Measuring Polymerization Shrinkage Stress on the Tooth Structure

Composite resin materials are popular dental restorative materials because of their esthetic nature and ability to be directly bonded to teeth. However, they have a volumetric shrinkage of 2.4% to 2.8% upon polymerization, which exerts stresses on the tooth structure via the bonding interface. This stress can lead to a host of clinical complications.

Recently, a new class of composite resin materials has been introduced to the market that claims to reduce the amount of polymerization shrinkage stress exerted on the tooth structure. If the restorative materials perform as indicated, dentists would be able to fill teeth with direct tooth-colored restorations much faster than with current materials, while patients would experience less sensitivity and complications.

The University of North Carolina's School of Dentistry put the new resin materials to the test by measuring the amount of shrinkage stress they exert on the tooth structure, using strain gages to measure tooth deformation as the materials polymerize. Micro-Measurements strain gages were chosen for this study because extremely sensitive equipment was required; recorded linear tooth deformation would amount to just a few micrometers. With Micro-Measurements strain gages, the university was able to determine that new bulk-fill composite resins exert less polymerization shrinkage stress when compared with conventional composites placed incrementally.

Click here to read the full Case Study: Effect of Dental Composite Type and Placement Technique on Polymerization Shrinkage Stress