A new method to assess the accuracy of a Cone Beam Computed Tomography scanner by using a non-contact reverse engineering technique.

Aim: Today Cone Beam Computed Tomography (CBCT) has become an important image technique for dento-maxilla facial applications. In the paper a new method to assess the geometric accuracy of these systems was proposed. It uses a free form benchmark model and a non-contact Reverse Engineering (RE) system. Method: The test geometry chosen for this study was designed in such a way that it simulated human spongy bone, cortical bone, gingiva and teeth and it composed of removable free form parts. It was acquired with a high-resolution laser scanner (D700 Scanner - 3Shape, Denmark). The reference 3D surface models obtained with the laser scanner was compared with the 3D models that were created from a CBCT system (Scanora 3D - Soderex, Finland) and from a traditional Multi-Slice Computed Tomography (MSCT) scanner (LightSpeed VCT 64 Slice - General Electric, USA) at different reconstruction settings, using an iterative closest point algorithm (ICP) in Geomagic (R) software. Results: The comparison between the different pairs of CAD models clearly shows that there is a good overlap between the models. Conclusions: Although the results obtained in this study could lead to increase the use of CBCT for an increasing number of dental procedures, the publication of the European Commission guidelines represents a baseline on which the clinicians should rely heavily when considering the use of CBCT in their practice. Clinical Significance: The results of this research show that the accuracy of CBCT 3D models is comparable to MSCT 3D models.