the effect of a glass ceramic insert in sandwich technique on microleakage in class ii composite resin restorations

introduction: the aim of the present study was to evaluate the effect of glass ceramic insert in the sandwich technique to reduce microleakage in class ii composite resin restorations. methods: sixty sound human upper second premolars were selected and randomly divided into six groups (n=10). class ii box-only cavities were prepared in distal aspects of each tooth with gingival margin located approximately 0.5 mm below the cej. group a (control) was restored incrementally with tetric ceram and a total-etch bonding technique. group b and c were restored with sandwich technique using a compomer (compoglass f) or flowable composite resin (tetric flow) as the lining material at gingival floor, respectively. group d, e and f were represented in the same way as group a, b and c and a glass ceramic insert was added to the composite bulk. the specimens were thermo-mechanically cycled, and then immersed in 0.5 % basic fuschin for 24 hours. dye penetration was detected using a sectioning technique. results: no significant difference was found between total-etch bonding and sandwich techniques. the placement of an insert caused an increase in   microleakage in all groups significantly (p < 0.05). group d (no liner/ with glass insert) showed the highest amount of microleakage and group a (no liner/ without glass insert) resulted in the lowest amount of total microleakage. conclusion: placement of glass ceramic insert could not decrease gingival leakage. according to the limitation of this study a composite resin restorations with incremental technique is recommended