Growth inhibitory activity of gutta-percha points containing root canal medications on common endodontic bacterial pathogens as determined by an optimized quantitative in vitro assay

Gutta-percha points containing calcium hydroxide, zinc oxide (ZnO), a mixtu re of ZnO and chlorhexidine (ZnO/CHX), iodine-polyvinylpyrrolidone (ZnO/J-P VP), or a mixture of CHX and J-PVP and ZnO (ZnO/CHWJ-PVP) were tested for t heir ability to inhibit growth of pure cultures of bacterial species common ly involved in endodontic infections (Peptostreptococcus micros, Streptococ cus intermedius, Enterococcus faecalis, and Porphyromonas gingivalis). To q uantitate growth inhibition, an in vitro assay was established that control led for important parameters of root canal infection. Approximately 10(7) b acteria per assay were suspended in diluted human serum and cc-incubated wi th the gutta-percha points in an anaerobic atmosphere for up to 2 wk. Aliqu ots used for determination of colony counts were taken on days 0, 1, 2, 4, 7, and 14 of incubation. As judged by colony-forming unit reduction kinetic s and final counts, calcium hydroxide had better growth inhibitory activity than ZnO/CHX, ZnO/J-PVP, and ZnO alone for all bacteria tested except Pept ostreptococcus micros. The combination of CHX and J-PVP with ZnO did not re nder results different from those of ZnO/CHX or ZnO/J-PVP. The results of t his study support the introduction of standardized assays for testing antib acterial properties of root canal medications under conditions that more cl osely resemble those encountered in endodontal infections.