Abstract:

Objective： To evaluate the feasibility of integrating 3D photos and cone-beam computed tomography (CBCT) images and to assess the degree of error that may occur during the above process, and to analyze soft and hard tissue changes after orthognathic surgery using this new method. Methods: Ten patients with maxillofacial deformities were chosen. For each patient, CBCT scans and stereophotographic images were taken before and 3 months after surgery. 3D photos were superimposed onto the CBCT skin images using relatively immobile areas of the face as a reference. 3D color maps and mean distances were used to evaluate the errors that might occur during the process. Two reference planes were set up using certain points. The distances between Prn (pronasale)，Sn (subnasale)，Ls (labrale superior)，ANS (anterior nasal spine)，A (subspinale)，UIE (upper incisor edge) to the coronal plane were calculated before and after surgery. In order to verify the repeatability of this method, we examined the distances twice at two-week intervals. Paired t test was used to evaluate the reproducibility. Results: CBCT and 3D photos could be successfully fused with clinically acceptable errors. This new method could be used to evaluate soft and hard tissue changes after orthognathic surgery. The 3D color maps showed that the two images could be fused with minimal errors. The mean distances were within 0.3 mm, and the locations of landmarks on maxilla and mandible such as Ls, ANS, A, UIE changed significantly after orthognathic surgery (P<0.05).Landmarks on the nose such as Prn，Sn had little changes after surgery (P>0.1). The paired t test showed that the mean value and standard deviation were （0.08±0.98） mm. Conclusion: Fusing of CBCT and 3D stereophotographic images used as a new method in evaluating soft and hard tissue changes after orthognathic surgery was feasible and accurate. The virtual 3D composite craniofacial models permitted concurrent assessment of hard and soft tissues during diagnosis and treatment planning. Maxillary and mandibular locations had significant association with orthoganthic surgery while the nasal tissue was not simp affected by surgery.

Key words: Cone-beam computed tomography, Stereophotogrammetry, Orthognathic surgery, Soft and hard tissue changes