Repair bond strength of resin composite to restorative materials after short- and long-term storage.

Objectives: To investigate short- and long-term bond strength ("repair bond strength"; RBS) of a resin composite to six restorative materials using either a silane and a bonding agent or a universal "one-step self-etch" adhesive system.

Methods: Specimens were produced from an amalgam, a direct resin composite, two indirect resin composites, a hybrid ceramic, and a feldspar ceramic and stored for 3 months in tap water (37 °C). All specimens were then sandblasted (AlO; 25 μm) and either treated with Monobond Plus and OptiBond FL Adhesive (MP-OFL) or with Scotchbond Universal (SBU). Filtek Z250 was used as "repair composite", and RBS was measured by means of a micro shear bond strength test after 24 h or after 1 year. RBS values (n = 15/group) were statistically analyzed (α = 0.05).

Results: RBS (MPa; mean values (standard deviations)) after 24 h for MP-OFL: 18.6 (3.2)-23.9 (5.0) and for SBU: 12.5 (4.9)-18.1 (4.6); after 1 year for MP-OFL: 8.9 (4.6)-19.8 (4.3) and for SBU: 5.6 (2.3)-18.8 (3.5). After 24 h, MP-OFL showed significantly higher RBS to the hybrid ceramic and the feldspar ceramic than did SBU (p ≤ 0.0001) whereas there was no significant difference in RBS for the other four restorative materials. After 1 year, MP-OFL showed significantly higher RBS to the feldspar ceramic than did SBU (p = 0.043) whereas there was no significant difference in RBS for the other five restorative materials.

Significance: The use of a silane and a bonding agent seems more versatile for repairing restorations than the use of a universal "one-step self-etch" adhesive system.