An occasionally irregular blog about orthodontics

Self ligation: more nails in the coffin?

Self ligation:  more nails in the coffin?

Self ligation: More nails in the Coffin or “oh no: he is going on about self ligation again”!

Those of you who follow the blog closely will have noticed that I have not posted for a while as I’ve been on holiday. I am now back after a good break  and I have returned to write about our “old friend” self ligation. This is because two papers have recently been published in the free to access journal, the Angle Orthodontist. This also follows on from this post, which created a fair amount of controversy.

A multicentre randomised controlled trial to compare the self ligating bracket with a conventional brackets in the UK population:

Part one treatment efficiency DOI: 10.2319/112414837.1

Part two pain. DOI: 10.2319/112414-838.1

Lian O’Dywer; Simon J. Littlewood; Shahla Rahman; R. James Spencer; Sophy K. Barber; Joanne S. Russell.

The North of England

Angle Orthodontist epub ahead of print:

These two papers reported the same study; One was concerned with treatment efficiency and the other with pain perception. My initial feeling is that it is a shame that this data was not presented as one paper covering the two outcomes. This is because the current presentation leads to repetition in the text. As a result, I will combine my description of the two papers in one blog post.

What did they ask?

The authors carried out a randomised trial that aimed to determine whether using self ligating bracket system increased the efficiency of treatment and reduced patient pain. Those of you who are familiar with self ligation will know that these are some of the claims made to promote this type of orthodontic appliance.

The study team on a "good day out" in the North of England

The study team on a “good day out” in the North of England

The study was a randomised trial that was carried out in the North of England. As an aside, this is the best part of England (I live there), even though some people think that it is a little bleak up North.







They randomly allocated 138 patients to receive treatment either with a Smart Clip (self ligating) or Victory (conventional. All patients were treated by two specialty trainee operators who were closely supervised. They followed the manufacturers wire sequence.

Randomisation concealment and blinding were good.

The sample size was developed using data on the primary outcome of treatment efficiency. Importantly, they did not carry out an additional sample size calculation for pain perception; I will return to this later. They collected data on the number of appointments, treatment duration, bond failures and pain using a questionnaire. The statistical analysis was appropriate, however, I wondered if they should have carried out multivariate analysis on the treatment efficiency data.

What did they find?

As with most randomised trials of self ligation, they found no difference between self ligating and conventional brackets. This table contains the data for efficiency and pain. I have not included bond failure, because its not very interesting.

 Smart clipVictoryDifference (95% CI)
Treatment time (months) (-1.4,2.7)
Number of visits19.920.30.4 (-1.4,2.2)

What did I think?

I thought that this was an interesting study that was well carried out and reported. However, I do have some concerns. These were:

  1. The group who were allocated self ligating brackets were on average one year older that the conventional bracket group.
  2. They used to questionnaire to measure pain that had not been validated
  3. They powered the study on treatment efficiency data only. Unfortunately, they did not carry out a similar power calculation for pain. This means that they had sufficient power to detect a difference in treatment efficiency but not for pain.

The authors also raised these issues in their discussion, which I thought was very balanced.

This means that we, as readers, need to consider whether these issues have influenced the results. My feeling is that we can be more confident about the findings for efficiency than we can for pain. Nevertheless, this study does add information that suggests, again, there are no or minimal advantages to the use of self ligating brackets..

I think it is very interesting to look back on the development and promotion of these systems, including the introduction of new treatment paradigms that fitted the theory behind the bracket. We also know that this was followed by claims being made for their advantages both in the advertising literature and by Key Opinion Leaders. We now know that several years following all the excitement that was generated by these claims, several trials have been published that now show the claims were “overoptimistic”.

I also find it interesting that, as far as I know, none of the key opinion leaders have accepted these findings and stated that they were “over keen” on the product.

Finally we need to consider if harm has been caused. At present, there is no real evidence of harm to patients. however, only time will tell with the potential for relapse following the adoption of an extraction policy.

It is also clear to me that self-ligation treatment was promoted and provided at additional costs to patients and their parents. We, therefore, must consider if patients and parents have been the victims of the over promotion of self ligation.  This, again, is for you to decide.

Would any of the Key Opinion Leaders or those who still promote self-ligation on their websites like to comment? It is easy just click on the comments below!
O’Dywer, L., Littlewood, S., Rahman, S., Spencer, R., Barber, S., & Russell, J. (2015). A multi-center randomized controlled trial to compare a self-ligating bracket with a conventional bracket in a UK population:

The Angle Orthodontist DOI: 10.2319/112414837.1

Rahman, S., Spencer, R., Littlewood, S., O’Dywer, L., Barber, S., & Russell, J. (2015). A multicenter randomized controlled trial to compare a self-ligating bracket with a conventional bracket in a UK population:

The Angle Orthodontist DOI: 10.2319/112414-838.1

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  1. Andrew Sonis says:

    Benefit to the patient or benefit to the orthodontist? I believe most who adopt self-ligation do so to decrease chair time by decreasing time taken to ligate new wires. As been pointed out now by several studies, little benefit to the patient.

    • Kevin O'Brien says:

      Hi Andrew, Yes I think you are right but there have been no studies looking at a reduction in surgery time. it would be really interesting to see a study carried out prospectively.

      best wishes: Kevin

  2. Simon J Littlewood says:

    Thanks for covering the results of our self-ligating RCT. This project was started at a time when self-ligating brackets were the most talked about aspect of orthodontics. It is interesting that the results are very similar to other randomised controlled trials in this area.
    I think the criticisms raised by Kevin in this blog are fair and worth commenting briefly on. Despite the use of appropriate randomisation, the average age of the self-ligating brackets patients was 1 year older – the readers will need to decide if this would make any difference to the overall result (we think probably not). The comments about the questionnaire and sample size are fair observations, and means that the results for the pain outcome should perhaps be viewed with more caution, but we can be more confident about the results comparing the efficiency of the 2 types of brackets. We hope this RCT study adds, in some small way, to the body of evidence about self-ligating brackets.

  3. Klaus Barretto Lopes says:

    Dear Kevin,
    In my opinion, it is clear that the great advantage to use self-ligation brackets is the reduced time chair. For the orthodontist, this is important when a lot of patients are attended per day. For the patient, this is important to save time in their appointments. This is the information I provide my patients and some of them choose the self-ligation brackets for this reason. I believe this is a fair approach. What do you think about it?
    Thanks and best regards, Klaus

  4. Hi Kevin

    Thanks again for your blogs
    Was just reading our latest one earlier today.
    I know it’s not part of the story but I have tried many of the bracket systems over the years. In my experience because of the way in which the Smartclip system works, it seems to hurt patients more than other systems when changing the wires, especially steel wires. It doesn’t seem as painful when closing a clip as with the other systems as it does with removing the wire using those special pliers in this system. It was one of the reasons I stopped using it. I tried it for a while since the concept of having a clip instead of using ligatures for the clear Smartclip seemed to be a good one. In the end it wasn’t
    Just thought I would share that with you in the light of the fact that this bracket was used in this study

  5. Haris Khan says:

    Dear Kevin I believe more similar and strong evidence like above study will come in future. In self ligating brackets we just use manufacturer made fourth wall and pay a lot for this. As ligation done on conventional brackets is also reliable till next visit and orthodontist modify their ligation according to treatment stage and malocclusion so obviously we are not going to find any difference in treatment efficacy with bracket having same prescription and using same treatment mechanics. Time saving with SL brackets can be debatable.Though not a good level of evidence, one prospective study show SL are better.

    The point is after this evidence what orthodontist lost from tall claims of manufacturers and what manufacturers lost. Orthodontist lost a lot of money except from some commercial speakers who will still claim SL are the best. Manufacturers lost nothing. They sold something which doesn’t exist and they will keep on selling it as back on streets in Asia , Africa and Latin America, Kevin O Brien and RCTS have a impact factor less than 1 while commercial speakers and salesman have impact factor above 100!!!

    • Kevin O'Brien says:

      Thanks for your great comment about impact factor! I suppose that you are right we cannot really resist the sheer weight of advertising and key opinion leaders. The only way is to make sure that orthodontic are sufficiently educated in research so that they can evaluate the claims that are made by people.

  6. Rajendran Krishnan says:

    Dear Doctor Kevin,
    Thank you very much for this useful information. I was actually thinking to start on self ligation for my patients, but the question is whether this will benefit the patient in any ways as such. Since I’m used to the MBT I feel that its much comfortable to the patients. I also would like to know whether individual tooth movements such as derotation, distal/mesial inclination can be done with self ligation as it is done with MBT?

  7. sarvraj kohli says:

    Dear Dr. Kevin,
    Thanks once again for an exemplary critique on the supposed merits of SLB bracket systems. Several other investigations with pain perceived by patients and treatment efficiency too hold concurrent conclusions as the present study.
    The only perceived advantage being reduced chairside time; too seems to be over – hyped as a reduction of 5 mins per visit multiplied by approximately 18-24 visits assuming an average treatment span translates to roughly 90-120 minutes saved. Does saving one and half hours justify the additional cost of the appliance?
    As you once remarked earlier it’s upto the orthodontist to take an “informed” decision,I could not think when your statement was more apt.
    All the very best to you and your team ahead of the WFO 2015 @ London.
    Sincere regards.

  8. Dear Kevin,

    Thank you for the summary of the two part article. It is getting increasingly clear that there is no much difference between self ligating and conventional brackets at least in relation to time taken to complete the case and the amount of pain experienced during treatment. However Just to play devils advocate in this discussion, I myself have been using only the Damon system for the last 3 years before which I worked with the Victory series for over 7 years. Clinically these are the observations I have made with this specific bracket system
    – the play between the bracket and archwire is significant and this allows for certain cases of Cl 1 crowding to be aligned without untoward effects such as excessive proclination of upper / lower anteriors. Also a bit of expansion in the premolar area due to the archwire shape helps . Certain borderline surgical cases Cl 2 and Cl 3’s can be treated non extraction ( camouflage) due to this play using respective elastics

    – Absence of elastomeric modules helps to maintain better hygiene. I have noticed when I place some modules over the Damon braces ( some patients ask for it , for the sake of colours) at the next appointment the modules have disintegrated lost a bit of their colour and accumulated quite a bit of debris around them. This is something to definitely look into with conventional brackets.
    – wire changes is quite easy , opening the gates and removing the modules may take the same time , wire change same time, but closing the gates against placement of modules/lig ties is worth looking into with respect to time taken. Also I don’t need an assistant to hand me any modules.

    – expensive
    – problems with rotational control
    – problems during finishing. Insufficient torque expression, need to introduce torque in the archwire for nearly all cases, having said that I did a bit of wire bending in the finishing stages even with the victory series.

    I hope this helps and maybe would throw open a few areas for further research. Manufacturers would always throw their weight behind their products through advertising . At the end of the day it is just a normal conventional bracket with an additional gate, Would it really make such a big difference ? I think we all know the answer to that

    Thank you

  9. Hisham Badawi says:

    Dear Kevin,
    Thank you for your interesting and stimulating blogs. I read your blog with interest, read the papers and I agree with many of your conclusions. However I feel everyone (including the authors) seem to miss a very critical point, which I would like to get your opinion on.
    On examining table2 I notice that despite randomization, the conventional ligation group had disproportionately higher number of Class I cases 32% compared to the self-ligation group which had only 18%. Two thirds of the class I cases happen to be assigned to the conventional group
    I am wondering if you considered this in your assessment of the results. Do you think on average Class I cases have shorter treatment times compared to class II and III cases. If so do you think it is worth asking the authors about the treatment time for each type of malocclusion?

    • Kevin O'Brien says:

      Hi Hisham, this is a very good point and illustrates the difficulty of carrying out a trial of treatment done for several types of malocclusion. All the cases were done with extractions, so I think that we can assume that the amount of space closure was the same. But, you do make a good point. Perhaps, one of the authors would like to respond?

  10. Hello Kevin,
    Thanks for your considerable effort in putting these articles together and sharing them with us. I appreciate the format and the analysis. I recommend the residents I teach follow this blog to learn where myth are reality are often dissected.
    My one comment to add to the self-ligation discussion pertains to auxiliary staff. The definitive reason that I have used self ligation brackets for many years has been to level the ability from less experienced technician to more experienced technician to fully engage wires into the archwire slot. Prior to using SL brackets, the technicians with the most experience were able to more effectively engage the arch wires and subsequent appointments were scheduled without interruption in treatment progress. The less experienced technician, being timid and not fully engaging the archwire, especially early in treatment, would often chose to not fully engage, or not use steel ties for fear of breaking a bracket. This often resulted in patients being scheduled for new arch wires, only to discover teeth which were not fully engaged which leads to another appointment of “re-tying”. In the days when all patients were seen monthly, this may not seem to big a deal. In today’s orthodontic practices, often with 5 or more technicians assisting the orthodontist, the emphasis has switched completely. We try to see the patient the least number of times to gain the final result. This may be part of a different discussion for another time. Back to the point of SL brackets. With SL brackets, the gate is either closed, or it is not. The learning curve to train this is pretty low. This makes the new technician, with minimal training, on par with the more experienced technician when it comes to predictability of being able to progress to the next wire in a sequence of wires. Patients can be scheduled for 10-12 weeks out without concern that we will not be able to progress to the next wire due to a ‘partially’ ligated tooth. The end result is the consistency of the practice as a whole benefits tremendously. The quality of the treatment, as well as the scheduling, becomes much more consistent and is not dependent upon which technician was primarily working with the patient. This is not to imply that we never have a problem with a SL bracket opening, or a tooth not moving as predicted. However, the added cost of the braces is overcome by having fewer patient visits and more consistent outcomes. The key parameter in our office is not the total treatment time, but rather the total number of visits required to get from start to final outcome. The cost to our practice for an additional visit heavily outweighs the cost of SL appliances. I can’t tell you how frustrating it was to have an anterior tooth at the end of treatment unexpectedly suffer a slight rotation due to poor ligation in conjunction with good class II elastic wear. This rarely, if ever, happens in SL brackets – as long as the gate is closed.
    I have never bought into the myths related to SL brackets as far as teeth moving faster, or miraculous bone growth allowing super-sized archforms. Not surprising is that the manufacturer’s would never make this a major selling point because it doesn’t distinguish why one SL bracket would be superior to another. The benefit is gained just by having the consistency of self-ligation is shared by all SL brackets (assuming the gates don’t pop open unintentionally). What I have seen over the past 17 years is that we can schedule very consistently, seeing patients every 10 weeks, since we have eliminated re-tie appointments in our practice.
    This may not be reason enough for some to bear the additional cost of these appliances, but I think it is worth pointing out as another factor to consider.

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