A Study On Reliability And Difference Between Cone-Beam CT Three-Dimensional Measurement And Two-Dimensional Lateral Cephalometry

Objective:To research the difference of some general distance and cephalome trics angles between 2D X-ray digitalization conventional cephalometrics and digital 2D lateral cephalometric images generated from CBCT 3D data before comparing and investigating these corresponding items from 2D lateral cephalometric and CBCT 3D measurement,as well as compare the reliability of these three measures.Methods:In this research we selected 78 juniors of a college who have normal occlusion,with ages among 18-20,and were radiographed with cephalometrical film and scanned with cone-beam computed tomography.The operator separately took the measurement of 5 general distances(Co-A?Co-Gn?ANS-Me?L1-APog?N-Me)and 6 cephalometrics angles(SNA?SNB?ANB?FMA?U1-L1?Y-axis)from 3D and2 D views by Dolphin Imaging 11.8 Premium software.The Cephalogram from CBCT(CCB)was produced and measured by the same software,each data was measured twice.These measurements of each item was compared by Intraclass Correlation Coefficient(ICC)to observe their test-retest repeatability and then scored the average magnitudes.All the measurement data was checked and imported into SPSS 19.0software.The values of all the groups were accorded with the normal distribution.Paired t-test was used for analysing the differences between both valuses from three groups,a p-value of <0.05 was taken as statistically significant.Results: There were about 100%(11/11)items in CBCT 3D measurements,whose ICC>0.9,and there were 72.7%(8/11)items in digital 2D lateral cephalometric images generated from CBCT 3D data,whose ICC>0.9,but there was no ICC<0.75.In 2D digitalization conventional cephalometrics,there were about 63.6%(7/11)of items,whose ICC>0.9 and no ICC<0.75.All of these measurements were repeatabille,the test-retest reliability of three measurements is very high.There were few different measurements between CBCT 3D and conventional cephalometrics 2D cephalometric.In the first group,one different value(L1-APog)of all general distances had statistical significance(P<0.05),(20%),and there were two different values(FMA & Y axis)of all cephalometrics angles had statistical significance(P<0.05),(33.3%).In the second group,one different value(L1-APog)had statistical significance(P<0.05),(20%),and there was one different value(FMA)of all cephalometrics angles hasstatistical significance(P<0.05),(16.7%).Finally,in the last group,one different value(L1-APog)of all general distances had statistical significance(P<0.05),(20%),and there was one different value(FMA)of all cephalometrics angles had statistical significance(P<0.05),(16.7%).No significant difference was found in the other values of groups(SNA?SNB?ANB?U1-L1?Co-A?Co-Gn?ANS-Me?N-Me).Conclusion:1.The reliability of CBCT 3D measurement was the highest among these three methods.CCB was better than X-ray digitalization conventional cephalome trics,but both of their reliability were lower than that of CBCT 3D measurement.2.There was no statistical difference among CBCT 3D measurement,CCB and digital cephalometric analysis in 8 of 11 items,and there was few difference between CBCT3 D measurement and 2D cephalometric analysis.3.There was no statistical difference in 9 of 11 items between CCB and X-ray digital cephalometric radiographs.These two methods of 2D lateral cephalometry were high similarity,and both of them can be used for precise cephalometric analysis.