Data sources: Searches for relevant studies were made using the Cochrane Oral Health Group's Trials Register, CENTRAL, Medline and Embase. The major oral medicine journals were also searched by hand and reference lists of included studies and reviews were checked. Endodontics experts were contacted by e-mail. No language limitations were imposed.
Study selection: Randomised controlled trials (RCT) and quasi-RCT of root canal treatment were included. Surgical endodontic treatment was excluded. The outcomes considered were the number of teeth extracted for endodontic problems; radiological success (absence of any periapical radiolucency) after at least 1 year; postoperative pain; painkiller use; swelling; or sinus track formation.
Data extraction and synthesis: Data were collected using a specific extraction form. The validity of the studies included was assessed on the basis of allocation concealment, blindness of the study, and loss of participants. Data were analysed by calculating risk ratios. When valid and relevant data were collected, a meta-analysis of the data was undertaken.
Results: Twelve RCT were included in the review. Four studies had a low risk of bias, four a moderate risk, and another four had a high risk of bias. The frequency of radiological success and immediate postoperative pain were not significantly different between single- and multiple-visit root canal treatments. People who had single-visit treatment reported a higher frequency of painkiller use and swelling, but the results for swelling were not significantly different between the two groups. We found no study that included tooth loss and sinus track formation among its primary outcomes.
Conclusions: No difference exists in the effectiveness of root canal treatment, in terms of radiological success, between single- and multiple-visit treatments. Most short- and long-term complications are also similar in terms of frequency, although patients undergoing a single visit may experience a slightly higher frequency of swelling and are significantly more likely to take painkillers.