Cephalometric Study Of Craniofacial Morphology By Computer On People With Normal Occlusion In Chongqing

Since 1931,when Broadbent[1] introduced his cephalolometer ,a new period began in orthodontics.Cephalograms can also help the orthodontist determine the changes associated with growth and orthodontic treatment. As treatment mechanics are becoming more effective, there has been an increased emphasis on the cephalometric analysis ,both in diagnostic and treatment results.As a result, many Cephalometric anylatical method have been introduced since 1931,for example:Downs[2],Tweed[3],McNamara[4], Wylie[5], Steiner[6],Holdaway[7]anylatical method and so on.Cephalometric norms for different racial groups have previously been established in many studies. Most investigators have concluded that there are significance differences between the ethnic and racial groups[8,9,10,11]. Objective:1,In order to establish the normal value of hard and soft tissues of Chongqing and to reveal the regular patterns and characteristics concerning the craniofaicial morphology . 2,To study the differences of repetition of landmarks identification on the computer monitor and the effect of X-radiographs quality on the repetition of landmarks identification through tracing landmarks by hand on the computer. Method : 1,55 students with early permanent dentition and 58 students with permanent dentition were selected as the samples .The cephalometric images images were scanned into a computer and the images were impoerted into the program.The cephalometric analysis were automated by the computer.The cephalometric analysis on hard and soft tissues features was used in this study . Correlational analysis for SNA,SNB,ANB,FMA,FMIA were caculated.2,30 lateral cephalograms were selected by random,The cephalometric X- radiographs were scanned into a computer and the images were copied. the landmarks were identified by two orthodontists on the computer monitor by twice. The dates were obtained and then the differences were studied.At the same time, in order to get more clearly images ,the quality of copied images were enhanced in the Photoshop 6.0.Each of the 60 images was traced two times ,the X,Y coordinates and other correlated measurements for each landmarks were recorded. Results: 1, The normal values of hard and soft tissues for permanent dentition and early permanent dentition on normal occlusal people of Chongqing were established and compared with that of other areas . 2,There were differences inter-operator and intra-operator on the coordinationï¼›There were significance differences between the dates of the abscissas and ordinate of the landmarks in some of the landmarks; After the quality of copied images were enhanced ,there were no differences on hard tissues of landmarks of average errors ,but there were significance differences on soft tissues of landmarks of average errors as well as two of the measurements;There were errors with eyes on the identification of X,Y coordinates. Conclusions : 1,We found that hard and soft cephalometric measurement values are various in sexual and races and regional population. 2,The repetition of identified landmarks related to understanding definition of the landmarks,location of the landmarks,the landmarks identification and the quality of the X-rays; Most of the effects of X-radiographs quality on the computer-aided cephalometry were showed on soft tissues and there are less effects on hard tissues.