November 25, 2019

Are fixed or removable retainers better?

Retention is one of the great mysteries of orthodontic treatment. Generally, we do not really know which retention regime is effective. Here is another trial that may help us decide.

Some of the most popular posts in my blog have been about retention.  It appears that there are little differences in the overall effectiveness of types of retainer. However, clinical reports may suggest that when a fixed retainer fails, there is a risk of significant problems. Finally, it does not seem to matter whether our patients wear their retainers full or part-time.  I was, therefore, interested to see this new randomised controlled trial. It certainly adds to the body of evidence that is building on retention.

What did they ask?

This was the first of several papers from a large randomised trial. In this paper, they asked:

“Are there any differences in retention over 18 months between vacuum-formed or fixed retainers”?

What did they do?

They ran a single centre, two-armed parallel-group randomised controlled trial. Participants were randomly allocated retention with a fixed or vacuum formed retainer. They collected data at 6 and 18 months after debond.  The PICO was:

Participants: Orthodontic patients treated with fixed appliances in one clinic

Intervention: Vacuum-formed retainer. They were instructed to wear this nights only. In the maxilla, the retainer covered all the teeth. In the mandible, it only covered from the first premolar to the first premolar.

Comparison: Fixed wire retainer bonded to the mandibular canines only. Upper VFR.

Outcome: Post-treatment change measured from study casts taken at 6 and 18 months of retention.

They did a precise sample size calculation based upon detecting a difference of 1.0mm relapse between the groups. They used pre-prepared block randomisation, good allocation concealment in sealed envelopes. The data were analysed blind.

They recorded post-treatment change in overbite, overjet, arch length, intercanine width and Little’s Irregularity index. These were recorded from 3D models.

Finally, they did an Intention to Treat analysis. This made sure that data were recorded and analysed from all participants regardless of the outcome or co-operation.  This is essential in a trial to ensure that the effect of the interventions are accurately recorded,

What did they find?

They randomised 104 patients into the two arms of the trial.  There were no differences between the groups at the start of treatment.  In the fixed retainer group, 33 patients had extractions, and in the vacuum formed retainer group, 23 were treated with extractions.

At the end of the 18 months, 46 of the VFR group and 49 of the bonded retainer patients remained in the study.

They presented a large amount of data, and I do not have the space to go through it all. I shall also only discuss the 18-month data. In summary, they showed that there were no statistically significant differences between the interventions for most of the variables that they measured.

Relapse occurred mostly during the first six months of retention.

When I looked at the Little’s Index data, this showed minimal relapse that was not clinically significant (VFR=0.52, Bonded =0.45).

Their main conclusion was:

“Vacuum formed and bonded retainers were equally effective at 18 months after debond”.

The relapse was not of clinical significance.

What did I think?

This was a nicely done and reported trial. It was interesting to see that the results were similar to other studies. This suggests that both types of retainer are equally effective.  Some operators point out that removable appliances rely on co-operation, and we do not really know how long our patients wear their retainers for. However, this reflects the “real world” nature of orthodontic treatment. Importantly, we are measuring the effects of asking a patient to wear a retainer again reflecting clinical practice.

It was also important to find that they asked the patients to wear their removable retainers at nighttime only.  This certainly reduces the burden of care or more traditional full-time retainer advice.

Clinical effects of this and other studies

I have thought about how this study may influence clinical practice. Ideally, we want to fit retainers that are effective and do not do harm. Furthermore, we do not merely want to delegate retainer management to the general practitioner. As a result, I cannot help thinking that the results of this and other studies support the use of VFRs over bonded retainers.  Let’s have a discussion about this?

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Have your say!

  1. Interesting result, but the bonded retainer was bonded mandibular canines only. Nothing in the upper arch.

    Would have been more interesting if the bonded retainers were bonded from canine to canine in both arches and that these were compared with full VFRs.

    Many orthodontists use bonded upper and lower retainers with upper and lower VFRs. Perhaps a third comparison.

    Hard to really draw a conclusion when the retainer options were so limited.

  2. It is my experience that often, patients do not wear the removable appliance.
    Therefore I almost always opt for a bonded retainer in the lower and a removable appliance in the upper jaw.

    Even then I get a lot of questions by patients why they cannot have a bonded retainer in the upper jaw.
    I prefer a retainer that holds the width of the upper jaw, so I put a vacuum formed one in the upper jaw.

  3. The ideal has to be ‘dual retention’ – ie both fixed and vacuum and telling patients retention is for life

    In practice (NHS makes us choose one retainer for the patient) we routinely use fixed DBR bonded 3-3 (0.0175 wildcat) in 90% of patients. Bonding 1200+ DBRs/year.
    Our practice audits over the past 10 years consistently find that problems arise within 3 months :16% having a problem in that initial 3mth period, dropping to 6% having problems in 6mths and 1% by 12mths. Replacement failure being only 0.2% over the 12 mth period. So our retention protocol is review 3/12 from debond then a further 9 months (12mth from debond).
    Our failure with VFM is almost double that of DBRs at 32% by 6mths, mainly due to patients loosing/forgetting to wear and we have used the “wear 24hrs, then night only wear” protocol for VFM for several years to try and improve compliance

    IMHO having read the evidence (we desperately need some long term 10+ year studies), backed by our own audits it is fixed over VFM every time

    As a related comment; when I ask a group of Orthodontists if they have had ortho treatment and what type of retainer they have? 95%+ have fixed… now, i know it’s not evidence, but if we and our colleagues are voting with their feet and choosing DBRs……

    ps my own DBR is in its 27th year and celebrates it birthday every September

    • Ross, how long do you recall your patients for a retainer check? Do you ask the patient ‘s GP to monitor for breakage, posterior tooth movement, other problems with referral back to you?
      Thank you.

      • Barry
        we monitor year 1 for NHS ; 2 year for private then ask GDP to take on monitoring. We have vids on our website on how to repair DBRs (it is only acid etch bonding) … and essix only needs an impression
        monitoring and repair is not difficult and the skills required, are held by all dentists. Only needs our intervention if relapse occurs

    • Ross,
      Do you not have issues with twisted/multistranded wire retainers unraveling causing unwanted root torque as time goes by?

  4. It says in “Interventions” that they were asked to wear their VFR’s Full time yet in the discussion it says they were asked to wear them night time only? Which is it as that could make a difference to the outcome.

  5. I live in a small town in Maine and I’ve been here for 40 years. I’m a big believer in fixed lower 3-3 bonded only to the canines. That is my only choice for normal lower fixed retention unless the patient specifically requests no fixed retention. I frequently meet adult patients around town who introduce themselves and ask if I remember them. I always look at their teeth hoping I’ll be pleased with what I see. Invariably, those that have a fixed lower retainer, have a very nice long term result. I’m talking long term like 10-20 yrs long term. I congratulate them on their long term result and the fact that the fixed retainer is still there. Now I do a lot of fixed retainers but I’ve never met a long term success patient still wearing a VF retainer long term. Even though this research paper says there is no difference after 18 months; from my empirical evidence around town, there is a difference over 18 years or thereabouts.

  6. With fixed retainers, the doctor continues to own the appliance and has the responsibility for it. The longer I practice the more certainity I have that Dr. Jack Sheridan had the right idea. He always told the patient and the parent. “I am the creator of your smile. I am not the guarantor of it. That responsibility belongs to you.” At some point the patient needs to understand and participate in this endeavor’s partnership.

    Larry White, Dallas, TX

  7. One additional comment: For those patients who started tx without any individual kind of upper arch problem like a midline diastema, once the upper front teeth settle against the lower front teeth, the fixed lower retainer is, in fact, serving to keep both arches aligned and stable long term.

  8. ‘set and forget’, doesnt work for any man made thing. Retention success requires maintenance and repair. Bonded upper and lower plus VFR over the top for once a week ‘try-in’ is my way. If minor unseat of VFR is detected we remake immediately and multiple times if needed. If bonded breaks there is a backup and patient expects to come for repair and pay. Just like all their other posessions. Effective life long retention come from the right effort and attitude.

  9. Agree here.
    For me, I have an upper 7 to 7 wrap around and a lower spring aligner. Both are celebrating their 25th birthday and have never needed adjustment! A well made, passive DBR is an awesome appliance when paired with a patient with great OH. Here in the US, a DBR is a liability, though if caries or perio issues arise.

  10. Vacuum formed on lower first premolar to first premolar…. Is that a thing?

    Swords Ortho

  11. The study looks at the results for 18 months which is short term. In the lower, relapse happens over a period of years especially when treatment is completed in late adolescence. In my humble opinion. although encouraging, the results cannot make a change in practice especially for the lower anteriors that are notoriously hard to retain.

  12. Hi,
    We compared Essix and Hawley retainers in our study and found similar results after two years of retention period. We concluded that the retention characteristics of both Essix and Hawley retainers are similar (Korean J Orthod 2012;42(5):255-262).
    This Recent study concluded that the vacuum formed and bonded retainers were equally effective at 18 months after debond.
    I think the decision in choosing the type of retainer depends on specific conditions of the case before treatment and the clinical experience of the orthodontist.

    Hasan Babacan

  13. To a certain extent, we let our patients chose what sort of retention they would like. I want patients to have retainers that they like. In certain situations, I dictate what will work best. I educate them on pros and cons and let them chose. Then they have ownership.

  14. For deep bite tendency cases I prefer a NTI splint as the lower retainer.
    For open bite tendency cases I use Hawleys.
    For lower crowding cases where teeth were advanced I prefer a lower bonded 3-3…especially if growth remains.
    Who trusts patients to be compliant?
    The idea that “one size fits all” is perilous…

    The study means nothing to me,

  15. I have for many years made vacuum formed upper retainers and for adolescents a bonded lower .032″ TMA wire bonded to the canines and centrals. If an adult requests a bonded lower retainer then I’ll make it for them. For a time, I only did upper and lower vacuum formed retainers because I had an adult patient swallow their bonded lower 3-3 retainer. That put me off the bonded retainers for a while. Something interested just happened to me. I had a female teenager request a maxillary Hawley retainer. Of course I asked why. She replied that her friend has one and it was “cute” Her mom paid for her to have this fashion statement while I’m beating my head against the wall.

  16. Thanks for sharing this great blog prof
    I am wondering:
    Can we generalize this outcome to the hawley retainers to compare them with fixed ones, or is there another study that made a comparison between hawley retainers and fixed ones?

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