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Objective:To investigation the veracity of orientation on modified upright lateral cephalometric radiographs. Methods:Fifty upright lateral cephalometric radiographs were analysed randomly.Twenty-three subjects,who had standard radiographs, were taken with modified technique. The chracterics both of radiographs were compared. Results:The orientations of porion?FH plane and the superimpositions of left and right gonion point on modified standard radiographs were more veracity. Conclusion:The veracity of orientation on upright lateral cephalometric radiographs can be improved.
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Objective:To obtain the morphological data of permanent teeth excavated from the Long County in Shaanxi Province about 2 000 years ago.Methods:Morphological methods were used to measure all teeth of 59 human skulls excavated from the Long County in Shaanxi Province about 2 000 years ago and conserved in Chinese Academy of Science.The information included length of tooth,height of dental crown,length of dental root,breadth of the dental crown,thickness of the dental crown,breadth of the dental neck and thickness of the dental neck.The data were analyzed by SPSS 13.0 software.Results:Length of tooth,height of dental crown,length of dental root,breadth of the dental crown,thickness of the dental crown,breadth of the dental neck and thickness of the dental neck of all teeth of 59 human skulls were reported.Conclusion:It suggests that the measured data may be useful in anthropological research.
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Objective:To observe the position of the third molar in the neolithic adults about 6 000 years ago.Methods:On the basis of the maxillary and mandibular specimens preserved in Banpo museum,200 maxillary and mandibular specimens with 383 third molars,187 maxillary and 196 mandibular,were observed for the eruption of the third molar.The teeth in the non-eruption group were further divided into impact group and congenital absent group according to the third molar germ presence testified by X ray.Results:The congenital absent rates of maxillary and mandibular third molar were 26.74% and 17.35%,while the impact rates of maxillary and mandibular third molar were(2.67%) and 14.79% respectively.Conclusion:Both the congenital absent rate and the impact rate of the third molar in neolithic era adults are lower than those in modern,the impact and congenital absence of the third molar are part of degradation of masticatory organ with whole humanity progressing.
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Objective: To study the influence of anterior crossbite on the position and morphology of teeth. Methods: 81 teenagers with permanent dentition and anterior crossbite were in volved in group 1 and 95 teenagers in permanent dentition without anterior crossbite in group 2. The teeth in both groups were compared on their position and morphology. Results:① The percentage of ill-positioned teeth in maxilla in group 1 and in group 2 was 14.0% and 8.8% respectively (P
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砄bjective: To assess interexaminer errors in traditional cephalometric analysis so as to improve the accuracy . Methods : Ten cephalometric radiographs were selected randomly and 12 angular and 5 liner parameters were measured by 5 orthodontists in one week according to the original landmarks. The results were quantified with that of computer based. Results: The mean errors of some measurements were larger than 0.5, such as SL,GoGn SN, SE,FMA,FMIA,OP SN, 1 1 ,IMPA and SNA,while only those of SL and GoGn SN were larger than 1.0. Conclusion: Statistical significant differences are found in the The errors of measurements which need assisted line among the examiners but not found in the errors between angle measurements and liner measurements?
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Objective:To determine the differences of age, eruption sequence and gender of permanent teeth in children and adolescents in Xi'an, China. Methods:Cross-sectional data on permanent teeth eruption were collected from children aged 3~15 in pre-school, primary and secondary school. The subjects were drawn by multistage random sampling from the school registers. There were 6 712 subjects involved in present survey, including 3 604 boys and 3 108 girls. The data were subjected to probit regression analysis. Results:The median age of tooth eruption in girls was earlier than that in boys. Although the range of years during which the permanent teeth erupted was similar in both sexes, i.e. 6~12 years, the sequence of the tooth eruption was differed. All mandibular teeth, with the exception of first and second premolars in both males and females, tended to erupt earlier than their maxillary counterparts. Conclusion:The findings seem to be different from earlier studies done in the other parts of China.
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0.05 ).The occlusal caries (73.08%) was more than the interproximal(50.00%).Conclusion:The prevalence of dental caries in the people at the Neolithic Age was lower than that in modern people.