Adhesive dental materials and their durability

Adhesive materials are used in dentistry because they are conservative and generally aesthetic, i.e. tooth coloured. Two main classes of material are involved, the glass-ionomer cements and the composite resins. This review describes the way they are bonded to the tooth and highlights their differences. Glass ionomers develop a zone of interaction with the tooth as they age which ultimately gives an extremely strong bond, and results in excellent retention rates. By contrast, bonding of composite resins is more complicated and possibly less effective, though these materials have better wear resistance and better aesthetics than glass ionomers. Assessment of bond durability is difficult. This is because a dental restorative can fail by a number of mechanisms apart from debonding: for example, through wear or fracture. The tooth may also show additional decay (secondary caries), hence the filling may need to be replaced. Clinical studies of survival tend to be as much concerned with these aspects as with the bond between the restoration and the tooth. Results from these clinical studies suggest that the various types of adhesive bond survive well in the demanding service conditions of the mouth.