Fixed functional appliances do not make mandibles grow: Another massive systematic review of cephalometric data
Fixed functional appliances do not make mandibles grow: Another massive systematic review of cephalometric data..
A few weeks ago I posted on a systematic review of Class II treatment and concluded that functional appliances do not have a clinically significant effect on skeletal pattern. This new post is on another systematic review which investigated the treatment effect of fixed functional appliances.
Treatment effects of fixed functional appliances in patients with Class II malocclusion: a systematic review and meta-analysis.
European Journal of Orthodontics, (May 2015), 1–14. doi:10.1093/ejo/cjv034
Zymperdikas, V. F., Koretsi, V., Papageorgiou, S. N., & Papadopoulos, M. A.
What did they do?
This was a standard systematic review based on Cochrane collaboration methodology. It is worth pointing out that this was not a Cochrane review. The authors use the following eligibility criteria to include/exclude publications
|Difference between treatment and control||95% CI|
They carried out all the usual steps of a high quality systematic review. After the literature research, they identified nine studies for inclusion. They evaluated risk of bias with the Cochrane Tool for risk of bias and the GRADE approach. They summarise the data and carried out a meta-analysis of many cephalometric variables. They had intended to analyse other outcomes that were more important to patients, but they could not find any.
What did they find?
They reported in detail on 24 cephalometric variables. I am not going to outline all of these (thank goodness I hear you cry!). But I have selected a few that I think are important and included them in this table.
If we look closely at this data it is clear that the skeletal change (ANB) is small and probably not clinically important. However, the dento-alveolar changes are much greater.
When I looked at the 95% confidence intervals for skeletal change (ANB) I found that this could be as little as -0.98° or as great as -2.5°. This represents some uncertainty and small treatment effects.
What did I think?
I felt that this review provided information that reinforced other reviews. They came to the same conclusion; functional appliances do not influence the skeletal pattern to a meaningful degree. It appears that they correct the overjet by tipping the lower incisors forwards and retrocline the upper incisors.
I think it is also relevant to point out that five of the nine studies involved a comparison with a historical control group. As a result, we need to interpret this data with a degree of caution because the selection of historical control groups may introduce bias. I have discussed this before.
I cannot help thinking that the question of whether functional appliances influence skeletal growth has been answered. They don’t have a clinically significant effect.
Finally, I also wonder if it is time that we stopped investigating the effect of functional appliances on cephalometric variables. We need to evaluate other far more relevant outcomes, for example, patient perceptions of the appliances and maybe breathing etc? to this end I have decided not to do another post on a cephalometric study.
Time to move on… There is nothing to see here
Emeritus Professor of Orthodontics, University of Manchester, UK.