**3. Compomers (Polyacid-modified resin composites)**

Polyacid-modified composite resins, known trivially as compomers, are a group of aesthetic materials for the restoration of teeth damaged by dental caries. They were introduced to the profession in the early 1990s [40], and were presented as a new class of dental material designed to combine the aesthetics of traditional composite resins with the fluoride release and adhesion of glass-ionomer cements. The trivial name was devised from the names of these two "parent" materials, the "comp" coming from composite, and "omer" from ionomer [60]. The term *polyacid-modified composite resin* was originally proposed for these materials in 1994 [39] and has been widely adopted both by manufacturers and researchers since that time. However, it has been criticised on the grounds that it ". . .may overemphasize a structural characteristic of no or little consequence" [60]. This is a somewhat strange criticism, since to formulate these materials, manufacturers have modified them specifically by the introduction of acid functional macro-monomers. They are, therefore, without question "polyacid modified". Whether this modification confers clinical benefits, or indeed whether these materials can usefully be considered to be distinctive materials is more debateable. The conclusion of Ruse is that ". . . They are, after all, just another dental composite", but this seems to the present author to be somewhat extreme, and there is considerable evidence that compomers possess characteristic properties, and are therefore distinct from conventional composite resins [50, 55, 60, 85].
