Activity: Participating in or organising an event types › Organisation and participation in conferences, workshops, courses, seminars
1. CHEWING MACHINE AND TOOTH WEAR: HOW PLANT MATERIALS AND GRIT AFFECT TEETH2. MACROSCOPIC TOOTH WEAR AND DIETS OF EXTANT AND FOSSIL XENARTHRANS (MAMMALIA, XENARTHA)
1. Karme, A., Rannikko, J., Bertin, T., Clauss, M., Fortelius, M., 2014. CHEWING MACHINE AND TOOTH WEAR: HOW PLANT MATERIALS AND GRIT AFFECT TEETH. Society of Vertebrate Paleontology 2014 Program and Abstracts.
2. Saarinen, J., Karme, A., 2014. MACROSCOPIC TOOTH WEAR AND DIETS OF EXTANT AND FOSSIL XENARTHRANS (MAMMALIA, XENARTHA). Society of Vertebrate Paleontology 2014 Program and Abstracts.
1. CHEWING MACHINE AND TOOTH WEAR: HOW PLANT MATERIALS AND GRIT AFFECT TEETH
In the last few years, the causes of tooth wear have again become a subject of active discussion. While progress may still be possible through improved analysis of existing data, the most urgent need now is for experimental work. Instead of using real animals and facing the limitations of standardization and repeatability, we introduced some time ago a simple chewing machine for wearing real teeth under fully controllable conditions. We have previously shown that attrition and abrasion can be produced according to predictions of traditional wear theory using artificial abrasives. Here we report results from experiments with real plant material with and without added grit.
The plant materials used in this research consist of pelleted diet preparations of increasing abrasiveness (as determined by acid insoluble ash content), consisting of lucerne (L; lowest abrasiveness, very few phytoliths), grass (G; higher abrasiveness, more phytoliths), a mixture of grass and rice hulls (GR; again increased abrasiveness due to high phytolith content in rice hulls), and the grass/rice hull-mixture with added grit (GRS). Unlike in actual animal experiments, we were also able to test for attrition, wear caused by direct tooth-tooth contact in the absence of food materials. Real horse teeth were immersed in a relatively thick and saline plant slurry, which was turbidated to ensure material circulation. The chewing machine is able to perform 260 cycles per minute (4-5 times the speed of a horse) with controlled and constant movement and force. In this study, tooth pairs were chewed for 6.5 hours resulting in 100 000 repetitions, equal to several days in horse time.
Our results show clear differences between attrition and abrasion. At the scale of dental microwear, attrition is characterized by pitting of polished areas, while abrasion is characterized by striation. At the macroscopic level quantitative analysis based on 3D scanning shows that attrition causes development of distinct, planar facets while abrasion causes facet-less, curved wear surfaces in this machine.
2. MACROSCOPIC TOOTH WEAR AND DIETS OF EXTANT AND FOSSIL XENARTHRANS (MAMMALIA, XENARTHA)
Xenarthra is one of the major superorders of placental mammals and it comprises a major group of the large terrestrial mammal fauna in South America during the Cenozoic and in North America during the Pleistocene. Understanding dietary paleoecology of Xenarthra would provide information not only about the dietary adaptations of the species but also about how their diets have varied according to changing resources and environmental conditions. The usually simple and reduced tooth morphology of the xenarthrans, lacking enamel, has rendered dietary analyses based on their fossil teeth challenging. In particular the problem is analyzing paleodiets of xenarthrans using a consistent methodology which would give results comparable to mammals with other kinds of tooth morphologies. We introduce a new method based on macroscopic tooth wear morphology easily applicable for fossil and extant xenarthran teeth. Relief on the occlusal surface of xenarthran teeth forms during the tooth wear as a result of uneven wear of harder dental materials (durodentin) and softer dental materials (vasodentin). The wear-resistant durodentin edges of the teeth wear down more heavily as a result of abrasive food materials (for example grass) causing lower relief of the tooth surface. The new method is similar to mesowear analysis and it is based on measuring the relief of the worn molariform teeth of xenarthrans as antero-posterior angles by placing the tip of the angle at the bottom of worn vasodentin valleys and the sides of the angle as tangent to durodentin edges of the teeth. The wider the measured angles are the lower the worn tooth relief is, which indicates increasingly abrasive diet. This method gives consistent, comparable information about the relief of the worn tooth surface regardless of differences in the primary morphology of the teeth. We have previously successfully applied this method for the dietary analysis of proboscideans. The results based on our angle-based method of recording tooth surface relief correlate with dietary analyses based on stable isotopes from xenarthran teeth. The work was funded by the Finnish Doctoral Program in Geology and the Waldemar von Frenckells Stiftelse.