Use of the frontal sinus to evaluate sexual dimorphism in a Brazilian sample

The frontal sinuses are commonly used in sexual estimation due to the considerable variation in size, shape and number. Previous studies have shown average accuracy measuring frontal sinus area, height and width; however, authors have associated such measurements with the frontal sinus index, obtaining better results. Therefore, the aim of the present study was to evaluate sexual dimorphism of the frontal sinus in Brazilian adults. The sample consisted of 255 lateral cephalometric radiographs of subjects between 20 and 40 years of age, 132 females and 123 males. Based on the methodology of Luo et al. (2018), the area (S) and the maximum frontal sinus height and width (AB and EF, respectively) were measured using computer-aided design software; and the ratio between AB and EF was taken as the frontal sinus index (R). The discriminant function developed by the authors was then applied to evaluate sexual dimorphism in the Brazilian population. Descriptive statistics were performed for the variables according to gender, as well as Student's t-test and the Mann-Whitney test to see if there was a difference between the variables. A new discriminant formula was calculated with the study data and machine learning techniques, neural networks and decision trees, were used to improve the prediction of sex. The variables showed significant differences in relation to gender, and with the exception of R, where the male mean was 2.00 and the female mean was 2.40, all the means were higher for males. The original formula of the study had low accuracy, with a level of accuracy of only 8.33% for females. However, the formula calculated for Brazilians presented an accuracy of 70.20%; of the machine learning techniques, only the neural network presented a higher value than the one already obtained, of 73.30%. In conclusion, the new formula showed an accuracy of 70.20% and can be applied as an auxiliary method in the assessment of frontal sinus sexual dimorphism in Brazilian adults.