Effect of post-cure heating on the flexural strength of two indirect resin composites

The aim of this study was to evaluate whether a post-cure heat-treatment may improve the flexural strength of two indirect resin-based composites. Tested factors were: material (Gradia Indirect, Gradia Forte), mass (opaqus dentin, dentin, enamel) and curing mode (light, light and heat). A three-point bending test appliance was developed according to ISO 4049/2000. Three-Way ANOVA and 2-Pameter Weibull cumulative distribution function were performed. Factors material and curing mode were significant (p < 0.001), while the mass type was not (p = 0.181). A post-cure heat treatment may be useful for enhancing the flexural strength of both materials

Effects of post surface treatments on the bond strength of self-adhesive cements

Purpose: To evaluate whether fiber post surface conditioning techniques would influence the ultimate retentive strength of self-adhesive resin cements into the root canal. Methods: 50 single-rooted premolars with one root canal were endodontically treated and prepared to receive a fiber post. Five groups were formed (n=10) according to the post surface pre-treatment performed: (1) Silane application (Monobond S) for 60 seconds; (2) 10% hydrogen peroxide application for 20 minutes; (3) Rocatec Pre; (4) Silicate/silane coating (DT Light SL Post); (5) No treatment (DT Light Post). Two self-adhesive resin cements (RelyX Unicem and MaxCem) were used as luting agents. The bonded specimens were stored up to 1 month (37 degrees C and 100% humidity). The force required to dislodge the post (MPa) via an apical-coronal direction was measured with the push-out bond strength test (cross-head speed: 0.5 mm/minute until failure). Failure patterns were evaluated under SEM. Data was statistically analyzed with one-way ANOVA and Tukey tests (P&lt; 0.05). Results: No increase in the push-out bond strength values were observed for RelyX Unicem, independently from the post surface treatment performed. MaxCem attained higher bond strengths when luted to silanated posts

Effects of post surface treatments on the bond strength of self-adhesive cements

Purpose: To evaluate whether fiber post surface conditioning techniques would influence the ultimate retentive strength of self-adhesive resin cements into the root canal. Methods: 50 single-rooted premolars with one root canal were endodontically treated and prepared to receive a fiber post. Five groups were formed (n=10) according to the post surface pre-treatment performed: (1) Silane application (Monobond S) for 60 seconds; (2) 10% hydrogen peroxide application for 20 minutes; (3) Rocatec Pre; (4) Silicate/silane coating (DT Light SL Post); (5) No treatment (DT Light Post). Two self-adhesive resin cements (RelyX Unicem and MaxCem) were used as luting agents. The bonded specimens were stored up to 1 month (37 degrees C and 100% humidity). The force required to dislodge the post (MPa) via an apical-coronal direction was measured with the push-out bond strength test (cross-head speed: 0.5 mm/minute until failure). Failure patterns were evaluated under SEM. Data was statistically analyzed with one-way ANOVA and Tukey tests (P&lt; 0.05). Results: No increase in the push-out bond strength values were observed for RelyX Unicem, independently from the post surface treatment performed. MaxCem attained higher bond strengths when luted to silanated posts

Adhesion between fiber posts and resin luting agents: A microtensile bond strength test and an SEM investigation following different treatments of the post surface

Purpose: (1) To evaluate the interfacial strength between FRC Postec posts and three luting agents (Multilink, Variolink 11, and MultiCore Flow) following different surface treatments, and (2) to observe the effect of sandblasting (Rocatec Pre) on the surface morphology of methacrylate-based fiber posts. Materials and Methods: The posts received one of the following surface treatments: (1) sandblasting, (2) sandblasting + silanization, (3) silanization or (4) no treatment. The three luting agents were bonded to the post and the post-cement bond strength was evaluated with the microtensile test. SEM observation of sandblasted and nontreated posts was performed. Post-cement interfaces were also evaluated. Data were statistically analyzed with two-Way ANOVA with post treatment and luting agent as factors. Tukey's test was applied for post-hoc comparisons. Results: Post treatment and the interaction between type of luting agent and type of post treatment were significant factors for bond strength (p lt 0.001). The type of luting agent did not significantly influence bond strength (p = 0.07). Sandblasting + silanization performed better than sandblasting or no treatment (p lt 0.001). Silanization resulted in significantly higher bond strengths than no treatment (p = 0.045). No differences were detected between sandblasting + silanization and silanization. SEM observation revealed an increased surface roughness and exposure of fibers in sandblasted posts. Conclusion: Silanization was confirmed to be a reliable method for improving the bond strength of resin luting agents to fiber posts. Bond strength of resin luting agents to fiber posts was not influenced by the type of luting agent. The sandblasting procedure modified the methacrylate-based post surface texture

Effect of air-drying temperature on the effectiveness of silane primers and coupling blends in the repair of a microhybrid resin composite

Purpose: To evaluate the effect of different silane agents and air-drying temperatures on the repair strength of a microfilled hybrid composite. Materials and Methods: Composite cylinders (8 x 4 mm) of Gradia Direct Anterior (GC, N = 36), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (50-mu m aluminium oxide), cleaned (35% phosphoric acid) and randomly divided into six groups (n = 6). Two prehydrolyzed silane primers (Monobond-S, lvoclar-Vivadent, Porcelain Primer, Bisco), a non prehydrolyzed silane primer (Porcelain Liner M, Sun Medical) and three silane/adhesive coupling agents (Porcelain Bond Activator-PBA/Clearfil New Bond, PBA/Clearfil SE Bond, PBA/Clearfil Tri-S Bond, Kuraray) were investigated. Siiane-coated surfaces were air dried at two different temperatures (23 degrees C and 38 degrees C) and repairs (8 x 8 mm) were fabricated (Gradia Direct Anterior). Unrepaired composite cylinders (8 x 8 mm, n = 6) were used as control to evaluate the cohesive strength of the material. Microtensile bond strength measurements (mu TBS) were performed. Results: The silane agent applied (p lt 0.001), the airdrying temperature (p lt 0.001) and their interaction (p lt 0.001) were significant factors (two-way ANOVA, Tukey test; p lt 0.05). Silane primers achieved inferior mu TBS when air dried at 23 degrees C as compared to silane/adhesive blends. Warm air-drying was significantly beneficial to composite repairs mediated by silane primers. Comparable results were achieved by silane/adhesive couplings at 23 degrees C and 38 degrees C. At 38 degrees C all the intermediate agents resulted in repair mu TBS that were comparable to the 24-h cohesive strength of the composite (one-way ANOVA, Dunnett t-tests; p lt 0.05). Conclusion: The chemical interactions between silane primers and compozite substrate may be optimized through warm airdrying. Silane/adhesive couplings were not influenced by the air drying temperature

Effect of air-drying temperature on the effectiveness of silane primers and coupling blends in the repair of a microhybrid resin composite

Purpose: To evaluate the effect of different silane agents and air-drying temperatures on the repair strength of a microfilled hybrid composite. Materials and Methods: Composite cylinders (8 x 4 mm) of Gradia Direct Anterior (GC, N = 36), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (50-mu m aluminium oxide), cleaned (35% phosphoric acid) and randomly divided into six groups (n = 6). Two prehydrolyzed silane primers (Monobond-S, lvoclar-Vivadent, Porcelain Primer, Bisco), a non prehydrolyzed silane primer (Porcelain Liner M, Sun Medical) and three silane/adhesive coupling agents (Porcelain Bond Activator-PBA/Clearfil New Bond, PBA/Clearfil SE Bond, PBA/Clearfil Tri-S Bond, Kuraray) were investigated. Siiane-coated surfaces were air dried at two different temperatures (23 degrees C and 38 degrees C) and repairs (8 x 8 mm) were fabricated (Gradia Direct Anterior). Unrepaired composite cylinders (8 x 8 mm, n = 6) were used as control to evaluate the cohesive strength of the material. Microtensile bond strength measurements (mu TBS) were performed. Results: The silane agent applied (p lt 0.001), the airdrying temperature (p lt 0.001) and their interaction (p lt 0.001) were significant factors (two-way ANOVA, Tukey test; p lt 0.05). Silane primers achieved inferior mu TBS when air dried at 23 degrees C as compared to silane/adhesive blends. Warm air-drying was significantly beneficial to composite repairs mediated by silane primers. Comparable results were achieved by silane/adhesive couplings at 23 degrees C and 38 degrees C. At 38 degrees C all the intermediate agents resulted in repair mu TBS that were comparable to the 24-h cohesive strength of the composite (one-way ANOVA, Dunnett t-tests; p lt 0.05). Conclusion: The chemical interactions between silane primers and compozite substrate may be optimized through warm airdrying. Silane/adhesive couplings were not influenced by the air drying temperature

Flowable composites as intermediate agents without adhesive application in resin composite repair

Purpose: To evaluate the effect of different intermediate resin agents on composite-to-composite microtensile bond strength (mu TBS). Methods: Composite disks (8 x 4 mm) of Gradia Direct Anterior (N= 15) and Filtek Supreme XT (N=15), stored in a saline solution at 37 degrees C for I month, were sandblasted (Microetcher, 50 mu m-Al2O3), cleaned (35% H3PO4), and randomly divided into five groups (N=3) according to the intermediate agent applied. Two flowable composites (Gradia LoFlo; Filtek Supreme XT Flow) and two adhesives (Adper Scotchbond 1XT, Scotchbond Multi-Purpose) were used. As a control, no intermediate agent was applied., Each disk was incrementally repaired (W mm) with the same resin as the respective substrate. By serially cutting each repaired specimen, multiple sticks of about 0.8 mm(2) in cross-section were obtained and loaded in tension until failure at a cross-head speed of 0.5 mm/minute. Data were statistically analyzed. Failure mode was examined by stereo- and scanning electron-microscopy (SEM). Additional specimens were prepared to morphologically evaluate the composite-to-composite interfacial quality by SEM analysis. Results: Composite substrate and intermediate agent were significant factors (Two-way ANOVA, P lt 0.001). Bond strengths achieved with Gradia Direct Anterior were higher than Hick Supreme XT. The application of flowable composites resulted in statistically superior mu TBS than adhesives and control (Tukey test, P lt 0.001). Failure mode was predominantly cohesive (flowable composites), cohesive/adhesive (adhesives) and adhesive (no treatment). Flowable composites and adhesives showed a good interfacial quality

Accelerated aging of adhesive-mediated fiber post-resin composite bonds: A modeling approach

Objectives: Although fiber posts luted in root canals are not directly exposed to oral fluids, water storage is considered as in vitro accelerated aging test for bonded interfaces. The aim of the study was to evaluate the influence of accelerated water aging on fiber post-resin composite adhesion. Methods: Forty fiber posts (DT Light Post, RTD) were randomly divided into two main groups, according to the surface treatment performed. Group 1: XPBond adhesive (Dentsply Caulk); Group II: sandblasting (Rocatec-Pre, 3M ESPE) and XPBond. Dual-cured resin cement (Calibra, Dentsply Caulk) and flowable composite (X-Flow, Dentsply Caulk) were applied on the posts to produce cylindrical specimens. The bond strength at the interface between post and cement/composite was measured with the microtensile test according to the non-trimming technique. Half of the sticks were tested immediately for bond strength, while in the other half testing was performed after 1 month of water storage at 37 degrees C. Post-cement/composite interfaces were evaluated under SEM prior and after water aging. Statistical analysis was performed using the Kruskal-Wallis ANOVA followed by Dunn's multiple range test (P lt 0.05). Results: Immediate bond strength was higher on sandblasted posts. After water aging the two post surface treatments resulted comparable in bond strength. Resin cement achieved higher bond strength to fiber posts than flowable composite. Water aging significantly reduced bond strength. Conclusions: Sandblasting followed by adhesive coating may improve immediate post-resin bond strength in comparison to adhesive alone. However, fiber post-resin bond strength mediated by hydrophilic adhesive tends to decrease after water aging