Dental caries in South African fossil hominins

Dental caries in living and extinct strepsirrhines with insights into diet

Dental caries is one of the most common diseases afflicting modern humans and occurs in both living and extinct non-human primates, as well as other mammalian species. Compared to other primates, less is known about the etiology or frequency of caries among the Strepsirrhini. Given the link between caries and diet, caries frequency may be informative about the dietary ecology of a given animal. Understanding rates of caries in wild populations is also critical to assessing dental health in captive populations. Here, we examine caries frequency in a sample of 36 extant strepsirrhine species (n = 316 individuals) using odontological collections of wild-, non-captive animals housed at the American Museum of Natural History by counting the number of specimens characterized by the disease. Additionally, in the context of studying caries lesions in strepsirrhines, case studies were also conducted to test if similar lesions were found in their fossil relatives. In particular, two fossil strepsirrhine species were analyzed: the earliest Late Eocene Karanisia clarki, and the subfossil lemur Megaladapis madagascariensis. Our results suggest that caries affects 13.92% of the extant individuals we examined. The frugivorous and folivorous taxa were characterized by the highest overall frequency of caries, whereas the insectivores, gummivores, and omnivores had much lower caries frequencies. Our results suggest that caries may be common among wild populations of strepsirrhines, and in fact is more prevalent than in many catarrhines and platyrrhines. These findings have important implications for understanding caries, diet, and health in living and fossil taxa.

Evaluation of a Decision Support System Developed with Deep Learning Approach for Detecting Dental Caries with Cone-Beam Computed Tomography Imaging

This study aims to investigate the effect of using an artificial intelligence (AI) system (Diagnocat, Inc., San Francisco, CA, USA) for caries detection by comparing cone-beam computed tomography (CBCT) evaluation results with and without the software. 500 CBCT volumes are scored by three dentomaxillofacial radiologists for the presence of caries separately on a five-point confidence scale without and with the aid of the AI system. After visual evaluation, the deep convolutional neural network (CNN) model generated a radiological report and observers scored again using AI interface. The ground truth was determined by a hybrid approach. Intra- and inter-observer agreements are evaluated with sensitivity, specificity, accuracy, and kappa statistics. A total of 6008 surfaces are determined as 'presence of caries' and 13,928 surfaces are determined as 'absence of caries' for ground truth. The area under the ROC curve of observer 1, 2, and 3 are found to be 0.855/0.920, 0.863/0.917, and 0.747/0.903, respectively (unaided/aided). Fleiss Kappa coefficients are changed from 0.325 to 0.468, and the best accuracy (0.939) is achieved with the aided results. The radiographic evaluations performed with aid of the AI system are found to be more compatible and accurate than unaided evaluations in the detection of dental caries with CBCT images.

The largest and earliest known sample of dental caries in an extinct mammal (Mammalia, Euarchonta, Microsyops latidens) and its ecological implications

Dental cavities or caries is a common disease among modern humans, affecting almost every adult. Caries frequency has been used to study dietary change in humans over time, based on an inferred tie between the incidence of caries and a carbohydrate-rich diet. However, the disease is not unique to our species. Among non-human primates, there is also variation in caries frequency associated with diet, suggesting that this metric may provide a mechanism for studying diet in broader contexts, and across geological time. To date, very few studies have examined caries among fossil mammals, and none have done so among Eocene mammals. Here, we present our analysis of the largest sample to date of fossil caries in a single extinct mammal species, Microsyops latidens, a stem primate from the early Eocene, which is known from over a thousand specimens from the Southern Bighorn Basin of Wyoming (n = 1030). Our results show that Microsyops latidens is characterized by a high prevalence of dental caries (7.48% of individuals), with notable variation through time, reaching 17.24% of individuals from a particular interval. This interval is also associated with a change in overall dental form, as quantified by dental topographic analysis, which measures functional aspects of the chewing surface of teeth. These observations suggest that this species experienced a shift in their diet to include more fruit or other sugar rich-foods for a short period. Our analysis, therefore, suggests that the diet of M. latidens fluctuated over time, as well as providing a framework for assessing caries in other fossil taxa.