IADR location:Goteborg, Sweden date:25-28 june 2003
Glass-ionomers are auto-adhesive to tooth tissue through combined micro-mechanical and chemical bonding. Also ‘mild' self-etch adhesives contain functional monomers that have been claimed to interact chemically with hydroxyapatite (HAp) that remained within a submicron hybrid layer. Objectives: Currently, it is not known how much chemical bonding contributes to the actual bonding effectiveness. Methods: We determined the micro-tensile bond strength (µTBS) of diverse adhesive materials to synthetic HAp (Asahi Optical), which was highly polished and thus devoid of mechanical interlocking sites.
Among the adhesives, all specimens prepared with the three-step total-etch adhesive OptiBond FL failed prior to µTBS-testing, proving that any micro-mechanical retention was excluded. The two-step self-etch adhesive Clearfil SE presented with a rather low µTBS along with a high ptf-%. Clearly, much less ptf and a significantly higher µTBS was recorded for the resin-modified glass-ionomer adhesive FujiBond LC and the conventional glass-ionomer restorative material Fuji IX. When HAp was not pre-treated, not one of the FujiBond LC specimens survived, indicating that the use of a polyalkenoic-acid conditioner significantly contributed to the chemical bonding potential of the glass-ionomers. Among the luting agents, all Panavia F specimens survived sample processing, resulting in the highest µTBS, while RelyX Unicem hardly bonded to HAp. Conclusion: Chemical bonding contributes to bonding effectiveness, but substantially depends on the material kind and composition.