Do bonded retainers really fail as much as the research suggests?
After my previous post about the high failure rates of bonded retainers in clinical trials, I contacted Simon Littlewood, an expert in retention and trials, to provide some insight on this issue. He has kindly shared a detailed explanation in this guest post.
Clinical experience v Research findings
Have you ever read research and thought, “That’s not my clinical experience”? That is something that certainly happens to me when reading research showing higher-than-expected failure rates of bonded retainers. And what makes it worse is that some of that research is from studies that I have been involved with. So, let’s look at the mystery behind bonded retainer failure rates…
Recent high-quality research discussed in this blog has shown that bonded retainers fail a lot more often than we would like to think. If the failure rates are as high as 30-40 %, surely it would make them impractical to use, with orthodontists overwhelmed with repairs, relapse, and really unhappy patients.
Why is the failure rate high?
Our immediate reaction is to presume that the research is flawed, yet on closer inspection, these studies are often of the highest quality: well-designed, prospective randomised controlled clinical trials. It’s worth considering why there is a disconnect between the high failure rates reported in these trials and our own clinical experience. I think a few things are going on here:
- Prospective research, in any medical or dental specialty, frequently produces less positive findings than retrospective research, which is based on looking back at records or clinicians’ recollections. It is human nature that we keep better records of treatments that go well, whereas patients whose treatment has been unsuccessful are often lost to follow-up. Prospective research results in more truthful outcomes, more accurately recording the problems and successes.
- When reviewing patients who are part of a bonded retainer trial, are we checking the retainers more carefully for any failures? In normal life, do we always notice bonded retainer failures? By their very nature, bonded retainers are difficult to see, so patients may not realise their retainer has a problem. Do we, as clinicians, always spot a problem with a bonded retainer during a cursory check-up? Look at this photo taken as part of one of the bonded retainer RCTs – only with careful checking by the researcher did they notice a wire fracture between the upper right lateral incisor and upper right permanent canine.
- Clinical expertise undoubtedly plays a major role in the success of bonded retainers. In fact, I would go as far as to say that the dexterity of the operator may be factor that is at least as important as the type of retainer, adhesive or bonding technique that is used. When interpreting research, the range and experience of the operators may play a role in the failure rates.
- The word “failure” is highly emotive, and I wonder if this is the correct term to use in bonded retainer research. Failure seems to imply some catastrophic result, meaning the whole treatment has been compromised. This, of course, is often not the case with bonded retainers. The commonest “failure” is the composite bond becoming detached from one tooth. If picked up early, no unwanted tooth movement usually occurs, and it is easily repaired in a few minutes. I wonder if our attitude to the research would be different if we described an incident like this as a ”minor problem” with the bonded retainer rather than a failure? Stating that 30% of patients had a “minor problem” with their retainer suddenly doesn’t sound so bad. Perhaps we should reserve “failure of bonded retainer” for situations with an adverse effect, such as noticeable relapse.
What do I think?
These are just a few possible reasons why the failure rates of bonded retainers in research may seem higher than we feel we experience clinically. But (and there is a big “but”) bonded retainers clearly aren’t perfect, and problems do occur more frequently than we like to believe. Every time we place a bonded retainer, we must make our patients aware of what problems can occur. We should also ensure the patient realises that these retainers need to be checked regularly. This could be done by the orthodontist or an appropriate dental care professional who is appropriately trained and remunerated for reviewing bonded retainers, not just in the short term but for as long as the retainer is in place.
In the meantime, let’s hope we continue to see more of these long-term, high-quality bonded retainer RCTs that help us identify ways of reducing the failure rates of our bonded retainers. Finally, I think there is one more area of retainer research that I hope we will see more of over the next few years, and that’s qualitative research. This explores patients’ expectations, motivations, aspirations and hopes for reducing post-treatment changes. I think this will help us focus on the best approach to bonded retainers from the patients’ perspective.
Simon Littlewood is Lead Consultant in the Orthodontic Department of Bradford Hospitals NHS Trust and a Registered Specialist in Orthodontics.
Simon Littlewood is Lead Consultant in the Orthodontic Department of Bradford Hospitals NHS Trust and a Registered Specialist in Orthodontics.
Thanks for your contribution on this topic. I often wonder why the rubber dam is not routinely used while placing fixed retainers. As this is an adhesive technique, we should consider applying evidence from other sister disciplines, which strongly support the use of the rubber dam to reduce moisture and improve bond strength.
Iacopo – this is a really good point and in fact this is something we also thought about at the University of Leeds in the UK. One of our postgraduates, Margaret Conway ran an interesting randomized controlled trial investigating actually what you are suggesting. The study qA entitled “Exploratory randomised control trial to determine if orthodontic bonded retainers should be placed using rubber dam – a pilot study”. It was never published, but stored as a masters as the University of Leeds. Interestingly, it showed no difference in failure rates between the 2 groups. Some people were disappointed that the rubber dam didn’t seem to offer a way of reducing failure rates, while others were relieved that the results failed to show we should all be placing rubber dam when using bonded retainers!
I my experience the reliance flexible chain fails/breaks 100 percent of the time
Do we really know the rate of bonded retainer failure? Perhaps patients often give up and don’t return, especially if they have had several bonded retainer repairs?
Danny – I think you may be correct. If patients fail to return for repairs it is difficult for us to know the true level of failure rate. It is one reason where prospective research, which aims to follow-up patients to monitor failure rates, often show higher failure rates. I wonder whether the advent of more sophisticated remote monitoring technology, which patients can utilise through software on their own smartphones, may allow an easier way to follow-up patients in the long-term?
The bonded retainers serve to maintain the correction of crowded anterior teeth. Bonded retainers in lower anterior teeth not only serve to prevent relapse of lower anterior crowding but also prevent late mandibular anterior crowding which is a physiological process. When these lower bonded retainers are kept for a long time, due to mesial migration of lower dentition may cause premature incisor contact leading to upper anterior spacing or worse, posterior positioning of mandibular condyles predisposing patients to TMJ problems.
Logically, bonded retainers should be removed after a specific time to allow natural settling and reposioning of teeth even if it means that there could be reoccurrance of some lower incisor crowding.
Nature always prevails at some point in time … Orthodontics is no exception…
perfect point to be considered
With bonded retainers i feel if it will fail generally occurs mostly in the first year or so as you are adjusting to your “new bite”. Afterwards it will mainly be a composite chip
Thanks for the post.
I am often curious about how long clinicians who place bonded retainers expect them to “work”? (not break, not move as a unit or to move teeth attached to the wire, not cause any additional chronic inflammation in the surrounding periodontium). Do we realistically expect them to never break? (even the most well educated specialist prosthodontists gluing in well-constructed crowns under rubber dam have an average 10-30 year survival rate – and the pros literature is replete with significant variables identified in long-term studies relating to failure; knee and hip replacements- highly mobile body parts- don’t last forever – high tech medical devices placed in high tech surgical theatres)
We are sometimes fortunate, and we may get decades or more time before a “minor problem”, sometimes not. I believe, the fact is that we simply do not know for any given individual the longevity of this artificial material we have attached to a living, functioning, highly variable patient. If we accept there is uncertainty- and pay attention to the high standard of research suggesting a 30% incidence of “minor problems”- , then we should cease being surprised when patients with relapse, adverse movements, breakages or calculus accumulation seek our help. It is inevitable. In a significantly high proportion of patients.
Solutions?
– if we still choose to glue wires, as well as vacuum-formed retainer protocol to protect the rest of the occlusion and alignment, why use the wire? (or schedule removal after an agreed period of “Edwards” remodeling).
– if we cant live without bonding wires, take responsibility and don’t send broken wires to our colleagues to repair – have we as a specialty determined who should maintain these “retainers” we placed? I welcome Dr Littlewood’s advice: “Every time we place a bonded retainer, we must make our patients aware of what problems can occur. We should also ensure the patient realizes that these retainers need to be checked regularly.”
(When I do this, patients usually welcome the vacuum-formed retainer alternative alone…I believe that timing is also key – these messages may ideally be delivered and discussed pre-treatment, not as a quick decision or worse, a routine protocol choice not agreed to by all fully informed patients and parents at “deband”.) Retention protocol is typically part of the treatment plan.
– start some research on “early” “minor problem” (failure) significant risk factors (design, operator experience, dam or no dam, wire/ composite / bond type, diet, age of patient, bone height, OH standard to suggest a few that may or may not be relevant) -so that we may target and prospectively manage this cohort. Do we know of any such research Dr Littlewood?
Lastly, I cant help but be amused by the bloggers who comment on their very high success rates, how they bump into patients decades later, who still have their bonded retainers in place. Heads up – this does not mean that tomorrow that wire wont experience a “minor problem”. …In fact, for that patient, the risk is now higher ; it does not mean their teeth are still aligned and healthy, and usually means that another practice will be removing that wire after you retire! 🙂
Thanks for the post. For years I try to convince our students and orthodontic community that the protocol should be refined with prior sandblasting rubberd, etc as well as to continue the search for other materials . A recent study we conducted revealed even the possibility of corrosion of the wires after long exposure. Let’s wait for new data to refine our protocols.
I am a fixed retainer advocate. Should the University of Washington studies on relapse following orthodontics never have been published, I might have considered removable retainers.
If removable retainers were released after 5 or 10 years and the teeth remained stable then orthodontics would be a relationship made in heaven.
I believe a good technician has a role to play in the success of fixed retainers.
Open bites caused by fixed retainers is something I have not seen much of in the literature, however it is another disappointment that occurs in my practice.
Fixed retainers have been frustrating, when failure occurs, the blame often on our shoulders. However the good long-term results makes the burden easier to bare.
I saw with surprise and suspicion the results of this study that says that retainers fall a lot, I believe that there is a huge bias there by the professionals who place them. I’ve been an orthodontist for 30 years and been a professor for 20 years. This doesn’t happen to me, on the contrary, my retainers last for years or decades without problems. Is time to reflection. Best wishes for all.
It sometimes surprises and disappoints me that clinicians are not more curious about their own clinical performance, assuming that what they are doing work well. In our multi-centre RCT comparing the clinical performance of composite v resin-modified glass ionomer cement for bonding brackets (https://www.sciencedirect.com/science/article/abs/pii/S0889540618308345) one secondary outcome was the proportion of first time bond failures (not including molars). The per site data ranged from 2% of brackets placed failing and 18% of patients bonded having at least one first time bond failure to 14% of brackets placed failing and 85% of patients bonded having at least one first time bond failure. The variability of the site related bond failures far outweighed the variability in the bond failures between the two materials. No clinician from any of the centres asked me about their own data.
our internal audits consistently find around 16% debonds and 0.5% total failure in the first year
BUT we have a very strict protocol:
Putty jig using multistrand (GAC Wildcat was best, but is no longer avaiable)
Abrade the enamel surface with a diamond bur (60+% increase in bond strength)
30sec etch with liquid phosphoric acid
wash, dry and isolate
3M MIP primer (do not cure at this stage)
bond using Kulzer venus Diamond flowable (high Vickers no and more abrasion resistance) extending as wide across the tooth surface as possible
cure
In the upper if patient is biting on DBR.. build up the bond as per Dahl on canines
Perhaps the high-polymer retainer is an alternative to the lingual retainer. It could be fracture-resistant due to its elastic structure and the radius and torque values it can exhibit.