A trial suggests that Clear Aligner Treatment is a shorter duration than braces.
At last, we are seeing more research papers on the effectiveness of Invisalign. This new trial looks at the duration of treatment with aligners and patients’ quality of life. The findings do not agree with the conclusions of another report on the treatment duration of Invisalign treatment. It is worth a close look.
While aligners have been around for many years, we still do not know much about their effectiveness. This deficiency is particularly true regarding their effect on oral health-related quality of life. These outcome measures are becoming increasingly important as dental research moves towards outcomes relevant to patients. This work is essential because it provides information on the effects of our appliances during and after treatment.
A team from Damascus, Syria, did this trial. The EJO published the paper.
Alaa M. H. Alfawal et al. EJO advance access. DOI: https://doi.org/10.1093/ejo/cjac012
What did they ask?
They did the trial to find:
“What is the impact of clear aligners on patients’ Oral Health Related Quality of Life (OHRQoL) and the duration of orthodontic treatment compared to fixed appliance treatment”?
What did they do?
The team carried out a single centre two arm parallel group RCT with a 1:1 allocation. The PICO was:
44 adult orthodontic patients with Class I molars and mild malocclusions (2-6mm crowding). They treated the patients without extractions.
Clear aligner treatment. Follow-up appointments every two weeks.
022 MBT fixed appliances. The patients attended every three weeks to have their appliances adjusted.
Oral Health Quality of Life using the Oral Health Impact Profile (OHIP-14). They collected this data at the start of treatment, then after 1 week, 1 month, 3 months and 6 months and post-treatment. The secondary outcome was the duration of orthodontic treatment in months.
One experienced operator did all the treatment.
They used an ITT approach in which all patients were analysed, regardless of the outcome. They analysed the OHIP data with multiple regression. The treatment duration between the interventions was analysed with t-tests.
The team used pre-prepared randomisation. They concealed the allocation with sealed envelopes. This was done by a researcher who was not involved in the trial. As a result, it was impossible to blind the operator or the patient to treatment allocation.
What did they find?
All the patients completed the study. This meant they had two groups of 22 participants who received treatment with fixed appliances or aligners. There were no differences in the mean ages, gender or discrepancy index data between the two groups at the start of treatment.
There were no differences in the OHIP-14 scores at the start or end of treatment. However, during the early stages of treatment, the oral health quality of life for the fixed appliance group was significantly lower for the fixed appliance group. This was reinforced by the regression.
Treatment duration was 15.73 (SD=2.45) for the fixed appliance group and 11.55 (SD=2.0) for the aligner group. This was a difference of 4.1 months (95% CI=2.8-5.5). This was statistically and clinically significant.
Their overall conclusions were:
“The Oral Health Quality of Life of patients treated with Clear Aligners was higher than those treated with fixed appliances throughout the course of treatment.”
“OHRQoL was improved by orthodontic treatment regardless of the treatment method.”
“Clear aligners reduced treatment time by 26% compared to fixed appliances”.
What did I think?
This was an interesting small trial. Firstly, let’s have a look at the good points. The groups were similar at the start of treatment. The randomisation was pre-prepared, and the allocation was concealed. Notably, the team followed the patients to the end of their treatment.
When I looked for components of the trial that were not ideal. There were several that we need to consider when we interpret this paper. Firstly, I was unsure whether any of the differences in OHRQoL were clinically significant. Furthermore, I was unclear on why they chose a slight difference in OHIP14 scores when they did the power calculation.
I was more concerned that the patients were seen at different time intervals. This was 3 weeks for the fixed appliance group and 2 weeks for the aligners. I was also unclear on why the aligner patients attended for aligner changes. As a result, I cannot discount that the difference in treatment times may have been influenced by the treatment interval.
I also could not find any information on how the operators judged that treatment had been completed. Furthermore, there was no data on the final occlusal result at the end of treatment. Both these omissions could influence the duration of treatment.
Finally, strictly speaking, the lack of blinding puts the trial at risk of bias. Again, however, this is like all orthodontic trials.
I have thought hard about this trial. But, first, we must consider why another study suggested that fixed appliances were faster than aligners. This may be due to the methodology and other issues. However, we are now seeing more investigations into the effectiveness of aligners. This means that soon we can do meaningful systematic reviews. This will allow us then to make recommendations to our patients.
Emeritus Professor of Orthodontics, University of Manchester, UK.