Objectives
A tooth chip occurs when a hard object forcefully contacts the surface of the tooth, typically removing enamel from the occlusal edge. In this study, chipping patterns in extant primates ...were compared, and hard‐object‐feeding assessed alongside other factors (e.g., grit mastication and dental properties), to elucidate dietary and behavioral inferences in archeological and paleontological samples.
Materials and methods
Thirteen species of extant primates were studied, including eight species within the Cercopithecidae, two within the Ceboidea, and three within the Hominoidea. Four additional species were also incorporated from the literature for some of the analyses. The severity (Grade 1–3), position (buccal, lingual, mesial, and distal) and number of tooth fractures were recorded for each specimen.
Results
Species considered hard‐object‐feeding specialists presented higher rates of chipping, with sakis, mandrills, sooty mangabeys and Raffles' banded langurs having high chipping rates (28.3%, 36.7%, 48.4%, and 34.7% of teeth, respectively). Species that seasonally eat harder foods had intermediate chipping frequencies (e.g., brown woolly monkeys: 18.5%), and those that less commonly consume hard food items had the lowest chipping frequencies (e.g., Kloss gibbon: 7.3%; chimpanzees: 4.4%).
Discussion
The results suggest hard food mastication influences differences in chipping prevalence among the species studied. Although Homo fossil samples show high rates of chipping comparable to hard‐object‐feeding extant primates, they display a different pattern of chipping, supporting the hypothesis that these fractures are mostly non‐food related (e.g., grit mastication in Homo naledi; non‐masticatory tooth use in Neanderthals).
Tooth chipping in wild primates.
Tertiary dentine forms when an odontoblast is directly affected by stimuli, commonly through occlusal wear and caries. In this study the presence of tertiary dentine was recorded in three South ...African fossil hominin species ('Australopithecus africanus, Homo naledi and Paranthropus robustus'), and two extant great ape species ('Gorilla gorilla gorilla' and 'Pan troglodytes'). Frequencies of tertiary dentine were calculated for each species based on macroscopic observations of teeth with dentine exposed through occlusal wear. Overall, the three hominin species have similar tertiary dentine frequencies ranging from 12% to 16.13%. In contrast, over 90% of permanent gorilla teeth with dentine visible show tertiary dentine. Chimpanzees fall between these extremes, with 47.21% of permanent teeth affected. Deciduous teeth follow the same pattern. Species variances are not related to differences in occlusal wear. Instead, some species appear predisposed to produce tertiary dentine earlier/faster, or more often, than other species. Therefore, tertiary dentine formation has the potential to provide useful information on fossil specimens. For example, the uniformly low frequency of tertiary dentine formation in hominins may relate to diet, or be due to thick enamel having a similar role in preventing loss of function of teeth, i.e., extending the life of a tooth. In contrast, tertiary dentine is clearly an important mechanism for normal dental function in gorillas, and may have evolved to help maintain shearing function.
Objectives
A variety of mechanical processes can result in antemortem 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 and in samples of nonhuman primates (n = 3) and recent humans (n = 7).
Results
With 44% of teeth affected, H. 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 nonmasticatory cultural behavior was the cause. A diet containing hard and resistant food, or contaminants such as grit, is more likely. The small chip size, and steep occlusal wear and cupped dentine on some molars are supportive of the latter possibility. This pattern of chipping suggests that H. naledi differed considerably—in terms of diet, environment, and/or specialized masticatory processing—relative to other African fossil hominins.
Display omitted
•The dispersion co-polymerization of PAEK polymers is reported.•They are synthetically readily available by Lewis acid-mediated Friedel-Crafts polymerization.•The polymers have been ...characterised by combustion analysis, inherent viscosity, DSC, and NMR analysis.•They exhibit suitable polymeric characteristics for engineering materials.
A range of particulate polyaryletherketone polymers and copolymers, incorporating ether-imide, sulfone, naphthalene, and aliphatic functionalities, along with branching monomers, may be successfully produced by a dispersion polymerisation process, provided that the reaction parameters are optimised. This significantly expands the range of monomers suitable for application in the Friedel Crafts dispersion polymerisation process.
Once considered rare in fossil hominins, caries has recently been repor ted 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.Significance: • This study adds to the growing evidence that dental caries was present throughout the course of human evolution. Caries prevalence in the fossil species studied is similar to those in non-agricultural human groups, with 1–5% of teeth displaying cavities. • Differences in prevalence and position of dental caries can provide insight into dietary aspects of past populations. South African fossil hominins display lesions on their posterior teeth, suggesting sugary foods were consumed.
Fluctuating Asymmetry (FA) in morphology is used as a proxy for developmental instability in response to stress factors. FA has important implications for understanding the impact of differential ...environments and stressors on the skeletal phenotype. Here, we explore FA in the mandibular morphology of wild and captive Macaca fuscata to detect differences induced by the captive environment. We use two different approaches in Geometric Morphometrics to characterise the degree and patterns of FA and Directional Asymmetry (DA) based on 3D mandibular landmarks. Our results show that the wild and captive groups exhibit morphological dissimilarities in the symmetric component of shape while no significant degree of asymmetry (fluctuating or directional) was detected. Based on our results and on previous literature on the subject, we suggest that (I) captivity is likely to affect the mandibular morphology of M. fuscata; (II) FA may not be a suitable indicator to detect stress in the conditions analysed; and that (III) the mandible may not be the ideal region to study asymmetry because of its functional nature.
A range of particulate poly(ether ketone ketone)s (PEKKs) have been synthesised by a room temperature Friedel–Crafts dispersion polymerisation. Their properties, including glass transition, melting ...and crystallisation temperatures, the degree of crystallinity and particle size, were readily controlled by altering the ratio of 1,3- to 1,4-units in the polymer backbone. The bulk polymer properties are comparable to materials produced by alternative methods and the polymers are highly melt stable. Unusually, all PEKKs are highly crystalline as produced, although some become amorphous on further processing. Evidence was obtained which is consistent with the particulate product being formed by a seeding mechanism, from aluminium( iii ) seeding particles which are formed in situ .
Display omitted
•The dispersion polymerisation of amine-terminated PEEK polymers is reported.•They are synthetically readily available by Lewis acid-mediated Friedel-Crafts polymerisation.•The ...polymers have been characterised by combustion analysis, inherent viscosity, DSC, SEM and fracture analysis.•They exhibit suitable polymeric characteristics for engineering materials.
Amine end-capped polyaryletherketones (PAEKs) are available by a dispersion process using a protection-deprotection strategy with an end-capping aminoaromatic derivative which adds no further steps to the dispersion polymerisation method. A model compound approach was employed to demonstrate successful amine attachment to the polymer, together with its compatibility and suitability within the polymer system. This approach was also successful for linear and trifunctional versions. Scale-up of the PAEK dispersion synthesis to 300g batches was achieved. Amine end-capped poly(ether ketone ketone) (PEKK) with 100:0, 80:20, 60:40 terephthaloyl (T):isophthaloyl (I) ratios, along with branched PEKK and PEKK-imide copolymers, were synthesised. Mechanical analysis confirmed a substantial increase in fracture toughness on incorporation of the functionalised PEKK particles in an epoxy resin laminate when compared to non-functionalised PEKK particles.
Plane-form enamel hypoplasia (PFEH) is a severe dental defect in which large areas of the crown are devoid of enamel. This condition is rare in humans and even rarer in wild primates. The etiology of ...PFEH has been linked to exposure to severe disease, malnutrition, and environmental toxins and associated with systemic conditions. In this study, we examined the prevalence of enamel hypoplasia in several populations of wild Japanese macaques (Macaca fuscata) with the aim of providing context for severe defects observed in macaques from Yakushima Island. We found that 10 of 21 individuals (48%) from Yakushima Island displayed uniform and significant PFEH; all 10 specimens were from two adjacent locations in the south of the island. In contrast, macaques from other islands and from mainland Japan have a low prevalence of the more common types of enamel hypoplasia and none exhibit PFEH. In Yakushima macaques, every tooth type was affected to varying degrees except for first molars and primary teeth, and the mineral content of the remaining enamel in teeth with PFEH was normal (i.e., no hypo- or hypermineralization). The aetiology of PFEH might be linked to extreme weather events or high rates of environmental fluoride-causing enamel breakdown. However, given that the affected individuals underwent dental development during a period of substantial human-related habitat change, an anthropogenic-related etiology seems most likely. Further research on living primate populations is needed to better understand the causes of PFEH in wild primates.
This study examines whether larger enamel prism diameters accommodate a greater enamel volume from the enamel-dentine junction (EDJ) to the outer-enamel surface (OES) in primate molars, and how prism ...size relates to enamel thickness and crown location.
We assessed variation in enamel prism diameter in relation to crown location and enamel thickness in catarrhine lower molars (n = 14 species) and one platyrrhine. Prism diameter and enamel thickness were recorded in four locations (lingual lateral; lingual cuspal; buccal cuspal; buccal lateral), using a buccal-lingual section through the centre of the mesial cusps. Ten prism diameter readings were collected at inner (near the EDJ), outer (near the OES) and middle (between the two locations) enamel for each location.
Mean prism diameter values for each species were similar (range: 4.06 µm to 5.81 µm). Prism diameter enlarged from inner to outer enamel, suggesting larger prisms help accommodate the increase in enamel volume from the EDJ to the OES. Average prism diameter does not associate with enamel thickness. Instead, cuspal positions had significantly smaller prism diameter at the EDJ than lateral positions, and larger prism sizes at the OES, leading to an overall similar prism diameter mean for all positions (Lingual lateral: 5.11 µm; Lingual cuspal: 5.04 µm; Buccal cuspal: 4.78 µm; Buccal lateral: 4.99 µm).
Our study revealed consistent average enamel prism diameters in various crown locations of lower primate molars, potentially contributing to the mechanical integrity and functional optimization of enamel in primates.
•Enamel prism size varies with crown location in primate molars.•Consistent mean prism diameter (4.06 µm to 5.81 µm) across primate species.•Cuspal positions show biggest prism diameter increase across enamel thickness.•Results provide insights into enamel structural and mechanical properties variation.
PDF
