The Accuracy Evaluation Of Mandibular CBCT Cephalometric Superimposition In Adult Orthodontic Patients

ObjectiveCephalometric superimposition is an important tool for data analysis in orthodontic treatment. Recently, two-dimensional (2D) cephalometric superimposition technique has been more mature, however two-dimensional image has many limitions in clinic practice. Three-dimensional (3D) image can describe craniofacial morphology more directly and entirely, but now three-dimensional cephalometric superimposition has not been widely used in clinic. This study used CBCT to superimpose mandibular image befor and after orthdontic treatment, then compare the amount of teeth movement on three-dimensional superimposition image with that on plaster cast to evaluate its accuracy.Materials and MethodsThirty adult patients(aged 23.5±3.1 years, age range:18-30) with bimaxillary protrusion were choosed, during the year from 2010 to 2014.All the patients had four first premolars extracted, and then miniscrews were placed to provide anchorage. The average course of treatment was 22.9±2.2 months. Pre-and post-treatment CBCT scan were performed by CBCT and saved as DICOM (Digital Imaging and Communications in Medicine) formate, and used Materialism’s Interactive Medical Image Control System (MIMICS, version 16.0) to reconstruction three-dimensional images.3D images of the pre-(T1) and post-(T2) CBCT data of mandible was superimposed by Mimics. The pogonion (pg) and the anterior inferior boarder points of mental foramen were chosen for point regeistration, then proceed STL registration. Measured the amount of inciors and canines relatively setback on 3D superimposition images of pre-and post-treatment, then compared the data with that on plaster cast.Absolute error (AE) and absolute percentage error (APE) were used to evaluate the accuracy of 3D images superimposition. SPSS and MedCalc were used for statistical analysis. Used paired t test (a P value of P≤0.05 was used to assign statistical significance) and the Bland-Altman (B-A) plots to evaluate the agreement of these two methods. Intraclass correlation coefficient (ICC) was used as a measure of reliability.Results1.The absolute errors in inciors and canines were 0.214±0.109mm and 0.201±0.127mm. The absolute percentage errors were 4.12%±2.20% and 3.08% ±2.04%.2. No significant statistical differences between these two methods(P>0.05). The Bland-Altman plots demonstrated that the errors between the 3D superimposition technique and the gold standard were evenly distributed across the different magnitudes of expansion.3. The agreement assessed by ICC values was also excellent(ICC>0.9). The measure was reliable.ConclusionThe result of CBCT mandibular superimposition was accurate. So CBCT mandibular superimposition can be used to evaluate the changes of mandible in orthodontic treatmeat.