Restorative materials for children
Amalgam has been the most popular restorative material for posterior teeth for many years for adults and children. It is a hard-wearing material which is both economical and easy to use, but there is no adhesion to dental tissues and its retention relies on having cavities that have some degree of undercut. Furthermore, there have been concerns in recent years regarding the safety of the material, as mercury is one of the main constituents and in a number of countries its use in primary teeth has been limited (e.g. in Sweden, but for environmental reasons). Nevertheless amalgam still remains a durable and widely used material in children.
This is a material that is likely to be the future replacement for amalgam as a posterior restorative material. Also because it is tooth coloured, it is the material of choice for anterior restorations. It has reasonable wear resistance and, when used with the acid-etch technique, has adhesive properties which obviate the need for mechanical retentive means as described for amalgam restorations. The earlier composite materials were a two paste system of a base and catalyst, but nearly all modern versions are polymerised by use of a curing light giving the advantage that the setting of the material is under the control of the operator. The main disadvantage of composite resin is that it is technique sensitive and any contamination, such as by moisture, will prevent adequate adhesion. Also there is considerable polymerization shrinkage on curing and therefore a large cavity needs to be filled and cured in a number of small increments.
Glass ionomer is a restorative material which comes in two main forms. As a cement it consists of a base and an acidic water soluble powder. The resultant combination is set by a chemical reaction to form a material that is susceptible to wear and fracture. It does have the benefit of adhesive properties and contains fluoride, thus providing some cariostatic effect on surrounding dental tissues. More recently introduced are the resin-modified glass ionomers which, as the name suggests, have a resin incorporated; this provides greater fracture and wear resistance as well as the ability to be polymerised by a curing light.