Non-Carious Cervical Lesions in Wild Primates: Implications for Understanding Toothpick Grooves and Abfraction...

In clinical settings, non-carious cervical lesions (NCCLs) are often linked to abrasion, erosion, abfraction, or a combination of these factors. In archaeological and paleontological remains, the most common NCCL is the "toothpick groove," yet little is known about the occurrence of these and other NCCLs in wild non-human primates.

Here, we examine 531 individuals from 27 wild extant and extinct anthropoid primate taxa for NCCLs. Macroscopic examinations were followed by microwear and tissue-loss analyses using multiple imaging techniques, including stereoscopic microscopy, confocal laser, handheld digital microscopy, and 3D tissue loss analysis.

NCCLs were identified in 21 individuals, indicating a prevalence of 4% within the sample. The distribution of NCCLs was uneven, with multiple cases concentrated in certain taxa and populations, but they are identified in all major groupings (e.g., Platyrrhini, Cercopithecidae, Hominoidea). Two distinct lesion types were identified: (1) localized U-shaped lesions with internal parallel striations, indicative of regular contact with abrasive materials (i.e., attrition or abrasion); and (2) smooth, shallow lesions characterized by tissue loss along the recessed gum line, indicative of a multifactorial process that may involve acid erosion.

Several attrition/abrasion NCCLs resembled or have characteristic features of "toothpick grooves" known from hominin samples, suggesting the need for further comparative analyses between human and non-human primates. The absence of abfraction lesions supports the view that abfraction may be related to contemporary human behaviors. These findings emphasize the value of non-human primate data for interpreting NCCLs in both contemporary and ancient human populations.