Abstract
The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.
Highlights
The study verified the bond strength in simulated dental restorations of siloraneor methacrylate-based composites repaired with methacrylate-based composite
This study evaluated the bond strength of methacrylateor silorane-based samples repaired with methacrylate-based composite before and after thermocycling procedures
It is possible that the chemical adhesion between new and old resins did not establish a reliable bonding in chemical conditions, considering that the quantity of free radicals decreases with the aging of dental restoration (10)
Summary
The study verified the bond strength in simulated dental restorations of siloraneor methacrylate-based composites repaired with methacrylate-based composite. Higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin. Different surface treatments produce different bond strengths for the repair of recent restorations of silorane- and methacrylate-based composites (4). These factors are the rationale to verify the behaviour of repair in the composite restorations. Surface roughness can be mechanically obtained by means of diamond points or blasting with aluminum oxide particles and chemically etched with hydrofluoric or phosphoric acid Both procedures are employed to remove the aged layer of resin and create roughness for increasing the bond strength. Different from the traditional system of polymerization, silorane-based composites use the cationic
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