The Relative Analysis Of Human Tooth Wear From Three Thousand Years Ago To Now In Xi'an Region

OBJECTIVEThis experiment collected and tidied up all the unearthed specimens at threearchaeological sites including: the Xi Zhou period Graveyard of ShaoLinyuan, Changan District, Xi'an(3000BC), The Shan ren pottery cave site of Qin shihuang's mausoleum, Lintong District, Xi'an(2000BC) and the inhabitant site ofTang dynasty, Changan District, Xi'an(1000BC), observed and recorded thetooth wear level of incisor ridges and occlusal surfaces, analyzed the above threeunearthed teeth specimens'tooth wear level, refered to the average level ofmodern people's tooth wear then contrasted and analyzed the four periodspeople's tooth wear level, finally summarized the evolutional regularity of toothwear from three thousand years ago to now, furthermore, the influencing factorswhich caused different level of different periods of people's tooth wear werediscussed, this could accumulate some research materials for contrast study ofdifferent social periods and oral preventive medicine.METHODSThis experiment adopted the method of crosssectional study of descriptiveepidemiology, according to the standard of age division of〈The method ofbody's measure〉(1984 edition) edited by Wu Ru kang, etc. The three batches of specimens and 416 modern peoples were divided into six groups: under 23 yearsold group, 24～35 years old group, 36～45 years old group, 46～55 years oldgroup, 56～65 years old group and over 66 years old group. The observationstandard adopted Smith.H 5 class standard of tooth wear which is fit for ancientinhabitants of huntergathering and agricultural society, excluded nubs,largeresidual crowns,impacted teeth and porcelain crowns ,observed and recordedevery tooth's tooth wear degree , measured each data for three times, took amean value, inputted all data into computer according to different age groups,then made a statistical analysis.RESULTS1.By means of Wilcoxon signed rank test, we compared the average degreesof tooth wear of the same tooth of 3000,2000,1000 years ago and the currentsample respectively. The findings showed that there was no significantdifference about tooth wear of the same tooth in the four different periods.2.The average degrees of tooth wear of 3000, 2000, 1000 years ago andcontemporary samples were 2.24,2 .01,1 .79 and 1.51, which were calculated byweighting method.3.Inspected two independent samples using the Wilcoxon rank sum test toinvestigate the significant difference of teeth wear between all age groups foreach tested period. The results showed that: for each period between differentage groups, there was a significant difference about the level of tooth wear (P<0.05), and tooth wear became worse with the increase of age.4.Using MannWhitney U test, we testeded the difference of tooth wear infour periods based on age, upper and lower jaw. The results revealed that therewas a significant difference in the four periods of all ages. With the exception ofindividual tooth, tooth wear in group of 3000 was greater than in 2000 group, 2000 group was greater than 1000 group, while the group of 1000 was greaterthan the current group.5.The difference of tooth wear between the anterior teeth and posterior teethshowed that: the average degree of tooth wear of anterior teeth of upper andlower jaws were greater than posterior teeth (ratio greater than 1) in group of3000 and group of 2000? 67﹪of the ratio in group of 1000 > 1? only 50% ofthe ratio in the current group > 1, And the ratio became smaller with the advanceof time. Using chisquare test, the results showed that tooth wear between theanterior and posterior teeth had a significant difference in all age groups ofdifferent times.CONCLUSION1.Age is the chief facter for tooth wear, and agingrelated changes exists inthe four different stages of people, it represents that the tooth wear aggravateswith the increase of age in each stage.2.The average tooth wear degree of the same tooth between the left and theright in the upper or lower jaw has no significant difference in every period of.time.3. Analyzing the tooth wear characteristics of the four stages, we find that thetooth wear varies with the progress of time, human tooth wear decreases withthe social development and time progress.4.The anterior and posterior tooth wear difference index is greatly differentbetween different stages, there are also timerelated changes, That is, with theprogress of society, the condition that tooth wear difference index is larger than1 reduced, this indicates that the tooth wear level of anterior teeth and posteriorteeth is becoming equal, the phenomenon that the anterior teeth wear is worsethan the posterior teeth decreases. On the orther side, it also indicates the anterior teeth wore more in ancient people.