The effect of additional enamel etching and a flowable composite to the interfacial integrity of Class II adhesive composite restorations

This in vitro study evaluated the interfacial integrity of Class II resin c omposite restorations. The influence of a flowable composite and additional enamel etching was also evaluated. Deep, saucer-shaped Class LI cavities w ere prepared in the mesial and distal proximal surfaces of 25 extracted hum an molars and assigned to five treatment groups. The gingival margins were extended to approximately 1 mm above the CEJ in 40 cavities and below the C EJ in 10 cavities. The prepared cavities were then restored with a self-etc hing primer system (Clearfil Liner Bond LT) and a hybrid resin composite (C learfil AP-X), with and without a flowable composite (Protect Liner Fl and additional enamel etching with 37% phosphoric acid gel (K-etchant). After f inishing, polishing and thermocycling (4 and 60 degreesC, x300), the sample s were longitudinally sectioned through the restorations and resin-tooth in terfaces were observed directly under a laser scanning microscope. Statisti cal analysis indicated that the use of a flowable composite produced signif icantly more (p=0.04) gap-free resin-dentin interfaces than teeth restored without the flowable composite. However, both flowable composite and enamel etching could not prevent gap formation at enamel-resin interfaces and cra ck formation on enamel walls.