Is a 2×4 appliance better than aligners for mixed dentition crowding treatment?
The traditional method of providing alignment of the mixed dentition may be using a 2X4 appliance. Nevertheless, clear aligners may be an excellent alternative treatment that does not involve bonding brackets to the incisors. This new randomized trial examined the effectiveness of aligners or 2×4 appliances.
In the introduction, the authors pointed out that correction of crowded incisors may be carried out in the mixed dentition. This is a controversial area, and the clinician’s drive to provide early interceptive treatment clearly influences the need for early treatment. I understand that this type of care is popular in the USA. However, I am not sure it is carried out in Europe. This means that this paper may be somewhat controversial.
A team from Bauru, Brazil, did this study. The Angle Orthodontist published the paper (this means that it is open access, and anyone can read it).
Vinicius Merino da Silva. Angle Orthodontist, advanced access. DOI: 10.2319/032322-237.1
What did they ask?
They did this study to
“Evaluate and compare the efficacy and efficiency between fixed appliances and clear aligners for resolving maxillary incisor irregularity in the mixed dentition”.
What did they do?
They did a parallel-sided randomized trial with a 1:1 allocation to answer this question. The PICO was
Orthodontic patients who they had treated with RME for posterior crossbites. The participants were between 7 and 11 years old, in the mixed dentition with a maxillary Little’s Index of at least 3mm.
Clear aligner treatment. The aligners were replaced every 15 days, and they asked the patients to wear them for at least 20 hours per day.
Fixed appliance treatment with the 2X4 appliance. They bonded brackets to the upper incisors and tubes to the molars. They used a standardized wire sequence, with the final wire being a 0.20 round ss wire.
The primary outcomes were maxillary incisor irregularity and treatment time. They also selected secondary outcomes, including arch widths, perimeter, plaque index, and caries. The team collected the data six months after RME treatment (T1) and at the end of incisal alignment (T2).
They did a sample size calculation that showed they needed 16 patients in each intervention group.
Finally, they did a simple univariate statistical analysis. The study team used stratified block randomization on irregularity. Allocation was done by a coin toss. They did not provide any information on concealment.
What did they find?
Firstly, they did not find any differences between the intervention groups at the start of treatment. However, I was concerned about marked gender differences between the groups. Chi-squared tests showed this was not statistically significant, but I wonder if this could have occurred because of a lack of power?
When they looked at tooth movement. The mean reduction in the Little’s Index was 5.8 for the aligner group and 5.15 for the fixed appliance group. This was not statistically or clinically significant. The treatment duration was 8.0 (2.9) months for the aligner and 8.6 (2.65) for the FA group. Again, these were not statistically or clinically significantly different.
They did not find any other differences in the outcomes that they measured.
Their overall conclusion was
‘Clear aligners and fixed 2X4 mechanics showed similar efficacy and efficiency for correcting maxillary incisor crowding in the mixed dentition”.
“Both appliances showed similar dental plaque index and white spot lesion incidence during treatment”.
What did I think?
This was an interesting study for those who provide interceptive treatment of maxillary crowding. It is also of interest to those looking to provide aligner treatment to children. Importantly, it shows that aligners are as effective as 2×4 fixed appliances for this treatment. This means that the advantages of invisible appliances are available to our younger patients.
While the trial came up with interesting information, I was disappointed that there was limited information on randomization, allocation, and concealment. Furthermore, the treatment endpoint was unclear, with a lack of operator blinding. This is likely to mean that the study is at risk of bias. As a result, we must bear this in mind when interpreting the data.
In addition, while there were no differences in treatment duration between the treatments. I was disappointed that they did not provide any information on the number of attendances between the interventions.
This is important because currently, some KOLs in the pay of aligner companies are suggesting we only need to see young patients a few times during treatment. This information would have helped to inform us of these ambitious treatment protocols.
I also thought that the treatment times were rather long. I certainly would not intervene at this early stage, as this adds to the overall burden of care and is potentially unnecessary. . I would correct this irregularity as part of a single comprehensive course of treatment.
Finally, it is great to see trials being done on aligners. These are beginning to provide helpful information on the relative merits of aligners and fixed appliances. This research is becoming increasingly important.
Emeritus Professor of Orthodontics, University of Manchester, UK.