Objective: To test the bacterial sealing ability of commonly used provisional endodontic restorative materials. Method and Materials: This study investigated Cavit (3M ESPE), Ketac (3M ESPE), DuoTemp (Coltène/Whaledent), and a combination technique using Ketac and Cavit. One hundred molars were randomly selected and then mounted in an apparatus that isolated the crown portion of the tooth. Provisional restorative materials were placed in an open access following manufacturer guidelines. Streptococcus mutans was applied to the samples, and results were tabulated over the course of 4 weeks. Results: Cavit and DuoTemp performed the best, and Ketac performed the worst. After 14 days, however, all materials leaked in over half of the samples. Conclusion: No material can be recommended as superior in providing a reliable seal after 14 days. Keywords: bacteria, leakage, provisional, provisional restorations