Critical Elements of Bonding Success
Bonded resin composites are the most frequently placed direct tooth-colored restoratives and, released from the constraints of classical preparations required for amalgam restorations, clinicians are now able to remove the minimal amount of tooth structure required for caries removal with no requirement for a retentive preparation form.
As such, resin composite restorations can play a positive role in the drive towards minimally invasive dentistry. A number of elements are critical for the success and durability of composite restorations. Selecting a composite with suitable properties including esthetics, high compressive and tensile strength, and minimal polymerization shrinkage is critical. Proper use of a resin adhesive, isolation such that a dry field is obtained for composite placement, careful attention to placement and final form, and marginal integrity are essential. Resin composite restoration success rates can be outstanding, and clinical studies have demonstrated that long-term success with bonded composite restorations is possible. Success, however, requires that both a suitable bonding agent and an appropriate technique are used.1,2,3 In one 8-year prospective study an annual failure rate of 2% was observed,4 while a review of multiple studies of at least five years? duration has shown an annual failure rate of 1% to 3%, with secondary caries being the most common cause of repair/replacement.5 From the patient?s perspective, the definition of success would be a restoration that is comfortable (pain-free), functional, and esthetic.
It was only following the introduction of adhesive technology that composite resins became a reality in dentistry and since their original introduction, adhesive systems have advanced dramatically. The first adhesive systems were based on etching of only enamel while, later, removal of the dentin smear layer by etching was also performed along with use of a hydrophilic monomer to obtain some adhesion to dentin. At the current time, a plethora of adhesive systems and resin composites is available to choose from?however, not all are created equal nor are they all universally compatible. Adhesive systems are arguably misunderstood yet they are the most important factor in successful short- and long-term outcomes for bonded resin composite restorations. Use of a compatible adhesive system in the manner intended is essential and adhesive systems for resin composites have been categorized in several ways. The generational classification is sequential and based on when the adhesive system was introduced. The sequence does not however correlate to the technique used (Table 1). A simpler method is to base categories on two simple measures?whether they are etch-and-rinse (total etch) or self-etch adhesives. Within this simple classification, the subsets are then based on the number of containers required for the system. Thus, etch-and-rinse adhesive systems can be broken down into 3-step, 3-bottle systems