Polymerization shrinkage and stress analysis during dental restoration observed by digital image correlation method.

Mechanistic polymerization shrinkage and stress behaviors of dental composite resins Filtek P90 (3M ESPE, USA) and Clearfil AP-X (Kuraray, Japan) were investigated using CCD camera and digital image correlation (DIC) method during and after light irradiation. For both resins, the interior of the resin part exhibited greater radial shrinkage strain (εr) due to more mobility than the resin margin near the interface of the substrate ring, where a non-symmetric distribution of εr was observed with a peak away from the center. DIC experiments on the specimen surface showed that the maximum principal stresses obtained along the margin were 1.5–8.4 times larger than the corresponding values by FEM. The non-symmetric shrinkage and the large shrinkage rate during light irradiation caused a significant increase in the principal tensile stress along the interface at cured state. [ABSTRACT FROM AUTHOR]