The Efficacy of Two Different Composite Liners in Preventing Microleakage in Deep Class Ii Glass-Ceramic Microhybrite Composite Restoration ; (In Vitro Study)

Abstract

Background
 Potential liner materials include resin modified glass ionomer (RMGI) and flowable liners have been suggested by some studies to inhibit the occlusal and gingival microleakage in Class II composite restorations, which may act as a flexible intermediate layer, relieving the stresses of polymerization shrinkage and subsequently decreasing the microleakage.
 Objectives
 The purpose of this study is to determine the microleakage prevention effect of two different liners (Resin- modified glass ionomer and Flowable composite liner) on the occlusal and gingival cavosurface margin of deep class II cavity restorations using glass-ceramic microhybrid composite.
 Materials and Methods
 Class II cavities were made on both mesial and distal proximal sides of twenty three extracted permanent molars (n= 45 cavities); the gingival margins were placed (1 mm) apical to the cemento enamel junction, and they were randomly assigned to three groups (n=15 cavities). All the cavities were filled with microhybrid resin composite using centripetal placement technique. In group A, no liner was used under the composite, in group B, RMGI liner was used and in group C, flowable liner was used. The specimens were kept in distilled water for 1 week and then they were thermocycled. In order to evaluate the marginal microleakage, the teeth surfaces were isolated with nail varnish then immersed in a 2% methylene blue dye for 24 hours. The specimens were then carefully sectioned mesially/distally at the center and were studied under a stereomicroscope. Then scoring was done.
 Results
 The results of this study show that in all of the groups the microleakage at the gingival margin was more than at the occlusal margin; in group A (p < 0.01), and in group B and C (p > 0.05). At the occlusal margin, group A showed higher microleakage than group B (p < 0.01), and group C (p > 0.05). At the gingival margin, group A also showed higher microleakage than group B and C (p < 0.01). At the occlusal and gingival margins, group B showed less microleakage than group C (p > 0.05).
 Conclusion
 The microleakage at the gingival margin was higher than at the occlusal margin in deep class II microhybrid resin composite restorations. More microleakage was seen in the group in which no liner was used. Therefore, it is imperative to use liner under microhybrid composite in deep class II cavity restorations. Resin Modified glass ionomer liner has the ability to reduce occlusal and gingival microleakage more than flowable liner but statistically the difference was not significant. None of the tested liners were able to prevent occlusal and gingival microleakage completely.