July 30, 2018

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.

One: doi:10.1093/ejo/cjy037.

Two: doi:10.1093/ejo/cjy039

Three: doi:10.1093/ejo/cjy038

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.

018 022
Duration of treatment (Months) 29.3 (SD=9.3) 31.2 (SD=12.3)
Final PAR score 7.4 (SD=5.1) 6.0 (SD=4.4)

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.

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Have your say!

  1. Osteblasts and Osteoclasts and everything else that is responsible for toothmovent reacts to forces and moments. Theeth don’t feel what kind of slotsize you use or which company has produced the bracket. They react to the forces and moments you apply.
    Not more and not less.
    By the ways:
    The famous windsurfer Robby Naish can do his job better than me- even if he uses an old wooden door.

  2. New (and some old) findings suggest that most bracket slot dimensions far exceed manufacturers’ stated slot dimensions.
    In addition, many bracket slots have slot shapes that are more open at the mouth than at the base. These findings speak to the fact that the inaccuracies in current manufacturing techniques render a discussion about bracket efficacy somewhat meaningless.

  3. hi Kevin

    thanks for that – interesting to read the effect that missed appointments and “emergency appointments” had on duration. You said you’d like to see the root resorption reviewed at the end of treatment – would that require extra ethical approval as it would have little effect on the individual patient’s management (beyond telling them not to get perio disease)?

    Stephen Murray
    Swords Orthodontics

  4. I have been involved in PAR scoring calibration/ grading etc. You mention that the pretreatment par scores indicated a high complexity of treatment. My training/belief/understanding of the Par scoring system is that it has no correlation with complexity of treatment?

    • Thanks for the comment. Yes, you are correct that PAR was not intended to measure complexity. I took this quote from the paper but did not put it in quotation marks. However, we did some work a while ago when we did the USA weightings for PAR and we showed that there was a strong association between PAR scores and perceived complexity. But we did not develop this further.

  5. Hello Kevin, I agree that this study is interesting, especially because the wire size seems to be properly adapted to the bracket size. But do you have an article showing bidimensional bracket sizes?

  6. Would love to see a study between 0.018 16×22 for the biggest wire size and 0.022 slot with 16×22 for the bigger wire size.

    I use 0.022 slot and almost never use bigger than 16 22, 17 25 in some rare case. To the best of my knowledge most of the orthodontist in South Easia work the same.
    Did a very interesting course on Miniscrew with Pr Park at Daegu university where on the mechanic part he started to explain, why he switched from 0.022 with 19×25 and higher , to 0.022 with 16×22.

  7. Two and a half years is too long for any average orthodontic treatment time.

    • Treatment length is sometimes dictated by orthodontist compensation. In Scotland, orthodontic treatment is covered by govt healthcare (NHS) for x months. I don’t remember the max amount of months, but I would bet it is around 32 months. So there is little incentive to finish treatments in 18 months (shorter treatment time, less total compensation by govt to Orthodontist). I recall that treatment times in the Netherlands, a similar system, is about 5 years !

      On the up side, all children under 18 qualify for ortho treatment.

  8. The generalizability of this study is low. I can tell you that in Hispanic and African populations, the leveling difference of .022 slot is signficiant in producing more timely and better treatment results.

  9. After a well-conducted study and well appreciated by Kevin(we seldom see this), we are into square A again- 0.022 or 0.018 which slot is better, as per available evidence? It’s just like which car is better, rather than the competence of the man behind the wheel! Whether the ingradients/recipe determine the quality of the dish or the skill, competence and experience of the chef ?
    My take on the study is, as rightly observed by others, “The Orthodontist is (has to be) in the Driver’s seat”- Not the appliance, prescription, brand, appliance manual or sponsored(?) publications. They come third after second place to the patient!

  10. You do a fantastic job making us think about cause and effect. Much appreciated.

  11. Dear Dr O’Brien
    The last paragraph of your article should be put into a frame hung to the wall in front of the dental chair so that every orthodontist will be reminded of its content at all times. It is absolutely true “there is no cook book” that we can just refer to in order to make treatment more successful in terms of time or quality. And yes, the walls built by Journals make it difficult for practitioners to read articles and feed their minds.

  12. What about the torque expression finishing with a .018x.022 wire? The study is well conducted for sure but there’s no reason in not assessing the torque exprerssion with full size wire. The big difference between the .022 and .018 system is all in the final wire for anterior control. I will define the paper simply incomplete.

  13. what is the the impact of patient perspective to the treatment outcome?
    There were couple of studies shedding the light on the torque expression achieved by different pre adjested brackets among specialist, and inclination of teeth!

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