Background and aims: Composite restorations frequently have gingival margins apical to the cemento-enamel junction (CEJ). Microleakage at the cementodentinal margins is one of the most important causes of failure in these restorations. The current study evaluated microleakage at the occlusal and gingival margins of Class II packable composite restorations using resin-modified glass ionomer and flowable composite as liners, using the two-step etch-and-rinse and self-etch dentin-bonding systems.
Materials and methods: This in vitro study was carried out on 48 intact human premolars. Class II preparations were made with the gingival margins placed 1.0 mm apical to the CEJ. The teeth were randomly assigned to six groups of 16 boxes and restored using the following techniques: Group 1: Single Bond (3M ESPE) + Filtek P60 (3M ESPE); Group 2: Clearfil SE Bond (Kuraray) + Filtek P60; Group 3: Single Bond + Filtek Flow (3M ESPE) + Filtek P60; Group 4: Clearfil SE Bond + Filtek Flow + Filtek P60. Group 5: Single Bond + Fuji II LC (GC) + Filtek P60; Group 6: Clearfil SE Bond + Fuji II LC + Filtek P60. The restorations were thermocycled for 1000 cycles at 5{degree sign}C and 55°C, soaked in 2% methylene blue for 48 hours, then sectioned mesiodistally and viewed under a stereomicroscope for leakage at the gingival margin. The data were statistically analyzed using the Kruskal-Wallis, two-way ANOVA and Mann-Whitney U-tests.
Results: The resin-modified glass-ionomer liner demonstrated significantly less leakage than flowable composite (p<0.05). There was no difference between restorations with flowable resin composite liners and those without the liner; in addition, no significant difference was observed between the two kinds of adhesive systems.
Conclusions: The current study supports the use of resin-modified glass ionomer as a liner in closed-sandwich technique to decrease microleakage of Class II packable composite restorations, applying either the two-step etch-and-rinse or the self-etch dentin adhesive system.