One of the main problems influencing longevity of dental restorations is shrinkage of the resin/ceramic composites during their polymerization precess. The resin shrinkage results in developing of high stresses between the composite and the wall of the tooth. When the stresses are too high the failure of the bonded interface occurs, with possible margin failure, secondary caries and need for re-restoration.
The aim of the study was to investigate an influence of ceramic contribution in the dental composite on its polymerization shrinkage. Moreover, the influence of resin shrinkage itself on the whole composite shrinkage was investigated.
In 3-D linear elastic finite element analyses, the process of shrinkage of dental resin/ceramic composites during their polymerization was simulated using Ansys ver. 5.4. The influence of the ceramic contribution and resin shrinkage on the shrinkage of the dental composites was investigated.
The composites were modeled as the bricks with different volumetric contribution (from 0% up to 70%) of ceramic aggregate. The aggregate was represented in the model by the balls with radii of 0.15 micrometers. Volumetric resin shrinkage of 3%, 9%, 12%, and 30% was applied to the composite brick via the thermal analogy.
Results & discussion
Quantitative estimates have been obtained of the reduction in the composite shrinkage with increase of volumetric contribution of the ceramic aggregate or decrease of shrinkage of the resin. It was also found that when the shrinkage of the composite resin is below 5% the influence of the aggregate contribution in the composite can be neglected. However, for the resin shrinkage of over a dozen percentages the contribution of the ceramic aggregate has a crucial influence on the shrinkage of the composite.
This study indicates that by proper changing of the aggregate contribution and resin shrinkage the lower shrinkage of the dental composite may be obtained.