Dental Wear Patterns Research Articles

Wear Pattern, Dental Function, and Jaw Mechanism in the Late Cretaceous Ankylosaur Hungarosaurus

ABSTRACTFeeding in thyreophoran dinosaurs is poorly understood. Although the group existed for over 130 million years, only the Early Jurassic basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous ankylosaurid Euoplocephalus tutus have been studied from this perspective in detail. In contrast to the earlier, conservative hypothesis of a simple “orthal pulping” feeding mode with no or limited tooth–tooth contact, recent studies have demonstrated precise dental occlusion with differing jaw mechanisms in these two species. Here, we describe the first detailed study of feeding related characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the Late Cretaceous of Hungary. Dental wear patterns comprising small, apical, and low‐angled facets on the maxillary and steep, extended, and bowl‐like facets on the dentary teeth reveal sophisticated tooth–tooth contact in this basal nodosaurid. The presence of two different scratch generations (vertical and low‐angled) on the dentary teeth unambiguously demonstrate a multiphasic powerstroke, which is further supported by the morphology of the quadrate‐articular and mandibular symphyseal joints and by the architecture of the reconstructed jaw adductors. Chewing started with an initial slicing phase associated with orthal movement that was followed by a retractive powerstroke with significant occlusal contact. Because of the curved tooth rows, these movements were probably facilitated by some mediolateral translation and/or axial rotation of the mandibles to produce precise shearing along the whole tooth row. These results demonstrate that complex jaw mechanisms and dental occlusion were more widespread among thyreophorans than thought previously and that palinal movement was present in at least two ankylosaurian lineages. Anat Rec, 297:1165–1180, 2014. © 2014 Wiley Periodicals, Inc.

A new system for computing dentition-based age profiles in Sus scrofa

Reconstructing demographic profiles is valuable for revealing animal exploitation strategies at archaeological sites. For pig (Sus scrofa), the method presented by Grant (1982) demonstrates a promising technique for estimating age through dental wear pattern analysis. Grant's study is, however, limited as it requires complete or nearly complete mandibles, exclusively uses mandibular teeth, and offers only a relative scale for aging. While some work has been done to establish useful age classes based on tooth eruption and wear patterns in S. scrofa, a systematic study producing a standardized and comprehensive methodology for using tooth wear to age pigs remains to be conducted.The study presented here is part of ongoing research aimed at developing new methods for the construction of S. scrofa demographic profiles based on both dentition and long bone fusion. In this paper, we present the results of a study of eruption and wear patterns in a large modern assemblage of wild boar which provides the basis for a new method for constructing pig harvest profiles and addresses some of the most serious limitations of Grant's earlier study. The utility of this method in detecting subtle differences in pig prey/harvest profiles is demonstrated through its application to three Near Eastern archaeological assemblages from three distinct time periods: Bronze Age Tell Leilan, Halafian Banahilk, and Epipaleolithic Hallan Çemi, where residents likely employed widely different pig exploitation strategies. The results of these case studies demonstrate the ability of this method to reliably reconstruct age demography and distinguish age profiles between sites with different animal procurement strategies. This method provides a standardized means of collecting accurate and reliable age data crucial in examining patterns of past pig exploitation.

Wear Pattern, Dental Function, and Jaw Mechanism in the Late Cretaceous Ankylosaur Hungarosaurus

Feeding in thyreophoran dinosaurs is poorly understood. Although the group existed for over 130 million years, only the Early Jurassic basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous ankylosaurid Euoplocephalus tutus have been studied from this perspective in detail. In contrast to the earlier, conservative hypothesis of a simple "orthal pulping" feeding mode with no or limited tooth-tooth contact, recent studies have demonstrated precise dental occlusion with differing jaw mechanisms in these two species. Here, we describe the first detailed study of feeding related characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the Late Cretaceous of Hungary. Dental wear patterns comprising small, apical, and low-angled facets on the maxillary and steep, extended, and bowl-like facets on the dentary teeth reveal sophisticated tooth-tooth contact in this basal nodosaurid. The presence of two different scratch generations (vertical and low-angled) on the dentary teeth unambiguously demonstrate a multiphasic powerstroke, which is further supported by the morphology of the quadrate-articular and mandibular symphyseal joints and by the architecture of the reconstructed jaw adductors. Chewing started with an initial slicing phase associated with orthal movement that was followed by a retractive powerstroke with significant occlusal contact. Because of the curved tooth rows, these movements were probably facilitated by some mediolateral translation and/or axial rotation of the mandibles to produce precise shearing along the whole tooth row. These results demonstrate that complex jaw mechanisms and dental occlusion were more widespread among thyreophorans than thought previously and that palinal movement was present in at least two ankylosaurian lineages.

On the Variability of the Dmanisi Mandibles

The description of a new skull (D4500) from the Dmanisi site (Republic of Georgia) has reopened the debate about the morphological variability within the genus Homo. The new skull fits with a mandible (D2600) often referred as ‘big’ or ‘enigmatic’ because of its differences with the other Dmanisi mandibles (D211 and D2735). In this report we present a comparative study of the variability of the Dmanisi mandibles under a different perspective, as we focus in morphological aspects related to growth and development. We have followed the notion of modularity and phenotypic integration in order to understand the architectural differences observed within the sample. Our study reveals remarkable shape differences between D2600 and the other two mandibles, that are established early in the ontogeny (during childhood or even before) and that do not depend on size or sexual dimorphism. In addition, D2600 exhibits a mosaic of primitive and derived features regarding the Homo clade, which is absent in D211 and D2735. This mosaic expression is related to the location of the features and can be explained under the concept of modularity. Our study would support the possibility of two different paleodemes represented at the Dmanisi site. This hypothesis has been previously rejected on the basis that all the individuals were constrained in the same stratigraphic and taphonomic settings. However, our revision of the complex Dmanisi stratigraphy suggests that the accumulation could cover an undetermined period of time. Even if “short” in geological terms, the hominin accumulation was not necessarily synchronic. In the same line we discard that the differences between D2600 and the small mandibles are consequence of wear-related dentoalveolar remodeling. In addition, dental wear pattern of D2600 could suggest an adaptation to a different ecological niche than the other Dmanisi individuals.

Prevalence, severity and etiology of dental wear in patients with eating disorders.

Objective:The purpose of this study was to evaluate the prevalence, distribution and associated factors of dental wear among patients with eating disorders (EDs).Materials and Methods:An epidemiological cross-sectional survey was conducted by trained, calibrated examiners, using the dental wear index. The sample was composed of 30 patients with EDs (experimental group – G1) and 30 control patients without current or previous history of EDs (G2). A questionnaire was used to assess the etiological factors of dental wear. The univariate analyses using the Chi-square (χ2) test were used to compare the tooth wear prevalence between groups according to the surface and tooth (P > 0.05).Results:The dental wear was similar for both group; however, the G1 presented more moderate wear in molars when compared with G2 (P = 0.048). The majority of EDs patients related have one or more oral habits (n = 26; 86.6%) and only 13.4% (n = 4) affirmed did not have oral habits. The etiological factors of tooth wear related with dental wear were biting objects (P = 0.04) and pain in temporomandibular disorders (P = 0.03).Conclusion:The highest prevalence of dental wear was observed in the molars teeth. Differences in the extent and pattern of dental wear were found in an individual, emphasized the relevance of clinical parameter.

Dental morphology and wear pattern of bamboo rats, genus Rhizomys (Rodentia: Spalacidae)

Rhizomys, one of the most derived genera within the tribe Rhizomyini (Rhizomyinae, Spalacidae, Rodentia), comprises three species: Rhizomys sinensisGray, 1831, R. pruinosusBlyth, 1851 and R. sumatrensis (Raffles, 1821). A detailed description of the morphology and wear pattern of the cheek teeth of this taxon is provided based on the study of 41 skulls. The variability tracked is due primarily to wear, control of which facilitates comparison of different individuals, fossil or not, at different wear stages. For the first lower and upper molars, six stages of wear (0–5) are recognized. The second lower and upper molars show five stages of wear (0–4), whereas the third ones have four (0–3). The dental wear pattern in Rhizomys is comparable to that of the Pliocene Brachyrhizomys shansiusTeilhard de Chardin, 1942.

Exploring the relationship between dental wear and status in late medieval subadults from England

Dental wear patterns were recorded on 458 deciduous molar teeth, of 142 subadults from late medieval (AD 1086-1539) England, to explore the relationship between dental wear and burial status of children. A new ordinal method for scoring dental wear stages on the deciduous molar teeth was devised. It was postulated that if a discernible relationship between dental wear stage and burial location could be seen then this could reflect a difference in diet between those receiving higher or lower status burial. The dental wear stages recorded were statistically similar for the dentitions of subadults from different cemeteries, as well as from different burial locations, indicating a comparable diet for the children studied.

Tracking environmental changes in the Pleistocene using dental wear patterns in European fossil ungulates

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Dental morphology of the Lesser Bamboo Rat, Cannomys badius (Rodentia, Spalacidae).

Cannomys and Rhizomys are the sole living genera of the tribe Rhizomyini (Rhizomyinae, Spalacidae, Rodentia), known in the fossil record since the Late Miocene. The dental morphology of fossil Rhizomyini has been described in detail but until recently such descriptions were unavailable for extant species. A detailed account of the morphology and dental wear pattern of the cheek teeth of Cannomys badius is provided here based on the examination of museum specimens. Three stages of wear are recognized. Cannomys shares with Rhizomys the synapomorphy of having a mesolophid that is a long continuation of the protoconid on the first lower molar. There are significant differences between these taxa, such as the much smaller size of the cheek teeth and the trilophodont dental pattern of the M2, M3, and m2 in Cannomys.

Dental Wear Patterns and Subsistence Activities in Early Nomadic Pastoralist Communities of the Central Asian Steppes

Dental wear patterns were studied in five ancient groups of Siberia and Mongolia. The results indicate considerable variation of subsistence activities among populations practicing different forms of pastoralism. In all groups, dental wear patterns in various classes of teeth appear to be more related to subsistence activities than to age at death.

Kinetic Limitations of Intracranial Joints in Brachylophosaurus canadensis and Edmontosaurus regalis (Dinosauria: Hadrosauridae), and Their Implications for the Chewing Mechanics of Hadrosaurids

The highly specialized tooth morphology and arrangement of the dental battery of hadrosaurids has led to much speculation surrounding the chewing mechanics of this successful group of herbivorous dinosaurs. Pleurokinesis, a long established hypothesis explaining the ornithopod chewing mechanism, proposes a transverse power stroke in hadrosaurids that was accommodated by vertical adduction of the mandible, lateral rotation of the maxilla at the maxilla-premaxilla joint, lateral rotation of the jugal-maxilla complex at its contact with the lacrimal, and posterolateral rotation of the quadrate at its contact with the squamosal. A secondary series of movements were also thought to have occurred as a consequence of these primary movements. In this article, the intracranial joint morphology is described for both Brachylophosaurus canadensis and Edmontosaurus regalis and their permissive kinematics are established. Based on this evidence, the movements associated with pleurokinesis are not accommodated in these hadrosaurine dinosaurs. Rather, the movements that seem most likely to have produced the observed dental wear patterns are those associated with the mandible about the jaw joint. The structure of this joint appears well-suited to have accommodated some translation as well as rotation of the mandible about the quadrate condyle. Three-dimensional modeling of the alternate mandibular movements reveals that not all the combined labiolingual width of the lingual and buccal facets of the tooth row was involved in the power stroke. Rather, limits on the degree of mandibular long axis rotation suggest that only the lingual facet and the more medial portion of the buccal facet were utilized.

Dental morphology and wear pattern in Tachyoryctes (Spalacidae, Rodentia)

Tachyoryctes, the most derived genus within the tribe Tachyoryctini (Rhizomyinae, Spalacidae, Rodentia), is known from Pliocene to Recent. It comprises four species: the fossil T. pliocaenicus and T. konjiti and the extant T. splendens and T. macrocephalus. A detailed description of the morphology and dental wear pattern of the cheek teeth of T. splendens is provided based on the study of 297 skulls. For the first and second lower and upper molars, five stages of wear are recognized (0–4). The third lower and upper molars show four stages of wear (0–3). The dental wear pattern in T. splendens is comparable to that of the Pleistocene T. konjiti.

Evaluation of Dental Wear Patterns and Preferred Chewing Direction in Horses

Evaluation of Dental Wear Patterns and Preferred Chewing Direction in Horses

On the relationship between hypsodonty and feeding ecology in ungulate mammals, and its utility in palaeoecology

High-crowned (hypsodont) teeth are widely found among both extant and extinct mammalian herbivores. Extant grazing ungulates (hoofed mammals) have hypsodont teeth (a derived condition), and so extinct hypsodont forms have usually been presumed to have been grazers. Thus, hypsodonty among ungulates has, over the past 150 years, formed the basis of widespread palaeoecological interpretations, and has figured prominently in the evolutionary study of the spread of grasslands in the mid Cenozoic. However, perceived inconsistencies between levels of hypsodonty and dental wear patterns in both extant and extinct ungulates have caused some workers to reject hypsodonty as a useful predictive tool in palaeobiology, a view that we consider both misguided and premature. Despite the acknowledged association between grazing and hypsodonty, the quantitative relationship of hypsodonty to the known ecology of living ungulate species, critical in making interpretations of the fossil record, was little studied until the past two decades. Also, much of the literature on ungulate ecology relevant to understanding hypsodonty has yet to be fully incorporated into the perspectives of palaeontologists. Here we review the history and current state of our knowledge of the relationship between hypsodonty and ungulate ecology, and reassert the value of hypsodonty for our understanding of ungulate feeding behaviour. We also show how soil consumption, rather than the consumption of grass plants per se, may be the missing piece of the puzzle in understanding the observed correlation between diets, habitats, and hypsodonty in ungulates. Additionally, we show how hypsodonty may impact life-history strategies, and resolve some controversies regarding the relevance of hypsodonty to the prediction of the diets of extinct species. This in turn strengthens the utility of hypsodonty in the determination of past environmental conditions, and we provide a revised view of a traditional example of evolutionary trends in palaeobiology, that of the evolution of hypsodonty in horses and its correlation with the Miocene spread of grasslands in North America.

Diet of Mongolian gazelles and Tibetan antelopes from steppe habitats using premaxillary shape, tooth mesowear and microwear analyses

The diets of Procapra gutturosa (Mongolian gazelle) and Pantholops hodgsoni (Tibetan antelope) are investigated through premaxillary shape, mesowear, and microwear analyses. The objective of the study is to test the hypothesis that the two species have similarities in dietary habits and also similarities with arctic or subarctic ungulates such as muskox ( Ovibos moschatus) and caribou ( Rangifer tarandus). Results indicate similarities between Procapra gutturosa and Pantholops hodgsoni, and also some variability in dietary habits related to seasonal and/or regional changes in their habitats. Dental wear patterns for the two species are similar to another ungulate from the arctic steppe environments, the caribou ( Rangifer tarandus). This supports the hypothesis that such similarities are reflected in dietary habits because the plant items consumed by those species have similar properties in terms of abrasiveness which are reflected in the tooth wear patterns observed through mesowear and microwear analyses. These results reveal a consistent dietary habit for certain ungulates from this type of arid or dry habitat and climate.

Estimating age of carnivores from the Pantanal region of Brazil

AbstractConservation and management of animal populations often require knowledge about the age structure, but this information is usually difficult to discern. We propose a method to estimate the age of carnivores based on dental condition and body size measurements, and we apply the method to populations of brown‐nosed coatis Nasua nasua and crab‐eating foxes Cerdocyon thous in the Brazilian Pantanal. We sexed, weighed and measured 31 coatis and 45 foxes of known‐age, and characterized and quantified their pattern of dental eruption and wear for the construction of a teeth condition index. Scores of the first factors of a principal component analysis including data on six body size measurements and the teeth condition index of the individuals were then used in a discriminant analysis to generate functions that can be used for estimating age of animals of unknown age. Models were validated using subsets of individuals of known age through a 3‐fold cross validation process. The first functions accounted for over 90% of the discriminatory power for both species. Whereas in coatis, the first function was mainly explained by the body size measurements, in crab‐eating foxes it was represented mainly by the teeth condition index. During model validation, individuals were on average classified with 88 and 80% average confidence for coatis and foxes, respectively. Our method is as accurate as other methods that are commonly applied to assess age, but less subjective. While it requires animal capturing, it is less invasive than methods requiring tissue removal such as analyses of teeth cementum annuli. The method we outlined can be used for age estimation of other populations, as long as the models are validated with a subset of animals from the region studied. It could also be useful as a model for estimating age of other carnivore species.

Domestic and wild ungulate dietary traits at Kouphovouno (Sparta, Greece): implications for livestock management and paleoenvironment in the Neolithic

The objective for this study is to explore interspecific variations in domestic and wild ungulate diets and management at the Neolithic site of Kouphovouno (Sparta, southern Greece). We tested four hypotheses related to environmental context and livestock management using, for the first time, a combination of mesowear and microwear analyses on a Neolithic site. We identified interspecific differences between ungulate taxa, especially between wild and domestic ungulates, however there is no significant difference between Ovis and Capra. There is no diachronic change in diet from the Middle Neolithic to the Late Neolithic. Changes in animal utilization are not reflected in their diet. Whatever the purpose of the husbandry, animals had access to the same food resources. The study of dental wear patterns gave some insights regarding the management practices for the domestic livestock as well as paleoenvironment through the study of wild ungulates.

What can incisor microwear reveal about the diet of ungulates?

Abstract We analyzed dental wear patterns on molars and incisors of modern plains zebra (Equus quagga) from a single locality in Kenya and from a single breeding population. Our objective was to explore the potential of incisor microwear in terms of elucidating ungulate diet as well as the various chewing patterns of different incisors and molar teeth among various age classes. We found significant inter-tooth variation of the microwear signal among different incisors and, not unexpectedly, that incisors do not reveal the same dietary signal as molar teeth. Such differences are related here to differential chewing forces (shearing vs compression) along the tooth row. We find no significant differences among various zebra age classes in terms of their mesowear and microwear patterns, providing additional evidence that the mesowear signal is consistent and stable throughout the adult lifespan of an individual. These findings indicate that there is no age segregation in terms of access to food resources in this particular breeding population.

Palaeoecology of the Mammoth Steppe fauna from the late Pleistocene of the North Sea and Alaska: Separating species preferences from geographic influence in paleoecological dental wear analysis

The paleodietary ecology of Late Pleistocene ungulate faunas of the Mammoth Steppe ecosystem was investigated at Fairbanks (Alaska) and Brown Bank (North Sea) through dental mesowear and microwear analysis. The purpose of the study is to address questions concerning the paleoecology of the Mammoth Steppe, an ecosystem that has no extant analog. Dental wear patterns indicate that the niche partitioning at Brown Bank (BB) region was consistent with ecosystem dynamics found in diverse ungulate faunas in recent time. In contrast, despite the lower numbers of extinct taxa, the Fairbanks (FB) fauna is ecologically bizarre. In general, the microwear of this fauna includes excessive numbers of very (narrow) fine scratches that are atypical for extant mixed feeders and grazers. Moreover, the mesowear signal suggests unusual paleodiets (niche dynamics), where low-crowned mixed-feeding cervids, Rangifer and Cervus, adopted diets that are similar to Equus in terms of mesowear (abrasion) and much more abrasive than the diets of either Bison or Ovis. We suggest that the anomalies may relate to unique, possibly disharmonious, ecosystem dynamics during the Pleistocene–Holocene transition. In addition to these findings, it was discovered (found) that dental wear patterns, particularly microwear variables such as scratch frequency and scratch width are strongly affected by geographic region, irrespective of species-specific dietary preferences.

Technical note: Occlusal fingerprint analysis: Quantification of tooth wear pattern

Information about food ingestion and mastication behavior during the lifespan of an individual is encoded in the dental occlusal wear pattern. To decode this information, we describe a new method called occlusal fingerprint analysis (OFA). Structural parameters of wear facets on the occlusal surface of teeth are quantified from digitized casts for the interpretation of occlusal aspects. The OFA provides an individual three-dimensional dental occlusal compass that indicates the major pathways of interaction between antagonists, revealing information about development, spatial position, and enlargement of wear facets. Humans develop a very similar overall pattern of crown contacts, although specific characteristics of wear facets reflect an individual's occlusal relationships and masticatory behavior. We hypothesize that the wear pattern is a unique character and therefore valuable for individual identification. Furthermore we suggest that OFA, when further developed, may be useful for identification of behavioral, biological, and chemical factors affecting crown morphology.