Laboratory evaluation of compomers in Class V restorations

To evaluate the in vitro microleakage, marginal morphology and resin tags configuration of a compomer restorative material (Dyract) alternatively used with two different bonding systems (Dyract-PSA and Prime & Bond 2.0). A hybrid resin composite (Prisma TPH) used with two different bonding systems (Universal Bond 3 and ProBond) was evaluated as control material.

Class V non-retentive restorations were made in vitro at CEJ and divided at random in four groups: Dyract/PSA, Dyract/P&B 2.0, Prisma TPH/UB3, and Prisma TPH/ProBond. The latter two groups were as controls. After finishing the restorations, an impression material was used to obtain an epoxy resin replica for SEM analysis of margin alterations. Percentage of perfect margin was evaluated under SEM and calculated comparing it with the width/length of restoration margin. The presence of gaps, enamel fractures and other marginal alterations was also recorded inspecting under SEM replicas. Each tooth was then immersed for 24 hours in erythrosin B dye solution at room temperature and evaluated at superficial margins as marginal leakage (ML) for dye penetration. Each sample was then longitudinally sectioned, and leakage was expressed as % dye penetration of the total cavity wall, longitudinal leakage (LL). Finally, each tooth was dissolved (10%H3PO4 for 48 hours and NaOCl solution for additional 24 hours) to leave only the resin restoration. The internal walls of each restoration were then inspected by SEM at x1,000-15,000 to evaluate the presence of resin-dentin infiltrated layer (hybrid layer) and to calculate the ability of primer/bonding to infiltrate peritubular dentin and to form resin tags.

Gap widths were 2-6 microns at dentin and lower at enamel. Several enamel fractures along the margin were observed. Resin tags were observed only in deeper dentin. Only Prime & Bond 2.0/Dyract formed resin tags at medium-superficial dentin. The length of resin tags ranged from 1-6 microns for Dyract-PSA primer to 100 microns for Prime & Bond 2.0. Marginal and longitudinal leakage was observed both at dentin and enamel levels. The best dentin seal was obtained with Prime & Bond 2.0/Dyract, while enamel seals were equivalent with both bonding systems (P > 0.05). No correlations were demonstrated between leakage and SEM observations.