May 13, 2014

Self Ligation: Another nail in the coffin?

Self Ligation: Another nail in the coffin?

In this blog I am going to review a paper from the most recent edition of the AJO-DDO. This is another trial of self-ligating brackets that reveals there are no advantages to using these brackets. This is contrary to the claims made by the manufacturers and on many orthodontist websites.

 Comparative assessment of alignment efficiency and space closure of active and passive self-ligating vs conventional appliances in adolescents: A single center RCT

Songra et al. AJO-DDO 2014; 145:569-78


This was a study carried out in Bristol, UK. This is also the home of Banksy the graffiti artist and I have used some of his work to illustrate this and other blogs.

This study was concerned with evaluating the effectiveness of two self-ligating brackets and a conventional bracket in terms of time taken to complete alignment and extraction space closure. This was a well reported and carried out study.

 What did they do?

They randomly allocated 110 orthodontic patients to receive treatment with either Damon 3MX (self ligating), In-Ovation (self ligating) and Omni (conventional) brackets.

Sequence generation, allocation and blinding of data collection were all good. They used the same archwire sequence for all patients. They also took impressions of the teeth at the start of treatment and every 12 weeks until the conclusion of the study. They measured the amount of incisor alignment using Little’s Index by a blinded operator. They also measure the time to space closure.

The data analysis and presentation was relevant and they used complex linear mixed models to analyse the data and took several confounders into account.

 What did they find?

When they measured the time to alignment, they found that the conventional bracket was more effective than the self-ligating brackets. This was clinically significant and the mean time to alignment with the conventional bracket was 251 days, compared to 422 and 399 days for the Damon and In-Ovation brackets. There were no differences in space closure.

Their discussion was a very balanced evaluation of their findings. They pointed out that when the results of this study they reviewed them in the light of other trials, it is now very clear that there are no advantages to be gained by using self-ligating brackets.

 What did I think?

ThinkingThis was another good trial and it is interesting to see that the evidence now overwhelmingly suggests that there are no advantages to using self-ligating brackets.

This has made me reflect, again, and wonder why we as a profession forgot our scientific grounding and adopted a method of treatment on the “evidence” presented by advocates, gurus and marketing. I have discussed this in more detail in this blog (In the land of no evidence, is the Salesman King?). There is no doubt that I shall revisit this theme in the future to continue to remind us that we should wait for evidence before adopting new techniques, philosophies or paradigms.

It is also important for us to consider that while our specialty appears to have been “taken in” there is now really no excuse for us to continue to advertise these claims about self-ligation to our patients on our websites. I shall soon post a blog containing the websites of the UK based orthodontists who are making the most extreme claims. This may be interesting, so watch this space!

Songra, G., Clover, M., Atack, N., Ewings, P., Sherriff, M., Sandy, J., & Ireland, A. (2014). Comparative assessment of alignment efficiency and space closure of active and passive self-ligating vs conventional appliances in adolescents: A single-center randomized controlled trial American Journal of Orthodontics and Dentofacial Orthopedics, 145 (5), 569-578 DOI: 10.1016/j.ajodo.2013.12.024

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Have your say!

  1. Yes it was a very interesting paper, hmm think I need to check the wording on my website to avoid naming and shaming!

    I am a user of a popular self ligating bracket (Damon) and have used it for years. I initially was “excited” by the claims, but after all this time (and evidence) there doesn’t really seem to be any difference in my hands. The one thing that I cling to is the comfort that the modules/o-rings don’t fall off and loose control of the tooth. Helps me sleep at night……….

  2. Readers of the Journal of Orthodontics might recall a rather good editorial in June 2010 about being cautious when people propose ideas or theories without backing these up with evidence.

    From idea to genuine progress
    J. Orthod. June 2010 37:75.

  3. I have found the same thing, but I still like their convenience and shortened appointments as I like to use steel ligatures to tie conventional brackets. I learned the hard way not to make any claims about them years ago.

  4. I sympathise with your frustration on the continued misapprehension that self ligation means faster treatment. I have been using self-ligating brackets on most of my patients for 10 years. It was subjectively evident after a couple of years that Self-ligating appliances were no faster at treating cases – circa 2005. A good retrospective study not picked up in UK was Hamiliton R et al. Aust Orthod J 2008; 24; 102-109 . followed of course a couple of systematic reviews since then.

    That said I feel your conclusion “.. there are no advantages to using self-ligating brackets. ” is a little harsh and perhaps was intended to be restricted primarily to speed of treatment. I shall try to list a few minor advantages that I have found with using self ligating appliances.
    1. Because of the secure ligation, flexible arch wires remain active for longer periods and can be allowed to fully express themselves. This reduces the frequency of need for archwire changes or re-ligation. In short by allowing longer intervals between appointments and using fewer arch wires I was able to treat extraction cases on average with 2 less appointments than with conventional ligation systems. Orthodontic update 2012; 5.1; 15-19. The financial implications of 2 less appointments per patient are an obvious. The overall treatment time is the same or marginally extended.

    2. N. Harradine Clin Orthod Res 2001; 4(4); 220-227 has shown that it is fractional quicker changing archwires with a self-ligating appliance.
    I don’t think anybody disputes this but of course it is of little practical advantage. For the operator it “feels” slightly easier and more convenient changing arch wires thus provokes a loyalty to stay with self-ligating systems. Nigel Harradine drew a parallel with the “feel good” majority use of shiny bright (more expensive) nickel titanium arch wires rather than the just as effective twist flex cheap stainless steel wires.
    3. The good appearance, (despite the anodised metal clip), of ceramic Innovation C appliances are well accepted by patients. The avoidance of the need for clear or white elastic modules which inevitably stained, is a big practical everyday plus for labial appliances.
    4. Unproved so far, there is my theory that self ligating appliances are better at anchorage preservation. By way of simplified explanation consider that the force needed to retract a canine be divided into 2 factors. The first factor is force Y needed to overcome frictional resistance in the wire/bracket system. The second factor X is the force needed to cause the tooth to move through the bone. Total force Y + X is equal to the strain on anchorage units.
    A multitude of laboratory studies have shown greatly reduced frictional resistance with self ligation (sl) systems compared to conventional (c) ligation. Force Ysl is substantially less than Yc . Theoretically (Ysl + X) puts less strain on anchorage than (Yc + X) for the same amount of canine retraction. Whether this can be borne out in practice is open to a research project.
    I very much hope that despite the damage done by misleading advertising, that self-ligating appliances remain as part of our orthodontic inventory even with a more realistic appraisal of their advantages and disadvantages.

    • Peter,

      I would like to reply to a couple of your observations.

      I agree that chairside time is reduced with self-ligating brackets as long as they open properly. You only need one obstinate bracket that will not open during a busy clinic and all previous gains are lost.

      Much has been made about the reduced levels of friction with self-ligating bracket, which is undoubtedly true; however friction is probably not a mechanical cause of slow tooth movement. Binding is much more important and this phenomenon is about the same in conventional and self-ligating systems (for an excellent review of this see Burrow 2009 – Friction and resistance to sliding in orthodontics:A critical review. Am J Orthod Dentofacial Orthop 2009;135:442-7). If friction was an important element in tooth movement you would only need to increase the force in a conventional system to OVERCOME the effects of friction i.e. the net force stimulating a biological response in the periodontal ligament = the force of the archwire/space closing spring or elastic – force required to overcome friction. In theory you should reduce your overall force level in a self-ligating system. If you do not reduce your force levels, because less force is dissipated overcoming the effect of friction, even more force will be acting on the periodontal ligament/anchorage unit in a self-ligating system than in a conventional system. I hope this makes sense?

      Of course all this ignores the fact that the we are dealing with biological systems (patients) with varying cellular responses to the same force.

      Kind regards,


  5. This is an interesting discussion on this posting and everyone is making good points. When self ligation was becoming popular I started using Damon brackets and I thought that they were great because of their ease of use and I really liked not using modules. From the point of view of supervising specialist trainees they were also great because they had to fully engage the wires. Now that the research has been published and we accept that they do not result in reduced treatment times it does not mean that we need to stop using them, because this is an operator choice and they have many good points. We can draw an analogy to the use of NiTi wires. There is minimal evidence that supports their use in terms of treatment time, but we find it easy to use these wires and so we all use them. If we accept that self ligation does not lead to faster treatment etc and they are just a good neat bracket that avoids the use of modules, that would be enough for me!

  6. I’m glad you brought this paper up, I think the flaw in this article is that they adjusted the conventionals every 6 weeks and the self-ligating every 12 weeks. In my opinion, it would have been a lot more interesting to see the results if they saw all groups equally every 8 weeks.

    I would like to see a study comparing self ligating v conventional where the whole self ligating mantra is followed, such as early class II’s and tieing in very displaced teeth with eyelets in self ligating instead of working into a round steel and running push coil etc.

    I am still on the fence with self-ligating, I don’t feel the ideal self ligating bracket exists, the passive self ligating slot sizes are oversized and I feel the active clip loses its force when its really needed.

  7. We just reviewed this paper in our journal club today. I agree with Zaid, the groups weren’t treated equally throughout the trial and so this could be the reason for the overall difference in initial alignment the paper found. They stated the reason for this was ‘manufactures instructions’ dictate(d) longer recall times (12 wks) for the self-ligating bracket systems. Conventional bracket (CB) patients ‘needed’ to be seen every 6 weeks due to the degradation of the O-ring. It is also a little unclear when the CB archwire change occurred. The self ligating groups could only move up an a/w when all ‘clips’ could be fully closed, but with modules you could ‘tie’ the wire in with the wire being away from the bracket base. Were F-8’s used? If the manufacturers instructions had to be followed then surely the a/w sequence for each system should have been followed as well?
    I’m sure there is an explanation for the methodology presented and it would be great to hear from the authors. An interesting paper.

    • Hi Andrew, yes you have raised good points. I can only assume that the investigators followed the recommendations made by the people who promote the self ligating bracket and this certainly may have an effect on the difference in treatment times for the two systems. It would be good if the author could answer this question and I will see if they are able?

      Best wishes: Kevin

  8. I am disappointed that my response to your self-ligation blog post has not been included in your blog site. I fear my compelling response might have been excluded because it did not fit the anti-self-ligation narrative.

  9. Kevin, you need to be taken to task for your inflammatory baseless articles you write. You have a picture of death along with the heading “another nail in the coffin for self ligating” then when you are challenged with some very simple answers you backtrack quicker than Sherman. Ie ‘I started using Damon brackets and I thought that they were great because of their ease of use and I really liked not using modules. From the point of view of supervising specialist trainees they were also great because they had to fully engage the wires……… does not mean that we need to stop using them’ strange you would say that!! But then again you hold everyone else to account but yourself. Andrew Flett has the most valid point about conducting research and using the self ligating system to their strengths against conventional and their strengths.
    Imagine if you will pitting a mike tyson in his prime v muhammed Ali, which one would win…well you would skew the results if you both made them fight the same way. If you both let them fight to their own and completely different styles then we would have our true answer. Sadly the medical industry isn’t interested in truth but only ego and putting their names to papers to gain notoriety.

    I look forward to your rep,y

    • Hi Peter, I am on holiday at the moment, I will reply when I get back.

      Best wishes Kevin

    • This is a response I submitted to Kevin concerning his death of self-ligation blog. Kevin said he would review and post, but conveniently never did. So I am once again submitting my post and this time i hope it is published on this blog site.
      “There appears to be little more to be said on self-ligation apart from…it offers no advantages.” I personally feel this statement is a little short sighted and focused solely on the speed of treatment. Assuming treatment time is not shortened by using self-ligating brackets let me offer some other advantages of self-ligating brackets both to the orthodontic practitioner and more importantly our patients who entrust us with their care.

      Advantages of self-ligation:

      1. Less discomfort for the patient. In a study published in Clinical Impressions 2006;15;5 entitled “Orthodontics from Good to Great” by Dr. Derick Tagawa he clearly shows that there is approximately 3 times less discomfort with self-ligating braces (Damon) than traditional edgewise brackets. I would encourage all my colleagues to read this article since it should be an objective of all orthodontists to treat their patients with the least amount of discomfort.
      2. Consistency or archwire engagement. Every self-ligating bracket, no matter whether the doctor or assistant engages the archwire in the bracket, produces a consistent amount of force on the tooth thus producing more predictable tooth movement. With steel or alastic ties there can be an inconsistency of force on the tooth after the wire is engaged in the bracket depending upon who is engaging (tying) the wire into the bracket.
      3. Security of archwire engagement. With traditional edgewise brackets if an elastic chain breaks, or an alastic tie comes off the tooth or a metal tie is loose and not properly securing the wire into the tooth unwanted and sometimes significant unwanted side effects can occur. This does not occur with self-ligating brackets since once the door or clip is closed the archwire is secured into the bracket.
      4. Fewer emergency visits for patients. Since the archwire is securely engaged in the self-ligating bracket, broken alastic chains have no effect on the engagement of the wire into the bracket and thereby adverse tooth movement will not occur thus eliminating the need for additional visits for patients to come to the practice to replace a broken chair.
      5. Fewer patient appointments are necessary to complete treatment. Another significant benefit for the patient is the reduction in the number of visits necessary to complete treatment when self-ligating brackets are used. There are numerous published articles documenting that the use of self-ligating brackets reduces the number patient visits necessary to complete treatment.
      6. Reduced chair time to complete treatment. A significant benefit for the orthodontist who utilizes self-ligating brackets is the reduced chair time necessary to complete treatment. This can increase significantly the profitability of the practice since reduced chair time reduces overhead costs.

      For an additional article which further documents and discusses the benefits of self-ligating brackets I would encourage you and your blog visitors to read the following article which appeared in Ortho Magazine, “Increasing Practice Productivity and Profitability Utilizing In-Ovation R Self-ligating Brackets”.
      Jerry Clark, DDS, MS

      • Hi Jerry, I had replied to you directly via email. But I will reply again when I am back from vacation

        Best wishes Kevin

        • Hi Kevin,

          Since you have put this topic out there and Jerry has asked questions about it, I feel it is highly unfair for you to respond personally and not on this open forum that you started.


          • As I said, I will reply when I get back from holiday. This will address all your comments. Is there anyone else who would like to comment while I take a rest from ortho?

      • Here is the reply that I posted in the blog post on self legation in late July

        Thanks for the comments. It is clear that you feel that in your hands there are advantages to self ligating brackets. However, my point about these brackets is that none of the claims of shorter treatment, less pain, better oral hygiene , reduction in treatment time etc are supported by the findings of some well conducted trials. These claims have also been discounted by the AAO council on scientific affairs. As a result, we have to conclude that for the average patient treated by the average orthodontist there are no advantages to self ligation.

        I note that you quote two papers, however, these are restrospective investigations and are subject to high levels of bias, particularly the one by Tagawa that was published in an unrefereed journal sponsored by Ormco. I hope that these comments are OK?

    • Thanks for the comments. Firstly, I am a little concerned that you feel that my posts are baseless and inflammatory. I think that most of my posts are based upon the scientific research literature and when we consider self ligating brackets, there is now a large amount of literature that states that their use does not lead to benefits over conventional brackets. I have simply interpreted this literature in what I have hoped is a clear and honest way.

      I am sorry that you do not like the graphics that I use, I only use these to lighten the blog a little.

      My comments on my personal use of self ligation reflect my views, I think that they are a good bracket in terms of wire engagement, but they are more expensive than conventional brackets, so I stopped using them in the absence of an advantage.

      I am not sure what you mean by your last comment. Are you suggesting that the researchers who have evaluated the brackets in trials have not used them correctly? If so are you supporting the self ligation philosophy which has limited basis in orthodontic science?

      As regards, the strengths of the brackets. As I have said before a bracket is a bracket, the factor that is most likely to influence treatment outcome is the orthodontist..

      I hope that I have answered your questions, if not let me know

  10. Hi Kevin,
    I found your article very interesting to read.
    I’m not sure if the heading of the article is ironic or hypocritical, as you state there is ‘no excuse’ to advertise the claims made by the companies who produce the brackets. Yet you stated several times above, you found them ‘great’ in some areas and there are ‘no advantages’ to using SL. Going by your standards, there is no excuse for you to write blogs that suggest SL is dead or near dead in the Ortho world, when in your replies to some of the comments you contradict yourself and of course your imagery used.
    As a matter of interest when you were using SL brackets how many cases were you doing a year and how many would you say you have done in total?

  11. Thanks for the comments. I take them on board. However, the title of the blog and the graphic were intended to be ironic and light, there is enough heavy stuff in writing at the moment. I suppose that I made this post as honest as possible, because when self ligating brackets were released I did use them, this was mostly because I liked the way that they engaged the archwires. I had also tried them several times throughout my career. However, I found that I did have problems with torque etc. The important thing to consider is that when I consented my patients into treatment I did not tell them that I was going to shorten their treatment time or avoid extractions. There is nothing wrong in trying a variation of a bracket and then when evidence is available on its effectiveness to stop using it. After all a bracket is just a bracket…..I have not done many cases with self ligating brackets as I stopped using them shortly after we bought them in our department. I am not sure that this is relevant, as I was commenting on evidence in the literature?

    • Thanks for your reply Kevin,
      Having attended lectures you have given, your dislike for SL is open to see and almost legendary amongst the UK Ortho fraternity, that fact is not in doubt. As you stated, during your consent with your patients you don’t make certain ‘untrue’ claims, which is what you have a problem with other Dr’s and/or companies doing. So when you try to pass off the heading and icons as light hearted, it feels completely disingenuous from you, as you are making claims that are untrue ie the death of SL, which really, in your own words works just fine. I’m afraid it seems you are guilty of what you dislike most, and that is misrepresentation, which is where the true irony lies in your blog.

      Many thanks

      • Hi and thanks for the comments again. As I said in my previous post, I have taken your comment on board. However, I have to respond to some of the points that you have made. Firstly, I do not dislike self ligation, I have always said that the concept is great. But, what I dislike is the unsupported claims made by the industry and some orthodontists. This is particularly true for the content of websites that are directed at the public that make claims for SL treatments, which can only be obtained privately. I hope that you do not have a problem with this. I have thought about the icon and the title of this blog a lot since your comments and I still do not understand why this irritates you, I was simply trying to be light hearted, I think that there is nothing wrong with this approach. We are far too serious in our publications and learning,
        Best wishes: Kevin

  12. Hi Kevin, thanks for the reply.

    You are a well respected member of the Ortho community and also very influential, when you say you don’t dislike SL, I have to take you at face value. However if you were to ask anyone in the UK Ortho community what your thoughts were on SL it wouldn’t be unfair to say their answer would be you are not a fan. This is mainly due to you mentioning it in most of your lectures in a negative light. I wasn’t able to attend the BOC this year, but was aware you were speaking at it, did you mention SL at all? If so was it a positive or negative comment.
    There fore I feel the icons and blog title are an attempt by yourself to dissuade non users, and put forward your own personal agenda against the bracket system. It is a known fact that headlines tend to influence people’s perspective rather than the content of the article. I go back to my original point you are as guilty of misrepresentation as the companies that make unsupported claims.
    Many Thanks

  13. Hi Kevin
    I have only recently looked at your blog and I am finding it most interesting. However, with regard to the research paper on SL brackets no mention has been made about the claims for dento-alveolar arch development. Neither were we informed as to whether these cases were extraction or non-extraction. Some of the promoters of SLBs claim that they reduce the need for extractions and therefore space closure is not an issue. Perhaps Bristol University would like to conduct another research programme comparing arch development. I welcome your comments.

  14. Hi Kevin
    I have only recently looked at your blog and I am finding it most interesting. However, with regard to the research paper on SL brackets no mention has been made about the claims for dento-alveolar arch development. Neither were we informed as to whether these cases were extraction or non-extraction. Dr David Bernie’s claim is that SL brackets reduce the need for extractions and therefore space closure is not an issue. Perhaps Bristol University would like to conduct another research programme comparing arch development. I welcome your comments.

  15. I have read the material and methods, there is a fundamental problem, the sequence of wires. Alignment in passive self-ligating brackets can not be performed if no wire is inserted with Xx’025 of depth. So the study wasted time trying to find an alignment with arcs of 0.018 and 0.022. This study should be repeated by placing an initial 0.014, followed by a rectangular wire of 0.025 depth and then measuring the alignment. The depth of the wires is everything in the control of rotations in self-ligating brackets.

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