Toothnroll: An R Package for Landmarking, Measuring, and Mapping Dental Tissues of Hominoid Anterior Teeth

Objectives

We present Toothnroll, a new R package for landmarking, measuring and mapping dental tissues of hominoid anterior teeth.

Methods

The required inputs include 3D meshes of enamel, dentine, and pulp, a drawn cervical outline, and six landmarks along the cervical line, root apex, and dentine horn tip. Toothnroll is customizable and includes an R function (ToothAlignment) for model alignment. The ToothCore and ToothShape functions slice the dental meshes and extract coordinates of evenly spaced semilandmarks from the aligned 3D dental meshes. These coordinates are used to unroll tooth tissues to create 2D morphometric maps, using the Tooth2Dmap function. ToothVolumes calculates crown and root tissue volumes. Application of Toothnroll to post-canine teeth and inherent methodological limitations are addressed.

Results

We apply Toothnroll to a modern human central incisor to demonstrate its utility in extracting linear, volumetric, and topographic dental measurements. To evaluate its applicability in paleobiology, we conduct two case studies: (1) the unrolling of the entire anterior dentition of a modern human individual and (2) the comparison of dental tissue measurements and topographic distribution between male and female human upper canines. Toothnroll is also suitable for analyzing anterior dentition with varying degrees of root curvature.

Discussion

Toothnroll, a package developed in the open-source R environment, integrates key methodologies in dental anthropology. These include tooth alignment and sectioning, linear, and volumetric dental measurements, and morphometric mapping of enamel and dentine. Using Toothnroll could significantly enhance our understanding of the evolutionary and functional factors affecting endostructural organization of anterior dentition.