A Critical Appraisal of Dental Adhesion Testing

The various methods used to investigate dental adhesion are reviewed. Concepts from fracture mechanics are used to interpret adhesive and cohesive failure of adhesives used in dentistry and to analyze bond strength testing techniques. The practical strength of an adhesive interface is a complex relationship between the stress distribution, specific adhesive fracture energy and the size and shape of interfacial defects. Bond strength tests are not designed to investigate these separate aspects related to adhesive failure. The problem of defects in dental adhesive failure are unique in that the number, size and shape of defects which result in failure are mainly technique related. However, the investigation of dental adhesive failure can generally be characterized as ignoring the relationship that specific adhesive fracture energy and defects have on the practical strength of adhesive systems. Based on theoretical considerations we propose that dental adhesion testing be reevaluated from a theoretical, experimental and most significantly from a practical viewpoint.