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Orthodontic Tooth Movement (OTM) with Clear Aligners

Permanent Link: http://ufdc.ufl.edu/UFE0041743/00001

Material Information

Title: Orthodontic Tooth Movement (OTM) with Clear Aligners
Physical Description: 1 online resource (33 p.)
Language: english
Creator: Drake, Carl
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: aligners, carl, dental, dentist, drake, florida, invisalign, movement, orthodontic, orthodontics, orthodontist, tooth
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: Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science ORTHODONTIC TOOTH MOVEMENT (OTM) WITH CLEAR ALIGNERS By Carl T. Drake May 2010 Chair: Timothy Wheeler Major: Dental Sciences - Orthodontics The following observations regarding tooth movement with Invisalign aligners resulted from a randomized and controlled clinical trial performed at the University of Florida (UF) in 2005: 1) more orthodontic tooth movement (OTM) occurred during the first week versus the second week of aligner wear for each two-week prescription cycle, 2) the full prescription of the aligners were not expressed, and 3) OTM was highly variable among individuals. These observations have clinical implications and require further research. The primary aim of this study was to determine whether these observations were due to material fatigue of the aligners in the oral environment. The secondary aim of this study was to describe and quantify the type and amount of OTM produced by clear aligners. A prospective single center clinical trial was completed, comparing 15 subjects treated over a course of eight weeks with a control group of 37 subjects from the UF study with similar population demographics and nearly identical study design. An upper central incisor was programmed to move two mm over eight weeks, or 0.5 mm every two weeks, using Invisalignregistered trademark aligners. The treatment subjects changed to a fresh aligner with the same prescription after one week, and the control subjects wore each aligner for the prescribed two weeks. Weekly polyvinyl siloxane (PVS) impressions were taken and digital models were fabricated to measure OTM. In addition, initial and final cone beam computed tomography (CBCT) images were obtained from the treatment subjects only, to describe and measure OTM. No significant difference was found in the amount of OTM between those who wore the same aligner for two weeks vs. those who changed to a fresh aligner after one week. Therefore, the reduction in the amount of OTM seen during the second week of aligner wear was unlikely to be due to material fatigue. There was, however, a significant difference in OTM during the first week vs. the second week of any given two-week cycle, for both groups. When OTM was measured from the centroid of the clinical crown, the two mm prescription of the aligners was not fully expressed in any of the 15 treated subjects. High variability was observed. In addition, CBCT data indicated that: 1) the target teeth experienced uncontrolled tipping, with the median center of rotation located 41% of the root length apical to the alveolar crest, 2) although only one central incisor was programmed to move, the contralateral central incisor felt a reactive force and moved in the opposite direction of the target tooth, 3) seven of the 15 subjects experienced a net anteroposterior (A-P) change of less than 1.9 mm between the midpoint of the incisal edge of the target tooth and the contralateral central incisor, and 4) the results of an exploratory data analysis attempting to correlate biologic variables with OTM revealed some trends, but additional research is required before making conclusions.
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.
Statement of Responsibility: by Carl Drake.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Wheeler, Timothy T.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041743:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041743/00001

Material Information

Title: Orthodontic Tooth Movement (OTM) with Clear Aligners
Physical Description: 1 online resource (33 p.)
Language: english
Creator: Drake, Carl
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: aligners, carl, dental, dentist, drake, florida, invisalign, movement, orthodontic, orthodontics, orthodontist, tooth
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: Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science ORTHODONTIC TOOTH MOVEMENT (OTM) WITH CLEAR ALIGNERS By Carl T. Drake May 2010 Chair: Timothy Wheeler Major: Dental Sciences - Orthodontics The following observations regarding tooth movement with Invisalign aligners resulted from a randomized and controlled clinical trial performed at the University of Florida (UF) in 2005: 1) more orthodontic tooth movement (OTM) occurred during the first week versus the second week of aligner wear for each two-week prescription cycle, 2) the full prescription of the aligners were not expressed, and 3) OTM was highly variable among individuals. These observations have clinical implications and require further research. The primary aim of this study was to determine whether these observations were due to material fatigue of the aligners in the oral environment. The secondary aim of this study was to describe and quantify the type and amount of OTM produced by clear aligners. A prospective single center clinical trial was completed, comparing 15 subjects treated over a course of eight weeks with a control group of 37 subjects from the UF study with similar population demographics and nearly identical study design. An upper central incisor was programmed to move two mm over eight weeks, or 0.5 mm every two weeks, using Invisalignregistered trademark aligners. The treatment subjects changed to a fresh aligner with the same prescription after one week, and the control subjects wore each aligner for the prescribed two weeks. Weekly polyvinyl siloxane (PVS) impressions were taken and digital models were fabricated to measure OTM. In addition, initial and final cone beam computed tomography (CBCT) images were obtained from the treatment subjects only, to describe and measure OTM. No significant difference was found in the amount of OTM between those who wore the same aligner for two weeks vs. those who changed to a fresh aligner after one week. Therefore, the reduction in the amount of OTM seen during the second week of aligner wear was unlikely to be due to material fatigue. There was, however, a significant difference in OTM during the first week vs. the second week of any given two-week cycle, for both groups. When OTM was measured from the centroid of the clinical crown, the two mm prescription of the aligners was not fully expressed in any of the 15 treated subjects. High variability was observed. In addition, CBCT data indicated that: 1) the target teeth experienced uncontrolled tipping, with the median center of rotation located 41% of the root length apical to the alveolar crest, 2) although only one central incisor was programmed to move, the contralateral central incisor felt a reactive force and moved in the opposite direction of the target tooth, 3) seven of the 15 subjects experienced a net anteroposterior (A-P) change of less than 1.9 mm between the midpoint of the incisal edge of the target tooth and the contralateral central incisor, and 4) the results of an exploratory data analysis attempting to correlate biologic variables with OTM revealed some trends, but additional research is required before making conclusions.
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.
Statement of Responsibility: by Carl Drake.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Wheeler, Timothy T.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-04-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041743:00001


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1 ORTHODONTIC TOOTH MOVEMENT (OTM) WITH CLEAR ALIGNERS By CARL T. DRAKE A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010

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2 2010 Carl T. Drake

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3 To my wife and children for bringing me peace and happiness

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4 ACKNOWLEDGMENTS I thank God and my family for providing and nurturing my potential. I thank my wife, Kristen, as well as several other unnamed family and friends for their tireless and unwavering support. I thank my research mentor, Dr. Wheeler, for his guidance and direction. I thank all of my teachers past and present, who have contributed to my education. I th ank my research committee, as well as Marie Taylor, Dr. Shin Jae Lee Ivette Coro Dr. Nair, Dr. Ju Han (Donna) Chang and Dr. Patrick Holmes for their hard work and contribution to this project Last but not least, I acknowledge financial and/or logistical support from the University of Florida Department of Orthodontics, the University of Florida Graduate Student Council, the Amer ican Association of Orthodontists the Southern Association of Or thodontist s, the Flo rida Association of Orthodontists and Align Technology.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 6 LIST OF FIGURES .......................................................................................................... 7 ABSTRACT ..................................................................................................................... 8 C HAPTER 1 INTRODUCTION .................................................................................................... 10 2 METHODS .............................................................................................................. 12 Study Design .......................................................................................................... 12 Enrollment ............................................................................................................... 13 Screening 1 (Initial Screening) ......................................................................... 13 Screening 2 (Second Screening) ...................................................................... 13 Study Visits ............................................................................................................. 14 Week 0 ............................................................................................................. 14 Weeks 1, 2, 3, 4, 5, 6 and 7 .............................................................................. 14 Week 8 (Study Termination) ............................................................................. 14 Collection of Data ................................................................................................... 14 Calibration ............................................................................................................... 16 Statistical Management of Data .............................................................................. 17 3 RESULTS ............................................................................................................... 22 4 DISCUSSION ......................................................................................................... 27 5 CONCLUSION .......................................................................................................... 31 REFERENCES .............................................................................................................. 32 BIOGRAPHICAL SKETCH ............................................................................................ 33

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6 LIST OF TABLES Table page 2 1 Comparison of demographics of treatment and control groups. ......................... 18 2 2 Inclusion and Exclusion Criteria. ......................................................................... 18 2 3 Superimposed CBCT measurements ................................................................ 19 3 1 Weekly statistics from treatment and control groups, respectively. .................... 23 3 2 Mixed modeling comparing mean OTM per week from baseline to Week 8 for treatment vs. control group. ................................................................................ 24 3 3 Mixed modeling comparing the mean magnitude of OTM per week expressed during each twoweek prescription cycle. ........................................................... 2 4 3 4 Mixed modeling comparing OTM during the first week vs. second week for the treatment and control groups, both separately and combined. ..................... 24 3 5 CBCT measurements from treatment group. ...................................................... 25 3 6 Pearson Correlation Coefficient of Week 8 OTM vs. Biologic Variables. ............ 25 3 7 Comparison of Model and CBCT mean A P OTM. ............................................. 25

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7 LIST OF FIGURES Figure page 2 1 Superimposed digital models. ............................................................................. 20 2 2 Superimposed CBCT .......................................................................................... 21 3 1 Mean weekly OTM with Std. Error. ..................................................................... 26

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8 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science ORTHODONTIC TOOTH MOVEMENT (OTM) WITH CLEAR ALIGNERS By Carl T. Drake May 2010 Chair: Timothy Wheeler Major: Dental Sciences Orthodontics The following observations regarding tooth movement with Invisalign aligners resulted from a randomized and controlled clinical trial performed at the University of Florida (UF) in 2005: 1) m ore orthodontic tooth movement (OTM) occurred during the first week versus the second week of aligner wear for each twoweek prescription cycle, 2) t he full prescription of the aligners were not expressed, and 3) OTM was highly variable among individuals These observations have clinical implications and require further research. The primary aim of this study was to determine whether these observations w ere due to material fatigue of the aligners in the oral environment The secondary aim of this study was to describe and quantify the type and amount of OTM produced by clear align ers A prospective single center clinical trial was completed, comparing 15 subjects treated over a course of eight weeks with a control group of 37 subjects from the UF study with similar population demographics and nearly identical study design. An uppe r central incisor was programmed to move two mm over eight w eeks, or 0.5 mm every two week s, using Invisalign aligners The treatment subjects changed to a fresh

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9 aligner with the same prescription after one week and the control subjects wore each aligner for the prescribed two weeks Weekly polyvinyl siloxane ( PVS) impressions were taken and digital models were fabricated to measure OTM. In addition, initial and final cone beam computed tomography (CBCT) images w ere obtained from the treatment subjects only, to describe and measure OTM. No significant difference was found in the amount of OTM between those who wore the same aligner for two weeks vs. those who changed to a fresh aligner after one week. Therefore, the reduction in the amount of OTM seen during the second week of aligner wear was unlikely to be due to material fatigue. There was, however, a significant difference in OTM during the first week vs. the second week of any given two week cycle for both groups When OTM was measured from the centroid of the clinical crown, the two mm prescription of the aligners was not fully expressed in any of the 15 treated subjects. High variability was observed. In addition, CBCT data indicated that : 1) t he target teeth experienced uncontrolled tipping, with the median center of rotation located 4 1 % of the root length apical to the alveolar crest, 2) a lthough only one central incisor was programmed to move, the contralateral central incisor felt a reactive force and moved in the opposite direction of t he target tooth, 3) s even of the 15 subjects experienced a net antero posterior ( A P ) change of less than 1.9 mm between the midpoint of the incisal edge of the target tooth and the contralateral central incisor, and 4) t he results of an exploratory data analysis attempting to correlate biologic variables with OTM revealed some trends, but additional research is required before making conclusions.

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10 CHAPTER 1 INTRODUCTION Research involving the Invisalign system is lacking. Most of the available literature consists of case reports, editorials, or articles written by authors with bias. There have been no evidence based attempts to describe the type of OTM resulting from treatment with clear aligners Conventional thinking suggests that the movement is most ly uncontrolled tipping, with the center of rota tion located between the center of resistance and the apex of the tooth. The center of resistance of a singlerooted tooth has been reported to be on the long axis of the tooth between one third and one half of the root length apical to the alveolar crest.1 Duong et al.2 compared the loaddeflection rates (LDR) of 0.017x0.017 stainless steel ( SS) and Nickel Ti tanium (NiTi) wires vs. 0.030 mm polyurethane material over a 0 10% range of strain in vitro. Th e LDR of the polyurethane was greater than the NiTi wire but less than the stainless steel wire. Therefore, with a given amount of deflection, the aligner should deliver a lower initial level of force than the ss wire. Additional studies relating force l evels to Invisalign would be beneficial, including clinical studies addressing deformation of aligners in the oral environment over time. A randomized and controlled clinical trial was performed at UF in 2005 ( Wheeler, T T unpublished data), evaluating the safety, tolerability, and efficacy of recombinant human relaxin during OTM using clear aligners. While t his study found no significant difference between the treatment and control groups, concluding that relaxin levels were not related to the rate of OT M several interesting observations were noted including: 1) m ore OTM occu rred during the first week v s. the second week of aligner wear for each two week prescription cycle, 2) t he full prescription of the aligners were not expressed

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11 and 3) OTM was highly variable amo ng individuals These observations have clinical implications and require further research. Currently patients are instructed to wear each aligner for two weeks, although there is little evidence to support this. Further, the role of aligner degradation on OTM is unknown, but it likely results in a decrease in the magnitude of forces transferred to teeth over time If material fatigue inhibits aligners from fully expressing their potential (or prescription), it seems reasonable to hypothesize that replacing each aligner after one week with a fresh aligner with an identical prescription may increase the reliability of OTM P atients and clinicians could benefit from a better understanding of the impact of appliance degradation and fatigue on OTM

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12 CHAPTER 2 METHODS Study Design This study was a pr ospective single center clinical trial involving subjects with minor incisor malalignment, who were otherwise healthy and intended to undergo comprehensive orthodontic treatment The design for this study was pat terned off of a previous study consisting of 37 subjects designed by the same pri ncipal investigator at UF in 2005, which served as the retrospective control group. Sixteen subjects were enrolled and one dropped out during the screening p rocess prior to initiating treatment, resulting in a sa mple of 15 subjects ( 6 males and 9 females ) between the ages of 18 and 40 years ( mean age 25.13) They were in good health and had acceptable malocclusions as defined by the inclusion and exclusion criteria (Table 21 ). Demographic information for the treatment group is compared with the control group in Table 22. T he right or left maxillary central incisor was selected as the target tooth based on th is tooth not being blocked out by the adjacent teeth. In the event that either tooth would qualify, one was chosen at random. During this study, subjects were provided with four maxillary aligners, each programmed to move the target tooth 0.5 mm every two weeks. Only bodily movement of the single t arget tooth in the A P dimension was programmed (no intrusion, extrusion or rotation). In addition, for the treatment group, four duplicate aligners were fabricated for the replacement of the delivered aligner at the beginning of each oddnumbered week. T herefore, new aligners were dispensed each week (Weeks 0 7). This is in contrast to the control group, where subjects wore only four aligners, each for a period

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13 of two weeks. The final time point for data collection, marking the end of the study, was at W eek 8 All study subjects were instructed to wear the aligners fulltime. However, t hey were allowed to remove the appliance when eating, drinking, or brushing their teeth. Compliance was monitored using a daily diary that was completed by the study subj ects. A fter the conclusion of the study, subjects were treated at the UF graduate orthodontic clinic with Invisalign Enrollment To determine subject eligibility, two screening visits were required. Screening 1 (Initial Screening) The purpose of th is appointment was t o identify potential subjects with malocclusions needing minor incisor alignment and to eliminate those with medical conditions or intraoral problems that were exclusionary. Potential subjects were allowed to proceed with Screening 2. Screening 2 (Second Screening) The purpose of this appointment was to finalize the subjects eligibility and collect records T he following procedures were performed: 1) PVS i mpressions 2) i ntraoral and extraoral photographs and 3) CBCT imaging. For wo men, a negative urine pregnancy test immediately prior to radiographic procedures was required. After the investigator reviewed all information and confirm ed eligibility, the subj ect was enrolled into the study and the target tooth was identified according to the above criteria.

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14 Study Visits Week 0 A t the first study visit (Week 0) the first aligner was deliver ed with instruct ions to wear full time except while eatin g, drinking and brushing. The acceptable visit window for Weeks 0 8 was one day, and all 15 treatment subjects successfully satisfied this requirement. Weeks 1, 2, 3, 4, 5, 6 and 7 A t these visits m axillary PVS impression s as well as frontal and occlusal photographs were taken, and the next aligner was delivered. Week 8 (Study Terminatio n) At the final study visit (Week 8) m axillary PVS impression s and final photographs were taken as well as CBCT imaging of the maxilla Collection of Data Weekly digital models were fabricated from PVS impressions M odels from Weeks 1 8 were then superimposed with the initial model from Screening 2, according to the best fit of the posterior teeth (Figure 2 1) using Align Technologys Tooth Measure software, version 2.3. The centroid of the clinical crown of the target tooth was established, and t he amount of A P and vertical OTM of the target tooth was then measured for each t imepoint relative to baseline The A P axis was determined by the direction of programmed OTM in ClinCheck Examiner 1 (an orthodontic resident) measured the models of the 15 treat ment subjects, and E xaminer 2 (a 3rd year dental student) measured the 37 control subjects. CBCT imag es were obtained during Screening 2 and Week 8. Using Anatomages InVivoDental software version 4.1, t he orientation of these images were adjusted b y

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15 Examiner 1 to standardize the A P axis with the corresponding digital models Initial and final images were superimposed, registered on the curvature of the palate and best fit of maxillary bony structures. Multiple measurements were obtained ( Table 23 and Figure 22 ) refers to the distance between l ines drawn through the midpoint of the incisal edges of the superimposed target tooth perpendicular to the A P axis (the plane of prescribed tooth movement). U1 (s ) is the l ength of the line connecting the midpoint of the incisal edges of the superimposed target tooth. refers to the length of a line connecting the change in apex of the superimposed t arget tooth. Rotation angle is the angle created by the intersection of lines drawn f rom the midpoint of the incisal edge to the apex of the target tooth. The apex of this angle is considered the center of rotation Tooth length refers to the distance from the midpoint of the incisal edge to the apex of the target tooth from the initial x ray. Crown length is the portion of the tooth length that is coronal to the bone. Bone to C rot. is the section of tooth length between the center of rotation and a line connecting the most coronal aspect of the faciolingual crestal bone. U1 (o) refers to the A P change in the midpoint of the superimposed incisal edge of the opposite central incisor the one that was no t the target tooth. From these measurements, additional ratios and measurements were calculated. A fractal analysis scor e3 was calculated from the CBCT for each treatment subject which was used to determine the quality of the bone. CBCT slices through comparable planes were obtained across all subjects Images were subjected to histogram equalization using a reference i mage and a region of interest ( ROI ) adjacent to the apex of the target tooth was selected for use on all images. Fractal analyses

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16 were carried out for each of the different ROIs using the power spectrum method employed by the TACT workbench. Thirty two bit complex floating point representations of the ROIs were cropped, and subject to 2D Fast Fourier transform (FFT), followed by plotting the log of the magnitude versus frequency component that was generated by the FFT. A regression line was fit to this plot, and the slope of this line was used to generate a fractal dimension (FD) for each of the ROIs. The higher the FD the higher the morphological complexity at the ultrastructural level of bone. Analyses of FD have been correlated with the strength of bone in previously reported studies. Calibration Examiners 1 and 2 were trained to use the ToothM easure software on the same day and t he following measurement protocol was agreed upon: 1) a llow the software to ignore teeth according to its "statistic al filtering" protocol, 2) always ignore teeth immediately adjacent to the target tooth as well as the target tooth itself and 3) i nstruct ToothM easure to superimpose the models according to the best fit of the remaining teeth. I nterexaminer reliability was determined after separately measuring six randomly selected subjects from the 2005 UF study with eight superimpositions per subject. Results were identical between Examiners 1 and 2, who later measured superimposed digital models for the treatment a nd control groups, respectively. For the CBCT data, E xaminer 1 re measured the following variables on a different day to determine reproducibility: U1 (s) rotation angle, tooth length, and crown length. T he intraclass classification coefficient (ICC) of Fliess 4,5 was determined, using R software ,6 to quantify the strength of relationship between the duplicate

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17 measurements ICC values ranged from 0.90 to 0.99, which demonstrate d excellent reliability Statistical Management of Data T he amount of A P OTM of the target tooth from baseline to Week 8 was assessed for the 15 treatment subjects that completed the study One subject dropped out after enrollment but prior to initiating OTM and thus had no data to analyze. Model d ata from the treatment sample was compared with data from the control group with a sample size of 37 The null hypothesis of no difference in OTM from baseline to Week 8 between control group and treatment group was tested, using a two sample t test with a level of significance set at 0.05. Mixed modeling analysis was used to test the difference between the first week of any given twoweek interval vs. the second week and differ ences with treatment group over the four two week cycles OTM was quantified using descriptive statistics from CBCT data. Correlations between tooth movement and possible covariates were analyzed u sing Pearson correlation coefficients

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18 Table 2 1. Com parison of demographics of treatment and control groups. Treatment Control n Mean SD Range n Mean SD Range p value Age (yr) 15 25.5 4.8 20.5 34.9 37 26.7 5.1 18.6 40.5 0.50* Sex Male (%) 6(30) 11(30) 0.52** Fema le (%) 9(60) 26(70) Race White (%) 8(53) 28(76) 0.08*** Black (%) 2(12) 5(14) Asian (%) 3(20) 1(3) Hispanic (%) 1(7) 3(8) Pac Island (%) 1(7) 0 Wilcoxon rank sum test ** Fisher exact test *** White vs. non white Fisher exact test Table 2 2. Inclusion and Exclusion Criteria. 1 Males or females between the ages of 18 and 40 2 Must have a dult dentition with all upper front teeth present. 3 Must have a t least o ne upper maxillary central incisor that has sufficient space between it and adjacent teeth to allow AP movement (crown tipping only) of 2 mm. 4 Must have n ormal pulp vitality, gingival attachment, papillary bleeding score index (PBS index), and pocket dep th. 5 Must be in g ood health as determined by medical history. 6 Must be w illing and abl e to participate. 7 Must understand and sign a written informed consent form 8 Must not have active caries. 9 Must not be a chronic user of NSAIDS or steroid medi cation. 10 Must not have smoked in the last six months. 11 Women must not be pregnant.

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19 Table 23 Superimposed CBCT measure ments Blue is initial and red is final.

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20 Figure 21 Superimposed digital models.

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21 A B Figure 22 Superimposed CBCT (A) and clos e up of target tooth with measurements (B). Gray is initial and blue is final.

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22 CHAPTER 3 RESULTS Results from model measurements are summarized in Table 31, and a comparison of mean values for the treatment and control groups is illustrated in Figure 3 1 No overall difference in OTM was detected between the groups, with mean total OTM of 1.11 mm ( standard deviation (SD) 0.30) and 1.07 mm ( SD 0.33) for the treatment and control groups, respectively (p=0.72). Also, no difference was detected in weekly OTM of the treatment vs. control groups overall (Table 32 ) (p =0.812) or between any twoweek prescription cycle (Table 33 ) ( p s=0.176 and 0.297) However, a s shown in Table 34 4.4 times more OTM occurred during the first week than the second week of a lign er wear ( p<0.001) after combining the groups Measurements from superimposed CBCT images confirmed that the target too th experienced uncontrolled tipping (Table 35 ) The center of rotation, on average, was located a distance of 41 % of the root length apical to the faciolingual crestal bone The incisal edge of the target tooth moved more than the centroid of the clinical crown in all cases, with a mean of 1.56 mm for U1 ( x ) compared with 1.1 mm measured from the centroid. U1 (s) had a mean of 1.63 mm compared with the mean Euclidian mean value of 1.11 mm measured from the centroid of the clinical crown on the models. The apex of the target tooth moved in the opp osite direction with a mean of 0.73 mm. T he contralateral central incisor experienced a loss of anchorage measured from the incisal edge, with a mean OTM of 0.28 mm. Mean FD determined from the CBCT of each treatment subject was 1.71 SD 0.20. Pearso n Correlation Coefficient values between OTM and CBCT measurements are listed in Table 3 6

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23 Table 31. Weekly statistics from treatment and control groups, respectively. Tx Group n Median Mean Std Error SD Min Max Wk 0 15 0 0 0 0 0 0 Wk 1 15 0.240 0.239 0.0174 0.0674 0.100 0.370 Wk 2 15 0.310 0.297 0.0228 0.0883 0.130 0.450 Wk 3 15 0.430 0.458 0.0295 0.114 0.330 0.670 Wk 4 15 0.450 0.497 0.0418 0.162 0.230 0.770 Wk 5 15 0.620 0.701 0.0536 0.207 0.430 1.060 Wk 6 15 0.770 0.793 0.0534 0.207 0.530 1.130 Wk 7 15 1.040 1.033 0.0648 0.251 0.530 1.420 Wk 8 15 1.160 1.108 0.0768 0.297 0.350 1.460 Control n Median Mean Std Error SD Min Max Wk 0 37 0 0 0 0 0 0 Wk 1 36 0.210 0.206 0.0122 0.0735 0.0300 0.320 Wk 2 36 0.240 0.234 0.0122 0.0735 0.0500 0 .390 Wk 3 37 0.440 0.445 0.0228 0.138 0.100 0.680 Wk 4 36 0.530 0.495 0.0255 0.153 0.0700 0.790 Wk 5 36 0.775 0.726 0.0380 0.228 0.120 1.100 Wk 6 36 0.830 0.737 0.0416 0.250 0.0700 1.100 Wk 7 37 1.080 1.009 0.0519 0.316 0.100 1.410 Wk 8 37 1.180 1.07 2 0.0536 0.326 0.220 1.550

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24 Table 32 Mixed modeling comparing mean OTM per week from baseline to Week 8 for treatment vs. control group. Group Mean SD P value (t test) Treatment 0.14 0.11 0.812 Control 0.14 0.15 Table 33 Mixed modeling comparing the mean magnitude of OTM per week expressed during each two week prescription cycle. Group Interval Mean/Wk SD P value Treatment Week 1 2 0.15 0.11 0.176 Week 3 4 0.10 0.09 Week 5 6 0.15 0.11 Week 7 8 0.16 0.13 Control Week 1 2 0.12 0.11 0.297 Week 3 4 0.13 0.13 Week 5 6 0.13 0.17 Week 7 8 0.16 0.19 Table 34 Mixed modeling comparing OTM during the first week vs. second w eek for the treatment and control groups, both separately and combined. Group Interval Mean SD P value Treatment 1 st week 0.21 0.09 < 0.0001 2 nd week 0.07 0.08 Control 1 st week 0.23 0.13 < 0.0001 2 nd week 0.04 0.11 Total 1 st week 0.22 0.12 < 0.0001 2 nd week 0.05 0.10

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25 Table 35 CBCT measurements from treatment group Variable n Mean SD Max Min U1 (x) 15 1.56 0.38 2.02 0.80 U1 (s) 15 1.63 0.40 2.09 0.80 Apex 15 0.73 0.26 1.32 0.39 Tooth Length 15 24.87 2.02 30.32 21.67 Crown Length 15 12.27 0.74 13.27 10.84 Bone to C rot. 15 5.14 1.25 7.7 2.9 U1 (o) 15 0.28 0.16 0.52 0 U1 (t) 15 1.85 0.36 2.4 1.08 Table 36 Pearson Correlation Coefficient of Week 8 OTM vs. Biologic Variables Variable n R P value Age 15 0.25 0.37 Crown/Root ratio 15 0.01 0.97 Fractal Dimension 15 0.38 0.10 Table 3 7. Comparison of Model and CBCT mean A P OTM. n Mean Max Min SD Model (x) 15 1.09 1.44 0.35 0.28 15 1.56 2.02 0.8 0.38 15 1.85 2.4 1.08 0.36 Ratio (x/x) 15 0.7 0.92 0.44 0.11 Ratio (x/t) 15 0.59 0.73 0.32 0.1

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26 Figure 31 Mean weekly OTM with S td Error.

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27 CHAPTER 4 DISCUSS ION This study reinforced previous findings t hat the vast majority of OTM during any 2 week aligner prescription cycl e occurs during the first week of the cycle The target tooth in this eight week study did not undergo the classic cycle of tooth movement described by Krishnan et al.7 This my be du e to the twoweek activation cycle or the inability of the removable polyurethane aligners to produce a continuous force, D ue to incomplete expression during the previous seven weeks, t he amount of target tooth activation after delivery of the eight h al igner was in excess of 1 mm according to model data. This likely resulted in the tooth feeling a greater force during the last week than after delivery of the first and second aligners when the amount of activation was 0.5 mm or less H owever significa ntly less OTM occurred at Week 8 than Week 1, and there was no significant difference in the amount of OTM observed at Week 8 and Week 2. This suggests that the discrepancy in the amount of OTM achieved d uring the first and second week of each prescription cycle cannot be explained by force magnitude. This is further supported by our finding that the use of fresh aligners did not increase the amount of OTM. Although bodily protraction of the target tooth was programmed, uncontrolled tipping result ed w hich has clinical implications. More specifically the final result will be different from Clincheck and aligner retention and tracking may be negatively affected. W hen clinicians attempt to move maxillary incisors in the A P dimension with aligners a llowing for vertical changes of the incisal edges may make treatment more predictable, which could reduce the need for midcourse modifications and make treatment more efficient T he amount of relative intrusion and extrusion to program can

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28 be determined by estimating the location of the center of rotation of the teeth ( determined to be approximately 41% of the root length apical to the faciolingual crestal bone). A ccording to model data, the full prescription was not expressed in any of the 52 subjects. In fact, the mean OTM for both groups was only 1.1 mm, or 55% of the prescription. It is important to remember that the prescribed amount of OTM was twice the maximum rate per aligner currently prescribed by Invisalign It is possible that a greater per centage of the prescription might be achieved if the maximum two week activation was decreased to 0.25 mm instead of 0.5 mm. This is currently being stud ied The discrepancy between the amount of OTM prescribed and that achieved may be part ially explained by the method of measurement used in this study as well as the uncontrolled tipping that occurred. The largest amount of OTM recorded from baseline to Week 8 from model data was 1.44 mm, or 72% of the prescription. This same subject had 1.98 mm of OTM from baseline to Week 8 when measured from the incisal edge of the target tooth of superimposed CBCT images See T able 3 7 comparing model and C BC T mean OTM values. Given this information one would not expect 100% of the prescription at the centroid of the crown to be fulfilled since OTM at the incisal edge was already fully achieved. One must also consider anchorage loss of the contralateral central incisor when interpreting this data. The prescribed protraction of the target tooth relative to the co ntralateral central incisor at Week 8 was two mm for each subject and the difference between ) ) indicate s that a mean of 1.85 mm of this two

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29 mm distance was actually fulfilled, an average of 92.3% of the prescription. In addition, e ight of the 15 subjects showed a total OTM greater than 1.9mm, which indicates that OTM at the incisal edge of these subjects was nearly fully expressed. The m easurement method explains a portion of the discrepancy in model data between programmed and actual OTM However, t remendous variation was reported among subjects and several target teeth did not achieve their full prescription at the incisal edge. Some discrepancy among this subset may be explained by lack of compliance. However from a biologic perspective, it is likely that a subset of subjects did not have the capacity t o keep up with the prescribed rate of OTM. According to Krish n an et al.,8 several systemic factors can influence rates of OTM and some were specifically excluded from this study Others that we re not controlled, such as sex, age, bone quality, tooth len gth, and the location of the center of resistance (determined by root length, root width, and bone height)1 9 may have been a factor The result of the exploratory data analysis attempting to correlate sev eral of these biologic variables with OTM was statistically insignificant with low powers of explanation. S om e trends were noted, however, and f uture research with larger sample sizes will be necessary to explore these findings There was considerable v ariability of OTM in this study, which is a problem that practicing orthodontists often encounter. Improving the ability to identify patients who are unlikely to respond well to treatment would be beneficial for the profession and should be a focus of ong oing research Regarding OTM using clear align ers, methods of altering treatment to compens ate for patients who may not respond as well to OTM might be : 1) establishing realistic expectations, 2) spreading treatment over additional

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30 align ers, thus decreasi ng the programm ed rate of tooth movement, and 3) programming over correction into Clincheck We hope to further examine these issues in future studies.

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31 CHAPTER 5 CONCLUSION This single center clinical trial examined OTM using clear aligners. No significant difference was found in the amount of OTM between those who wore the same aligner for two weeks vs. those who changed to a fresh aligner after one week. Therefore, the reduction in the amount of OTM seen during the second week of aligner wear was lik ely not due to material fatigue. Other variables that could affect tooth movement such as age, gender, root location and bone quality were examined. H owever subject numbers were too low to make any conclusions.

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32 REFERENCES 1 Burstone CJ, Pryputniewic z RJ. Holographic determination of centers of rotation produced by orthodontic forces. Am J Orthod 1980;77:396409. 2 Duong T, Kuo E. Finishing wit h Invisalign. Prog Orthod 2006; 7(1):44 55. 3 Nair MK, Seyedain A, Webber R, Nari U, Piesco N, Agarwal S, Mooney M, Grondahl H. Fractal analysis of osseous healing using Tuned Aperature Computed Tomog raphy images. Eur Radiol 2001; 11:151015. 4 Fleiss JL. The design and analysis of clinical experiments. New York : Wiley; 1986: 8. 5 Fleiss JL, Chilton NW. The measurement of interexaminer agreement and periodontal disease. J Periodont Res 1983;18:6016. 6 The R Project for S tatistical C omputing. Internet site. Available at: http://www.R proj ect.org Accessed September 23, 2009. 7 Krishnan V, Zeev D. Cellular, molecular, and tissuelevel reactions to orthodontic force. Am J Orthod Dentofacial Orthop 2006; 129:469 e132. 8 Krishnan V, Davidovitch Z. The effect of drugs on orthodontic tooth movement Orthod Craniofacial Res 2006;9: 163 171. 9 Smith RJ, Burstone CJ. Mechanics of Tooth Movement Am J Orthod 198 4;85(4):294307.

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33 BIOGRAPHICAL SKETCH Carl T. Drake was born in Bloomington, IL and raised in El Paso, IL where he graduated from E l Paso High School in 1999. He received a Bachelor of Science in Business Administ ration with a concentration in entrepreneurship from the University of Illinois in 2003. He continued his education at Indiana University in Indianapolis and earned a Docto rate of Dental Surgery degree in 2007. He is expected to receive a Master of Science in Dental Sciences as well as a Certificate in Orthodontics from the University of Florida in the spring of 2010. Carl plans on living and working in BloomingtonNormal IL following graduation. He has been happily married to his wife, Kristen, since 2003 and they have two children, Benjamin an d Ella.