A probable genetic origin for pitting enamel hypoplasia on the molars of Paranthropus robustus

We report the frequencies of linear enamel hypoplasia (LEH) and, specifically, pitting enamel hypoplasia (PEH) defects in the teeth of Paranthropus robustus, for comparison with four other South African hominin species and three extant nonhuman primate species. Unlike LEH, the lesser known PEH is characterized by multiple circular depression defects across a tooth crown and is often difficult to interpret in terms of developmental timing and etiology. Teeth in all samples were examined macroscopically with type, position and number of defects recorded. Frequencies of teeth with LEH vary among hominin species, but the differences in PEH are considerable. That is, P. robustus has much higher rates of pitting defects, with 47% of deciduous teeth and 14% of permanent teeth affected, relative to 6.7% and 4.3%, respectively, for all other hominin teeth combined; none of the extant primate samples evidences comparable rates. The defects on P. robustus molars are unlike those in other species, with entire crowns often covered in small circular depressions. The PEH is most consistent with modern human examples of amelogenesis imperfecta. Additionally, the defects are: 1) not found on anterior teeth, 2) uniform in shape and size, and 3) similar in appearance/severity on all molars. Therefore, this form of PEH may have been a side effect of selection on another trait that shares the same coding gene(s), i.e., these defects have a genetic origin. We discuss a possible scenario that may explain how this form of PEH evolved to become so common in the Paranthropus genu

Behavioral inferences from the high levels of dental chipping in Homo naledi

Objectives: A variety of mechanical processes can result in ante-mortem dental chipping. In this study, chipping data in the teeth of Homo naledi are compared with those of other pertinent dental samples to give insight into their etiology. Materials and Methods: Permanent teeth with complete crowns evidencing occlusal wear were examined macroscopically. The location, number, and severity of fractures were recorded and compared to those found in samples of two other South African fossil hominin species, as well as in samples of non-human primates (n= 3) and recent humans (n= 7). Results: With 44% of teeth affected, Homo naledi exhibits far higher rates of chipping than the other fossil hominin samples. Specifically, 50% of posterior teeth and 31% of anterior teeth display at least one chip. The maxillary teeth are more affected than the mandibular teeth (45% vs. 43%, respectively), 73% of molar chipping occurs on interproximal surfaces, and right teeth are more often affected than left teeth (50% vs. 38%). Discussion: Results indicate that the teeth of H. naledi were exposed to acute trauma on a regular basis. Because interproximal areas are more affected than buccal, and posterior teeth more than anterior, it is unlikely that non-masticatory cultural behavior was the cause. A diet containing hard and resistant food, or contaminants such as grit, is more likely. The small chip size, as well as steep occlusal wear and cupped dentine on some molars is supportive of the latter possibility. This pattern of chipping suggests H. naledi differed considerably – in terms of diet, environment, and/or specialized masticatory processing— relative to other African fossil hominins

Variation in enamel mechanical properties throughout the crown in catarrhine primates.

Enamel mechanical properties vary across molar crowns, but the relationship among mechanical properties, tooth function, and phylogeny are not well understood. Fifteen primate lower molars representing fourteen taxa (catarrhine, n = 13; platyrrhine, n = 1) were sectioned in the lingual-buccal plane through the mesial cusps. Gradients of enamel mechanical properties, specifically hardness and elastic modulus, were quantified using nanoindentation from inner (near the enamel-dentine junction), through middle, to outer enamel (near the outer enamel surface) at five positions (buccal lateral, buccal cuspal, occlusal middle, lingual cuspal, lingual lateral). Cuspal positions had higher mechanical property values than lateral positions. Middle enamel had higher mean hardness and elastic modulus values than inner and outer locations in all five crown positions. Functionally, the thicker-enameled buccal cusps of lower molars did not show evidence of increased resistance to failure; instead, lingual cusps-which show higher rates of fracture-had higher average mechanical property values, with no significant differences observed between sides. Preliminary phylogenetic results suggest there is relatively little phylogenetic signal in gradients of mechanical properties through the enamel or across the crown. There appears to be common mechanical property patterns across molar crowns in Catarrhini and potentially among primates more broadly. These results may allow more precise interpretations of dental biomechanics and processes resulting in mechanical failure of enamel in primates, such as wear and fracture. [Abstract copyright: Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Root grooves on two adjacent anterior teeth of Australopithecus africanus

Tooth root grooves and other ante-mortem dental tissue loss, not associated with caries found on or near the cementoenamel junction (CEJ), are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study, South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. The characteristics of these grooves suggest the predominant aetiology was erosive wear. In addition, they are extremely similar to clinical examples of dental erosion. These are the oldest hominin examples of non-carious cervical lesions and the first described in a genus other than Homo. Further, the lesions suggest that this individual regularly processed and consumed acidic food items. © 2018 Elsevier Inc

Recording and interpreting enamel hypoplasia in samples from archaeological and palaeoanthropological contexts

Enamel hypoplasia is often split into several macroscopic categories, including pit, localised, linear and planeform defects. All types have been considered a sign of ‘non-specific stress’ during dental development in archaeological, as well as palaeoanthropological and other samples. there is growing evidence suggesting many defects may not be caused by illness or malnutrition during childhood, instead relating to trauma to the developing tooth, genetic conditions or specific environmental factors, i.e., may not be associated with ‘stress’ to the individual. In this study all types of macroscopic enamel hypoplasia were recorded, including pitting, linear, plane and localised type defects, in two extant great ape species and three fossil hominin species. The aim is to compare the characteristics and prevalence of different types of enamel hypoplasia among species and discuss potential differences in aetiology. The results show that samples have diverse prevalence’s of different kinds of defects, and pitting, linear and localised defects likely have different aetiologies. Additionally, dental characteristics (e.g., tooth morphology, developmental timing/speed and enamel structure) heavily influence the likelihood of specific types of enamel hypoplasia forming. In sum, studies that include only one type of enamel hypoplasia, or focus on one tooth type, to generate a ‘stress’ rating for a sample may miss relevant information when comparing groups. Instead, it may be beneficial to record different types of defects separately, for all teeth, and then consider how genetic, environmental and tooth property factors may influence sample differences

Severe Plane-Form Enamel Hypoplasia in a Dentition from Roman Britain

Enamel defects can provide insight into the life histories of past individuals and populations, in-cluding information on a wide range of disturbances during childhood. This study investigates a particularly severe case of plane-form enamel hypoplasia from a Roman site in Gloucester, UK. Dentine protrudes above the occlusal enamel of upper central incisors, both upper canines, the lower left canine, lower right central incisor, and all four first molars. Given the morphology and location of these defects, along with the developmental tim-ing of the affected teeth, such factors as molar-incisor hypomineralization, amelogenesis imperfecta, and congen-ital syphilis can likely be ruled out. The defects resulted from a nonspecific but severe physiological disturbance during the second year of life. Severe plane-form defects of this kind, where enamel formation has completely ceased, are extremely rare in premodern populations, and this example is one of the earliest reported cases. It has been suggested that these defects generally occur only in individuals that survived a life-threatening illness, which would explain the scarcity in the archaeological record, i.e., the afflicted individual would not have lived long enough for the defects to manifest. Comparisons with clinical examples and pathogen DNA analysis may provide further insight into the etiology of these defects.</jats:p

High frequency of dental caries and calculus in dentitions from a British medieval town

Objective Dental pathology and tooth wear data can offer valuable insights into the diet and behaviour of past populations. This study aimed to investigate the presence of dietary continuity by examining different types of dental pathology and tooth wear in a medieval sample from the United Kingdom, comparing them to earlier and later samples from the same location. Design A comprehensive examination was conducted on 41 individuals (comprising 914 permanent teeth) retrieved from the medieval cemetery of St. Owens Church in Southgate Street, Gloucester, UK. The research focused on documenting and analysing various types of dental pathology and tooth wear, such as dental caries, calculus, and tooth chipping. The frequency of these specific pathologies and wear patterns was then compared to existing literature. Additionally, non-masticatory tooth wear was also evaluated as part of the study. Results The sample exhibits high levels of carious lesions and calculus (24 % and 74 % of teeth respectively). Anterior teeth also show an elevated chipping frequency, and along with occlusal notches on the maxillary central incisors suggest teeth were regularly used for non-masticatory purposes. Conclusions Caries frequency is similar to sites from later periods and may relate to the early adoption of consuming refined carbohydrates. However, remains from the same area, but the earlier Roman period, also shows high rates of caries and calculus, suggesting a continuation of consuming certain cariogenic foods, or certain behavioural/environmental factors, may instead be responsible for these pathology and wear patterns

Dental caries in South African fossil hominins

Once considered rare in fossil hominins, caries has recently been reported in several hominin species, requiring a new assessment of this condition during human evolution. Caries prevalence and location on the teeth of South African fossil hominins were observed and compared with published data from other hominin samples. Teeth were viewed macroscopically, with lesion position and severity noted and described. For all South African fossil hominin specimens studied to date, a total of 10 carious teeth (14 lesions), including 4 described for the first time here, have been observed. These carious teeth were found in a minimum of seven individuals, including five Paranthropus robustus, one early Homo, and one Homo naledi. All 14 lesions affected posterior teeth. The results suggest cariogenic biofilms and foods may have been present in the oral environment of a wide variety of hominins. Caries prevalence in studied fossil hominins is similar to those in pre-agricultural human groups, in which 1–5% of teeth are typically affected

Relationship between Tibial conformation, cage size and advancement achieved in TTA procedure

Previous studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted. The purpose of this study was to test and quantify this in clinical cases. The hypothesis was that the advancement of the tibial tuberosity as measured by the widening of the proximal tibia at the tibial tuberosity level after a standard TTA, will be less than the cage sized used, with no particular cage size providing a relative smaller or higher under-advancement, and that the conformation of the proximal tibia will have an influence on the amount of advancement achieved