Crown Morphological Characteristics of Angle Class II Division 2 Malocclusion Using ASUDAS

UCHIDA Shun* and ARAI Kazuhito

Angle Class II Division 2 malocclusion, characterised by a distal relationship of the mandibular first molar to the maxillary first molar, lingual inclination of the maxillary central incisors, and increased overbite, has been suggested to involve a heritable component. Non‑metric dental traits, such as shovel‑shaped incisors and the Carabelli trait, are also known in dental anthropology to reflect genetic influences and population variation, yet their expression in this dentition remains insufficiently understood. The aim of this study was to clarify intergroup differences in the expression of non‑metric dental traits in this dentition. Thirty individuals with Angle Class II Division 2 malocclusion comprised the II/2 group, and 30 individuals with normal occlusion, defined as no apparent occlusal abnormalities, comprised the control group. Non‑metric traits were scored using the Arizona State University Dental Anthropology System (ASUDAS). Crown morphology of all permanent teeth, excluding third molars, was scored on dental casts according to ASUDAS, and bilateral data were pooled. Intergroup differences were analysed using the chi‑square test (P < 0.05). Significant differences between the groups were observed for curvature (maxillary central and lateral incisors), shovelling (maxillary and mandibular central and lateral incisors), double shovelling (maxillary central and lateral incisors), hypocone (maxillary first molars), cusp number (mandibular second premolars), and cusp 5 (mandibular first molars). These findings indicate that individuals with Angle Class II Division 2 malocclusion exhibit distinct frequency distributions of multiple ASUDAS‑defined non‑metric traits compared with controls, providing a basis for further anthropological and genetic investigations.