Endodontic sealer residues remaining within the pulp chamber dentin after root canal obturation and cleaning with various solvents may compromise the appearance and the durability of dental restorations. Acid etching is routinely performed prior to application of dentine adhesive systems, but is effect on residual sealer material and the optimal time-point for performing etching, are unknown. Here, we evaluated the effect of acid etching on the dentin surface when performed either immediately or 7 days after removal of the endodontic sealer with two solvents, i.e., 95% ethanol or xylol. Forty crowns fragments from bovine incisors were impregnated with sealer and divided into 4 groups (n = 10 each), according to the dentin cleaning protocol and to the acid etching time-point: G1, 95.0% ethanol and immediate acid etching; G2, xylol and immediate acid etching; G3, 95.0% ethanol and acid etching after 7 days; and G4, xylol and acid etching after 7 days. Scanning electron microscopy (SEM) images (2000 ×) were obtained from each specimen and the number of open dentinal tubules counted and compared. Another 40 fragments were similarly prepared, and SEM images were obtained (500 ×) to score and compare the persistence of sealer residues on the dentin. G4 showed the most open dentinal tubules and the least epoxy resin-based sealer residues on the dentin surface (p < 0.05). The least epoxy resin-based sealer residues was obtained when acid etching, using 37% phosphoric acid, was performed after 7 days after cleaning the dentin with xylol.
This study evaluated the effects of 10% alphatocopherol on the fracture resistance of endodontically treated teeth subjected to tooth bleaching with hydrogen peroxide and immediately restored with composite resin. Fifty bovine incisors were selected, including 10 sound teeth that constituted the control group (G1 (C)). The remaining 40 teeth, which were endodontically treated, were divided into four groups (n = 10): G2 (CR), consisting of teeth immediately restored with composite resin; G3 (HP + CR), consisting of teeth subjected to tooth bleaching with 38% hydrogen peroxide and immediately restored with composite resin; G4 (HP + SA + CR), which received treatment similar to that used for G3, but with 10% sodium ascorbate gel applied after the bleaching protocol; and G5 (HP + AT + CR), which was similar to G4 but included 10% alphatocopherol gel as an antioxidant. After 24 h, composite restorations were performed, and teeth were subjected to a fracture resistance test at a speed of 0.5 mm/min in an electromechanical testing machine. The axial force was applied with an angle of incidence of 135° relative to the long axis of the root. Data were subjected to ANOVA and Tukey tests (p = 0.05). G1 exhibited the highest fracture resistance (p < 0.05). No significant differences among the other experimental groups were observed. The 10% sodium ascorbate and 10% alphatocopherol gels did not improve the fracture resistance of endodontically treated teeth subjected to bleaching with 38% hydrogen peroxide.
PDT presented negative effects on the bond strength to dentin in the cervical third after cementation using Relyx ARC and on the dentinal penetrability of the etch-and-rinse adhesive system in the cervical and apical thirds of the prosthetic space.
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