The Study On Creating The Differential Templates For Shijiazhuangnese With Normal Occlusion In Early Permanent Dentition

Objective: The aim of the present study was to establish the differential templates of the skeletal and soft tissue profiles for Shijiazhuangnese with normal occlusion in early permanent dentition and furthermore develope the clinical application of template analysis aided by computer in order to provide the theoretical basis of template analysis for clinical diagnosis, design and treatment evaluation for orthodontic patients.Methods: 1. Classifying samples: lateral cephalograms of Ninety-six early permanent dentition with normal occlusion samples who were selected in the school through a community dental health survey, were traced and measured. The vertical variables were mainly composed of SN-MP,FMA,PMA,AB-MP,ODI,Bjork sum,Gonial angle,Y axis angle,ANS-Me/N-Me,S-Go/N-Me. Cluster analysis was used to classify the 96 samples into three groups. They delegate the three kinds of vertical skeletal growth patterns, which were average growth pattern, horizontal growth pattern and vertical growth pattern. Discriminant analysis with a stepwise entry of variables was designed to identify individual malocclusion patient. 2. Establish templates : 40 skeletal landmarks, which were linked to templates of the skeletal and soft tissue profiles, were identified on the lateral cephalograms scanned on the computer. An X-Y coordinate system was established: rotated 7 degree down from the sella-nasion line as the X axis and the vertical line through sella perpendicular to the X axis as the Y axis. The coordinates of each sample's 40 landmarks were caculated and the database of the mean coordinates of every subgroup's characterstic landmarks could be formed. Connecting the 40 points of each group by computer software, three templates would be created. 3. Application for template analysis: First, we should select a suitable template for superimposition using the discriminant equations. Second, standardize the sizes between individual skeletal and soft tissue profiles and template by computer. Third, different planes were superimposed to show the variations between the two graphs in order to realize the patients'abnormalities visually.Results: 1. Finally, people of early permanent dentition with normal occlusion were divided into three groups according to vertical skeletal patterns. The mean of SN-MP, FMA, PMA, Y axis angle, Bjork sum, Gonial angle get maximum in third group, decressed in first group and get minimum in second group. The mean of ODI, AB-MP and S-Go/N-Me get minimum in third group, incressed in first group and get maximum in second group. 2. The discriminant formula of three types through stepwise discriminant analysis were constituted , thery wereY1=-528.557+7.144SN-MP+5.989PMA+9.216AB-MP; Y2=534.344+6.613SN-MP+5.642PMA+9.655-AB-MP;Y3=-584.672+8.213SN-MP+6.339PMA+9.286AB-MP. Discriminant analysis assigned 94.79% classification accuracy to the predictive model. 3. Between the three skeletal groups, significant differences were seen in 9 variables with analysis of variance. The nine variables were SN-MP,FMA,PMA,AB-MP,ODI,Bjork sum,Gonial angle,Y axis angle,S-Go/N-Me.The results demonstrate that when people with normal occlusion were studyed, the skeletal pattern should be taken into account. 4. The computer software and coordinate system were used to form the 40 landmarks database, by which three template graphs were obtained which represent three different skeletal patterns of people with normal occlusion.Conclusion: 1. This study classify normal occlusion samples into specific skeletal with the aid of mathematics. Discriminant analysis was also designed to provide fomula for an individual malocclusion. 2. The templates of the skeletal and soft tissue profiles were established in the light of vertical skeletal patterns of people with normal occlusion. 3.Template analysis is based on superimposition of individual cephalogram and template graphs. The proportion of craniofacial skeleton could be showen in the template graphs. It was concluded that template analysis is more convenient and graphic than other traditional cephalometric analysis and might facilitate clinical practice.