A massive Cochrane systematic review tells us a lot about Class II treatment.
We have updated our Cochrane review on Class II treatment. The results are interesting and clinically relevant.
When you sign up to do a Cochrane review you have to agree to keep it up to date. This post is about the updated review that was published this week. I will declare an interest. I am a co-author on this paper and it included data from trials that I was involved with.
Cochrane Database of Systematic Reviews 2018, Issue 3. Art. No.: CD003452. DOI: 10.1002/14651858.CD003452.
Batista KBSL, Thiruvenkatachari B, Harrison JE, O’Brien KD.
A team from Manchester, North of England, did this study. The lead author is Klaus Barretto-Lopes, who worked with us for a year and has returned to Brazil. He does the excellent Portuguese translation of my blog.
We tried to answer three main questions;
1 What are the effects of treatment provided in 1 or 2 phases (early v adolescent)?
2 What are the effect of later treatment with functional appliances vs untreated controls?
3 Are there any difference in the effects of the various types of functional appliance?
What did we do?
We followed standard Cochrane methodology and only included randomised trials in the review. The PICO was
Participants: Children receiving orthodontic treatment to correct prominent upper incisors
Intervention: Any type of functional appliance
Control: Delayed or no treatment or other functional appliance
Outcome: Primary outcome was overjet. Secondary was skeletal relationship, harms, self esteem.
We carried out standard electronic and relevant hand searches. We evaluated the trials for bias using the Cochrane Risk of Bias tool.
What did we find?
After applying all the usual filters, we selected a final sample of 27 trials that provided data on 1251 participants. These were broadly divided into;
- Four trials looking at early treatment for children aged 7-11 years old.
- Twenty evaluating treatment of children aged 10-15 years old
- The remaining seven treated children between 9-13 years old.
We divided the studies into two main groups;
- Those that looked at early treatment (2 phase) and followed the participants until all treatment was completed when they were older.
- Studies of later (adolescent) treatment. (1 phase).
We found that most of the studies were rated as high or unclear risk of bias. This was mostly for issues with blinding, concealment and randomisation. The other main reason was for attrition bias because of “drop outs”. I shall return to this later.
These are our main findings;
When treatment was provided early the only effect of treatment was a 12% reduction in the incidence of incisal trauma. At the end of all treatment 19% of the early treatment group had experienced trauma. Whereas, 31% of those that did not have early treatment had trauma.
There were no effects of early treatment on final occlusion, self esteem and skeletal pattern.
It was clear that the functional appliances reduced the overjets of the patients. Interestingly, removable functional appliances statistically reduced the ANB by 2.37 degrees (95% CI 1.7-2.37). The use of fixed functional appliances did not have a significant effect.
There were minor differences between the Twin Block and other functional appliances.
What did I think?
Because I am conflicted, I cannot comment on the quality of this review. However, it is a Cochrane review and Cochrane operate to a high standard.
When I think about the findings. There are several important points that we should consider. Firstly, the risk of bias tool resulted in the identification of several main problems. This meant that the strength of evidence for the main findings ranged from low to moderate. This is not unusual for a Cochrane review.
I feel that it is important to point out that there was a strong effect of attrition bias. Unfortunately, this is a characteristic of most orthodontic studies because of the length of our courses of treatment and difficulty with long term patient recall. Nevertheless, the problem is there and we need to interpret the findings accordingly.
Perhaps the most important data we found is concerned with the reduction in trauma from early treatment. The strength of evidence was moderate. As usual, with findings of a percentage reduction, we need to remember that even when early treatment was done 19% of the children suffered some sort of incisal trauma. Nevertheless, these are interesting findings.
The adolescent treatment data was also clinically relevant. It is important to look at the effect sizes that we found. For example, removable functional appliance reduced the ANB by 2.4 degrees (low strength of evidence). It is up to you to decide if this is clinically signficant.
My feeling is that we can conclude that functional appliances are effective at reducing overjets and most of this reduction is a result of tooth movement. There is some skeletal change but this is small. We do not grow mandibles with our appliances.
This was a large and complex review that looked at a lot of data and patients. I think that the main conclusions are;
- Early treatment results in a reduction in incisal trauma, but it does not eliminate trauma
- There is an absence of evidence on any other benefits of early treatment
- Adolescent treatment with functional appliances reduces overjets. There are minimal differences between appliances. We do not grow mandibles.
Emeritus Professor of Orthodontics, University of Manchester, UK.