Examination of new parameters for sex determination of mandible using Japanese computer tomography data

Abstract

Objective: In the field of forensic science, sex discrimination of skeletons is an important identification item for personal identification. The individual sex discrimination method using skeletons includes a determination method using measurement values and a macroscopic form observation method. Both methods have advantage and disadvantage. In this study, we used the homologous model technique and principal component (PC) analysis to determine gender difference from morphology of the mandible. Methods and materials: 45 patients (23 males and 22 females) of CT imaging for tooth extraction from January 2018 to March 2019 at department of oral surgery, Osaka Medical College. The mean age was 43.1 ± 14.6. Patients with less than 14 remaining teeth were excluded because the number of remaining teeth may affect the shape of the mandible. 3D images were constructed, and 20 landmarks plotting on the 3D model surfaces. We generated template models of the mandible consisting of approximately 8434 polygons. The template model automatically fitted into the individually scanned point cloud of the mandible by minimising external and internal energy functions. As described above, the mandibles were constructed for each sample by using the Homologous Body Modeling software (HBM, Digital Human Technology, Inc.) and the mHBM-Rugle (Medic Engineering Corporation). The mandibles were analysed using the PCA. Results: The contribution of the most important PC was found to be 27.2%. 12 PCs explained over 75% of the total variance. That is, it was able to express 75% or more of the mandible expression with 12 PCs. A significant difference between male and female was observed in the first PCs (Wilcoxon test, p < 0.05). Visualising the result of the first PC showed that the mandibular branch of male was larger than that of female, and the mandible angle was overhanging outside. Conclusion: This method is a combination of the determination method using the previous measurement values and the determination using macroscopic observation, and is considered to be innovative method.

A three-dimensional statistical shape model of the growing mandible

“…Cross-sectional studies that have investigated the shape of the mandible often suffer from the same limitations 26,36,39 . There are several reports on the natural variation in morphology of the mandible, but these pertain to the adult mandible only [20][21][22][23][24][25] 33,34,40 , and have the most comparable data sets to the current study. Of the research with a similar age range as the present study, four studies employ PCA to investigate the morphology of the mandible 27,[33][34][35] .…”

“…Some studies investigated one aspect of the mandible, such as the condyle 10-13 , ramus 14 , mandibular canal [15][16][17][18] , or the lingula 16,19 . Several authors attempted to describe the shape [20][21][22][23][24][25] or the growth of the mandible as a whole [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] . Limitations of these studies mainly involve a small sample size, narrow age range, selection bias, or extensive manual input, such as landmark annotation.…”

Objective evaluation of tooth carving using homologous models

“…A new method that applies homologous models has been used in the 3D shape analysis of the human body. [12][13][14][15] The concept of homologous models is to represent the object shape by a polyhedron of homotopic geometric structure using the same number of anatomically mapped points; thus, it can be used to create an average shape using the arithmetic mean and compare the morphology of 3D objects. [12][13][14][15] For instance, Inoue et al 12 examined the left-right differences in mandibular ramus morphology using computed tomography (CT) data, whereas Suzuki et al 14 examined sex differences in the mandible.…”

Sex determination in domestic rock pigeons (Columba livia) using radiographic morphometry

“…Radiographic morphometry is a widely used research method for sex determination in humans (Suzuki et al, 2020; Uzuner et al, 2016) and domestic mammals (Gündemir et al, 2021) but has not yet been reported in poultry.…”