Morphological Study On Evolution Of Mandible Posterior Part Of Human During6,000Years In Shaanxi

Material：The study is divided into six groups:Mandible unearthed in Xi’an Shaanxi Province，Neolithic sites,6000years ago，existing in Banpo Museum,83cases;Mandible unearthed in Shangluo Shaanxi Province，Xia Dynasty sites,4000yearsago，existing in department of cultural heritage, Northwest University,5cases；Mandible unearthed in Xi’an Shaanxi Province，Xi zhou Dynasty sites,3000yearsago existing in the Shaanxi Institute of Archaeology,8cases;Mandible unearthed in Guanzhong eastern region Shaanxi Province，Qin Dynastysites,2000years ago，existing in department of cultural heritage, Northwest University,49cases；Mandible unearthed in Chang’an Shaanxi Province，Tang Dynasty sites,1000yearsago existing in the Shaanxi Institute of Archaeology,8cases;Mandible in modern group of Shaanxi Province, existing in department of anatomy,Fourth Military Medical University,50cases Objective: The study reported mandibular posterior part measurement data andmandible molar eruption proportion of different ages, since6000years ago in ShaanxiProvince. The result discussed the trends of morphological evolution of mandiblePosterior part in Shaanxi province and influencing factors of mandibular third molareruption which offer data and references for further research on human mandibleevolution.Methods: The measure is independently made by the author referring to the physicalanthropology, oral anatomy and physiology. Mandible measured in daylight and twiceeach measurement and project to measure averaged.If the result differ than0.5mm or1degree then re-measure.Result: Morphology comparison of mandible Posterior part shows: Mandibularposterior part thickness, the length of mandible and the length of retromolar space isshortened with time and that the gonial angle and the crystal-marginal angle is prolongedwith time which result from the masticate organ degradation of the mandible deficiencygrowth.Morphology of mandibular posterior part of people groups in different ages eruptionof third molar grouping shows: Longitudinal comparison with mandibles in the same erashows that the length of mandible and the length of retromolar space in Eruption group aresignificantly different from that of Impacted group and Congenital absence group.Morphology of mandibular lingula in different ages shows:The nodular is the mostprevalent in people in6,000years group. The2,000years group takes the same proportionof triangular truncated and nodular. The triangular is the most prevalent in people inmodern group.Reported morphology of mandibular posterior part data,molar eruption data,morphology of mandibular lingula of4000years、3000years、1000years group.Conclusion: Morphology study of mandibular posterior part shows: mandibularposterior part became thinner, smaller length, angle increases as human evolution.Mandibular molars eruption of posterior segment changes over time tends to decreasethe proportion of abnormal eruption (ectopic eruption, impaction, missing); The length of the mandible and mandibular third molar eruption close correlated.Morphology of mandibular lingula was deduced the lingula trends to bulge shape ashumans evolved.