The antimicrobial effect of calcium hydroxide in root canals pretreated with 5% iodine potassium iodide

Calcium hydroxide (CH) is often used as a routine interappointment dressing during the endodontic treatment of teeth with apical periodontitis. Howeve r, it fails to consistently produce sterile root canals. The present study was set up to find out whether an antimicrobial strategy including the use of CH could be made more effective if: 1) canals were pretreated with 5% io dine potassium iodide (IPI), and 2) the dressing period was extended up to 2 months. Fifty human teeth, with radiographically verified apical periodon titis, were microbiologically sampled. After chemomechanical preparation th e canals were pretreated with IPI for 3-7 days. Teeth where microorganisms persisted were then treated with CH for 2 months. Following instrumentation and dressing with IPI, 43 bacterial strains were recovered in 22 of the te eth. Samples obtained after the CH dressing period disclosed growth of 13 f acultative and two strict anaerobic strains in 10 teeth. Enterococcus faeca lis was identified in two specimens. In conclusion, the present study gave no evidence for an increased antimicrobial effect of CH if it was left for longer periods in the root canal. Although pretreatment with IPI from a qua ntitative point of view did not seem to add antimicrobial power, it might r educe the frequency of persisting strains of E. faecalis.