| The purpose of this study was to assess the differences in dental pathology, enamel thickness and density, tooth trace elements and tooth stable isotopes between hunter-gatherers and agriculturists in Shaanxi Province in order to increase our knowledge about changes in tooth structure, tooth composition and dental pathology during the transition from hunting-gathering to agricultural economy, and correlated them with dietary patterns and subsistence.Investigation was carried out on the skeletal remains of 79 adult individuals (about 6,000 years BP) who were excavated from Banpo archaeological sites and 62 adult individuals (about 1,000 years BP) excavated from archaeological sites of Tang dynasty. The samples analyzed were dental remains of 1007 permanent teeth (490 upper teeth and 517 lower teeth) from Banpo sites and 631 permanent teeth (328 upper teeth and 303 lower teeth) from Tang sites. The sex was determined based on the pelvic morphology and the classic macroscopic aspects of the skulls and jaws. Age-at-death was established following Brothwell's criteria on dental attrition and cranial suture fusion. The samples were classified into 4 age groups according to age-at-death: 17-25 years, 26-35 years, 36-45 years, and 45+ years. Dental pathology, enamel thickness and density, tooth trace elements and tooth stable isotopes were examined and recorded according to authoritative criterion and methods. The main results were as follows:In the aspect of dental pathologies, the present study determined the frequency and distribution of dental caries and tooth wear between hunter-gatherers and agriculturists in Shaanxi Province. More than 41% subjects showed at least one carious lesion, and the percentage of total carious lesions was 5.7% among hunter-gatherers from Banpo sites. However, the proportion of teeth with caries (14.6%) and the prevalence of individuals with at least one carious lesion (62.9%) among agriculturists from Tang sites were found significantly higher than those among hunter-gatherers withχ2=6.207 and P=0.013;χ2=37.324 and P=0.001.In the aspect of enamel thickness and density, the maxillary second premolars of hunter-gatherers excavated from Banpo sites and agriculturists from Tang sites were scanned by Micro-CT and the enamel thickness and density was evaluated and recorded. There was no significant difference (P﹥0.05) in the enamel thickness and density of the upper second premolars between hunter-gatherers and agriculturists in Shaanxi Province. Analysis by tooth region demonstrated that the distribution of enamel thickness and density over a tooth corresponded closely to the functional demands of mastication and dietary preferences. The enamel thickness and density at cusps observed in this study was higher than that at the occlusal basin. Functional (lingual) cusps/slopes and distal surfaces possessed thicker enamel than non-functional (buccal) cusps/slopes and mesial surfaces.In the aspect of tooth trace elements, tooth trace elements were measured using a spectra IRIS Advantage atomic absorption spectrophotometer including Sr, Cu, Fe, Mn, Ca, P, Mg, Zn and Ba. Sr, Cu, Fe and Ba content of teeth among agriculturists excavated from Tang sites was higher than that among hunter-gatherers from Banpo sites, while Zn content of teeth was lower than that among hunter-gatherers from Banpo sites. There was no significant difference (P﹥0.05) in the content of other tooth trace elements between hunter-gatherers and agriculturists in Shaanxi Province.In the aspect of tooth stable isotopes, dentin collagen was extracted for stable isotope analysis, and carbon and nitrogen stable isotopes were assessed by MAT-251 mass spectrometer. The carbon/nitrogen ratio was significantly different (P﹤0.05) between hunter-gatherers (3.15±0.03) and agriculturists (3.08±0.04) in Shaanxi Province. Dentin collagen isotopic compositions showed that the values ofδ13C andδ15N and C4 ratio among hunter-gatherers excavated from Banpo sites were higher than those among agriculturists from Tang sites (P﹤0.05), while C4 ratio was lower than that among agriculturists from Tang sites (P﹤0.05).In summary, with the emerging of agriculture, diet rich in carbohydrates increased, and caries became more and more prevalent, while dental wear was unremarkable. In addition, changes of tooth trace elements and tooth stable isotopes were obvious during the transition from hunting-gathering to agricultural economy. However, there was no significant difference in the enamel thickness and density between hunter-gatherers and agriculturists in Shaanxi Province. This study analyzed the differences in dental pathology, enamel thickness and density, tooth trace elements and tooth stable isotopes between hunter-gatherers and agriculturists in Shaanxi Province, increased our knowledge about changes in tooth structure, tooth composition and dental pathology during the transition from hunting-gathering to agricultural economy, and based on archaeological evidence and anthropological records, correlated them with dietary patterns and subsistence.
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