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

Tooth wear as a means to quantify intra-specific variations in diet and chewing movements

9 pagesInternational audienceIn mammals, tooth function, and its efficiency, depends both on the mechanical properties of the foodand on chewing dynamics. These aspects have rarely been studied in combination and/or at the intraspecificlevel. Here we applied 3D dental surface texture analysis to a sample of field voles (Microtusagrestis) trapped from Finnish Lapland at different seasons and localities to test for inter-populationvariations. We also explored intra-individual variation in chewing dynamics by analysing two facetson the second upper molars. Our results confirm that the two localities have similar environments andthat the voles feed on the same items there. On the other hand, the texture data suggest that diets areseasonally variable, probably due to varying concentrations of abrasives. Lastly, the textures on thebuccal facets are more isotropic and their direction deviates more from the mesial chewing directionthan the lingual facets. We interpret these results as reflecting food, rather than chewing, movements,where food particles are more guided on the lingual side of the molars. This has implications for theapplication of dental microwear analysis to fossils: only homologous facets can be compared, evenwhen the molar row seems to constitute a functional unit

Post-mortem enamel surface texture alteration during taphonomic processes—do experimental approaches reflect natural phenomena?

Experimental approaches are often used to better understand the mechanisms behindand consequences of post-mortem alteration on proxies for diet reconstruction.Dental microwear texture analysis (DMTA) is such a dietary proxy, using dental wearfeatures in extant and extinct taxa to reconstruct feeding behaviour and mechanicalfood properties. In fossil specimens especially, DMTA can be biased by post-mortemalteration caused by mechanical or chemical alteration of the enamel surface. Herewe performed three different dental surface alteration experiments to assess the effectof common taphonomic processes by simplifying them: (1) tumbling in sedimentsuspension to simulate fluvial transport, (2) sandblasting to simulate mechanicalerosion due to aeolian sediment transport, (3) acid etching to simulate chemicaldissolution by stomach acid. For tumbling (1) we found alteration to be mainlydependent on sediment grain size fraction and that on specimens tumbled with sandfractions mainly post-mortem scratches formed on the dental surface, while specimenstumbled with a fine-gravel fraction showed post-mortem formed dales. Sandblasting(2) with loess caused only negligible alteration, however blasting with fine sand quartzparticles resulted in significant destruction of enamel surfaces and formation of largepost-mortem dales. Acid etching (3) using diluted hydrochloric acid solutions inconcentrations similar to that of predator stomachs led to a complete etching of thewhole dental surface, which did not resemble those of teeth recovered from owl pellets.The experiments resulted in post-mortem alteration comparable, but not identical tonaturally occurring post-mortem alteration features. Nevertheless, this study servesas a first assessment and step towards further, more refined taphonomic experimentsevaluating post-mortem alteration of dental microwear texture (DMT)

Dental wear patterns reveal dietary ecology and season of death in a historical chimpanzee population

Dental wear analyses have been widely used to interpret the dietary ecology in primates. However, it remains unclear to what extent a combination of wear analyses acting at distinct temporal scales can be beneficial in interpreting the tooth use of primates with a high variation in their intraspecific dietary ecology. Here, we combine macroscopic tooth wear (occlusal fingerprint analysis, long-term signals) with microscopic 3D surface textures (short-term signals) exploring the tooth use of a historical western chimpanzee population from northeastern Liberia with no detailed dietary records. We compare our results to previously published tooth wear and feeding data of the extant and continually monitored chimpanzees of Taї National Park in Ivory Coast. Macroscopic tooth wear results from molar wear facets of the Liberian population indicate only slightly less wear when compared to the Taї population. This suggests similar long-term feeding behavior between both populations. In contrast, 3D surface texture results show that Liberian chimpanzees have many and small microscopic wear facet features that group them with those Taї chimpanzees that knowingly died during dry periods. This coincides with historical accounts, which indicate that local tribes poached and butchered the Liberian specimens during dust-rich dry periods. In addition, Liberian females and males differ somewhat in their 3D surface textures, with females having more microscopic peaks, smaller hill and dale areas and slightly rougher wear facet surfaces than males. This suggests a higher consumption of insects in Liberian females compared to males, based on similar 3D surface texture patterns previously reported for Taї chimpanzees. Our study opens new options for uncovering details of feeding behaviors of chimpanzees and other living and fossil primates, with macroscopic tooth wear tracing the long-term dietary and environmental history of a single population and microscopic tooth wear addressing short-term changes (e.g. seasonality)

Forage silica and water content control dental surface texture in guinea pigs and provide implications for dietary reconstruction

Recent studies have shown that phytoliths are softer than dental enamel but still act as abrasive agents. Thus, phytolith content should be reflected in dental wear. Because native phytoliths show lower indentation hardness than phytoliths extracted by dry ashing, we propose that the hydration state of plant tissue will also affect dental abrasion. To assess this, we performed a controlled feeding experiment with 36 adult guinea pigs, fed exclusively with three different natural forages: lucerne, timothy grass, and bamboo with distinct phytolith/silica contents (lucerne < grass < bamboo). Each forage was fed in fresh or dried state for 3 weeks. We then performed 3D surface texture analysis (3DST) on the upper fourth premolar. Generally, enamel surface roughness increased with higher forage phytolith/silica content. Additionally, fresh and dry grass feeders displayed differences in wear patterns, with those of fresh grass feeders being similar to fresh and dry lucerne (phytolith-poor) feeders, supporting previous reports that "fresh grass grazers" show less abrasion than unspecialized grazers. Our results demonstrate that not only phytolith content but also properties such as water content can significantly affect plant abrasiveness, even to such an extent that wear patterns characteristic for dietary traits (browser-grazer differences) become indistinguishable

An anatomical study of the dorsal and ventral nasal conchal bullae and middle nasal conchae in normal Shetland ponies: Computed tomographic anatomical and morphometric findings

Abstract Equine paranasal sinuses are susceptible to inflammation. Insufficient drainage through the nasal passages and meatus may lead to the accumulation of inspissated purulent discharge. Particularly in ponies, these anatomical structures are suspected to be relatively small. To date, there are no reports considering the morphology of nasal conchal bullae in small horse breeds such as Shetland ponies. The aim of the present study was to evaluate the size of the conchal bullae and the medial nasal conchae of Shetland ponies and their relation to the skull dimension using computed tomography. Reconstructed images of healthy adult heads of Shetland ponies were used. Linear skull measurements as well as two cranial indices of the head dimensions were taken. Length, width and height of the dorsal and ventral conchal bullae and the medial nasal conchae were measured in relation to the skull and compared with the data of skulls of large breed horses. The anatomical proportions of pony heads were characterized by a smaller cranial index and a greater nasal index than those of large breed horses. Shetland ponies showed a longer cranial length compared with the nasal length. Heads are consistently smaller, and the relationship of the bullae to the head length was also smaller than those measured in large breed horses. A negative correlation between the head and bullae size was found. In conclusion, this study suggests that Shetland ponies have distinguishing proportions of the head. These findings are relevant for clinical examination and surgical treatment of equine sinus disease in those breeds