In vitro bonding two-unit cantilever resin-bonded fixed partial dentures

Objectives: This study evaluated the in vitro influence of surface pretreatment, luting cement and test method on the bond strength to enamel for two-unit CoCr cantilever resin-bonded fixed partial dentures (RBFPDs). Methods: CoCr beams simulating cantilever RBFPDs were luted to flat ground bovine teeth as substrate with four commercially available luting cements (UniFix, Cavex, The Netherlands; Resiment, Septodont, France; RelyX ARC, 3M-ESPE, Germany; Panavia F, Kuraray, Japan). The CoCr beams were pre-treated with either sandblasting or Rocatec (3M-ESPE, Germany). All samples were stored in tap water (37°C) during 72h after cementation. Subsequently tensile peel, load and torque strengths were determined. The effect of sandblasting and Rocatec pretreatments on the morphology of the CoCr surface was also investigated with SEM and EDAX analysis. Results: The average bond strength for Rocatec samples (132.0N) was significantly higher than for sandblasting samples (109.9N). Tukey post hoc test showed that the average bond strength of Rely X ARC (96.6N), Resiment (105.4N) and Panavia (110.0N) were within close range and significantly lower than UniFix (171.9N). Three-way ANOVA showed significant difference for the test method (F = 1633.3; P < 0.001), the luting cement (F = 81.7; P < 0.001), and the metal pretreatment (F = 33.7; P < 0.001). Furthermore, Tukey post hoc test showed that all three test methods had significantly different mean bond strengths; peel (22.0N), load (68.4N) and torque (272.6N). But the clinically most relevant test, the peel test, showed no significant effect of the Rocatec system. The best peel test results were obtained by using UniFix as luting cement and sandblasting as pre-treatment. Conclusion: Based on the results of this study the use of Unifix with sandblasting as metal surface pretreatment, is preferred for cementation of two-unit CoCr cantilever RBFPDs.