September 12, 2016

Are bonded retainers better than vacuum formed orthodontic retainers? A new trial lets us know.

Are bonded retainers better than vacuum formed orthodontic retainers? A new trial lets us know.

I’m sure that we all feel that retention is one of the most difficult problems in orthodontics. There are several different types of orthodontic retainers but we are not really sure on which is the most effective. This new trial provides us with useful clinical information.

When I started practising as an orthodontist I mostly placed  bonded multi strand wire orthodontic retainers.  Then after a few years I noticed that I was spending a large amount of time reviewing my bonded retainer patients or replacing broken retainers. I then switched my retention regime to vacuum formed retainers, as this seemed a better option.   However, I’m still not sure which is the most effective retainer. This East end of London based team may provide us with the answer in this recent paper.

Effectiveness of bonded and vacuum-formed retainers: A prospective randomized controlled clinical trial.

Niamh O’Rourke, Hussein Albeedh, Pratik Sharma, and Ama Johal

Am J Orthod Dentofacial Orthop 2016;150:406-15

In the literature review the authors pointed out that the only guarantee of long-term stability is long-term retention.   Unfortunately, there are very few trials of bonded retainers. Earlier studies have shown that vacuum formed retainers are superior to Hawley retainers.  There is one trial that compares bonded and vacuum formed retainers after two years retention. This showed that there was no difference in relapse.

They carried out this study to compare the change in a number of dental measurements, following retention with vacuum formed and bonded retainers.

What did they do?

This was a parallel designed randomised controlled trial in which they randomly allocated 82 participants to retention with either a bonded or vacuum formed retainer. All patients had completed fixed appliance treatment.

They carried out a sample size calculation, then they used remote Web-based randomisation  to generate the randomisation sequence. A research assistant placed the allocation of treatment  into envelopes. The patients then selected an envelope to find their retention regime

Lower arch impression were taken at the start of retention and then at six months, 12 months, and 18 months.  They cast the models in stone and made dental measurements with digital calipers.   The primary outcome was Little’s Index.  Secondary outcomes were the inter canine and inter molar widths and arch length. One of the investigators measured all the models and they carried out a standard error analysis.

What did they find?

They found a low failure rate with the bonded retainers. Only three patients debonded a retainer pad.

They had good attendance up to the 12 month review.  After this point, they had problems with the attendance of the patients at 18 months. This resulted in only 60% of  the vacuum formed group and 71% of the bonded group patients attending for records. This is a substantial dropout rate.

When they looked at the relapse of the lower incisors they showed that there was an increase in Little’s irregularity index for both treatment groups over the first six months of retention. The amount of relapse for the vacuum formed retainer was statistically greater than for the bonded retainer. But when I looked at the effect size, the difference in change was only 0.05. This is not clinically significant.

After 18 months there were no differences between the two retention regimes  for all the measurements.

What did I think?

I thought that this was a good study into very relevant clinical question. They used good methods and reported the study clearly.

One potential criticism is that they did not measure the amount of removable retainer wear. I do not think that this was necessary because this was a “real-world” trial that captured information on standard treatment. This also means that the study had some external validity.

Unfortunately, the drop out rate was rather high and if we apply the very strict Cochrane tool for risk of bias, this will show that this study is at high risk. Nevertheless, this is a characteristic of long-term orthodontic studies and we need to interpret this information carefully.

It was interesting that there were no differences between the retention regimes.  As a result, I think that our patients should decide on their retainer.  We should  outline the various risks and benefits of wearing and maintaining these two different types of retainer and explain that there is no difference in their effectiveness. Most of our patients should then be able to take an informed decision on their retainer.

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Have your say!

  1. Very interesting study. But what about long term retention? Most of the patients after 1 year are getting bored of wearing the splints. Isn’t the bonded retainer a guarantee for that?

  2. What is the opinion of combination regimes. Bondable fixed retainer with a pressure formed or Hawley type retainer?

  3. Thank you for sharing us your wonderful blog !

  4. Dear Professor Kevin O’Brien,
    This is a very important topic. Thank you for thinking of discussing it. The problem of retention is very old, one of the first to analyze relapse from a scientific standpoint was AF. Lundström, who stated: “when the apical base is deficient, crowded teeth moved by orthodontic means into an accepted normal arrangement will relapse when retainers are removed”. The question is: how long should retention last?

  5. So many questions for this one, but as Prof says, ‘It’s a real world study’, so we’ll go with that.
    Were they extraction or non-extraction cases? Does that make a difference to stability? Upper / lower/ both?
    I have been discussing the options with my patients since attending a Prof Course. Patient preference ( where possible and appropriate!) is important but commitment, involvement and understanding is vital for patient compliance.
    Another great blog subject. Thank you!

  6. Hello Brian,
    A greatpost again, but I miss the evaluation of the occlusal changes. With wire retainers, the occlusion van settle much better compared to the retention with clear aligners. So not only the change in Little index, but also interarch relations should be evaluate to select the “invisable retainers” or the retention wires. Especially in cases with maxillary arch expansion the invisable retainers could be used to retain the maxillary arch form.

  7. Thank you for this post! Can I ask what wear times and durations you prescribe for VFRs, as there is a lot of debate in the clinics I work in.
    Personally I advocate Full time wear for 6 months, before reducing to 12hours a day wear for the remainder of the year. Then alternate nightly wear.

  8. “It was interesting that there were no differences between the retention regimes”

    Of course there are differences between the two regimes . . . if you place a bonded retainer and the patient develops crowding . . . it is ‘your fault’ and definitely your problem, as you placed the retainer . . . and you are obliged to find a solution.

    If you provided removable retainers and the patient develops crowding, it is their fault and their problem . . . and they have to find a solution.

    This is what determines which retainers are used in the ‘real world’

  9. Kevin
    what i find frustrating is these studies only go out 12-18 months and as we recommend ‘retention is for life’ we really need to know 10+ year data.
    I get the feeling from reading the literature is that bonded retention last better than removable/VFMs as patients tend to loose/forget etc the removable retainers. My clinical experience is bonded is best, that VFMs are better than hawleys and similar (esp post ortho/pre restorative), Hence, i use bonded retainers when a choice has to be made, unless expansion has been undertaken, then a VFM is better.
    Obviously the best option is both ie bonded and VFM, but this not financially viable under the UK NHS primary care system… which brings me on to why does the NHS pay £1200+ for treatment then refuses to maintain the retainers??
    AND why do dental schools and Vocational Training not teach management and repair of ortho retention?
    A final comment is whenever i proclaim my preference for bonded retainer over VFMs my colleagues tell me i am wrong… but every time i then ask ‘what retainers do you or your family have?’ 100% of the time the orthodontist has replied -“bonded retainer” — maybe this tells us more then we think 🙂

    keep up the great blog

  10. One factor that would have been interesting to evaluate would have been the gingival health of the patient in the lower arch. Was there a greater incidence of gingival inflammation in either group, especially on the lingual of the lower anteriors.

  11. Good review Kevin, but what about differences in the long run? I would be very cautious in your statement “explain there is no difference in their effectiveness and let them (patients) decide” since this study cannot be categorized as long term retention. We say both are equally effective at two yrs post tx, but how long are our results supposed to hold in place? And who is responsible to make it happen? Should we leave this responsibility to the patient with a removable retainer?

  12. cases with arch expansion or inter canine distances increase . bonded retainer will keep lower anterior teeth aligned but there will be relapse in arch form
    I routinely used vacuum formed retainers
    If patient doesn’t like to wear vacuum formed retainers then I used bonded retainer plus wearing vacuum formed retainers for one to two night per week

  13. I have been letting my patients decide on which type of retainer to wear for several years. I don’t charge extra for either option, and if they choose a bonded retainer, I still give them a vacuum formed retainer). I give them the pros and cons of each option (bonded retainer vs vacuum formed). Most choose the vacuum formed retainer.

  14. I have been letting my patients decide on which type of retainer to wear for several years. I don’t charge extra for either option, and if they choose a bonded retainer, I still give them a vacuum formed retainer. I give them the pros and cons of each option (bonded retainer vs vacuum formed). Most choose the vacuum formed retainer.

  15. How to address the problem of patients not wearing a vacuum formed retainer as against a bonded one?silly question may be but bonded gives somewhat more surety of retaining the results.

  16. Does the study stipulate how the fixed retainer was bonded? Just the canines or incisors as well?

  17. Kevin,
    Thanks for discussing this article. Seeing an article in your Blog always leads me back to a more careful reading of the article and its findings.
    Before saying anything further, I will say that my bias is towards bonded retainers due to their longevity past my monitored retention period and because they allow better occusal settling following bracket removal. (I rarely use upper or lower vacuum formed retainers until patients have been out of brackets for a year.)
    After rereading the article, I am going to stick with my current protocol and not offer patients a choice as you suggest. The article does show equivalence between the two methods in a good cross section of cases, but the dropout rate, especially in the vacuum formed group (48% vs 36% of bonded), is enough to prevent me from switching away from the trusty, always present, bonded retainer.
    The 48% that did not show up for the 18 month check are exactly the ones I want to see. Since they knew they were in a study looking at retention, it is easy to speculate that their failure to show up may be linked to poor retainer wear and possibly significantly larger amounts of change that may have influenced their desire to return. I feel more confident that the bonded retainer group that failed to return had very little change.
    It is to bad such a relevant, well designed study had such bad luck regarding the follow up of the vacuum formed retainers.

  18. A quick search on Twitter for ‘retainer’ will reveal the magnitude of the task you, as orthodontists, are facing. The number of people who lose or choose not to wear their removable retainers is quite staggering which considering the years of active treatment they have just gone through is something I fail to properly comprehend. It may be that following a de-bond, patients feel their treatment is over and that retention is an activity they can choose to participate in and I do wonder whether this can be improved through better patient engagement? This leads us to the question ‘who’s responsibility is retention’? I attended an interesting talk from an orthodontist at the Scottish Dental Show earlier this year in which he suggested that responsibility should lie with the patient. There are, of course, various arguments for and against this but I believe it should be a shared responsibility in the first instance as patients become accustomed to supporting this most important next phase of their treatment. The study raises some interesting questions particularly around longer term retention and I would be keen to see this being investigated so that patients who are committed to the long term success of their treatment can be properly informed about the choices they have.

  19. The problem with the vacuum formed retainers, we see a bad settling. Great site

  20. Thanks again for addressing this topic in your usual analytical way. Retention does not seem to be a big ticket item at ortho conventions, yet it is a battle for us that have been in practice for long enough. I use a mix of bonded, clear and acrylic circumferential and lower spring retainers (circumferential and spring allow full occlusion and settling). With removables I aim to get to night only asap and then cut back again from there. The choice of retainers – sorry, no real science. Significant lower incisor malalignment, palatal upper laterals and midline diastemas get bonded retainers. I like the point made by J Sandler. I served as the ortho complaints manager for four years and a significant number of patient complaints related to fractured bonded retainers. They were being charged to be replaced and despite any explanations of individual occlusal stresses, diet etc. many remained convinced that the fault was with the orthodontist/product and they should be replaced as part of the service. This is an important consideration as in some areas the dramatic increase in general practitioner orthodontics with the general dentist being a diminishing source of referrals, (satisfied) patient referrals and word of mouth are more important (my major source of referrals). Treatment planning for stability is another topic – perhaps one of those areas where we don’t necessarily know the recipe for success but we do know the recipe for failure. My own preference is to generally avoid large amounts of expansion in already good arch forms to fit them all in.

  21. Because of the compliance issue with retainers I have adopted an idea from a colleague and have a consent form signed. This says the patient/parent is happy to have the appliances removed and sets out the patient’s responsibilities for wear and returning for retainer checks (with the retainers).

  22. Generally we do; Bonded retainer on the lower jaw and vacuumed form retainer on the upper jaw ….
    sometimes both ….Thanks

  23. Kevin, Thank you once again for reviewing a very relevant topic and article. In our practice we use mostly Essix and Fixed retainers sparingly on patient request or on significant spacing cases. One of the primary reasons we elect removable (and by the way my children have Essix too!) is the concern with the increased risk of dental disease over the long term with placement of fixed retainers. I am not aware of any studies to have explored this. We all know that it is a rarely motivated patient who would display the motivation and prowess to maintain excellent oral hygiene protocol. My concern is if in fact as this study shows the small insignificant benefit with fixed retention is worth the added burden of care we assume with the placement of fixed retainers? Would love to hear your sagely input. Thanks

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