Sexual dimorphism of the first deciduous molar: A geometric morphometric approach

Estimating the sex of immature skeletal remains is important when reconstructing the biological profile of unknown individuals in anthropological practice. Teeth have a distinct importance as they are the most frequently recovered physical elements of an individual. They persist after death due to their hardness and resistance to postmortem insults. The aim of this study was to analyse the sexual dimorphism of the occlusal surface of the first deciduous molar using geometric morphometric techniques. This study evaluated 38 first maxillary deciduous molars (21 males, 17 females) and 30 first mandibular deciduous molars (15 males, 15 females) from the Granada osteological collection of identified subadults (Granada, Spain). The landmark and semilandmark coordinates were analysed by principal components analysis, canonical variate analysis and discriminant analysis. Only the first maxillary deciduous molar showed a significant sexual dimorphism, with cross-validation values for shape variables of 93.23% for males and 83.17% for females, and 100% for males and 87.50% for females when both shape and size variables were considered. Despite there being acceptable cross-validation classification for the first mandibular deciduous molar (82.35% for males and 92.31% for females for shape variables and 82.35% for males and 92.31% for females for shape and size variables), no significant differences indicating sexual dimorphism were identified. The results show that the first upper deciduous molar can assist in sex estimation, and that geometric morphometric analysis is a suitable technique to answer questions related to shape that cannot be observed with the naked eye.