A Study On Buccal Surface Morphology Of The Canine And Premolar Teeth In Shandong Province In A Three-dimensional Digital Model

Objective:Degree of agreement between the bracket baseboard and tooth buccal surface not only affects the stability of the bracket bonding, but also directly affect preset data expression of the crown axis angle, torque angle, baseboard thickness and molar compensation angle in the straight wire appliance system. Studies have shown that the buccal contour of the canine and premolar is large. Therefore, the adhesion stability and preset data expression in the straight wire appliance system will be affected significantly by the degree of agreement between the bracket baseboard and tooth buccal surface. However, the domestic and international researches on crown buccal surface contour is insufficient, and there is no definite standard of the curvature radius. In recent years, the digital three-dimensional models measuring technology is more mature, which provide a convenience for our study. In this study, we use the digital three-dimensional models measuring technology to measure the buccal morphology in bracket bonding area of canine and premolar teeth in Shandong province, and analyze the differences between different skeletal malocclusion types, different gender and regions. Then we can provide the data reference for the improvement and design of the domestic straight wire appliance.Materials and Methods:204 adolescent patients aged from 13 to 18 years old were randomly selected who saw a doctor in Shandong University Dental Hospital for orthodontic treatment. These 91 boys and 113girls were divided into six groups by gender and ANB angle. We scanned all tested plaster cast by the inEos Lab device (Sirona, German, precision ≤15μm) to get digital three-dimensional dental model with the format of STL (stereolithography, STL).Then these data were input to JDP5.20 software (carved, Beijing) to measure the horizontal and vertical six radius of curvature, and use the SPSS20.0 software for statistical analysis.Results:1. Establish the database of the curvature radius in buccal bonding zone of canine and premolar teeth in Shandong province with different skeletal malocclusion types and different gender groups.2. In different gender groups, the vertical and horizontal curvatures are different.3. In different skeletal malocclusion types groups, the vertical and horizontal curvature radius are different either.4. There is no significant difference about the curvature radius of the bilateral teeth(P >0.05), except individual teeth.5. The buccal curvature radius of first and second premolar teeth have few differences in the three skeletal classes of male and skeletal class I, II of female. But there are different significantly in female skeletal classⅢ(P<0.05).6. There was a significant difference among three vertical curvature radius, so as to three horizontal curvature radius in canines and premolars from maxillary and mandible (P<0.01).Conclusion:1. In this experiment, the buccal contour of canines and premolars are different between three skeletal malocclusion types and two gender groups, suggesting that the bracket baseboard design should be different in crowds of different gender and different skeletal malocclusion types.2. In this study the three horizontal radius of curvature are variable as well as the vertical radius of curvature. So the bracket baseboard should reflect the changes in the horizontal and vertical directions of the tooth surface, and the domestic appliance should be improved. The premolar teeth in the same name of the same arch could use a consistent standard.3. It is necessary to establish database of buccal curvature radius in canine and premolar teeth, which will provide a basis for the design and improvement of the domestic straight wire appliance.