Clinical requirements for a successful 'sandwich'--dentine to glass ionomer cement to composite resin.

The composite resins are now being used extensively in restorative dentistry although there are still some problems remaining. Long-term prevention of microleakage continues to be an area of controversy particularly in relation to the margins between dentine and composite resin. Chemical adhesion between glass ionomer cement and dentine is accepted as being a long-term union and it has recently been shown that a mechanical union is possible between composite resin and glass ionomer cement. This has led to the development of the so-called 'sandwich technique' where glass ionomer cement is used as a lining under composite resin restorations particularly where the cavo-surface margin is in dentine. This paper discusses the various levels of adhesion in the 'sandwich' and suggests the best methods of obtaining optimum results from the clinical application of the technique. Particular attention is drawn to the wide variation in the strength of the union depending on the materials used and the methods of handling.