Using skeletal anchorage for expansion is not necessary in pre-adolescents! A five year follow up of a trial.
Expansion appears to be all the rage at the moment. There are claims and counterclaims for its effects and benefits. Indeed, the discussion is getting very heated. Strangely, most of the claims are based on selective quoting of convenience studies with low levels of evidence. I have discussed expansion many times on this blog, and it has been challenging to come to solid conclusions. We also have to consider the type of expansion we should use with respect to skeletal anchorage. This was summarised nicely by Martyn Cobourne in a recent post on this blog. He concluded
“Bone-borne expansion seems to be the future. First, however, there is a need for some high-quality clinical trials to investigate further and refine these appliances”.
This new study sheds some light on this subject. It was also unique as the authors report data five years following expansion.
A multinational team from Sweden, Germany and Russia did this study. The European Journal of Orthodontics published the paper.
Bazargani et al. EJO: Advanced access. DOI: https://doi.org/10.1093/ejo/cjad024
What did they ask?
They did the study to:
“Three dimensionally assess and compare the influence of the conventional Tooth Borne-RME and Tooth-Bone-Borne RME (skeletal anchorage) on the skeletal structure of growing children”.
What did they do?
The team did a single centre two-arm parallel-sided RCT. This study started enrolment in September 2010 and closed in December 2015. The PICO was:
Patients aged 8-13 with unilateral or bilateral crossbites with constricted maxilla. Their dental age was in the early or late mixed dentition.
Tooth borne RME (TB).
Tooth-bone- borne (TBB) RME with skeletal anchorage
Primary outcome: Mid-palatal suture expansion. The secondary outcomes were skeletal expansion at the nasal base. The marginal bone level at the buccal aspect of the first molars and any skeletal differences between boys and girls.
The team collected data at the start of the study, at the end of the expansion, one-year post-expansion and five years post-expansion.
The primary data sources were CBCT examinations at all the data collection stages. They derived most of the measurements from the scans. Their statistics were relevant.
Importantly, the authors used a pre-determined randomisation that remotely allocated the interventions. Notably, the allocation was done after the patients entered the study. A research assistant revealed the allocation to the operators, ensuring good concealment. They analysed the data blindly and did a nice sample size calculation based on the differences in palatal expansion between the two techniques.
What did they find?
They enrolled 52 participants in the study and they all completed treatment. One participant in each group missed their CBCT appointment at the end of the expansion. They analysed data on all the participants after five years.
Similarly to most orthodontic studies, the authors presented a ton of data. I have decided to concentrate on the primary outcome of palatal suture expansion and nasal width.
In short, they showed that at the end of expansion (T1), the mid-palatal width difference was 0.6mm (CI 0.2-1.1) greater in the TBB group. However, this was not evident at the last data collection points.
When they looked at nasal width at T1, it was 0.7mm (CI 0.1-1.4) greater in the TBB group. At T2, it was 1.6mm (CI 1.0 -2.3); at T3, it was 2.1mm (CI 1.4 -2.8).
All other outcomes showed either no significant differences or were clinically insignificant.
The authors concluded:
“Skeletal expansion in the mid palatal suture was higher in the TBB group. However, this may not be clinically significant”.
“Skeletal expansion at the level of the nasal cavity was higher in the TBB group”.
“The use of miniscrews and skeletal anchorage in young preadolescents cannot be recommended due to the similar outcomes as the less invasive conventional TB-RME”.
What did I think?
This was an excellent study that used high-level methods. I was also impressed that the study team successfully followed up participants for five years. In many ways, this makes this study unique. Their methodology was sound, and the paper was very clear.
When I started to read the paper, I was concerned about the repeat CBCTs. I have been critical of other retrospective studies using multiple CBCTs. However, in this study, the team got ethical committee approval for the CBCTs, and this deals with ethical issues, as the patients would have been fully informed.
The authors drew attention to a systematic review that showed mini-screw assisted RME produces more significant expansion than tooth-borne expansion in late adolescents. This led them to conclude that there is no need for mini-screw expansion in the mixed dentition. Effective treatment can be done with a tooth-borne RME.
Interestingly, it flies in the face of most of the stuff currently peddled by the airway/expansion groups. It would be great if they read and understood this study.
Emeritus Professor of Orthodontics, University of Manchester, UK.