The Effects of Bioactive Glass on Bonding to Dentin
Since the introduction of adhesive dentistry in the 1950s, leakage has been a major problem affecting the dentin bonding process. The micromechanical nature of the bond leaves it vulnerable to hydrolytic and enzymatic degradation, reducing the strength and lifetime expectancy of the restoration. Bioactive glasses are known to promote the formation of apatite in aqueous environments that contain calcium and phosphate (e.g. saliva); it is hypothesized here that their presence at the bonded interface will improve the quality of the resin-dentin bond through self-sealing caused by the formation of apatite, in the presence of leakage. Determination of the relative success of incorporation of bioactive glass into the dentin bonding process requires assessment of the ability of the glass to reduce leakage, as well as its effect upon the strength of the bond. Leakage was measured by both a silver nitrate method and a methylene blue method. The ability of microparticles of commercially available bioactive glass to infiltrate etched dentin was tested, and hybrid layer formation and leakage were assessed by SEM and EDX. A novel bioactive glass containing fluoride and magnesium was made, and the same tests were applied to teeth that were vacuum-deposited with microparticles of this glass powder. The effects on bond strength of the presence of bioactive glass at the bonded interface were tested by the single plane lap shear test, and the failure modes investigated by SEM. Finally, bioactive glass powder was incorporated into a commercially available adhesive, and the effects on leakage and bond strength were investigated. Both the commercially available glass and the novel glass were found to reduce leakage with no negative effects on bond strength, either when vacuum-deposited into etched dentin or when incorporated into adhesive.