The aim of this study was to assess the efficacy of chlorine dioxide (ClO₂) gas against Porphyromonas gingivalis strain smeared on three different materials for experimental purposes. The experimental materials comprised titanium implant fixtures (TIFs) (Steri-Oss ®threaded implant, 3.8 mm in diameter, 13 mm in length), titanium pellets (TPs) (4 mm in diameter, 1 mm in thickness) and paper disks (PDs) (5.6 mm in diameter, 1.1 mm in thickness). The microorganism used in this study was anaerobic Porphyromonas gingivalis ATCC 33277 strain. P.gingivalis-tainted TIFs (TPs/Pds) were inserted into the test tube to dilute the P.gingivalis broth to 10^-1–10^-9 concentration. TIF (TP/PD) polluted with P.gingivalis was transferred to sterile Petri dishes with the cover removed, and exposed to CIO₂ gas with concentrations of minimum 1 ppm to maximum 6.5 ppm in a door-closed and sealed room (7.4 m³) for 60 minutes each. Then, the TIF (TP/PD) placed in Petri dishes was put into a test tube containing sterilized BHI (Brain Heart Infusion) broth and cultured for 48 hours at 37℃. The degree of antimicrobial effect on P.gingivalis was determined based on macroscopic assessment of the extent to which the broth in the test tubes became turbid.
P.gingivalis on TIFs in the 10^-1to 10^-6 dilution group did not perish completely even when exposed to 6.0–6.5 ppm ClO₂ gas. On the other hand, P.gingivalis on TPs and PDs were destroyed regardless of the dilution group by exposure to concentrations of 5 ppm and 3 ppm CIO₂ and above in the same room, respectively.
The results showed that higher concentrations over 6.5 ppm ClO₂ gas were needed to kill all the P.gingivalis ATCC 33277 cells growing on the implant fixtures than those on the other two materials. Therefore, it is suggested that for materials having a smooth surface and/or a plain form, the open method is effective in order to disinfect tools and implant materials contaminated with P.gingivalis, but is inadequate in latter materials having a complicated form.