Datasets and Analysis of the metric and non-metric parameters of the mandible

<b>Background</b>Mandible is the hardest and most durable bone of the skull exhibiting high degree of sexual dimorphism. This characteristic feature of mandible helps sex and age determination in medicolegal cases. Cranium and mandible are the most found bones at crime scenes. Of these, the mandible is more resistant to postmortem damage. Mandibles are frequently used in gender determination, as they are compact, least destructible, and have high strength. It shows sexual dimorphism because size, shape, and masticatory forces exerted on the mandible are different in males and females.Although the existing literature does address sexual dimorphism of human mandibles, comparison of metric and non-metric traits and finding out the best traits to identify the gender are rarely addressed. Therefore, in the present study an attempt is made to observe the sexual dimorphism by both nonmetric and metric methods using several parameters in dry human mandibles of South Indian origin. The authors hypothesized that the non-metric traits are better in determining sex than the metric parameters and there are certain parameters which are superior to others which can be used to determine gender accurately.<br><b>Material and methods</b>The present multicentre cross-sectional, observational study was carried out from May 2020 to April 2021. 156 Dry adult human mandibles of known gender were procured from three medical institutes of Karnataka state, South India (103 male and 53 female). The mandibles were confirmed to be of South Indian origin through the records available at the respective institute. Only adult mandibles with all the parts intact were included in the study. Paediatric and damaged mandibles were excluded from the study. Approval for the study was obtained from the institutional ethics committee of the Kasturba Medical College, Manipal (IEC 476/2019), followed by written permission from the authorities of the other two institutes. The mandibles were subjected to non-metric observations and metric measurements.We took 15 metric and 12 nonmetric parameters into consideration. The nonmetric parameters were considered based on the study by Hu et al. We first numbered all the mandibles and observed for parameters denoted ‘N’.We used digital callipers to measure the metric parameters, which are denoted ‘M’. Length, condylar ramus height and the gonial angle were measured using a Goniometer. Some metric parameters were single, and others were calculated separately for the right and left sides (two-sided).Two authors observed and measured the same parameters together and came to a consensus before considering the item. The third author considered any difference of opinion in the observations between the two authors. To address intra-observer variability, the same author measured the metric parameters again on ten randomly chosen mandibles. To address inter-observer variability, the third author measured the same parameters using ten randomly chosen mandibles.<b>Data analysis</b>Using descriptive statistics, mean and standard deviation were calculated, and frequencies were measured. Chronbach’s alpha was calculated for the observer variability. Mann Whitney U test was used to compare the means of each variable between male and female mandibles. The Chi-square test was used to calculate the association between the variables. Furthermore, logistic regression analysis was applied, and Odd’s ratio was calculated to predict the gender probability considering the gender metric and non-metric parameters. The data analysis was carried out using SPSS software version 21.