Comparative Research On Reliability Of 2D And CBCT-3D Cephalometrics Of People With Normal Occlusion

Objective: To compare the reliability of 2D cephalometrics and CBCT-3D as well as 2D cephalometrics angle and line spacing transformed by CBCT.Methods: The researchers selected 50 college students as subjects who have normal occlusion without facial malformation. 50 research subjects receive the shooting of cephalometrical film and CBCT. Winceph8.0 was used to conduct 2D measurement for cephalometrical film. After taking CBCT, NNT software was used to output DICOM file,and then it was input into Mimics software which was used to conduct 3D cephalometrics.The measurement results of 2D cephalometrical film transformed by CBCT were produced by automatic projection of Mimics software. Three methods were all used to measure 22 item values. There were three operators separable who conducted the measurement two times every seven days.(Intra-class Correlation Coefficient, ICC) was used to compare the reliability and accuracy of measurement values by 2D and CBCT-3D within operators and among operators. Analysis of variance was used to compare the differences of these three measurements.Results: For ICC in operators, there were 68.1% items in 2D measurement whose ICC>0.9(15/22), and there were 9% whose ICC<0.75. In CBCT-3D measurement, there were 81.8% items whose ICC>0.9(18/22) and there was no item whose ICC<0.75. In CBCT-2D measurement, there were 72.7% items whose ICC>0.9(16/22) and 4.5% items whose ICC<0.75(1/22), and the statistically significant differences were observed.(F=3.204,p=0.047)In terms of ICC among operators, in 2D measurement, there were 59.1% items whose ICC>0.9(13/22). In CBCT-3D measurement, there were 81.8%items whose ICC>0.9(18/22). In CBCT-2D measurement, there were 68.1% items whose ICC>0.9(15/22). In the three groups, there was no item whose ICC<0.75, and the statistically significant differences were observed.(F=5.826, p=0.005). In the angle measurement, in addition, SNB, Y axis, FH-MP, MP-SN, L1-MP, there were eight measured such as SNA、ANB、NA-Pog A、NPog-FH、U1-SN、U1-NA、L1-NB and U1-L1;values of angle(p<0.05). The differences all had statistical significance. According to the results of the comparison, the comparison of 2D measurement and CBCT-3D measurement,all the measurement items had significant difference(p<0.05). In comparison of CBCT-3D measurement and CBCT-2D measurement, ANB、NA-Pog A、U1-SN、L1-NB、U1-L1、B-Go 、 Ar-Go difference had statistical significance(p<0.05); comparison of 2D measurement and CBCT-2D measurement, ANB、NPog-FH、U1-SN、U1-NA、U1-L1、ANS-PNS items differences had statistical significance(p<0.05).Conclusion: This research shows that there is a certain difference between the traditional2 D cephalometric measurement and CBCT-3D measurement and CBCT-2D measurement results and CBCT-3D cephalometric measurement method of have higher reliability, which is to reduce the errors caused by human factors in clinical cephalometric. This research provided experimental basis for further clinical application of CBCT-3D.