| Objectives: According to Angle’s classification system, the Class â…¡subdivision malocclusion has one Class â… molar relationship side and Classâ…¡ on the other. Relational treatment planning has been essential andchallenging. Thus, accurate analysis of the malocclusion can facilitate clinicaltreatment planning. This study aim to analyze mandibular and dentalasymmetry of adults with Class â…¡ subdivision malocclusions, by comparingwith normal-occlusion subjects using cone-beam computed tomography.Methods: The subjects were divided into two groups. Thirty adultpatients with Angle Class â…¡ subdivision malocclusions (18male,12female,average age,24.6years) were selected from those who sought orthodontictreatment at the Orthodontic Department in Hospital of Stomatology, HebeiMedical University, from October2011to October2013, as Class â…¡ sub-division group. Thirty volunteers with normal occlusions (9male,21female,average age,21.5years) were chosen from the students of Hebei MedicalUniversity as normal occlusion group. All the individuals were informed ofthe study and agreed to participate. Pre-treatment CBCT scans were obtainedin the intercuspal position (ICP). The raw data was saved as digital imagingand communications in medicine (DICOM) files and imported into Invivosoftware. Skeletal and dental landmarks were set on the3D reconstructedmodels to conduct linear and angle measurements in maxillary and mandibulardentition and mandible.The landmarks are: maxillary dental midpoint, incisive foramen point,maxillary molar point, mandibular dental midpoint, mandibular molar point,condylar vertex, gonion point, menton point, and condylar midpoint. Based onthese points, several linear and angle measurements were conducted to set variables used to assess the asymmetry. Statistical analysis was made withSPSS13.0software. Significance level was set at0.05.Results:1In Class â…¡ subdivision group, cases withâ‘ only mandibular dentalmidline deviated,â‘¡only maxillary dental midline deviated, andâ‘¢bothmidlines deviated, account for60%(18cases),23%(7cases) and17%(5cases) respectively.2The variables of normal occlusion group had no significant differenceexcept for maxillary molar position and its2D length, with left side0.67±1.22mm and0.81±1.34mm longer than right side, respectively (P<0.05).3Asymmetry analysis of Class â…¡ subdivision group indicated that,asymmetry existed widely in maxillary and mandibular dental arch andmandibular body, as well as dental midlines.4Compared to normal occlusion group, subjects in Class â…¡ subdivisiongroup had smaller2D maxillary molar position difference, mandibular molarposition difference and mandibular body length difference and greater dentalmidline deviation (P<0.05).5As the results of correlation test to molar difference, mandibular molarangle showed significant negative correlation, while mandibular direct archlength difference,2D mandibular direct arch length difference and dentalmidline difference of Class â…¡ subdivision group showed significant positivecorrelation (P<0.05). In addition,2D and3D maxillary molar positiondifference and mandibular dental midline showed weak positive correlation,while mandibular ramus length difference, mandibular length difference and2D mandibular molar position difference showed weak negative correlation.Conclusion:1Subjects with Angle Class â…¡ subdivision malocclusions often havedental midline deviation, most in mandibular dental.2The development of Class â…¡ molar relationship mostly correlated tomandibular molar position. Maxillary molar position together with mandibleand ramus length contributed to some extent. |
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