Objectives: The purpose of the study was to evaluate the antimicrobial properties of four provisional cements from three different groups with the addition of Chlorhexidine diacetate (CHDA). Methods: The Direct Contact Test (DCT) and the Agar Diffusion Test (ADT) were used to evaluate the antimicrobial properties of: TempBond (KERR, Michigan, USA), TempBond NE (KERR, Michigan, USA) and FreeGenuol (GC, Tokyo, Japan). The cements were mixed with Chlorhexidine diacetate (7.7% by weight). The materials were tested in contact with Streptococcus mutans. In the DCT, Samples of each material were placed on sidewalls of eight wells in a 96 micro titer plate. After setting, freshly grown cells (1X106) were placed on the surface of each sample for 45min at 370C. Fresh medium was then added to each well and microbial growth was followed for 24hrs in a temperature-controlled spectrophotometer. The provisional cements mixed with CHDA were examined immediately after setting, and after aging periods of 1, 2, 3, 14 days and 3 months. The ADT was preformed by measuring the Halo created around samples of provisional cements that were put in uniform wells punched in agar plates then covered with microorganism suspension and incubated for 24 hours. 1-way ANOVA was preformed. Results: All of the materials demonstrated bacterial inhibition even after 3 month of aging at the DCT tests. All of the provisional cements + CHDA presented the same antibacterial properties at all aging times. Conclusions: Chlorhexidine diacetate added to three provisional cements produced bacterial inhibition that lasted at least three month.