Comparison between Class II Division 1 and 2 Malocclusions and Normal Occlusion regarding Tooth Size Discrepancy and Arch Dimensions using Digital Models

The orthodontists grant a considerable importance to dental arch dimensions to attain more stability of the dentition and better esthetics. The aim of this study was to measure tooth size disharmony and dental arch dimensions in both divisions of class II malocclusion and compare them to Normal occlusion as a control group using three dimensional digital models obtained from 3Shape E1 laser scanner (3Shape, Copenhagen, Denmark). This work was performed on 120 dental casts randomly selected from the records of patients (age range 16- 22 years) attending the Department of Orthodontics, Faculty of Dentistry, Mansoura University. Various parameters were measured including anterior and overall Bolton ratios, maxillary and mandibular intercanine, interfirst premolar and intermolar widths, maxillary and mandibular arch depth, palatal depth, depth of curve of Spee, overjet and overbite. Mean and standard deviation were calculated. One-way ANOVA was used to detect possible differences between groups. The findings indicate that Class II division 1 malocclusion showed significantly greater maxillary arch depth, palatal depth, mandibular intercanine, interpremolar and intermolar widths and larger overjet amount in comparison with Class II division 2, while revealed significantly higher values of maxillary arch depth, mandibular intermolar width, curve of Spee, overjet and overbite than Normal Class I. On the other hand Class II division 2 malocclusion had significantly greater overall Bolton ratio, maxillary intermolar width, curve of spee depth and overbite than Class II division 1, while it showed deeper curve of Spee and larger amount of overjet and overbite compared to Normal Class I. The results of the current study can help the clinicians in treatment planning and provide guidance for proper selection of arch wires to obtain post-treatment stability.