May 22, 2017

The end of self-ligation: or is it?

The final nail in the self ligation coffin: or is it?

As readers of this blog will know I have posted about self ligation several times.  I have recently read a new study that looks at whether self-ligation results in a reduction in the duration of treatment, but does this add to knowledge?

I will start this post with a brief summary of what we know about self-ligation.  In many ways this is a classic story of discovery, followed by the release of a product and finally, testing that shows it is no better than any other product.  When self-ligation was re-discovered the manufacturers of the brackets made several claims for the benefits of the new technology.  These claims were supported by initial retrospective studies and then promoted by Key Opinion Leaders (who frequently did the studies).  Eventually, several years later, independent  invistigators carried out randomised trials. As we all know, these studies showed that there were no or very limited advantages of self-ligating brackets over conventional brackets.

The journals have published several trials that have looked at self-ligation. While these provided very useful information, they were directed at evaluations of the phases of a course of orthodontic treatment. For example, the rate of space closure, alignment and overbite reduction. To my knowledge, there has only been one trial that has evaluated the effect of self-ligation on total treatment time.

This team, from Greece, did this new study to find out if the use of  self-ligating brackets resulted in a reduction in treatment time.  The Journal of Orthodontics published this paper.


Eleftherios G. Kaklamanos et al

Journal of Orthodontics:

What did they do?

They ran a two group parallel randomised controlled trial with a 1:1 allocation. The PICO was

Participants: Patients with a Class I malocclusion with a space deficiency of up to 9mm

Intervention: Orthodontic treatment with Damon 3 brackets

Comparator: Orthodontic treatment with conventional brackets

Outcome:  Duration of treatment, Gingival Index Score. PAR score

One operator treated all the patients and saw them every 6-8 weeks.

They used a pre-prepared randomisation scheme and concealed the allocation in envelopes.  The operator enrolled the patients into the trial and then let them know their treatment allocation.

They could not blind the patient or the operator to treatment. But they collected and analysed the data blind.

They carried out a sample size calculation that was based on being able to detect a difference of 4 months based on a treatment time of 24 months for the treatment.

What did they find?

They randomised 22 patients to the two interventions (11 to each).  The patients did not have extractions as part of their treatment.

There were no differences between the groups at the start of treatment.  I have included the end of treatment data in this table.

No MOPS0.5 (0.28-0.7)0.6 (0.52-0.76)
MOPS1.1 (0.8-1.32)

The difference in treatment duration was 2.25 months (95% CI -0.40-4.9).  This was not statistically significant.  They concluded that the use of self-ligating brackets did not result in a reduction in treatment time.  Furthermore, there was no difference in the PAR scores between the interventions.

What did I think?

In their discussion they pointed out that in their sample size calculation they assumed that the average treatment duration would be 24 months. However, in their study they found that it was several months less than this estimate.  This may have resulted in a possible lack of power to detect a difference.

This becomes more relevant when we look at the 95% confidence intervals of the differences they detected. While this contains zero (suggesting no difference), we must consider that this was marginal. P was also 0.09 suggesting that there is a 9% probability of incorrectly accepting no difference exists. Finally, the 95% confidence intervals are rather wide, this suggests that there is uncertainty in their data.  I feel that these issues have happened because of the rather small sample size.

I cannot help thinking that this was a well carried out study, but I am concerned that  the sample size was too small. This leads me to wonder that if they had included a larger sample, there would have been a statistically significant difference.  As a result, my next step is to look at the effect size. This was 2.25 months.  We need to assess whether this is clinically significant and this is up to you to decide.

What can we conclude?

My interpretation of this data suggests that this study is probably underpowered. As a result, I am not too confident in the conclusions.

Nevertheless, before the “self ligators” get all excited, this does not change the current state of knowledge on self-ligation.  There is still an absence of evidence that this treatment is more effective than conventional brackets.

Related Posts

Have your say!

  1. Interesting to see that both the control and experimental groups patients were treated in less than the expected time – would be good to know how this was achieved ? Efficient priority booking of every appt, Hawthorne, patient engagement, clinician engagement, only treating these patients ? Would love to replicate this time frame in our DGH clinics so just interested and rather envious . Will read whole paper to see if I glean further info- thanks for posting

  2. leveling seems to be faster using speed braces and supercable wires in my office.
    Forward looking for hearing about new scientific data about self ligation.

  3. Hi Kevin,
    Thanks for another excellent blog anaylsis of a good piece of work. You are an indispensible resource in our profession. I love your blog.
    I find the discussion on self ligation interesting because it is so blatantly biased.

    For Example:
    1. Why do we talk about “nails in the coffin” of a popular device because it fails to reduce treatment months? If two brackets are equivalent in treatment time why does that make one of them fit for a coffin – or dead? Even if it cost more and had an odd name? This is perjorative nonsense!

    2 . Why are treatment months considered to be the only criterion of value? Aren’t there are other attributes of possible value? Like time saving, appearance, robustness, hygiene?
    An unbiased viewer would acknowledge other possible attributes needing evaluation.

    3. Why genealise about a whole class of products following a study concerning a single product -which is not an agreed exemplar of the product class? This is biased.

    There are situations where good a self ligating system actually makes or breaks the viability of treatment. Like lingual braces treatment. Like when you have no time in a schedule to remove and replace a wire for a loose bracket – but you simply have to. A device that saves time has value.

    • Hi Geoff, thanks for the comments. I suppose I am being a little too sarcastic about self ligating brackets, however, when you have two brackets and one is claimed to lead to several benefits and is advertised to patients, then I think that my sarcasm may be justified?

      your other point on other differences is good, but no study has shown any differences and again the issue is what we advertise to our patients and also charge them for the bracket that “makes no difference”. I hope that you see what I mean

      Best wishes: Kevin

  4. I think the most important thing here is not the time of treatment but the damage we can do expanding so much and leaving tooth without bone.

    • Just liked to ask, are there any articles that shows the expansion from Self Ligating causes thinning of the bone and gums? From what I heard, they can move the teeth with the gum.

  5. Good Evening Prof O@Brien,

    Thanks for your excellent blogs and summarising the Self ligation brackets does not necessarily to reduce the treatment time..

  6. I think this study is a comparison of Damon brackets vs twin brackets. Not all self ligating brackets are created equal. What may be true for Damon may not be the same for, say, Speed or any of the others. Also protocol for a self ligating bracket would be different than twin. Using the same protocol for both is wrong. Use a twin protocol for twins and self ligating protocol for the respective bracket. That could affect tx time differently. Has there been a good study comparing one self ligating bracket to another? I doubt they would all be equal. Damon is not the gold standard of self ligating to carry the banner of all self ligating brackets. As an aside, I’m surprised that even 15% less tx time with Damon is not statistically different.

  7. Very interesting, 9mm space deficiency (per arch I presume) and treating them all non extraction, and, I presume, without adjunctive expanders or class 2 correctors.

    I confess I live in a different world!

  8. I feel that many of the self-ligation studies have been poorly conceived thus creating inadequate findings and results. I would like to refer you and your readers to two studies that demonstrate significant time savings in: Treatment Time, Clinical Chair Time, and the Number of Visits required to complete treatment. The first study was titled “Clinical Effectiveness and Efficiency of Customized vs Conventional Readjusted Bracket Systems” by Weber, Koroluk, Phillips, Nguyen and Proffit. This article appeared in the April issue of the Journal of Clinical Orthodontics in 2013. To summarize their findings, Treatment Time went from a mean of 23 months for conventional brackets to 15 months with the Insignia bracket system. Scheduled Appointments went from a mean of 18 visits with Conventional Brackets to 11 appointments with Insignia.
    The second study was performed by myself, Dr. Jerry Clark, and appeared as a White Paper Report entitled, “Increasing Practice Efficiency and Profitability Utilizing InOvation Self-ligating Brackets. The study was a large one including 355 patients – 114 treated with InOvation brackets and 241 patients treated with traditional edgewise brackets. My findings were very similar to the above mentioned study. The Treatment Time went from an average of 24 months to 20 months, Chair Time was reduced by a full 3 hours, and the Number of Visits was reduced from 16 visits to 10 visits to complete the cases. This article can by downloaded from the Dentsply Sirona website by clicking on Orthodontics and then clicking on Resource Material and looking for the above mentioned White Paper Report. In my opinion Self-ligation is far from dead, in fact brackets are becoming more efficient and effective, especially since the introduction of the new InOvation X bracket.

  9. I love this website, thanks for taking the time to write and share such valuable info. I’m a sales rep, 24 years of experience and the industries leading sales rep in self ligation. These studies can be misleading. There are many advantages to self ligation, to claim to save treatment time is not one that any doctor will claim. And saving 2 months on a 14 month average is significant. This number seems fast, cases done in one year on average? Specialists can use anything to straighten teeth. Twin or Self Ligating no matter, the doctors are talented in this field. The important issue is make sure you take your family to see the specialist. This is where you save treatment time. Marketing plays a factor is the business, manufacturing companies also deliver on wants and needs of the specialist. This is how self ligation came about. What should be studied is hygiene and finishing. Numbers of visits and length of those visits are factors. Less friction is a benefit to both the patient and the practice, for many reasons. The claims towards bone growth on the mandible have never been substantial and one of your articles explains why in great detail. Self ligation was designed on two principals, saving time and reducing the work chair side and mostly for the patient. Sure color ties are fun, they are also nasty hygiene nightmares and need frequent replacing, they stain easy and bad breath is a guarantee. Treatment mechanics a SL bracket can offer advantages, tooth alignment is much faster. Some SL systems can slow you down later in treatment, finishing is a large part of treatment, detailing cases comes easier with certain systems. The one system noted in the article is the most challenging when it comes to finishing. To conduct a study on SL advantages vs twin you have to use more than one system to get a fair result. This study uses only one manufacturer making the study incomplete. Stack the IOR or IOX bracket against any other bracket system and the results would be strongly in favor of SL. Saving treatment time while interesting is not the major factor when using SL. The study should be on other areas that are more important, efficiencies. Finishing and torque control are the main areas, hygiene and comfort are also just as important. Less wire bending, that has always been the goal, ease of placement. This is what really matters and this is how the manufacturing companies should position SL systems.

Leave a Reply

Your email address will not be published. Required fields are marked *