Sir, it is of great interest to read the full results of the national new patient registration of avascular necrosis of the jaws published by the Faculty of General Dental Practitioners (UK) highlighted in a recent BDJ (2012; 213: 594).

The study summarises the results of the two-year National Survey of avascular necrosis of the jaw referred to secondary care units and is the first report to try to obtain a picture of avascular necrosis and bisphosphonte-related osteonecrosis of the jaw (BRONJ) in the UK. Whilst the merits of this ambitious study are without question, I believe that it is important that practitioners read the report in full and accept the figure of 620 new cases reported in the UK annually as at best a 'rough calculation'.

There is clearly a danger in extrapolating a voluntary registration survey to determine an accurate national disease incidence in the UK. This quoted figure is based on extrapolation of the figures from Merseyside and Northern Ireland to the UK as a whole and numerous population assumptions. Indeed, the authors of the report openly highlight the limitations of the study particularly regarding regional under-reporting as well as practical difficulties in online registration. In addition the 'non-exposed' presentation of BRONJ recently described in the literature would not be included in these figures and perhaps reflects our lack of understanding regarding the full spectrum of clinical presentations of this condition.1

Nevertheless, the study does highlight some interesting data regarding BRONJ and in particular the fact that the majority of cases were associated with females taking oral bisphosphonates rather than the more potent higher dose intravenous form of the medication. Perhaps this is a reflection of UK prescribing patterns and the high numbers of post-menopausal women taking oral bisphosphonates rather than the risk due to route of administration or dose potency. It is also interesting that half of the patients were also taking corticosteroids and raises the question whether bisphosphonates are the only drug to increase risk of osteonecrosis. This is also in light of osteonecrosis reports in patients taking other anti-resorptive drugs such as the RANKL inhibitor, Denosumab.2

Ten years on since the initial description of BRONJ there continues to be much debate as to its disease mechanism and we are only beginning to get a picture of the disease in the UK. Whilst BRONJ appears to be a rare complication of bisphosphonates it is important that we continue to carefully manage our patients taking all forms of bisphosphonates. This report should not be interpreted as a cue to belittle this condition which although apparently rare can have a significant effect on the quality of life of affected patients.