| It's known to all that it's highly effective to choose the best time for orthodontics. Many scholars in the field have been doing much scientific research work for disclosing the relationship between the growth characteristics of different body positions from different point of views in order to predict the best time for orthodontics for each individual. The results were not always identical due to the sample sources or methods adopted.[ Objective] To study the intrinsic relationship between wrist,cranonium and some teeth and lay a solid theoretical foundation for orthodontists to predict the development for each individual by studying the development of wrist , cranonium and some teeth among the children aged 7-16 in Nanjing area.Part I Correlation studies of teeth development and wrist maturity[Materials and methods] 367 patients aged between 7-16 who came to the department of orthodontics of Jiangsu Stomatological Hospital for the first time were selected, among whom 142 were males, 225 females. They were divided into E, F, G and H groups according to Demirjian teeth development stages after their panoramic X-ray pictures of tooth were taken. X-ray pictures of left hand wrist were taken and bone maturity were scored for each individual, according to "Chinese Hand Wrist Development Standards CHN Method". By referring to different bone development norm for different gender/age groups, bone age were decided. At the same time, by referring to Grave methods, adolescence sudden increase stages were divided, according to hand wrist calcification mark. The different stages of teeth development of both males and females were analyzed for the sameness and difference of ages and bone age and their continuity degrees with the stages of wristmaturity.[Results] The children's teeth developed more slowly in different stages than their bones, suggesting that the skeleton of the children at present developed in an earlier stage than it did in the past, according to the CHN Method Standards formulated in the 1990s. There were differences between males and females.[Conclusion]The teeth and skeleton of females developed more quickly than the males'. Teeth and skeleton have their own development patterns, but mandibular canine could be chosen to predict the sudden increase in adolescence development with the help of other physiological maturity marks. Chronologic age is superior to the skeletal age in evaluating the development of mandibular canine.Part II Bone age were applied to judge the development characteristics of cranonium.[Materials and methods] 458 patients aged between 8-16 who came to the department of orthodontics of Jiangsu Stomatological Hospital for the first time were selected, among whom 172 were males, 286 females. They were grouped, according to the results of individual bone age and sex from the first part of study. After lateral x-ray film were taken, SIDEXIS software was adopted to measure the angles of cranonium base and mandible and length marks. SPSS 10.0 was adopted to analyze the sudden increase of each growth mark and their skeletal age period of significant growth.[Results] The growth time and amount of anterior cranonium base were both less than those of posterior cranonium base; the growth time and amount of maxillary were both less than those of mandible? there were no significant differences among angle marks such as ArGoGn, SNA, SNB and NSD. In terms of the growth characteristics of mandibular ramus, body and mandibular length, there were differences betweensexes, positions, suggesting the sudden increase of growth and stop for females were both earlier than those for males, and the rapid growth period of cranonium was earlier than those of wrist and certical. [Conclusion]Chronological age is the best plane to evaluate anterior cranonium, and anterior cranonium base is the best plane to evaluate the growth of cranonium. The mandible has greater potent than maxillary. |
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