Dentin horn angle and enamel thickness interactively control tooth resilience and bite force.

Area of Science:

• Paleoanthropology
• Biomechanics
• Evolutionary Biology

Background:

• Fossil teeth are crucial for understanding hominin evolution, feeding ecology, and adaptation.
• Current methods for analyzing fossil teeth, such as bite force analysis and morphogenetics, have limitations in quantitative correlation with behavior.
• The relationship between anatomical features and functional capabilities in fossil teeth remains an area for refinement.

Purpose of the Study:

• To identify and quantify a novel developmental parameter in tooth structure.
• To establish a direct, mechanistic link between tooth anatomy and bite force.
• To develop a new method for estimating bite force in fossil hominins.

Main Methods:

• Histological analysis of human premolar and molar teeth sections.
• Examination of cuspal enamel thickness (d_c) and dentin horn angle (φ).
• Analysis of bending stress at the horn apex under axial cuspal loading.

Main Results:

• A unique and conclusive correlation was found between d_c and φ.
• This relationship generates a constant force causing cusp fracture (P_F), a measure of tooth resilience.
• The d_c vs. φ relationship in fossil hominin teeth is consistent with modern humans, with varying P_F.

Conclusions:

• The d_c vs. φ relationship provides a novel, development-based approach to understanding tooth resilience and function.
• Scaling bite force (BF) with P_F allows for direct, non-destructive estimation of BF from fossil teeth using micro-computed tomography scans.
• This study offers a new analytical framework for examining evolutionary processes in hominins through fossil tooth analysis.