A Novel Method for Assessing Enamel Thickness Distribution in the Anterior Dentition as a Signal for Gouging and Other Extractive Foraging Behaviors in Gummivorous Mammals

Reconstructing the dietary habits and trophic positions of the Longipterygidae (Aves: Enantiornithes) using neontological and comparative morphological methods

The Longipterygidae are a unique clade among the enantiornithines in that they exhibit elongate rostra (≥60% total skull length) with dentition restricted to the distal tip of the rostrum, and pedal morphologies suited for an arboreal lifestyle (as in other enantiornithines). This suite of features has made interpretations of this group’s diet and ecology difficult to determine due to the lack of analogous taxa that exhibit similar morphologies together. Many extant bird groups exhibit rostral elongation, which is associated with several disparate ecologies and diets (e.g., aerial insectivory, piscivory, terrestrial carnivory). Thus, the presence of rostral elongation in the Longipterygidae only somewhat refines trophic predictions of this clade. Anatomical morphologies do not function singularly but as part of a whole and thus, any dietary or ecological hypothesis regarding this clade must also consider other features such as their unique dentition. The only extant group of dentulous volant tetrapods are the chiropterans, in which tooth morphology and enamel thickness vary depending upon food preference. Drawing inferences from both avian bill proportions and variations in the dental morphology of extinct and extant taxa, we provide quantitative data to support the hypothesis that the Longipterygidae were animalivorous, with greater support for insectivory.

Dental macrowear, diet, and anterior tooth use in Colobus polykomos and Piliocolobus badius

Two similarly-sized colobine species living sympatrically in the Ivory Coast's Taï Forest that differ in both diet and oral processing behavior provide an opportunity to explore the strength of associations between feeding behavior and dental wear patterns. Here we test the hypothesis that vigorous processing of tough, hard Pentaclethra macrophylla pods by Colobus polykomos manifests in greater anterior tooth wear relative to that observed in Piliocolobus badius, which does not exploit this resource. We assessed levels of anterior tooth wear in a sample of 160 upper incisors and 131 lower incisors from 18 adult Colobus polykomos and 62 adult Piliocolobus badius naturally deceased individuals from Taï National Park. We operationalized tooth wear by dividing the area of exposed dentin by total occlusal crown area. To assess relative degrees of incisor wear, we regressed incisor wear against molar wear (sample = 105 upper molars, 135 lower molars) for the pooled Colobus polykomos and Piliocolobus badius wear data and compared the number of individuals from each species that fell above and below the pooled regression curve for each model using Chi-square tests of independence and odds ratios. Under our hypothesis, we would expect more Colobus polykomos points above the pooled regression curve than Piliocolobus badius, indicating higher incisor wear relative to molar wear in Colobus polykomos. Nine of sixteen interspecific comparisons demonstrated this predicted pattern; however, none of the Chi-square tests or odds ratios were significant, indicating no difference between Colobus polykomos and Piliocolobusbadius incisor wear relative to molar wear. The absence of significant differences in incisor wear relative to molar wear highlights the challenge of identifying idiosyncratic feeding behavior in fossil taxa and the necessity for continued exploration of the relationship between diet and macrowear.

Enamel Remineralization Competence of a Novel Fluoride-Incorporated Bioactive Glass Toothpaste-A Surface Micro-Hardness, Profilometric, and Micro-Computed Tomographic Analysis

This study aimed to analyze the enamel remineralization efficacy of a novel fluoridated bioactive glass (F-BG) toothpaste compared to a standard fluoride toothpaste. Seventy-two enamel blocks (N = 72) were divided into groups of twenty-four blocks according to the toothpaste exposure—group 1: brushed with distilled water, group 2: brushed with fluoride toothpaste (Colgate^TM), and group 3: brushed with F-BG toothpaste (BioMinF^TM). Pre-brushing, enamel blocks were demineralized using 6 wt.% citric acid (pH = 2.4). Tooth brushing was performed using a mixture of respective toothpaste and artificial saliva (AS), and each enamel block received 5000 linear strokes. The samples were assessed for surface micro-hardness (to estimate Vickers hardness number, VHN), surface roughness (Ra), and volume loss/gain using micro-computed tomography (micro-CT). The highest increase in the VHN was noticed for group 3 (117.81) followed by group 2 (61.13), and all the intragroup comparisons were statistically significant (p < 0.05). Demineralization increased the Ra values, and a decrease was observed post-remineralization for all the groups. The maximum Ra decrease was observed for group 3 (−223.2 nm) followed by group 2 (−55.6 nm), and all the intragroup comparisons were again statistically significant (p < 0.05). Micro-CT investigation revealed that the enamel volume decreased after demineralization and increased after remineralization among all groups. The F-BG toothpaste showed greater enamel surface micro-hardness (increased VHN), smoother surface (low roughness), and better volume restoration (remineralization) in comparison to the fluoride toothpaste.