Dimensional stability of dental restorative materials and cements over four years

While the polymerization shrinkage of some restorative materials is well-recognized among dentists, the problem and extent of dimensional expansion has received a relatively small amount of study. The tooth or restorative material may risk fracturing if the net expansion exceeds the amount of shrinkage. This study measured the linear dimensional change of dental restorative materials and cements stored in water for four years immediately after curing. Cylindrical specimens were made according to manufacturer's recommendations for each of 19 materials. After four years, five of the 19 materials were affected by net shrinkage; the remaining 14 underwent net expansion. One product's linear expansion exceeded 3.5%, which corresponds to over 10% volumetrically. Dentists should consider long-term dimensional stability data when selecting materials for clinical use.