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.
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:
Orthodontic patients of any age who had fixed retainers
All forms of fixed retainers irrespective of the wire type.
Individuals without bonded retainers etc
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.
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.
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?
Emeritus Professor of Orthodontics, University of Manchester, UK.