Sir, I was sad to see that the letters criticising my opinion article, Science versus empiricism (BDJ 2005 199: 495–497) tended to be personal rather that scientific.

Empiricism essentially means experiment, and if one thing does not work, try something else (trial and error) but it is valueless without scientific logic. It is empiricism which has led the specialty around the houses on the extraction issue. Angle tried without and it did not work so Tweed tried with it and that failed too. Now no one knows. My critics would do better if they analysed people with naturally straight teeth and used scientific logic to work out why, but they do not do this.

Dr Horobin agrees with me that our modern lifestyle is the obvious cause of malocclusion, but Dr Di Biase believes that 'the aetiology of malocclusion is poorly understood'. Is it ethical to treat a disease that you do not understand? Twenty-five years ago I first put forward an explanation for the aetiology of malocclusion1 and again in 2004;2 no one has ever challenged it scientifically and I know of no rational alternative. It is just ignored as it does not slot in with mechanical/surgical thinking.

Dr McIntyre quotes 1,915 articles which failed to show that functional appliances had a significant effect on mandibular growth, a finding that may be true, but negative evidence is dangerous. I have not seen one article that shows that growth guidance appliances do not produce a change, or for that matter that orthodontic treatment has any long-term benefit at all.

Too few orthodontists pay attention to the direction of facial growth or are aware of the overwhelming influence of oral posture. How can one correct a mandible when the maxilla has dropped half an inch? No one who rests their tongue against the palate with their lips sealed will have a malocclusion, despite what Mr Pearson says.

My own research on identical twins has convinced me that a substantial ratio of patients receiving conventional treatment suffer some facial damage and that the teeth of most patients need to be held straight for ever, hardly an optimal result. Orthodontists are poorly placed to refute this as they prefer the flat faces they create,3,4,5 while the general public prefer a forward (horizontally) growing face. I do not say this to annoy people but to encourage reasoned debate.

We have to balance the merits of fixed appliances that we know are 'clinically effective' (in the short-term anyway) against other methods that may be more 'clinically efficacious'. Postural changes are very hard to achieve and inevitably there is a high rate of failure but if we do not try, then extractions and/or orthognathic surgery become inevitable. Some children improve their oral posture spontaneously and this, as Dr McIntyre reminds us, may be the group that grow favourably regardless of treatment. Mr Pearson recommends a double blind clinical trial but how does one assess the changes in oral posture? No one has yet developed a means of measuring tongue posture, so it would prove nothing.

I know of only one way. Select a number of good responses to each treatment and compare them. The most 'effective' method will have a higher ratio of satisfactory results but if one method is more 'efficacious' it is likely to have a higher ratio of excellent results. I would be happy to present 10 of my good cases so that they could be matched against those of any other orthodontist in the UK. Because I have been in practice longer than most, it might be fair to increase this to three other orthodontists. My only condition would be that they are assessed by lay judges. Sadly, many will see this as provocative but I can see no other way to settle this debate.

I have made similar offers in the past, even to pay the cost (substantial) of an independent scientific enquiry to assess the science supporting orthotropics versus orthodontics. I also offered to pay the individual orthodontists for attending to give evidence. It seems that no orthodontist has the courage to show their cases or debate this issue on a purely scientific basis.