I am writing this blog post in Edinburgh, where the British Orthodontic Conference is about to start. This is an important place for the UK at the moment, as the Scottish people are about to vote on their independence.
I was also born here, so I am Scottish, but I cannot vote because I live in Manchester, North of England. The result of the vote will be of crucial importance to the UK and is due to be announced on Friday morning, which is when I am speaking at the Conference. I hope that this does not coincide with my presentation.
Several posts ago I mentioned that there has been a “burst” of systematic reviews being published. I have already discussed those on this post and this one. This is the final installment of the orthodontic clinical reviews.
Agostini P et al
Cochrane Database of Systematic Reviews 2014: 8
This is an update of a Cochrane review. Importantly, the conclusions have changed with the addition of new information. This review is carried out to a high standard and if you want information on how to read a review, see this post here.
What did they do?
The authors aimed to evaluate the effects of different orthodontic treatments for correcting posterior crossbites. I felt that this was an important question.
They identified 15 studies that could be divided into
9 Comparing types of fixed appliances
2 Fixed vs removable comparisons
4 Others they could not classify, for example, grinding of primary canines.
The primary outcome was the correction of crossbite. This is very relevant because some studies have measured mm of expansion, and this is not particularly relevant as the aim of treatment is to correct the crossbite.
The risk of bias table was interesting and I have included this here. I have interpreted it as showing that there is moderate to high risk of bias in the studies that they have included.
What did they find?
When I looked at the comparisons, most were between variants of fixed appliance and I not sure that this is of much interest to me. Instead, I concentrated on the comparisons between fixed and removable appliances and rapid vs slow expansion.
They concluded that there was low quality evidence that crossbite correction was more successful when using a fixed appliance when compared to a removable appliance. The risk ratio was 1.2 (95% CI 1.04 to 1.37). The stated that this means that the true effect estimate lies somewhere between a 4% and 37% better correction rate for quad helix appliances. This represents a high degree of uncertainty. For a discussion on risk ratio etc, read this blog post.
They could not really draw any conclusions from the papers on slow vs rapid expansion.
What did I think?
I was rather disappointed that the results of 15 papers did not really contribute to our knowledge. So, I looked more closely at their reasons for their assessment of the papers. It became clear to me that low sample sizes and issues with blinding and allocation concealment characterized the studies. This resulted in high levels of uncertainty about the findings. (for more on uncertainty see this post).
What can we conclude?
Firstly more research is needed. In short the studies need to be adequately powered and carried out to contemporary standard. This should be possible because posterior crossbites are a common condition and there should be no shortage of patients in potential trials.
Nevertheless, this review does provide some limited evidence on whether we should use fixed or removable expanders and this is useful, even though there is a high degree of uncertainty. This also reinforces my current practice, as I do not use removable expansion devices. Which is nice to know…
I am now off to the Conference. I am presenting using Prezi software and interactive questions with the audience using Smart phones. It could go very well or be a complete disaster, either way will be memorable. I will report back…
Emeritus Professor of Orthodontics, University of Manchester, UK.