Shrinkage of restorative materials remains a major concern because it can cause residual stresses that have been associated with various clinical symptoms. Not all contraction during polymerization contributes to residual stresses.
An experimental method was developed by Dr. Antheunis Versluis and others in the MDRCBB to determine the post-gel shrinkage component (responsible for residual stress development) during polymerization using bi-axial strain gauges.
More recently, Dr Alex Fok and Dr Jianying Li developed a noncontact shrinkage strain measurement technique using digital image correlation (DIC). The new technique can provide more detailed, full-field strain distribution of dental restorative materials undergoing polymerization shrinkage.