Inhibition of pure cultures of oral bacteria by root canal filling materials

This study compared the antimicrobial effectiveness of nine dental materials and a negative control agent against 21 strains or species of bacteria using an agar diffusion assay. The materials were: 1. Camphorated parachlorophenol mixed with calcium hydroxide (CPC + Ca(OH)2). 2. CPC mixed with zinc oxide (CPC + ZnO). 3. Formocresol mixed with zinc oxide and eugenol (FC + ZOE). 4. Chlorhexidine mixed with ZOE (CHX + ZOE). 5. Kri paste. 6. ZOE. 7. Zinc oxide mixed with sterile water (ZnO + H2O). 8. Calcium hydroxide mixed with sterile water (Ca(OH)2 + H2O). 9. Vitapex. 10. Vaseline (control). The test bacteria represented species commonly isolated from nonvital primary and permanent tooth root canals. The antimicrobial effectiveness of the materials was divided into five groups based on the diameters of the zones of inhibition against all test bacteria and distribution of the data. All materials except Vaseline showed antimicrobial activity against some of the 21 organisms. Generally, all materials inhibited gram-negative anaerobic bacteria more effectively than aerotolerant gram-negative or gram-positive bacteria. Materials containing CPC or FC (except Kri paste) produced strong or medium strong inhibition against most bacteria. CHX + ZOE, Kri paste, ZnO + H2O, and ZOE inhibited all or most bacteria, but to lesser extent than CPC + Ca(OH)2, CPC + ZnO, or FC + ZOE. Ca(OH)2 + H2O, Vitapex, and Vaseline generally were nonihibitory. The findings should allow a comparative evaluation of antimicrobial effectiveness to be made of materials commonly used in pulpectomy procedures with primary teeth.