ABSTRACT
PURPOSE: To evaluate 3-dimensional changes in the position of the condyles, rami, and chin from 1 to 3 years after mandibular advancement surgery. MATERIALS AND METHODS: This prospective observational study used pre- and postoperative cone-beam computed tomograms of 27 subjects with skeletal Class II jaw relation and normal or deep overbite. An automatic technique of cranial base superimposition was used to assess positional and bone remodeling changes that were visually displayed and quantified using 3-dimensional color maps. Analysis of covariance with presence of genioplasty, age at time of surgery, and gender as explanatory variables was used to estimate and test adjusted mean changes for each region of interest. RESULTS: The chin rotated downward and backward 1 to 3 years after surgery. Changes of at least 2 mm were observed in 17% of cases. Mandibular condyles presented with displacements or bone remodeling of at least 2 mm on the anterior surface (21% of cases on the left side and 13% on the right), superior surface (8% on right and left sides), and lateral poles (17% on left side and 4% on right). Posterior borders of the rami exhibited symmetric lateral or rotational displacements in 4% of cases. CONCLUSION: In the hierarchy of surgical stability, mandibular advancement surgery is considered one of the most stable surgical procedures. However, 1 to 3 years after surgery, approximately 20% of patients had 2- to 4-mm changes in horizontal and vertical chin positions or changes in condylar position and adaptive bone remodeling.
Subject(s)
Imaging, Three-Dimensional/methods , Mandibular Advancement/methods , Adult , Age Factors , Bone Remodeling/physiology , Cephalometry/methods , Chin/diagnostic imaging , Cone-Beam Computed Tomography/methods , Female , Follow-Up Studies , Genioplasty/methods , Humans , Image Processing, Computer-Assisted/methods , Longitudinal Studies , Male , Malocclusion, Angle Class II/diagnostic imaging , Malocclusion, Angle Class II/surgery , Mandible/diagnostic imaging , Mandibular Condyle/diagnostic imaging , Osteotomy, Sagittal Split Ramus/methods , Overbite/diagnostic imaging , Overbite/surgery , Prospective Studies , Recurrence , Rotation , Sex FactorsABSTRACT
OBJECTIVE: To evaluate reliability in 3-dimensional (3D) landmark identification using cone-beam computerized tomography (CBCT). STUDY DESIGN: Twelve presurgery CBCTs were randomly selected from 159 orthognathic surgery patients. Three observers independently repeated 3 times the identification of 30 landmarks in the sagittal, coronal, and axial slices. A mixed-effects analysis of variance model estimated the intraclass correlations (ICC) and assessed systematic bias. RESULTS: The ICC was >0.9 for 86% of intraobserver assessments and 66% of interobserver assessments. Only 1% of intraobserver and 3% of interobserver coefficients were <0.45. The systematic difference among observers was greater in X and Z than in Y dimensions, but the maximum mean difference was quite small. CONCLUSION: Overall, the intra- and interobserver reliability was excellent. Three-dimensional landmark identification using CBCT can offer consistent and reproducible data if a protocol for operator training and calibration is followed. This is particularly important for landmarks not easily specified in all 3 planes of space.
