Isidora Christopoulou – Francesca Miotti Award Young Speaker’s Contest

BACKGROUND: The chin is one of the most distinctive anatomical traits of modern humans. It is found only in our species, Homo sapiens, and its exact function still remains unknown. Comprehensive and quantitative evaluation of chin shape and size is required for assessment of sexual dimorphism and age-related effects.

AIM: The present study aims to develop a new method to examine chin morphology.

MATERIALS AND METHODS: Electronic databases were searched for methods of evaluating chin morphology. Two-dimensional methods focus on the lateral cephalogram, whereas 3D methods use computed-tomography (CT) images or skeletal specimens. Most studies have used linear measurements between anatomic landmarks and a few have used geometric morphometric (GM) methods, again based on a small number of landmarks. We decided on a 3D GM method, but including a large number of sliding semilandmarks, in order to capture anatomy that might have been missed in previous studies, such as the mental tubercles and the digastric fossae. One hundred CBCT images of patients of both sexes and covering a wide age range were used. The images were segmented to create mesh surfaces of the exterior mandibular anatomy.

RESULTS: The mental region was defined as the area between the mental foramina. A 3D template of hundreds of dense surface landmarks and salient curves was created to capture the morphology of this area. The majority of landmarks are semilandmarks, allowed to slide along curves and surfaces towards minimizing the bending energy. After sliding, landmarks and semilandmarks can be treated as homologous points between specimens and superimposed by Procrustes alignment. Principal components analysis (PCA) allows for extracting the most prevalent morphological patterns. Differences between sexes and age groups can be investigated with permutation tests and visualized with Procrustes superimposition.

CONCLUSIONS: In this study, we suggest a new method to address an old problem in anthropology: chin morphology. By utilizing geometric morphometric methods, researchers can obtain a detailed model of chin morphology, exploring its function, possible variations attributed to gender or age and potential implications in fields such as forensics and evolutionary biology.