Microleakage of Class II composite restorations

(1) To evaluate the in vitro sealing ability of several Class II resin restorations whose gingival extension of the proximal margin was apical to the cemento-enamel junction and in dentin and (2) to determine the effect of thermocycling on leakage into the resin-tooth interface.

Mesio-occlusal and distoocclusal preparations were made in extracted human molars. The gingival floor of the proximal box, was placed 1.0mm apical to the CEJ, and was prepared to a width of 1.5mm from the cavosurface margin to the axial wall. The teeth were restored with one of seven restorations (Z100 control, Z100, Wave, F2000, Surefil, Z100 and Vitrebond Sandwich A, Z100 and Vitrebond Sandwich B) using multiple incremental placement and materials. Following storage, half the samples were thermocycled. All 70 samples were stained using silver nitrate. The entire resin restoration was then removed from the proximal box ,and starting at the cavosurface margin the gingival floor was divided into three zones of 0.5 mm each and analyzed for dye penetration, using a novel technique which utilized the aid of computer imaging software and assessed both quantitatively and qualitatively.

There was no statistical difference in leakage for all groups in Zone 1. For Zones 2 and 3, the groups utilizing glass-ionomer liner on the cavosurface margin had significantly less microleakage (P>0.05). Although the compomer/hybrid combination had low leakage values on average, the wide range of values led to unpredictable results. The flowable/hybrid combination and the packable composite performed less favorably.

This study demonstrated the difficulty in sealing a proximal dentin margin. However, the glass-ionomer/hybrid restorative techniques is the most likely to give successful clinical results.