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Effects of Class II Treatment on Third Molar Angulation and Anterior PAR Component

Permanent Link: http://ufdc.ufl.edu/UFE0022251/00001

Material Information

Title: Effects of Class II Treatment on Third Molar Angulation and Anterior PAR Component
Physical Description: 1 online resource (33 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

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Subjects / Keywords: Dentistry -- Dissertations, Academic -- UF
Genre: Dental Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The purpose of this study was to follow the development of the 3rd molar with age, compare differences in 3rd molar angulation amongst headgear/biteplane, bionator, and observation groups; and to compare incisor PAR index to the 3rd molar angulation. This study is a retrospective extension derived from a previous prospective, longitudinal, randomized clinical trial. Angulations of the 3rd molars were measured at the end of Phase I (DC-3), post-Phase I (DC-5), baseline at Phase II (DC-7), end of Phase II (DC-F), one year into retention (DC-R1), and two years into retention (DC-R2). A total of 807 panoramic films were measured. Angulations of lower 3rd molars were compared at each time point among the three treatment groups using both Kruskal-Wallis and Analysis of Variance tests. Lower and upper anterior PAR indices were compared to the respective lower or upper 3rd molar angulation. Spearman correlation of coefficients was used for both the average 3rd molar angulation per arch and the most extreme 3rd molar angulation. The lower 3rd molar?s angulation did not differ significantly between treatment groups at time points DC-3, DC-5, DC-7, DC-F, DC-R1, or DC-R2. The lower anterior PAR index had a mild positive correlation at DC-F with a mesial angulation of the lower 3rd molar. The highest significant correlation (r=0.18795, p= 0.0156) was found when the Spearman correlation of coeffiecients was used with the most extreme lower 3rd molar angulation. The bionator group was the only treatment group at DC-F which showed any correlation with 3rd molar angulation and PAR index. It revealed a mild correlation with anterior PAR index increasing with mesial angulation of lower 3rd molars (r=0.30659, p=0.303) and distal angulation of the upper 3rd molars (r=-0.33849, p=0.0141). Neither bionator nor headgear/biteplane Phase I treatment appears to influence significantly upon the angulation of the developing 3rd molars. The only statistically significant correlation 3rd molar angulation had with anterior PAR component was found at the end of Phase II treatment, where clinical significance is most likely low since teeth should be aligned at this stage.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Dolce, Calogero.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

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Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022251:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022251/00001

Material Information

Title: Effects of Class II Treatment on Third Molar Angulation and Anterior PAR Component
Physical Description: 1 online resource (33 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: Dentistry -- Dissertations, Academic -- UF
Genre: Dental Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The purpose of this study was to follow the development of the 3rd molar with age, compare differences in 3rd molar angulation amongst headgear/biteplane, bionator, and observation groups; and to compare incisor PAR index to the 3rd molar angulation. This study is a retrospective extension derived from a previous prospective, longitudinal, randomized clinical trial. Angulations of the 3rd molars were measured at the end of Phase I (DC-3), post-Phase I (DC-5), baseline at Phase II (DC-7), end of Phase II (DC-F), one year into retention (DC-R1), and two years into retention (DC-R2). A total of 807 panoramic films were measured. Angulations of lower 3rd molars were compared at each time point among the three treatment groups using both Kruskal-Wallis and Analysis of Variance tests. Lower and upper anterior PAR indices were compared to the respective lower or upper 3rd molar angulation. Spearman correlation of coefficients was used for both the average 3rd molar angulation per arch and the most extreme 3rd molar angulation. The lower 3rd molar?s angulation did not differ significantly between treatment groups at time points DC-3, DC-5, DC-7, DC-F, DC-R1, or DC-R2. The lower anterior PAR index had a mild positive correlation at DC-F with a mesial angulation of the lower 3rd molar. The highest significant correlation (r=0.18795, p= 0.0156) was found when the Spearman correlation of coeffiecients was used with the most extreme lower 3rd molar angulation. The bionator group was the only treatment group at DC-F which showed any correlation with 3rd molar angulation and PAR index. It revealed a mild correlation with anterior PAR index increasing with mesial angulation of lower 3rd molars (r=0.30659, p=0.303) and distal angulation of the upper 3rd molars (r=-0.33849, p=0.0141). Neither bionator nor headgear/biteplane Phase I treatment appears to influence significantly upon the angulation of the developing 3rd molars. The only statistically significant correlation 3rd molar angulation had with anterior PAR component was found at the end of Phase II treatment, where clinical significance is most likely low since teeth should be aligned at this stage.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Dolce, Calogero.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022251:00001


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EFFECTS OF CLASS II TREATMENT ON THIRD MOLAR ANGULATION AND ANTERIOR PAR COMPONENT By NOELLE F. WILLIAMS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008 1

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2008 Noelle F. Williams 2

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To my mom Karen for her continuing support. To my cat Cricket for putting up with my absence. 3

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ACKNOWLEDGMENTS I sincerely thank Dr. Calogero Dolce, Dr. Timothy Wheeler, Dr. Sue McGorray, and Marie Taylor for their help and efforts in the making of this research project. 4

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TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........6 LIST OF FIGURES.........................................................................................................................7 ABSTRACT.....................................................................................................................................8 CHAPTER 1 INTRODUCTION................................................................................................................. .10 2 MATERIALS AND METHODS...........................................................................................14 Subjects...................................................................................................................................14 Methods..................................................................................................................................14 Data Analysis..........................................................................................................................15 3 RESULTS...................................................................................................................... .........16 4 DISCUSSION................................................................................................................... ......23 5 CONCLUSION................................................................................................................... ....28 LIST OF REFERENCES...............................................................................................................29 BIOGRAPHICAL SKETCH.........................................................................................................33 5

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LIST OF TABLES Table page 3-1 Subject characteristics by treatment group........................................................................19 3-2 Average age of subjects, number of 3rd molars measured per data collection point, and number of subjects who had all 3rd molars removed...................................................19 3-3 Correlation values between 3rd molar angulation and ante rior PAR component at various time points............................................................................................................ .22 3-4 Correlation values between 3rd molar angulation and anteri or PAR component at DC-F based on treatment group.........................................................................................22 6

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LIST OF FIGURES Figure page 3-1 Mean lower 3rd molar angulation per time point...............................................................20 3-2 Mean upper 3rd molar angulation per time point..............................................................20 3-3 Mean lower 3rd molar angulation per time point examining Phase I treatment group.....21 3-4 Mean upper 3rd molar angulation per time point examining Phase I treatment group.....21 7

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Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EFFECTS OF CLASS II TREATMENT ON THIRD MOLAR ANGULATION AND ANTERIOR PAR COMPONENT By Noelle F. Williams, DMD May 2008 Chair: Calogero Dolce, DMD, PhD Major: Dental SciencesOrthodontics The purpose of this study was to follow the development of the 3rd molar with age, compare differences in 3rd molar angulation amongst hea dgear/biteplane, bionator, and observation groups; and to compare incisor PAR index to the 3rd molar angulation. This study is a retrospective extension derive d from a previous prospective, longitudinal, randomized clinical trial. Angulations of the 3rd molars were measured at the end of Phase I (DC-3), post-Phase I (DC-5), baseline at Phase II (DC7), end of Phase II (DC-F), one year into retention (DC-R1), and two years into retention (DC-R2). A total of 807 panoramic films were measured. Angulations of lower 3rd molars were compared at each time point among the three treatment groups using both Kruskal-Wallis and Analysis of Variance tests. Lower and upper anterior PAR indices were compared to the respective lower or upper 3rd molar angulation. Spearman correlation of coefficients was used for both the average 3rd molar angulation per arch and the most extreme 3rd molar angulation. The lower 3rd molars angulation did not differ signi ficantly between treatment groups at time points DC-3, DC-5, DC-7, DC-F, DC-R1, or DC-R2. The lower anterior PAR index had a 8

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mild positive correlation at DC-F with a mesial angulation of the lower 3rd molar. The highest significant correlation (r=0.18795, p= 0.0156) was found when the Spearman correlation of coeffiecients was used with the most extreme lower 3rd molar angulation. The bionator group was the only treatment group at DC-F which showed any correlation with 3rd molar angulation and PAR index. It revealed a mild correlation w ith anterior PAR index increasing with mesial angulation of lower 3rd molars (r=0.30659, p=0.303) and distal angulation of the upper 3rd molars (r=-0.33849, p=0.0141). Neither bionator nor headgear/biteplane Phase I treatment appears to influence significantly upon the angulat ion of the developing 3rd molars. The only stat istically significant correlation 3rd molar angulation had with anterior PAR component was found at the end of Phase II treatment, where clinical significance is most likely low since teeth sh ould be aligned at this stage. 9

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CHAPTER 1 INTRODUCTION Third molars are first able to be seen on a panoramic radiogr aph as early as age 5 and as late as age 16 years.1 Gravely,2 Rantanen,3 and Haavikko4 reported that initiation of calcification is typically seen between 6 and 13 y ears of age, with the av erage age being between 9 to 10 years. The completion of the 3rd molar crown was reported at between 11 and 15 years of age. Normal eruption of teeth is exp ected between the ages of 18 and 24 years.5, 6 Rates for mandibular 3rd molar impaction range between 9.5% and 50%.7, 8, 9, 10, 11 Dachi and Howell12 found in a study examining 3874 routine panoramic films that 29.9% of maxillary third molars and 17.5% of mandibular 3rd molars were impacted when present. This study did not find any predilections towards se x or bilateral versus unilateral impaction. As the distance of the retromolar space increases the likelihood of mandibular 3rd molar impaction decreases. For every millimeter increase in the width of the 3rd molar crown, there is a 44% increase in the risk of maxillary 3rd molar impaction.13, 14 Questions regarding extraction of other teeth in the arch influencing the eruptive potential of the 3rd molar have been studied. Richardson15 found that extraction of a lower 2nd molar almost eliminates the occurre nce of a mesioangular lower 3rd molar impaction. Bjork7 noted that the loss of other teeth in the mandible may im prove the chances of eruption of the lower 3rd molars. Further studies focused on the fate of 3rd molar impaction following a premolar extraction among orthodontic patients. Faubion16 concluded that the prevalence of 3rd molar impaction is reduced but not eliminated in cases treated by extraction of premolars by as much as fourfold. Artun17 found that the decision to extract premol ars with orthodontic treatment in the maxilla reduces the risk of 3rd molar impaction by 76% due to the mesial movement of the maxillary molars. Kim18 conducted a study looking at the 3rd molar impaction in orthodontic 10

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patients treated either non-extract ion (n=105) or with the extrac tion (n=53) of four premolar teeth. Non-extraction patients showed higher scores of 3rd molar impaction, less mesial movement of the molars from before treatment to after treatment, and a smaller retromolar space in both arches compared to extraction patients. Staggers19 study looked at first premolar extraction and found that, unlike the study on second pr emolar extraction, the 3rd molar angulation and eruption during a nd after orthodontic treatmen t was not significant between extraction versus non-extraction groups. Angulation plays an important ro le in determining whether a 3rd molar is fated for impaction. Initially, many 3rd molars have a mesial inclinatio n but progressively become more upright to the age of 25.20, 6 Richardsons21 five-year longitudinal st udy looking at 46 children on an annual basis found that the st eeper the angle of the lower 3rd molar to the mandibular plane at age 10 years, the more likely it is to erupt with in the next five years. By measuring the growth of the mandible and comparing the lower 3rd molars which uprighted, Richardson21 found that the change in angulation seemed to be independent of mandibul ar growth. Bjork7 disagrees and believes that the growth of the mandible is an important factor that contributes to making space for the 3rd molar. A controversial subject regarding mandibular impacted 3rd molars is whether they increase the likelihood of lower anterior crowdi ng of the dentition. A survey in 1971 taken by 600 orthodontists and 700 oral surgeons f ound that 65% were under the impression that 3rd molars sometimes produce crowding of the mandibular anterior teeth.22 A survey from 2007 noted that more recent orthodontic graduates ar e less likely to recomm end prophylactic removal of 3rd molars to prevent lower anterior crowding than their counterparts who graduated from residencies in the 1970s and 80s.23 Many studies have looked at whether or not lower 3rd molars 11

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have an impact on anterior alignment. Longit udinal studies have compared subjects based on whether or not a lower 3rd molar was erupted, unerupted, or imp acted. Other studies have merely noted the presence or absence of a lower 3rd molar. A handful of studies have prophylactically removed a lower 3rd molar on one side of the mandible and not on the other side to see if unilateral lower anterior crowding or mesializatio n of the teeth would occur. The conclusions seem to be split down the middle. Half the studies found that lower 3rd molars influenced lower anterior crowding,24, 25, 26 while the other studies did not find a correlation.27, 28, 29 Bergstrom27 also looked at upper 3rd molars and found that they did not appear to have an influence on upper anterior crowding. Early Class II treatment may have an effect on the uprighting of the 3rd molars during development. Studies30, 31, 32 have looked into the anteroposteri or skeletal and dental changes after early Class II treatment w ith headgear and bionator therapie s. Dental effects have shown that headgear causes distal maxillary molar movement and that bionator treatment retracts maxillary incisors.30 OBriens31 study found that for a twin-block appliance used in early Class II treatment that the molar correction was found to be due to 41% skeletal versus 59% dental. Despite a predominant dentoalveolar change, mesi al or distal displacement of the posterior dentition may influence the eruptive potential of the 3rd molar. Keelings30 study looked at 325 subjects randomized to bionator, headgear/biteplane, or observation in an early Class II treatment. Significantly more skeletal Class II correction was found in the bionator and headgear groups compar ed to the observation group. The headgear group showed a more significant dental Class II correction in the maxillary molar and incisor position compared to the bionator. The headgear group also showed a significant molar relapse during the 6-month retention phase This study also found enhanced mandibular growth in both 12

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the headgear and bionator groups. Turkkahraman and Sayins33 study looking at activator as well as activator headgear treatment found that both encouraged mandibular growth, lengthening the mandible by approximately 3 mm. Th is study agrees with Tulloch et al34 that long-term benefit of achieving early greater growth compared to untreated subjects still remains to be confirmed. This early treat ment may encourage the 3rd molar to develop in a more favorable position. The purpose of this study was to evalua te the changes in angulation of the 3rd molar during its development, the influences bionator or headgear/biteplane treatment may have on the angulation of the developing 3rd molar, and if upper and lower anterior crowding PAR components are correlated to 3rd molar angulation. 13

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CHAPTER 2 MATERIALS AND METHODS Subjects The subjects were part of a previous prosp ective, longitudinal, randomized clinical trial designed to examine and report the effectivene ss of early treatment with bionator or with headgear/biteplane in patients with Class II malocclusion. Changes were compared over a similar time period to an observation control grou p. A stratified block randomization procedure was used to assign a treatment pr otocol during Phase-1 for each patient. Strata was defined by severity of Class II malocclusion, need for prep aratory treatment, mandibular plane angle, race, and gender. After completing Phase-1, both treatment and control groups underwent fixed appliances in Phase-2, followed by a retentio n/follow-up period. The study design and subject selection are described in detail in the previous publication.32 Methods Angulations were calculated on the panoramic film for both maxillary and mandibular 3rd molars exhibiting at least 1/3 crown calcification development at data collection (DC). Time points included the end of Phase I (DC-3), post-Ph ase I where the subjects were randomized for 6 months into retention or no retention, follo wed by all subjects with no retention for an additional 6 months (DC-5), baselin e at Phase II ( DC-7), end of Phase II (DC-F), one year into retention (DC-R1), and two years into retention (DC-R2). First and third molar templates were made from the best developed panoramic film fo r each patient in each quadrant. Two points on the occlusal surfaces of each molar were marked on the template. The templates were then overlayed on each panoramic film and the two points of the 1st and 3rd molar were marked in each quadrant. The crown of the 1st molar was used as a reference for the occlusal plane. The CalComp Drawing Board III digitizer was use to m easure an x and y axis on the occlusal table 14

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of each 1st and 3rd molar crown in order to calculate th e angulation. Positive measurements indicate mesially inclined molars. One examin er collected all of the measurements. Intraexaminer reliability was tested by measuring fifteen panoramic films two weeks apart. Measurements were within 5 degrees at 95.89% of the calibration measurements. The upper and lower anterior PAR indices were taken from a previous study on the same subjects.35 Data Analysis Relationships between angulation and treatm ent group were examined with KruskallWallis and Analysis of Variance tests with a p-value less than 0.05 considered statistically significant. Spearmans Correla tion of Coefficients was used to examine any relationship between 3rd molar angulation and anterior PAR indices. 15

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CHAPTER 3 RESULTS Time points DC-3, DC-5, DC-7, DC-F, DC-R1 and DC-R2 were chosen to analyze based on a sufficient number of panoramic films available to measure where 3rd molars had at least 1/3 of their crowns calcified. The sample consisted of 239 subjects in th e Class II study, whose 3rd molar angulation was calculated at one or more of the time points under consideration. The Class II study randomly distributed 325 subjec ts into bionator, headgear/biteplane, and observation groups based on gender, race, severity of molar classi fication, pre-treatment, and retention post-phase I treatment. Since th e 239 subjects analyzed in this study was a subpopulation of the larger study, analyses were pe rformed to see if thes e variables were still well distributed. No bias was found among the di stributions, with p-va lues well above 0.05 as shown in Table 3-1. Table 3-2 shows the actual number and percentage of the 807 panoramic films analyzed at each time point. Table 3-2 also displays the mean age for the subjects at each time point, the total number of lower and upper 3rd molars measured, and data collection time points where 3rd molars had been extracted since the previous pa noramic taken. A larger number of films were available at time points DC-7, DC-F, and DC-R1. Many 3rd molars did not have 1/3 of their crown calcified at the earlier time points (DC-3 and DC-5) and subjec ts were either lost to follow up or had their 3rd molars extracted by the later time point (DC-R2). Only 9 of the 239 subjects had their 3rd molars extracted. Ninety-thr ee percent had all third 3rd developing, while 18 of the 239 subjects, or approximately 7.53%, were congenitally missing at least one 3rd molar. Figure 3-1 depicts the mean angulation of the combined left and right lower 3rd molars per time point, regardless of their treatment or control group. The term uprighting will describe a 3rd molar that has a mesial angulation but less so than its original angulation. The lower 3rd 16

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molars in DC-3 were approximately 4 degrees more mesially angulated than the lower 3rd molars measured in DC-R2. Figure 3-2 reveals that the mean angula tion of the upper 3rd molars at DC-3 were approximately 12 degrees more mesial than the upper 3rd molars measured in DC-R2. It should be noted that not all 3rd molars were measured at each time point analyzed. The average angulation of the 3rd molars broken down into tr eatment/control groups is shown in Figure 3-3 and 3-4. No significance between angulation among treatment groups were found for any of the time points analyzed using both Kruskal Wallis and Analysis of Variance methods. The bionator group did not show a mean change in lower 3rd molar angulation from DC-3 through DC-F, but did show an uprighting of approximately 4 degrees two years into retention (41.21 to 36.61 degrees and 42.84 to 31.15 degrees respectively). The control group showed a 1 degree increase in mesial angulati on between DC-3 and DC-F with this angulation staying stable two years into retention. The headgear/biteplane gr oup showed the largest uprighting effect with a 4 de gree change between DC-3 and DC-F (42.84 to 38.99 degrees) and then an additional 7 degrees of uprighting tw o years into retenti on (31.15 degrees). In regards to the upper 3rd molar both the bionator and cont rol group had a few degrees of increased mesial angulation be tween DC-3 and DC-F, followed by a few degrees of uprighting which left them close to their original DC-3 a ngulation two years into re tention. The headgear group displayed a mean 3 degrees of upright ing between DC-3 and DC-F (34.91 to 31.09 degrees), followed by an additional 2 degrees of uprighting two year s into retention (29.29 degrees). Mandibular and maxillary anterior crowding based on the PAR index was assessed from casts taken at the six DC time points analyzed. Sp earman Correlation of Coefficients was used to determine if the angulation of the 3rd molar influenced the ante rior crowding PAR component. 17

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No significant correlation wa s found between the lower 3rd molar angulation and the lower anterior crowding PAR component at time points DC-3, DC-5, DC-7, DC-R1, and DC-R2. DCF showed a p-value under 0.05 using Spearman Correlation of Coefficients finding a positive correlation value of 0.15544, as shown in Table 3-3. The mandibular an terior crowding PAR component was also evaluated based on the most severely (maximum) lower 3rd molar angulation, rather than the averag e of the two in the mandible. Again, no significant correlations were found at time points DC-3, DC-5, DC-7, DC-R1, and DC-R2. DC-F again showed a pvalue under 0.05, finding a positive correlation va lue of 0.18795. Maxillary anterior crowding PAR component showed no statistically significant co rrelations to either the average or the most severely (maximum) upper 3rd molar angulation at any of the six time points. Time point DC-F was further analyzed according to treatment/control group to assess correlations between 3rd molar angulation and the anterior crowding PAR component, as shown in Table 3-4. Significant correlations between 3rd molar angulation and the anterior crowding PAR component were found in the bionator treated group, but not in the headgear/biteplane or control groups. The average lower 3rd molar angulation and mandibul ar anterior crowding PAR component showed no statistica lly significant correl ation, but the most severely (maximum) lower 3rd molar angulation and mandibular ante rior crowding PAR component showed a statistically significant positive correlation of 0.30649. Although upper 3rd molar did not find any significant correlations overall in DC-F when all treatment groups were combined, it was found that when looking at both the average a nd most severely (maximum) angulated upper 3rd molar of the bionator group there was a signific ant negative correlation to maxillary anterior crowding PAR component of 0.33749 and -0.32754 respectively. 18

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Table 3-1 Subject characteristics by treatment group. Characteristic Bionator Control Headgear/Biteplane (n=78) (n=78) (n=93) P-value Sex (% female) 37.18% 37.18% 42.17% 0.7530 Race (% white) 88.46% 91.03% 93.98% 0.4652 Initial molar class severity# % mild 31% 28% 31% % moderate 27% 26% 24% 0.9822 % high 42% 46% 45% No Pre-Treatment 49% 87% 51% <0.0001 B vs. HG/BP 0.8100 No Retention after Phase I treatment 51% 100% 48% <0.0001 B vs. HG/BP 0.6952 # definition of initial molar class severity: mild (bilateral cusp), moderate (at least one side cusp), or severe (at least one side full cusp). Table 3-2. Average age of subjects, number of 3rd molars measured per data collection point, and number of subjects who had all 3rd molars removed. Data Collection #Panoramic Age (years) Lower Third Upper Third 3rd Molars Films Measured Molars Measured Molars Measured Extracted End Phase I 98 12.05 156 183 (DC-3) Retention Post Phase I 164 12.93 270 313 (DC-5) Baseline at Phase II 178 13.51 296 340 (DC-7) End of Phase II 175 15.53 320 332 5 (DC-F) One Year into Retention 93 16.60 163 184 3 (DC-R1) Two Years into Retention 99 17.21 185 189 1 (DC-R2) 19

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20 25 30 35 40 45 50 55 60 DC-3 DC-5 DC-7 DC-F DC-R1 DC-R2 Time PointMean Lower Third Molar Angulation Figure 3-1 Mean lower 3rd molar angulation per time point. 10 15 20 25 30 35 40 45 50 DC-3 DC-5 DC-7 DC-F DC-R1 DC-R2 Time PointMean Upper Third Molar Angulation Figure 3-2 Mean upper 3rd molar angulation per time point. 20

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0 10 20 30 40 50 60 70 DC3 DC-5 DC-7 DC-F DC-R1 DC-R2 Time PointDegrees Bionator Control Headgear Figure 3-3 Mean lower 3rd molar angulation per tim e point examining Phase I treatment group. 0 10 20 30 40 50 60 DC-3 DC-5 DC-7 DC-F DC-R1 DC-R2 Time PointDegrees Bionator Control Headgear Figure 3-4. Mean upper 3rd molar angulation per time point examining Phase I treatment group. 21

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Table 3-3 Correlation values between 3rd molar angulation and ante rior PAR component at various time points. Time Point Average Lower 3rd Molar Average Upper 3rd Molar Angulation Angulation DC-3 0.881 0.8056 DC-5 0.1159 0.1213 DC-7 0.6847 0.9351 DC-F 0.0462* (0.15544) 0.0156* (0.18795) DC-R1 0.5269 0.5375 DC-R2 0.1651 0.4143 Spearman Correlation of Coefficient value (* Significant p-value) Table 3-4. Correlation values between 3rd molar angulation and anteri or PAR component at DC-F based on treatment group. Bionator Control Headgear/BP Average Lower 0.138 0.8524 0.0697 Maximum Lower 0.0303* (0.30659) 0.8868 0.0706 Average Upper 0.0144* (-0.33749) 0.3282 0.8321 Maximum Upper 0.0178 (-0.32754) 0.4897 0.3457 Spearman Correlation of Coefficient value (*Significant p-value) 22

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CHAPTER 4 DISCUSSION The purpose of this study was to evaluate three things. One being the changes in angulation of the 3rd molar during its development, the sec ond looking at influences bionator or headgear/biteplane treatment may have on the angulation of the developing 3rd molar, and the third to find if upper and lower anterior cr owding PAR components are correlated to 3rd molar angulation. The subjects in this study were Class II patients en rolled in a 2-phase orthodontic treatment where Phase I consisted of bionator, headgear/biteplane, or an observation control group. Of the 239 subjects analyzed in this st udy, approximately 91% were Caucasian and 62% were males. The first time point analyzed was DC-3, bei ng that at this point a sufficient number of panoramic films had 1/3 crown calcification of their 3rd molars. Unfortunately, DC-3 is when Phase I treatment has completed and a baseline prio r to treatment was not av ailable. At least one 3rd molar was congenitally missing in 18 of the 239 subjects studied. Richardson43 reported that 9-20% of the population is conge nitally missing at least one 3rd molar, which is greater than the 7.53% found in our study. The trend for lower 3rd molar uprighting between DC-3 and DC-R2 are in agreement with the general consensus of 3rd molar development6, 20, although these subjects and 3rd molars were not one hundred percent coincident and this trend may be misleading. The upper 3rd molar angulation showed a mean uprighting between DC-3 and DCR2. Standard deviation ranges for the means of both lower and upper 3rd molars encompasses the changes measured. No statistically signif icant angulation differences of the lower or upper 3rd molars were found between the bionator, headgear/biteplane, or control treatment groups between the six time points analyzed. Class II early tr eatment should therefore not be chosen on the assumption that 23

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the 3rd molar angulation will be influenced enough to allow eruption of the tooth. Multiple papers have found that the mandibular length incr eases in bionator or ac tivator treatment when compared to controls.36, 37, 38 Other papers have suggested that an increase in mandibular length would also increase the retrom olar space and promote lower 3rd molar eruption.13, 39 Keeling30 found that headgear/biteplane treatment enhanced mandibular growth, but multiple other studies have concluded that headgear treatment does no t significantly influence mandibular length.36, 40, 41, 42 OBrien31 found that twin-block Phase I appliances contributed to Class II correction mainly through dentoalveolar effects, which theoretically would encourage mandibular 3rd molar uprighting and maxillary 3rd molar distalization. Our study did not find a statistically signi ficant difference between mandibular molar uprighting in the headgear group versus the control, although from DC-3 to DC-R2 the headgear/biteplane group uprighted 11 degrees in comparison to the control group which increased its mesial angulation by 1 degree. There may not be a statistical significance when looking at each treatment group per time point, but the overall effect from DC-3 through DC-R2 may hold clinical significance. The bionator group did not show any uprighting effect between DC-3 through DC-F, but mandibular molars did up right a mean of 2 degrees two years into retention. Artuns44 study examining non-extraction orthodon tically treated subjects found the mandibular 3rd molar increased in mesial angulation approximately 7.56 degrees compared with the mandibular plane during treatment (n=16). Our study found that the mean mandibular 3rd molar will upright in both headg ear and treatment groups in comparison to controls in the long term. Whether or not this small amount of uprighting is enough to prevent the lower 3rd molars impaction is yet to be seen. It should be not ed that each time group had a different number of 24

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subjects whose 3rd molars were analyzed, therefore contam inating the longitudinal nature of the study. Headgear has been shown to cause distalization of th e upper 1st maxillary molar, 26, 30, 32, 33, 34, 36 making us expect the upper 3rd molar to be pushed distal or to have a less likely chance to upright during its development. Although not statistically significant, Figure 3-4 shows that the upper 3rd molar uprighted more in the headgear group than for the bionator or control group. The total uprighting from the end of Phase I until two years out of Phase II was 5.5 degrees. Both bionator and control groups show ed no uprighting between these time points. It should also be noted that the headgear tr eated group had a DC-3 angulation that was 4-6 degrees more mesially inclined than the bionator or control group. It might be that the headgear group was slightly dentally delayed at DC-3 and that this uprighting effect was something that would have occurred despite treatment or an eff ect that had taken place prior to DC-3 in the bionator and control groups. Artuns44 study found that the maxillary 3rd molar increased in mesial angulation by approximately 3.34 degrees (n=28) during non-ex traction orthodontic treatment in adolescents. When evaluating the lower 3rd molar angulation to the lower anterior PAR score it was found that the only statistical signi ficance was seen at DC-F time point. Spearman Correlation of Coefficients found a positive correlation of approximately 0.15544 and 0.18795 to the lower anterior crowding PAR component to the averag e and most severe (maximum) mandibular 3rd molar respectively. This is a mild co rrelation finding that as the mandibular 3rd molar became more mesially angulated the lower anterior PAR component increased, or showed more misalignment. Studies have suggested th at an impaction or mesialized lower 3rd molar effects lower incisor crowding.24, 25, 26 It is interesting that the only significant time point was DC-F 25

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(Table 3-3), the end of Class II treatment, wher e alignment should be at its best and where each subject should have a low an terior crowding PAR component score regardless of lower 3rd molar angulation. Statistical significance most likely does not have an effect on clinical significance at this time point. The upper 3rd molar angulation was not found to be statistically significant to a correlation with the upper anterior crowding PA R component in any of the six time points analyzed. Not many previous studies have warranted a reason to look at the upper 3rd molars angulation effect on the upper anterior PAR component, although Bergstroms21 study did not find a correlation. Since DC-F was the only time point that show ed statistical signifi cance to a correlation between 3rd molar angulation and the anterior crowding PAR com ponent, this time point was further analyzed according to treatment group (Table 3-4). The average of the two mandibular 3rd molars no longer showed a significant correl ation to lower anterior PAR component, although when looking at the maximum, or most severely angulated, 3rd molar there was a mild-moderate positive correlation with lower anterior PAR com ponent. This suggests that a more severely angulated lower 3rd molar may play more of an influence than two less severely angulated lower 3rd molars. It was interesting to note the only the bionator group was stat istically significant and that the maxillary 3rd molars showed a more moderate ne gative correlation than the mandibular molars mild positive correlation. The fact that the bionator group showed a moderate correlation between the more uprighted maxillary 3rd molar with the maxillary anterior crowding PAR component cannot be explained by a different mean maxillary 3rd molar angulation (Figure 3-4), since the mean maxillary 3rd molar angulation for the bionator, headgear/biteplane, and control group were within 4 degrees of one another at DC-F. It could be that the bionator group had a wider range of maxillary 3rd molar angulations and that thes e outliers played a role in the 26

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maxillary anterior crowding PAR component. A nother theory is that both the lower and upper anterior crowding PAR component may have correlated to one another if overbite and overjet were not finished ideally or had relapsed in re tention. It is impossibl e to know whether it was the Phase-I bionator treatment s effect on the maxillary 3rd molar is what impacted the maxillary anterior crowding PAR compone nt, although it seems unlikely si nce Phase I treatment ended approximately 3.5 years prior to DC-F. One problem with this study is that although we were trying to decipher an effect Phase I treatment may have had on angulation, all measurem ents were analyzed post-Phase I. Another problem is that not all of the same subjects were measured during each time point, which diminishes the longitudinal nature of the study. Patients were randomized into 6 month retention or no retention groups after Phase I, followed by a ll subjects without reten tion for an additional 6 months. After Phase II, most patients were given permanent lower lingual retainers, although some were given removable retainers. The type of retention and compliance needed to maintain the alignment may have played a role on the ante rior crowding PAR compone nt. As far as using panoramic films to measure angulations, studies ha ve shown that a mean angulation difference of two panoramic films taken of the same dentition can easily result in a 5 degree difference, which may not be clinically significant fo r most dental diagnoses but does play a large influence in this particular study. 45, 46, 47 27

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CHAPTER 5 CONCLUSION We attempted to determine whether there were significant differences in the angulation of the developing 3rd molar and/or their relationship to th e anterior crowding PAR component when treated with either a Phase I bionator, headgear/biteplane, or placed in a control group. No angulation differences were found amongst the thr ee Phase I groups. At the completion of Phase II treatment the subjects in the bionator group showed a mild-moderate positive correlation between mandibular 3rd molar angulation and mandibular anterior PAR component, whereas the maxillary 3rd molar angulation and maxillary anterior PAR component revealed a mild-moderate negative correlation. Clinical si gnificance is most likely lacking since the anterior teeth should be well aligned at the conc lusion of Phase II treatment. 28

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LIST OF REFERENCES 1. Garn SM, Lewis AB, Bonne B. Third molar formation and its developmental course. Angle Orthod 1981; 51: 41-47. 2. Gravely JF. A radiographicsurvey of the third molar development. Br Dent J 1965; 119: 397401. 3. Rantanen AV. The age of eruption of the third molar teeth. A clinical study based on Finish university students. Ac ta Odontol Scand 1967; 25: 1-86. 4. Haavikko K.The formation and the alveolar and clinical eruption of the permanent teeth. An orthopantomographic study. Suom Hammaslaak Toim 1970; 66:103-70. 5. Nolla C. Development of the Permanent Teeth. J Dental Child 1960; 27: 254-66. 6. Enlow DH. Essentials of facial growth/ D onald H. Enlow, Mark G Hans. Philadelphia: Saunders, c1996 xv, 303. 7. Bjork A, Jensen E. Palling M. Mandibular growth and 3rd molar impaction. Acta Odontol Scand 1956; 14: 231-7. 8. Richardson M. Changes in lower third mo lar position in the young adult. Am J Orthod Dentofacial Orthop 1992; 102: 320-7. 9. Ricketts, R. A principle of racial growth of the mandible. Angle Orthodont 1972; 42: 368386. 10. Ricketts RM, Turley P, Chac onas S, Schulhof RJ. Third molar enucleation: diagnosis and technique. J Calif Dent Assoc 1976; 4: 52-7. 11. Schulhof RJ. Third molars and orthodontic diagnosis. J Clin Orthod. 1976; 4: 272-81. 12. Dachi SF, Howell FV. A survey of 3, 874 routine full-month radiographs. II. A study of impacted teeth. Oral Surg Oral Med Oral Pa thol 1961; 14: 1165-9. 13. Artun J, Behbehani F, Thalib L. Predicti on of Maxillary Third Molar Impaction in adolescent Orthodontic Patient s. Angle Orthodontis t 2005; 75: No 6. 14. Ganss C, Hochban W, Kielbassa AM, Umst adt HE. Prognosis of third molar eruption. Oral Surg Oral Me d Oral Pathol 1993; 76: 688-93. 15. Richardson ME. The early developmental position of the lower third molar relative to certain jaw dimensions. Angle Orthod 1970; 3: 226-30. 29

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16. Faubion BH. Effect of extraction of premol ars on eruption of mandibular third molars JADA 1968; 76: 316-320. 17. Artun J, Thalib L, Little RM. Third molar angulat ion during and after treatm ent of adolescent orthodontic patients. Eur J Orthod 2005; 27: 590-6. 18. Kim TW, Artun J, Behbehani F, Artese F. Prev alence of third molar impaction in orthodontic patients treated nonextrac tion and with extraction of 4 premolars. Am J Orthod Dentofacial Orthop 2003;123: 138-45. 19. Staggers JA, Germane N, Fortson WM. A comp arison of the effects of first premolar extractions on third molar angulation. Angle Orthod 1992; 62: 135-8. 20. Olive RJ, Basford KE. Transverse dento-skelet al relationships and third molar impaction. Angle Orthod 1981; 51: 41-7. 21. Richardson ME. Development of the lo wer third molar from 10 to 15 years. Angle Orthod 1973; 43: 191-3. 22. Haug RH, Perrott DH, Gonzalez ML, Talwar RM. The American Association of Oral and Maxillofacial Surgeons Age-Related Thir d Molar Study. J Oral Maxillofac Surg 2005; 63: 1106-14. 23. Lindauer SJ, Laskin DM, Tfeki E, Taylor RS, Cushing BJ, Best AM. Orthodontists' and surgeons' opinions on the ro le of third molars as a cause of dental crowding. Am J Orthod Dentofacial Orthop. 2007; 132: 43-8. 24. Shanley LS. The influence of mandibular thir d molars on mandibular anterior teeth, MS thesis, Washington University, St. Louis, Mo., 1960. 25. Sidlauskas A, Trakiniene G. Effect of the lower third molars on the lower dental arch crowding. Stomatologija 2006; 8: 80-4. 26. Little RM. Stability and relaps e of mandibular anterior alignm ent: University of Washington studies. Semi n Orthod 1999: 5: 191-204. 27. Bergstrom K, Jensen R. Responsibility of the third molar for secondary crowding. Sven Tandlak Tidskr 1961; 54: 111-124. 28. Vego L.A longitudintal study of mandibular arch perimeter. Angle Orthod 1962; 32: 187192. 29. Richmond S et al. The development of the PAR Index (Peer Assessment Rating): reliability and validity. European Journal of Orthodontics 1992; 14: 125-139. 30

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30. Keeling SC, Wheeler TT, King GJ, Garv an CW, Cohen DA, Cabassa S, McGorray SP. Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear. Am J Or thod Dentofacial Orthop 1998; 113: 40-50. 31. OBriend K, Wright J, Conboy F, Sanjie Y, Mandall N, Chadwick S, Connolly I, Cook P, Birnie D. Hammond M, Harra dine N, Lewis D, Mc Dade C, Mitchell L, Murray A, ONeill J, Read M, Robinson S, Roberts-Harry D, Sandler J, Shaw I. Effectiveness of early orthodontic treatment with the Twin-block appliance: a multicenter, randomized, c ontrolled trial. Part 1: Dental and skeletal effects. Am J Orthod Dentof acial Orthop 2003;124: 234-43. 32. Wheeler TT, McGorray SP, Dolce C, Taylor MG King GJ. Effectiveness of early treatment of Class II malocclusion. Am J Orthod Dentofacial Orthop 2002; 121: 9-17. 33. Trkkahraman H, Sayin MO. Effects of act ivator and activator headgear treatment: comparison with untreated Cla ss II subjects. Eur J Orthod 2006; 28: 27-34. 34. Tulloch JF, Proffit WR, Phillips C. Outcomes in a 2-phase randomized clinical trial of early Class II treatment. American Journal of Orthodontics and Dentof acial Orthopedics 2004; June: 657-667. 35. Pavlow SS, McGorray SP, Taylor MG, Dolce C, King GJ, Wheeler TT. Effect of early treatment on stability of occlusion in patients with Class II malocclusion. Am J Orthod Dentofacial Orthop 2008; 133: 235-44. 36. Almeida-Pedrin RR, Almeida MR, Almeida RR, Pi nzan A, Ferreira FP. Treatment effects of headgear biteplane and bionator appliances. Am J Orthod Dentofacial Orthop 2007;132:1918. 37. Maran G. Effects of activator and high-pu ll headgear combination therapy: skeletal, dentoalveolar, and soft tissue pr ofile changes. Eur J Orthod 2007; 29:140-8. 38. Jena AK, Duggal R, Parkash H. Skeletal an d dentoalveolar effects of Twin-block and bionator appliances in the treatment of Class II malocclusion: a comparative study. Am J Orthod Dentofaci al Orthop 2006;130: 594-602. 39. Ganss C, Hochban W, Kielbassa AM, Umstadt HE. Prognosis of third molar eruption. Oral Surg Oral Med Oral Pathol 1993; 76: 688-93. 40. Sekin O, Surucu R. Treatment of Class II, di vision 1, cases with a maxillary traction splint. Quintessence Int 1990; 21: 209-15. 41. Uner O, Eroglu EY. Effects of a modified maxillary orthopaed ic splint: a cephalometric evaluation. Eur J Orthod 1996; 18:269-86. 31

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42. Fotis V, Melsen B, Williams S, Droschl H. Vertic al control as an important ingredient in the treatment of severe sagittal discrepancies. Am J Orthod 1984; 86:224-32. 43. Richardson ME. The etiology and predicti on of mandibular third molar impaction. Angle Orthod 1977; 47:165-72. 44. Artun J, Thalib L, Little RM. Third molar angulation during and after trea tment of adolescent orthodontic patients. Eur J Orthod 2005; 27:590-6. 45. Stramotas S, Geenty JP, Darendeliler MA, Byloff F, Berger J, Petocz P. The reliability of crown-root ratio, linear and angular measurements on panoramic radiographs. Clin Orthod Res 2000; 3: 182-91. 46. Mckee IW, Glover KE, Williamson PC, Lam EW, He o G, Major PW. The effect of vertical and horizontal head positioning in panoram ic radiography on mesiodistal tooth angulations. Angle Orthod 2001; 71: 442-51. 47. Mckee IW, Williamson PC, Lam EW, Heo G, Glover KE, Major PW. The accuracy of 4 panoramic units in the projection of mesiodistal tooth angulations. Am J Ortho Dentofacial Orthop 2002; 121: 166-75. 32

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BIOGRAPHICAL SKETCH Noelle Williams grew up in Northport, NY. Her educational accomplishments include receiving her B.S. from Boston Co llege in the field of biology in 2001. She went on to receive here D.M.D. from Harvard School of Dental Medicine. In May of 2008, Noelle will be completing her Master of Science and orthodontic certificate from the Univ ersity of Florida. 33