Objective: Biofilm accumulation on provisional restorations may affect the surrounding tissues' integrity. The purpose of this study was to test in vivo biofilm formation on polymethyl methacrylate (PMMA) self-cured acrylic resin provisional crowns. Method and Materials: Three types of PMMA surfaces were tested: (1) polished, (2) polished and coated with bonding agent, and (3) polished and coated with light-cured liquid polish. After 12 hours in the oral cavity, the crown was removed and examined by confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM). Results: Biofilm, 250 µm thick, was observed with CLSM on the polished acrylic surface. Significantly less bacterial accumulation was observed on the crowns coated with bonding agent, whereas no biofilm was observed on the crowns coated with liquid polish (P .001). SEM examination confirmed these findings. Conclusions: Bonding resin or liquid polish coatings significantly reduce early biofilm formation, which in turn might affect the overall plaque accumulation on provisional restorations. Schlagwörter: biofilm adhesion, bonding resin, liquid polish, polymethyl methacrylate, provisional crown