Buonocore memorial lecture. Adhesion to enamel and dentin: current status and future challenges.

TLDR

Bonding to tooth tissue can be achieved via etch‑and‑rinse, self‑etch, or glass‑ionomer approaches, and adhesives are increasingly evaluated by laboratory and clinical studies. This study demonstrates the basic bonding mechanisms to enamel and dentin through ultramorphological and chemical characterization and introduces a novel micro‑rotary fatigue‑testing device to assess biomaterial‑tooth bonds in a fatigue mode. The authors evaluate bond‑strength testing, marginal‑sealing effectiveness, and the benefits and drawbacks of etch‑and‑rinse versus self‑etch approaches, using ultramorphological and chemical analyses and the new fatigue device to assess long‑term performance. Laboratory data correlate with clinical outcomes, showing that conventional three‑step etch‑and‑rinse adhesives remain the most reliable long‑term, while mild two‑step self‑etch systems offer comparable performance with reduced technique sensitivity and application time, indicating a promising future for self‑etch approaches.

Abstract

Bonding to tooth tissue can be achieved through an "etch&rinse," "self-etch" or "glass-ionomer" approach. In this paper, the basic bonding mechanism to enamel and dentin of these three approaches is demonstrated by means of ultramorphological and chemical characterization of tooth-biomaterial interfacial interactions. Furthermore, bond-strength testing and measurement of marginal-sealing effectiveness (the two most commonly employed methodologies to determine "bonding effectiveness" in the laboratory) are evaluated upon their value and relevance in predicting clinical performance. A new dynamic methodology to test biomaterial-tooth bonds in a fatigue mode is introduced with a recently developed micro-rotary fatigue-testing device. Eventually, today's adhesives will be critically weighted upon their performance in diverse laboratory studies and clinical trials. Special attention has been given to the benefits/drawbacks of an etch&rinse versus a self-etch approach and the long-term performance of these adhesives. Correlating data gathered in the laboratory with clinical results clearly showed that laboratory research CAN predict clinical effectiveness. Although there is a tendency to simplify bonding procedures, the data presented confirm that conventional three-step etch&rinse adhesives still perform most favorably and are most reliable in the long-term. Nevertheless, a self-etch approach may have the best future perspective. Clinically, when adhesives no longer require an "etch&rinse" step, the application time, and probably more importantly, the technique-sensitivity are substantially reduced. Especially "mild," two-step self-etch adhesives that bond through a combined micromechanical and chemical interaction with tooth tissue closely approach conventional three-step systems in bonding performance.