Bond strength between resilient denture liners and different acrylic resins

Objectives: this study evaluated the tensile bond strength of 2 resilient denture liners processed against 3 heat-polymerized denture base acrylic resins, polymerized by different polymerizing cycles (with water bath and microwave energy). Methods: Tensile specimens consisted of 2 segments of acrylic resin (SR Triplex, Lucitone 550 or Acron MC) measuring 60 × 10 × 10 mm each, and a central segment of resilient liner (Eversoft or Molloplast-B) of 3 × 10 × 10 mm. Ten specimens for each liner/resin combination, were prepared and polymerized as follow: SR Triplex, 100ºC for 2 hours; Lucitone 550, 73ºC for 90 minutes, plus 2 hours at 100ºC; and Acron MC, microwave activation at 850W for 10 minutes. Specimens were placed under tension until failure in a universal testing machine, at a crosshead speed of 5 mm/min. Mean bond strength was calculated and expressed in megapascal, and the type of failure was determined by use of stereoscopic microscopy and recorded as being cohesive, adhesive, or mixed. Data were analyzed by one-way ANOVA and Tukey HSD test (P<.05). Results: Polymerization of both resilient liner materials by microwave energy resulted in significantly lower bond strength values (P<.05) when compared with the groups polymerized in the water bath. The highest mean bond strength values were presented by Molloplast-B groups when processed against Lucitone 550 (1.41 ± 0.15 MPa) and SR Triplex (1.40 ± 0.10 MPa) acrylic resins. Eversoft demonstrated the lowest bond strength values, regardless of the acrylic resins it was bonded to. Conclusion: the acrylic resins and their respective polymerization cycles affect the bond strength of both resilient liners tested. Polymerization by microwave activation produced the lowest bond strength values in both resilient liners.