Comparison of two video-imaging instruments for measuring volumetric shrinkage of dental resin composites.

Objectives: The purpose of this study was to measure the polymerization shrinkage of three dental resin composites using two commercially available video-imaging devices to determine if the devices produced equivalent results.

Methods: Small, semi-spherical specimens of a microhybrid (Venus), microfill (Filtek A110), and flowable (Esthet*X Flow) resin composite were manually formed and light activated for 40s using a light-curing unit. The volumetric polymerization shrinkage of fifteen specimens of each brand of resin composite was measured using the AcuVol and the Drop Shape Analysis System model DSA10 Mk2 (DSAS) video-imaging devices. Mean volumetric shrinkage values were calculated for each resin composite and equivalence was evaluated using the two one-sided tests approach. Differences between the means that were less than approximately 5% of the observed shrinkage were considered indicative of clinical equivalence.

Results: Mean volumetric shrinkage values measured for the resin composites were: Venus (AcuVol, 3.07+/-0.07%; DSAS, 2.90+/-0.07%); Filtek A110 (AcuVol, 2.26+/-0.10%; DSAS, 2.25+/-0.09%); and Esthet*X Flow (AcuVol, 5.01+/-0.17%; DSAS, 5.14+/-0.11%). Statistical analysis revealed that the two imaging devices produced equivalent results for Filtek A110 and Esthet*X Flow but not for Venus.

Conclusions: Video-imaging systems provide an easy method for measuring volumetric shrinkage of resin composites. As with other methods for measuring volumetric shrinkage, however, they are best used to comparatively measure different materials within the same laboratory.