Shear Bond Strength of Two Chemically Different Denture Base Polymers to Reline Materials

Purpose: This study evaluated the shear bond strengths of light-polymerized urethane dimethacrylate (Eclipse) and heat-polymerized polymethylmethacrylate (Meliodent) denture base polymers to intraoral and laboratory-processed reline materials. Materials and Methods: Thirty disks measuring 15 mm diameter and 2 mm thick were prepared for each denture base material following the manufacturers' recommendation. They were relined with Meliodent RR, Kooliner, and Secure reline materials after 1 month of water immersion. Ten additional Eclipse specimens were relined using the same Eclipse resin. A shear bond test was carried out on an Instron machine at a crosshead speed of 1.0 mm/min 24 hours after relining. Data were analyzed using two-way and one-way ANOVAs and post hoc Dunnett's T3 test (p = 0.05). The nature of failure was analyzed under a stereomicroscope. The effect of dichloromethane adhesive on the two denture polymer surfaces and the failed interfaces of mixed and adhesive failures were analyzed under a SEM (scanning electron microscope). Results: Two-way ANOVA showed significant differences in the shear bond strength values as a function of the denture base polymers, reline materials, and their interaction (p < 0.05). One-way ANOVA showed significant differences in shear bond strength values among denture base-reline combinations (p < 0.05) except for Meliodent-Kooliner and Eclipse-Meliodent RR relines. Meliodent showed the highest shear bond strength value when relined with Meliodent RR (14.5 +/- 0.5 MPa), and Eclipse showed the highest value with Eclipse relining (11.4 +/- 0.6 MPa). Meliodent denture base showed adhesive, cohesive, and mixed failure, while all Eclipse showed adhesive failure with various reline materials. Conclusion: The two chemically different denture base polymers showed different shear bond strength values to corresponding reline materials.