CBCT Evaluation of Adolescent Mandibular Morphology in Different Classifications of Facial Type

Transcription

1 UNLV Theses, Disseraions, Professional Papers, and Capsones December 2015 CBCT Evaluaion of Adolescen Mandibular Morphology in Differen Classificaions of Facial Type Annie Hsu Universiy of Nevada, Las Vegas, Follow his and addiional works a: hps://digialscholarship.unlv.edu/hesesdisseraions Par of he Denisry Commons Reposiory Ciaion Hsu, Annie, "CBCT Evaluaion of Adolescen Mandibular Morphology in Differen Classificaions of Facial Type" (2015). UNLV Theses, Disseraions, Professional Papers, and Capsones hps://digialscholarship.unlv.edu/hesesdisseraions/2539 This Thesis is brough o you for free and open access by Digial Scholarship@UNLV. I has been acceped for inclusion in UNLV Theses, Disseraions, Professional Papers, and Capsones by an auhorized adminisraor of Digial Scholarship@UNLV. For more informaion, please conac digialscholarship@unlv.edu.

2 CBCT EVALUATION OF ADOLESCENT MANDIBULAR MORPHOLOGY IN DIFFERENT CLASSIFICATIONS OF FACIAL TYPE By Annie Hsu Bachelor of Ars in Economics Universiy of California, Berkeley 1998 Docor of Denal Surgery Universiy of California, Los Angeles, School of Denisry 2009 A hesis submied in parial fulfillmen of he requiremens for he Maser of Science - Oral Biology School of Denal Medicine Division of Healh Sciences The Graduae College Universiy of Nevada, Las Vegas December 2015

3 Copyrigh by Annie Hsu, 2015 All Righs Reserved

4 Thesis Approval The Graduae College The Universiy of Nevada, Las Vegas Ocober 9, 2015 This hesis prepared by Annie Hsu eniled CBCT Evaluaion of Adolescen Mandibular Morphology in Differen Classificaions of Facial Type is approved in parial fulfillmen of he requiremens for he degree of Maser of Science Oral Biology School of Denal Medicine James Mah, D.D.S., D.M.Sc. Examinaion Commiee Chair Kahryn Hausbeck Korgan, Ph.D. Graduae College Inerim Dean Edward Herschaf, D.D.S., M.A. Examinaion Commiee Member Rober Danforh, D.D.S. Examinaion Commiee Member Bob Marin, D.D.S. Examinaion Commiee Member Debra Marin, Ph.D. Graduae College Faculy Represenaive ii

5 Absrac CBCT Evaluaion of Adolescen Mandibular Morphology in Differen Classificaions of Facial Type By Annie Hsu Dr. James K. Mah, Examinaion Commiee Chair Professor of Clinical Sciences Direcor of he Advanced Educaion Program in Orhodonics and Denofacial Orhopedics Universiy of Nevada, Las Vegas The goal of his sudy is o use he improved imaging capabiliy of cone-beam compuerized omography (CBCT) o invesigae he relaionship beween verical facial paerns and mandibular ooh-alveolar morphology in he adolescen populaion. Pre-reamen orhodonic records were obained from he UNLV School of Denal Medicine archival denal records. One hundred and seveny hree paiens (72 males, 101 females) beween he ages of 12 and 18 years were included in his sudy. Among hese paiens, 61 displayed he verical growh paern, 30 displayed he horizonal growh paern, and 82 displayed he average growh paern. The samples were caegorized ino 4 age groups for analysis: Group 1 (age 12 o 18), Group 2 (age 12 o 13), Group 3 (age 14 o 15), and Group 4 (age 16 o 18). Cross secional slices of he mandible were developed from he cone-beam scans o evaluae corical bone hickness, alveolar bone heigh, alveolar bone widh, ooh inclinaion, and alveolar bone inclinaion a four locaions. Each cross secion was measured a 10 sies, which included 5 corical bone hickness, 1 heigh, 2 widh, 1 ooh inclinaion, and 1 bone inclinaion measuremens. An analysis of iii

6 variance (ANOVA) wih pos-hoc Scheffé saisical analysis was used wih a significance level of p < Resuls of his sudy indicaed ha in all age groups he hyperdivergen facial ype generally had he hinnes corical bone, he highes alveolar bone heigh a he anerior region of he mandible, and he narrowes alveolar bone widh compared wih he oher wo facial ypes. The hyperdivergen facial ype had more uprigh lower incisor and more lingually inclined poserior eeh han he oher facial ypes. The alveolar bone inclinaion generally followed he same angulaion endency as he ooh inclinaion. The resuls of his sudy indicaes saisically significan differences exis in corical bone hickness, alveolar bone heigh, alveolar bone widh, ooh inclinaion, and bone inclinaion measuremens beween he various facial ypes in he adolescen populaion. iv

7 Acknowledgemens I would like o express my sinceres graiude o my advisor Dr. James Mah for his advice, ime, and suppor. His guidance has helped me remendously on his research projec and I will be forever graeful. I would also like o hank my oher commiee members Dr. Edward Herschaf, Dr. Rober Danforh, Dr. Bob Marin, and Dr. Debra Marin for heir encouragemen and dedicaion o his projec. Their assisance and guidance have helped me enormously in compleing my research projec. In addiion, I would also like o acknowledge Dr. Marcia Dimeyer for her assisance in analyzing he saisical daa. Lasly, I would like o hank my enire family for providing me wih uncondiional love and suppor. In paricular, I mus acknowledge my husband and bes friend, Seve, wihou whose love and encouragemen I would no have finished his hesis. v

8 Dedicaion To my husband Seve and daugher Naalie, Thank you for always believing in me and for all of your suppor. I love you boh more han words can say. vi

9 Table of Conens Absrac... iii Acknowledgemens... v Dedicaion... vi Lis of Tables... xi Lis of Figures... xii Chaper 1: Inroducion... 1 Purpose of Sudy...3 Research Quesions and Hypohesis...4 Chaper 2: Lieraure Review... 7 Verical Facial Types...7 Compued Tomography (CT) vs Cone Beam Compued Tomograph (CBCT)...9 Accuracy of CBCT Measuremens of Corical Bone...11 CT Sudies of Mandibular Morphology and Facial Types...13 CBCT Sudies of Mandibular Morphology and Facial Types...15 Chaper 3: Mehodology Subjecs...19 Deerminaion of Verical Facial Type...21 Adjusmen for Head Posiion...23 vii

10 Measuremen of he Tooh alveolar complex...23 Saisics...30 Chaper 4: Resuls Age Disribuion...31 Inra-Observer Error...33 Research Quesion Age Group 12 o 18 Years...34 Age Groups Subdivided...37 Research Quesion Age Group 12 o 18 Years...41 Age Groups Subdivided...43 Research Quesion Age Group 12 o 18 Years...48 Age Groups Subdivided...50 Research Quesion Age Group 12 o 18 Years...53 Age Groups Subdivided...55 Research Quesion Age Group 12 o 18 Years...59 Age Groups Subdivided...60 viii

11 Research Quesion Age Group 12 o 18 Years...64 Age Groups Subdivided...65 Chaper 5: Discussion and Conclusion Age Group 12 o 18 Years...69 Corical Bone Thickness...69 Alveolar Bone Heigh...72 Alveolar Bone Widh...74 Tooh Inclinaion...76 Bone Inclinaion...77 Age Groups Subdivided...78 Corical Bone Thickness...78 Alveolar Bone Heigh...79 Alveolar Bone Widh...80 Tooh Inclinaion...81 Bone Inclinaion...82 Limiaions and Fuure Sudies...83 Conclusion...85 Appendix A: UNLV Insiuional Review Board Approval Appendix B: Shapiro Wilk and Levene s Tes ix

12 Appendix C: ANOVA and Poshoc Scheffé References Curriculum Viae x

13 Lis of Tables Table 3.1 Verical Skeleal Measuremen Norms Table 3.2 Abbreviaions Used To Indicae Measuremen Sies Table 4.1 Sample Disribuion of each Age Group According o Gender Table 4.2 Sample Disribuion of Each Age Group According o Facial Type Table 4.3 Analysis of Inra-Observer Error Table 4.4 Means and Sandard Deviaions of Buccal Corical Bone Thickness Table 4.5 Means and Sandard Deviaions of Buccal Corical Bone Thickness Table 4.6 Means and Sandard Deviaions of Lingual Corical Bone Thickness Table 4.7 Means and Sandard Deviaion of Lingual Corical Bone Thickness Table 4.8 Means and Sandard Deviaions of Alveolar Bone Heigh Table 4.9 Means and Sandard Deviaions of Alveolar Bone Heigh Table 4.10 Means and Sandard Deviaions of Alveolar Bone Widh Table 4.11 Means and Sandard Deviaions of Alveolar Bone Widh Table 4.12 Means and Sandard Deviaions of Tooh Inclinaion Table 4.13 Mean and Sandard Deviaions of Tooh Inclinaion Table 4.14 Means and Sandard Deviaion of Alveolar Bone Inclinaion Table 4.15 Means and Sandard Deviaion of Alveolar Bone Inclinaion xi

14 Lis of Figures Figure 3.1. SN-GoMe Angle (red line) Figure 3.2. AFH (Blue Line) Figure 3.3. PFH (Blue Line) Figure 3.4. Mandibular Plane (Go-Me) parallels he floor Figure 3.5. Cross Secions in he Occlusal View Figure 3.6. Measuremen of Buccal and Lingual Corical bone (a) Figure 3.7. Measuremen of Basal Bone (b) Figure 3.8. Measuremen of Alveolar Bone Heigh (c) Figure 3.9. Measuremen of Alveolar Bone Widh (d) Figure Measuremen of he Tooh Inclinaion (e) Figure Measuremen of he Alveolar Bone Inclinaion (f) Figure 4.1. Buccal Corical Bone Thickness for All Facial Types Age 12 o 18 Years Figure 4.2. Buccal Corical Bone Thickness for All Facial Types Age 12 o 13 Years Figure 4.3. Buccal Corical Bone Thickness for All Facial Types Age 14 o 15 Years Figure 4.4. Buccal Corical Bone Thickness for All Facial Types Age 16 o 18 Years Figure 4.5. Lingual Corical Bone Thickness for All Facial Types Age 12 o 18 Year Figure 4.6. Lingual Corical Bone Thickness for All Facial Types Age 12 o 13 Years.. 47 Figure 4.7. Lingual Corical Bone Thickness for All Facial Types Age 14 o 15 Years.. 47 Figure 4.8. Lingual Corical Bone Thickness for All Facial Types Age 16 o 18 Years.. 47 Figure 4.9. Alveolar Bone Heigh for All Facial Types Age 12 o 18 Years Figure Alveolar Bone Heigh for All Facial Types Age 12 o 13 Years Figure Alveolar Bone Heigh for All Facial Types Age 14 o 15 Years xii

15 Figure Alveolar Bone Heigh for All Facial Types Age 16 o 18 Years Figure Alveolar Bone Widh for All Facial Types Age 12 o 18 Years Figure Alveolar Bone Widh for All Facial Types Age 12 o 13 Years Figure Alveolar Bone Widh for All Facial Types Age 14 o 15 Years Figure Alveolar Bone Widh for All Facial Types Age16 o 18 Years Figure Tooh inclinaion for all Facial Types Age 12 o 18 Years Figure Tooh inclinaion for all Facial Types Age 12 o 13 Years Figure Tooh inclinaion for all Facial Types Age 14 o 15 Years Figure Tooh inclinaion for all Facial Types Age 16 o 18 Years Figure Bone inclinaion for all Facial Types Age 12 o 18 Years Figure Bone inclinaion for all Facial Types Age 12 o 13 Years Figure Bone inclinaion for all Facial Types Age 14 o 15 Years Figure Bone inclinaion for all Facial Types Age 16 o 18 Years Figure 5.1. Incremenal Growh Curve Illusraing Growh Sages xiii

16 Chaper 1: Inroducion Verical facial morphology and is effec on he oucome of orhodonic reamen is of grea ineres for clinicians because he amoun and direcion of facial growh may aler biomechanics, reamen plans, and ulimaely oucomes (Schudy, 1964). There are imporan changes in verical facial dimension during he growh of he craniofacial region, and shor, average, and long facial ypes have disinguishing morphological and funcional differences (Bjork, 1969; Bjork & Skieller, 1972; Bresin, Kiliaridis, & Srid, 1999; Schudy, 1964; Skieller, Bjork, & Lende-Hansen 1984). Pas sudies ha have invesigaed craniofacial growh and verical facial morphology used laeral cephalograms and meallic implans as mehods of research. In some of hese sudies, researchers placed meallic implans in various sable regions of he maxilla and mandible and hen raced and superimposed he annual laeral cephalograms (Bjork, 1955). The researchers hen sudied he verical developmen of he face and he subsequen compensaory changes in mandibular roaion and eeh wih he implans as reference poins. These sudies have esablished ha hypodivergen individuals are characerized by shorer lower anerior face heigh wih longer poserior face heigh and have more forward roaion of he mandible during growh (Bjork, 1969; Bjork & Skieller, 1972). Because of he more upward and forward posiion of he mandible, he shor-faced individual herefore ends o have a more horizonal palaal plane and a lower mandibular plane angle. In addiion, a deep bie malocclusion ends o occur because as he mandible roaes upward and forward, he verical overlap of he eeh ends o increase (Bjork, 1969; Bjork & Skieller, 1972). The hypodivergen individual has a shor and wide face wih a square mandible and wide denal arches (Rickes, Roh, Chaconas, Schulhhof, & Engel, 1982). 1

17 Conversely, hyperdivergen individuals ypically have longer lower anerior face heigh wih shorer poserior face heigh and have more backward roaion of he mandible during growh (Bjork, 1969; Bjork & Skieller, 1972). Because of he downward and backward posiion of he mandible, he long-faced paien herefore ends o have a seeper palaal plane and a higher mandibular plane angle. Since he mandible roaes backward, here is a endency for anerior open bie and mandibular incisor prorusion o develop (Bjork, 1969; Bjork & Skieller, 1972). The hyperdivergen individual has a long and narrow face wih weak muscles and an obuse mandibular gonial angle (Rickes e al., 1982). I is believed ha mandibular roaion, mandibular plane, occlusal plane, gonial angle, occlusion, denal arch forms, mandibular shapes, corical bone hickness, and ooh inclinaions are differen beween he hree groups (Bjork, 1969; Bjork & Skieller, 1972; Bresin e al., 1999; Schudy, 1964; Skieller e al., 1984). Among hese variaions, he differences in he oohalveolar bone complex beween he facial ypes are especially imporan in orhodonic reamen planning and he subsequen success of reamen. Knowledge of he varians in buccolingual inclinaion of mandibular incisors and molars beween he facial ypes allows for proper reamen planning o ensure a sable occlusion. The knowledge of he alveolar bone morphology also assiss in deermining he locaion and placemen of emporary anchorage devices in order o achieve maximum sabiliy. An undersanding of he pos-reamen growh endencies furher assiss clinicians in making herapeuic decisions ha ensure pos-reamen sabiliy. Thus, for many reasons, i is imporan o undersand and invesigae he morphological characerisics of he mandibular body and is relaionship o facial ype. Researchers have invesigaed he relaionship beween verical facial paern and mandibular ooh-alveolar morphology in he pas. However, he limiaions of hese earlier 2

18 sudies are ha he sample sizes were small and he sudy populaions consised only of compued omography (CT) scans of dry skulls of male Asiaic Indians or modern Japanese males (Kasai e al., 1995; Kohakura, Kasai, Ohno & Kanazawa, 1997; Masumoo, Hayashi, Kawamura, Tanaka, & Kasai, 2001; Tsunori, Mashia, & Kasai, 1998). The appearance of conebeam compuerized omography (CBCT) echnology has opened new possibiliies for denal and maxillofacial assessmen and research. However, CBCT sudies evaluaing he relaionships beween mandibular ooh-alveolar morphology and facial ypes have been insufficien in number and scope (Han e al., 2013; Horner, Behrens, Kim, & Buschang, 2012; Ozdemir, Tozlu, & Germec-Cakan, 2013; Sadek, Sabe, & Hassan, 2014; Swasy e al., 2011). Previous CBCT research focused mainly on he adul populaion and only evaluaed limied aspecs of he oohalveolar mandibular morphology. In addiion, here are some conflicing findings derived from hese sudies. Purpose of Sudy The purpose of his sudy is o conduc a broad evaluaion of he mandibular oohalveolar morphology as relaed o differen facial divergences in he adolescen populaion. This sudy uses he improved imaging capabiliy of he CBCT o analyze a broader se of daa poins for a se of subjecs more represenaive of he orhodonic reamen populaion. Specifically, measuremens were aken of he corical bone hickness, heigh of he alveolar bone, widh of he alveolar bone, buccolingual inclinaion of eeh, and buccolingual inclinaion of he alveolar bone a four locaions in he mandible for male and female subjecs beween he ages of 12 and 18 years. These measuremens have hen been correlaed wih facial ype. Since he majoriy of he sudies performed previously focused on aduls, his projec s focus on adolescens was designed o idenify and assess issues ha are likely o arise in orhodonic pracice. 3

19 Research Quesions and Hypohesis 1. Is here a difference in he mandibular buccal corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he mandibular buccal corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. Null Hypohesis: There is no difference in he mandibular buccal corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 2. Is here a difference in he mandibular lingual corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he mandibular lingual corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. Null Hypohesis: There is no difference in mandibular lingual corical bone hickness beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 3. Is here a difference in he mandibular alveolar bone heigh beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he mandibular alveolar bone heigh beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. Null Hypohesis: There is no difference in he mandibular alveolar bone heigh 4

20 beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 4. Is here a difference in he mandibular alveolar bone widh beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he mandibular alveolar bone widh beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. Null Hypohesis: There is no difference in he mandibular alveolar bone widh beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 5. Is here a difference in he buccolingual ooh inclinaion beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he buccolingual ooh inclinaion beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. Null Hypohesis: There is no difference in he buccolingual ooh inclinaion beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 6. Is here a difference in he buccolingual inclinaion of mandibular alveolar bone beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes? Hypohesis: There is a difference in he buccolingual inclinaion of mandibular alveolar bone beween adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 5

21 Null Hypohesis: There is no difference in he buccolingual inclinaion of mandibular alveolar bone in adolescens wih normodivergen, hypodivergen, and hyperdivergen facial ypes. 6

22 Chaper 2: Lieraure Review Verical Facial Types The undersanding of verical facial growh and is implicaions wih regard o reamen are imporan opics in orhodonics. Two facial forms, namely he hyperdivergen and hypodivergen facial ypes, have been sudied exensively. individuals have been characerized as having a skeleal open bie or a long face while hypodivergen individuals have been characerized as having a skeleal deep bie or a shor face (Schendel e al., 1976, Schudy, 1964). Researchers have conduced various sudies o undersand verical facial growh and is implicaions in orhodonics. In 1964, a sudy invesigaed he relaionship beween poserior and anerior face heigh cross-secionally using 270 paiens wih an age range of 11 o 14 years (Schudy, 1964). Researchers concluded, based on measuremens of laeral cephalograms, ha he oal and lower anerior facial heighs were larger and he mandibular plane angles were higher in he skeleal open bie subjecs han in he skeleal deep bie subjecs. Oher invesigaors made similar observaions in 1976 and 1984 (Fields, Proffi, Nixon, & Sanek, 1984; Schendel e al., 1976). The 1976 sudy used 31 paiens wih an age range of 17 o 25 years wih verical maxillary excess (Schendel e al., 1976). Various angular and linear measuremens were made on laeral cephalograms and he conclusion was ha he oal anerior face heigh, and in paricular, he lower anerior face heigh, was increased in paiens wih a long face. I was also discovered ha he wo varians of he long-faced ype are hose who have an open bie and hose who have a non-open bie. Those who have a long face bu no open bie have an increased ramus heigh. Boh groups have a high mandibular plane angle and a normal upper lip lengh wih an excess display of maxillary anerior eeh (Schendel e al., 1976). The 7

23 1984 sudy also concluded ha long faces are also associaed wih higher Sella-Nasion o Mandibular Plane (SN-MP) angles (Fields e al., 1984) Longiudinal sudies of craniofacial growh uilizing meallic implans insered in jaws found ha forward mandibular condylar growh roaion is associaed wih he shor face cases while a backward mandibular condylar growh roaion is associaed wih he long face cases (Bjork, 1969; Bjork & Skieller, 1972). These sudies invesigaed growh changes in a sample of 100 children of each sex covering he ages of 4 o 24 years. Researchers examined growh changes using meallic implans placed in sable sies in he maxilla and mandible, and hen raced and superimposed annual laeral cephalograms. Researchers hen sudied he verical developmen of he face and he subsequen compensaory changes in mandibular roaion and eeh wih he implans as reference poins. The sudies found ha wih he shor-faced ypes he more forward roaion resuls in a more horizonal palaal plane, a lower mandibular plane angle, and a larger gonial angle. In addiion, when excessive roaion of he jaw occurs, he incisors end o move ino an overlapping posiion and herefore he endency for a deep bie develops (Bjork, 1969; Bjork & Skieller, 1972). Conversely, wih he long-faced ypes he more backward roaion of he mandible leads o a seeper palaal plane, a higher mandibular plane angle, and a smaller gonial angle. Wih an anerior open bie, incisors will need o erup for a greaer disance. The roaion of he jaws will hen carry he incisor forward and resul in denal prorusion (Bjork, 1969; Bjork & Skieller, 1972). Sudies also indicae ha here are biomechanical differences beween verical facial ypes which resul in morphologic and funcional differences. The size and orienaion of he masicaory muscles and he forces ha hey generae affec he developmen of he maxillofacial complex and facial divergence (Chan, Woods, & Sella, 2008; Sairoglu, Arun, & Isik, 2005). 8

24 There is an associaion beween increased facial divergence and reduced muscle funcion (Garcia-Morales, Buschang, Throckmoron, & English, 2003). Densiy and hickness of he corical bone of he mandible and maxilla also adap o masicaory forces and herefore resul in differen maxillomandibular morphology beween he facial ypes. Reduced muscle funcion correlaes wih a reduced amoun of corical and rabecular bone in he denoalveolar process (Bresin e al., 1999; Ichim, Kieser, & Swain, 2007). The forces generaed by he masicaory muscles affec he occlusion, denal arch forms, and mandibular morphology. The various sudies on verical facial dimensions indicae significan differences in craniofacial morphology and funcion beween he hyperdivergen, normodivergen, and hypodivergen facial ypes. These differences warran addiional invesigaion as his knowledge will aid he orhodonic clinician in reamen planning and achieving sable resuls. Compued Tomography (CT) versus Cone Beam Compued Tomography (CBCT) Tradiional wo dimensional imaging echniques used in he orhodonic specialy such as he panoramic radiograph or he laeral cephalomeric radiograph have he disadvanages of magnificaion, disorion, and superimposiion of srucures (Farman & Scarfe, 2009). Due o he many limiaions of hese wo dimensional image views, here has been a shif oward a hree dimensional approach o daa acquisiion and image reconsrucion including he use of compued omography (CT) and cone beam compued omography (CBCT) (Mah & Hacher, 2004). Three dimensional imaging are composed of voxels insead of pixels used in wo dimensional images. Voxels have heigh, widh, and hickness. All compued omography scanners consis of an x-ray source and a deecor mouned on a roaing ganry. As he ganry roaes, he recepor deecs x-rays aenuaed by he paien. A compuer algorihm hen reconsrucs he daa colleced o generae cross-secional images (Farman & Scarfe, 2009) 9

25 Compued omography can be caegorized based on x-ray beam geomery as eiher fan beam CT or cone beam CT. Mos hospial CT scanners use a fan-shaped x-ray beam and images are produced in axial plane slices. These slices need o be reassembled in he correc orienaion o consruc he volume from which subsequen reoriened slices can be made. The resulan voxels are no uniform in all planes, which means ha he precision in some measuremens can be compromised. CBCT scanners use a cone-shaped x-ray beam so ha a single C-arm roaion generaes several hundred basis images of raw daa, which are reconsruced o produce he complee denal or maxillofacial volume. The measuremens are generally precise in all dimensions because he voxels are isoropic, or uniform, in all planes (Farman & Scarfe, 2009; Mah & Hacher, 2004). CBCT offers several advanages over CT as he preferred imaging modaliy for denal and orhodonic assessmen. Since CBCT provides qualiy images of high conrasing srucures, i improves he abiliy o evaluae calcified srucures such as ooh alveolar morphology and corical bone in he mandible (Farman & Scarfe, 2009). Paien radiaion dose and scanning ime are lower as compared o convenional medical CT, which reduces arifacs creaed by movemen of he subjec. In addiion, CBCT measuremens are generally precise in all dimensions because he voxels are isoropic, or uniform, in all planes. CBCT offers he advanages of accurae, reliable, and high definiion images compared o convenional CT, MRI, and laeral cephalomeric headfilms wih a reduced radiaion dose (Mah, Danforh, Bumann, & Hacher, 2003). For all of he reasons cied above, CBCT echnology has emerged as he superior imaging modaliy for he sudy of mandibular ooh-alveolar morphology in he differen facial ypes. 10

26 Accuracy of CBCT Measuremens of Corical Bone CBCT is an increasingly popular echnology used in many specialies of denisry because of is high performance, low cos, and reduced radiaion dose compared wih convenional compued omography (Mah e al., 2003). Because CBCT is a relaively new advancemen, numerous sudies have been conduced o evaluae he accuracy of CBCT daa. Iniial sudies conduced in 2004 comparing direc measuremens wih CBCT measuremens on dry cadaver mandibles reveal ha linear disance measuremens are accurae wih CBCT wih a mean measuremen error of only 0.22mm (±15) (Kobayashi, Shimoda, Nakagawa, & Yamodo, 2004). More recen sudies have repored similar resuls wih he excepion ha possible measuremen inaccuracies can occur in areas of hin bone such as he mandibular anerior incisor region (Pacas, Muller, Ullrich, & Pelomaki, 2012). Research conduced in 2011 found only submillimeric differences in measuremens of cadaver buccal bone heigh and buccal bone hickness of 0.30 and 0.13 mm, respecively, and concluded ha CBCT imaging can provide accurae and reliable represenaions of buccal alveolar bone dimensions (Timock e al., 2011). This is consisen wih he findings of anoher 2010 sudy where mean absolue measuremen errors were 0.05mm and 0.07mm for he 0.25mm voxel-size scans and 0.4mm voxel-size scans, respecively (Damsra, Fourie, Huddleson, & Ren, 2010). A 2012 sudy also concluded ha CBCT is an appropriae ool o use for linear inraoral measuremens because accurae daa is provided and anaomic srucures are depiced reliably (Pacas e al., 2012). However, hese researchers noed ha in he areas of hin buccal bone in he mandibular anerior incisor region here is a risk of assuming fenesraions and dehiscence on CBCT radiographs ha do no exis clinically. Anoher sudy found ha when alveolar bone hickness is near or smaller han he 11

27 CBCT voxel size, alveolar bone heigh measuremens are likely o be underesimaed by 0.9 o 1.2mm (Sun e al., 2011). Bone can become invisible in a CBCT image due o wo facors: he parial volume averaging effec and conras resoluion (Sun e al., 2011). The parial volume averaging effec occurs when a voxel lies on wo objecs of differen densiies. This voxel reflecs he average densiy of boh objecs raher han he rue densiy of eiher objec. Therefore when he hickness of he alveolar bone is below or near he voxel size he voxel will reflec an average densiy of he alveolar bone and periodonal ligamen raher han he rue densiy of he alveolar bone. Bone may be hard o disinguish from adjacen periodonal ligamen srucures when he hickness is below or a he voxel size and herefore no aken ino accoun when measuring alveolar bone heigh (Sun e al., 2011). Conras resoluion deermines he abiliy o disinguish wo objecs of similar densiies and in close proximiy. The periodonal ligamen (approximaely 0.5mm hick) separaes he alveolar bone from he cemenum and anyhing smaller han his minimum disance requiremen could resul in he alveolar bone becoming indisinguishable from he cemenum (Sun e al., 2011). Areas wih bone less han 0.6mm hick were invisible on CBCT images (Leung e al., 2010). CBCT can be reliably used in he curren sudy of mandibular alveolar morphology of adolescens as he majoriy of measuremens of corical bone hickness and heigh are concenraed in he poserior mandible where here is greaer corical bone hickness. Resuls of pas research have demonsraed ha measuremens of a few millimeers wih CBCT are accurae and repeaable (Damsra e al., 2010; Kobayashi e al, 2004; Timock e al., 2011). The corical bone measuremens colleced in his research projec were generally 5 o 10 imes greaer han 12

28 he 0.38 mm voxel-size scans used. In addiion, recen research using sudy samples of fresh young pig heads wih bone equivalen o ha of early adolescen humans found ha for 0.40 mm voxel-size scans, measuremens in he mandibular molar regions were generally accurae (Wood e al, 2013). For he measuremens of mandibular anerior incisors in his curren invesigaion of adolescen mandibular morphology, measuremens of corical bone hickness were a 1/3 rd and 2/3 rd of alveolar bone heigh and no a he bone margin as used in pas sudies where corical bone can be exremely hin (Leung e al., 2010; Pacas e al., 2012; Wood e al., 2013). Mandibular anerior corical bone measuremens colleced in his sudy were generally 3 o 8 imes ha of he 0.38 mm voxel size, which decreased he chance of underesimaion of corical bone hickness. Alveolar bone heigh in he anerior incisor region may be underesimaed, however, if he corical bone hickness is a or below he voxel size. Therefore, he analysis of he resuls in his research projec mus address for his possible underesimaion of alveolar bone heigh. CT Sudies of Mandibular Morphology and Facial Types Facial ypes are imporan in orhodonics because hey influence anchorage usage, growh predicion of maxillofacial srucures, and goals of reamen. The significance of his relaionship has promped sudies o invesigae he relaionship beween verical facial ype and mandibular ooh alveolar morphology. Since CBCT was only inroduced in Europe in he 1990s and in Norh America in 2001, CT was he main imaging modaliy used o obain radiographic secions for measuremen in he earlier sudies of ooh-alveolar morphology as relaed o facial ype. In wo sudies, conduced in 1997 and 1998, researchers a he Deparmen of Orhodonics a Nihon Universiy School of Denisry a Masudo evaluaed he corical bone 13

29 hickness, ooh inclinaion, and bone inclinaion of he mandible using CT scans of 40 dry skulls and 39 dry skulls of male Asiaic Indians, respecively, and correlaed he findings wih verical facial paerns (Kohakura e al., 1997; Tsunori e. al, 1998). Boh sudies used a laeral radiograph of he skull for each specimen o deermine he facial ype. In addiion, boh sudies used four CT scan secions of he mandibular body a he lef lower incisor, lef lower second premolar, lef lower firs molar, and lef lower second molar for measuremens of he corical bone, ooh inclinaion, and bone inclinaion. Boh sudies found ha he hickness of he buccal corical bone srongly correlaed wih facial ype. The buccal corical bone of shor-faced subjecs was hicker han ha of average or long-faced subjecs for all secions measured in he 1998 sudy and only a he second premolar and firs molar for he 1997 sudy. The 1998 sudy found ha he lingual corical bone in shor-faced subjecs in he firs and second molar region was hicker han in oher facial ypes bu he 1997 sudy only found he same correlaion wih he second molar region. The 1998 sudy also found ha he second premolar, firs molar, and second molar were all more lingually inclined in he shor-faced group, while he 1997 sudy only found a correlaion wih he second molars. The 1997 sudy found ha he heigh a he second molar region was less han a he lower incisor region, while widh was greaer a he second molar region han a he lower incisor region in all facial ypes. In 2001, researchers sudied he CT scans of 31 dry skulls of modern Japanese males beween he ages of 18 and 45 years wih a mean average age of 27 years (Masumoo e al., 2001). Similar o he resuls of he 1998 sudy by Tsunori e al., he corical bone hickness of he firs molar and second molar secions was hicker in shor-faced subjecs han in average and long-faced subjecs. The lingual corical bone was hicker in he shor-faced paien in he lower hird region of he mandible. However, conrary o he 1997 and 1998 sudies, eeh of long- 14

30 faced subjecs were more lingually inclined han hose of shor-faced subjecs (Kohakura e al., 1997, Tsunori e. al., 1998). There is a consensus among he CT sudies ha buccal and lingual corical bone hickness is generally greaer in shor-faced subjecs alhough here are some sligh differences repored regarding which regions have he hicker corical bones (Kohakura e al., 1997, Masumoo e al., 2001, Tsunori e. al., 1998). The main dispariy in findings lies in wheher he poserior mandibular eeh are more lingually inclined in he shor-faced or long-faced group. The 2001 sudy found ha eeh of long-faced subjecs were more lingually inclined, while he 1997 and 1998 sudies found ha eeh of shor-faced subjecs were more lingually inclined (Kohakura e al., 1997; Masumoo e al, 2001; Tsunori e. al., 1998). CBCT Sudies of Mandibular Morphology and Facial Types The appearance of CBCT echnology has opened new possibiliies for denal and maxillofacial assessmen and research. The improved imaging capabiliy of he CBCT allows for more exensive and accurae invesigaion of mandibular morphology as relaed o facial form. Landmarks can be more precisely and easily idenified, and addiional measuremens can be aken, due o he 3-D naure of he images (Mah, Huang, & Choo, 2010). Sudies evaluaing he relaionships beween mandibular ooh-alveolar morphology and facial ypes using CBCT have been conduced in he pas few years, bu hese sudies have been limied in number and in is scope especially peraining o he mandibular morphology of adolescens. The earlier CBCT sudies evaluaing facial ypes and mandibular morphology focused mainly on measuremens of corical bone hickness in he adul populaion wih a mean age of 27 years in one 2012 sudy and an age range from 20 o 45 years in anoher 2013 sudy (Horner e al., 2012; Ozdemir e al., 2013). In hese sudies he digial communicaions in medicine 15

31 (DICOM) files of each CBCT scan were impored ino hree dimensional sofware and he images were oriened in hree planes of space so ha measuremens could be made on a cross secion of he alveolar bone a various sies in he mandible. Boh sudies found saisically significan differences beween he facial ypes in he buccal corical bone beween he premolar, firs molar, and second molar inerradicular sies in he mandible. Saisically significan differences in he hickness of lingual corical bone was found a wo sies (Horner e al., 2012). These sudies concluded ha he hypodivergen group has hicker corical bone a many sies in he mandible and hicker alveolar bone hickness in general han he hyperdivergen subjecs (Horner e al., 2012; Ozdemir e al., 2013). Researchers a he Universiy of California a San Francisco in 2011 used CBCT echnology o evaluae a larger age range of paiens which included a oal of 111 subjecs beween he ages of 10 and 65 years (Swasy e al., 2011). Alhough adolescens were included in he sudy, he invesigaion focused on he comparison of he mandibular corical bone hickness, heigh, and widh beween he facial ypes only. Consisen wih he findings of he 2012 and 2013 CBCT sudies, he 2011 CBCT sudy found ha subjecs in he shor-faced group had a hicker corical plae in many regions of he buccal and lingual areas while subjecs in he long-faced group had hinner corical bone in almos all sies in he mandible (Horner e al., 2012; Ozdemir e al., 2013). In he long-faced group, here was a considerable change in heigh of he mandibular cross-secional area from he molars o he symphysis wih maximum change in heigh occurring around he incisors. The long-faced group also showed a saisically significan narrower cross secion of he mandible in he upper hird region compared wih he average-face and shor-faced groups. This is consisen wih he findings of a 2014 CBCT sudy where he long-faced group was found o have he hinner alveolus and larger denoalveolar 16

32 heigh in he anerior mandible compared o he shor face group (Sadek e al., 2014). This 2014 sudy repored ha due o he hin alveolus here were significanly lower values for he maximum possible buccal lingual movemens of he cenral and laeral incisors in he long-faced group. A more comprehensive CBCT invesigaion of mandibular ooh alveolar morphology was performed by researchers in China in 2012 (Han e al., 2013). Corical bone hickness, basal bone hickness, inclinaion of eeh, inclinaion of bone, and heigh and widh of mandibular bone were all analyzed. Alhough his sudy of ooh alveolar morphology is more comprehensive han pas CBCT sudies, he analysis was resriced o 45 Chinese adul male and female subjecs beween he ages of 21 and 41 years. Consisen wih findings from previous CT and CBCT research, average hickness of he buccal corical bone was greaer in paiens wih he horizonal growh paern. This sudy found no saisical differences in he widhs of he mandibular bone beween he wo facial groups, which differs from he 2011 and 2012 CBCT sudies (Horner, e al., 2012; Swasy e al., 2011). This sudy also found ha he firs and second molars have a greaer buccal inclinaion in shor-faced paiens when compared o hose paiens wih a verical growh paern. This finding differs from he previous CT sudies of mandibular morphology where greaer molar buccal inclinaion was found in long-faced paiens bu agrees wih he findings of he 2001 CT sudy (Kohakura e al., 1997; Masumoo e al., 2001; Tsunori e al., 1998). There is consensus among he CBCT and he CT sudies ha corical bone hickness is greaer in he hypodivergen facial ype and hinner in he hyperdivergen facial ype in aduls (Han e al., 2013; Horner e al., 2012; Kohakura e al., 1997; Masumoo e al., 2001; Ozdemir, e al., 2013; Swasy e al., 2011; Tsunori e. al., 1998). Sudies have also concluded ha here is a 17

33 significan change in heigh of he mandibular alveolar bone wih he maximum change in heigh occurring around he incisors in he long-faced ype. The long-faced group has he larger anerior denoalveolar heigh in he mandible and he hinner alveolus compared o he shor-faced group (Han, 2012; Sadek e al., 2014; Swasy e al., 2011). However, here are differing conclusions on wheher here are differences in he alveolar bone heigh, alveolar bone widh, and ooh inclinaion beween he hree facial ypes. These differences in findings warran addiional research o provide furher clarificaion on hese opics. In addiion, more sudies invesigaing he ooh alveolar morphology of adolescens wih differen facial divergences should be conduced. 18

34 Chaper 3: Mehodology The following proocol, # M, was reviewed by he Office of Research Inegriy Human Subjecs a he Universiy of Nevada, Las, Vegas, and deemed excluded from IRB review (Appendix A). Subjecs A oal of 561 CBCT scans were obained from he UNLV School of Denal Medicine archival denal records from Augus 2006 o June All CBCT scans were aken by one radiology echnician rained in he echnique and operaion of he CBCT (CB MercuRay, Hiachi Medical Corp). Scans were aken wih a marix of 512 x 512, 193 mm FOV, 100 kv, 15 ma, and exposure ime of 10 seconds. The daa was sen direcly o a UNLV School of Denal Medicine compuer wih password proeced access and sored in Digial Imaging and Communicaions in Medicine forma (DICOM). Volumeric renderings of subjecs CBCT scans were evaluaed wih InvivoDenal version sofware (Anaomage, San Jose, CA). Of he 561 oal records, 173 (72 males, 101 females) subjecs beween he ages of 12 and 18 years were chosen for inclusion. Among hese paiens, 61 displayed he verical growh paern, 30 displayed he horizonal growh paern, and 82 displayed he average growh paern. CBCT scans were included only if hey were of good image qualiy and were absen of any movemen arifac. Subjecs wih complee deniion including full erupion of he second permanen molars, no remaining deciduous eeh, and symmeric mandibles were included. Subjecs wih missing or roo canal reaed eeh, large meallic resoraions, mandibular pahology, deciduous or incomplee deniion, syndromes or disease ha may affec craniofacial developmen, pas hisory of mandibular surgery, or currenly receiving orhodonic reamen 19

35 were excluded. The age range of 12 o 18 years was chosen as second molars have generally eruped by he age of 12 and adolescence has been commonly defined as spanning he ages of 12 o 18 years (American Academy of Pediarics, 2011; Dean, Avery, & McDonald, 2011). In addiion, daa colleced can be compared wih pas CBCT invesigaions of corical bone hickness in adolescens wih he age range of 13 o 18 years (Fayed, Pazera, & Kasaros, 2010). Adolescens are he focus of his sudy as hey consis of he main reamen populaion for orhodonics. Daa colleced were analyzed according o he following age groups: Group 1: Age ( 12 o 18 Age Group ) Group 2: Age ( 12 o 13 Age Group ) Group 3: Age ( 14 o 15 Age Group ) Group 4: Age ( 16 o 18 Age Group ) The combined age group of 12 o 18 years was also sudied and he resuls repored because of he limied sample sizes once he subjecs were classified in heir individual age subgroups. 3-D volumeric skeleal racings from hese scans were used o deermine he facial ype for each subjec. All images were reoriened so ha he mandibular plane (Gonion-Menon) was parallel o he floor. Measuremens were hen made of he buccal corical bone hickness, lingual corical bone hickness, basal bone hickness, mandibular alveolar bone heigh, mandibular alveolar bone widh, ooh inclinaion, and alveolar bone inclinaion in he cross secional image a four locaions in he mandible. All personal informaion regarding he subjecs was anonymized. Age, sex, and facial ypes for each individual were recorded independenly and only made available for his projec upon he compleion of daa collecion. 20

36 Deerminaion of Verical Facial Type The primary invesigaor performed 3-D volumeric skeleal racings o classify subjecs ino he normodivergen, hyperdivergen, and hypodivergen facial ypes based on sandard values (Table 3.1). The classificaions of facial ype was deermined by he angular measuremen Sella-Nasion and Gonion-Menon angle (SN-GoMe) and he linear Facial Heigh Index (FHI) measuremen. Subjecs had o fi ino a single facial ype caegory for boh measuremens in order o be included in he sudy. 1. SN-GoMe he angle formed by he Sella Nasion plane (S-N) o he Gonion-Menon (Go-Me) plane (Figure 3.1) Figure 3.1. SN-GoMe Angle (red line) 2. Facial Heigh index raio of poserior facial heigh (PFH) o anerior facial heigh (AHF) or PFH/AFH a. AFH Anerior Facial Heigh is he linear disance beween Nasion and Menon (Figure 3.2) 21

37 Figure 3.2. AFH (Blue Line) b. PFH Poserior Facial Heigh is he linear disance beween Sella and Gonion (Figure 3.3) Figure 3.3. PFH (Blue Line) Table 3.1 Verical Skeleal Measuremen Norms SN-GoMe ( )* FHI (%)* Normodivergen > 37 <61 Hypodivergen <27 >69 (Horn, 1992; Jacobson & Jacobson, 2006; Riedel, 1952) *Consisen wih he measuremen norms and sandard deviaions in Invivo

38 Adjusmen for Head Posiion The cross-secions aken of he mandible for measuremen purposes would differ depending on he mandibular plane angles of he subjecs sudied. Those who have a mandibular lower border ha closely parallels he floor would have a shorer cross-secion han hose wih a seeper mandibular plane. In order o correc for his facor, all subjecs were reoriened so ha he mandibular plane (Go-Me) was parallel o he floor (Figure 3.4). The reorienaion was performed wih he InVivo sofware by defining a horizonal plane in he coordinae sysem in he 3D Analysis ab and using gonion and menon as reference poins. Figure 3.4. Mandibular Plane (Go-Me) parallels he floor Measuremen of he Tooh alveolar complex A oal of four mandibular cross-secions (C1, P2, M1, and M2) were aken for each subjec. C1 is he cross-secion passing hrough he cener of he lower righ cenral incisor; P2 is he cross-secion passing hrough he cener of he lower righ second premolar; M1 is he crosssecion passing hrough he cener of he mesial roo of he lower righ firs molar; M2 is he cross-secion passing hrough he cener of he mesial roo of he lower righ second molar (Figure 3.5). 23

39 Figure 3.5. Cross Secions in he Occlusal View Because previous sudies repored ha corical bone widh is he same for boh sides of he jaw, only one side of he mandible was measured (Deguchi, Nsu, Yabuuch, & Takana- Yamamoo, 2006; Schwarz-Dabney & Dechow, 2003). Measuremens for each cross secion was performed in he Arch Secion ab of InVivo Slice hickness was se a 1.0mm. For each cross secion a oal of 10 measuremens were recorded. The corical bone was measured a 5 sies: 2 buccal, 2 lingual, and 1 a he base. One heigh, 2 widhs, 1 ooh inclinaion, and 1 bone inclinaion measuremens were also recorded. Firs, a lengh measuremen was made by drawing a line perpendicular o he mandibular plane a he heigh of he alveolar cres o he mandibular plane. This lengh was hen divided ino equal verical hirds. Two lines were hen exended perpendicular o his lengh a 1/3rd and 2/3rds he heigh and hese 2 lines served as reference poins for he corical bone hickness and widh measuremens (Figure 3.6). These measuremen procedures followed he proocol used in he CBCT sudy by Swasy e al. (2011). 1. Corical bone hickness (a): The 1/3 rd and 2/3 rds reference lines were used o deermine where he buccal and lingual corical bone hicknesses were measured. Two measuremens were aken of he buccal corical bone and wo measuremens were aken 24

40 of he lingual corical bone. The measuremen lines were angled in he same direcion ha he cross-secion was angled and posiioned a approximaely 90 degrees o he exernal surface of he corical bone. This was done o preven false readings aken obliquely hrough he corical plae (Figure 3.6). 2. Basal bone hickness (b): 1 measuremen was made a he base of he mandible (Figure 3.7). 3. Alveolar bone heigh (c): Heigh from he cener of he alveolar bone cres o he inferior border of he mandible. Measuremen was drawn along he long axis of he secion and placed approximaely hrough he cener of he slice (Figure 3.8). 4. Alveolar bone widh (d): Widh of he mandibular cross secion aken a 2 sies, using he same 1/3 rd and 2/3 rds reference lines used in measuring he hickness of he corical plaes. Widhs were recorded perpendicular o he heigh measuremen ha was aken hrough he long axis (Figure 3.9). 5. Tooh inclinaion (e): The angle beween he basal line (mandibular plane) and he ooh long axis. The long axis of he ooh is defined as he line passing hrough he midpoin of crown widh and he roo apex (Figure 3.10). 6. Bone inclinaion (f): The angle beween he basal line (mandibular plane) and he bone axis. The long axis of he bone is defined as he line passing hrough he middle poin of he buccal and lingual alveolar process and he inferior border of he mandible (Figure 3.11). 25

41 Figure 3.6. Measuremen of Buccal and Lingual Corical bone (a) Figure 3.7. Measuremen of Basal Bone (b) Figure 3.8. Measuremen of Alveolar Bone Heigh (c) 26

42 Figure 3.9 Measuremen of Alveolar Bone Widh (d) Figure Measuremen of he Tooh Inclinaion (e) Figure Measuremen of he Alveolar Bone Inclinaion (f) 27

43 Table 3.2 Abbreviaions Used To Indicae Measuremen Sies Second Molar CBB132M Second Molar Buccal Corical Bone a 1/3rd Heigh CBB232M Second Molar Buccal Corical Bone a 2/3rds Heigh CLB132M Second Molar Lingual Corical Bone a 1/3rd Heigh CLB232M Second Molar Lingual Corical Bone a 2/3rds Heigh BB2M Second Molar Basal Bone BHT2M Second Molar Alveolar Bone Heigh BW132M Second Molar Bone Widh a 1/3rd Heigh BW232M Second Molar Bone Widh a 2/3rds Heigh TIncl2M Second Molar Tooh Inclinaion BIncl2M Second Molar Bone Inclinaion Firs Molar CBB131M Firs Molar Buccal Corical Bone a 1/3rd Heigh CBB231M Firs Molar Buccal Corical Bone a 2/3rds Heigh CLB131M Firs Molar Lingual Corical Bone a 1/3rd Heigh CLB231M Firs Molar Lingual Corical Bone a 2/3rds Heigh BB1M Firs Molar Basal Bone BHT1M Firs Molar Alveolar Bone Heigh BW131M Firs Molar Bone Widh a 1/3rd Heigh BW231M Firs Molar Bone Widh a 2/3rds Heigh TIncl1M Firs Molar Tooh Inclinaion BIncl1M Firs Molar Bone Inclinaion Second Premolar CBB132P Second Premolar Buccal Corical Bone a 1/3rd Heigh CBB232P Second Premolar Buccal Corical Bone a 2/3rds Heigh CLB132P Second Premolar Lingual Corical Bone a 1/3rd Heigh CLB232P Second Premolar Lingual Corical Bone a 2/3rds Heigh BB2P Second Premolar Basal Bone BHT2P Second Premolar Alveolar Bone Heigh BW132P Second Premolar Bone Widh a 1/3rd Heigh BW232P Second Premolar Bone Widh a 2/3rds Heigh TIncl2P Second Premolar Tooh Inclinaion BIncl2P Second Premolar Bone Inclinaion Cenral Incisor CBB13CI Cenral Incisor Buccal Corical Bone a 1/3rd Heigh CBB23CI Cenral Incisor Buccal Corical Bone a 2/3rds Heigh CLB13CI Cenral Incisor Lingual Corical Bone a 1/3rd Heigh CLB23CI Cenral Incisor Lingual Corical Bone a 2/3rds Heigh 28