利用下顎骨的全口顎影像分析預測台灣人之性別

Abstract

性別和年齡是法醫師做人身鑑定最先需要解決的兩個問題，而除了骨盆骨之外，頭顱骨是最具性別雙形性的骨頭，其中下顎骨因為堅硬厚實，是法醫實務上最常遇到的人類殘骸。根據過去文獻，不同種族的下顎骨形態有所差異，因此各國利用下顎骨判別性別或年齡需要使用個別族群的資料，而就我們所知，目前台灣法醫人類學缺乏這方面的研究。本研究就是希望收集台灣人下顎骨形態資料，建立迴歸公式以預測性別或年齡。 本研究屬於一種 hospital-based study，使用立意抽樣法（purposing sampling）選取樣本，資料來源為 2012 年 1 月至 2014 年 12 月於國立臺灣大學附設醫院牙科部門診進行全口顎攝影的個案。研究收集 16 歲至 76 歲男性及女性全口顎影像資料，以 DICOM 軟體（RadiAnt DICOM Viewer）進行下顎骨影像上八個參數的測量。 本研究收集男女各 120 位影像資料的測量結果，並利用測量真實下顎骨上金屬貼片進行全口顎影像放大率的校正。受測者男性年齡範圍 16 至 75 歲，平均年齡 45.22 歲，平均總牙數為 27.84 顆，下顎骨上則為 13.94 顆，受測者女性年齡範圍為 16 至 76 歲，平均年齡為 45.4 歲，平均總牙數 27.82 顆，下顎骨為 13.91 顆，所有測量結果依照不同性別、年齡分層進行比較統計。研究結果顯示，全部下顎骨參數，不管校正前或校正後都和性別具有顯著相關，男性除了下顎角（gonial angle）平均值小於女性之外，其餘參數如下顎枝高（ramus height）、下顎投影枝高（projected ramus height）、下顎兩髁頭寬（bicondylar width）、下顎角寬（bigonial width）數值都較女性大，且具有顯著意義。校正前下顎骨參數以枝高最具有兩性雙形性，利用枝高單一參數建立迴歸公式的性別預測正確率為80.56%，而利用枝高、投影枝高組合的迴歸公式可得到較高的預測性別正確率83.33%。校正後下顎骨參數以兩髁頭寬較具有性別雙形性，利用單一參數兩髁頭寬預測性別正確率為 94.44%，男女性別分界值為 98.88mm，而利用兩髁頭寬和投影枝高組合來預測性別，正確率可達 91.67%。另研究指出年齡和下顎骨各參數皆不具有相關性，不管校正前後皆是如此，除了下顎角隨著年齡增長有稍微變小的趨勢外，其他參數則呈現波動之變化，並無一致的方向。 在本研究中，我們確認了台灣人口下顎骨形態和性別或年齡的關係，並建立性別和下顎骨參數邏輯迴歸公式，提供法醫師實務上人身鑑定判別性別的一個輔助工具，讓法醫師可以不用再使用國外不同種族的資料，以增加判別性別的精確度。

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.