A Study On The Normal Occlusion Data Measurement In A Three-dimensional Digital Model

Objective: The three-dimensional data of Straight wire appliance had differences between regions.However,the normal occlusion data of northeast region had not been reported yet.In this study,the digital measurement techniques were used to measure the normal occlusion models characteristics in northeast region,and provided a reference of the straight wire appliance,to establish the three dimensional database of northeast region.Meanwhile,due to the molar’s large volume and diverse morphological variation,we decided to study the diversity of molar offset angle.This study provided multiple sets of basic data for molar brackets and buccal tubes in different offset angle.Methods: A total of 105 normal occlusion plaster models in northeast region were scanned by structured light scanning(Shining,precision<0.015 mm),and the digital three dimensional images of which was established with the format of STL(stereolithography,STL).We used data analysis software to define the occlusion plane and to mark each symbol points.The occlusive characteristics were analyzed by three-dimensional precision measurements.Measurement items consisted of four measurement indicators: the crown angulations,the crown inclinations,the crown facial prominence and the offset angle.The four data were used the SPSS 22.0 software for statistical analysis.Results: 1.Establish the three-dimensional data database of the northeast region normal occlusion.2.The first molar and second molar exist multiple types of offset angle,including distal offset,mesial offset and zero offset.3.The characteristics of dentition arrangement were similar to those of other researchers,but the specific values have their own characteristics: the lower second molar crown inclinations were slightly smaller than the average of other researchers.The crown facial prominence of both upper and lower incisors is slightly larger,the first molar facial prominence were slightly smaller.4.The study on the differences of angulation between different sexes showed that male and female mandibular first molars and second molars had significant differences(P<0.01).In the study of gender differences in inclination,there were gender differences in maxillary canines(P<0.05),While considerable differences existed between the mandibular incisor and the first molar(P<0.01).There were gender differences in the maxillary and mandibular incisors.Mandibular central incisor and maxillary first premolar were significantly different(P<0.01).Maxillary second molars offset angle were different(P<0.05).Conclusion: 1.The characteristics of normal occlusion in the northeast region were racially specific,so it was necessary to establish a regional normalization database to provide a reference for the design and manufacture of domestic appliances.2.This study showed that some three-dimensional data with gender differences,which suggested the occlusion characteristics individual teeth between men and women were different.These should be properly considered in clinical practice.3.There were diversities of molar compensation angles,so a single type of molar compensation angle couldn’t satisfy particular patients need.It was recommended that various types of molar brackets and buccal tubes should be used to accommodate patients with different types of compensation angles during orthodontic treatment,to reduce the bending of arch edgewise or to adjust the appliance and so on.