 appliance. Headgear growth modification was used until a Class I molar relation was achieved. At the discretion of the orthodontist, patients were either given a retainer or no appliance after completion of the first phase of treatment. These patients were placed on recall until the start of the second phase of treatment with fully bonded appliances. SINGLE-PHASE TREATMENT GROUP- CASE SELECTION Selection for the single-phase treatment group was the same as the two-phase treatment group. The single-phase patients either presented for orthodontic evaluation during adolescence or the choice to be treated in a single phase was decided. Treatment began with the exfoliation of all primary teeth with the exception of primary second molars. 28 PATIENT SAMPLE; DISTRIBU TION, AND PREM OLAR EXTRACTION RATE Of the 106 patient cases selected for this study, 70 patients were treated ina single phase and 36 were treated in two. Thirteen patients (18.6%) of the single-phase treatment group and five patients (13.9%) of the two-phase treatment group had premo lar extra cte d. The de cision to e:«:ract was base d on a co mbinati on oflower inci sor po siti on and amo unt of cro wding. TABLE 2: EXTRACTION RATES INSINGLE- AND TWO-PHASE TREATMENT GROUPS EX T RACT ION R AT E TOTAL EXTRACT N ON - E XTR ACT I PHASE 70 1 3 (1 8.6% ) 57 (81.4%) 1 PHASE 36 5 (13.9% ) 31 (8 6. 1 %) TOTAL 106 1 8 88 TABLE 3: FREQIJENCY OF MALES 1/S. FEMALE IN SINGLE· OR TWO·PHASE TREATMENT M AL E S v s . FEM A L E S T OT AL I PH A S E 2 P H ASE MALE S 48 4 0 8 FEM 1\LE S 58 30 28 29 TA BLE <k FREQ UENCY OF HEAD GEAR USE IN TREA TMENT HE ADGE AR v s . NO HE ADGEAR T OTJ \L I PHASE 2 PHASE HEADG E AR 8 7 5 1 30 N O 19 13 6 HEADG E A R CEPH ALOMEI'RICTRACNGS AND MEAS UREM ENTS Lateral cephalomemc radiographs of each patient were importedinto Dolphin Imaging 10.5 Premiwn software and eleven measurements were trace d to evaluate an�, linear, and prop orti onal change s (TABL E S).Jnitial and final tracings were re corde dfor the both groups while an additi onal tracing, initial of phase II, was includedfor the two-phase group. 30 TABLE 5: IEPHALOMETRIC MEASUREMENTS A- P Maxilla SNA angle. A- P Man d ible SNB angle. Maxilla to Ma n d ible ANB angle Lower In cisor LI -NB de gree, LI-NB mm Vertical (Skeletal) FMA angle (MP-FH ) Dental Relationship lnterincisal angle (U I-Ll) Upper Incisor UI-NA degree, UI-NAmm Chin Projection Pog-NB nu n Sf ATISTICAL METHODS In order to evaluate the differences in extraction rate between single-and two phase patient treatments, the Pe arson chi squared test was use d. Due to the small sample si;zoe of tw.rphase extraction patients.. the Wilooxon rank test was used to compare the change in a continuous variable for a given group of patients (e.g. change inANB for a single-phase treatment). The Mann-Whitney- Wilcoxon U-test was used to compare differences cl a continuous variable between different groups (e.g. difference in ANB betwe en single- and two-phase patients). This allowed meaningful oomparisons of the means to be made without needing to asswne a normal distribution. Means, standard deviations, and p-values were all reported. The investigators conducted all statistical analyses. Significance was set at p s. 0.05 for the Pearson chi square d test and p s. 0.01 for all other statistical tests. 31 INSTITUTIONAL REVIEW BOARD APPROVAL The proposal to conduct this investigation was approved by the Institutional Review Board (IRB) on january 3, 2011. USC UPIRB # UP-10-00453 32 Cl!AP TER 5: RE SULTS PREM OLAR EXTRACTI O N RATE The singl e-phase treatment group had an extracti on rate of 18.6% (13 out of 70 patients had premolars eJ<tracted) while the extra ction rate for the two-phase group was 13.9% (5 of the 36 patients had premolars extracted). The difference in extractio n rate b etwe en the two groups, calculate d using the Pearso n Chi S quare d test, was not significant (p-value 0.543) as shown in TABLE 6. TABLE 6: EXTRACTION RATES IN SINGLE· TIS TWO·PHASE TREA TMENT GROUPS EX TRACT I ON R A T E TOT1\L EXTRACT N O N- EXTRA CT I PHAS E 70 13 (1 8.6%) 57 (81. 4% ) 2 PHAS E 36 5 (13.9% ) 3 1 (8 6. 1 %) TOTA L 106 1 8 88 33 FJGURE 4: BAR GRAPH OF PATJENTS WJTH PREMOLAR EXTRACTJONS CEPHALOMETRIC MEASUREMENTS Six of the two-phase treatment cephalometric measurements from initial to final time points were significant (p s 0.01) including: SNA, ANB, UlNAdeg, PogNBmm, IntAng, and FMA (TABLE 7). Wilcoxon Signed t-test was used. 34 TABLE 7: COMPARJS!ON OF CEPHALOMETRIC MEASUREMENTS AT INITIAL, MIDDLE, AND FINAL TIME POINTS FOR TWO-PHASE TREATMENT GROUP TWO-PHASE TRE1\TMENT GROUP INITAL Mid P(M-1) FINAL P(F-M) I'(F-1) SNA 81.9+/-3.6 81.1+ / -3. 0 0.255 79. 9+ / -3. 3 ..-...O .QI <.0 . 0 1 SNB 7 6. 2+ / -3.0 77. 2+/ -3. 3 0.011 77. 1+/ -3. 6 0.871 0.011 ANB 5. 8+ / ·2. 6 3. 9+/ -1. 4 '-. 0. 01 2. 8+ / ·1. 5 ·-0 . 01 '-.0. 0 1 UINAmm 3. 1+ / -3.8 3. 5+ / - 2 . 0 0.735 4. 3+ / - 2 . 0 0.029 0.047 UlNAdeg 19. 1+ / - 7 .8 22. 9+ / -5. 8 <, 0. 01 26.4 +/ -5. 3 . ... 0. 01 0. 01 LINBmm 5. 1+1·2. 1 6. 7+ / -11. 2 0.517 6. 3+ / -4. 6 <0. 01 0.164 LINBdeg 15. 1+ / - 7.5 14. 9+ / -6. 0 0.777 26. 8+1 -4.4 0.085 0.118 PogNBmm 0. 9+ / -1.2 1.3+/-1.2 0.100 1.9+/-1.4 ..-...O .QI <.0 . 0 1 lntJ\ng 119.9+/-IU 118. 3+ / -9.1 0.330 1 2. 1. 8+/ -6. 7 0.023 '-.0 . 0 I FMA 31.1+/-6.9 19. 5+1 ·5. 5 0.063 27.7 +1 ·5. 5 0.018 '-.0. 0 1 IMP/\ 94 . 1+ / -8. 3 93 . 6+/ - 7 .1 0.820 95. 2+ / ...( t. 2 0.223 0.396 Table 8 shows the changes in cephalometric measurements from initial to final time points for the single-phase treatment group. SNA, ANB, UlNAdeg, PogNBmm, and FMA were significant (p.: 0.01). Wilcoxon Signed t-test was used. 35 TABLE 8' COMPA RISON OF CEPHA L OMETRIC MEASUREMENTS AT INI TIAL AND FINAL TIME POINT S FOR SINGLE· PHASE TREA TMENT GROUP SrNGLE•PHASE TIUiATMENT GROUP INITAL FINAL P(f·l ) SNJ\ 82.h/-4.3 80.7+/-4 .1 "-0.01 SNB 77.7+/-3.6 76. 8+/-9 .1 0.911 A N B 4. 5+/ -2. 4 3.0+/- 2.4 ... 0.()1 UINAmm 3.6+ / -2. 5 3.8+/- 2.4 0.925 UINAdeg 21.5�/-7.6 25 .1+ /- 5.4 '- 0. 01 LI�Bmm 5. 1 T / • 2. 3 5.2+/ - 2.0 0. 535 LINBdeg 26.5 � 1 -6.8 27 .3+ /-4 .9 0.433 PogNBmm 1.7+/-1.6 1. 8 +/- 2.6 .;.. 0.01 lmAng 127.5T/•10.6 1 24.5+/-6 . 6 0.04 2 FMJ\ 28.5+/-5.1 16 .0+ /- 5. 3 ·•0.0 I IMP A 96.0+/-7.1 9 6.6+/-8. 3 0.330 Table 9 shows several significant cephalometric changes between single· and two· phase treatments (either initial to final or middle to final). ANB change, SNB change, UlNA degre e change from initial to final time po ints to a more ideal position was si gnificant (p .: 0.01) betwe en groups with more corre cti on o ccuning in the two· phase treatment. 36 TABLE 9: COMPA RISON OF CHANGE IN CEPHALOME TRIC MEASUREMENTS BETWEEN SINGLE· AND TWO· PHASE TREATMENT GROUP CHANGES BETWEEN SINGlE AND TWO PHASE TREATMENT p ( 1 12 ) P 112 (1"- m ) P 1 12 (m - i) SNA 0.531 0. 7 34 0.1 51 SNB 0.03: 0.767 0.017 ANB '-0.0 I 0.1 76 0.61 9 UINAmm 0.085 0.094 0.791 UINAdeg 0.017 0.883 0.9 92 LINBmm 0.548 0.1 76 0.349 LINBdeg 0 .3 57 0.399 0.655 PogNBmm 0. 21 5 0. 669 0.254 lmAng 0.1 45 0.767 0.488 FMA 0.494 0.4 43 0.3 77 IMP A 0.821 0.61 7 0.449 Change in ANB was signifi cant for b oth extraction and non-extracti on groups betwe en single-phase and two-phase as well as SNB change for the extraction group (TABLE 10 and 11 ). Differenc es between initial and final value s for single· and two· phase treatment groups were calculated using the Mann-Whitney_ Wilcoxon·U·test. 37 TA BLE 10: COMPA R JSON OF CEPHA LOMETR IC MEA SURES AT INI TIA L AND FINA L TIME POINTS IN EXTRA CTION CASES EXTRACrJON I PHASE 2 PHASE INITIAL FINAL rNITl"L FINAL p SNA 82.8+ / -3 .9 81.2+ /-4 . 0 82. 3+ / -3.6 80.6+/-2.9 0.95 1 SNB 78.1+ / -3.6 77. 3+ /- 9. 9 76.6- /-2.9 77.9+/-3.2 0.0 �7 ANB 4. 6 + / -2 .3 2.8 + 1 -2.5 5.7� / -2.7 2 . 7+ / - 1.5 O. Ol6 UINAmm 3. 6+/ -2 .5 4. 0+ 1 -2. 4 3.h/-4.0 4.5+/-2.0 0.296 UINAdeg 21 .4+/-7.7 25. 2 + 1 -5.5 19.5�/ -8.1 26. 7+/-5.5 0.081 llNBmm 5. 2 + 1 -1.4 5.3 + / -2. 2 5.1+/*2.4 6.5+/-4.9 0.352 LINBdeg 21 >. 4 + / -6. 5 27. 6+/-5. 0 2 4 .9 - / - 7.7 2 7.0+ / -4. 3 0.474 PogNBmm I. 7+/- 1.6 1. 7 + / -1 . 9 0.9+/- 1.2 1.7 + / - 1. 4 0.487 lmAng 1 27 . 6+/ - 10 .9 12 4.1+ /-6.7 12 9. 8+ /- 11. 6 123.3+/-6.5 0.295 FM1\ 27.8+/-5.1 25. 2 + / -5. 4 3 1.0+/- 7.0 27.3+/-5.7 0.332 IMP A 9 6. 3+ / -6 .4 97. 3+ /- 8. 6 94.0+/-8.7 9 5.6 + / -6 .2 0.990 3!! TA BLE 11: COMPARISON OF CEPHA LOMETRiC MEASUREMENTS AT INITIA L AND FINAL TIME POINTS IN NON-EXTRA CTION CASES 1\'0:-.1-EXTRi\CTION I Phn< c 2 Ph os e lni1ial fin .a l lnilial fin al p SNA 7 9.h/-5. 0 78 .5+1 ·3.9 79.9., . /-3.4 75.6+1·2. I 0. 0 44 SN IJ 75 . 9 ... /- 3.1 74.8 +1 - 3.6 7 3. 8 +/ - 2 .6 72. 4+ 1· 1.6 0 . 982 i\NB 3.9+ / - 2. 6 3. 7+1- 1.6 6. I ., . /· 2. 3 3.2+/.o. 7 0.014 U I NJ\ mm J .R T/·2. 7 2. 5+/-2.2 1.7 .,. 1·2. 0 2. 7+ /· l. .l 0.0 75 U l i'f Ad eg 22.2•1·1.6 24.6+/-4 .8 I 6 .5•1·5 . I 24.(>+/·3.8 0.208 Ll i'fBmm 4.9+/-2.3 5.2.,./- I. I 5.41'/- 1.6 4.8+/- 1.8 0.455 LIN B<Icg 21 . 0 .,.1 - X. I 25. 6 + / -4. 3 26. 1 +/ . (l, (t 25. 4 +/ -4.8 0. 703 rogNBmm J .7T/• J. 7 2.2+/- 1.3 I. I +/·1 .2 2 .9+/- 1.0 0.124 ln! Ang I 26.9T / ·9. I I 26. I +/-6. I IJ0.9 T/ ·12.8 126.9+/·7.6 0.143 F MA 31. 9 ... /- 3.4 29.5 +/·3. I 3 1 . 5 ... 1- 1.5 J O..l +/·2 . 9 0 .4 8 7 IMP!\ 94 .8+/ -10. 0 93.5 T/-5.9 95.0 � /-5. 6 92.8+1·6. I 0.904 39 TABLE 12: COMPARISON OF CEPHALOMETRIC MEASUREMENTS AT /NI T/AL AND FINAL TIME POINTS BETWEEN SINGLE- AND TWO-PHASE TREA TMENT GROUPS [::'IIITIAL F l }.IA L :'II A 0.096 0.886 SNB 0.681 0.056 ANB 0.605 !I 11 2.• UIN Amm 0.630 0.180 Ul NAdeg 0.649 0.095 Ll NBnm1 0.63H 0.74S LI ::'I!Bdeg 0.756 0.658 Pog::'I!Bmm 0.584 0.092 lntAng 0.989 0.330 FMA 0.327 0.380 IMPA 0.579 0.629 FIGURE 5: INI TIAL ANB ANGLES FOR SINGLE- AND TWO-PHASE 1S T I 10 -, I I 0 I i :l n � . � I I j_ 0 L 40 FIGURE 6: FINAL ANB ANGLES FOR SIN GLE- AND TWO-PHASE IS•r---�------�-------r----------� 10 f -.,- i s n 1 Q I � e � --'- -'- 0 MOLAR SEVERITY Molar severity was determined by quarter cusp increments. A Class I molar was assigned a value of 0, quarter-step Class II molar was assigned 0.25, half-step Class II molar was assigned 0.5, and 1.0 was assigned to a full-step Class II molar relation (TABLE 13). The difference in molar relationship between the initial time point of two-phase treatment and the beginning of the second phase (middle time point) was significant (p s 0.01) (TABLE 13). 41 TABLE 13: DEFINIT ION OF MOLAR SEV ERITY SCORE MOLAR CL.I S S S EJ' E RITY SCO {(£ Cl o ss I 0 .00 Qumer·St<p Class II 0.25 Hal r· St ep C lass II 0 .50 Fu ll - S t ep C l ass II 1.00 TABLE 14: MOLAR SEV ERITY MO L1\R SEV ERI TY S CO RE BASELINE P HASE 2 DIFFERENCE r STJ\ RT SCO RE 0.7 + / . 0 .1 0 . 1 + / . 0. 2 0.5 + I · 0.3 < Q . O I HEADGEAR A s ignifi cant change was found betwee n initial and final ANB for both the headgear a.nd non-hea.dgea.r groups (Wilcoxia.n Signed t-test). There wa.s no significant difference in ANB change between the headgear and non-headgear groups (p = 0.63 9) as shown in TABLE 15 (Mann·Whitney·W ilcoxian·U·test). 42 TABLE 15: CHANGE IN ANB WITH AND WIT HOUT HEADGEAR (Mann-Whitney Wilcoxian-U-test) IIEADGEAR NO liEADGEAR INITLAL FINAL r INITAL FINAL r P (hg, no-hgl 1\NB 5.1 �t. 2.5 3.0 .. ,. 2.5 Ohl 4.3 -t•' .. 2J 2.6 �/- z.z 0 �II 0.639 ·� EXT 11.5 10 of87 42.1 8 of 19 FIGURE 7: BAR GRAPH DEPICTI NG EXTRACTIONS WITH HEADGEAR OR NO HEADGEAR 09 08 07 106 Jos § lo' .. 03 02 01 TREATMENT TIME A significant difference in treatment time was found between single-and two-phase treatment groups (p s 0.01). The total treatment time for single phase was 31.1 months, and 46.3 months for two-phase treatment (TABLE 16). The diff erence in 43 length of time betwe en single-phase and the s ec ond-phase of two -phase treatment was also found to be significant (p.: 0.01). The difference in treatment time betwe en extractio n and non- extra cti on groups was not significant with a p-value of 0. 724 (TABLE17). TABLE 16: TO TAL TREATMENT TIME IN SINGLE· TIS TWO· PHASE TREATMENT GROUPS TREATMENTTIME (Earlyvs. wte.) I PHASE 2 PHASE p PHASE II 31.1 +I- 8.4 24.4 T/• 6.3 " 0.01 T OTAL 3 1. 1 +1- 8.4 46.3 �1- 9.9 <0.01 44 FIGURE 8: TOTAL TREA TMENT TIME IN SINGLE- VS TWO-PHASE TREA TMENT GROUPS j f � f -,- I I I •so � " - � - g«> I ! I ... c f"' 20 I l. 10 0 I $Ingle PhNO TwoPn•M 45 FIGURE 9: SINGLE-PHASE/ 2ND PHASE OF TWO-PHASE TREATMENT TIME j !� f �so E - � - . �� I I N c I *"" I l ,---L I 20 l. 10 0 I $Ingle PhNO TwoPn•M TABLE 17: TOTAL TREA TMENT TIME IN EXTRA CTION VSNON-EXTRACTION CASES TOTAL TREA TMENT TlME EXTRACTION NON- p EXTR.ACTJ0}-1 TOTAL TIME 36.4+1· I 0.1 36.3 +i- 11.8 0.7.:!4 Single-phase female patients were treated longer (33.7 months) than male patients (29.2 months) but not enough to be significant (p = 0.111). In two-phase treatment, male patients treated longer than female patients but also not by a significant amount of time (p = 0.939). TABLE 18. 46 The treatment time for male s and female s treate d ina single phase and tho se treated in two-phases was too similar to be significant. TA BLE 18: TO TAL TREA TMENT TIME IN MALE VS FEMALE SUBJECTS G ENDER S PEC IFI C TOT AL TREA TMENT TI ME I PH A SE 2 P HASE p MALE 29.2 + /- 6 .5 48.3 � t. 1 5.9 .. o .o 1 F EMALE 33.7+/-10.1 4 5.8- 1 - 7.7 - 0.01 r 0.111 0.9 39 AGEAND GENDER The difference in age for male and female patients between single- and two-phase treatment groups, and within the single-phase group, was significant. The mean startin g age for female patients was significan tlyyoungerthanm ale patients. There was no significant differenc e for the total treatment time s b etwe enmale s and females. 47 TABLE 19: GEN DERSPEGFICMEANAGE INSINGL E· VS TWO-PHASE TREATMENT GROUPS (Man n· Whitr.ey· W!lcox ian U· test) G E N D E R SP E C IF I C M EA N A G E FO R TR E A TM E I\ 'T I P H A SE 2 P HAS E p M A L E 12.6 +/- 1.3 9.4 .,.,_ 0.9 '0.01 F EM A L E 11.4 +/- 1.3 9.3 �/- 1.1 '0.01 p 0.0 I 0.74 6 48 CHAPTER 6: DISCUSSION OVERALL This investigation was designed to address some important issues to determine the optimal time for treating patients with Class II malocclusions. The primary hypothesis was two-phase treatment reduced the need for premolar extraction compared to single-phase treatment and that cephalometric outcomes of the two phase group were more ideal than single-phase. A single orthodontist treated all cases in this study to minimize clinical bias. A total of 106 cases were selected through a two round screening process, 70 one-phase and 36 two-phase. Patients of the two-phase group were treated with headgear until a Class I molar was achieved regardless of length of time. Early treatment studies conducted at Universities have the disadvantage of drawing conclusions that are not always relevant to a private practice setting such as: multiple treating orthodontists and residents and school-mandated vacation time. A private practice was the source chosen for this study to produce data that is more pertinent to private practice clinicians to help make evidence-based clinical decisions. 49 PREMOLAR EXTRACTION RATE The results of the University of North Carolina's study did not reveal a significant difference in premolar extraction rate between the single-phase, bionator, and headgear groups. The single-phase control group had an extraction rate of 28%, the bionator group 35%, and only 17% the headgear group had premolar extractions. Although a trend was observed between treatment and extraction rate it was concluded that early treatment did not conclusively reduce the need for premolar extraction. 3.4.21. 23 The University of Florida study also found the difference in premolar extraction rate between single- and two-phase (headgearjbiteplane and bionator) treatments to be not significant. Although their findings were not statistically significant, a correlation was drawn between treatment protocol and extraction rate: observation group 20%, headgearjbiteplane group 12%, and the bionator group had an 8% extraction rate. 5,6,5o Fagin and Yang (USC) results showed a 37.5% extraction rate for two-phase treatment group while the single-phase had premolars extracted 50% of the time. Although very close, the calculate p-value was 0.017 and therefore not considered statistically significant according to their study.67 Lee's (USC) findings were consistent with the previous study's trend with a single-phase extraction rate of 44% and 20% for the two-phase treatment group, not statistically significant.68 so Fields' (USC) study arrived at a different conclusion. She found a significant difference in premolar extractions between two-phase (22.9%) and single-phase ( 49.2%) treatment groups (p ,; 0.01). Two-phase treatment resulted in almost 50% less premolar extraction than the single-phase group.26 The successive study by MacFarlane (USC) did not support the hopeful findings of Fields with a non significant difference found in premolar extractions between the two treatment groups, single-phase 48.1% and 31.6% two-phase extraction rate.69 In this study, the single-phase treatment group had an extraction rate of 18.6% while the extraction rate for the two-phase group was 13.9%. The difference in extraction rate between the two groups was not significant (p-value 0.543) as shown in TABLE 6. The results of this study as well as the previous studies mentioned, indicate that patients treated in two-phases do not require as many extractions as patients treated in a single phase, but not by a statistically significant amount, with the exception of the study conducted by Fields (USC). Although the results of this study are consistent with regard to significance, the p-value is considerably larger indicating there is less of a relationship between extraction rate and treatment group, than previous studies have found. This difference may be attributed to the personal preference of each treating orthodontist to favor extraction or non-extraction treatment or perhaps the patient pools varied enough with regard to other factors such as crowding, incisor position, or facial profile, for example, which were not addressed in the inclusion criteria. This study's finding 51 does not negate the borderline significance shown by previous studies with respect to two-phase treatment and fewer premolar extractions. Perhaps this study reveals the importance of other dental or skeletal factors that may also influence the decision to extract or not extract in combination with or independent of Class II malocclusion. CEPHALOMETRIC MEASUREMENTS There are many ways to determine the quality of treatment. The University of Florida, the University of North Carolina, and Fagin and Yang (USC), used the Peer Assessment Rating (PAR) to assess treatment outcomes. PAR was originally an objective mean to assess the quality of treatment when studying rotations and occlusion. Tulloch found it was possible for two dental outcomes with different tooth to basal bone relationships to have the same PAR score. 56 Because of this potential problem in accurately comparing the outcomes of different treatment groups, cephalometric measurements were the chosen method of examining the quality of single-phase and two-phase treatment groups for this study. The six two-phase treatment cephalometric measurements that showed significant differences (p ,; 0.01) from initial to final time points, were: SNA, ANB, U1NAdeg, PogNBmm, In tAng, and FMA (TABLE 7). Table 8 shows the changes in cephalometric measurements from initial to final time points for the single-phase treatment group. SNA, ANB, U1NAdeg, PogNBmm, and FMA were significant (p ,; 0.01). 52 There were several significant cephalometric changes between single-and two phase treatments (either initial to final or middle to final) including ANB, SNB, and UlNAdeg (TABLE 9). ANB is the most common cephalometric measurement analyzed to determine a skeletal Class II malocclusion and the change in ANB from initial and final time points can indicate the effectiveness of treatment. In this study, ANB change from initial to final time points was significant (p ,; 0.01) between groups with more correction occurring in the two-phase treatment. This was a new finding compared to the previous studies by Lee, Fields, MacFarlane, UNC, and UF. This treating orthodontist continued phase I treatment until a Class I molar was achieved or until the patient was ready for phase 2 while some of the previous treating orthodontists discontinued treatment after a certain amount of time. This may have contributed to the greater amount of ANB correction compared with previous studies, however is difficult to determine with a small sample size. Additionally, this orthodontist teaches cephalometries to orthodontic residents at USC and is probably more particular about achieving ideal measurements than the average orthodontist. Therefore, the significant changes found in this study may not accurately represent the outcomes of the general population of orthodontists. More data is necessary to conclude that two-phase treatment results in greater correction of ANB compared to single-phase treatment. SNA was also found to change more in 53 two-phase than during one but the difference was not great enough to show significance. No significant cephalometric differences were found between single-phase and two phase within extractions or non-extraction groups (TABLE 10 and 11). Table 12 shows that cephalometric measurements are independent of phase. MOLAR SEVERITY One of the main arguments for phase I treatment is the timely use of growth to correct a Class II malocclusion to a Class I molar relation. The treating orthodontist whose records were analyzed for this investigation treated Class II phase I patients until a Class I molar was achieved (or until the patient was ready for phase II) regardless of length of time. There was a significant difference in molar relationship between the initial time point of two-phase treatment and the beginning of the second phase of (middle time point) with molar severity reduced from 0.7±0.2 to 0.1±0.2 (TABLE 13). This study confirms the presumed advantage of correcting the Class II dental relation prior to the start of phase II in order to have a simpler problem list to address with full appliances than single-phase treatment. HEADGEAR This study did not find a significant difference in ANB change between headgear and non-headgear groups. Both groups had significant ANB changes from initial to final 54 time points with or without the use of headgear for growth modification (TABLE 15). The non-headgear group did however have a 42.1% extraction rate while the headgear group had an extraction rate of only 11.5%. It cannot be concluded that the use of headgear reduces the need for extraction but rather could be the result of an extraction treatment plan for Class II correction over headgear because further growth was not expected at the time of consultation. Further study of the relationship between headgear use and extraction rate is needed. TREATMENT TIME Studies conducted by the University of Florida, the University of North Carolina, Lee, and MacFarlane collectively concluded that two-phase treatment was less efficient and took significantly longer to complete than single-phase treatment. In this study, total treatment time for patients treated in two-phases (46.3m ± 7.7) was also significantly longer than one-phase (31.1m ± 8.4 )(p ,; 0.01 )(TABLE 16). This is likely due to the fact that this particular orthodontist treats phase I Class II malocclusion until a Class I molar is achieved. Additionally, patient compliance is one of the most important factors of headgear use and the most difficult for the orthodontist to control. Patients were not eliminated from this study due to poor cooperation and therefore may have also contributed to the increase in length of treatment time. According to previous studies, a justification for two-phase treatment is a shorter treatment in fixed appliances. The significant difference in treatment time between 55 single-phase (31.1m ± 8.4) and phase II (24.4m ± 6.3) of two-phase treatment (p ,; 0.01) observed in this study confirms this assumption. The University of Florida study also observed that patients treated in two-phases spent six months less in fixed appliances than the single-phase group. However, the single-phase treatment group in our study had many outliers, one as high as 62 months, that may have skewed the data to make the second phase of the two-phase group appear more efficient than it was (FIGURE 9). According to Proffit, early treatment was not much more efficient than one-phase as it only produced a slight reduction in the second phase of treatment and an overall treatment time much greater than single-phase treatment.1.2 AGE AND GENDER The mean age at the start of single-phase treatment was significantly younger for female (11.4y ±1.3) patients than male (12.6y ±1.3). This observation is consistent with trend that the male growth spurt occurs two years later than the female and therefore was expected (TABLE 19). Two-phase treatment in this study began for male and female patients at the ages of 9.4y ±0.9 and 9.3y ±1.1, respectively. Hand-wrist radiographs were not taken in order to assess each patient's personal skeletal age and peak height velocity, 56 however the chronological ages were similar to those of the University of Florida (9.6 ±0.8) and University of North Carolina (9.9y) studies.3.4 .. S .6,21. 23, s o 57 CHAPTER 7: CONCLUSIONS The results of this study conclude that two-phase Class II treatment does not have a statistically significant advantage over single-phase treatment. Cephalometric measurements were also determined independent of premolar extraction. PRIMARY CONCLUSIONS: 1. There was no significant difference in extraction rate between two-phase and single-phase Class II treatment. The single-phase treatment group had an extraction rate of 18.6% (13 out of 70 patients) while the extraction rate for the two-phase group was 13.9% (5 of the 36 patients)(p-value 0.543). 2. Significant differences were found within the two treatment groups between time points: a. Within the two-phase treatment group (initial to middle): i. ANB: decreased from 5.8 to 3.9 degrees ii. U1NAdeg: increased from 19.1 to 22.9 degrees b. Within the two-phase treatment group (initial to final): i. SNA: decreased from 81.9 to 79.9 degrees ii. ANB: decreased from 5.8 to 2.8 degrees iii. U1NAdeg: increased from 19.1 to 26.4 degrees iv. PogNBmm: advanced from 0.9 to 1.9 mm v. IntAng: decreased from 129.9 to 123.8 degrees vi. FMA: decreased from 31.1 to 27.7 degrees 58 vii. IMPA: decreased from 81.9 to 79.9 degrees c. Within the single-phase treatment group: i. SNA: decreased from 82.2 to 80.7 degrees ii. ANB: decreased from 4.5 to 3.0 degrees iii. U1NAdeg: increased from 21.5 to 25.1 degrees iv. PogNBmm: advanced from 1.7 to 1.8 mm v. FMA: decreased from 28.5 to 26.0 degrees 3. There was a significant difference in ANB change between two-phase and single phase treatment groups, with more correction occurring in the two-phase treatment (initial to final): a. Two-phase treatment group: decreased from 5.8 to 2.8 degrees b. Single-phase group: decreased from 4.5 to 3.0 degrees 4. There was not a significant change in cephalometric measurements between one-and two-phase treatment within the extraction and non-extraction groups. 5. The headgear and non-headgear groups both had a significant change in ANB from initial and final time points, however, there was no significant difference in ANB change between the two groups. 6. The difference in total treatment time was significant between the two-phase and single-phase groups with two-phase treatment taking longer to complete. The total treatment time for single-phase was 31.1 months, and 46.3 months for two-phase treatment. 59 SECONDARY CONCLUSIONS: 1. There was a significant difference in starting age for single-phase treatment between male and female patients: a. Male: 12.6y ±1.3 b. Female: 11.4y ±1.3 2. There was no significant difference in total treatment time between male and female patients. 60 CHAPTER 8: LIMITATIONS The limitations of this study were: 1. Some results of this study may be skewed due to the small sample size that allowed outliers to have a meaningful impact. 2. A single private practice office in Southern California provided all of the records for this study and therefore may not accurately represent the total population. 3. Due to the nature of this retrospective study, a control group was not available to evaluate the changes achieved with early treatment compared to the natural growth and self-correction of an untreated patient during the same amount of time. 4. Compliance was not screened for or evaluated. Treatment time, headgear results, molar severity, and possibly some cephalometric measurements may have been affected by poor patient compliance. Compliance is difficult to assess but vitally important to the success of some treatment plans and therefore worth considering in further investigations. 61 REFERENCES 40 Adenwalla ST, Kronman JA. Class II, Division I treatment with Frankel and edgewise applia nce: a comparative study of mandibular growth and facial esthetics. Angle Orthod 1985; 55:281 -98. 57 Baccetti T, Lorenzo F, Stahl F. Comparison of 2 comprehensive Class II treatment protocols including the bonded Herbst and headgear applia nces: A double-b lind study of consecutively treated patients at puberty. Am J Orthod Dentofacial Orthop 2009; 135:698.e1-6 98.e10 66 Baccetti T, Franchi L, Kim L. Effect of timing on the outcomes of 1- phase nonextraction therapy of Class II malocclusion. 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A comparison of premolar extraction rates in single -phase versus twophase treatment of Class II malocclusions. Master's Thesis, University of Southern California; May 20 II. 16 MacGregor FC. Social and psychological implications of Dentofac ial disfigurement. Angle Orthod 1970; 40:23 1-233. 47 Marchner JF, Harris JE. Mandibular growth and Class II treatment. Angle Orthod 1966; 36:89-93. 64 60 Mao J, Zhao H. The correction of Class II, division 1 malocclusions with bionator headgear combination appliance. J Tongii Med University 1997; 17:254-6 . 8 McDonald FT. The inf luence of age on patient cooperation in orthodontic treatment. Dent Abstr 1973; 18:52. 10 McEwen, JD, McHugh WD, Hitchin AD. Fractured maxillary central incisors and incisal relationships. J Dent Res 1967; 46:1290. 38 McNamara JA, Bookstein FL, Shaughne ssy TG. Skeletal and dental changes following functional regulator therapy on Class II patients . Am J Orthod 1985; 88:91 -110. 48 Moore A W. Observa tions on facial growth and its clinical significanc e. Am J Orthod 1959; 45:399-4 23. 53 O'Brien K, Macfarlane T, Wright J, Conboy F, et a!. Early treatment for Class II malocclusion and perceived improvements in facial prof ile. Am J Orthod Dentofacial Orthop 2009; 135(5):580-5. 39 O'Brien K, Wright J, Conboy F, Sanjie Y, Mandall N, Chadwick S, et a!. Eff ectiveness of treatment for Class II malocclusion with the Herbst or Twin -block applia nces: a randomized, controlled trial. Am J Orthod Dentofacial Orthop 2003; 124: 128-37. 49 O'Brien K, Wright J, Conboy F, Chadwick S, Connolly I, Cook P, et a!. Eff ectiveness of early orthodontic treatment with the Twin- block applia nce: a multicenter, randomized, contro lled trial. Part 1: dental and skeletal eff ects. Am J Orthod Dentofacial Orthop 2003; 124: 234-43. 50 O'Brien K, Wright J, Conboy F, Chadwick S, Connolly I, Cook P, et a!. Eff ectiveness of early orthodontic treatment with the Twin- block applia nce: a multicenter, randomized, contro lled trial. Part 2: psychosocial eff ects. Am J Orthod Dentofacial Orthop 2003; 124: 488 -94. 64 O'Brien K, Wright J, Conboy F, Apple be P, Davies L, Connolly I, et a!. Early Treatment for Class II Division 1 malocclusion with the Twin -block appliance: A multi -c entered, randomized, contro lled trial. Am J Orthod Dentofacial Orthop 2009; 135(5):573 -79. 11 O'Mullane, DM. Some factors predisposing to in juries of permanent incisors in school children. Brit Dent J 1973; 134:328-32. 65 54 Owen AH. Maxilla ry incisolabial responses in class II, division I treatment with Frankel and edgewise applia nces. Angle Orthod 1986;56:67-8 7. 55 Pancherz H, Aneh us -Pancherz M. The headgear eff ect of the Herbst applia nce: a cephalometric long- term study. Am J Orthod Dentofac Orthop 1993;103:510-2 0. 36 Poulton DR. A three -year study of Class II malocclusion with and without headgear therapy. Angle Orthod 1967; 34:181 -93. 2 Proffit WR. The timing of early treatment: An overview. Am J Orthod Dentofac ial Orthop 2006; 129: S47 -9. I Proffit WR, Tulloch JF. Preadolescent Class II problems: treat now or wait? Am J Orthod Dentofacial Orthop 2002; 121 :560-2. 46 Righellis EG. Treatment eff ects of Frankel, activator, and extra-oral traction applia nces. Angle Orthod 1983; 53: 107-21. 51 Schulhof RJ, Engle GA. Results of Class II functional appliance treatment. J Clin Orthodl982; 16:587-99. 13 Shaw, WC. The inf luence of children's Dentofac ial appearance on their social attractiveness judged by peers and by adults. Am J Orthod 1981; 79-399-415. 14 Shaw WC, Meek SC, Jones DS. Nicknames, teasing, harassment and the salience of dental fe atures among school children. Brit J Orthod 1980; 7:75 -8 0. 37 Stahl F, Baccetti T, Franchi L, McNamara J. Longitudinal growth changes in untreated subject with Class II Division I malocclusion. Am J Orthod Dentofacial Orthop 2008; 134: 125 -37 23 Tulloch JF, Phillips C, Proffit WR. Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial. Am J Orthod Dentofacial Orthop 1998; 113 :62 -7 2. 4 Tulloch JF, Proffit WR, Phillips C. Influences on the outcome of early treatment for Class II malocclusion. Am J Orthod Dentofacial Orthop 1997; Ill :533-4 2. 59 Tulloch JF, Medland W, Tuncay OC. Methods used to evaluate growth modification in Class II malocclusion. Am J Orthod Dentofacial Orthop 1990; 98:340-7. 66 3 Tulloch JF, Phillips C, Koch G, Proffit WR. The eff ect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial. Am J Orthod Dentofacial Orthop 1997; 111:391 -400. 25 Tulloch JG, Proffit WR, Phillips C. Outcomes in a 2 -phase randomized clinical trial of early Class II treatment. Am J Orthod Dentofacial Orthop 2004; 125:657-67. 63 Turpin DL. The long- waited Cochrane review of2-p hase treatment. Am J Orthod 2007; 132(4):423-24. 65 von Breman J, Pancherz H. Eff icency of early and late Class II Division I treatment. Am J Orthod Dentofacial Orthop 2002; 121:31 -37 9 Weisla nder L. Early or late cervical traction therapy of Class II malocclusion in the mixed dentit ion. Am J Orthod 1975; 67:432-439. 17 Weiss J, Eiser, HM. Psychological timing of orthodontic treatment. Am J Orthod 1977; 72 :198-204. 5 Wheeler TT, McGorray SP, Dolce C, Taylor MG, King GJ. Eff ectiveness of early treatment of Class II malocclusion. Am J Orthod Dentofacial Orthop 2002; 121:9-17. 6 Wheeler TT, McGorray SP, Dolce C, King GJ. The timing of Class II treatment. Am J Orthod 2006; 129( 4):S65 -70. 52 Wijayaratne D, Harkness M, Herbison P. Functional appliance treatment assessed using the PAR index. Aust Orthod 2000; 16:1 18-126. 67
Abstract (if available)
Abstract
INTRODUCTION: The timing of treatment for Class II malocclusion has been heavily studied yet still remains to be a controversial clinical issue. This study specifically evaluates the ability of Class II growth modification to prevent the need for premolar extraction and the effect it has on cephalometric measurements. ❧ MATERIALS AND METHODS: Patient records from the private practice office of an American Board of Orthodontics diplomate in Southern California were evaluated for this study. A total of 106 patient records were examined, 36 were treated in two-phases and 70 were treated in a single-phase. The complete records of each patient were analyzed to compare premolar extraction rates between the two treatment groups and their resulting cephalometric measurements. ❧ RESULTS: There was no significant difference in extraction rate between two-phase and single-phase treatment. The single-phase treatment group had an extraction rate of 18.6% (13 out of 70 patients) while the extraction rate for the two-phase group was 13.9% (5 of the 36 patients)(p-value 0.543). The change in ANB was the only significant cephalometric difference between two-phase and single-phase treatment with more change occurring in two-phase treatment. ❧ CONCLUSION: The results of this study conclude that two-phase Class II treatment does not reduce the rate of premolar extraction by a significant amount. In addition, early orthodontic treatment does not affect cephalometric outcomes, with the exception of ANB.
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Harshbarger, Laura T.
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Comparison of premolar extraction rates between one-phase and two-phase class II malocclusion
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School of Dentistry
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Craniofacial Biology
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04/30/2012
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02/06/2012
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class II,extraction rate,OAI-PMH Harvest,two-phase treatment
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Sameshima, Glenn T. (
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