Objective: The objective of this split-mouth randomized controlled study was to compare the 2-year clinical performance of two restorative techniques and materials for posterior permanent carious teeth. Method and Materials: After signing informed consent, 30 patients aged between 7 and 16 received two Class 1 restorations on cavities on permanent first or second molar teeth performed with one of two systems: incrementally placed conventional posterior composite resin (Herculite Ultra, Kerr), and sonic-resin placement system (SonicFill, Kerr) with single-component self-etch adhesive system (Kerr) according to the manufacturers' directions. Two blinded observers evaluated the restorations at three times (baseline, and after 1 and 2 years) according to the US Public Health Service modified criteria. Kruskal-Wallis test and Mann-Whitney U-test were used to compare the clinical performance of the restorative systems. Results: The restorative systems showed similar clinical performance at 2 years. At the end of 2 years in both groups, one restoration's marginal staining Alpha ratings decreased. In the same period, two restorations in the conventional group and one in the SonicFill group received Bravo ratings for color match and surface roughness scorings. Conclusion: The sonic-resin placement system demonstrated similar results to incrementally placed conventional composite resin in terms of clinical success. Considering the advantages of providing up to 5 mm in a single layer, and the adjustability of the viscosity, bulk-fill composite restorations seem to be a good alternative to posterior Class 1 composite restorations. Clinical Relevance: This study suggests that a new dental material for bulk-fill technology exhibits similar clinical success to incrementally placed composite resin. Keywords: adhesive, bulk-fill, composite, dentistry, resin, restorative