What is better 018 or 022 slot brackets? A really interesting trial.
Orthodontists tend to use either or both 018 or 022 inch slot brackets. But which is better? This new trial gives us the answer.
The use of two orthodontic bracket slot widths is long established. However, there is limited evidence underpinning our choice of bracket size. This large randomised trial investigated whether there were any differences in the effectiveness of the 018 or 022 slot fixed appliances.
A team from Dundee, Scotland did the study. The EJO published it.
A randomized clinical trial of the effectiveness of 0.018-inch and 0.022-inch slot orthodontic bracket systems:
Yassir A. Yassir, Ahmed M. El-Angbawi , Grant T. McIntyre , Gavin F. Revie and David R. Bearn.
They published this study in three papers. I am going to cover it in one post to reduce repetition etc.
They set out to compare the effectiveness of orthodontic treatment with 018 or 022 inch slot bracket systems.
What did they do?
They did a large randomised controlled trial. The PICO was
Participants: 12 year old children requiring fixed appliance treatment in both arches. This included extraction and non extraction treatment.
Intervention: 022 brackets with a standardised wire sequence. The last wire fitted was 019×025 ss.
Comparison: 018 brackets with a standardised wire sequence. The last wire they fitted was a 016×022 ss.
Outcomes: The primary outcome was duration of treatment. Secondary outcomes were root resorption (score of 1 = none to 5 = extreme exceeding one third of root length), pain and final occlusal result (PAR scores).
They did a sample size calculation (based on treatment duration), used a pre determined block randomisation, followed good practice for concealment using sealed envelopes and blinded the data analysis.
They randomised 89 participants to the 018 slot and 91 to the 022 slot systems. Experienced orthodontists did the treatment.
They collected data at the start and end of treatment and 9 months into treatment for the root resorption.
What did they find?
At the end of treatment 77 of the 018 and 76 of the 022 slot patients completed the study. The loss to follow up was similar in both groups. They carried out a per protocol analysis of the data. They could not do an Intention to Treat analysis because their predictive models were not sufficiently sensitive. As a result, the findings are only relevant to patients who completed the treatment.
There were no differences between the groups in any of the parameters that they measured. The number of extraction/non extraction cases were also balanced.
I have put the main findings from the three papers into one table.
|Duration of treatment (Months)
|Final PAR score
These differences were not statistically significant.
They recorded root resorption using a five point scale and reported the numbers of participants for each grade. I did not have enough space to include this but there were no significant differences between the interventions.
They reported on many other outcomes and provided interesting data. The main points were
- Age of treatment: With each year of age the duration of treatment increased by 0.39 months
- Type of malocclusion: Class II Div 2 malocclusion required an additional 4.7 months treatment.
- Failed appointments: Each failed appointment added 1.4 months to the treatment duration.
- Emergency appointment: For every emergency appointment the duration was increased by 0.95 months.
What did I think?
I thought that this was a really good study that was well carried out and reported. Their methodology was good and the findings were clearly outlined. I recommend that most orthodontists read these papers, if you can get through the EJO firewall. Perhaps the editor will take down the wall?
The findings were interesting and relevant to our practice. I was a little concerned about the length of treatment, as this was generally high for both groups. This may be due to the complex nature of the treatment, as evidenced by the high pre-treatment PAR scores. It was also a little disappointing to find that the root resorption data was only recorded after 9 months and they did not do this at the end of treatment.
This study also concludes that there were no differences between the systems. This is a similar conclusion to many orthodontic studies. While some may feel that this is not useful. I tend to feel that these findings emphasise that the effect of the operator is greater than that of the brackets, wires and other devices that we use. This is because operators adapt their mechanics as treatment progresses. As a result, this paper adds to the evidence that suggests there is no “cook book” method of orthodontics and there is nothing magical about brackets and wires. This is probably the most important finding in this and other studies. We need to remember this next time we are selling or being sold the latest innovation in bracket design.
Emeritus Professor of Orthodontics, University of Manchester, UK.