Efficacy of 4 adhesive systems for amalgam. In vitro study

BACKGROUND: The aim of this research is to study the shear bond strength of 4 adhesive systems of the last generation: All-Bond 2 (AB2), Clearfil Liner Bond 2 (CL), Scotchbond MP plus (SBMP) and High Q Bond plus (HQB). According to the manufacturing company these products are suitable for amalgam adhesion to dentin. METHODS: Forty extracted human third molars have been ground to expose a flat dentin surface. The teeth were randomly assigned to 4 groups, and every group was treated with one of the adhesive system according to the manufacturer's instructions. Samples were then secured in a split Teflon mould, having a 6 mm diameter opening and a spherical amalgam was triturated and condensed onto the treated dentin surfaces. The amalgam cylinders have been exposed to a tensile bond test using a Universal Testing Machine (Instron 4500). ANOVA test has been used to the statistic study among groups. RESULTS: The study of the tensile mean range, showed that dentin shear bond strength values (MPa) for the adhesive systems tested were: 8.13 +/- 1.48 for AB2, 7.06 +/- 1.41 for SBMP, 4.2 +/- 1.06 for HQB, 3.04 +/- 0.68 for CL. The statistic test revealed significant differences among the 4 groups (p < 0.05). CONCLUSIONS: The bond strength mean values of amalgam adhesives are lower than the ones for composite resins, nevertheless dentin-enamel adhesive systems specific for amalgam have to be taken into consideration particularly in case of conservative restorations that need chemical retention as a support, when the mechanical one is not enough.