The marginal seal of Class II restorations: flowable composite resin compared to injectable glass ionomer

The objective of this study was to investigate the effect of a flowable composite resin (Tetric Flow) versus an injectable glass ionomer (Fuji II LC) on microleakage at the cavosurface margin of the proximal box of Class II restorations in permanent teeth in-vitro. Thirty caries and restoration-free human bicuspids were prepared with mesial and distal slot preparations and were filled either with a bonding agent (Optibond) plus a flowable composite resin (Tetric Flow), Group I; bonding agent (Optibond) plus a flowable glass ionomer (Fuji II LC), Group II; or a flowable glass ionomer (Fuji II LC) with no bonding agent, Group III. All specimens were then immersed in a 2% solution of basic fuschin dye for 24 hours to allow for dye penetration into possible existing gaps. These teeth were then carefully sectioned mesially/distally into two pieces using an Isomet saw. The teeth were then studied under a binocular microscope to measure depths of dye penetrations as an indication of marginal microleakage at the gingival cavosurface margin and scored as follows: 0 = no dye penetration, 1 = dye penetration into enamel only, 2 = dye penetration into enamel and dentin, 3 = dye penetration into the pulp. The specimens were also evaluated using a SEM. The results showed that there were statistically significant differences between Groups I (Tetric Flow) and (Fuji II LC plus bonding agent), II in favor of Group I; between Groups I and (Fuji II LC with no bonding agent), III in favor of Group I; as well as Groups II and III in favor of Group II (Fuji II LC plus bonding agent). Group I (bonding agent plus flowable composite resin) showed significantly less microleakage. Group II (bonding agent plus flowable glass ionomer) demonstrated a bond that existed between the bonding agent and the glass ionomer but microleakage within microgaps of the glass ionomer itself Group III (flowable glass ionomer plus no bonding agent) demonstrated significant microleakage between the glass ionomer and tooth structure, microgaps within the glass ionomer, and lack of retention of the restoration. It appears that the use of a flowable composite resin (Tetric Flow) plus a bonding agent (Optibond) in the proximal box of a Class II restoration in permanent teeth will significantly reduce the microleakage at the cavosurface margin when compared with an injectable glass ionomer (Fuji II LC) with or without a bonding agent (Optibond).