Fusion of intra-oral scans in cone-beam computed tomography scans

Abstract

Purpose: The purpose of this study was to evaluate the clinical accuracy of the fusion of intra-oral scans in cone-beam computed tomography (CBCT) scans using two commercially available software packages.

Materials and methods: Ten dry human skulls were subjected to structured light scanning, CBCT scanning, and intra-oral scanning. Two commercially available software packages were used to perform fusion of the intra-oral scans in the CBCT scan to create an accurate virtual head model: IPS CaseDesigner® and OrthoAnalyzer™. The structured light scanner was used as a gold standard and was superimposed on the virtual head models, created by IPS CaseDesigner® and OrthoAnalyzer™, using an Iterative Closest Point algorithm. Differences between the positions of the intra-oral scans obtained with the software packages were recorded and expressed in six degrees of freedom as well as the inter- and intra-observer intra-class correlation coefficient.

Results: The tested software packages, IPS CaseDesigner® and OrthoAnalyzer™, showed a high level of accuracy compared to the gold standard. The accuracy was calculated for all six degrees of freedom. It was noticeable that the accuracy in the cranial/caudal direction was the lowest for IPS CaseDesigner® and OrthoAnalyzer™ in both the maxilla and mandible. The inter- and intra-observer intra-class correlation coefficient showed a high level of agreement between the observers.

Clinical relevance: IPS CaseDesigner® and OrthoAnalyzer™ are reliable software packages providing an accurate fusion of the intra-oral scan in the CBCT. Both software packages can be used as an accurate fusion tool of the intra-oral scan in the CBCT which provides an accurate basis for 3D virtual planning.

Keywords: CAD; Digital imaging/radiology; Oral implants/implantology; Orthodontic(s); Orthognathic surgery; Treatment planning.

Fig. 1

Overview of the fusion process in the IPS CaseDesigner®. a Three-dimensional CBCT skull model in the IPS CaseDesigner® software with the left and the right condyle indicated as well as the occlusion plane. b Intra-oral scans of maxilla and mandible. c Cross-sectional view of the 3D CBCT skull model and fused intra-oral scans. d Frontal view of the result of the fusion of the intra-oral scans in the CBCT

Fig. 2

Overview of the fusion process of the intra-oral scans in the CBCT in OrthoAnalyzer™. a Three-dimensional CBCT skull model in OrthoAnalyzer™ with three points on both the maxillary and mandibular teeth. b Intra-oral scans of maxilla and mandible with three points on both the maxillary and mandibular teeth, corresponding with the points shown in 3A. c Cross-sectional view of the 3D CBCT skull model and fused intra-oral scans (shown in green). d Frontal view of the result of the fusion of the intra-oral scans in the CBCT

Fig. 3

Overview of the fusion process. (A) Virtual head model made with IPS CaseDesigner®. (B) Structured light scan (gold standard) of a dry humal skull with high detail of the bony structures as well as the teeth. (C) Virtual head model made with OrthoAnalyzer™. (D) Superimposition of the gold standard with the virtual head model created in IPS CaseDesigner® using the forehead, orbital rims, and zygomatic area as reference. (E) Superimposition of the gold standard with the virtual head model created in OrthoAnalyzer™ using the forehead, orbital rims, and zygomatic area as reference. (F) The different positions of the dental arches of IPS CaseDesigner® and the gold standard. Blue and gray: dental arch position of the gold standard, brown and white: position of the dental arches fused using IPS CaseDesigner®. (G) The different positions of the dental arches of OrthoAnalyzer™ and the gold standard. Blue and gray: dental arch position of the gold standard, brown: position of the dental arches fused using IPS CaseDesigner®. (H) Differences of the dental arches expressed in six DOF for IPS CaseDesigner® and the gold standard for both the maxilla and mandible. (I) Differences of the dental arches expressed in six DOF for OrthoAnalyzer™ and the gold standard for both the maxilla and mandible. LR left/right, AP anterior/posterior, CC cranial/caudal