| Objective:The purpose of this experiment is to improve the accuracy of digital orthognathic surgery by evaluating the effects of brackets,dentition status and registration methods on the accuracy of registration of CBCT dentition and laser scanning dental casts.Methods:The CBCT and laser scanned dental mold data of 26 patients were imported into Mimics 20.0 software to build 3D reconstructed dentition.Global registration and local registration of STL registration were used to register non-occlusal,occlusal CBCT dentition and laser-scan dental molds,which could be divided into four groups: group 1: non-occlusal dentition using local registration,group 2: non-occlusal dentition using global registration,group 3: occlusal dentition using local registration,group 4: occlusal dentition using global registration.Among them,13 patients had orthodontic metal brackets and 13 patients didn’t.Each group included three subgroups,which were registered three times according to the parameter settings of 3mm,1.5mm and 0.3mm,and the registration results were exported in STL format.With the help of the distance analysis function of Geomagic Studio software,the distance color scale diagram and the mean value,standard deviation and root mean square of the distance between the two images were obtained.First of all,find out the subgroup with the best matching effect in each group by the qualitative analysis of the distance between the matching model and the CBCT dentition outline and the color distribution of the color scale diagram,and through the quantitative analysis of the data of each subgroup,as the data of this group.After using SPSS software to test the normality and homogeneity of variance of the data,a general linear model was established to test the influence of bracket,dentition state and registration method on the accuracy of registration by multi-factor analysis of variance.Results:1.The local registration of each group is the best in 3 mm subgroup,and the global registration is the best in 0.3 mm subgroup.2.The sort of RMS values were as follows: group 3> group 4>group > group 2.3.The effects of bracket,dentition status and registration method on the registration results were statistically significant,but the interaction among them was not significant(P>0.05),but the interaction between bracket and dentition state,bracket and registration method,dentition status and registration method was significant(P<0.05).Through simple effect analysis,it was found that in occlusal dentition registration/bracket registration,the simple single effect of registration method on registration accuracy did not exist(P>0.05),while that of non-occlusal dentition registration/non-bracket registration had a simple single effect on registration accuracy(P<0.05).The simple single effect of occlusal dentition registration/non-occlusal dentition registration/local registration/global registration,with or without brackets on registration accuracy existed(P<0.05).There was a simple single effect of dentition status on registration accuracy in patients with brackets/patients without brackets/local registration/global registration(P<0.05).There was a simple single effect of occlusal dentition registration/non-occlusal dentition registration/local registration/global registration and with or without bracket registration on the accuracy of occlusal dentition registration/local registration/global registration(P<0.05).Conclusion:1.In this experiment,for patients with brackets,if you use local registration,you only need to match the parameters of 3mm once;if you use global registration,you need to register three times according to the parameters of 3,1.5 and 0.3mm.2.The accuracy of global registration of non-occlusal dentition is the highest.The registration accuracy of patients without brackets is better than that of patients with brackets.3.The presence of brackets,the status of dentition and the method of registration all have influence on the registration results. |
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