Testing functional and morphological interpretations of enamel thickness along the deciduous tooth row in human children

Abstract

The significance of a gradient in enamel thickness along the human permanent molar row has been debated in the literature. Some attribute increased enamel thickness from first to third molars to greater bite force during chewing. Others argue that thicker third molar enamel relates to a smaller crown size facilitated by a reduced dentin component. Thus, differences in morphology, not function, explains enamel thickness. This study draws on these different interpretive models to assess enamel thickness along the entire human deciduous tooth row. Average enamel thickness (AET), the area and proportion of crown enamel and dentin, and a crown size proxy are calculated for incisors, canines, and molars. Allometric scaling relationships are assessed within each tooth class, and then comparisons are undertaken along the row. Generally, AET was correlated with crown size and scaled with isometry, except for second molars which scaled with positive allometry. Mean AET increased along the row and was greater on molars, where bite forces are reported to be higher. Second molars combined the largest crown size with the thickest enamel and the smallest proportion of dentin, which is consistent with a reduction in the potential for cusp fracture under high bite forces. Resistance to wear may also account for some enamel thickness variation between tooth classes. Dental reduction did not explain the trend in AET from central to lateral incisors, or from first to second molars. The gradient in AET along the deciduous tooth row is partly consistent with a functional interpretation of enamel thickness.

Intra‐ and interspecific variation in macaque molar enamel thickness

“…This is reflective of tooth size patterns, as macaque maxillary molars have larger buccal-lingual dimensions than do mandibular molars (Swindler, 2002). Considerable debate exists about the biomechanical significance of this pattern in primates, which is explored further in Schwartz (2000), Grine (2005), Grine et al (2005) and Mahoney (2010Mahoney ( , 2013. Our data do not support the idea that increasing enamel thickness in posterior molars is due to reduction in tooth size (Grine, 2005;Grine et al, 2005), as macaques show increases in both enamel thickness and tooth size from first to third molars.…”

“…Recent work has reinvigorated functional explanations for primate enamel thickness variation (Vogel et al, 2008;Constantino et al, 2009;Rabenold and Pearson, 2011;McGraw et al, 2012;Mahoney, 2013;Pampush et al, 2013). A number of studies posit a relationship between enamel thickness and the mechanics of tooth wear or fracturing, while others assess the relationship between enamel thickness and diet (preferred and/or fallback foods) (reviewed in Smith et al, 2012b).…”

Shear bond strength of different types of adhesive systems to dentin and enamel of deciduous teeth in vitro

“…Yet, the present study additionally examined the adhesive's potential to bond to primary enamel. In case of front teeth restorations due to trauma or shallow smooth-caries defects, the proportion of enamel has a stronger impact on the cavity design [38]. The present investigation illustrates that this clearly attributes to the suitability of the adhesive agent.…”

Biorhythms, deciduous enamel thickness, and primary bone growth: a test of the Havers‐Halberg Oscillation hypothesis

“…; Brown et al. ; Mahoney, ). However, M1 size is only weakly associated with adult height (Garn et al.…”