Shear bond strength between a polyester-based root canal filling material and a methacrylate-based sealer with an intermediate layer of fiber-reinforced resin-based material

Purpose: To investigate the effects of an interfacial fiber-reinforced resin-based material (FRRM) application and different light-curing modes on the bond strength of a thermoplastic synthetic polymer-based root canal filling material (Resilon) to a methacrylate-based sealer (Epiphany). Materials and Methods: One hundred Resilon disks were prepared and divided into two experimental groups: 1. application of FRRM (EverStick Net) on the Resilon surface, and 2. Resilon alone (control). Following subsequent application of the Epiphany sealer, the specimens were randomly assigned into 3 subgroups according to the curing method employed: 1. chemical curing, 2. quartz-tungsten-halogen (QTH) light, and 3. light-emitting diode (LED). The latter two groups were further subdivided to test the effects of two different polymerization modes for each light-curing unit. Cured specimens were subjected to shear bond strength testing and the failure modes were examined. The data were analyzed with three-way analysis of variance (ANOVA). Results: Regardless of the curing method tested, application of FRRM at the interface significantly increased the bond strength of Resilon to Epiphany (p < 0.001). Bond strength values (MPa) were as follows (mean ± SD): 1. chemical curing with FRRM= 3.0 ± 0.4, without FRRM = 1.2 ± 0.3; 2. QTH: a) standard mode with FRRM = 8.6 ± 0.6, without FRRM = 5.5 ± 0.9; b) ramp mode with FRRM = 8.0 ± 1.0, without FRRM = 5.3 ± 1.4; 3. LED: a) standard mode with FRRM = 8.8 ± 1.1, without FRRM = 5.4 ± 1.0; b) exponential mode with FRRM = 8.5 ± 1.0, without FRRM = 4.6 ± 0.6. Although light curing of specimens significantly increased the bond strength of Resilon to Epiphany (p < 0.001), the type of light-curing unit and different curing modes had no significant influence on bond strength (p = 0.852 and p = 0.776, respectively). Conclusion: The highest bond strength values were obtained when the FRRM was used at the interface and the sealer was light cured.