The diagnostic accuracy of microbiologic root canal sampling and the influence of antimicrobial dressings

The routine approach to endodontic treatment of teeth with apical periodont itis often involves an interappointment dressing with calcium hydroxide. Ho wever, investigations have demonstrated a negative influence of calcium hyd roxide on the accuracy of microbiological root canal sampling (MRS). The ai m of the present study was to investigate whet-her the use of a fluid dress ing lit 5% iodine potassium iodide (IPI) would increase the accuracy of MRS . Following instrumentation of 50 teeth with radiographically verified apic al periodontitis the root canals received IPI as an intracanal dressing. On e week after closure canals were sampled, "test sample" (TS), and then left filled with sampling fluid and temporarily sealed. Seven days later a "gol d standard" (GS) sample was obtained. Bacteria were recovered in 22 teeth ( 44%) in TS as well as in GS. Fifteen teeth (30%) were positive for growth i n both samples. Using the detection level "very sparse growth" of microbes the sensitivity and specificity of MRS reached 68% and 75%, respectively; I n an earlier study, following the same experimental protocol, but with calc ium hydroxide as intracanal dressing, the corresponding values were 33% and 81%, In 25% of these cases bacteria persisted in the canals. As compared t o calcium hydroxide, the use of IPI resulted in improved test accuracy, bur loss of antibacterial capacity. Conclusively, intracanal dressings seem to vary in their influence on the microbiologic test performance as well as i n their antibacterial efficacy. In a clinical situation the choice of inter appointment dressing should include consideration of these potentially conf licting properties.