Reliability Of Assessment Of Craniofacial Changes Using Voxel Based Superimposition Of Cone-beam Computed Tomography Models In Growing Patients And Early Clinical Exploration

Part one Reliability of assessment of craniofacial changes using voxel based superimposition of cone-beam computed tomography models in growing patientsObjective: To evaluate reliability in 3-dimensional(3D)assessment of craniofacial changes using voxel based superimposition of cone-beam computed tomography(CBCT)models on the anterior cranial base in growing patients.Methods: Cone-beam computed tomography scans were performed before and after orthodontics treatment.Three observers independently constructed 180 3D virtual surface models from CBCT scans of 30 patients in InvivoDental software 5.1.3,reoriented 3D models before treatment to natural head posture.The anterior cranial base was used to register the 3D models before and after treatment.Mandibular voxel-based registration was done using an area encompassing from the internal part of the symphysis to the distal aspect of the first molars at the level of basal bone as a reference.Three observers independently identified 23 landmarks three times in the 3D models of before and after treatment,recorded three-dimensional coordinates of landmarks.The reliability of the method were analyzed.Results: The ICCs was > 0.90 for 59(85.5%)of the intraobserver assessments.The ICCs was > 0.90 for 49(1.0%)of the inte-observer assessments.The precision of the measurement method was < 0.3 mm in 10(14.5%)cases.Part two Evaluation of craniofacial changes after maxillary protraction with rapid maxillary expansion using voxel based superimposition and early clinical explorationObjective:: To evaluate 3-dimensional(3D)craniofacial changes aftermaxillary protraction with rapid maxillary expansion using voxel based superimposition of cone-beam computed tomography models.Methods: The CBCT records of 23 patients with skeletal Class III malocclusion characterized by maxillary hypoplasia(14 boys,9.76±1.28 years old,and 9 girls,9.04±1.12 years old)who had undergone RME/MP were selected from our CBCT database.The first CBCT scan was performed before RME/MP(T1)while the second was taken after treatment(T2),on average8~10 months later.Data from the CBCT were exported to InvivoDental software 5.1.3.Voxel based superimposition were used to evaluate 3-dimensional(3D)craniofacial changes.Paired samples t-tests were used for statistical comparison.Results: From the X coordinate,rUIAR,lUIAR and rZS were statistically different before and after treatment.From the Y coordinate,ANS,A point,rUIAR,lUIAR,rPA and lPA were significantly different before and after treatment.Conclusions: The reliability of three-dimensional assessment of craniofacial changes using voxel based superimposition in growing patients were excellent.