Abstract
In pediatric dental clinics, the degree of mandibular angle and anteroposterior manndibular length of a child is costumed to use the prediction of the occlusion of an adult in the case of Class 3 malocclusion. The mandible is a complex structure and the size and shape could be determined by genetic and environmental factors. The purpose of this study was to investigate the genetic factor to the degree of mandibular angle by QTL analysis using SMXA recombinant mice. We measured the degree of mandibular angle in 21 SMXA recombinant inbred (RI) strains and its parental strains, SM/J and A/J.The results were obtained as follows.1.Continuous distribution pattern of the degree of mandibular angle in SMXA RI strains suggests that the angle is not determined by a simple Mendelian inheritance but is controlled by multiple genes.2.It is conceivable that SM/J and A/J-derived alleles include both increasing and decreasing effects on growths of mandibular angle in SMXA RI strains as determined by the combination of SM/J and A/J-derived alleles.3.Based on the QTL analysis, it is suggested that the candidate genes of mandibular angle are mapped to a D 13 Mit 130 on chr. 13 with LOD score of 2.3, and NdA 29 on chr. X with LOD score of 2.2. These findings strongly suggest that mandibular angle is genetically controlled.
