Congenital Missing Teeth On Maxillofacial Morphology Associated With Pax9 Gene Polymorphism Study

Part 1 Dento-facial morphology study of female children with congenital absence of mandibular incisorObjective The purpose of this study was to examine the dento-facial morphology of the female children with congenital absence of mandibular incisor.Methods Cephalometric analysis for 47 girls aged 12-15 with congenital absence of mandibular incisor (the test group) was conducted and compared with the cephalometric standards from 21 age-matched female subjects without hypodontia or malocclusion (the control group).Results There was no significant difference in all cephalometric measurements between the female children who lacked one mandibular incisor and those who lacked two. The hypodontia group showed smaller UI-NA(mm), IMPA and increased ANB, NA-PA,MP-SN,N-ME,ANS-ME, mandibular length compared to the control group.Conclusions Female children with congenital absence of mandibular incisor might have a skeletal class II appearance, greater retroclination of the anterior teeth, a more clockwise-rotated mandibular plane, an increased Vertical facial dimensions,lower Vertical facial dimensions and mandibular length.Part 2 PAX9 polymorphisms and susceptibility to sporadic tooth agenesis: a case-control study in southeast ChinaObjective To investigate the association between PAX9 gene polymorphisms and sporadic tooth agenesis in the general population of southeast China.Methods A total of 102 subjects diagnosed with sporadic tooth agenesis (excluding the third molar) and 116 healthy controls were consecutively recruited from the Stomatological Hospital of JiangSu Province (Nanjing), the Affiliated Hospital of Nanjing Medical University, from October 2005 to January 2007. All individuals participating in the study were genetically unrelated ethnic Han Chinese and were from Nanjing City and the surrounding regions in southeast China. A Molecular epidemiology was warranted to genotype these PAX9 polymorphisms.Results The allele and genotype frequencies of the four polymorphisms were not significantly different between the controls and the subjects with tooth agenesis. Similar results were observed in a subgroup analysis of test subjects only with mandibular incisor agenesis. Further analysis showed no significant difference in the haplotype distribution between the controls and the subjects with tooth agenesis or mandibular incisor agenesis. However, we found that the AGGC haplotype was associated with a decreased risk of tooth agenesis, compared with the most common haplotype, AGCC.Conclusion These results suggest that the four PAX9 polymorphisms alone have a non-significant main effect on the risk of tooth agenesis but that the AGGC haplotype may have a protective effect associated with a decreased risk of tooth agenesis.