July 08, 2014

TADS are effective: The results of a trial

TADS are effective! More published evidence….

The World Cup is now moving to the final stages and I have begun the slow migration away from my television to return to the world of orthodontic research. This has allowed me to put together a blog post for this week. This is concerned with a recently published trial of temporary anchorage devices in the AJO-DDO.

 The effectiveness of 3 methods of anchorage reinforcement for maximum anchorage in adolescents; a 3-arm multicenter randomized clinical trial

Jonathan Sandler et al. North of England, UK

AJO-DDO 2014: 146: 1: 10-20


The more observant of you will have spotted that I am a co-author of the paper, and I know a lot about this study. So here is my unbiased review!

This project was carried out by Jonathan Sandler and a team from the North of England. It was a very straightforward investigation, but it took a lot of work, and Jonathan is describing it here.


We attempted to answer a simple question

 “Is there a difference in the effectiveness of TADS, Nance button palatal arch and headgear”?


What did they do?

This was a three arm parallel sided randomized trial. Seventy eight patients aged 12-18 years, requiring absolute anchorage were randomized to be treated with (i) TADS, (ii) Nance palatal arch and (iii) headgear. As with all trials reported in the AJO-DDO the paper was written according to CONSORT guidelines and, therefore, it was fairly clear to read and check for quality. The randomization, blinding and concealment was good, a sample size calculation was carried out and the statistics were relevant.

The primary outcome was the amount of molar tooth movement. The secondary outcomes were the quality of the final finish result (PAR) and the patients opinions on their treatment. We collected data at the start of treatment, at the end of anchorage reinforcement and at the end of treatment.

We also measured tooth movement from 3D scans of casts that were superimposed on the palatal rugae. This allowed us to accurately measure tooth movement in three dimensions and avoid the many errors involved with cephalometric measurement.

 What did they find?

When we looked at tooth movement we found that no method of anchorage reinforcement was any better than another. There were also no differences in the number of attendances and duration of treatment.

We also found that the final occlusal result of treatment was better for the TAD group when compared to headgear.

Another, and perhaps the most important finding, was that the patients reported less problems and concerns with TADS than Headgear.

 What did I think?

I hope that you feel that this was a good study that answered a straightforward clinical question using relevant methods. While we found that there were no differences in the effectiveness of the methods of anchorage reinforcement, there were differences in the patient’s perceptions. The addition of this important information suggests that the method of choice of anchorage reinforcement for both the clinicians and patients is the use of TADS.

It is also worth pointing out that if we had not collected the patient information , this would have been “another trial finding no difference” and illustrates the importance of moving away from “orthodontic” measures to collect information that is relevant to our patients.

Finally, it is great to see a clinical trial reporting on an orthodontic innovation is proving to be effective. We are currently in the final stages of finishing a Cochrane review on methods of anchorage reinforcement. I will publish a blog on this as soon as it is published, so watch this space!


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Have your say!

  1. Thank you for this nice review. I always had the impression that palatal bar are ineffective as anchorage reinforcement measures. I may have got this from the few studies that compared patients with palatal bars to patients without them and found no significant difference regarding mesial movement of the first molars. Here is an example: http://www.ncbi.nlm.nih.gov/pubmed/18538249
    Can you please comment on that?

    • I think the Zablocki et al study is a good review of the anchorage enhancing effect (or lack of!) simple trans-palatal arches. I have always thought that if anchorage supplementation is really required using palatal arches, then a large Nance button covering most of the vertical part of the hard palate is going to maximise the chances of resisting mesial movement of molar teeth.

      I think this supposition was supported by the results of our recent RCT, which compared the anchorage value of Nance supported palatal arches, with the reference category of headgear. No clinically significant differences were found between the mesial molar movements using the two techniques.

      Bearing in mind these headgear patients were being studied under the most favourable possible conditions, being part of a RCT, and therefore there was likely to be a significant Hawthorne effect on this particular group, the Nance button really performed quite well.

  2. Bravo ! Very useful and well explained information. Of particular interest ,”We also found that the final occlusal result of treatment was better for the TAD group when compared to headgear. Another, and perhaps the most important finding, was that the patients reported less problems and concerns with TADS than Headgear.”

  3. Thank you for sharing your insider’s view of your recently published study. While I found value in the objective comparison of different types of anchorage, the questioning of patients about their experiences with headgear versus TADs was a forgone conclusion. One could compare headgear to anything and headgear would lose. The use of headgear in the practice of modern orthodontics is very limited, and in many practices, nonexistent. You failed to mention how patients reported their experiences with the Nance Holding Arch compared to TADs. That would be more “apples to apples”.

    • The comments received from the patients were recorded in full and reported in the original write up of the study. The comments written down by the patients about their experiences with the Nance supported Palatal arch were generally negative suggestive of tissue irritation under the Nance button, difficulties in cleaning, food packing and tissue trauma compared with the almost universally positive comments about TADs (Didn’t know the screw had been removed, after a couple of days couldn’t feel anything, worked well, comfortable, very impressive). Despite the overall flavour of the comments both these two groups were highly recommended as a method of anchorage supplementation by the patients who had received that particular treatment. This is in comparison to the markedly negative comments received from the headgear group where almost half the patients would not recommend the technique as a method of anchorage supplementation.

      Headgear has never been terribly popular with patients or with clinicians in the UK. One of the reasons for this is that, for the vast majority of patients treated here, treatment is free . . . therefore no ‘monetary value’ is attached to the treatment. As a consequence patients may be reluctant to do anything that they consider an imposition, or they perceive to be uncomfortable or involves a significant effort on their part. In a recent survey 60% of practitioners don’t regularly use Headgear and 20% never use Headgear (Banks et al 2010 J. Orthod : 37; 43-55) therefore other methods of anchorage supplementation are clearly necessary. The general perception in Europe is that headgear is still more accepted in the United States of America where a ‘higher value’ may be attached to orthodontic treatment.

  4. Hi Kevin,
    Very interesting trial and blog. Some thoughts:
    -I wondered after reading the paper at which location exactly were the miniscrews inserted and then I found Jonathan’s thesis electronically and got some info about that. Could you give some info about the clinician and insertion technique of the TADs? The failure rate was very low (although of course the number of inserted MIs was moderate).
    -If I remember correctly from an older AAO lecture of Jonathan, HG is not that popular an option in the UK and moderately tolerated? Any comment on the compliance or the generalizability of the trial’s results?
    -I had no idea (until I read the thesis) that the midpalatal implants had been discontinued. I would say this is positive. The somewhat higher stability was dearly bought both in tissue and patients discomfort.
    -The patient-reported outcomes were also very nice.
    -Likewise, the fact that you avoided extra x-rays for the evaluation of the treatment changes. In the upper arch, fortunately stable structures can be found for the superimposition. Can this also be used for the lower arch? I haven’t found any info about it… A couple of studies I read used the molars for the superimposition, but who says they remain stable? Also, now that I think about it, the superimposition of the upper jaw might be more problematic if the palatal implants together with supra-constructions for anchorage had been used in the palate?? Or not?
    Again, congratulations to the whole team for the nice research. Best regards,

  5. Thank you Spyros for your thoughtful comments.

    In all cases the TADs were placed using a buccal approach, in between the premolar tooth and the anchor molar tooth, wherever possible at the junction of the attached gingivae and the movable mucosa. Of course I am now familiar with your excellent Meta Analysis published in the AJODO 142,577-595.e7. which clearly shows this consideration is not a significant risk factor . . . ah . . . the benefit of hindsight!

    The upper and lower straight wire appliances were placed and an appointment was made for the extractions to be carried out by the General Dental Practitioner. The TADs were to be placed for anchorage supplementation, prior to straining the anchorage unit. In this group of cases no canine lacebacks were used from the molar bands and no initial canine retraction was performed in advance of TAD placement. Soon after the extraction sockets had healed the patients were booked in for placement of the TADs.

    If the patients were particularly nervous about TAD placement, they would first have some topical anaesthetic gel placed on the mucosa, immediately mesial to the molar tooth in the upper arch. A small amount of lignocaine was then carefully infiltrated into the reflected mucosa, immediately mesial to the molar tooth and this was digitally massaged into the tissues. A few minutes later, further anaesthetic was infiltrated and three or four minutes later the area was tested with a sharp probe to ensure complete soft tissue anaesthesia. A 2mm biopsy punch was then used to remove a small cylinder of mucosa, where possible at the junction of the attached and reflected mucosa.

    The 8mm x 1.6mm Aarhus screw was lifted from the screw rack in the Aarhus kit, using the custom made screwdriver. Using copious water irrigation and narrow bore suction the screw was gently but firmly screwed into place over a 60-90 second period. Water irrigation was continued throughout this period of screw placement. The TAD was tightened until there was minimal space between the collar and the mucosa and each screw was checked for primary stability. Occasionally undue resistance was felt as attempts were made to pierce the buccal plate of bone. In this situation the screw was removed and a site at least 2-3mm distant from the original site was selected for a subsequent attempt at screw placement.

    The TADs were loaded immediately via a 6mm NiTi coil spring that had metal ligatures attached to both ends. One ligature was threaded through an internal hole in the head of the screw and the other ligature tied around the bracket on the tooth to be distalised. A gentle pressure of 80-100gm was immediately applied from the TAD to the canine teeth that required distalisation.

    For compliance . . . see above comment in response to Dr Griffin Jr.

    As regards the generalizability I remember the comments by Professor Bob Lee at the EOS meeting in Iceland that “maybe the answer is for our patients is to enter them all into RCTs” . . . then we would get the incredibly useful ‘Hawthorne effect’ kicking in, which particularly in Headgear patients is so valuable. Certainly if we could engender the same amount of enthusiasm for treatment in our routine patients as we do in our Research patients a very different treatment outcome could be seen.

    There was a temporary discontinuation in the manufacture of the Straumann mid-palatal implants which sadly coincided with the publication of my previous RCT (Sandler et al. 2008 AJODO, 133, 51-57) which clearly demonstrated their usefulness! Their production has now been resumed and I believe they are now successfully used for anchorage supplementation. The placement and removal of these large osseointegrated implants is certainly a much bigger deal than the placement of TADs and involves more significant surgery.

    More recently palatal implants have had a significant resurgence in popularity largely championed by German orthodontists such as Bjorn Ludwig, Benedict Wilmes and Sebastian Baumgaertel. They have been show to be easy to place and remove and using a variety of plates and attachments can achieve all manner of tooth movements simultaneously.

    I agree that analysing cases using the above technique may prove to be problematic as the TADs are inserted in the region which is partially used for the superimposition (medial areas of the palatal rugae) and the plates cover the other area which has been shown to be stable (posterior part of the hard palate). Careful thought will have to be given to setting up a study that will allow reliable three dimensional monitoring of the effectiveness of this technique.

    As regards using the mandibular arch in 3D superimposition I refer you to Thiruvencatachari, B. (2008) A comparison of the effectiveness of the Twin Block and the Dynamax appliances for the treatment of Class II Division 1 malocclusion patients: A Randomised Controlled Trial. PhD Thesis, U.Manc


  6. Dear Jonathan,
    Thanks for the time you spent to respond.

    Thanks also for the complete details of your protocol. It was really interesting-especially as it was both clinically effective and with a very small implant failure rate.

    The compliance problem of course is a major thing with headgear. I read the recent paper in the Aug issue of AJO-DO about tracking electronically the wear-time of removable appliances by the patients. Maybe the same should be done also for headgear? Of course, we can always solve this by using compliance-free methods like TADs…

    I give it to you the Hawthorne effect could be of use. I still remember a study originating from the Dept. of Katherine Kula in USA in 2002 about “feigning” patient randomization into two groups and measuring the oral hygiene of ortho-patients. The “experimental” patients (or rather those who thought they were experimental) had significantly better hygiene the next 6 months of treatment…

    Personal bias: I still think the Strauman implant too costly (tissue-wise) for routine use. Plus, its only for the upper jaw and only from palatally.

    I am new to the literature about 3D model superimposition, however I really liked this method. Some more studies about the reliability of it would also be welcome. And again, as I commented above to Kevin, also liked the fact that you included patient outcomes to the trial.

    Again, congratulations for this excellent piece of research to you and the rest of the team!

    PS: do you happen to have a link of a repository or something like that where I can find the thesis of Dr. Thiruvenkatachari? I searched it in normal Google and Google Scholar, but could only find the published report in AJO-DO..

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