An occasionally irregular blog about orthodontics

Fixed retainers do not prevent relapse? A long term study.

By on July 3, 2017 in Recent posts with 23 Comments
Fixed retainers do not prevent relapse? A long term study.

Fixed retainers do not prevent relapse: A long term study.

One of the greatest challenges in orthodontic treatment is our ability to retain our treatment.  Even though orthodontic retainers have been researched for years, our level of knowledge about retention is surprisingly low. This new paper provides us with interesting, but perhaps, disappointing information.

Stability of orthodontic treatment outcome in relation to retention status: As 8 year follow up.

Jenette Steinnes et al

Am J Orthod Dentofacial Orthop 2017;151:1027-33

http://dx.doi.org/10.1016/j.ajodo.2016.10.032

A team from Tromso in Norway did this interesting study. In their introduction, they pointed out that fixed orthodontic retainers are the most commonly used form of retention in Norway. However, there are few long term studies of their effectiveness.  They set out to answer the following question.

“What is the stability of orthodontic treatment outcome and retention status 7 or more years after placing fixed retainers”?

What did they do?

They identified a sample of patients who they had treated in the public orthodontic service from 2000-2007.  All the patients had originally presented with more than 4mm crowding in the mandible or maxilla. They also had to have full records.  They found 105 eligible patients and sent an invitation to them asking if they could attend a follow-up examination.  When they came to this appointment the authors took impressions for dental casts and collected data on the process of treatment, the type of retainer, compliance and satisfaction with treatment.  They then scored the study casts with the PAR and Little’s Irregularity (LII) Indices.

What did they find?

67 (64%) patients attended for the appointments. The average time between the end of treatment and the second data collection was 8.5 years.  90% of the patients had been fitted with a mandibular fixed retainer.   In the maxilla 54% had a fixed and removable retainer, 39% had a removable only and the remainder had no retention (4%) or fixed only (3%).  At the long term recall visit some of the patients had stopped wearing their retainer or it had debonded. This meant that they had a sample of patients with and without retainers at the second visit. As a result, they could make comparisons between these groups to identify the effect of retention.

They provided a large amount of detail on the dental changes in retention and I have summarised them in this table.

Little's Irregularity Index (means and 95% CIs)

 StartFinishPost-retention
Maxilla9.6 (8.4-10.7)1.7 (1.3-2.0)2.8 (2.3-3.1)
Mandible7.4 (6.5-8.2)1.1 (0.8-1.3)2.1 (1.6-2.5)
pNS0.001

Increase in LII (mm) in maxilla and mandible

 RetainerNo Retainerp
Maxilla0.761.150.33
Mandible0.651.820.001

They also found that in the maxilla there was no difference in the amount of relapse between the patients who did or did not have retainers. That is the retainers did not prevent relapse.  I presume that this was because of failure in bonding etc, but they did provide any additional data on this.

When they looked at patient satisfaction, most of the patients were satisfied with the treatment outcome.  However, more than half noticed that their teeth had moved after treatment.

What did they conclude?

They concluded that

  1. Occlusal relapse occurs irrespective of the use of long-term use of retainers.
  2. A fixed retainer is effective in the mandible, but it did not appear to make any difference in the maxilla.
What did I think?

I thought that this was an interesting paper that outlined an ambitious project.  When I looked at the results it was interesting to see that despite most of the patients wearing their orthodontic retainers, the average relapse in PAR index scores was 14%.  This is clinically significant, but it may be composed of a number of minor factors, for example, mild lower incisor crowding and increase in overbite.

Importantly, the use of retainers in the maxilla did not have an influence on changes of maxillary incisor irregularities.  However, in the mandible the patients without a retainer had significantly more relapse.

When we read a study like this we need to interpret the results by thinking about several important points.  These are:

Effect size and confidence intervals

The differences that they detected between the groups were rather small. For example, the amount of relapse, according to Little’s Index was only 1mm. I am not sure if this is clinically significant. The confidence intervals are not too wide and this shows that we may have moderate certainty in the data.

Strengths

This was an ambitious study and they recalled a high number of patients who had various levels of success in wearing their retainers.  Their choice of outcome measures was logical. The PAR index measured all components of relapse and the LLI was directed at visible incisal relapse. They also used patient satisfaction as an outcome that is relevant to our patients.  Interestingly, the results reflected clinical experience as there was more relapse in the lower incisors.

Weaknesses

This was a retrospective study and one of their selection criteria was that the patients had good records.  This introduces selection bias because we are not sure why some of the patients had complete records and other potential patients did not.

While the response rate is high. We must assume that those who attended for the follow-up appointment were different from those who did not attend.  This is response bias and is important. For example, the patients who had relapsed may be more likely to attend. Alternatively, the patients who attended may be pleased with their long term result and want to share this with the orthodontists!

Orthodontic retainers; Putting all this together..

My feeling is that this is a study that may be considered to be “best that we can get”.  I think that it provides useful information and reinforces that relapse is inevitable, particularly in the lower incisors.  It also shows that the concept of long-term retention may not be the answer to preventing relapse.  However, there is a degree of uncertainty present because of the methods and response rate.  So it is up to you to decide whether these findings are robust.

Let’s see if we can have a good discussion on this in the comments to this post.

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There Are 23 Comments

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  1. vicki vlaskalic says:

    Great topic Kevin, interesting study. Informing patients of pros and cons and long-term outcomes of fixed retention is important – no such thing as “a permanent retainer”, maybe “indefinite retention regimen “. I wonder if we are measuring orthodontic relapse or physiologic change, and will we ever be able to tell? Until we know more about inevitable inherent movement in the untreated dentition over time, we may not be able to conclude a whole lot. It also amazes me that some people still believe that a well treated dentition can be made “stable”. Hello!…..everything – everything – in the universe, let alone our bodies, moves over time. Even well aligned, well interdigitating teeth with parallel roots! Question is can we make this movement clinically insignificant by decreasing inherent instability, as opposed to “increasing stability” with our various finishing techniques, positions, retainer types, cytokines, etc?

  2. Bethany says:

    I think this study will add a lot of value to the conversation with parents regarding choice of retention method. I find myself trying to emphasize the weakness of fixed retention (especially maxillary), but so often patients have their minds made up that it’s going to be the best solution for them. This will add value to the informed consent that I can offer. Thanks for writing about it!

  3. Geoffrey Wexler says:

    I think it’s important to look at the indices of irregularity in individuals with survivng fixed retainers.

    Its unrealistic to think that things a dentist make (once) last indefinitely.

  4. Sia Maani says:

    Thank you Brian for sharing this. I agree that it’s a great study, confirming what most of us general dentists already knew or suspected, as we tend to see our patients grow up and become adults over a longer period of time compared with our specialist colleagues.

    Let’s face it, we can’t stop teeth from moving. Long-term complete immobility equals the death of the tissues. However, the main question here is how we can make the unwanted post-treatment movements minimal, and inline with our natural growth and changes as we mature.

    In my experience, as a general dentist with a very high interest in Orthodontics, the roll of functional aspects of the mouth and the masticatory system have not received sufficient attention in the past.
    My orthodontic patients with natural and balanced oral forces from the tongue, lips and cheeks, always exhibit a more stable result, year after year. Relapse, at my clinic is mostly noted in patients who present with some kind of hyperfunction in their soft tissues, such as tongue thrust, tight Mental muscles and mouth breathing.

    The conclusion I draw from the above, is that only having a balanced and aligned set of teeth doesn’t promote long-term stability, however, when accompanied by a balanced oral muscles’ function, it shows a much higher long-term success.

    As an actionable conclusion to serve our colleagues and patients, I’d like to mention that in cases where some kind of functional imbalance is present, Functional Activator Therapy is carried out at our practice, preceding and accompanying the fixed orthodontic treatment. The functional therapy includes customised exercises and part-time wear of removable activators to de-, and reprogram the muscles involved in the various oral activities.

    I am aware that this concept hasn’t found its place in the UK (yet), however, I believe that in order to serve our patients in the best possible way, we must be open to the ideas that are simple and practical, with great results.

    • Catherine Murphy says:

      Thank you Sia. I agree, muscle balance is key to long term retention. Habits such as tongue thrusting do not spontaneously resolve themselves and will lead to relapse. Muscle balance and myofunctional therapy remain unconventional here in the US as well.

  5. Dear Kevin, just the one comment – Many thanks for your enthusiasm and your Blog – why hasn’t anyone done it before? With kindest regards, David Green

  6. I hve observed the same in my practice too that bonded fixed retainers donot prevent relapse. i am not able to find a permanent solution to relapse. Kindly suggest some.

  7. Gerald Samson says:

    Hello, Kevin and thanks for another in your fine, diligent series. In addition to this interesting report I seem to recall that essentially every long-term study of changes in the dentition without orthodontic intervention (Michigan, Bolton, Burlington, etc) reveals that teeth shift with age – orthodontic treatment or not. Everyone’s face changes with age and the dental alveolar structures are obviously part of the face. Teeth “shift with age……..it all shifts with age”. From a clinical application, years ago I started explaining to patients (and parents) that teeth shifting with age is part of the aging process of the face. Most people accept “aging” of the face and teeth. Therefore, I stopped using the term “relapse of teeth” and started using “aging of the face and teeth”.

  8. Robert Stoner says:

    Maintenance of original arch form and not expanding the lower canines or premolars is your best bet

  9. I have wondered about this topic more than once. There are several variables that are not considered in this paper. What type of fixed retainer was used? Was the retainer a solid bar connecting the canines only or was it a flexible braided stainless steel wire bonded to each tooth, or was it only bonded to the incisors and not the canines? I have seen many come through my practice and each has benefits and drawbacks. A prospective study with several bonded retainer types needs to be conducted and compared to removable renention to get ‘best practices’ that we can follow.

  10. Kevin please keep up the tremendous work. Thank you. My question would be…How were they treated? Were all the arches expanded? Were these extraction cases?

  11. Ray Reed says:

    I wonder if the recent trend to fewer extractions could be a factor.
    Pure speculation, of course.

  12. Peter Southall says:

    Excellent review Kevin, thank you! Now, who’s going to do a prospective randomised study?

  13. Eman Fatani says:

    stability of our work is a continous challenge we try through proper diagnosis ,good mechanics and proper choice of retention(which ?) to maintain structures that are always normally changing by aging process our eating habits and health condition (too many variables)

  14. andy pearson says:

    Thanks Kevin,
    Probably the best solution to this issue is not to treat in the first place. We all have an idea of what cases will have a high chance of relapse so maybe we should do our best not to treat these cases and advise the patient appropriately. Day in and out I encounter patients obsessed with slightly crooked lower teeth and I can’t help feeling that we have only ourselves to blame for this (the obsession that is). Instead of gluing the teeth together, forever, maybe the best option is to set them free (free, free set them free) so that they can shift and adapt as the face changes.

    I don’t wish to be out of a job but I feel that we should draw the line somewhere. Let’s just stop treating mild lower incisor crowding for starters, there’s more to life than straight lower teeth that will move anyway. Let’s embrace normal aesthetic variation in the teeth and do everyone a favour. (mid-life crisis rant over)

  15. Kerry Shooter says:

    Thanks for your ongoing critiques Kevin.
    As some posts have noted, there are so many variables here to do with non-extraction v extraction, expansion etc etc, but I think the point is that this is only meant to be an overall snapshot and nothing more. (Sidebar – I am always a tad confused about immediate post-tx irregularity – patient-driven debands??)
    I think what does need to be expanded upon in more studies is the type of retainer, retainer wear regime, frequency of retainer checks etc. Is a lower bonded retainer bonded only to canines better at retaining teeth than one bonded to every anterior tooth? Should patients with retainer debonds be eliminated from the study, since technically they aren’t retaining any longer? I suspect we will never get a wholly conclusive answer, but every little bit of (good) research helps.
    Personally I seldom do upper bonded retainers because: (1) I hate replacing/repairing bonded retainers (2)upper bonded retainers lead me to point (1) too often

  16. Lysle Johnston says:

    When you park your car, the receipt says, “Not responsible for items left in car.” When you check your coat, the tag says, “Not responsible, etc, etc.” The courts, however, do not agree; these folks are responsible. O.K., you give a patient some sort of result, a fixed retainer, a prophy, and the sincere admonition, “Now, it’s all up to you.” Eventually, you will have thousands of folks out there with your appliance in their mouth. Your appliance. Your patients. The sum of many tiny probabilities adds up to almost a certainty that something will go wrong. Your appliance. Your patient. At the outset, it probably would be better/safer to seek more stable outcomes. Just because you can glue the teeth together (in any position) doesn’t mean you should.

  17. sam says:

    Thankyou Kevin for highlighting this topic. I’m a GDP and for the last three years or so I’ve been treating patients with functional appliances. I am far from an expert and will probably continue learning around the subject for many years to come. I think it would benefit the dental/ortho profession if we spent some time understanding why malocclusions form in the first place. Throughout my dental school days it was drilled into me that malocclusion is genetic and to be honest I never really questioned it.
    Is it genetic though? I doubt it. The genetic theory is convenient because we can draw a line under it. Much like a TMJ patient who happens to be female is hormonal!
    Malocclusion has not spread in common with how a genetic disease spreads. Malocclusion did not start in one region and then spread across Europe to America etc. Why are we seeing such variance in facial proportion and yet most of us are growing pretty normal hands/legs/shoulders? Why don’t other mammals display such variance in malocclusion?
    I’m of the opinion that most malocclusion’s are caused by the bones of the face not growing properly. Most likely this is due to nutrition, allergy and feeding habits as an infant. In turn, this leads to the development of abhorrent breathing and swallowing patterns, hence the bones of the face are not growing as nature intended. If we intercept functionally and get the bones to grow properly then we can indeed achieve a stable result or at least come closer to it. The kids might not end up with wall to wall straight teeth and convergent centrelines but they’re healthy.

  18. Very nice discussion. Thanks for raising this issue Kevin. Here’s a few points. The word and concept of ‘relapse’ is IMHO out of date. Let’s think about craniofacial homeostasis; in the same way the body regulates blood pressure over a lifetime, for example. Teeth are only one component of the craniofacial system, which is subject to the ageing process like every other part of the body. Our aim perhaps ought to be to enhanced craniofacial homeostasis. For example, if someone is clinically obese and gets into shape thru improved exercise, diet and sleep, then unless they keep up that routine, the obesity will ‘relapse’. Those folks stay on a proactive maintenance program to prevent the weight coming back. Similarly, we need a proactive ‘retainer’. It’s a pink color. It’s called the tongue, and the maintenance program is invariably called ‘orofacial myology’ or myofunctional therapy, which targets the four craniofacial tissues viz. soft tissues (e.g the tongue), hard tissue (bone of the jaws), dental tissue (teeth) , and functional spaces (the upper airway). IMHO ‘orofacial myology’ or myofunctional therapy should not be an afterthought. Instead it needs to be planned prior to, during and post-treatment.

  19. Simon Wong says:

    We do a lot of robust RCT research on treatment planning. Clearly we care to know the truth.

    We do a lot of robust RCT research on mechanics. Clearly we care to know the truth.

    We do a lot of robust RCT research on phase 1 therapy. Clearly we care to know the truth.

    We do a lot of robust RCT research on phase 2 therapy. Clearly we care to know the trusty.

    We do lot of wishy washy research on phase 3 retention. Clearly we…….

    Ummm, perhaps we should?

  20. Noel Stimson says:

    The above bloggers Lysle Johnson, Sam and David Singh talk a lot of sense about how we should approach retention; however one important factor is so far absent from the debate. The cranium. The key to satisfactory retention does not rest with oral myo-function alone, crucial though that is; if the cranial and facial bones are not aligned correctly, there will always be some degree of structural mis-match between the jaws, which in turn will drive occlusal relapse if not addressed. It is a force that cannot be dealt with simply by straightening the teeth because that is only the symptom. The cause is shared between the oral musculature and the cranio-facial bones.
    One other factor is often missed; living bone has a small degree of flexibility, not only at the joints and sutures but within the bone itself. The bony sutures of the cranium must be free to flex and function, so it is unsurprising that the fixed retainers placed across the maxillary and mandibular midlines can ‘pop-off’ easily.
    You may see why I do not agree with your statement, Kevin, that “the PAR measured all the components of relapse”.

    The BOS guidelines state in effect that “life-long fixed retainers are the only means by which long-term orthodontic stability can be achieved”. Imagine an orthopaedic surgeon telling a patient that “I can fix your hip joint but you will need to use crutches for the rest of your life.”

    High time we started to address the causes of malocclusion and not just simply treat the symptom.

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