John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. Root canal treatment is a common procedure in dentistry, and requires one or more visits to the dentist. In an updated review in December 2016, the Cochrane authors have brought together the trials that compared different numbers of visits and we asked the lead author, Maddalena Manfredi from the University of Parma in Italy to tell us what they found.

Maddalena: Root canal treatment, which is also called endotontic treatment, is done to remove organic tissue, infected debris, and bacteria from the root canal system of a tooth. There are two main techniques. In the first approach, residual bacteria are eliminated or prevented from repopulating the root canal system by putting a dressing into the root canal which remains there in-between at least two visits to the dentist. The second approach aims to eliminate remaining bacteria or render them harmless by entombing them using a method that we call complete and three-dimensional obturation, which means that the treatment is complete in a single visit.
Our Cochrane Review investigates the relative effects of the two approaches, helping patients and dentists who wish to choose between having the root canal treatment in a single visit or over two or more visits.
We now have 25 randomised trials in the review, and were able to use data from approximately 3570 patients in our analyses, finding that, at present, there is no evidence of a substantial advantage of one approach over the other.
In particular, we found that they were similar for outcomes such as tooth extraction due to endodontic problems, radiological failure, immediate postoperative pain, swelling or flare-up, sinus tract or fistula formation, and complications. There were some differences in terms of pain in the first week and use of painkillers, in favour of multiple visit approach, but these results need to be considered with caution because of the low to moderate quality of the evidence.
In summary, there is no evidence to suggest that a single- or a multiple-visit strategy is better for root canal treatment. Neither can prevent all short- and long-term complications and, on the basis of the available evidence, it seems that the benefits of a single-visit treatment, in terms of time and convenience need to be balanced against a higher frequency of late postoperative pain and need for painkillers.

John: If you would like to look in more detail at the balance of these effects, and see the results for the outcomes that were similar, you can find the full review in the Cochrane Library. Just go online to Cochrane Library dot come and search ‘number of visits for endodontic treatment’.