Dentin shear bond strength of compomers and composites

The aim of this study was to compare the shear bond strengths and fracture characteristics of two compomers bonded with a single step bonding agent with two modern composites, a microfil and hybrid, bonded with a fourth generation bonding agent.

Freshly extracted human third molars were sectioned parallel to the occlusal surface to expose midcoronal dentin, prepared with 320-grit surface finish, and bonded (N = 11 samples/group) following manufacturer's directions with the compomers (Dyract, DeTrey Konstanz, Germany or Compoglass, Vivadent, Schaan Liechtenstein) or the dentin bonding agent SMP+ (Scotchbond Multi-Purpose Plus, 3M Dental Products, St. Paul MN) with Silux Plus or Z100 (3M Dental Products, St. Paul, MN). The samples were tested using a single plane lap shear bond strength test at 5 mm/min until failure. Statistical analysis was performed using ANOVA with Scheffe multiple comparison testing. Fracture surfaces of the debonded surfaces were examined using SEM to determine the failure mode of each specimen.

Bond strengths for the compomers were 12.7 +/- 2.9 MPa for Dyract and 8.9 +/- 4.1 MPa for Compoglass and were not significantly different. Bond strengths for the dentin bonded composites were significantly stronger than the compomer Compoglass, but were not different from one another, despite the use of different composites. The averages values for SMP + /Silux Plus and SMP + /Z100 were 15.7 +/- 4.5 MPa and 15.2 +/- 5.6 MPa, respectively. SEM analysis showed that all materials exhibited mixed failure patterns. Compoglass specimens exhibited 5 of 11 failures classified as adhesive, while each of the other materials showed only 1 of 11 adhesive failures.

Compomers have undergone rapid development over the last several years, but their bond strengths have not yet reached the same level as modern dentin bonded composites. Difference in composite filler type and amount had little influence on the bond strength determined in this work.