A Geometric Morphometric Study on the Rat Mandible

Abstract

The aim of the study was to investigate the shape of the mandible in Wistar albino rats using the geometric morphometric method. However, ‘Is the shape of the mandible different in rats depending on gender?’ the question formed the hypothesis of the study. For this purpose, a total of 52 rat mandibles, 31 female and 21 male rats, were used in the study. The right mandible was photographed from the lateral aspect. A total of 16 landmarks were marked on the photographs. In the study, principal component analysis (PCA) and discriminant function analysis were performed with the MorphoJ program. As a result of the study, 28 principal components (PC) were calculated. The values of variance of the first three PC were explained as 54.887% of the total shape difference. Principal component analysis showed the shape changes were more in mandibular ramus. However, no shape change was observed, especially the most top point of the ventral edge of the mandible at the rostral side. In the graph of PCA, the groups according to gender did not show a clear distinction. According to cross-validation scores, 24 females and 17 males showed correct grouping. In the study, the shape characteristics of the rat mandible from the lateral aspect were revealed. However, it was determined that the most difference in shape by gender was in the condylar process, coronoid process and angular process. As a result, despite the formal differences, when all the data were evaluated, it was concluded that gender discrimination could be made mostly (77% female, 80% male) according to shape of the rat mandible.