Abstract
The purpose of this review was to identify the various factors involved in polymerization shrinkage of dental composites and to discuss possible strategies of overcoming this drawback. The final setting reaction of dental composite material is followed by polymerization shrinkage of the material which leads to shrinkage stress and strain. This shrinkage stress and strain could result in debonding of the material, cuspal flexure, fracture of the tooth, microleakage and poor mechanical properties. PubMed and Google scholar databases were used to search through the past 30 years of literature using selected search criteria "Dental composite*[TW] AND (shrinkage*[TW] OR stress*[TW] OR strainITWD" to identify articles/book chapters discussing polymerization shrinkage and possible solutions. In total 46, articles/book chapters met the criteria for inclusion in the literature review.
There were multiple factors that were identified to have an impact on polymerization shrinkage and consequently shrinkage stress and strain, which included the composition and viscosity of the material, modulus of elasticity acquired by the material, rate of polymerization, configuration factor and degree of conversion. On the other hand, the methods which could help minimize shrinkage involved alteration to the material including change in particle size, incorporation of inhibitors, and addition of silorane as well as use of various clinical techniques. It can be concluded that various strategies have been implemented to overcome the shrinkage stress and strain related to dental composites, however, further research is required to help in the development of the material. In addition, improvement in the placement techniques of the material needs further exploration to reduce this complication.