Analytic sex prediction in Taiwanese by using panoramic radiography of the mandible

The sex and age are the major problems to be solved in identification of human remains by forensic physician. Skull is the most dimorphic skeleton, except bones of pelvis. Mandible is the most encountered human skeletal remains due to its robusticity in forensic practice. In the literature, the discrepancies were observed between different ethnic mandibular morphology. It needs to use individual ethnic database of mandible to identify sex or age of victims. To our knowledge, forensic anthropology of Taiwan lacks study about this as far. Therefore, this study expects to collect the mandibular morphologic datas of Taiwanese and establishes regression formulas to predict sex and age. A hospital-based study with purposive sampling was conducted. The material included those who had undergone orthopantomography (OPT) in OPD of dental department of National Taiwan University Hospital from January, 2012 to December, 2014. The study included panoramic images of Taiwanese aged from 16 to 76 years old. Measurements were taken at eight parameters of mandibular images using DICOM software (RadiAnt DICOM Viewer). In this study, the results of image data were collected including 120 male and 120 female. To adjust the magnification rate of panoramic radiography, the metal markers on mandibular bone was used. Male age ranged 16-75 years; mean 45.22 years; total average teeth number 27.84; residual mandibular teeth number 13.94 and female age ranged 16-76 years; mean 45.4 year; total average teeth number 27.82; residual mandibular teeth number 13.91. The measurement results were categorized according to sex and age classification to analyze. The results showed all parameters of mandible were sexual dimorphic significantly whatever adjustment or not. The mean values of ramus height, projected ramus height, bicondylar width and bigonial width of male is bigger than female significant statistically, besides mean gonial angle of female is bigger than male. The ramus height is the most sexual dimorphic among pre-adjusting mandibular parameters. The predictive accuracy of gender is 80.56% with the regressive formula created by using unique ramus height. And the predictive accuracy of gender is higher , 83.33%, with combination of ramus height and projected ramus height. Bicondylar width is more sexual dimorphic among post-adjusting mandibular parameters. The predictive accuracy of gender is 94.44% with unique bicondylar width. And the demarking point of gender is 98.88mm. Using the bicondylar width and projected ramus height together to predict gender, the accuracy is up to 91.67%. But the research indicated the mandibular parameters were not significant related to age, no matter what adjusting or not. Although gonial angle decreased slightly as aged, other parameters had no consistent trends with age. In our study, we established the relation between mandibular morphology of Taiwanese and gender or age, and developed a logistic regression formula of mandibular parameters with gender. The regression formula is valuable to apply in identifying human gender and could be used as an accessorial tool to elevate the predictive accuracy of gender without using the foreign database.