Heritability Study On Skeletal Angle â…¢ Malocclusion

Objective:The purpose of the study was to explore the role and significance of genetic factor in the pathogenesis of skeletal angleⅢmalocclusion,according to familial aggregation and the heritability of different cephalometric parameters. Materials and methods:1 A case-control study of 90 skeletal angleⅢmalocclusion probands and 200 controls and their relatives,were investigated in the questionnaire.Analyze the prevalence rates of skeletal angleⅢmalocclusion in the first-degree relatives and second-degree relatives in the proband group and in the first-degree relatives in the control group.The familiar aggregation and the genetic mode were evaluated. Falconer regression method was applied.2 90 subjects and their parents were taken the lateral cephalogram,and 35 reference points were identified on each cephalogram,and 58 variables were calculated, both angular and linear.Heritalbility of different cephalometric parameters was calculated by mid-parent-offspring regression and parent-offspring regression.Results:1 The prevalence rates of skeletal angleⅢmalocclusion in the first-degree relatives and second-degree relatives in the proband group were 15.30%and 8.07%,respectively,which were higher than that in the first-degree relatives in the control group(1.58%).The heritability in the first-degree relatives was 88.3%. In the proband group,61.11%of families had at least 1 member other than the proband with skeletal angleⅢmalocclusion.The prevalence rate of men (10.71%) was higher.than that of the women(8.25%),but no statistically significant(x~2=1.791,P=0.181).2 According to the mid-parent-offspring regression:the heritability of the N-S-Ba, N-S-Ar,basal sagittal measurements,∠SNA,∠SNB,∠SNP,∠ANB,NA-PA, Pog-NB,Wits appraisal;basal vertical measurements,SN-MP,FH-MP,RP-MP, PP-MP,SN-PP,Y-axis,N-ANS/ANS-Me,showed the highest heritability(70%～90%);but the heritability in the dental variables and soft-tissue was low. 3 According to the parent-offspring regression,sons showed higher heritability to mother than father,and daughters showed higher heritability to father than mother. The heritability in the different craniofacial parts is slightly different between parents and children.Conclusions:1 In the skeletal angleⅢmalocclusion families,61.11%had at least 1 member other than the proband.2 The prevalence rate of probands' total relatives was 9.47%.The prevalence rates of skeletal angleⅢmalocclusion in the first-degree relatives and second-degree relatives in the proband group were 15.30%and 8.07%,respectively,which were higher than that in the first-degree relatives in the control group(1.58%).Skeletal angleⅢmalocclusion showed significantly familial aggregation.It belongs to polygenic inheritance model.3 The heritability for the first-degree relatives was 88.3%.4 Skeletal angleⅢmalocclusion had a significant heritability tendency between parents and offspring.Cranial,maxillary and mandibular skeletal parts showed stronger heritability,especially in the mandible,and the heritability in the dental variables and soft-tissue was low.5 Cephalometric data can support predictions,and analysis of parental data could have predictive value for offspring.6 The angular heritability was stronger than the linear heritability for craniofacial charateristics.