Optimized CBCT protocol for intraoperative application in endodontics

Abstract

Cone-beam computed tomography (CBCT) has been frequently used in endodontics due to allows a three-dimensional evaluation of the area of interest and has higher accuracy in the diagnosis of clinical conditions when compared to periapical radiographs. Considering that the most indicated CBCT protocol for endodontics should have a smaller FOV and higher spatial resolution, a higher radiation dose may be associated. Thus, dose optimization, that is, the use of a lower dose without compromising diagnostic accuracy, has been shown to be an essential point to be analyzed in the literature. Therefore, this study aims to evaluate the diagnostic accuracy of an optimized CBCT protocol in the detection of intraoperative endodontic complications. An image phantom composed of a partially edentulous macerated human mandible and forty lower first molars will be made. The mandible will be covered by Mix-D, a simulator of X-ray absorption and scattering of soft tissues. The 40 teeth will be subdivided into 4 groups: a. control/absence of complications (n=10); B. pulp calcification (n=10), c. file fracture (n=10) and d. root perforation (n=10). Initially, all teeth will be submitted to access surgery and removal of the pulp chamber roof and, later, endodontic instrumentation will be performed. The pulp calcification group will be composed of a selected sample of teeth with pre-existing calcification. In the file fracture group, 10 reciprocating files will be inserted into each of the teeth. And, in the root drilling group, the drillings will be performed using a Gates-Glidden drill. All teeth will be scanned with the Micro-CT Skyscan 1174 (Kontich, Belgium) and CBCT images will be acquired for the 10 teeth of each group individually positioned in the empty socket of the lower left first molar of the imaging phantom with the OP 300 unit (Instrumentarium, Dental, Tuusula, Finland) adjusted at FOV of 6 x 4 cm, 90kVp and 3 different dose protocols: low (18.4mAs and 0.2mm voxel), standard (48.8mAs and 0.13mm voxel) and high (79.3mAs and 0.085mm voxel). Additionally, a titanium implant will be inserted into the empty socket of the second premolar, adjacent to the tooth of interest, to simulate image artifacts. The CBCT images of the imaging phantom will be analyzed subjectively in the Osirix MD software by four evaluators who will indicate the presence of pulp calcification, file fracture and root perforation on a 5-point scale. Sensitivity, specificity and area under the receiver operating characteristic curve will be calculated and analysis of variance and Tukey's post hoc test will compare the different dose protocols with a significance level of 5%. The expected results are the reduction of the radiation dose without compromising the diagnostic accuracy in the evaluation of pulp calcification, file fracture and root perforation.