November 29, 2021

How long does it take to align teeth?

We all want to align the teeth as quickly as possible to get on with orthodontic treatment. But, surprisingly, we do not know how long it takes to align all the teeth in an arch. This question was answered in this good systematic review.

Alignment is the essential first phase of orthodontic treatment. As a result, the duration of alignment influences the overall length and burden of a course of orthodontic treatment.  Furthermore, we know that the speed of tooth movement is controlled by the biological response.

Ideally, we would also like to increase the rate of tooth movement. Efforts to achieve this have used different types of brackets, wires, and other methods.  While a large amount of research has been done into the speed of the alignment. We do not really know the length of the alignment phase of an average course of fixed appliance treatment with a degree of certainty.

A team from London and Bristol in the beautiful south of England and Zurich did this study.  The AJO-DDO published the paper.

Duration of tooth alignment with fixed appliances: A systematic review and meta-analysis

Fidaa Wazwaz et al.

AJO-DDO: Advanced access.

What did they ask?

They asked this simple question:

“How long does it take achieve whole arch alignment of the mandibular dentition using fixed appliances”?

What did they do?

They did a detailed systematic review of the literature. Firstly, they did electronic and hand searches followed by paper inclusion. Then they extracted the data and carried our relevant meta-analyses. The final stage was assessing bias with the Cochrane Risk of Bias tool.

The PICO was

Participants: Humans of any age having orthodontic treatment

Intervention: Fixed orthodontic appliances

Control: Randomised controlled trials of any comparison

Outcome: Duration and rate of orthodontic tooth movement.

What did they find?

They did the systematic review well. The authors then selected a final sample of 35 publications that reported on 35 trials.

Sixteen trials (45%) reported on non-extraction treatment, 6 (17%) were on extraction and non extraction and 7 (20%) extraction only.

The average baseline irregularity was 2.1-11.8mm.

They reported many variables that were looked at in the trials, and I will not go into these here because of lack of space.

When they looked at the risk of bias. This was high for 5 trials; in 10 trials, they had concerns with the randomisation, and 20 trials had a low risk of bias.

Let’s look at the data on tooth movement. I thought that this was interesting.

  • It took 263.0 (8.8 months) to achieve whole arch alignment of the mandibular teeth.  The 95% CIs were 6.2-11.3 months.
  • To just align the incisors, it took 110.7 days (3.4 months), 95% CIs were 2.8-3.9 months.
  • There were very high levels of heterogeneity across the studies. As a result, the authors suggested that we look at the Cis rather than the pooled averages.

When they did the meta-analysis, this showed the following:

  • There were no differences in whole arch alignment between self-ligating and standard brackets.
  • Surgically assisted orthodontics reduced the time to initial alignment of the anterior teeth by 44.3 days (95%CI=20.0-68.9 days).
  • The quality of evidence using GRADE was high for the lack of benefit of SLBs and surgically assisted orthodontic treatment.

Their overall conclusions were

“The duration of treatment for mandibular alignment was 263 days”.

What did I think?

This was an excellent clear, and well-done systematic review. The authors looked at a very relevant clinical question, and they wrote an excellent paper.

As with all reviews, there are some problems with heterogeneity between studies, which influences our confidence in the findings. Nevertheless, the overall strength of evidence using the GRADE approach suggested that we may be reasonably sure about the results.

I thought it was interesting that they reinforced the finding that self-ligating brackets do not influence the time to align the teeth.  It was also interesting to see that surgically assisted orthodontic reduced alignment time by 44 days.  This may be meaningful to our patients and we need to consider whether this reduction in alignment time is worth the cost and burden of having an invasive procedure. I feel that it is not worth it.  Furthermore, our most important outcome is the total duration of treatment and this was not reported in any of the surgically assisted trials.

Final thoughts

We need to consider whether this review adds value to our knowledge. I think that it does in two main ways. Firstly, we can assess whether our own alignment times are within the average reported in this paper.  Secondly, when we read the literature on the speed of tooth movement, we can factor in these findings as part of our critical appraisal.

It is great to see a systematic review that comes up with valuable findings.



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Have your say!

  1. Just under 9 months, (with a range of 6.2-11.3 months), is a very long time, if we define alignment time as the time it takes to get to a rectangular working wire.

    From my very biased observations, in my unsponsored hands, without using SLB’s, it generally takes 2 to 6 months to insert a 19×25 TMA, with an 8 week appointment interval.

    Good to see no benefit or magic with SLB’s and what amounts to less than a 20% reduction in alignment time with surgically assisted orthodontics and their associated costs and morbidity.

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