Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
The use of composite materials for dental fillings has become more common due to demands for more esthetic filling materials and a national ban against using mercury-containing products, among others dental amalgam. However, one of the drawbacks with composites is their polymerization shrinkage. Filler particles are incorporated into composites among other things to minimize the shrinkage. The sizes of the filler particles have in recent years become smaller and most composites have nano-particles incorporated.
The aims of the study were to investigate if a) the filler load, b) the curing time and c) tested after "best-before date" will affect the polymerization shrinkage of commercial dental composites. The hypotheses are that high filler loads will result in low shrinkage, and that different curing times and tested after "best-before date" will not significantly affect the shrinkage.
The polymerization shrinkage of ten commercial composites was studied and three different curing times were used. 150 specimens were manually formed and AcuVol was used to register the volumetric shrinkage.
The mean volumetric polymerization shrinkage values of the composites ranged between 1.8% and 5.0% for the recommended curing times. The composite with the highest filler load (Kalore) had the lowest mean shrinkage, and the composite with the lowest filler load (SDR) had the highest mean shrinkage.
The video-imaging device could be used to register the polymerization shrinkage of dental composites. The composites polymerization shrinkage was related to the filler loads when the composites were arranged in groups based on their type. No conclusion could be made about the effect of different curing times and "best-before date".