A novel system for classifying tooth root phenotypes.

Jason Gellis,Robert Foley

doi:10.1371/journal.pone.0251953

Abstract

Human root and canal number and morphology are highly variable, and internal root canal form and count does not necessarily co-vary directly with external morphology. While several typologies and classifications have been developed to address individual components of teeth, there is a need for a comprehensive system, that captures internal and external root features across all teeth. Using CT scans, the external and internal root morphologies of a global sample of humans are analysed (n = 945). From this analysis a method of classification that captures external and internal root morphology in a way that is intuitive, reproducible, and defines the human phenotypic set is developed. Results provide a robust definition of modern human tooth root phenotypic diversity. The method is modular in nature, allowing for incorporation of past and future classification systems. Additionally, it provides a basis for analysing hominin root morphology in evolutionary, ecological, genetic, and developmental contexts.

Highlights

Human dental morphology is a diverse collection of non-metric traits: cusp numbers, fissure and ridge patterns, root number and shape, and even congenital absence
Dental trait scoring systems are overwhelmingly focused on tooth crown morphology, with less attention paid to roots
CT scans of 5,970 teeth (Table 2) of 945 individuals from a global sample (S1 and S2 Tables) were analysed to identify morphologies which are useful for classifying the tooth root complex of modern human teeth

Summary

Introduction

Human dental morphology is a diverse collection of non-metric traits: cusp numbers, fissure and ridge patterns, root number and shape, and even congenital absence. Recording systems, such as the widely utilized Arizona State University Dental Anthropology System (ASUDAS) [1, 2], have been developed to catalogue these traits and their variants under a standardized scoring procedure; and to study how these variants are partitioned within and between populations. The studies discussed below have addressed root number, canal number, external root morphology, canal morphology, and canal configuration independently They comprise only parts of the tooth root complex, and provide a basis for a comprehensive phenotype system. In contrast to the maxilla, the most frequent form of mandibular P3s and P4s is single rooted; though P3s are occasionally two-rooted or, more rarely, thee rooted [29,30,31]

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Conclusion