The Evolutionary Paradox of Tooth Wear: Simply Destruction or Inevitable Adaptation?

Abstract

Over the last century, humans from industrialized societies have witnessed a radical increase in some dental diseases. A severe problem concerns the loss of dental materials (enamel and dentine) at the buccal cervical region of the tooth. This “modern-day” pathology, called non-carious cervical lesions (NCCLs), is ubiquitous and worldwide spread, but is very sporadic in modern humans from pre-industrialized societies. Scholars believe that several factors are involved, but the real dynamics behind this pathology are far from being understood. Here we use an engineering approach, finite element analysis (FEA), to suggest that the lack of dental wear, characteristic of industrialized societies, might be a major factor leading to NCCLs. Occlusal loads were applied to high resolution finite element models of lower second premolars (P2) to demonstrate that slightly worn P2s envisage high tensile stresses in the buccal cervical region, but when worn down artificially in the laboratory the pattern of stress distribution changes and the tensile stresses decrease, matching the results obtained in naturally worn P2s. In the modern industrialized world, individuals at advanced ages show very moderate dental wear when compared to past societies, and teeth are exposed to high tensile stresses at the buccal cervical region for decades longer. This is the most likely mechanism explaining enamel loss in the cervical region, and may favor the activity of other disruptive processes such as biocorrosion. Because of the lack of dental abrasion, our masticatory apparatus faces new challenges that can only be understood in an evolutionary perspective.

Mandibular morphology in two archaeological human skeletal samples from northwest Europe with different masticatory regimes

“…The rate of dental wear does not appear to change throughout the period of use of the Wharram Percy burial ground (Mays, 2007), and typifies that in Mediaeval and earlier populations in Britain (Brothwell, 1981;Miles, 1963). The Zwolle population shows greater wear than seen in modern Europeans, where dentine exposure is rare (Benazzi et al, 2013;Sengupta et al, 1999). This suggests that the difference in dietary material properties between Zwolle and Wharram Percy is not as great as between most ancient populations and modern Europeans.…”

The physiological linkage between molar inclination and dental macrowear pattern

“…Tooth wear is a physiological and adaptive phenomenon of dental tissue loss (Benazzi et al, 2013). In anatomically modern humans, numerous factors contribute to creating and modifying wear on the occlusal surface of teeth.…”

Is the deciduous/permanent molar enamel thickness ratio a taxon-specific indicator in extant and extinct hominids?

“…In this sense, our study attempts to do this for the first time. While occlusal enamel topography is more directly informative in terms of functional activity and adaptive responses (e.g., Guy et al, 2013;Kono, 2004;Kono and Suwa, 2008;Olejniczak et al, 2008b), lateral enamel thickness is also involved in dissipating occlusally-related stresses (Benazzi et al, 2013a(Benazzi et al, , 2013b. Lateral enamel also resists wear, tooth height loss and maintains interproximal tooth-tooth contacts during the late stages of tooth wear after dentine exposure over the occlusal surface.…”