Innovative CT imaging applications in dental treatment

Abstract

Computed tomography (CT), which has advantages of fast and accurate acquisition of internal and metrological information of the object, has been introduced in dentistry since the mid 2000’s. Recently, there have been various attempts to actively utilize dental CT imaging for dental treatment. Although a variety of digital-based dental applications that actively employ CT images are being developed, the applications are still constrained by existent challenging issues such as artifacts which degrade image quality. Therefore, in this work, we have investigated innovative applications of CT imaging in dental treatment. In addition to the new applications of dental CT imaging which have not been studied so far, research has been conducted to overcome the technical limitation of dental CT imaging. At first, we proposed a new CT application to endodontic treatment for the challenging situation of the patients who have anomalous teeth and therefore cannot be treated by a general endodontic treatment. Morphologic information of tooth and internal root canal structures were achieved from CT data, and were converted to physical tooth model and custom-made jig by 3D printing techniques. With the fabrications, a novel endodontic treatment procedure which provides precise and safe working path to the anomalous root canal was successfully established. Next, we investigated innovative CT application for dental restoration that can fabricate accurate and efficient digital cast model. The key idea of the proposed scheme is that dental impression of patients can be accurately digitized by CT scan and that one can make digital cast model from CT data directly. By segmentation of the air regions and conversion to digital surface model, accurate digital cast model for dental restoration was fabricated. We also studied a new reduction method of metal artifacts which is the main problem that hinders the application of dental CT imaging. As additional tilted CT scans would provide information complementary to that of scans in which some regions are free of metal artifacts, a modified version of SSIM was utilized to generate artifact-free image by selecting the regions with less metal artifacts between original and tilted CT images. Unlike the widely used MAR methods that require sinogram data, the proposed method consists of a post-processing procedure alone, which can be performed without reference to the CT system or reconstruction method. Both simulation and experimental studies were conducted to check the clinical feasibility and validity of the proposed methods in dentistry. We have successfully validated that dental CT imaging in each specific subject can effectively serve the corresponding purpose. These studies are expected to be available not only in dentistry but also in other medical fields using CT system.