August 21, 2023

Let’s have a look at the evidence on pre-adjusted edgewise fixed appliances.

Over the past 20 years, much research has been done into the effectiveness of edgewise-fixed appliances and treatment mechanics. These trials have provided good clinical information, but this has been somewhat disparate. Therefore, I thought it was fascinating to see this new review on trials of edgewise fixed appliances that gathered substantial evidence.

A team from the UK wrote this paper, and the British Dental Journal published the report. This paper is open-access, so you can read it.


I want to declare an interest as two members of this team, Nicky Mandall and Padhraig Fleming, have worked with me on previous research projects.

What did they ask?

“What is the evidence underpinning the use of pre-adjusted edgewise appliances, in order to better inform the selection of fixed appliance design and mechanics”?

What did they do?

They systematically reviewed the literature from June 2000 to June 2022. They included randomised controlled and clinical controlled trials. Notably, they excluded retrospective studies, case reports, and case series.


Any variation on fixed appliance attachments or mechanics.


Any treatment outcome using a validated scale or measure of treatment efficiency assessed during and after treatment.

They used an extensive and relevant series of search terms. This was not a standard systematic review, and they did not assess the risk of bias for the included studies. Nevertheless, for each study, the team provided information on its limitations.

What did they find?

The team identified many studies that looked at various interventions and outcomes. They presented the results as a narrative review of several components of fixed appliance treatment. I will list these here, but I have not got the space to go through all of them in detail.

These were

Leveling the curve of Spee, archwire sequence, effect of bracket slot and prescription, initial aligning archwires, lacebacks, space closure, and ligation methods.

As with many orthodontic trials, most of the studies they included did not identify any statistical or clinically relevant differences between the interventions. As a result, I decided to highlight factors that investigators identified as being different.

In brief, these were:

Leveling the curve of Spee

“Overbite reduction was more efficient with the use of bite turbos”.

Space closure

“NiTi closing springs were superior to active ligatures, but they peformed similarly to elastomeric chains”.

“Stainless steel closing springs were more effective and cheaper than NiTi springs”.

Notably, the archwire sequence, bracket slot and prescription, the initial aligning archwires, and using lacebacks did not have a clinically or statistically significant effect on the outcomes.

Their overall conclusion was that.

“The information from a large number of trials can be used to make evidence-based decisions in the selection and manipulation of fixed appliances”.

What did I think?

This paper provides a great deal of clinically relevant information on edgewise fixed appliances. It is helpful for all practitioners, but particularly relevant to those in training.

However, I was a little concerned about the methods that they adopted. The paper is more robust than a traditional literature review, where the authors collect a selection of studies to make a point. But it is not at the level of a full systematic review because there was no in-depth evaluation of bias, strength of evidence, detailed selection, and presentation of data. Furthermore, the definitions of the selection of papers and outcomes were not tight. I understand that the authors made these decisions to make the review more accessible and of a more manageable length.

Does this make it of limited value? I do not think so; we need to consider that the level of evidence produced is not as high as a well-done systematic review. But it does certainly point us in the right direction.

While I may appear a little negative about this paper, this is not the case. I did take home the message that the operator’s skill and the patient’s characteristics are probably more important than the choice of our appliance or adjunct. This brings us further from research that looks at orthodontist outcomes to studies evaluating our decision-making and patient values. This should be the direction of future research.  This is a very useful paper.

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Have your say!

  1. Somehow, I didn’t find it an interesting information because throughout the world, thousands of Orthodontists and ortho- practicing other dentists use whatever is accessible. The results of this study can’t be of any clinical significance.

  2. It is too bad this study was only able to look at the differences in efficiancy between 018 x 025 and 022 x 025. With the advent and proliferation of brackets with square arch wire dimensions, the dramatic claims being made about the efficiency would be interesting to evalaute. Perhaps there is no data available yet to compare a sqare bracket slot versus a rectangular slot.

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