Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy.

OBJECTIVE: This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin. MATERIALS AND METHODS: Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface. RESULTS: Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure). CONCLUSION: Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition. CLINICAL RELEVANCE: Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Influence of a Metal Artifact Reduction Filter on the Diagnostic Accuracy of Complete and Incomplete Vertical Root Fractures.

INTRODUCTION: This study aimed to assess the influence of the e-vol DX BAR filter on the diagnostic accuracy of complete and incomplete vertical root fractures (VRFs). METHODS: Twenty single-rooted teeth were selected. The tooth crowns were removed, and the root canals were prepared up to a 40/.06 instrument (ProTaper Next). Each specimen was scanned in a Prexion 3D cone-beam computed tomography (CBCT) device, in a dry human skull, in 4 different situations: no root canal filling, gutta-percha, fiberglass post, and metal post. The specimens were fractured in a universal testing machine by using a customized wedge. Each specimen was reinspected to confirm the presence of incomplete VRFs. Another set of CBCT scans was performed. Then, the fractures were completed in the universal testing machine, the teeth were reinspected, and the CBCT images were acquired again. Images were assessed by using the e-Vol DX software system, with the BAR filter and with the original images, for the diagnosis of VRFs. Statistical analysis was performed by using the DeLong and McNemar tests for the comparison of the area under the receiver operating characteristic curves (AUC), accuracy, sensitivity, and specificity values. RESULTS: The use of the BAR filter did not improve the diagnostic values of AUC, accuracy, sensitivity, and specificity in both fracture patterns (P > .05). Incomplete VRFs presented significantly lower AUC, accuracy, and sensitivity compared with complete VRFs (P < .0001). CONCLUSIONS: The BAR filter did not improve the diagnostic accuracy of VRFs. The intracanal materials also did not influence the diagnosis. Incomplete VRFs were highly associated with a decrease in sensitivity.

Development and validation of a method for creating incomplete vertical root fracture in extracted teeth.

The present study reported a method for inducing incomplete root fracture in human extracted teeth for the purpose of evaluating the merits of different diagnostic imaging techniques. Thirty-five single-rooted teeth were inspected under magnification and transillumination to exclude previously fractured teeth. Tooth crowns were removed, and the root canals were prepared up to the ProTaper Next X4 (40.06) file. Each root was lined with wax and embedded in a polystyrene resin block. The setup was attached to a universal testing machine for pressing a customized conical wedge (diameter at tip: 0.6 mm; taper: 0.2 mm/mm) into the instrumented canal with a 2 kN load at 5 mm/min. The machine was programmed to stop after a sudden 10% drop in loading force. Each specimen was removed from the resin block and inspected under × 20 magnification and transillumination to identify the fracture characteristics (pattern, surfaces and root-third affected). The gap width of each specimen was measured at different locations along the fracture line. The protocol induced incomplete vertical root fractures in all specimens. Fracture widths were < 100 µm in all specimens (mean gap width: 34.9 µm). The proposed methodology was successful in inducing incomplete vertical root fractures with characteristics that resemble the clinical presentation of these conditions. The method is easy to execute, highly reproducible and helps to minimize bias in laboratory studies that aims to mimic vertical root fractures.

Effect of Sodium Thiosulfate on Interfacial Adaptation and Penetration of an Epoxy Resin-Based Root Canal Sealer.

Introduction: Our study evaluated the impact of sodium thiosulfate (ST) irrigation, subsequent to sodium hypochlorite (NaOCl) and just before root canal filling, on the filling quality (interfacial adaptation and penetration segment) of an epoxy resin-based root canal sealer. Methods and Materials: Twenty single-rooted human teeth were prepared with the ProTaper system. The specimens were then divided into the following groups: 5.25% NaOCl irrigation (NaOCl group) and 5.25% NaOCl irrigation+0.5% sodium thiosulfate (NaOCl+ST group). The root canals were filled using single-cone technique with ProTaper F3 cones and AH-Plus sealer, labeled with rhodamine B dye to allow analysis under a confocal laser scanning microscopy (CLSM). All samples were sectioned at 2, 4, and 6 mm from the apex and prepared for CLSM analysis. The percentage of voids, gaps and dentinal sealer penetration segment of the canal were calculated at the apical, middle and coronal thirds. The non-parametric Mann-Whitney statistical test was used at 5% significance level. Results: Higher percentage of gaps and voids were observed at all root thirds of the NaOCl group when compared to the NaOCl+ST group (P<0.05). There was a significant increase in the penetration segment of NaOCl+ST group at the coronal and middle root third when compared to the NaOCl group (P<0.05). Conclusion: Our in vitro results showed that the use of ST as an antioxidant agent after NaOCl irrigation promoted a better interfacial adaptation and penetration of epoxy resin-based root canal fillings.