Evaluation of skeletal and dental asymmetries in Angle Class II subdivision malocclusions with cone-beam computed tomographyby Craig M. Minich, Eustáquio A. Araújo, Rolf G. Behrents, Peter H. Buschang, Orlando M. Tanaka, Ki Beom Kim

American Journal of Orthodontics and Dentofacial Orthopedics




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Evaluation of skeletal and

Angle Class II subdivision cone-beam computed tom

Craig M. Minich,a Eustaquio A. Araujo,b Rolf G. Behrents,b and Ki Beom Kime

Chagrin Falls, Ohio, St Louis, Mo, Dallas, Tex, and Curitiba, Paran rmin s II a t pho the C ere p pare e. R e to t ticall lation ars a between the Class I and Class II sides. The dental asymmetry. (Am JOrthod Dentofacial Orthop 2013;144:57-66)

C fyin subd both try b asym mec cate , or tric elnal ion the ctly phs differences between the 2 sides were primarily found no statistically significant skeletal differences

Professor, Department of Orthodontics, Baylor College of Dentistry, Texas A&M

Health Science Center, Dallas, Tex. 0889-5406/$36.00

Copyright  2013 by the American Association of Orthodontists.

ORIGINAL ARTICLEdentoalveolar. The main factor is the distal positioning of the mandibular first molar on the Class II side with a mandibular dental midline deviation toward the

Class II side (type 1). A secondary factor is the mesial positioning of the maxillary first molar on the Class II side with a maxillary dental midline deviation away from the Class II side (type 2).1,4,11-13 These authors dProfessor, Graduate Dentistry Program in Orthodontics, School of Health and

Biosciences, Pontifıcia Universidade Catolica do Parana, Curitiba, Parana, Brazil. eAssociate professor, Department of Orthodontics, Center for Advanced Dental

Education, Saint Louis University, St Louis, Mo.

All authors have completed and submitted the ICMJE Form for Disclosure of

Potential Conflicts of Interest and none were reported.

Reprint requests to: Ki Beom Kim, 3320 Rutger St, St Louis, MO 63104; e-mail, kkim8@slu.edu.

Submitted, December 2012; revised and accepted, February 2013.(posteroanterior cephalograms, submentovertex view, and corrected oblique cephalograms) to evaluate Class

II subdivisions for dental and skeletal asymmetries between the Class II and Class I sides of the skull and the dentition.1,4,9,10 These studies showed that the aPrivate practice, Chagrin Falls, Ohio. bProfessor, Department of Orthodontics, Center for Advanced Dental Education,

Saint Louis University, St Louis, Mo. chttp:/lass II subdivision malocclusions can be extremely challenging for diagnosis and treatment planning because many clinicians have difficulty in identig the cause of the malocclusion.1 Since Angle Class II ivision malocclusions possess characteristics of

Class I and Class II malocclusions, there is asymmeetween the right and left sides of the dentition. This metry often requires asymmetric extractions or hanics during treatment, which can be very complid.1-4 The etiology of the asymmetry can be quite complex. It could be dental related, skeletal related a combination of both.

Any time a dental midline deviation or an asymme occlusion is observed, the clinician must check for sk etal asymmetries, dental asymmetries, and functio shifts.5-8 Manipulating the patient into centric relat or using an occlusal splint to verify the position of mandible is an important first step in corre diagnosing any type of asymmetry.5

Previous studies used 2-dimensional radiograIntroduction: The purpose of this study was to dete have skeletal or dental asymmetries between the Clas

Angle Class II subdivision patients with pretreatmen scans was used. The photos were used to identify amount of crowding per quadrant. Landmarks w dimensional measurements could be made to com dental structures on the Class II side vs the Class I sid etal measurements: the position of the maxilla relativ the mandibular foramen to the mental foramen. Statis sition of the mandibular first molars and canines in re icant differences were found for the maxillary first mol

There were significant skeletal and dental differences metries accounted for about two thirds of the total asym/dx.doi.org/10.1016/j.ajodo.2013.02.026dental asymmetries in malocclusions with ography

Peter H. Buschang,c Orlando M. Tanaka,d a, Brazil e whether Angle Class II subdivision malocclusions nd Class I sides.Methods: A sample of 54 untreated tos and cone-beam computed tomography (CBCT) lass II subdivision malocclusion and to record the lotted on each CBCT volume so that direct 3the positions and dimensions of the skeletal and esults: Significant differences were found for 2 skelhe cranial base, and the mandibular dimension from y significant dental differences were found for the poto the maxilla and the mandible. Statistically signifnd canines in relation to the mandible. Conclusions:between the 2 sides, but they mentioned a tendency 57 of the sella and perpendicular to the x-axis through the middle of the sella.

By establishing the x-, y-, and z-axes, 3 planes in space were created that intersected at the origin. The origin (0, 0, 0) was located along the midsagittal plane, just below the sella, and at the level of Frankfort horizontal.

After the reconstructed model was oriented and the axes and planes were defined, landmarks could be plotted in precise anatomic locations by using sagittal, coronal, and axial slices of the CBCT volume.

Twenty-one digital landmarks, skeletal and dental, were selected based on ease of identification and reproducibility (Fig, Table I). Three midline landmarks—origin, incisive foramen, and genial tubercles—were chosen to represent the middle of the cranial base, the maxilla, and the mandible, respectively. The other 18 landmarks were located on the right and left halves of the skull and dental arches.

Each landmark was assigned unique coordinates (x, y, z) when it was plotted in the Dolphin 3D software.

These coordinates could then be copied and pasted into

Excel (Microsoft, Redmond, Wash), with a spreadsheet designed so that the direct measurements in millimeters 58 Minich et alfor mild skeletal asymmetries in Class II subdivisions and recommended further research to investigate these minor asymmetries.13,14

The purpose of this study was to analyze Class II subdivision malocclusions for skeletal and dental asymmetries by using cone-beam computed tomography (CBCT).