cosmetic dentistry_ beauty & science

18 I I clinical technique _ SDR _Recent developments in composite resin materials and bonding technology have made theroutineuseofthesematerialsinposteriorteeth possible.1 Directposteriorcompositeresinrestora- tionsarenowpredictableanddurable,andinmany instances their superior aesthetic and tooth-sup- porting properties make them the ideal treatment optionwhenrestoringtheposteriordentition.2 The main shortcomings of composite resin materials are polymerisation shrinkage3 and polymerisation stress. Polymerisation stress can result in contrac- tion forces on the cusps that can result in cuspal deformation,4 enamel cracks and ultimately de- crease the fracture resistance of the cusps.5 Cavity configuration and the method of in- sertion of composite resin into the cavities can influence the gaps at the interface between the dentine/enamel and the restoration.6 According to Davidson and De Gee,7 the parallel walls of a box-shaped cavity may restrict the flow of com- posite during polymerisation, causing stresses at the resin–dentine interface.8 The present generation of chemically or light- activated flowable composites undergoes free volumetric shrinkage of 4 to 9 % as compared with regular viscosity and packable composites at 2 to 5 %, with an average of 3.5 %. According to Jensen and Chan, polymerisation shrinkage stresses have the potential to initiate failure of thecomposite–toothinterface,whichcouldcause deformation of the tooth, which in turn might re- sult in post-operative sensitivity and which could even open pre-existing enamel microcracks.9 SDR Smart Dentin Replacement (DENTSPLY DeTrey) is marketed as a low stress flowable base materialthatcanbeplacedinlayersofupto4mm cosmeticdentistry 4_2011 Clinical application of a new flowable base material for direct and indirect restorations Author_ Prof Peet van der Vyver, South Africa Fig. 3a Fig. 2Fig. 1 Fig. 3b