Abstract: One small trial at high risk of bias met the inclusion criteria. The trial randomised 49 participants, most of whom had cancer. It compared standard care (defined as surgery, antibiotics and oral rinses at the discretion of the oral-maxillofacial surgeon) to standard care plus hyperbaric oxygen therapy (2 atmospheres twice a day for 40 treatments). The trial measured the percentage of participants who improved or healed at three, six, 12 and 18 months and last contact. It also measured mean weekly pain scores. At three months, the study found that the participants in intervention group were more likely to have an improvement in their osteonecrosis than the standard care group participants (risk ratio (RR) 1.94, 95% confidence interval (CI) 1.01 to 3.74). There was no clear difference between the groups for the outcome 'healed' at three months (RR 3.60, 95% CI 0.87 to 14.82). There was no clear difference between the groups for improvement or healing when they were evaluated at six, 12 and 18 months and last contact. The study did not give any information on adverse events. Although the findings suggest adjunctive hyperbaric oxygen improved BRONJ, the quality of the evidence is very low since the only study was underpowered and was at high risk of bias due to lack of blinding, cross-over of participants between groups and very high attrition (50% at 12 months and 80% at 18 months in this study, which was designed for an intended follow-up of 24 months). There is a lack of evidence from randomised controlled trials to guide treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ). One small trial at high risk of bias evaluated hyperbaric oxygen therapy (HBO) as an adjunct to "standard" care and could not confirm or refute the effectiveness of HBO. There are two ongoing trials of teriparatide treatment for BRONJ. We found no randomised controlled trials of any other BRONJ treatments. High quality randomised controlled trials are needed. We provide recommendations for their focus and design.

Plain-language summary: Review authors, working with the Cochrane Oral Health Group, carried out a thorough search up to 15 December 2015 for studies that randomly allocated participants to different treatments for BRONJ (or to a 'placebo' condition that has no active treatment). This type of study design is known as a 'randomised controlled trial'. We only found one relevant completed study and two ongoing studies. The completed study compared people with BRONJ being treated with surgery, antibiotics and mouth rinses to people receiving the same 'standard care' with an add-on treatment called hyperbaric oxygen therapy, which is thought to increase bone renewal. There were 49 participants, most of whom had cancer. The study found that the participants in intervention group were more likely than the standard care group participants to have an improvement in their osteonecrosis at three months, but there was no clear difference between the groups when they were evaluated at six, 12 and 18 months and last contact. There was no clear difference between the groups at any time point for complete healing. These results are not reliable as the quality of the evidence is very low. The study did not assess whether there were any side effects of the treatment. The study had several important flaws: for example, there was a very small number of participants, some participants changed groups during the study and there was a loss of participants during the study. There is insufficient evidence to conclude whether hyperbaric oxygen therapy is a useful add-on to standard care in the treatment of BRONJ. There are two ongoing trials of teriparatide, a hormonal treatment for BRONJ. We found no randomised controlled trials of any other treatments for BRONJ. As there is a lack of good quality scientific evidence to decide how best to treat BRONJ, high quality trials are needed.