August 13, 2018

Hang on to what you have got: A new trial on orthodontic retention.

We do not know the best method of orthodontic retention.  This ambitious trial may help give us the answer.

Orthodontic retention is one of the most controversial areas in orthodontics. As a result, there are many methods of retention. However, we do not really know which is the best method of orthodontic retention.

This new study provides us with very useful information. A team from London, South of England did this study. The AJO-DDO published it.


Dalya Al-Moghrabi et al

Am J Orthod Dentofacial Orthop 2018;154:167-74

In their introduction, the authors mentioned that while there have been several trials looking at orthodontic retention, none of these had followed the patients for longer than two years.  As a result, they set out to do a trial that looked at retainer performance over at least four years.  This is very ambitious. Let’s see how they got on.

They asked;

“What is the stability of treatment with fixed and removable retainers over 4 years”?

The secondary outcomes were gingival health and plaque accumulation.

What did they do?

This was a long term follow up of a previous study in which they looked at stability after 18 months. I have posted about this before.  I thought that this was a good study.

The PICO was

Participants: 82 orthodontic patients who had completed treatment.

Intervention: Bonded retainer made from 0175 co-ax wire

Comparator: Vacuum formed retainer (VFR). They wore the VFR retainer for 6 months full time, nights only for another 6 months and alternate nights for a further 12-18 months.

Outcome: Little’s Index and various measures of periodontal health.

They did a good randomisation, sequence generation, allocation concealment, sample size calculation and relevant statistical analysis.

What did they find?

They enrolled 82 patients into the study. After 4 years, 42 of these remained in the study.  This represents a 50% drop out.

The median increase in irregularity for the VFR group was 2.37mm and for the fixed group this was 0.85mm.  The median difference was 1.64mm.  They did not find any other effects.

When they looked at the periodontal outcomes. They did not find any differences between the retainers. However, they found that there was significant plaque accumulation and gingival inflammation for both types of retainers.

They also reported that the non compliance rate for the VFRs after four years was 67%.

Their conclusions were;

  • Fixed retainers were more effective than VFRs.
  • Both types of retainer were associated with gingival inflammation and plaque accumulation.
What did I think?

This was an interesting and ambitious trial. It was interesting to see that in their earlier report on these patients that there were no differences between the retainers. This suggests that as the retention period becomes longer, fixed retainers are more effective. This may be related to the high levels of non-compliance for the VFR group.

While this study was good. I am concerned with the high drop out rate. It was good to see that there was no difference in the drop out rate between the groups. Importantly, the study still had sufficient power.

Unfortunately, we do not know if the participants who dropped out were different from those who remained in the study. This is likely to lead to bias. For example, those who returned may have been concerned with their relapse. Alternatively, those who dropped out may have been very poor compliers with their retention.  As a result, while there is bias, we do not know its direction.

Finally, we all know that long term follow up of our patients is very difficult. I feel that the authors should be congratulated on this study. Their findings are clinically relevant. Nevertheless, you should make your own interpretation of this study in light of the high drop outs that they reported.

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Have your say!

  1. After 38 years, I have some strong ideas on retention.
    Just as Dr. O’Brien said, fixed is the way to go but I would prefer to use a thicker wire in the bottom arch bonded only to the canines. More hygienic and I have many of these still bonded after 20-25 years or more. The other advantage of a fixed lower is that assuming the OB and OJ are normal, the upper teeth settle against the lower teeth and the lower fixed pretty much stabilizes both the upper and lower anterior teeth. The problem with a VFR upper retainer (and I use them a lot) is that they don’t allow settling. So the patient goes away for the weekend, leaves his VFR home and comes back with the teeth settled but the VFR no longer fits easily. I think in a perfect world, you would actively retain the upper with a VFR for about a year and then tell the patient to go with nothing for a week or so and then make a new VFR in the “relaxed” position and that is their long-term retainer. Again, an upper fixed could be helpful in this situation also but definitely more breakage in the upper arch.

  2. Hello, Kevin and thank you for this review. Regardless of retainer type or design many “current cultures” lean on the notion that it is the doctor’s responsibility to maintain orthodontic results. The patient is merely along for the ride. On this side I advocate clear, compassionate informed consent emphasizing the patient is primarily responsible for compliance. Specifically, it is explained and in writing, “if you think something isn’t right with your retainers please don’t hesitate to contact the office for an appointment. Don’t wait more than 2 or 3 days. If you wait too long, the situation will likely become worse. This will mean crooked teeth and added expense which will upset everybody.”

  3. Hello Professor O’Brien

    Thanks for an excellent review.

  4. Hello Professor O’Brien

    Thanks for an excellent review.

  5. The conundrum of post-orthodontic treatment stability (a different issue from retention) will never be solved until we have fully identified ALL the causes of malocclusion. When we recognize and understand the causes, only then will we be able to address them appropriately and provide our patients with a permanent result.

    Part of the problem is that orthodontists tend to see ‘retention’ as the solution to ‘stability’. The reality is actually the reverse; achieving stability should mean retention will no longer be required.

    Malocclusion is not the problem; it is a sign of the problem. Conventional orthodontics provides straight teeth by addressing these signs only, but the fundamental causes (whatever they may be) are not addressed. The result is that the forces that caused the malocclusion are still in place, even if the teeth have been successfully aligned. Relapse at some point is inevitable.

    The extraordinary thing is that if we are to have fully-informed consent from the patient, the GDC and BOS guidelines require us to tell the patient that they will need life-long retention! Imagine an orthopaedic surgeon telling a patient “I can fix your hip but you will be on crutches for the rest of your life.”

    So can we please direct our scientific attention towards the actual causes of malocclusion instead of obsessing about which type of retainer or fixed wire bracket size is better.

  6. I have seen teeth move even with intact fixed rets. I use a multi-stranded dead soft wire for fixed retainer and a VFR over it to be used in case fixed retainer fails and patient is not able to return to the office in a timely manner. The VFR can also be used to reposition the tooth that might have moved out of alignment due to breakage of fixed retainer. There is no free lunch when it comes to retention.

  7. So why don’t you direct your research efforts at the causes of malocclusion instead of telling others to do so? After all, you make several unfounded claims and incoherent analogies. It’s very easy to pontificate about things when you don’t have the burden of proving any of them. This type of simplistic thinking was what led to the flat earth society.

  8. Cause of malocclusion? Like there is one cause? Why should teeth be static? They shift in patients who have never been treated!
    Permanent result? Do surgeons “permanently” guarantee surgical results? Do restorative dentists “permanently” guarantee restorations? If you want straight teeth, some degree of retainer wear is mandatory. These type of conflationary statements with unprovable hypotheses are not based on reality, and are usually made by folks pushing an agenda.


  9. Dr Busey, I wouldn’t dream of ‘telling’ anyone to do the science; I am simply pointing out that there is very little understanding, and certainly no consensus, of the causes of malocclusion, and is high time that we knew more about the process.

    Dr Kean, perhaps you would do me the courtesy of re-reading my blog, where you will find that I have used the word ’causes’ several times, and never in the singular. Of course there is more than one cause and we need to find out what they are. Symptom-based treatment is not good enough. THAT is my agenda!

    • That’s great! Perhaps when you publish the findings of your research, you can share them on this blog. In the meantime, we will focus our efforts on “treating the symptoms” as you call it.

  10. On occasion I hear speakers explain that you don’t need retention lifelong if the treatment was done correctly. Their advice is that a year or so is enough and you should never have a bonded retainer for more than a few years. Any serious research that supports this?

    Stephen Murray

  11. This is my 20th year of routinely using fixed upper and lower fixed 3-3 retainers( 0215 triplex ss bonded to each tooth). Very occasionally I use the various arsenal of removable retainers to hold expansion or for certain prosthodontic solutions. The reason is simple – I fight too hard for every .1 mm to allow a patients noncompliance ( 67% after 4 yrs in this article) too ruin my good work. It has not been an easy road, paricularly having to take the responsibility of breakages and learning to repair and correct any movement following these situations. But worth it – yes – for me it is the most important and neglected aspect of orthodontics. I like Charlie Ruff’s point about settling with the VFR. In the very few cases that I do back-up with a VFR – I will fit the upper and lower fixed – wait approximately a week for settling and then make the VFR. More often than not I prefer just the fixed upper and lower fixed with the posterior teeth settling into the neutral zone between the cheek and tongue.

  12. It appears we all have different ideas re retention and malocclusion in general. The interesting part of the above study for me was the nearly 70% non compliance rate for removable retainers. This tells me that there is no point in treating mild crowding unless you put a fixed retainer in after so maybe you shouldn’t treat mild crowding.
    From some of the comments above there seems to be an opinion that malocclusion is a problem and has to be treated and, if treated, to be retained no matter what, to maintain the slight improvement achieved. Why can’t we accept that malocclusion is not a disease, almost always causes no problems and that it’s correction is mainly an aesthetic choice? Basically most patients are not bothered if their lower teeth move a bit, only we are. By treating these things the sunk costs fallacy kicks in and it becomes “essential” to retain forever. We would be doing our patients a great service if we could bring ourselves to advise them, for starters, that lower teeth can be left a bit crooked, and if they move after braces that it doesn’t matter.
    By all means try to research the cause of crookedness and relapse etc but that does not mean that you will be able to treat differently or remove the cause. Currently the cause of relapse (or tooth movement as you get older) is probably best described as ageing. Teeth are “designed” to move to maintain an occlusion, and as we age our faces change slightly so the teeth have to move.
    Teeth are not bothered whether they are straight or not, they just want to try to fit. Since our faces are all different (as well as teeth missing or odd sizes) then almost no-one will have or can have a so-called perfect class 1. Realising this and accepting it, in mild cases (mainly non extn) is the first step to what I call Enlightenment and a better world (probably the end of global warming as well).

  13. Dear Kevin,

    Thank you for posting on our study. We are delighted to see that our findings are being read, digested and debated.

    We recognise that change following orthodontics is far from desirable and await the magic biological bullet that might obviate the need for retention. Alas, this has thus far eluded many committed, forward-thinking research groups across the globe. Until such time as this happens, we will have to continue to plan optimal retention regimes both for the short- and longer- term. Hopefully, our findings will at least make us consider this in more detail being mindful that indefinite removable retention places a significant onus in terms of compliance.

    The aetiology of malocclusion is not something that can be neatly packaged into 140 or even 280 characters. I would recommend a 2-part paper published in BJO (Mossey PA, 1999) as an excellent starting point- ideal for August holiday reading!


  14. HiKevin this was a very nice and clinically useful review. As Orthodontists we all know we need to treat or eliminate causes and the original malocclusion is at the most stable position .Keeping in view the idea of tweed if we keep teeth over the basal bone and don’t violate neutral zone and finish cases at optimum levels ,we can probably retain till the bone gets organised to lamellar bone and PDL fibres re organise themselves . otherwise in cases of suboptimal finish,neutral zone violation only lifelong retention could prove sufficient which could be burden to the patient and orthodontist . Idea of having it get settled for a week with fixed lingual retainers and then giving VFR later on for long term retention seems practical but as per this article we can rely on this for long term retention due to compliance issues.,though Dr Roberto justus showed cases with 40 years of retention with pyjama appliance and suggested lifelong retention for most patients . Thanks

  15. Very nice review Dr Kevin

  16. Hi Kevin,

    I do not provide orthodontics and I do not have postgraduate qualifications in orthodontics but I have an interest in orthodontic retention.

    With regard to long term/lifelong retention, given the potential for tooth movement in later life caused by factors including physiological mesial drift and late mandibular growth, is it not the valid to argue that “lifelong retention” is in reality “Lifelong Orthodontic Treatment”?

    p.s. Apologies in advance if this one has been thrashed out elsewhere (if so links/reference/s would be very much appreciated)?
    p.p.s, asked the same question on another forum.

  17. Hi Kevin,

    I do not provide orthodontics and I do not have postgraduate qualifications in orthodontics but I have an interest in orthodontic retention.

    With regard to long term/lifelong retention, given the potential for tooth movement in later life caused by factors including physiological mesial drift and late mandibular growth, is it not the valid to argue that “lifelong retention” is in reality “Lifelong Orthodontic Treatment”?

    p.s. Apologies in advance if this one has been thrashed out elsewhere (if so links/reference/s would be very much appreciated)?
    p.p.s, asked the same question on another forum

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