Sir, I write having read Dr Mew's letter (BDJ 2006; 200: 360) titled Courage for debate in response to the series of letters in turn responding to his original opinion article Science versus empiricism (BDJ 2005; 199: 495–497).

Dr Mew writes that these responses 'tended to be personal rather than scientific'. I have no intention in becoming embroiled in arguing against the majority of the vitriolic statements within Dr Mew's most recent letter, most being irrelevant to his original thesis Science versus empiricism. Similarly, I have no wish to become involved in a 'plaster on the table' competition. It would be more appropriate if Dr Mew published his research in one of the peer-reviewed dental or orthodontic journals. The dental profession could then analyse his results along with the other research on growth guidance.

Dr Mew mentions specifically in reply to my own letter that 'negative evidence is dangerous'. Indeed this can be true such as the 'negative evidence' of the existence of weapons of mass destruction (WMDs) in Iraq in advance of the recent conflict.

However, Dr Mew will appreciate that orthodontic evidence is actually scrutinised before publication in peer-reviewed journals by independent reviewers. That the four recent randomised controlled trials involving a total of 598 subjects have failed to confirm that growth modification appliances can guarantee an enhancement of skeletal growth in terms of either magnitude or direction1,2,3,4 is proof enough for the majority of the dental profession. It is just unfortunate that some clinicians continue to ignore the scientific evidence that so clearly indicates that functional appliances cannot enhance the magnitude or alter the direction of skeletal growth.

If Dr Mew has good quality growth guidance evidence to the contrary, then it should be published to add to the debate.