Superimposition of 3D cone-beam CT models of orthognathic surgery patients

Abstract

Objectives-To evaluate the registration of 3D models from cone-beam CT (CBCT) images taken before and after orthognathic surgery for the assessment of mandibular anatomy and position.Methods-CBCT scans were taken before and after orthognathic surgery for ten patients with various malocclusions undergoing maxillary surgery only. 3D models were constructed from the CBCT images utilizing semi-automatic segmentation and manual editing. The cranial base was used to register 3D models of pre-and post-surgery scans (1 week). After registration, a novel tool allowed the visual and quantitative assessment of post-operative changes via 2D overlays of superimposed models and 3D coloured displacement maps.Results-3D changes in mandibular rami position after surgical procedures were clearly illustrated by the 3D colour-coded maps. The average displacement of all surfaces was 0.77 mm (SD = 0.17 mm), at the posterior border 0.78 mm (SD = 0.25 mm), and at the condyle 0.70 mm (SD = 0.07 mm). These displacements were close to the image spatial resolution of 0.60 mm. The average interobserver differences were negligible. The range of the interobserver errors for the average of all mandibular rami surface distances was 0.02 mm (SD = 0.01 mm).Conclusion-Our results suggest this method provides a valid and reproducible assessment of craniofacial structures for patients undergoing orthognathic surgery. This technique may be used to identify different patterns of ramus and condylar remodelling following orthognathic surgery.

Reliability of three-dimensional anterior cranial base superimposition methods for assessment of overall hard tissue changes: A systematic review

“…Pre-and posttreatment images were registered on the anterior cranial base surface on all studies, 3,7,12,16,21,25 and one was also superimposed on the left zygomatic arch. 12 …”

Deslocamentos esqueléticos associados à cirurgia de avanço mandibular: avaliação quantitativa tridimensional

“…Regional superimposition in the cranial base does not completely define the movement of the mandible relative to the maxilla 9,10,[20][21][22][23] . Previous studies 20,22,[24][25][26] revealed that relative displacement of mandibular and maxillary skeletal and dental components is critical because the resulting information may differ from conclusions formulated from the cranial base superimposition.…”

“…ia.unc.edu/dev/download/imagine/index.htm). 9 The software compares both images using the intensity of gray scale for each voxel of the region, so that the pre-surgical cranial base was used as reference for the superimposition of post-surgery models (Fig 1).…”

“…8 The use of 3-dimensional (3D) superimposition tools allows the identification and quantification of bone displacement and remodeling. 9,10 Previous studies 9,[11][12][13][14] have used the 3D virtual models superimposition technique to assess post-surgical outcomes and stability in Class III patients, but the post-surgical outcomes of Class II correction have not been evaluated by this method.…”

The Validity of 3dMD Vultus in Predicting Soft Tissue Morphology Following Orthognathic Surgery

“…This methodology was employed by Cevidanes et al (2005) who found that the superimposition of pre and post operative CBCT models of orthognathic surgery patients is a valid and reproducible technique, ideally suited to examining treatment outcomes.…”