# Maxillary first premolar shape (and not size) as an indicator of sexual dimorphism: A 2D geomorphometric study

## TL;DR

This study uses 2D geometric analysis to show that the shape of maxillary first premolars can help determine sex, with high accuracy.

## Contribution

The study introduces 2D geomorphometric analysis of maxillary first premolar shape as a novel method for identifying sexual dimorphism.

## Key findings

- Centroid sizes were similar between genders (p = 0.606), indicating no significant size difference.
- Shape analysis showed significant sexual dimorphism (F value of 1.4; p = 0.0624).
- Discriminant function analysis correctly classified sex with 90.91% accuracy.

## Abstract

Introduction

The primary aim of the study is to evaluate the morphological form of the maxillary first premolar using 2D geomorphometry and evaluate the sexually dimorphic characteristics.

Methods

The present study was carried out on  standardized photographs of right Maxillary first premolar from 55 dental casts (33 male and 22 females). Nineteen landmarks (based on geometric and anatomic evidence) were marked on the tooth using TPSdig software and analysed using Morpho J applying procrustes analysis and discriminant function analysis

Results

The results showed similar centroid sizes between gender (p = 0.606). Procrustes ANOVA for shape analysis showed a greater dimorphism between sexs (f value of 1.4; p value=0.0624).  Discriminant function analysis based on the procrustes coordinates showed an overall accuracy of 90.91 % in classifying sex based on the landmark coordinates with correct classification of  20/22 (90.99%) females and 30/33 (90.91) males.

Conclusion

Shape of the tooth can be measured objectively using geometric morphometric methods which can be utilized to identify the sex of an individual. Enamel covering the crown of the teeth is biologically stable resisting climatic, physical and chemical insults. The enamel is derived from ectoderm and once formed does not change during the life. The tooth’s structure and shape are determined by the sex chromosomes, which is well represented as sexual dimorphism. The study evaluates the occlusal and contact area morphology of premolars. These are important parameters considered during restorative treatment, functional rehabilitation and forensic investigations.