Three-dimensional images from cone beam computed tomography (CBCT) may be helpful in the diagnosis of root fractures due to the elimination of image superimposition, thus facilitating visualization of eventual vertical dental root fractures. However, intracanal materials (e.g. metallic posts, fiberglass posts and gutta percha) may produce image artifacts that may hamper diagnosis of such fractures. CBCT acquisition protocols that use higher tube current values generally produce higher quality images; however, the increase in this parameter is related to a higher dose of radiation exposure. This study aims to determine the most adequate CBCT tube current parameters for the diagnosis of vertical root fractures in the absence of intracanal materials, and in the presence of gutta percha, metallic posts, and fiberglass posts. The sample will consist of 20 single-rooted teeth divided in two groups (i.e no fracture and with fracture). Teeth will be prepared to accommodate different intracanal materials and further divided into 8 subgroups: G1 - with fracture and no intracanal material; G2 - with fracture and with gutta percha; G3 - with fracture and with fiberglass post; G4 - with fracture and with metallic post; G5 - no fracture and no intracanal material; G6 - no fracture and with gutta percha; G7 - no fracture and with fiberglass; G8 - no fracture and with metallic post. Each tooth will be scanned using four different CBCT parameters for tube current (4mA, 8mA, 10mA, 13mA). These images will be randomly analyzed by five Oral and Maxillofacial Radiology specialists experienced in CBCT, and one Dental undergraduate student. A 5-point-scale will be used to classify images: (1) absence of root fracture, (2) probable absence of root fracture; (3) uncertain diagnosis; (4) probable presence of root fracture and (5) presence of root fracture. The area under the ROC (Receiver Operating Characteristic) curve will be calculated to assess sensitivity as a function of specificity for the diagnosis of root fractures in CBCT images obtained with different tube current parameters. Interobserver and intraobserver reliability will be assed by Weighted Kappa Index. The diagnostic values areas under ROC curve of each tube current parameter and each intracanal material tested will be calculated, and the values of areas under ROC curve will be compared using the analysis of variance (ANOVA) and two criteria Tukey post hoc test, and p<0.05.
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