Tooth Wear Patterns Research Articles

Determining the age classes of free-ranging female nilgai (Boselaphus tragocamelus) in southern Texas, USA

Age classification methods have not been evaluated for free-ranging nilgai antelope (Boselaphus tragocamelus) either on their native or introduced ranges of southern Texas, USA. Our objectives were to 1) determine if cementum annuli aging was a feasible method for aging nilgai, 2) measure the crown-lingual crest heights of nilgai molariform teeth to assess if these measurements were correlated to the cementum-annuli age of nilgai, and 3) develop nilgai age classes based on visual observations of tooth eruption and wear patterns. Six commercial nilgai meat harvests were conducted via helicopter from May–September 2018–2021 across 3 properties. We collected data from 225 harvested nilgai (n = 213 females and n = 12 juvenile males). We found significant relationships between cementum annuli ages and the crown-lingual crest heights of nilgai teeth (n = 63). However, the relationship was weak given the low R-squared values (0.23–0.46), suggesting that the age of female nilgai does not explain a large amount of variation among tooth heights (i.e., wear). From nilgai teeth samples, we documented 13 tooth eruption stages and 6 age classes. Female nilgai age classes presented provide land managers with the basic tools needed to assess population age structures. On the Indian subcontinent, our method could be used to evaluate age-biased predation on free-ranging nilgai.

Progressive Tooth Wear Against Resin-Based Restorative Composites.

The composition and properties of resin-based composite materials could affect tooth wear and lead to clinical problems. Therefore, the study objective was to characterize human tooth wear behavior against a bulk-fill restorative (BF) compared to a conventional resin composite (RC) and a CAD/CAM resin nano ceramic (RN). Square-shaped specimens of each material were prepared and sub-divided according to the number of testing cycles (n=8): 100,000, 250,000, and 500,000 cycles. An occlusal wear test was performed using a chewing machine with 49 N, 2 Hz, in 37°C distilled water. Human premolar cusps were used as antagonists. Micro-CT and laser scanner were used to scan antagonists and specimens, respectively. Wear volume was assessed using a software and the wear pattern was examined with SEM. Softening in solvent analysis was performed by measuring the materials' Knoop microhardness (KHN) before and after immersion in ethanol. Wear volume data were analyzed with two-way ANOVA and Student-Neuman-Keuls test (α=0.05). For tooth and specimen wear volume, there was statistical significance for material and number of cycles, but not for the interaction between factors. BF resulted in less tooth (p=0.008) and specimen (p=0.030) wear than RN and RC, which were similar (p⟩0.05). Volume loss increased from 100,000 to 500,000 cycles. BF showed the lowest microhardness (KHN1); and %ΔKHN similar to RC, but greater than RN. BF induced less volume loss to the tooth than RC and RN, while presenting greater wear resistance. The tooth wear pattern and damage progression were mild for all materials. Resin composites show favorable wear behavior, leading to low volume loss and mild structural damage of the tooth. Regular bulk-fill resin composite stands out for its efficient restorative technique, low wear susceptibility and reduced capacity to wear down the tooth.

Long-term occlusal tooth wear at the onset of permanent dentition

ObjectivesThis study quantified the long-term occlusal wear in the natural posterior teeth and the associations per tooth type within the dentition.MethodsThe sample included 70 orthodontically treated subjects (52 females and 18 males; median age, 14.3 years), followed for a 12.7-year period. They were consecutively selected with no tooth wear–related criteria. Post-treatment (T1) and follow-up dental casts (T2) were scanned and superimposed through three-dimensional methods. Occlusal wear volume of posterior teeth and tooth wear patterns were investigated through non-parametric statistics and analysis of covariance.ResultsThere were no significant differences between contralateral teeth. The average occlusal wear per posterior tooth was 2.3 mm3, with 65.2% of teeth showing values greater than 1 mm3. Males, mandibular teeth, and first molars exhibited slightly greater wear levels than females (median, 2.57 and 2.21 mm3, respectively; p = 0.005), maxillary teeth, and first or second premolars, respectively. In all first premolars and in the mandibular second premolars, the buccal cusps were primarily affected with no other distinct patterns. There were weak to moderate correlations between tooth types, apart from certain strong correlations detected in males.ConclusionsPosterior tooth wear was highly prevalent after a 13-year period starting at the onset of permanent dentition. The detected patterns are in accordance with the concept of canine guidance occlusion that is transforming into group synergy through function.Clinical relevanceThe widespread tooth wear occurrence and the high intra- and inter-individual variability underline the need for individual patient monitoring to identify high-risk patients at early stages.

Prevalence of tooth wear diseases in patients with diabetes and its impact on the quality of life in Dakshina Kannada population: a cross sectional study.

Early detection and management of tooth wear (TW) has not been given due consideration in the dental profession. Thus, this study aimed to explore the prevalence of TW in adults with diabetes in Dakshina Kannada population using the Basic Erosive Wear Examination (BEWE) and recording its impact on quality of life using the Oral Health Impact Profile (OHIP-14). In total, 236 dentate adults with diabetes and TW, who visited the Manipal College of Dental Sciences, Mangalore were recruited to the study. Assessment of TW was done using BEWE during examination of each participant and was categorized as none, mild, moderate, and severe. Impact of TW on quality of life was assessed using the OHIP-14. Overall, 81 (34.30%) individuals had a poor score on the basic erosive tooth index, 82 (34.70%) had a medium score, . The level of TW, both moderate and severe (high), affected quality of life. Erosion, abrasion and attrition were seen in a large proportion of the study population. The diabetic status of the individual was collected from their medical file. The HbA1C level was found to range from good, fair and poor control. The quality of life among the study population was affected because of TW and diabetes. Few participants had hypertension along with diabetes. The majority of study participants were on oral hypoglycaemic agents. Participants used tooth brushes and tooth paste and brushing frequency varied between once or twice daily. In the study population, there were moderate and severe TW patterns. Quality of life was found to be impacted by TW. Dental professionals must give proper consideration to the influence of TW on quality of life in addition to clinical findings. This will make it easier to offer preventive or restorative management depending on the situation.

Estimating age of mule deer in the field: Can we move beyond broad age categories?

Age of individuals is an intrinsic demographic parameter used in the modeling and management of wildlife. Although analysis of cementum annuli from teeth is currently the most accurate method used to age ungulates, the age of live ungulates in the field can be estimated by examining tooth wear and tooth replacement patterns. However, there may be limitations to aging based on tooth wear as the rate of tooth wear likely varies among individuals due to factors such as age, diet, environment, and sex. Our objective was to determine the reliability of estimating age for mule deer based on tooth wear and tooth replacement patterns. We compared ages estimated by tooth wear (collected at time of capture for a statewide monitoring effort) to ages determined from cementum analysis (from teeth collected after mortalities of radio-tracked animals from the monitoring effort). Accuracy was high; ages estimated from tooth wear were within one year of cementum ages >75% of the time when aged by experienced observers. Bias in accuracy for estimates of age was low but slightly biased toward underestimation (i.e., 0.6 years on average)-especially as cementum age increased. Our results indicate that aging mule deer using patterns in tooth wear can be reliable if observers estimating age have experience using this method.

A method for assessing relative wear rate in cattle molars, with an application to the Iron Age and Roman periods

Mandibular tooth wear patterns are important in zooarchaeological research as they can be used as a record of age at death. Age profile comparisons between different archaeological assemblages, therefore, rest on the assumption that tooth wear rates are consistent across groups. Consequently, Salvagno et al. [Journal of Archaeological Science, 127, pp. 1–17 (2021)] recently devised a method to determine relative tooth wear rate (TWR) of pig molars and assess the comparability of archaeological kill-off patterns. Their method quantifies the relative tooth wear rate between two adjacent mandibular molars and uses this to calculate the average wear rate (AWR) of an archaeological population. This paper adapts their method for use on cattle molars, to evaluate whether differences in relative tooth wear rates both within, and between, different archaeological cattle assemblages may affect age estimations.The method is applied to two case studies: Iron Age and Roman assemblages from Elms Farm, Heybridge, UK and Houten-Castellum, Netherlands. These are compared to two outgroups: a collection of European aurochs data, and a modern cattle assemblage from Germany. The method is additionally tested across species, by comparing cattle and pig relative tooth wear rates from Heybridge. Methodological considerations regarding the use of scoring systems to assess wear rate are identified and discussed. The potential causes of variation in tooth wear rates - such as diet, environmental inclusions, dental abnormalities, and genetic variation - are also considered.This study demonstrates the ease and affordability with which the tooth wear rate method can be employed. The results provide no evidence to suggest that comparisons of cattle age profiles between the Iron Age and Roman period at Heybridge or Houten-Castellum may be significantly compromised. However, differences in relative tooth wear rate were found between these two sites, and when comparing them to aurochs and modern outgroups. On this basis, it is suggested that caution be used when comparing kill-off patterns from different archaeological cattle assemblages, and that this methodology be employed routinely to increase the reliability of archaeological interpretations.

A Computerized Simulation of the Occlusal Surface in Equine Cheek Teeth: A Simplified Model.

Equine mastication, as well as dental wear patterns, is highly important for the development of treatments in equine dentistry. During the last decades, the stress and strain distributions of equine teeth have been successfully simulated using finite element analysis. Yet, to date, there is no simulation available for dental tooth wear in equines. In this study, we developed a simplified two-dimensional computer simulation of dental wear. It provides a first tentative explanation for the development of the marked physiological inclination of the occlusal surface and for pathological conditions such as sharp enamel points in equine cheek teeth. The mechanical properties of the dental structures as well as the movement of the mandible during the equine chewing cycle were simulated according to previously published data. The simulation setup was optimized in preliminary test runs. Further simulations were conducted varying the lateral excursion of the mandible and the presence or absence of incisor contact during the chewing cycle. The results of simulations showed clear analogies to tooth wear patterns in living equids, including the formation of wear abnormalities. Our analysis indicates that small variations in the pattern of movement during the masticatory cycle, as well as incisor contacts, are leading to marked changes in the occlusal tooth wear patterns. This opens new research avenues to better understand the development of dental wear abnormalities in equines and might have serious implications on captive animal health, welfare, and longevity.

A new cuspidate ptychodontid shark (Chondrichthyes; Elasmobranchii), from the Upper Cretaceous of Morocco with comments on tooth functionalities and replacement patterns

The first articulated dentition of †Ptychodus from Africa is described herein. The specimen, likely coming from the Turonian of the Asfla area (Goulmima region, southeastern Morocco), exhibits a well-preserved lower dental plate of a second-level predator. A new species, †P. maghrebianus sp. nov., is erected herein based on this durophagous dentition characterised by imbricated cuspidate teeth. We employed for the first time in †Ptychodus multiple quantitative analyses and statistical parametric and non-parametric tests to process biometrical data taken from articulated, associated and isolated teeth. The quantitative approach (morphospace analysis) is exploited herein to support the traditional taxonomic identification (qualitative examination) of †P. maghrebianus sp. nov. and to separate it from the similar cuspidate species, †P. mortoni. Morphospace reconstructions confirm a marked lower dental heterodonty (mesio-distal patterns) for both species. The analysis protocol employed here also allows assigning indeterminate teeth as belonging to †P. mortoni. The reconstruction of the entire lower dental plate of †P. maghrebianus sp. nov. shows a cuspidate dentition probably able to reduce tooth damages when crushing thin-shelled prey. Both dental morphologies and tooth wear patterns suggest a peculiar food processing and a diet mainly consisting of bivalves, decapods and small fish for this durophagous predator. Trophic reconstructions of the Turonian ichthyofauna inhabiting the middle to outer ramp environment of the Asfla area emphasize that †P. maghrebianus sp. nov. and the batoid †Tingitanius most likely represented second-level consumers, whereas the sclerorhynchiforms †Asflapristis and †Ptychotrygon represented third-level predators. Top positions within the food web were occupied by larger predaceous elasmobranchs (e.g., †Squalicorax).

P.0340 Effects of interventions for anxiety on peripheral inflammation: a systematic review and meta-analysis

To develop an in situ model for erosive wear research which allows for more clinically relevant exposure parameters than other in situ models and to show tooth site-specific erosive wear effect of an acid challenge of orange juice on enamel.This pilot study included 6 edentulous volunteers wearing full dentures with 13 embedded enamel samples The study consisted of two control runs: habitual diet only for 30 days, and two experimental runs: habitual diet plus 125 ml orange juice four times per day (consumed over 4 m). In the first experimental run subjects were instructed to take the drink in their mouth and promptly swallow it. In the second experimental run subjects take the drink in their mouth and hold each 25 ml for 30 s, moving it around their mouth before swallowing. Sample enamel surface loss was measured using non-contact surface profilometry.Drinking of orange juice additional to the habitual diet, caused significant but low increased erosive wear at buccal, palatal and lingual specimens. Significantly higher levels of tissue loss were found on all surfaces in the swishing experiment but molars (especially occlusal specimens in mandibular molars), palatal specimens sited in upper anterior teeth and lingual specimens in lower anterior teeth were most affected.The model showed clinically relevant patterns of erosive tooth wear as seen clinically in erosive wear patients.The model could have many applications to study clinically erosive wear for specific diets or consumption patterns and to test preventive measures.

Dentition and body condition: tooth wear as a correlate of weight loss in roe deer

BackgroundIn many mammalian species, once the permanent teeth have erupted, the only change to dentition is a gradual loss of tooth surface/height through wear. The crown of the teeth cannot be repaired once worn. When dental crown tissue has been depleted due to wear, the animal is expected to have a suboptimal body condition. We evaluated the role of tooth wear in causing a reduction of physical condition in adult roe deer females (Capreolus capreolus).ResultsThe progressive wearing of the lower cheek teeth was assessed in a Northern Apennines (Italy) population with a new scoring scheme based on objectively described tooth characteristics (morphotypes) being either present or absent. Eviscerated body mass and mandible length, which is a good proxy for body size in roe deer, were related to the tooth wear score by the use of linear regressions. The sum of wear scores for molariform teeth correlated most strongly with body condition (i.e., eviscerated body mass/mandible length), showing the importance of the entire chewing surface for acquiring energy by food comminution, chewing, and digestion. In comparison with individuals of comparable size experiencing minor tooth wear, the body mass of those with the most advanced stage of tooth wear was decreased by 33.7%. This method was compared to the height and the hypsodonty index of the first molar, the most commonly used indices of tooth wear. The sum of molariform wear scoring scheme resulted in a more suitable index to describe the variation in body condition of roe deer.ConclusionsDescribing tooth wear patterns in hunted populations and monitoring at which tooth wear level (and therefore dental morphotype) an animal is no longer able to sustain its physical condition (i.e. when it begins to lose body mass) can be a useful tool for improving the management of the most widespread and abundant deer species in Europe. At the same time, such an approach can clarify the role of tooth wear as a proximate cause of senescence in ungulates.

Tooth wear development in the Australian Aboriginal dentition from Yuendumu: A longitudinal study.

The analysis of dental wear, at both the microscopic and macroscopic scale, is one of the most widely used tools in archeology and anthropology to reconstruct the diet and lifestyle of past human populations. Biomechanical studies have indicated that tooth wear helps to dissipate the mechanical load over the crown surface, thus reducing the risk of tooth fracture. To date, there are only a few studies that have examined functional tooth wear variation in modern humans. Here we propose to study masticatory efficiency through the use of the Occlusal Fingerprint Analysis method, a well-developed digital approach that allows the reconstruction of the occlusal dynamics occurring during mastication. The aim of this study is to provide the first longitudinal quantitative data of molar and premolar macrowear patterns within a functional context. We examined the mixed and permanent dentition of one Australian Aboriginal child (from ages 8 to 17) from Yuendumu, using high-resolution surface scans of dental casts including both upper and lower arches. Our results suggest that the occlusal macrowear patterns of this individual did not significantly change through time. Occlusal contact parameters such as functional area, inclination and direction remain relatively unaltered throughout childhood and adolescence, indicating little change in the masticatory function of this individual. The functional tooth wear pattern in this individual did not change longitudinally indicating the degree of masticatory efficiency has most probably remained unaltered.

Feeding experiments on Vittina turrita (Mollusca, Gastropoda, Neritidae) reveal tooth contact areas and bent radular shape during foraging

The radula is the food gathering and processing structure and one important autapomorphy of the Mollusca. It is composed of a chitinous membrane with small, embedded teeth representing the interface between the organism and its ingesta. In the past, various approaches aimed at connecting the tooth morphologies, which can be highly distinct even within single radulae, to their functionality. However, conclusions from the literature were mainly drawn from analyzing mounted radulae, even though the configuration of the radula during foraging is not necessarily the same as in mounted specimens. Thus, the truly interacting radular parts and teeth, including 3D architecture of this complex structure during foraging were not previously determined. Here we present an experimental approach on individuals of Vittina turrita (Neritidae, Gastropoda), which were fed with algae paste attached to different sandpaper types. By comparing these radulae to radulae from control group, sandpaper-induced tooth wear patterns were identified and both area and volume loss could be quantified. In addition to the exact contact area of each tooth, conclusions about the 3D position of teeth and radular bending during feeding motion could be drawn. Furthermore, hypotheses about specific tooth functions could be put forward. These feeding experiments under controlled conditions were introduced for stylommatophoran gastropods with isodont radulae and are now applied to heterodont and complex radulae, which may provide a good basis for future studies on radula functional morphology.

Judging a reindeer by its teeth: A user-friendly tooth wear and eruption pattern recording scheme to estimate age-at-death in reindeer (Rangifer tarandus).

Reindeer (Rangifer tarandus) have shaped the cultures and provided livelihood to peoples of the Northern Hemisphere for thousands of years. They are still the socio‐economic cornerstone of many northern cultures. Insight into reindeer mortality patterns is important for understanding past human–reindeer interactions and reindeer population fluctuations in relation to climatic and environmental change. Beyond archaeology, assessing the age structures of modern reindeer populations is important for developing wildlife management strategies. This paper presents a quick, non‐destructive and cheap method to estimate age in reindeer in both modern and ancient populations based on tooth wear and eruption patterns of mandibular teeth. We devised the method using a large sample of Svalbard reindeer (Rangifer tarandus platyrhynchus) of known age. We blind‐tested the method and tested its applicability on another known‐age Svalbard reindeer mandible assemblage. The tests demonstrate our methods' user‐friendliness and reliability to generate reproducible, reusable datasets and accuracy in estimating reindeer age‐at‐death.

Palaeoecological differences underlie rare co-occurrence of Miocene European primates

BackgroundThe two main primate groups recorded throughout the European Miocene, hominoids and pliopithecoids, seldom co-occur. Due to both their rarity and insufficiently understood palaeoecology, it is currently unclear whether the infrequent co-occurrence of these groups is due to sampling bias or reflects different ecological preferences. Here we rely on the densely sampled primate-bearing sequence of Abocador de Can Mata (ACM) in Spain to test whether turnovers in primate assemblages are correlated with palaeoenvironmental changes. We reconstruct dietary evolution through time (ca. 12.6–11.4 Ma), and hence climate and habitat, using tooth-wear patterns and carbon and oxygen isotope compositions of enamel of the ubiquitous musk-deer Micromeryx.ResultsOur results reveal that primate species composition is strongly correlated with distinct environmental phases. Large-bodied hominoids (dryopithecines) are recorded in humid, densely-forested environments on the lowermost portion of the ACM sequence. In contrast, pliopithecoids inhabited less humid, patchy ecosystems, being replaced by dryopithecines and the small-bodied Pliobates toward the top of the series in gallery forests embedded in mosaic environments.ConclusionsThese results support the view that pliopithecoid primates preferred less humid habitats than hominoids, and reveal that differences in behavioural ecology were the main factor underpinning their rare co-occurrence during the European Miocene. Our findings further support that ACM hominoids, like Miocene apes as a whole, inhabited more seasonal environments than extant apes. Finally, this study highlights the importance of high-resolution, local investigations to complement larger-scale analyses and illustrates that continuous and densely sampled fossiliferous sequences are essential for deciphering the complex interplay between biotic and abiotic factors that shaped past diversity.

Accuracies and biases of ageing white-tailed deer in semiarid environments

Abstract Context The ability to accurately estimate age of animals is important for both research and management. The two methods for age estimation in ungulates are tooth replacement and wear (TRW) and cementum annuli (CA). Errors in estimated TRW ages are commonly attributed to environmental conditions; however, the influence of environmental variables on tooth wear has not been quantified. Further, the performance of CA in environments with weak seasonality has not been thoroughly evaluated. Aims The study had the following three goals: identify environmental and morphological factors that influenced estimated ages, quantify accuracy of TRW and CA, and develop TRW ageing criteria that minimise error. Methods We used data from harvested (n = 5117) and free-ranging, known-age white-tailed deer (n = 134) collected in southern Texas, USA, to quantify environmental and morphological influences on estimated TRW ages, and assess biases in both methods. Key results We observed substantial variation in age estimates for both TRW and CA. Soil, drought and supplemental nutrition had minor effects on tooth wear, insufficient to alter age estimates by ≥1 year. Body mass and antler size influenced age estimates for TRW only for extreme outliers. Both methods were biased and tended to under-estimate ages of adult deer, especially TRW. Wear on the first molar was most correlated with the known age (r2 = 0.78) and allowed biologists to correctly place known-age deer into age classes of 2, 3–5, and ≥6 years old 72%, 73% and 68% of the time, an improvement compared with the 79%, 48% and 28% accuracy from pooled TRW. Conclusions We observed substantial inter- and intra-individual variation in tooth-wear patterns that became more pronounced in older deer. Individual variation had a greater influence on TRW ages than did environmental covariates, whereas CA ages appeared unaffected by environment. Although variable, age estimates were ±1 year of the true age 87% and 93% of the time for TRW and CA respectively. Implications Managers, ecologists and epidemiologists often incorporate ages into population models. The high inter-individual variation in estimated ages, the tendency to underestimate ages of older deer, and the ageing method need to be considered.

Brief notes on newly discovered teeth of the hybodontiform shark Strophodus dunaii (Szabó et Főzy, 2020)

Genus Strophodus has been considered as a junior synonym of genus Asteracanthus for a long time. Th e discovery of an articulated skeleton of Asteracanthus ornatissimus resurrected the genus Strophodus, which is recommended to include all species previously referred to Asteracanthus, except for those described by isolated dorsal fi n spines. Th is stands for Strophodus dunaii comb. nov. as well, which was established for isolated tooth remains. A new tooth and casts of several previously unknown teeth referable to this species are described here in detail. Notes on future tooth wear pattern analyses in Strophodus spp. are also discussed. With 19 fi gures.

Patterns of telomere length with age in African mole-rats: New insights from quantitative fluorescence in situ hybridisation (qFISH).

Naked mole-rats Heterocephalus glaber (NMRs) are the longest-lived rodent and also resist the normal signs of senescence. In a number of species, cellular ageing has been correlated with a reduction in telomere length, yet relatively little is known about telomeres and their age-related dynamics in NMRs and other African mole-rats. Here, we apply fluorescence in situ hybridisation (FISH) to quantify telomeric repeat sequences in the NMR, the Damaraland mole-rat, Fukomys damarensis (DMR) and the Mahali mole-rat, Cryptomys hottentotus mahali (MMR). Both terminal and non-terminal telomeric sequences were identified in chromosomes of the NMR and DMR, whilst the MMR displayed only terminal telomeric repeats. Measurements of tooth wear and eruption patterns in wild caught DMRs and MMRs, and known ages in captive bred NMRs, were used to place individuals into relative age classes and compared with a quantitative measure of telomeric fluorescence (as a proxy for telomere size). While NMRs and MMRs failed to show an age-related decline in telomeric fluorescence, the DMR had a significant decrease in fluorescence with age, suggesting a decrease in telomere size in older animals. Our results suggest that among African mole-rats there is variation between species with respect to the role of telomere shortening in ageing, and the replicative theory of cellular senescence.

Examination on the wear process of polyformaldehyde gears under dry and lubricated conditions

This study presents the results of detailed wear process examination on polyformaldehyde gears under both dry and lubricated conditions. A multi-purpose durability test rig was employed to study the wear performance of polyformaldehyde gear pairs. The wear behaviors of polyformaldehyde gears under dry and oil-lubricated operating conditions were characterized via measurements of gear tooth surface micro-topography and tooth profile deviation. Under the dry running condition, a hump and a gully appear on the tooth surface in the pitch line area of the driving gear and the driven wheel, respectively. The largest amount of wear was observed around the tooth root of the driving gear. However, the gear tooth wear pattern with lubrication is different from that under the dry running condition.

Date of death of domestic caprines assessed by oxygen isotopic analysis of developing molars: Implications for deciphering the calendar of pastoral activities in prehistory

The assessment of the date of death (DOD) of animals found in archaeological sites provides insights into the exploitation of their environment by ancient mobile and sedentary populations. In an attempt to overcome the limitations of the traditional methods, we determine the DOD of domestic caprines using sequential oxygen isotope analysis of developing tooth enamel. We built a reference set composed of developing molars from 14 modern sheep and goats from Western and Central Mongolia with known DOD. The teeth were sequentially sampled, and δ18O sequences were modelled using a cosine function in order to position the lowermost δ18O value (δf) within the annual cycle. We found that δf values are strongly linearly correlated with the DOD (R2 = 0.88), allowing the use of this regression to estimate the DOD with a precision of about ±25 d (1σ). This method was applied to determine the DOD of caprines found in two graves in the Xiongnu necropolis of Egiin Gol, Mongolia. We determined a slaughter date of late July and late September for the two graves, respectively, suggesting that burial occurred during the warm season. By combining this information with age at death assessed using tooth eruption stages and tooth wear patterns, we were also able to determine that caprine birth occurred mostly in April and was strongly controlled within this seasonal window by the herders, much like in Mongolia today.

Diet reduces the effect of exogenous grit on tooth microwear

Exogenous grit adherent to the surface of food items and food fracture properties have each been considered important factors contributing to pattern and degree of tooth wear in mammals. However, the interactions between these two factors in generating distinctive microwear textures have remained understudied. Here the authors revisit in-vitro results from simulated chewing to explore how adherent grit and physical properties of foods act together to create dental microwear textures on occlusal enamel surfaces. Results suggest that the effect of exogenous grit on microwear texture is dependent on the material properties foods to which they adhere. Grit in the absence of food causes more complex microwear surface textures than foods covered with similar levels and types of grit (for a given number of chews and angle of approach between opposing teeth). Different foods covered in grit also yield different complexity values. Grit-laden, pliant meat, for example, results in a less complex texture than does resistant, grit-laden raw carrot. This work implied that tooth wear assessment can benefit from considering grit load and food material properties together.