To determine the operative time and the internal restoration gap in the restoration–tooth interface in the cavity floor using an incremental technique for conventional resins and the single-increment technique for the bulk fill resin.In this in vitro experimental study, the internal gaps of the restoration–tooth interfaces in the cavity floors of two conventional resins and two bulk fill resins were microscopically analyzed, and the restoration times of the single-increment technique and the incremental technique were determined.Bulk fill resins had smaller internal gap (63.31 µm) than conventional resins (333.14 µm). Regarding the restoration time, the single-increment technique obtained the best results in operative time (3.52 minutes), with significant differences relative to the incremental technique.The Tetric N-Ceram bulk fill resin presented better performance than conventional resins relative to the internal gap of the restoration–tooth interface in the cavity floor. In addition, the single-increment technique presented a short clinical restoration time.