The purpose of this in vitro study was to evaluate marginal integrity and wall adaptation in 1- and 2-mm-deep cavities restored with a high filler-loaded flowable composite in comparison to a flowable composite with lower filler content and a conventional hybrid composite. 1-mm-deep dentin and 2-mm-deep enamel-dentin Class I cavities were prepared and restored with a self-etch adhesive and with one of the composites. Samples were crosscut and evaluated for marginal integrity and gap formation using a digital microscope. Selected samples were also observed using a scanning electron microscope. For 1-mm-deep cavities, no differences in marginal integrity and wall adaptation were observed among the three composites. For 2-mm-deep cavities, those restored with the bulk technique and with the higher filler-loaded flowable composite demonstrated a similar outcome as that of the conventional hybrid composite. On the effect of restorative techniques, cohesive enamel defects were observed in bulk-filled 2-mm-deep cavities. However, when the incremental technique was used in conjunction with the higher filler-loaded flowable composite and the conventional hybrid composite for 2-mm-deep cavities, superior results were obtained.
