Use of the metal artefact reduction tool in the identification of fractured endodontic instruments in cone-beam computed tomography.

AIM: To evaluate the influence of the metal artefact reduction (MAR) tool in the diagnosis of fractured instruments in root canals of extracted mandibular molars, with or without root canal fillings. METHODOLOGY: The root canals of 31 mandibular molars were divided into four groups: (i) the control group, without root fillings; (ii) the fracture group, without fillings and with fractured files; (iii) the fill group, with root filling; and (iv) the fill/fracture group, root filled and with fractured files. The following instruments were used as fractured endodontic instruments: stainless steel hand files, NiTi reciprocating files and NiTi rotary files. Each tooth was inserted in a dry mandible to obtain cone-beam computed tomography (CBCT) images using a CBCT OP300 3D Maxio (Instrumentarium Dental, Tuusula, Finland) and Picasso Trio (Vatech, Hwaseong, Republic of Korea), with and without application of the MAR tool. All images were evaluated by three radiologists for the presence or absence of fractured files on a 5-point scale. The diagnostic accuracy (area under ROC curve) was calculated. Image noise was measured in regions of trabecular and cortical bone and soft tissue. The comparison between the ROC curve values with the MAR tool enabled or disabled was performed using a t-test. A t-test was also employed for comparing image noise when the MAR tool was enabled and disabled. The significance level was set at 5%. RESULTS: The use of the MAR tool did not influence the diagnostic accuracy for identifying fractured endodontic instruments in root canals with and without fillings in both CBCT systems (P > 0.05), nor did it influence the image noise (P > 0.05). CONCLUSIONS: The MAR tool on these two devices did not increase the detection of fractured endodontic instruments and did not reduce image noise using extracted mandibular molars. Therefore, the MAR tool is not recommended for evaluation of fractured endodontic instruments in teeth with and without root fillings in mandibular molars.

Influence of Cone-Beam Computed Tomography filters on diagnosis of simulated endodontic complications.

AIM: To evaluate the influence of cone-beam computed tomography (CBCT) filters on diagnosis of simulated endodontic complications. METHODOLOGY: Sixteen human teeth, in three mandibles, were submitted to the following simulated endodontic complications: (G1) fractured file, (G2) perforations in the canal walls, (G3) deviated cast post, and (G4) external root resorption. The mandibles were submitted to CBCT examination (I-Cat® Next Generation). Five oral radiologists evaluated the images independently with and without XoranCat® software filters. Accuracy, sensitivity and specificity were determined. ROC curves were calculated for each group with the filters, and the areas under the curves were compared using anova (one-way) test. McNemar test was applied for pair-wise agreement between all images versus the gold standard and original images versus images with filters (P < 0.05). RESULTS: G1 was the most difficult endodontic complication to diagnosis, followed by G2, G4 and G3. There were no differences between areas under the ROC curves for the filters in all groups; however, Sharpen Super Mild filter had the best results for G1 (0.47), Angio Sharpen Low 3 × 3 for G2 (0.93), Angio Sharpen Low 3 × 3, S9, Shadow and Sharpen for G3 (1.00) and Sharpen 3 × 3 for G4 (1.00). The McNemar test revealed significant differences between all filters with the gold standard (P = 0.00 for all filters) and the originals images (P = 0.00 for all filters) only in G1 group. There were no differences in the other groups. CONCLUSIONS: The filters did not improve the diagnosis of the simulated endodontic complications evaluated. Their diagnosis remains a major challenge in clinical practice.

Influence of glass fibre post length and remaining dentine thickness on the fracture resistance of root filled teeth.

AIM: To evaluate, ex vivo, the influence of glass fibre post length and remaining thickness of dentine on the fracture resistance of bovine roots, after thermomechanical ageing. METHODOLOGY: Ninety bovine roots of the same size were root filled and randomly distributed into nine groups (n = 10), according to the root weakening protocol (NW - nonweakened; MW - medium weakened; HW - highly weakened) and post length (7 mm; 9 mm and 12 mm). The weakening of roots was performed using diamond burs, resulting in different thicknesses of remaining dentine. The post spaces were prepared, and in the weakened roots, the glass fibre posts were customized with composite resin, to create posts matching the canal size. Chemically activated resin cement was used to lute the posts. After luting, full crowns made of composite resin were attached to a silicon matrix. To reproduce physiological mobility, the roots were covered with polyether and embedded in polyurethane. The thermomechanical cycling was performed (1 200 000 cycles; 88N; 3,8 Hz; 5 ± 1 °C to 55 ± 1 °C). Then, the specimens were subjected to compressive force in a universal testing machine (1 mm min-1 ; 100 kgf) to analyse the fracture resistance. The specimens were analysed through a stereomicroscope to classify the failure mode (repairable/catastrophic). The values were subjected to statistical analysis (two-way anova and Tukey's test at 5%). The frequencies of failure mode were compared using chi-square test. RESULTS: The association between length and dentine thickness was significant (P > 0.05). The difference was between NW and HW roots for posts of 12 mm in length. There was an association between failure mode and the length and remaining dentine thickness. CONCLUSIONS: Reduced dentine thickness in roots with longer posts had lower fracture resistance values, as catastrophic failure was more predominant.