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.