Relapse of extraction and non-extraction treatment. A long term study.
One of the most controversial areas of orthodontic treatment is the decision on whether to extract teeth or not. Research has been sparse on this crucial subject. The AJO published this new paper and I thought that it was helpful.
I do not often provide a comment on retrospective studies. However, there are specific questions that cannot be answered by prospective cohorts or trials. One of these is the long term effects of extraction or non-extraction treatment. This is still a very controversial area of orthodontic treatment. In general, the opinion of clinicians and researchers is that the extraction of teeth does not cause any harm. Nevertheless, the choice of treatment mechanics may lead to some problems. The counterpoint is that extractions result in over retraction of the upper teeth and cause a myriad of problems. Indeed, some have suggested that extractions are the amputation of body parts!
This debate is never-ending, and I doubt that it will ever end. As a result, I was very interested in this new paper. A team from Brazil did the study. The AJO-DDO published the article.
What did they ask?
They asked this simple question.
“What are the long term outcomes of orthodontic treatment for extraction and non-extraction patients”?
What did they do?
They did a retrospective study to look at relapse. The authors obtained the records of patients from the orthodontic department of Bauru dental school. The inclusion criteria for the study were:
- Class I or Class II malocclusion at the start of treatment
- Non-extraction or extraction treatment (4 first premolars)
- Complete fixed appliance treatment
- Retention with Hawley retainer (and lower bonded retainer for at least three years
They obtained dental casts and panoramic radiographs at pre-treatment (T1), post-treatment (T2) and long term follow up (T3). This period was a mean of 37 years after treatment.
They selected the records of 57 patients. Group 1 was 16 subjects who they had treated without extractions, and Group 2 included 41 subjects treated with extractions.
The primary outcome measure was occlusal change. They measured this with the Peer Assessment Rating and the ABO OGS. They also asked the patients to complete a satisfaction questionnaire that they sent out via WhatsApp.
I could not find in the paper any mention of how they identified the patients so long after their treatment. I think that this is important, and I will discuss this later.
What did they find?
The mean length of the extraction treatment was 2.3 (0.5) years, and for the non-extraction treatment, it was shorter at 1.8 (0.8) years. This difference was statistically significant.
I am only going to include the occlusal index data for the PAR index. This is because I understand it more than the OGS, and it does not rely on recording the technical aspects of treatment such as angulation of the teeth. Furthermore, we can apply PAR at the start of treatment. This information gives us data on the pre-treatment dental morphology of the patients.
Here is the relevant data.
|Extraction||23.7 (19.5-27.8)||3.1 (2.2-3.9)||7.5 (5.3-9.6)|
|Non-extraction||25.7 (22.7-28.6)||2.8 (2.0-3.5)||8.6 (5.6-11.6)|
“There was significant post-treatment relapse in the long-term for both groups of patients”.
I thought that their survey data was perhaps more important than the occlusal index scores. This is because they collected information that was relevant to our patients. When they looked at this data, they found that 72% of the sample responded. Unfortunately, when I looked closely at their data, I found that only 13 of the non-extraction and 28 of the extraction group responded. This means that we must be uncertain of these findings. Their main finding was that there were minimal differences between the groups. However, the non-extraction group reported more changes in alignment than the extraction group.
What did I think?
When I interpreted this paper, I had to decide whether the scientific method was sufficiently robust. Firstly, this was a retrospective study. As a result, we must suspect that there was selection bias. Furthermore, the authors did not state the response rate for long-term recall. This information is crucial for a study of this nature, as it gives us information on response bias. Importantly, we need to consider if the responders are different from non-responders. In the absence of this information, it is difficult to come to any conclusions, and I have to assume that there is significant uncertainty in this data.
I was also concerned that they did not provide any information on how they identified and approached the patients to obtain long-term data.
However, we also need to consider the difficulty of obtaining long-term samples of orthodontic patients. In this respect, I respect the work and the success that the investigators had in obtaining their sample. In many ways, I suggest that this is the best that we can get. As a result, I think that we should accept their findings. Nevertheless, there is a degree of uncertainty in the data. This is reflected by the relatively wide 95% confidence intervals.
We also need to consider that there must be something, aside from random decision making, that persuaded the operators to extract teeth or not. This concept means that we cannot approach this data as being similar to a randomised trial. Again, this adds to potential bias.
It was interesting to see that they felt that there was significant relapse with both the non-extraction and extraction approaches. I was not sure that I agreed with this conclusion. This is because the amount of relapse was in the order of 4 PAR points. This is not clinically important.
It was interesting that there was no difference in relapse between the groups. This finding suggests that in this sample, the extraction of teeth did not influence relapse. Nevertheless, there was a shorter treatment time with non-extraction. As a result, there may be some advantages to the non-extraction approach.
I also need to point out that they did not provide any information on the aesthetics of the final treatment result, breathing, life performance, bedwetting, arch width or any other magical effect of non-extraction treatment. I think that the non-extraction/extraction wheel will keep turning.
Emeritus Professor of Orthodontics, University of Manchester, UK.