An occasionally irregular blog about orthodontics

The top ten orthodontic papers that have influenced me.

The top ten orthodontic papers that have influenced me.

The top 10 papers that have influenced my career?

I have been away lecturing in Italy and taking a short vacation this week, so I have not had time to write a new blog post.  But I have decided to re-publish one of my earlier blogs that readers may have missed. This was a simple list and details of the top ten orthodontic papers that have influenced me and I hope that you find them interesting.

They may not be the best research papers, however, they are the papers that persuaded me to think carefully about the areas that they were addressing. You will see most of them are somewhat dated. But I think that  it is very worthwhile for us to look back at studies that tend to challenge the thinking at that time.

 Dental and social effects of malocclusion and effectiveness of orthodontic treatment: a review.

Shaw WCAddy MRay C.

Community Dent Oral Epidemiol. 1980 Feb;8(1):36-45.

Apart from this paper being a classic, it means a lot to me, because when I was applying to the orthodontic program at Manchester, one of the orthodontic registrars at Newcastle (where I was based) suggested that I should read it. This was because Bill Shaw  had recently been appointed to Manchester and was bound to be  interviewing me. So I  got out the paper and read it on the train journey to Manchester. In fact, they did not ask me any questions about it!   Even though I did not understand much of the subject area, I found it interesting.  I have read this many times since then and it certainly is a classic paper, because it stated the case that the need for orthodontic treatment was not clear cut. Importantly, this work led to much of the work that developed IOTN and PAR.   Interestingly,  many of the questions that they raised in the paper are still unanswered today

Equilibrium theory revisited

Proffit WR.

Angle Orthod. 1978 Jul;48(3):175-86.

This is a paper which I still suggest all postgraduates and residents read. Again, this is somewhat dated, but timeless. In the paper Bill Proffit  outlines the rationale behind the factors that influence the position of the teeth.  While most of this is personal opinion, it is very hard to put forward an alternative hypothesis.  This is still highly relevant paper as we still agonise over the need for retention.

Methods used to evaluate growth modification in Class II malocclusion.

Tulloch JF, Medland W, Tuncay OC.

Am J Orthod Dentofacial Orthop. 1990 Oct;98(4):340

This paper was one of the first systematic reviews into the effectiveness of orthodontic treatment and was the basis for the study into early orthodontic treatment carried out at the University of North Carolina. I felt that this was a fascinating paper because it made the orthodontic research community aware of the problems that were arising from our use of traditional retrospective methods. This paper is a ” must read” for all aspiring orthodontists.

 Cephalometrics in perspective

Hixon EH.

Angle Orthod. 1972 Jul;42(3):200-11. and

This was a paper that help me start to understand cephalometrics  and also develop a rather cynical viewpoint to their use. It also probably has the best start to any orthodontic paper that has been published.

 “If  one could sit on the moon and look at the activities of the 3500 different millions of humans each trying to obtain elbow room and food on a rather small planet in the third-rate solar system and ask himself “what have cephalometrics contributed?”.

A long-term comparison of non-extraction and premolar extraction edgewise therapy in “borderline” Class II patients.

Paquette DEBeattie JRJohnston LE Jr.

Am J Orthod Dentofacial Orthop. 1992 Jul;102(1):1-14.

When I was starting on a rather evangelical point in my career and I had “discovered” clinical trials, I was putting a viewpoint forwards that the only type of research of value was a clinical trial. While this is still my opinion. I have mellowed and realised that other well-controlled studies, while not providing the same high level of evidence to a trial, may still help us reduce uncertainty about our treatment. This paper addresses a difficult question by careful selection of matched cases in a retrospective sample. This was also the first time I came across Lysle Johnston, and his very logical questioning approach to orthodontics.

The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial.

Tulloch JF, Phillips C, Koch G, Proffit WR.

Am J Orthod Dentofacial Orthop. 1997 Apr;111(4):391-400.

This paper is simply a classic. It was a preliminary report on the first large scale RCT in orthodontics.  This led the way for many researchers to start using RCT methodology.

Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear

Stephen D. Keeling, Timothy T. Wheeler, Gregory J. King, Cynthia W. Garvan, David A. Cohen, Salvatore Cabassa, Susan P. McGorray, Marie G. Taylor

American Journal of Orthodontics & Dentofacial Orthopedics

Volume 113, Issue 1 , Pages 40-50, January 1998

And so is this.

The lead author on this paper was Stephen Keeling. I met him when they were starting to analyse the data on this trial and he came to Pittsburgh so that I could show him how to use the Peer Assessment Rating. He very sadly died a couple of years later and he was one of the nicest people that I’ve ever worked with

Consistency of orthodontic treatment decisions relative to diagnostic records

Unae Kim Han, Katherine W.L. Vig, Jane A. Weintraub, Peter S. Vig, Charles J. Kowalski

American journal of orthodontics and dentofacial orthopedics  September 1991 (volume 100 issue 3 Pages 212-219)

Again, this is a paper that questioned current dogma at that time and orthodontics.  It still stands close scrutiny and its central message is still very relevant today, particularly with the development of CBCT

Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt.

Houston WJ.

Eur J Orthod. 1980;2(2):81-93.

Another paper from a great British orthodontist. I remember reading this when I was on the orthodontic programme and did struggle to understand it because it is rather complex. In effect Houston was illustrating that the hand wrist radiograph was of no value in assessing skeletal maturity. This paper probably resulted in less young people being exposed to unnecessary radiation. This is a considerable achievement

The stability of the lower  labial  segment.

Mills JRE

Transactions of the British Society of Orthodontics. 1966 . 54:11 – 24

I add this paper for completeness.  Unfortunately, I could not get a PDF. This was published a long time ago and is very dated.  There is no real science  in the paper, as Mills simply collected a convenience sample. However, it does provide us with a useful message that we probably cannot ignore as there is no other compelling evidence on the position that we should place the lower incisors at the end of orthodontic treatment.

That’s about it on these papers. I hope that you find time to read them and while you may not agree on my selection I hope that you enjoy looking back.

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  1. Salesse says:

    Thanks for the reading list 🙂 .
    The link you send to this article in your email is broken
    Best

  2. Dr Dharma R M says:

    Dear Obrien
    It is indeed a pleasure to read your blogs and are very informative . Thank you for your invaluable service to Orthodontics .
    I met you recently at the Annual session of AAO In Orlando

  3. Lawrence J. Levens, DDS, MSD, MScLO says:

    Thanks as always for your thoughtful insights into our profession. I am always happy to see a new Kevin O’Brien blog in my inbox.

    I would like to suggest the addition of one more contemporary to your list (a top 11 list?) that has meant a great deal to me. It is the singular reason I learned more about lingual orthodontics as a treatment device for patients desiring hidden appliances. In Sept. 2009, Dr. Neil Kravitz et al published in the AJO-DO an article regarding aligners (Invisalign in particular) and the devices efficacy.

    How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign (Am J Orthod Dentofacial Orthop 2009; 135:27-35). It is both on the AAOmembers.com website and on Dr. Kravitz’s website at Kravitzorthodontics.com (under Team Kravitz > publications).

    The study compared the expected tooth movement from the ClinCheck setup (pre-treatment) to the final results of the treatment. The results were that there was approximately a 42% match between the two when superimposed. No matter how I try to minimize the results found I cannot find a way to make a 42% beneficial result sound like a good choice in treatment for my patients.

    Even today Invisalign boasts on their website that over 3 million patient treatments have been undertaken using Invisalign. One would expect to see a multitude of additional peer-reviewed clinical studies showing the above article was somehow wrong but I have not found one yet. Hopefully there are other readers that can tell me of some (or even one) that shows otherwise. I challenged my Invisalign representative to present such articles to me and he has not since returned to my office for discussion.

    I have been told that the above study was also stacked to show positive results in aligner treatment. If true, I was told that Dr. Kravitz was on Align Technologies, Inc. Clinical Advisory board at the time of the study, that the study was paid for by Align Technologies, Inc. and, finally, that this was a prospective study meaning that the patients were told that they would be part of the study. I understand that this sometimes results in patients working much harder than expected to follow instructions of the clinician. If all of this is indeed true I would think that the 42% achievement in the findings would have actually been much lower.

    We are now practically assaulted daily by dental companies showing us just the information that garners a favorable opinion of their products. But as my father told me, “putting training wheels on your grandma doesn’t make her a car” and so must all be vigilant in what we believe when the information comes from a less than objective source such as a company that gains financially from providing us with less than proven “science” on their products.

    Again, if someone out there has additional information on the success to be gained in aligner treatment please reply. I can’t find anything other than case reports, anecdotal stories of success and archived video of Invisalign presentations and User’s meetings.

    • vicki vlaskalic says:

      Hi Dr Levens! As a user and investigator of the Invisalign system, I shall attempt to answer your plea at the risk of being labelled a heretic! I gain solace from the knowledge that pioneers are often labelled as such, and that time and science may be the ultimate judges.
      Firstly let me state that I have no financial interest in Align technology and have never owned shares in the company despite being offered options for around 1 cent! (not that I didn’t believe the potential – actually I didn’t at first- but I found it unethical to investigate if owning shares). I did provide initial “training” to US and then largely Japanese doctors for 8 years and still lecture occasionally about the Appliance System. As one of the primary investigators, along with Prof Robert Boyd at Pacific CA, the study and clinical use of Invisalign has become somewhat of a professional hobby (replacing objective measurement of orthodontic outcomes and root resorption as previous research topics) – so therein lies my bias.
      I am kicking myself for doing this as I feel that you have made up your mind and there is very little to gain except your torment, but here goes! I would please ask of you to set aside your frustration with other aspects of the Invisalign system, such as aggressive consumer marketing and the whole GP debate and look at this in a similar way to assessing or comparing any 2 mechanical systems in terms of clinical “success” – not an easy task. Ask the same questions of our fixed appliances that we do of the Invisalign system in terms of evidence for accuracy, efficiency”. (I don’t believe fixed appliances are either accurate nor efficient, but we have learned how to overcome the weakness (bond position methods, wire bending, so many different bracket prescriptions and designs, positioners, suresmile all around as evidence of this), and to make them more efficient so that they became the “gold standard” -( there was no alternative really)…another discussion..

      I feel that the paper you refer to as upholding the current efficiency of the Invisalign System has many fatal flaws, the most significant being the inability of the methodology to answer the aim of the study, and if I fail to illustrate this point to you below, I hope that you acknowledge that the Invisalign system used to treat the sample of 37 in 2007-8 in a post grad department is a significantly different appliance system to that in use today – broadly aligner material has changed, active attachments have now been developed and custom engineered based on biomechnical principles by eminent engineers who have designed bracket and wire systems, the software in use – both by the technicians and clinicians has radically changed in terms of vector defaults (eg. no longer 5-7 degrees rotation per aligner but max 2 degrees), staging has changed to slow velocity and alter movement paths, as well as the addition of many diagnostic tools such as ability for the clinician rather than technician to position the virtual dentition and conventional attachments and occlusal contacts being visible. I would hope that this information alone is sufficient to nullify any valid conclusion that readers may now gain from the article you site. If not, please read on!
      As there are so many areas of “contention” – I will make a list. If you feel that you need me to elaborate on any 1 area, please let me know, nicely.:)
      1. How well does Invisalign work? – Can anyone please tell me how well any particular bracket and wire system works? Not only can we not measure this for non-digital bracket systems, we have very little evidence of the nature that you expect of the Invisalign system, 1 has been around about 80 years longer than the other. Yes, we can use anecdotal evidence, but there is plenty of that now for Invisalign patients too (surgical, extraction, impacted canines, every case type). Objective outcome scoring you cry? Its coming, multicentre prospective outcome studies comparing fixed and Invisalign outcomes. I do fear that they may be similarly obsolete when published due to the rapid evolution of the Invisalign technology however we need to start somewhere, watch this space.
      2. sample is from a university clinic, treated by residents. Arguable as to orthodontic competency with fixed appliances let alone new technology that requires traditional and new skill set to obtain a predictable, physiologically compatible and aesthetic clinical result. (studies mentioned in this paper also found that residents have failed to treat a significant number of fixed cases to ABO standards- see below – but this is never quoted!)
      3. sample selection: 2 faculty members – not sure if they actually had used the system – “selected” the subjects specifically using their own criteria for what they thought Invisalign was capable of! This is a huge flaw and contradiction in study design as it creates bias immediately towards what the clinicians feel is achievable – or not – with the appliance system that they are testing!!
      4. When we test an appliance system, the most realistic and useful data comes from the test when used by an “expert” in that system – eg. when we compared outcomes of orthodontic provision in different modes of practice, we chose competent ABO certified clinicians USING THEIR PREFERED MECHANICS. Otheriwise we can test a Ferrari at the hands of an unlicensed driver..valid conclusion :car doesn’t work?? Courtesy of Shelly Baumrind.
      5. The authors note in opening as a weakness, that the Invisalign system does not come with scientific evidence regarding indications, efficacy, limitations, or treatment effects. Where is the equivalent literature for the many fixed systems available? Yes, the new kid on the block needs to be held to a standard but should it be higher than standards we currently accept? Perhaps.
      6. The authors quote a paper stating that Invisalign cases received a passing rate 27% lower than fixed appliances – the paper, having many similar flaws to the one in mention also reported “as a side note, even the fixed appliance cases had
      a surprisingly low OGS pass rate- the braces group 23 received passing grade and 25 received
      failing grades” !!Djeu et al ’06. Thats a paper in itself! Do we then conclude that over 50% of fixed appliance treatments fail to move teeth predictably?
      They go on to quote several other early papers, Kunico et al, Bollen and Clements and rightly they do acknowledge that these papers are not testing the “identical” Invisalign system in use at the time of the study- questionable term to resort to in scientific evaluation – and needless to say these authors (and myself) have fallen to the same fate when attempting to evaluate clinically such a rapidly changing system. If you plan a prospective study, treat moderate complexity patients, evaluate and publish – usually the publication comes 2 to 3 years later at the earliest.
      7. The clinician/s preparing the ClinCheck software for the patients was not clearly identified in terms of experience with the system or in fact orthodontics- this is the key to gaining more predictable movement (no matter what appliance) and ultimately successful occlusal outcome. The authors mention choice of attachments and tooth set up was determined by the “clinician”. If this was performed by a clinician, even the most experienced orthodontists but one who does not use Invisalign (or a resident in training as implied) , then the chance of success is biased towards failure, just as initial bondings, finishing of cases of any orthodontist is generally not as accurate as in a more experienced clinician- like wine we get better with time.
      9. Clinicians were allowed to request IPR, attachments and overcorrection at their discretion. This introduces a significant operator variable that is arguably larger than the variable to be tested – accuracy of the tooth movement expressed when compared to that being programmed. Overcorrection, misuse of attachments and insufficient expression of IPR if approved all influence tooth movement and in this case were arbitrarily requested, not by Invisalign software defaults. To understand the implications of these treatment choices in terms of resulting movement takes time, just as understanding the implications of bracket position or wire bending – you don’t know what you will get until you get there, but in the case of more experienced users, their “educated” decisions will be closer to the mark in general when compared to a resident (or any clinician) using a system for the first time
      10. Patient instructions were not consistent with Invisalign System guidelines. Aligners and aligner features are designed and engineered to be worn for 2 week intervals (recently being tested). In this study, the patients were told to wear aligners for between 2-3 weeks. Aligners are plastic, they stretch and deform the longer they are worn. Wearing an aligner for longer than prescribed is contrary to company advice and in my experience never assists movement but makes it worse (It is proper seating and use of the next new aligner that is often more useful..)
      11. Superimposition using Tooth Measure, Align proprietary software – potential bias as Dr Levens already pointed out. In addition, we cannot test the error margin of the software, PVS technique , storage, scan discrepancies that all accumulate to create noise in the final figures. It is difficult to test movement, as palatal rugae are not included in TREAT software, and in our studies at University of Melbourne, Newby, McDonald, Scott, Wang, have all showed that even teeth that are not programmed to move – especially those adjacent to those programmed (premolars in the case of this study) actually do move making the methodology less accurate in reporting true dental change, especially where measurements are small.
      12. The accuracy was determined as a % of movement programmed (not “predicted” as term used). As Kevin points out above, if a tooth was programmed to move 1mm but moved 0.5mm, the accuracy would be 50%. …..In addition, mean accuracy was reported, so that if 1 clinician underperformed the IPR they requested, 1 patient was non-compliant or movement was retarded, this 1 subject will “muddy” the sample – so that theoretically we could have 99% moving well, but with 1 low score. This could significantly reduce the reported accuracy of the system potentially based on 1 individual patient – (I don’t believe that this happened, but it illustrates how the Methodology and crunching can easily distort the results)
      13. There is no mention of the influence or use of attachments in rotations, extrusions etc. except a blanket number of teeth with attachments. The attachment design and defaults defaults were vastly different in 2008 and prior ; there was no default engineering of active attachments to assist the expression of movement as we see today. It was left to the individual clinician – assume resident – to understand whether they should be requested , where and what type. In our Uni of Melbourne studies, we have found that teeth with attachments, even the conventional type express a higher degree of programmed movement than teeth without. When the authors report that extrusion was relatively low in comparison to rotation, labial and lingual movements, it would have been very useful to know if attachments were actually used, and how. This “weakness” of extrusion when using aligners alone has been largely overcome with attachment use. The past necessity of combination of elastics and buttons to achieve certain dental extrusion not expressed is obsolete today – even so it is not a failure of Invisalign to combine mechanics – imagine assessing fixed appliance ability to correct A-P discrepancy without the ability to apply Class II or Class III mechanics – as was done in the studies quoted in this paper evaluating ability of aligners to achieve A-P correction! Please lets keep the playing field level. You may combine mechanics , RPE, elastics – it is not seen as a failure with brackets, why with aligners? The Invisalign system works to a degree of clinical acceptability – that much we can say from anecdotal evidence – when used judiciously. To expect to have poor diagnosis, no treatment plan, send a PVS, /scan, accept software programming without understanding the mechanical implications of each tooth programmed and mechanical features available, then not to apply clinical evaluation and adjunctive mechanics such as needed in Class II and III correction – ah, I believe we will have a significant chance of failure.
      14. The authors compare their less favourable findings on intrusion with previous studies. Anterior intrusion mechanics requires attachments placed distal to the segment being intruded. As this was anterior treatment only and no premolars were treated, it is no wonder that they have lower results than other studies quoted, and a surprise that they were as “accurate” as reported. Again, without using the system as designed, and understanding aligner mechanics, it is a critical failure to assess these movements. Intrusion attachments placed on 1 or 2 premolars (depending on rotation requirements) is now default and has been for many years. In our early studies at Pacific quoted in the paper, we were aware of weaknesses and used methods to overcome them that were excluded from use in this study.
      15. Aligner material is very different in properties (yes, we want to know them but this is for our independent testing, company wont give us the exact material properties as bracket and wire companies don’t either)
      16. velocity is different, no longer 0.33mm but max 0.25 currently
      17. PVS was used, scans are now available that allow less data
      abrogation due to fewer manufacturing steps that may allow further increase in movement accuracy
      18. 10X more patients have now been treated since the paper was written – yes, anecdotal evidence of case reports, yes, likely clinical failures involved just as with fixed over a 10 year period but that is a lot more intellectual data collected by Align to study and improve outcomes
      19. When will people stop referring to refinement or midcourse correction as a failure? Where was that ever written? Minimize them great, but really! For apparently educated individuals to think that this or ANY system can produce clinically successful outcomes without refinement is at this point in the world of orthodontics ludicrous and lazy. I feel that this defines a responsible clinician from a lazy or very lucky one! Do we really expect to take a scan (or PVS), scan that, clean up the digitization, separate the teeth, move the teeth using default protocols- some being based on new data, some are the original ones that were best estimate based on conventional orthodontic science, have individual technicians also interpret doctors instructions, transfer to different software program, have individual clinician input – sometimes more sometimes less, create SLA, manufacture aligner, package, ship, provide varied instructions to very individual patients with very individual physiologies such as age difference, bone density, medication and more significantly compliance differences and STILL expect to achieve 100% of the clinician approved ClinCheck! Nonsense! Even if all of the cumulative engineering variables are small, we can never, not even ALIGN can ever remove the largest variable of the patient. And aligners rely on patient compliance more than fixed appliances. Fact. If we accept that, case refinement will always be around for those who scrutinize results after the first series of aligners as we do prior to deband. Almost always in patients I see as an orthodontist I am going for a second “finishing” series. Yes it takes time, yes the patient is almost always happy after the first but currently my gold standard is the most “ideal” occlusion for any give patient and that’s the standard Invisalign, in my experience, may achieve if strengths and weaknesses are understood and compensated for. Do you consider the need for resorting to wire bending a failure? Rebonding a failure of the system? Same thing. the bonding position, wire slop, bracket inconsistency, debonding, crown moving more than the root apex, tendency to tip, tendency to extrude, etc etc. This is not a failure of fixed appliances, we have learned to work with the weakness of generic slot prescription as we work with weakness of default computer tooth movement programming . Do your wire bending / rebonding and do a case refinement – every movement / tooth will express to a different degree and this needs to be understood and dealt with.
      20. So there are always good things we can take from any paper. Kudos for attempting a difficult study and addressing a necessary question in the early days. Kudos to Align for supporting the research no matter what the outcome – and they still do. To be fair, the authors do point out weakness of their design and the difficulties involved, but many of the above variables perhaps could have been better controlled, notably operator experience and variability. If we compare outcome of 5 orthos with fixed appliances in the same case, do we really think we will get the same results – no – even if we used direct bonding! Yes, Invisalign has the distinct advantage and lets say disadvantage of being digital – we can now program aligners to express smaller, more precise movements …but we can also measure their “success” or “failure” – whichever way your cup is full.

      I believe a more appropriate title for this paper would have been “how much programmed tooth movement may be expressed by Invisalign aligners alone in the hands of post graduate students using individual treatment protocols?” This paper neither tested “how well the Invisalign system works” nor was subject selection appropriate , nor did it test the “efficacy” of movement. But it was a start. University of Melbourne, department of Orthodontics use similar methodology but an “expert” (bad term) clinician familiar with the system strengths and weaknesses, prospective, subject selection based on sequential starts, conebeam root analysis and independent engineering software, not Align Technology software. Stay tuned for publications, Newby, Wang, McDonald, Scott all postgrad masters thesis.

      Finally, I would like to add the obvious but often forgotten that occusal outcome is only 1 aspect, all be it crucial, in assessing orthodontic outcome. Add patient comfort, social impairment, risk of iatrogenic potential, appointment time, cost and other factors that may work for or against a system and we may obtain a more thorough evaluation of the success of the system. For now fixed appliances may be considered the gold standard, but the rapid rate of data acquisition and digital nature of this and such systems makes identification and measurement of mechanical weakness relatively simple so that by creating “smart” aligners – programmed tooth movement that allows for “lag, slop, non-fit, inaccuracy, lack of full expression,”- in any given patient will not be far away. Imagine being able to scan in-house, select movement programming custom made for pregnant patients, those elderly, those with alveolar bone loss, those with long roots, short roots etc , then 3D print aligners in your office- that’s a possible future with such an appliance system! ….We will still need diagnosis, treatment planning, thorough knowledge of anatomy, physiology, biomechanics and aesthetics -, just a different appliance system.

      Dr Levens, probably more than was required. You can see that I am passionate about learning and evaluating this form of mechanics. I truly hope that if you happen to see your Invisalign rep again, that you go gently on them! From above, you may see why it is so difficult to produce the literature you are asking them for – either for the Invisalign System or traditional fixed appliances. In my experience, the culture at Align has been not to bad-mouth or criticize alternative techniques or literature that is unfavourable, but to work on making their system better and eventually -they hope- the best choice for patients…we don’t have to love it but I believe that we need to understand it because it is here and we are specialists in the field.

      • Lawrence J. Levens, DDS, MSd, MScLO says:

        Dr. Vlaskalic. Thanks so much for your professional and respectful response to my suggested article to include in Dr. O’Brien’s Top 10 list. In retrospect I wish I had suggested a 12th article for Dr. O’Brien to include (Ker Reitan’s article from 1967 in AJO, “Clinical and histological observations on tooth movement during and after orthodontic tooth movement”).
        I agree with many of your well-thought out points on the Kravitz article. Yes, it is old (now 6 years) and certainly much has been tried to improve the Invisalign device since that time. I also agree that there are flaws in the study design of the article which is often the case in many if not most studies. And yet, the article passed the “sniff test” of the editorial board of the AJO-DO well enough to have been published in one of the most impactful journals with peer-review in all of Orthodontics. Should we simply dismiss the study as worthless or the results as meaningless? The 42% figure cited in the study is an awfully long way from something most people find to be success.
        Even with the difficulties in producing research on the efficacy of any orthodontic device, I am still left completely perplexed why there is not further research to refute those findings in any legitimate journal? As you noted, using a digitally planned and fabricated device lends itself much more easily to such research and, of course, that is exactly what Invisalign is. For comparison I would propose that one read Dan Grauer’s article from AJODO in Sept. 2011 on digitally produced orthodontic appliances (Incognito in particular) that showed a 90%+ match in treatment outcomes as compared to the setup
        The Invisalign website appears to claim more than 3 million cases of Invisalign have now been attempted. With that large number of treatments attempted– including use in graduate Orthodontic departments around the world– I do not understand how there can be a void in well-performed studies showing differing and positive effects and results from Invisalign use? Even if the research process is difficult there have been more difficult topics tackeled in the literature.
        One has to wonder what is standing in the way of such research? This void of countering articles certainly does nothing to dispel the results of the Kravtiz article cited. Is it possible that Algin Technologies is influencing what research is performed due to having had the Kravitz article backfire in gaining support for their device? This certainly would not be the first time a company with financial interests attempts to influence the science presented in the literature. After all, like many other appliances taught in graduate programs the product is likely given to the Orthodontic programs at reduced or no cost to the department. In addition, I suspect the company is also gifting the residents and programs in a variety of ways that could influence opinions and garner favors. Perhaps there is some oversight by the company of what is and is not researched and published using their product?
        As you can surmise, I am something of a skeptic and without evidence to refute the findings of the Kravitz study I cannot find a way to assume that a 42% superimposition match in the success of the device has now been turned around into a an orthodontic device with great success without any supporting evidence to prove this (no matter how old or flawed this AJO-DO study may seem). But I am also open to changing my mind if well done bona-fide research shows me something different.
        And simply for the sake of clarity I will tell you that yes, I do use the Invisalign device and agree it needs to be understood by specialists. But being understood can also mean that nothing has been shown to prove it is consistently successful enough for patients that are trusting me to give them advice on how to achieve the best outcomes of their treamtent. I have had some successes with the device in my own office but I cannot say it is as good as other devices in my hands.
        Again, thank you for your response as I enjoy hearing other’s perspectives as food for thought.

    • Vicki Vlaskalic says:

      Hi Dr Levens – I did provide a lengthy reply to your request for comment on this paper, however it was not posted. I have prepared a précis version to allow fair exchange of ideas. I have a bias in that I use the Invisalign system and was one of the original investigators at Pacific, CA alongside Prof Robert Boyd. My financial interest remains occasional educational sponsored lectures.
      1. The study and paper that you refer to as upholding the current efficiency of the Invisalign System has fatal flaws, the most significant being the inability of the methodology to answer the aim of the study, and many conclusions, although valid are conjecture and not answered by the study, more suitable in the discussion.
      2. The Invisalign system used to treat the sample of 37 in 2007-8 is a significantly different appliance system to that in use today – broadly aligner material has changed, active attachments have now been developed and custom engineered, the software defaults in use – both by the technicians and clinicians has radically changed in terms of velocity (e.g.. no longer 5-7 degrees rotation per aligner but max 2 degrees, not 0.33mm but 0.25mm per aligner max linear velocity), staging has changed to alter movement paths, as well as the addition of further diagnostic tools such as ability for the clinician rather than technician to position the virtual dentition and conventional attachments and occlusal contacts being visible.
      3. How well does Invisalign work? – Can anyone please tell me how well any particular bracket and wire system works? Not only can we not measure this for non-digital bracket systems, we have little evidence of the nature that you expect of the Invisalign system. The authors quote a paper stating that Invisalign cases received a passing rate 27% lower than fixed appliances – that same paper, having many similar flaws to the one in mention also reported “as a side note, even the fixed appliance cases had a surprisingly low OGS pass rate- the braces group 23 received passing grade and 25 received failing grades” Djeu et al ’06. Do we then conclude that over 50% of fixed appliance treatments fail to move teeth predictably?
      4. The sample is from a university clinic, treated by residents. Arguable as to orthodontic competency with fixed appliances (above) let alone technology that takes additional skill set.
      5. Sample selection: 2 faculty members “selected” the subjects specifically using their own criteria for what they thought Invisalign was capable of. This is a huge flaw and contradiction in study design as it creates bias and skewed sample
      6. The authors note “the Invisalign system does not come with scientific evidence of regarding indications, efficacy, limitations, or treatment effects”. Where is the equivalent literature for the many fixed systems available?
      7. The clinician/s preparing the ClinCheck software for the patients was not clearly identified – If this was performed by a clinician, even the most experienced orthodontists but one who does not use Invisalign (or a resident in training as implied) then the chance of success is biased towards failure, just as initial bonding by residents is generally not as accurate as in a more experienced clinicians.
      8. Clinicians were allowed to request IPR, attachments and overcorrection at their discretion. This introduces a significant operator variable that is arguably larger than the variable to be tested – similarity of the resulting tooth movement when compared to that being programmed.
      9. Patient instructions were not consistent with Invisalign System guidelines….
      10. Superimposition using Tooth Measure, Align proprietary software – potential bias as Dr Levens already pointed out.
      11. Mean accuracy was reported, so that theoretically we could have 99% moving “well”, but with 1 outlier, this could be significantly reduced so that the accuracy of the system may be potentially based on 1 individual patient, as suggested by large SD – (I don’t believe that this happened, but it illustrates how the Methodology can easily distort the results)
      12. The authors compare their findings on intrusion with previous studies. Anterior intrusion mechanics requires attachments placed distal to the segment being intruded. As this was anterior treatment only and no premolars were treated, it is no wonder that they have lower results than other studies quoted, and a surprise that they were as “accurate” as reported. Deep bite mechanics have also new defaults.
      13. Birte Melsen is currently the best source in my experience to test and inform us just how “accurate” various fixed appliance systems are….I believe the message is that we are obligated to learn intricately the strengths and weaknesses of the appliance system we may select in order to use them well.

  4. vicki vlaskalic says:

    Thanks Kevin for the trip down memory lane. It is noteworthy that these papers have such a varied methodology and yet have contributed significantly to creating your matrix for orthodontic knowledge. This blog forms part of my matrix:) I am sure that we all have our favourite literature for both academic and sentimental reasons – I recall being staggered when I somehow found myself in a dental library reading dusty bound minutes of ortho society meetings from the early 1900’s. Our forefathers discussed many of the same issues that we still investigate today! The great extraction debate of 1911, (reprint) American Journal of Orthodontics Volume 50, Issue 11, November 1964, 843-851 stands out to me for the topical discussion, wonderful prose, and the attention to so many factors we consider essential in diagnosis and treatment planning today – facial aesthetics from the outside in, growth and development, subjectivity in aesthetic evaluation. It is a humbling and thought provoking read! VV

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