Methods: Eighty half hour-glass slabs were prepared (Grandio, VOCO, GmbH. Cuxhaven, Germany), and were divided into 8 groups (n=10) according to the bonding protocols employed. All half-slabs were wet ground using high-speed abrasive burs and immediately repaired using a 3-step etch-and-rinse adhesive (Solo bond Plus, VOCO). Forty slabs were repaired using wet bonding with or without silane pretreatment. The other forty were repaired using dry bonding. The immediately repaired slabs were tested either after 24-hours or one-month. Complete intact slabs (n=10) were prepared and tested in tension after a 24-hours storage period. TBS was performed at a cross-head speed of 0.5 mm/min. Failure modes were evaluated using a stereomicroscope at 40X. Two-Way ANOVA was run to test the effect of bonding protocols, testing time and their interaction on the immediate repair TBS.
Results: Two-Way ANOVA revealed that both bonding protocols and testing time had a significant effect of the repair TBS (p=0.001). The interaction between the independent variables (protocols and testing time) had no significant effect (p=0.234). The repair TBS ranged from 40%-61.9% after 24-hours and from 26%-53.1% after one-month in comparison with the TBS of the intact-slabs.
Conclusions: Based on the TBS results, repair bond strength significantly dropped after one-month storage in water for all bonding protocols except for the wet bonding with silane pretreatment protocol. Dry or wet bonding had no effect on the immediate repair bond strength of nano-hybrid restorative composite. Silane treatment did not improve the immediate repair bond strength.
The authors would like to thank the VOCO Company (VOCO, GmbH. Cuxhaven, Germany) for supplying the materials used in this study.