Sir, I read with interest the recent thought provoking opinion article by J. Mew (Br Dent J 2005; 189: 495–497). In this article, Dr Mew argues the relative merits of science versus empiricism in both the causes and the treatment of malocclusion.

I disagree with Dr Mew in that optimal orthodontic care is actually delivered by clinicians who combine knowledge (science) and experience (empiricism) in routine clinical practice. This is of particular relevance in the main theme of Dr Mew's article — 'growth guidance'.

A recent MEDLINE search produced 1,915 hits when the search term 'Orthodontic Appliances, Functional' was used. Of these, the randomised controlled trials1,2,3,4,5 (in addition to a multitude of other studies [of variable quality]) have all failed to produce any evidence that 'growth guidance' produces any significant 'extra' anteroposterior mandibular skeletal growth in Class II cases. Similarly, there is no evidence that any orthodontic appliance can convert vertical skeletal growth into horizontal skeletal growth. Nonetheless, all orthodontists have experience of cases where useful skeletal growth coincides with the wear of the 'growth guidance' appliance. However, 31% of the untreated controls in one study also grew favourably.6 There are also many 'growth guidance' cases where the outcome is not successful for a variety of reasons.

These facts do not diminish the value of empiricism in clinical orthodontics, but if we fail to combine the substantial amount scientific evidence with clinical experience, we are misleading both ourselves and our patients. How much more evidence is needed to convince the dental profession that 'growth guidance' appliances do not produce a miraculous change in skeletal growth?