Archives

Introduction: Information regarding dental arch dimensions in human populations is important in different specialties including orthodontics. Arch shape and size affect stability of the dentition and plays important role in diagnosis and treatment planning.

Objective: The purpose of this study was to evaluate differences in dental arch morphology among different malocclusion groups.

Materials and Method: The sample consisted of 180 pretreatment orthodontic study casts. The subjects were classified into three groups according to Angle’s classification of malocclusion with each group consisting of 60 pairs of samples. Inter-canine width, inter-premolar width, inter-molar width, and intra-alveolar width were measured in each dental cast using digital caliper. ANOVA test followed by post-hoc Tukey test were done to compare among the different groups of malocclusion. Ratio of inter-molar to inter-canine width was also calculated and compared withthe Williams’ ratio.

Result: Arch width measured at ten different locationswere found to besignificantly larger in Class III samples, followed by Class I and Class II malocclusion groups except maxillary inter-alveolar width, mandibular inter-molar width and mandibular inter-alveolar width which were found to be least in Class I samples. Inter-molar to inter-canine width ratios wereapproximately 13:9 in upper arch and 15:9 in lower archin Class I samples.

Conclusion: Significant difference was observed in arch widths among different malocclusion groups. Inter-molar to inter-canine ratio was found to vary in Nepalese samples as compared to Caucasian norms. Maintaining thesenewly devised ratios in orthodontic treatment would ensure stability.

Alveolar width; arch width; dental arch; malocclusion; ratio.