The aim of this study was to evaluate the macroshear bond strength and the thickness of the hybrid layer obtained by using the etch-and-rinse and self-etching adhesive systems on caries-affected and sound dentin.
Method:
A total number of 120 extracted human molars were collected and grounded to expose oclusal sound or caries-affected dentin. Differentiation between both substrates was carried out according combined criteria of visual examination and staining with a caries detector solution. The specimens were asigned to two groups (n = 60) according to the dentin substrate and further randomized within each group into three subgroups according to adhesive system: etch-and-rinse, Adper-Single-Bond 2/Filtek-Supreme XT (ASB-FS), Prime&Bond NT/CeramX-Mono (PB-CXM); and self-etching, AdheSE-One/Tetric-EvoCeram (AO-TEC). Half the samples served to evaluate the macroshear bond strength. Adhesives were aplied to selected substrate and composite cylinders (4x4 mm) were formed. After 24h, specimens were subjected to macroshear bond testing at a crosshead speed of 1mm/min. The other half of the samples was hybridized and restored with composite resin, than sectioned in order to investigate the thicknes of the hybrid layer with SEM. Data were statistically analyzed using T-test, ANOVA and Mann-Whitney U-test.
Result:
The significantly lowest macroshear bond strength values were obtained with self-etching adhesive system AO-TEC on caries-affected (6.73±1.66 MPa) and sound dentin (7.00±2.05 MPa). The etch-and-rinse adhesive system ASB-FS revealed highest values on sound (10.56±3.50 MPa) and caries-affected dentin (10.06±2.55 MPa). SEM observation showed no significant differences of the hybrid layer thickness. However, the hybrid layers created on caries-affected dentin are thicker than those on sound dentin for all tested adhesive systems.
Conclusion:
The etch-and-rinse adhesive systems produce higher bond strength than self-etch adhesive system. The hybrid layer thickness is not adequate parameter that represent quality of bonding effectiveness of adhesive systems to dentin.