A Three-Dimensional Research For Chin Morphology Of Class I Female With Congenital Absence Of Mandibular Incisor

Objective:This study was conducted to establish a three-dimensional measuring system for chin,and use it to investigate the morphological characteristics for chin of Class I Female with Congenital Absence of Mandibular Incisor.Method:Choose one patient attented Stomatological Hospital of JiangSu Province randomly and use Dolphin software to measure distance、angle、propotion、area and volume of the chin.Then check the consistency of the measurement.According to the inclusion criteria,we collected 239 CBCT data of class I female,including 127 with congenital absence of mandibular incisor and 112 with complete dentition.We use the new three-dimensional measuring system to evaluate the chin morphology and proceed statistical analysis by SPSS 22.0 to investigate relationship between incisor absence with chin morphology.Result:1.Congenital absence of mandibular incisor affect the chin morphology of average-angle Class I Female of different age group.The LCT(R)-LCT(T)decreases.The protrusion increases over 12 and the diagonal length decreases over 18.Between 12-26,the protuberance of lower lip,the horizontal distance from Po’/Si to LL decrease.The thickness of lower lip increases over 26.The mandibular process suffers hypodevelopment under 12 from a 2-D point of view,when over 18,it suffers hypodevelopment from a 3-D point of view.2.Congenital absence of mandibular incisor affect the chin morphology of teen-age Class I Female of different angle group The LCT(R)-LCT(T)decreases.The protrusion increases of average angle,the diagonal length decreases of lower-angle group,the protrusion increases of lower and average angle.The thickness of lower lip of lower angle and the protubence of the lower lip dreases,and the horizontal distance from Po’/Si to LL decrease of average angle.Conclusion:Chin morphology of class I female with congenital absence of mandibular incisor is different from those with complete dentition.We should pay more attention to the clinical diagnosis and treatment for patient with congenital absence of mandibular incisor.