August 22, 2022

Are fixed retainers better than VFRs?

This post is another one about retainers. It follows closely on the heels of last week’s post in which I described the results of a five-year trial. This week’s paper is another 5-year follow-up that looks at the long-term stability of fixed and removable retainers. It is another excellent study.

It is great to see investigators publishing so many randomised trials about retainers. The present authors write that previous trials are starting to conclude that bonded retainers are more effective than VFRs. This may be particularly true for mandibular retention. They provided further evidence in this long-term study.

What did they ask?

They did the study to;

“Evaluate and compare the five year post treatment changes in the maxilla and mandible with two different retention protocols”.

What did they do?

They did a single centre two-arm randomised controlled trial with a 1:1 allocation.

The PICO was:

Participants:

Adolescents treated with upper and lower fixed appliances (MBT 0.022)

Intervention:

Upper VFR and lower fixed retainers.

Control;

Upper and lower VFRs

Outcome:

The primary outcome was Little’s Irregularity index. Secondary outcomes were other dental measurements and participants’ perceptions of their retainers.

They collected study casts at debonding (T1), after 6 months of retention (T2), after 18 months (T3), and after 5 years of retention (T4).

The clinicians asked the participants to wear their retainers full time for one week, then nightly only for a year. After one year, they reduced wear to every other night, and two years after debonding, they wore their retainers for 1-2 nights per week.

The fixed retainers were made from 0.8 hard ss wires bonded to the canines.

They carried out a sophisticated and relevant multivariate analysis. This included imputation of data for participants who did not complete the trial.

What did they find?

The authors reported a large amount of data. Therefore, I have decided to concentrate on what I felt were the most clinically relevant outcomes.

Firstly, the team randomised 104 patients into two groups of 52 participants. At the end of the study, 74 completed the trial. This was a dropout rate of 28%. Equal numbers of patients dropped out of each group. When they analysed the data, they used imputation techniques to obtain meaningful data for the dropouts. As a result, they did an intention to treat analysis for all the participants who started the trial.

These were the main findings:

  • There was a significant difference in the LII between the fixed retainers and the VFR group in the mandible at the end of the study. This was a median difference of 0.6mm.
  • Arch length decreased, intercanine width remained stable, but there was a significant decrease in the maxillary arch width of a median of 0.2mm.
  • The participants were satisfied with their retention regimes. However, when they looked at self-reported compliance, they found that 72% of all patients were not wearing their removable retainers at 5 years.
  • Finally, 7% of the fixed retainers failed.

The authors concluded.

“Anterior alignment in the mandible was more stable with a bonded retainer compared to a removable VFR after 5 years of retention”.

What did I think?

This was a nicely done RCT. Randomisation was well done in advance, and concealment was good. The team analysed and recorded the data blindly. They did a relevant statistical analysis, and the paper was clearly written. I thought it was nice to see such a well-done and reported trial.

This was another trial that suggested the advantages of bonded retainers. However, as I have discussed before, the main problem with bonded retainers is that we need to monitor them. When we consider the results of this trial, we have to appreciate that the amount of relapse is small. Importantly, we need to think about whether this was clinically significant. Only you can make this decision.

Final comments

My decision on the best retainer is still influenced by my clinical impression, and I will stick with VFRs. Nevertheless, the evidence of the superiority fixed retainers is mounting. I may change my mind as further trials are published.

There have been several good trials over the last couple of years and our evidence base is building nicely. Perhaps, Simon Littlewood (the Lord of retention) could take some time out from touring the World and update his team’s excellent Cochrane review on retainers? I would really look forward to this update.

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Have your say!

  1. If patients had been asked to wear VFR’s 5-6/7 instead of 1-2/7 the results most likely would have been different.
    They weren’t removing the bonded retainers for 5 days a week and then rebonding them.
    i.e. they are not comparing like for like in terms of number of hours of retention per week.

    VFR’s only work, in my non RCT opinion, if you were them most then 1-2 days a week.

    • I was thinking the same before I read your comment, Dr. Caves.
      Taking Vivera retainers as an example, the recommended protocol is full time for the first three months, and then only at night for at least another 12 months. That’s much more frequent compared to the 1-week full time in the trial.

  2. Kevin
    i have to disagree with your conclusion in continuing with VFRs, when the current study shows 72% were not wearing them (ie they had ‘failed’), vs 7% of fixed had ‘failed’
    To me that is overwhelming evidence that fixed are better then VFM!

    I am still of the opinion that ‘dual’ retention (fixed & VFR) has to be the best overall plan

  3. Congratulations on another excellent blog Kevin – The Lord of the Orthodontic Blog. I agree this is a very interesting trial that adds more to our knowledge about the vital topic of retention. What is becoming clear is that all approaches to retention have different advantages & disadvantages, & the implications of these need to be considered on an individual basis for each patient we are treating.
    You will be very pleased to hear that we are finalising the latter stages of the update to the Cochrane review on retention. This time we are working with an excellent team from Spain, led by Conchita Martin. We have over 40 RCTs included in this retention review, so we hope it will make this update the most useful retention Cochrane review yet. I’d love to write more…but I can’t right now…you won’t be surprised to hear that I am away travelling; this time in spectacular Barcelona. Keep up the great work with the blog – always a great read & relevant to all of us involved in clinical orthodontics.

  4. Kevin,
    I have to agree with Dr. Hobson. A week ago my good friend and orthodontic colleague, Dr. Doug Durbin passed. Doug had an article published in the JCO in 2001…
    https://www.jco-online.com/archive/2001/12/723-relapse-and-the-need-for-permanent-fixed-retention/
    As unscientific as it may have been, it illustrates what I have seen for the last 45 years as an orthodontist.

    17.2% of my Invisalign cases are retreatments. Having treated just over 12K Invisalign cases, that represents 2k + because of post-retention movement. We actively market to the retreatment population.
    Of course ‘Dual’ retention is not perfect, but it sure does a better job in my practice than expecting a patient to wear VFR’s for life-time.

  5. The thing I don’t understand is why are we only concerned w lower incisor crowding? Arch length is collapsing, the posterior bite is deepening and the COS is deepening. No ortho case is stable without changing the reason the teeth became crooked in the first place. If the business is to just straighten teeth then obviously a fixed retainer that stays put is superior. But let’s not act like the total case is stable… straight lower anteriors or not.

  6. For me there remains a question of ‘is dual retention the best retention”, it would be great to see a 3 arm study with dual retention investigated with the same number of independent variables as per this study.

  7. I’ve done dual retention for 20 years. We have a very small rate of repairs for fixed rets. I don’t place twisted wires.

    But the vast majority of vfr users discontinue usage early, leaving the bonded devices as the sole devices.

    The vast majority of bonded retainers do their job well with little trouble. Bonded rets in my practice appear to have a high survival rate and allow o lying little increase in the Little Irregularity Index.

  8. LOL Kevin O’Brien those acronyms tho! Took me a minute! Here’s my beef with VFR’s and this research that wasn’t really accounted for in the research: Most docs make crappy in-house VFR. They don’t do it right and not with the right equipment. Those are so much MORE inferior than a properly made one, which isn’t bad in my experience . The issue is, that a consumer can’t tell if it is or isn’t properly made. Yes, they can do branded ones like Vivara but I hate to arbitrarily throw business to a branded company when it really isn’t needed. Also an 0.80 round wire bonded only on canines? Not the best LBR IMPO. I like the omega helix ones or the ones that have a composite mesh pad on each tooth, or BOTH if possible!

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