An occasionally irregular blog about orthodontics

Do lingual appliances reduce orthodontic decalcification?

By on September 14, 2015 in Clinical Research, Recent posts with 12 Comments
Do lingual appliances reduce orthodontic decalcification?

Do lingual appliances reduce orthodontic decalcification?

Most followers of this blog will know that I tend to confine my posts to discussing clinical trials. However, very occasionally someone publishes a retrospective investigation that provides clinically interesting information, that my lead to a question that can be tested in a trial. This paper on the incidence of white spot lesions during lingual appliance treatment is one.

Do lingual appliances reduce decalcifationLingual appliances reduce the incidence of white spot lesions during orthodontic multi bracket treatment.

Dirk Weichmann et al

AJO-DDO 2015: 148; 414-22.



In the introduction, the authors point out that visible white spot lesions particularly on the maxillary teeth are a concern. I have discussed the prevention of this problem in previous blogs. They put forward the suggestion that the use of lingual appliances may reduce decalcification because it occurs less frequently on the lingual surfaces of teeth. Furthermore, they will not be visible. As a result, they carried out a study to assess the incidence of white spot lesions in patients treated with lingual appliances. This also appeared to be follow up study to a paper published in 2014 in Head and Face medicine.  The authors also featured on the AJO-DDO video stream and you can see Professor Knossel describe the study here.

What did they do?

This was a retrospective single centre study in which they collected records on 174 patients, out of a possible sample of 214, who had been treated from June 1, 2011 to May 31, 2014 in one orthodontic Centre. They applied the following inclusion criteria for the patients:

  • Upper and lower lingual appliance treatment
  • Aged less than 18 years old
  • The treatment was complete
  • They had high quality initial and final photographs

They also recorded the patients age, gender, and duration of treatment. As part of their treatment the patients underwent an intensive oral hygiene and preventative regime. The data was collected by one assessor who assessed the presence, or absence, of white spot lesions The statistical analysis was appropriate.

What did they find?

They found that the main duration of treatment was 19 months. The global incidence of new white spot lesions was 3.19% Interestingly, 41.9% of the patients were affected by at least one new white spot lesion There was no effect of age.

In the discussion they drew attention to the fact that this was a very large sample size. They also pointed out that when they considered the maxillary incisor teeth the subject related incidents of at least one new white spot lesion was 10.5%, whereas in other studies of labial appliances this was as high as 60%. They also mentioned that they excluded just under 6% of the teeth because they could not be visualised well on the photograph.

They went into a long section of the discussion about the validity of their method compared with other methods used in previous studies. I actually thought that their method was simple, straightforward and reflected the real world situation of recording visible decalcification. They concluded that orthodontic treatment with customised lingual fixed appliances can significantly reduce incipient carious lesions.

What did I think?

When we interpret this study, we need to consider that it is retrospective. As a result, there is a high risk of selection bias. The authors addressed this by describing in great detail how they derived their sample and made particular reference to those cases that they excluded. We, therefore, need to consider that this sample was 174/214 possible patients. This represents a subject loss of just under 20%. It was not clear why these patients were not included in in the sample. It may be that some of these did not have high compliance and were at greater risk of decalcification than those who were included. So we need to bear this in mind when we interpret their findings.

My other concern, which some may not considered to be relevant, is that these patients were treated in one orthodontic Centre which is very well-known to have very high clinical standards. This may not be true in the other study centres with which they have made comparisons.

I have also tried to think about why there was potentially less decalcification.  This may be due to  the design of the bracket. These were customised for the patient and the bracket base covers a larger area of the tooth than standard buccal appliances. As a result, they may have a preventative effect because of this increased closely fitting coverage. Furthermore, the lingual surfaces of the teeth are more self cleansing than the buccal because of the action of the tongue and salivary flow.

Another potential advantage of lingual brackets is that if decalcification occurs and the enamel is not compromised the White spots can be left untreated, as they will not be visible.

In summary, I think this was a really interesting study and it certainly points us in the direction of further research into the advantages of lingual appliances. I would really like to see someone carry out a trial in which patients they randomised patients to have treatment with either lingual or labial appliances.
Wiechmann, D., Klang, E., Helms, H., & Knösel, M. (2015). Lingual appliances reduce the incidence of white spot lesions during orthodontic multibracket treatment American Journal of Orthodontics and Dentofacial Orthopedics, 148 (3), 414-422 DOI: 10.1016/j.ajodo.2015.05.015

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  1. Hello Kevin. As always thank you for your blog and making us think!
    I am not sure if you are aware of this article published in European Journal of Oral Sciences (Volume 118, Issue 3, pages 298–303, June 2010) Caries outcomes after orthodontic treatment with fixed appliances: do lingual brackets make a difference? by M. H. Van Der Veen, R. Attin, R. Schwestka-Polly and D. Wiechmann? I think it augments your review of the above article quite nicely. Here they have done just what you wished for– a split mouth study of labial and lingual treatments, non-prospective and randomized for whom receives each type of appliance and which arch, with qualitative and quantitative evaluations for WSLs. The patients were also treated in the same single, high-quality office as the study you have reviewed removing the issue of possible clinical differences. (
    In the article they find almost 5x less chance of WSLs on the lingual versus labial surfaces and almost 10x less loss of enamel matrix on the lingual versus labial surfaces. In my opinion, this is data that is hard to argue with as having been something other than less WSLs due to lingual treatment.
    In your review of the new AJO-DO article I would argue that the enlarged size of lingual appliances does not sway the outcome as suggested. The bracket pads on lingual appliances are large for retention of the bracket and the size of the bracket pads were not enlarged for this study. Even with lingual appliances, there are still bracket pad margins to decalcify with lingual brackets but somehow they didn’t decalcify as much. Your argument could be construed as a bit like arguing that the fastest track athlete should not be compared to an amateur athlete because the faster athlete has the advantage of being fast. Instead I would suggest there is some self-cleansing effect from the tongue and the additional saliva wash on lingual surfaces. In addition, it is important to note that WSLs on the lingual surfaces that do not penetrate the enamel do not require treatment and are then clinically insignificant. Labial counterparts to this still require treatment to hide the WSL if they are not to be seen. Thanks again Kevin.

    • Kevin O'Brien says:

      Thanks for the comments. I have added a couple of paragraphs on the siting of the WSL and the lingual salivary flow. I have also rewritten the section that you referred to, because I was not making my point clearly.

    • Kevin O'Brien says:

      Thanks, I have changed the text of the posting and I will look up the trial that you mentioned and re-visit it

  2. Dear Dr. O’Brien,

    Thank you for the in-depth ctritic of this article. As you mentioned matters of study methods like attrition of group under study, selection bias, control group and randomisation – points that I agree with totally –, it came to my mind that there was a pro and contra debate on RCTs in orthodontics in the last EJO. In the contra part Meikle’s contention from an editorial written in 2005 is cited even two times: ‘if one asks whether RCTs have achieved their intended objective, or provided knowledge not previously available from retrospective studies or animal experimentation, the answer would have to be no’.
    I would be glad if you could write an adequate reply to such an incredible nonsense. Orthodontics may lag far behind scientific standards set in medicine, but in this way we make ourselves ridiculous.

    • Kevin O'Brien says:

      Thanks for the quick response. I have read the paper in the EJO and found it very disappointing. You have reminded me that I need to return to it and write a blog post. I will do this and post in the next four weeks.

      • Henning Madsen says:

        …the blog post is welcome, but a letter to the EJO would be very useful as well! Of course many critical aspects can be said about RCTs in general, an some of these Sabine Ruf points out correctly (difference between efficacy and efficiency, Hawthorne effect) etc.), but finally she throws out the baby with the bathwater.

        • Kevin O'Brien says:

          I thought about a letter but the EJO is not too widely read. I think that this blog is read more times and this could have a greater effect?

  3. Sorry, the article I mentioned was not printed in the last EJO, instead it is EJO advance access published online in July 2015:


  4. Anand Srinivasa says:

    Dear Dr. O’Brien,

    It is a very interesting topic and one which would benefit from a randomised trial. I do agree that constant salivary flow and cleansing action of the tongue could be beneficial, however there are a many other variables such as shorter inter bracket distances lingually especially anterior teeth, inability to directly visualise the lingual surface in the anterior region which many of my patients have commented on with regards to hygiene. Lingual appliances are here to stay and are getting more popular with time, it would not be a bad idea to have a few randomised studies on how they rate next to labial appliances with regards to hygiene maintainence. Once again thank you for an interesting Blog

  5. Robert "Bob" Stoner says:

    I cannot achieve my treatment objectives routinely with lingual appliances. Therefore, the study is irrelevant to me.

  6. Michael Knösel says:

    Thank you for very much for this post. I am very happy to see our paper being discussed in your blog as I welcome any discussion as positive.
    However, I would like to address your uncertainty towards „why these (40) patients were not included in in the sample. It may be that some of these did not have high compliance and were at greater risk of decalcification than those who were included. So we need to bear this in mind when we interpret their findings“.

    We gave the reason for exclusion of these 40 patients in the paper: „Accordingly, of the 214 potentially eligible subjects, 40 (18.69%) were excluded from analysis because they were 18 years of age or older.“
    Furthermore, it is stated that „the reason for excluding subjects in that age group was to match the samples from previous studies of WSL formation in patients treated with conventional labial appliances without creating a bias toward reduced formation of WSL by including subjects who are potentially less susceptible to WSL formation because of their age“ (This refers to Enaia et al., AJODO 2011). It was suggested that „a majority of the patients in our sample were characterized by even more pronounced caries activity and susceptibility, and a higher risk for WSLs, because of their young age (mean, 14.35 years)“, referring to Chapman et al., AJODO 2010. Therefore, the incidence of postorthodontic lingual WSLs may be expected to be even more reduced in a sample with a greater mean age“.
    That is, the exclusion of older patients was made in an attempt to avoid the accusation of having intentionally reduced decalcification incidences by combining patients with low- and high risk of caries activities.

    What may also be relevant in comparing study findings with those of others is the fact that we did not exclude a single patient for the reason of incomplete documentation. Exclusion of such is a common side note in a number of studies, and clinicians know well that incomplete documentation often equals ’lack of compliance’, or end of trearment ahead of schedule due to lack of oral hygiene. It is a factor that is commonly not given too much attention during study evaluations, but one that is highly underestimated in terms of the impact on results, and worth to be discussed, from my point of view.

    Concerning your other remark that „these patients were treated in one orthodontic Centre which is very well-known to have very high clinical standards. This may not be true in the other study centres with which they have made comparisons“, I would like to point out to the fact that the three major studies we were comparing our results to collected their samples at the Department of Orthodontics, Universitiy of Giessen (Enaia et al.), the graduate orthodontic clinic at the University of Michigan School of Dentistry (Richter et al.), and the Department of Orthodontics of the Virginia Commonwealth University (Tüfkci et al.). Although I cannot judge the quality of treatment standards that apply in those centers, it would be my strong assumption that they are providing an excellent level of healthcare.

    Overall, our point is that the lingual technique represents an opportunity to augment and improve our orthodontic therapeutic measures, and also proactively addresses the concerns of non-orthodontists and (what I perceive) of an increasing number of pediatric dentists who may claim a high incidence of WSL as counter-argument to fixed orthodontic treatment, or orthodontics, in general.
    So it is my personal opinion that this approach may be helpful for our specialty, whether you use the lingual technique, or not.

    Thanks, again, for your post.

    Best wishes from Germany,


    • Kevin O'Brien says:

      HI Michael, thanks for the comments. Sorry for the error in not spotting the exclusion criteria for the patients in the study. I simply did not follow the text too well. My other comments on the excellence of the treatment centre were really directed towards other providers of treatment, for example, the average high street specialist practice. This is not a reflection of the overall standard of orthodontic treatment but a feeling that oral hygiene etc may not be as good as in a practice that is well known for provding high quality lingual orthodontics. This whole area is really interesting and your study is a real contribution
      Best wishes: Kevin

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