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ABSTRACT ObjectivesOdontoblasts lining the pulp cavity deposit dentine throughout life, meaning the volume of the pulp cavity decreases with age. Primates with more abrasive diets have relatively higher molar pulp volume in their unworn molars than those with less abrasive diets. We propose that species with more abrasive diets deposit additional dentine across their lifespans to help resist wear and extend the effective lifespan of their molars. Whereas both age and wear affect dentine deposition, it is unknown which of these two variables has the greater impact. Materials and MethodsWe measured pulp volume and calculated wear from micro‐CT scans of lower first molars of captive‐bredMacaca fascicularis(n = 13) of known age. We used reduced major axis regressions (alpha = 0.05) to test if age or wear was a better predictor of pulp volume. ResultsBoth variables have a significant negative relationship with pulp volume (age:p = 0.004,R² = 0.546; wear:p < 0.001,R² = 0.890). A mixed linear model of pulp volume against wear as main effect and age as covariant had a non‐significant interaction effect (p = 0.078) and confirmed that both age (p = 0.030) and wear (p = 0.004) are significantly negatively correlated with pulp volume. DiscussionResults suggest that whereas pulp volume decreases with age, wear is more strongly correlated with decreasing pulp volume. These findings have implications for interpreting odontoblast activity in response to sensory feedback and the relationship between pulp volume and diet. These results also have implications for using molar pulp volume to estimate age at death in humans. 

Abstract ObjectivesMaintaining effective and efficient occlusal morphology presents adaptive challenges for mammals, particularly because mastication produces interactions with foods and other materials that alters the geometry of occlusal surfaces through macrowear and/or catastrophic failure (i.e. “chipping”). Altered occlusal morphologies are often less effective for masticating materials of given diet—but not always—some species exhibit dental sculpting, meaning their dentitions are set up to harness macrowear to hone their occlusal surfaces into more effective morphologies (i.e. secondary morphologies). Here we show that dental sculpting is present in the folivorousPresbytis rubicundaof Borneo. MethodsThirty‐one undamaged lower second molars ofP.rubicundaexhibiting various stages of macroscopic wear were micro‐CT scanned and processed into digital surfaces. The surfaces were measured for convex Dirichlet normal energy (vDNE, a measure of surface sharpness), and degree of surface wear. Regression analyses compared surface sharpness with several measures of wear to test for the presence and magnitude of dental sculpting. ResultsPositive correlations between the wear proxies and vDNE reveal thatP.rubicundawear in such a way as to become sharper, and therefore more effective chewing surfaces by exposing enamel‐dentine junctions on their occlusal surfaces and then honing these junctions into sharpened edges. Compared to another primate folivore in which increasing surface sharpness with macrowear has been demonstrated (i.e.,Alouatta palliata), the worn surfaces are similarly sharp, but the dental sculpting process appears to be different. DiscussionThe results presented here suggest that not only do some primates exhibit dental sculpting and the attendant secondary morphology, but that there appear to be multiple different morphological configurations that can achieve this result.P.rubicundahas thicker enamel and a more stereotyped wear pattern thanA.palliata, although both show positive correlations of occlusal surface sharpness (vDNE) with various wear proxies. These findings shed light on the varied approaches for the maintenance of effective and efficient occlusal surfaces in primates.