Prevalence and patterns of tooth agenesis in Angle Class II Division 2 malocclusion in Japan

Introduction: The purpose of this study was to evaluate the prevalence and patterns of tooth agenesis in subjects with Angle Class II Division 2 malocclusion compared with general orthodontic patients in Japan.

Methods: Panoramic radiographs, dental casts, and cephalograms of 76 patients with Class II Division 2 malocclusions (52 female, 24 male) and 270 orthodontic patients as the control group (168 female, 102 male) who were 14 years of age or older were selected. The prevalences of tooth agenesis in this cohort and in each tooth type were calculated and compared between the groups with the chi-square test. Odds ratios and corresponding 95% confidence intervals were also calculated.

Results: The prevalence of tooth agenesis excluding the third molars was significantly higher in the Class II Division 2 group (22.4%) than in the control group (11.9%) (P <0.05); the odds ratio was 2.14 (95% CI, 1.12-4.12). A higher prevalence of tooth agenesis excluding the third molars was observed in the Class II Division 2 group for the mandibular second premolar (P <0.05) and the maxillary lateral incisor (P <0.01). The prevalence of third molar agenesis was also significantly higher in the Class II Division 2 group (42.1%) compared with the control group (26.7%) (P <0.05); the odds ratio was 2.00 (95% CI, 1.18-3.40).

Conclusions: Compared with the general orthodontic patient population, permanent tooth agenesis was observed approximately 2 times more frequently, and a distinctive agenesis pattern was found in the Class II Division 2 group in Japan.