February 10, 2020

Do bonded retainers harm periodontal health?

We all use or have used bonded retainers for long term retention.  But does this type of retention do harm to our patients? This systematic review provides some reassuring information.

 Over my career, I have used many types of retainer. When I first started to treat a high volume of cases, I was very keen on fixed retainers.  I then became concerned that I was getting overwhelmed with retainer reviews.  I decided that I would “delegate” the responsibility of monitoring retention to the general practitioner. As a result, I did not see the long term effects of placing bonded retainers. However, my practitioner colleagues did raise some concerns about plaque and calculus formation.  I tended to dismiss these observations, perhaps, I did not want to hear bad news?  Occasionally, I wonder whether the large number of bonded retainers that I stuck on caused long term harm. I was, therefore, really interested to see this new systematic review on the effects of bonded retainers on periodontal health.

The AJO published this paper and a team from Bern, Switzerland and Athens, Greece.

The effects of fixed orthodontic retainers on periodontal health: A systematic review

Marie-Laure Arn et al

Am J Orthod Dentofacial Orthop 2020;157:156-64.  https://doi.org/10.1016/j.ajodo.2019.10.010

 

What did they ask?

They did this systematic review to answer this question: 

“Is there an effect of fixed orthodontic retainers on periodontal health”?

What did they do?

They did a standard systematic review with an electronic literature search, identification of paper, assessment of bias and data extraction.  Two authors did most of the work, and when there was disagreement between them, another author was consulted.

The PICO was:

Participants:

Orthodontic patients of any age who had fixed retainers

Intervention:

All forms of fixed retainers irrespective of the wire type.

Control:

Individuals without bonded retainers etc

Outcomes:

Periodontal assessments of any type with no limit on the period of observation.

They included randomised controlled trials, controlled clinical trials and prospective and retrospective cohorts.  This meant that they included lower levels of evidence.

They assessed risk of bias for the systematic reviews with the Cochrane Risk of Bias tool, the ROBINS-I tool for the cohort studies and the Newcastle-Ottawa tool for the cross-sectional studies.

What did they find?

They identified a final sample of 29 studies. These were divided into 11 RCTs, 4 prospective cohort, 1 retrospective cohort and 13 cross-sectional studies.

When they looked at the risk of bias. The authors classified six of the RCTs as being of some concern and five as high risk.  None of the cohort studies was a low risk of bias.  Finally, none of the cohort studies could be classified as a “good” study.  These findings have implications for the data analysis part of the systematic review.

When they considered running a meta-analysis on the data, they found that this was not possible. This was because there was marked heterogeneity in study designs, the type of wire used, comparisons made and the outcomes that were used.  As a result, they could only carry out a narrative review.  I will come back to this later.

I do not have sufficient space to report in detail on the narrative review.  I have read it carefully, and these are the “take-home” messages.

  • Most of the studies suggested that fixed retainers do not have an effect on periodontal health.
  • No study reported any severe effects.
  • Fibre-reinforced composite retainers may cause more harm than wire retainers.
  • A significant limitation of this review was that the observation period of the studies as the most extended period of observation was between 4 and 5 years.

Their overall conclusion was

“Fixed retainers seem to be a retention strategy that is compatible with periodontal health, or at least not related to severe detrimental effects on the periodontium”.

 In other words, they seem to be OK?

What did I think?

I thought that this review was carried out to a high standard, all the usual steps were taken.  I was a little concerned that they decided to include lower levels of evidence than trials. Particularly, as they identified 11 trials. Again, we need to remember that the inclusion of cohort studies and cross-sectional studies reduces the strength of evidence of a systematic review.

 Unfortunately, they could not carry out a meta-analysis of their data because of marked differences between the studies.  This is a common characteristic of orthodontic systematic reviews. I think that this occurs because of the stage of development of orthodontic trials. We need to follow more uniform protocols and use core outcomes, and I encourage future trialists to attempt to adopt more uniform designs etc.

Final conclusions

Nevertheless, these authors did include a large number of papers and did not find any harms from placing bonded retainers in the short term.  As a result, we can consider that this is the best evidence that we have got and we can inform our patients accordingly.  This study is, therefore, of relevance to our patients.  It would be great to see a long-term investigation into retention. But is there anyone out there who can devote 10 or more years to answer this question?

Have your say!

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    Thank you for your review.

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    a nice review: however the RCT comparing bonded retainer vs no retainer is required over a long period eg 10+yrs
    we do know and accept some patients just don’t clean well enough and/or have a high calculus deposit rate.
    Until i see good evidence, personally I will stick with ‘Dual retention’ – both bonded and essix/VFM

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    In the last 2 years, I have seen two patients who had fixed retainers placed many years ago in another practice. In both cases, a single tooth was torqued almost out of the alveolar housing (a lower cuspid and a lower lateral). I attributed this to the technicians’ failure to heat treat or pacify the wire, so it was placed with torque built in which was expressed over time. This phenomenon also explains crooked teeth when a fixed retainer is still attached. Like so many things we do, it is technique sensitive. And, different patients react differently to permanent retention.

    I like to keep things simple and go with a “standard” removable retainer (Essix style) and a fixed retainer only on request (with a substantial fee added).

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      John Wise, I have found several cases over the years of incisors torqued on bonded retainers as you described. It is always caused by a tongue thrust. While your theory is plausible, think about the 3-3 sitting on the tray, passive, unattached to any thing. Any torque in the wire would express at that point. There is no way for a lab bend wire to store torque if it passively lays on to the teeth when it is bonded.

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    Hello Brian thank you fo your energy and scientific approach. However I regret, may be I didn’t read your review carefully enough, I regret you didn’t seem to make a distinction between upper and lower retainers. I have now 44 years of practice with many many cases finished to centric relation and canine protection. Cases that I was able to monitor over 40 years… I wrote a little article for my patients and colleagues whose conclusions are the following: lower fixed retainer 3×3 only glued to the canines for life. No absolutely no upper fixed retainers on good Cl1 cases to a few case with initial severe anterior rotations. Because , they are food trap , dental floss obstacle, anterior neo-prematurities to good cases, created the risk to wire elongation thus space opening thus upper cone from 13 to 23 opening and finally bite deepening. They could be be helpful in Cl2 and compromise cases …as an American trained orthodontist in Paris I see a lot of emergencies with upper wires and I am glad my cases don’t end up like those…

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    Considering periodontal disease develops over many years I would be hesitant concluding that they are okay.

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    great post kevin

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    Thanks for the review. I wouldn’t embrace their overall conclusion so easily – I don’t forget your former blog “be aware of old retainers” which sheds a different light on the subject.

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    Studies like this are very ,very valuable.In a busy clinical practice we need protocols to deal with day to day realities.
    I ,strongly, believe that at the end of active tmnt.we provide the pt with the means to retain the teeth ,then it is up to them.Put the emphasis on the pt.where it should be ,in my view.
    My suggestion ,build in a 2 or 3 months passive appliance stage towards the end of active tmnt.,debond,remove attachments.Bonded wires as needed.Upper and lower slip cover ,clear retainers eg.vivera.
    99% of the time ,no movement at all .Very important to have a signed contract to state that retention ,at night starts ,now.Any broken retainers ,damage etc.are covered for 18 months and otherwise a fee is charged -give an idea of cost.
    Dont lose sleep and stress over an issue that is not under our control and not our responsibility.
    Hope this,maybe ,helps someone.
    I decided to minimise stress in my life a couple of decades ago and this is part of my tactics.
    Again ,just my view.
    TMJ cases are vastly different but thats for another day.
    PS no follow up appts neede and I always recommend 8,s removal.Again ,up to the pt /parent.

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