Microleakage and polymerization shrinkage of various polymer restorative materials

The aim of this in vitro study was to evaluate the polymerization shrinkage and the microleakage of direct resin-based restorative materials commonly used in pediatric dentistry.

Standardized Class V cavities overlapping the cementoenamel junction were prepared on the buccal and the lingual surfaces of 40 extracted human mandibular third molars (36 specimens, 4 controls). The cavities were restored with 4 different materials: a packable resin composite (Filtek P60), a compomer (Compoglass F), an ormocer (Admira) and their associated bonding agents (Scotchbond 1, Excite, and Admira Bond, respectively), and a resin-modified glass ionomer (Fuji II LC). The teeth were then immersed in methylene blue solution for 48 hours. Dye penetration was evaluated for all materials, which were analyzed using a multivariate model (alpha=0.05): influence of microleakage score, margin location (enamel/cementum), and preparation location (buccal/lingual). Multivariate analysis was performed using a polychotomous logistic regression. Polymerization shrinkage was evaluated by the disk deflective method. The percentage of polymerization shrinkage (N=3) was evaluated by ANOVA and Tukey test.

Regarding polymerization shrinkage, the P60 demonstrated the lowest value, followed by ADM and COF, whereas FLC presented the highest shrinkage-strain (P<.0001). The preparation location had no significant effect on dye penetration (P=.86). Margin location (enamel or cementum) had a significant effect on microleakage (odds ratio [OR]=24.61). Significant differences in the microleakage patterns and scores were also observed between the 4 restorative materials. Admira exhibited the lowest overall microleakage. In comparing Filtek P60, Compoglass F, and Fuji II LC to Admira, P60 showed significantly less microleakage (OR=1.30) than Fuji II LC (OR=1.47), whereas Compoglass F demonstrated the greatest significant overall microleakage (OR=3.15).

Within the experimental conditions of this in vitro study, the microleakage was significantly lower at the enamel margins than at the cementum margins for the four restorative materials tested. The ormocer and the packable resin composite exhibited the best sealing ability, as well as the lowest polymerization shrinkage. It could not be demonstrated in this study, however, that the higher the polymerization shrinkage was, the lower the marginal sealing ability was.