Gender differences in patterns of second premolar agenesis observed in 4,756 individuals

To elucidate intra- and inter-maxillary patterns of second premolar agenesis in the mandible and maxilla-including unilateral and/or bilateral occurrence and gender differences.

The study comprised panoramic radiographs from 4,756 children with and without orthodontic treatment needs.

All radiographs were screened twice. 251 individuals had agenesis of one or more mandibular and/or maxillary second premolars; 37 had agenesis of both mandibular and maxillary second premolars.

Gender differences were analysed using χ² and Fisher's exact test.

193 individuals had agenesis of one or both mandibular second premolars, while 95 had agenesis of one or both maxillary second premolars. In females, agenesis of left and right second premolars was significantly associated in both the mandible and in maxilla (p < 0.0001). In males, this association was only significant in the maxilla (p < 0.0001). Bilateral agenesis occurred almost twice as frequently in females. Unilateral agenesis in the maxilla occurred almost twice as frequently in females. The probability of finding second premolar agenesis in the maxilla was significantly greater in females than in males (p = 0.03). A significant association was seen between agenesis of tooth 25 and 35 in females and males combined (p = 0.03) and in males alone (p = 0.01). No significance was found between agenesis of tooth 15 and 45 in either females or males.

The study confirms some previous findings of second premolar agenesis and presents new observations on gender differences, especially concerning associations in agenesis occurrence within and between the jaws.