EARLY TENSILE BOND STRENGTHS OF SEVERAL ENAMEL AND DENTIN BONDING SYSTEMS

Tensile bond strength tests are commonly used for the evaluation of ad hesive dental materials. The majority of these tests are carried out a fter 24 h of storage in water. However, determination of the early ten sile bond strength could be more important, especially in relation to gap formation between the cavity surface and the restorative material. This study investigated the tensile bond strengths of five enamel/den tin bonding systems and two experimental dentin bonding systems. Tensi le bond strengths were obtained at one min, ten min, and 24 h after th e resin composite was cured. Bond strengths at the early stages were a lways somewhat less than the 24-hour test results. For the enamel/dent in bonding systems, a significant difference was found between the ena mel and dentin bond strengths at all time periods, except with Superbo nd D-liner and Liner Bond. The experimental group with glyceryl methac rylate as the primer produced a good 24-hour result (14.3 MPa), but th e early bond strengths were no different from those in the non-primer- treated groups. It was concluded that this material may actually retar d the polymerization of the bonding resin. Previous workers have sugge sted that a tensile bond strength in the order of 20 MPa is necessary for gap-free restorations to be obtained. Should this be the case, the n all of the materials tested, from the aspect of early bond strength, lack the strength for prevention of gap formation, although Superbond D-liner and Liner Bond approached this hypothetical figure. These sys tems, Superbond D-liner and Liner Bond, also exhibit small differences between the enamel and dentin tensile bond strengths.