Bond strength of relined denture base resins after water storage

Objectives: The aim of this study was to evaluate the effect of water storage on the shear bond strength between two autopolymerizing reline acrylic resins (Ufi Gel Hard-U e Tokuso Rebase-T) and two denture base acrylic resins (Lucitone 550-L e Acron MC-A). Methods: Denture base resins were packed and processed in PVC cylinders (16x16 mm) following the manufacturers' instructions. After preparing with 240 grit paper, the surfaces to be bonded were brushed with detergent (20 s), washed in distilled water, and blot-dried. The bonding sites were prepared by painting the surfaces with the bonding agents of resins U or T. A label, with a center hole (3.5 mm), was set on the treated surfaces of the denture base resins. Each cylinder was placed in a stainless steel mold with a center hole (3.5x5.0 mm), where the reliners were set. For each reline acrylic resin/denture base acrylic resin association, 20 specimens were fabricated and divided into two groups. The shear bond strength results (MPa) were obtained using a servo-hydraulic universal testing machine (0.5 mm/min.). For group 1, the tests were performed after polymerization of the reline resins and for group 2, after storage in distilled water at 37±1ºC for 30 days. Results: Results were analyzed with 2-way ANOVA and Tukey's tests (alpha=.05). The specimens relined with U showed higher (P<.05) shear bond strength (A/U-10.83 MPa; L/U-10.5 MPa) than A/T union (6.78 MPa). After water storage, the specimens A/U (14.13 MPa) and A/T (10.76 MPa), demonstrated an increased shear bond strength (P<.05). Conclusion: The relining of A denture base acrylic resin with U demonstrated the highest values of shear bond strength, particularly after water storage. Grant FAPESP 02/13728-8.