Hypodontia as a predictor of third molar agenesis: A comparative cross-sectional study according to sex and tooth type in a French orthodontic population

Abstract

Objectives

The aim of this study was to determine the patterns of third molar agenesis and to investigate potential relationships with the agenesis of other permanent teeth, the type of missing teeth, and sex.

Methods

Panoramic radiographs from 4081 orthodontic patients aged 11 to 21 years were examined to identify non-syndromic tooth agenesis, including third molars. McNemar's Chi-square tests were used to compare the prevalence of third molar agenesis between jaws or sides. Logistic regression analyses were conducted to explore associations between the occurrence or patterns of third molar agenesis and potential explanatory factors.

Results

Third molar agenesis was observed in 19.0% of the sample (19.3% for females and 18.7% for males). The most common patterns of third molar agenesis were bilateral absence of the lower third molars (16.8%) and all third molars missing (16.7%). Third molar agenesis was 3.92 (95% CI = 3.07–5.00; P < 0.001) times more likely to occur when other permanent teeth were congenitally missing. The congenital absence of maxillary lateral incisors was associated with the agenesis of third molars in the maxilla (OR = 3.93; 95% CI = 1.07–13.70; P = 0.034). At least one missing mandibular third molar was involved in the patterns associated with the agenesis of other permanent teeth. No sexual dimorphism was observed.

Conclusion

Third molar agenesis appears to represent a continuum with the agenesis of other teeth, reflecting strong genetic control, affecting both sexes similarly.