Flare-up rate in pulpally necrotic molars in one-visit versus two-visit endodontic treatment.

This retrospective study compared one-visit versus two-visit endodontic treatment. The same technique and materials were used before and after making the sole change to one-visit endodontic treatment in 1991. Treatment records of 402 consecutive patients with pulpally necrotic first and second molars were compared. In 201 patients, treatment was provided by debridement and instrumentation, followed by obturation at a second visit; whereas the second group received single visit therapy. Flare-ups were defined as either patient reports of pain not controlled with over-the-counter medication or as increasing swelling. Sixteen flare-ups (8%) occurred in the two-visit group versus six flare-ups (3%) for the one-visit group. This showed an advantage for one-visit treatment at a 95% confidence level. In a second comparison, one-visit patients who had previously received two-visit treatment for a different pulpally necrotic molar served as their own control. No significant differences were present in this subgroup of 17 patients.