Sexual Dimorphism in Third Molar Agenesis in Humans with and without Agenesis of Other Teeth

Simple Summary The assessment of differences between sexes (sexual dimorphism) in tooth formation allows for a better understanding of the developmental processes that contribute to phenotypical variations. Here, we tested for sexual dimorphism in the absence of third molar formation (agenesis) in modern humans with and without agenesis of teeth other than the third molars. No sexual dimorphism was detected in the patterns or the severity of third molar agenesis in any group. When teeth other than the third molars were absent, both sexes showed third molar agenesis and bilateral occurrence more often. There was no sexual dimorphism in the patterns or the severity of third molar agenesis, despite the higher vulnerability compared to other teeth. Moreover, there was no sexual dimorphism in single tooth agenesis with regard to any tooth. This indicates that the third molars are more often and more globally affected by genetic or epigenetic factors involved in tooth agenesis, with no differences between sexes. This is consistent with the evolutionary trend in humans towards a reduced molar number. In preadolescent patients with multiple tooth agenesis, the higher possibility of additional third molar agenesis should be considered during dental treatment planning. Sexual dimorphism in the human dentition is of interest from a developmental, evolutionary, and clinical point of view. Here, we investigated sexual dimorphism in third molar agenesis patterns and severity in non-syndromic white European individuals with (group A: 303 individuals) and without agenesis (group B: 303 individuals) of teeth other than the third molars. There was no sexual dimorphism in the patterns or the severity of third molar agenesis within groups. Both sexes showed a higher number of third molar agenesis per individual in group A than in group B. The most common third molar agenesis pattern was that of no third molars. For both females and males, bilateral third molar agenesis was approximately three times more frequent in group A than in group B (p < 0.001), whereas no difference was detected for unilateral agenesis. These findings indicate a strong genetic control of the developmental process of tooth formation, with any disruptions affecting both sexes in a similar manner. Overall, the higher vulnerability of third molar formation could be associated with the evolutionary trend in humans towards a reduced number of molar teeth, which seems to show no sex-related differences.

Automated summary

Sexual dimorphism in patterns and severity of third molar agenesis was investigated in non-syndromic white European individuals. No sexual dimorphism was found in the patterns or severity of third molar agenesis within groups. Both sexes showed a higher number of third molar agenesis in the group with other teeth agenesis. Bilateral third molar agenesis was more frequent in this group compared to the group without other teeth agenesis. These findings suggest strong genetic control of tooth formation and no sex-related differences in third molar agenesis.