Bond strength of resin modified glass ionomer cement to primary dentin after cutting with different bur types and dentin conditioning

The aim of this in vitro study was to evaluate the effect of different bur types and acid etching protocols on the shear bond strength (SBS) of a resin modified glass ionomer cement (RM-GIC) to primary dentin. Forty-eight clinically sound human primary molars were selected and randomly assigned to four groups (n=12). In G1, the lingual surface of the teeth was cut with a carbide bur until a 2.0-mm-diameter dentin area was exposed, followed by the application of RM-GIC (Vitremer - 3M/ESPE) prepared according to the manufacturer's instructions. The specimens of G2, received the same treatment of G1, however the dentin was conditioned with phosphoric acid. In groups G3 and G4 the same procedures of G1 and G2 were conducted respectively, nevertheless dentin cutting was made with a diamond bur. The specimens were stored in distilled water at 37 degrees C for 24h, and then tested in a universal testing machine. SBS. data were submitted to 2-way ANOVA (= 5%) and indicated that SBS values of RM-GIC bonded to primary dentin cut with different burs were not statistically different, but the specimens that were conditioned with phosphoric acid presented SBS values significantly higher that those without conditioning. To observe micromorphologic characteristics of the effects of dentin surface cut by diamond or carbide rotary instruments and conditioners treatment, some specimens were examined by scanning electron microscopy. Smear layer was present in all specimens regardless of the type of rotary instrument used for dentin cutting, and specimens etched with phosphoric acid presented more effective removal of smear layer. It was concluded that SBS of a RM-GIC to primary dentin was affected by the acid conditioning but the bur type had no influence.

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degreesC for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.

Influence of cross-head speed on resin-dentin shear bond strength

Objective: To evaluate the influence of different cross-head speeds on shear bond strength test on the dentin surface.Methods: One hundred and twenty extracted bovine incisors were embedded in polystyrene resin. The specimens were prepared by wet grinding with 320-, 400- and 600-grit Al2O3 paper exposing dentin. After the application of the adhesive system Single Bond (3M) to etched dentin, the composite resin Z-100 (3M) was applied and light cured. The specimens were randomly assigned to four groups (n = 30). The shear bond strength tests were performed with an EMIC DL 500 universal testing machine at four different cross-head speeds: 0.50 (A); 0.75 (B); 1.00 (C); and 5.00 mm/min (D).Results: the mean values of shear bond strength in MPa (SD) were: A, 11.78 (3.91); B, 11.82 (4.78); C, 16.32 (6.45); D, 15.46 (5.94). The data were analyzed with one-way ANOVA and Tukey's test (alpha = 0.05). The results indicated that A = B < C = D. The fracture pattern was evaluated by visual analysis in a stereomicroscope (25 x). The percentage of fractures that occurred at the adhesive interface were: A, 92.5%; B, 91.6%; C, 70.0%; D, 47.0%. The Student's t-test to percentages ( = 0.05) indicated that there were no significant differences among A, B and C; A and B differed from D, and there was no significant difference between C and D.Significance: Different cross-head speeds may influence the shear bond strength and the fracture pattern in dentin substrate. Shear bond strength using cross-head speeds of 0.50 and 0.75 mm/min should be preferred. (C) 2001 Academy of Dental Materials. published by Elsevier B.V. Ltd. All rights reserved.

Repair bond strength of a resin composite to alumina-reinforced feldspathic ceramic

This study compared the microtensile bond strength of a repair resin to an alumina-reinforced feldspathic ceramic (Vitadur-alpha, Vita) after 3 surface conditioning methods: Group 1, etching with 9.6% hydrofluoric acid for 1 minute plus rinsing and drying, followed by application of silane for 5 minutes; group 2, airborne particle abrasion with 110-mm aluminum oxide using a chairside air-abrasion device followed by silane application for 5 minutes; group 3, chairside tribochemical silica coating with 30-mu m SiOx followed by silane application for 5 minutes (N = 30). Group 1 presented the highest mean bond strength (19.7 +/- 3.8 MPa), which was significantly higher than those of groups 2 (10 +/- 2.6 MPa) and 3 (10.4 +/- 4 MPa) (P <.01). Scanning electron microscope analysis of the failure modes demonstrated predominantly mixed types of failures, with adhesive and/or cohesive failures in all experimental groups.

Influence of ceramic surface conditioning and resin cements on microtensile bond strength to a glass ceramic

Statement of problem. It is not clear how different glass ceramic surface pretreatments influence the bonding capacity of various luting agents to these surfaces.Purpose. The purpose of this study was to evaluate the microtensile bond strength (mu TBS) of 3 resin cements to a lithia disilicate-based ceramic submitted to 2 surface conditioning treatments.Material and methods. Eighteen 5 X 6 X 8-mm ceramic (IPS Empress 2) blocks were fabricated according to manufacturer's instructions and duplicated in composite resin (Tetric Ceram). Ceramic blocks were polished and divided into 2 groups (n=9/treatment): no conditioning (no-conditioning/control), or 5% hydrofluoric acid etching for 20 seconds and silanization for 1 minute (HF + SIL). Ceramic blocks were cemented to the composite resin blocks with I self-adhesive universal resin cement (RelyX Unicem) or 1 of 2 resin-based luting agents (Multilink or Panavia F), according to the manufacturer's instructions. The composite resin-ceramic blocks were stored in humidity at 37 degrees C for 7 days and serially sectioned to produce 25 beam specimens per group with a 1.0-mm(2) cross-sectional area. Specimens were thermal cycled (5000 cycles, 5 degrees C-55 degrees C) and tested in tension at 1 mm/min. Microtensile bond strength data (MPa) were analyzed by 2-way analysis of variance and Tukey multiple comparisons tests (alpha=.05). Fractured specimens were examined with a stereomicroscope (X40) and classified as adhesive, mixed, or cohesive.Results. The surface conditioning factor was significant (HF+SIL > no-conditioning) (P<.0001). Considering the unconditioned groups, the mu TBS of RelyX Unicem was significantly higher (9.6 +/- 1.9) than that of Multilink (6.2 +/- 1.2) and Panavia F (7.4 +/- 1.9). Previous etching and silanization yielded statistically higher mu TBS values for RelyX Unicem (18.8 +/- 3.5) and Multilink (17.4 +/- 3.0) when compared to Panavia F (15.7 +/- 3.8). Spontaneous debonding after thermal cycling was detected when luting agents were applied to untreated ceramic surfaces.Conclusion. Etching and silanization treatments appear to be crucial for resin bonding to a lithia disilicate-based ceramic, regardless of the resin cement used.