Mandibular vertical asymmetry in adult orthodontic patients with different vertical growth patterns: A cone beam computed tomography study

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1 Originl Article Mndibulr verticl symmetry in dult orthodontic ptients with different verticl growth ptterns: A cone bem computed tomogrphy study Slih Celik ; Mevlut Celikoglu b ; Suleymn K. Buyuk c ; A. Ercn Sekerci d ABSTRACT Objective: To evlute condylr nd rml verticl symmetry in dult orthodontic ptients with different verticl growth ptterns nd cliniclly norml sgittl skeletl pttern using cone-bem computed tomogrphy (CBCT). Mterils nd Methods: The study smple consisted of 101 dult orthodontic ptients (48 men nd 53 women) divided into three groups ccording to their verticl growth ptterns: high- (33 ptients; men ge, yers), low- (34 ptients; men ge, yers), nd norml-ngle (34 ptients; men ge, yers) groups. Condylr, rml, condylr plus rml height, nd index mesurements were performed using CBCT imges nd nlyzed using one-wy nlysis of vrince nd post hoc Tukey tests. Results: There ws no sttisticlly significnt difference in height mesurements between right nd left sides in ech group, except slight difference of pproximtely 0.5 mm for condylr height (CH) in the low-ngle group (P,.05). No sttisticlly significnt gender differences were found for the vlues (P..05). In the high-ngle group, the rml height (RH) nd condylr plus rml height (CH + RH) on both sides were found to be less thn those of the low- (P,.001) nd norml-ngle groups (P,.017 nd P..017, respectively), nd the symmetry index vlues were slightly higher thn those of the low- nd norml-ngle groups (P..05). Conclusions: The high-ngle group showed sttisticlly significntly smller vlues of RH nd CH + RH on both sides nd sttisticlly insignificntly higher symmetry index vlues thn the lownd norml-ngle groups. (Angle Orthod. 2016;86: ) KEY WORDS: Condylr symmetry; Mndibulr symmetry; Cone-bem computed tomogrphy INTRODUCTION Verticl mlocclusions cn result from the interction of severl different etiologicl fctors including Assistnt Professor, Deprtment of Orl nd Mxillofcil Surgery, Fculty of Dentistry, Akdeniz University, Antly, Turkey. b Associte Professor, Deprtment of Orthodontics, Fculty of Dentistry, Akdeniz University, Antly, Turkey. c Assistnt Professor, Deprtment of Orthodontics, Fculty of Dentistry, Ordu University, Ordu, Turkey. d Assistnt Professor, Deprtment of Orl nd Mxillofcil Rdiology, Fculty of Dentistry, Erciyes University, Kyseri, Turkey. Corresponding uthor: Dr Mevlut Celikoglu, Deprtment of Orthodontics, Fculty of Dentistry, Akdeniz University, Antly, Turkey (e-mil: mevlutcelikoglu@hotmil.com) Accepted: My submitted: Mrch Published Online: June 11, 2015 G 2016 by The EH Angle Eduction nd Reserch Foundtion, Inc. growth of the jws, function of the lips nd tongue, nd dentolveolr development with the eruption of the teeth. 1 They might be divided into those tht re predominntly skeletl due to the growth ptterns of the mndible nd mxille nd those tht re dentolveolr in origin. Three bsic types of skeletl verticl growth ptterns exist: high- (hyper-), low- (hypo-), nd norml-ngle (normo-divergent). The high-ngle growth pttern is generlly ssocited with incresed verticl fcil growth, decresed posterior-to-nterior fcil-height rtio, incresed sell-nsion (SN) mndibulr plne (MP) ngle, incresed gonil ngle, nd incresed mxillry plne MP ngle. 2,3 On the other hnd, the low-ngle growth pttern is chrcterized by reduced verticl fcil growth, incresed posterior-to-nterior fcil-height rtio, decresed SN-MP, decresed gonil ngle, nd decresed mxillry plne MP ngle, 4 while the norml-ngle fcil growth pttern lies between those types. It hs been shown tht DOI: /

2 272 CELIK, CELIKOGLU, BUYUK, SEKERCI posterior rottion of the mndible hs mrked effect on mndibulr condyle morphology nd position. 5,6 Hbets et l. 7 described method for evluting mndibulr verticl symmetry by clculting the condylr nd rml heights to compre the right nd left sides of the mndible. Severl uthors hve used this method to ssess mndibulr symmetry in ptients with temporomndibulr disorders, 8 unilterl nd bilterl posterior crossbites, 9 11 vrious sgittl mlocclusions, unilterl 15 nd bilterl molr extrctions, 16 nd cleft lip nd plte. 17,18 Although mndibulr verticl symmetry hs ppered frequently in the literture, bibliogrphic serch in Medline using PubMed nd the key words condylr symmetry, mndibulr symmetry, verticl growth pttern, nd CBCT reveled tht no published study hs evluted condylr nd rml verticl symmetry using cone-bem computed tomogrphy (CBCT) in ptients with different verticl growth ptterns. Therefore, the im of the present study ws to evlute mndibulr verticl symmetry in dult ptients hving vrious verticl growth ptterns (high- nd low-ngle ptterns) nd cliniclly norml sgittl skeletl ptterns nd to compre the findings with well-mtched control group (norml-ngle) using CBCT. MATERIALS AND METHODS This study ws pproved by the locl ethicl committee of Erciyes University, nd ll ptients signed n informed consent form to llow use of their dt for scientific purposes. CBCT scns, tken for dignostic resons relted to previous dentl nd orthodontic or orthognthic surgery requirements, were rndomly selected from the rchives of Erciyes University. The ptients were therefore not exposed to ny dditionl rdition for the purpose of the present retrospective study. The study smple comprised totl of 101 ptients (53 women nd 48 men) ged yers (men ge, yers) divided into high-, low-, nd norml-ngle groups bsed on their verticl growth pttern using the SN-MP ngle (high ngle, $38u; low ngle, # 26u; nd control group or norml-ngle group, 26u 38u) s the criterion. 19 The smple included 33 ptients in the high- (22 women nd 11 men; men ge, yers), 34 ptients in the low- (16 women nd 18 men; men ge, yers), nd 34 ptients in the norml-ngle (15 women nd 19 men; men ge, yers) groups. All ptients hd skeletl Clss I (1u, ANB, 5u) 20 reltionships nd the sme ethnic origin, nd none hd unilterl or bilterl posterior crossbite. All CBCT dt were previously obtined in stndrd supine position with the sme mchine (NewTom 5G, QR Veron, Veron, Itly) using scnning time of 18 seconds, n exposure time of 3.6 seconds, collimtion height of 13 cm, nd voxel size of 0.3 mm 3. The imges were trnsformed to Digitl Imging nd Communictions in Medicine nd then Simplnt Pro softwre, version 13.0 (Mterilise, Leuven, Belgium) ws used to perform the mesurements. The symmetry mesurements were done rndomly by n experienced mxillofcil rdiologist without knowing the ptient s verticl growth pttern, nd n orthodontist performed the cephlometric mesurements (ANB nd SN-MP). Condylr height (CH), rml height (RH), nd condylr plus rml height (CH + RH) mesurements (Figure 1) were done s previously elborted in the literture. 11,18 The mndibulr verticl condylr, rml, nd condylr plus rml symmetry indexes (CAI, RAI, nd CRAI, respectively) were clculted using the formul described by Hbets et l. 7 Asymmetry index~ Right{Left 100 RightzLeft Sttisticl Anlysis To determine the rndom error, 25 CBCT imges were rndomly selected nd ll mesurements were repeted 3 weeks fter the first exmintion by the sme uthors without knowing the initil vlues. Correltion nlysis yielded the highest r vlue for right (RH; 0.993) nd the lowest for left (CH; 0.934) mesurements. The method error ws clculted using the Houston test, nd the results confirmed the relibility of the mesurements (the coefficients were bove.95). Since the Shpiro-Wilks test showed tht the dt were normlly distributed (P..05), prmetric tests were used. A Person chi-squre test ws performed to test gender distribution, nd one-wy ANOVA test for compring ge, ANB, SN-MP, CH, RH, CH + RH, CAI, RAI, nd CRAI vlues mong the groups. Tukey s honestly significnt difference test ws employed for compring individul differences, tking the Bonferonni correction into ccount (P,.017). A pired t test ws used to determine the potentil differences between right nd left sides for CH, RH, nd CH + RH mesurements for ech group. A Student s t-test ws used to determine the gender difference ccording to the symmetry indexes. All sttisticl nlyses were performed using the SPSS version 15.0 softwre pckge for Windows

3 MANDIBULAR VERTICAL ASYMMETRY 273 Figure 1. Mesurements used in the study. (SPSS, Chicgo, Ill); P,.05 ws considered sttisticlly significnt. RESULTS Tble 1 shows the descriptive dt of the ptients included in ech group. Gender distribution nd chronologicl ges of the ptients in ll groups were well mtched (tested by chi-squre nd one-wy ANOVA, respectively) (P..05 for both tests). Chronologicl ges of the ptients in the high-, low-, nd norml-ngle groups were yers, yers, nd yers, respectively. All ptients hd skeletl Clss I sgittl reltionship (men ANB, u) with no sttisticlly significnt differences mong the groups (P..05). Sttisticlly significnt differences were present mong the high-, low-, nd norml-ngle groups for the SN-MP ngle ( u, u, nd u, respectively) t significnce level of P,.001. Tble 2 shows the mens, stndrd devitions, nd sttisticl results of the pired t test compring the CH, RH, nd CH + RH mesurements of the right nd left sides in the ech group. There ws no sttisticlly significnt difference between the sides for those mesurements in ech group (P..05), except for slight difference of pproximtely 0.5 mm for CH in the low-ngle group (P,.05). The descriptive mndibulr symmetry indices for both women nd men were clculted seprtely in ech group to investigte the reltion between genders. No sttisticlly significnt gender differences were found for the vlues nd thus the dt were pooled for further sttisticl nlysis (Tble 3). Tble 1. Comprison of Demogrphic Vribles Among Different Verticl Ptterns Men ge (y) ANB (u) SN-MP (u) N Women/Men Men SD Men SD Men SD High ngle 33 22/ * 3.51 Low ngle 34 16/ * 2.39 Norml ngle 34 15/ * 1.77 Totl / P SD indictes stndrd devition. * P indictes sttisticlly significnt differences mong groups t P,.001.

4 274 CELIK, CELIKOGLU, BUYUK, SEKERCI Tble 2. Comprison of Height Mesurements Between Sides Among Verticl Groups High Angle Low Angle Norml Angle Right Side Left Side Right Side Left Side Right Side Left Side Vrible Men (mm) Men (mm) P* Men (mm) Men (mm) P Men (mm) Men (mm) P CH RH CH + RH CH indictes condylr height; RH, rml height; CR + RH, condylr-plus-rml height. * P indictes results of pired-smples t test. In the high-ngle group, RH nd CH + RH on both sides were sttisticlly significntly less thn those of the low-ngle group (P,.001). The high-ngle group hd sttisticlly significntly lower RH vlues on both sides compred with the norml-ngle group (P,.01). On the other hnd, the CAI, RAI, nd CRAI vlues in the high (11.54% %, 3.53% %, nd 3.29% %, respectively)- nd low (10.09% %, 2.63% %, nd 2.59% %, respectively)-ngle groups were found to be slightly higher compred with the norml-ngle group (8.57% %, 2.28% %, nd 2.27% %, respectively). However, these differences were sttisticlly insignificnt (P..05; Tble 4). DISCUSSION Mndibulr symmetry cn be ssessed by vrious tools including clinicl ssessment; photogrphs; rdiogrphs such s pnormic, frontl, nd lterl cephlogrms; computed tomogrphy (CT); nd CBCT. 21,22 Most previous studies 9,12 17,23 investigting the reltionship between condylr symmetry nd vrious mlocclusions were crried out using pnormic films. Although this technology hs n cceptble cost-benefit rtio becuse of its miniml rdition exposure, it suffers from limittions similr to those derived from the conventionl cephlometric nlyses including mgnifiction, distortion, nd superimposition of ntomicl structures. 24 Contemporry three-dimensionl technology mkes it fesible to chieve true (1:1 in size) imges devoid of mgnifiction. 10 Although rdition exposure could be n issue, CT is the gold stndrd for determining condylr symmetries. 25 In the present study, CBCT imges were used to ssess condylr nd rml verticl symmetry in dult ptients hving vrious verticl growth ptterns since CBCT provides reltively low rdition dose with low costs compred with CT. In ddition, Simplnt Pro softwre version 13.0 ws used to perform the mesurements. The threshold vlue could be set from the scn, the required structure could be seprted from its surrounding structures, nd the softwre llows us to visulize n re tht ws superimposed by other structures nd to evlute its ctul dimensions. 10 The Houston nd correltion nlyses confirmed the high relibility of the vrible vlues s previously reported for the CBCT imges of the twond three-dimensionl mesurements. 10,11,18, Compring right nd left sides for the CH, RH, nd CH + RH vlues in the high-, low-, nd norml-ngle groups showed only slight difference of pproximtely 0.5 mm for CH in the low-ngle group (P,.05), indicting n lmost symmetricl posterior verticl height of the mndible in ll studied groups. Similrly, no sttisticlly significnt differences were reported for right nd left sides in ptients with or without ny mlocclusion. 9,11,32 However, some uthors 23,33 using pnormic Tble 3. Comprison of Mndibulr Asymmetry Indexes Between Genders Men (n 5 48) Women (n 5 53) Group Vrible (%) Men SD Men SD P* High ngle (n 5 33) (W/M:22/11) Low ngle (n 5 34) (W/M:16/18) Norml ngle (n 5 34) (W/M:15/19) CAI RAI CRAI CAI RAI CRAI CAI RAI CRAI CAI indictes condylr symmetry index; RAI, rml symmetry index; CRAI, condylr-plus-rml symmetry index; W/M, women/men; SD, stndrd devition. * P indictes results of Student t test compring genders.

5 MANDIBULAR VERTICAL ASYMMETRY 275 Tble 4. Comprison of Mndibulr Height nd Asymmetry Vlues Among Groups Tukey HSD Vrible Group N Men SD P G1-G2 G1-G3 G2-G3 CH right High ngle Low ngle Norml ngle CH left High ngle Low ngle Norml ngle RH right High ngle Low ngle Norml ngle RH left High ngle Low ngle Norml ngle CH + RH right High ngle Low ngle Norml ngle CH + RH left High ngle Low ngle Norml ngle CAI High ngle Low ngle Norml ngle RAI High ngle Low ngle Norml ngle CRAI High ngle Low ngle Norml ngle CH indictes condylr height; RH, rml height; CR + RH, condylr-plus-rml height; CAI, condylr symmetry index; RAI, rml symmetry index; CRAI, condylr-plus-rml symmetry index; SD, stndrd devition; HSD, honestly significnt difference; G1, high ngle; G2, low ngle; G3, norml ngle. * P indictes results of one-wy ANOVA compring the three groups. films reported significnt side differences for ptients with unilterl crossbite, while recent studies 11,32 using CBCT imges hve indicted the similrity of right nd left sides in ptients with unilterl crossbite. The use of pnormic films in those studies 23,33 might hve cused this difference becuse of their low reproducibility compred with tht of the CBCTs. In contrst to the finding of Sglm, 13 we observed tht the symmetry indices were not ffected by gender (tested by mens of the Student t test); thus the dt were pooled for further sttisticl comprison. In greement with our finding, severl uthors 7,9,15,17,23 lso reported no sttisticlly signiicnt differences for symmetry indexes between genders. In the present study, CAI vlues in the high- (11.54% %) nd low-ngle (10.09% %) groups were found to be slightly higher thn those of the norml-ngle group (8.57% %; P..05). These vlues re higher compred with the 3% threshold vlue of Hbets et l., 7 showing tht ll ptients included in the present study hd symmetric mndibles ccording to the CAI vlues. The CAI vlues found in the norml-ngle group were less thn the findings of Celikoglu et l. 18 (12.11% %) nd Hlicioglu et l. 11 (10.58% %) using CBCT imges for the control groups hving norml occlusion. According to Hbets et l., 7 3% index rtio could result from 1-cm chnge in hed position while the pnormic film is being tken; therefore, symmetry index vlues greter thn 3% should be considered s mndibulr symmetry. Our study exmined this hypothesis becuse the ptient s hed position is not n ssessment criterion when using CBCT, nd the findings showed tht the investigtors interested in condylr symmetry should revise the 3% CAI threshold vlue of Hbets et l., 7 s reported previously. 11,18 In ddition, previous studies 13,16,17,32 using pnormic films lso reported tht CAI vlues in norml occlusion groups were over 7%, within the limittions of those films. Regrding the RAI nd CRAI vlues, no sttisticlly significnt differences were present mong the verticl groups, except slight increse in the high-ngle group (3.53% % nd 3.29% %, respectively)

6 276 CELIK, CELIKOGLU, BUYUK, SEKERCI compred with the low- (2.63% % nd 2.59% %, respectively) nd norml-ngle (2.28% % nd 2.27% %, respectively) groups. On the other hnd, the RH nd CH + RH vlues of both right nd left sides were highest in the low-ngle group, nd lowest in the high-ngle group (P,.001). In greement with our finding, significnt difference ws noted mong the verticl growth ptterns for rmus height, s the highest vlueinthelow-nglegroupndthelowestvlueinthe low-ngle group. 34,35 It is difficult to compre our findings with those of previous studies evluting condylr symmetry, s there hve been no studies investigting mndibulr verticl symmetry in different verticl growth ptterns. Thus, further studies re needed to prove or compre our findings. We did not include ny ptients with unilterl or bilterl crossbite or sgittl mlocclusion to eliminte those berrtions effect on mndibulr symmetry, since previous studies hve shown tht mndibulr symmetry vlues differ in ptients with unilterl or bilterl posterior crossbite 9,23,33 or Clss II or III mlocclusions 14,22 compred with norml occlusion groups. CONCLUSIONS N There ws no sttisticlly significnt difference in height mesurements between right nd left sides in ech group, except slight difference of pproximtely 0.5 mm for CH in the low-ngle group (P,.05). N No sttisticlly significnt gender differences were found for the symmetry index vlues (P..05). N In the high-ngle group, RH nd CH + RH on both sides were found to be less thn those of the low- (P,.001) nd norml-ngle groups (P,.017 nd P..017, respectively), nd symmetry index vlues were sttisticlly insignificntly higher thn those of the low- nd norml-ngle groups (P..05). 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