What do rates of deposition of dental cementum tell us? Functional and evolutionary hypotheses in red deer

Cementum is a bone connective tissue that provides a flexible attachment for the tooth to the alveolar bone in many mammalian species. It does not undergo continuous remodelling, unlike non-dental bone, which combined with its growth pattern of seasonal layering makes this tissue uniquely suitable as a proxy for tracking changes in body repair investment throughout an animal´s life. We tested functional and sexual selection hypotheses on the rate of cementum deposition related to the highly polygynous mating strategy of red deer. We used a sample of 156 first lower molars from wild Scottish red deer of known age between 1 and 17 years old, approximately balanced by sex and age class. Cementum deposition on the inter-radicular pad increased with age at a constant average rate of 0.26 mm per year, with no significant differences between sexes. Cementum deposition was independent of (i) tooth wear, other than that associated with age, and (ii) enamel and dentine micro-hardness. The results partially supported the hypothesis that the main function of cementum is the repositioning of the tooth to maintain opposing teeth in occlusion. However, teeth that had more wear or males´ teeth that had faster rates of tooth wear than those of females did not present the expected higher rates of cementum deposition.
The study was supported by projects Ministerio de Economia, Industria y Competitividad, Gobierno de España RTC-2016-5327-2 (Dr. T Landete-Castillejos); Junta de Comunidades de Castilla-La Mancha SBPLY/19/180501/000115 (Dr. MP Serrano). The red deer study on the Isle of Rum National Nature Reserve takes place with the support of the UK Natural Environment Research Council and Scottish Natural Heritage. The European Union Lifelong learning programme (Leonardo da Vinci) for supporting the postgraduate students who collaborated in this study.