Wrong parameters in – no results out

By Jan Tunér

A comment on: Camila Haddad Leal de Godoy, Lara Jansiski Motta, Kristianne Porta Santos Fernandes et al. Effect of Low-Level Laser Therapy on Adolescents With Temporomandibular Disorder: A Blind Randomized Controlled Pilot Study. Journal of Oral and Maxillofacial Surgery volume 73, issue 4, year 2015, pp. 622 - 629

This study is a quite recent one and with a negative outcome. I only have the abstract available and have on purpose not checked the whole paper, because I believe in being quite clear in abstracts. Any why? Well, because the majority of persons ever checking on a study will only read the abstract on PubMed. So it is important to state all the pertinent parameters in the abstract. Omitting these details will leave the reader in the dark.

The first question is: Did the authors treat only the TMJ or did they treat the masticatory muscles? “TMD” generally means a muscular background, whereas arthritis in the TMJ (joint) is generally indicated as such. Some cases may have pain in the muscles and in the TMJ at the same time, but a proper reporting of the treatment target is necessary.

The second question is: Which muscular points were treated and how many? How often? From the Results section it seems that the muscles were targeted.

The third and most basic unresolved question is: If treating muscles, why use only 1 J per point? This is a very low energy for a muscle! Clinically I find at least 6 J needed to reduce the palpation pain and no less than 8 points, often 12. WALT recommendations are unclear in this case, suggesting 4 J, two points, so probably 2 + 2 J. For the TMJ this is fine, for muscles a waste of your time. The study is called a pilot study. Such studies are made in areas where there is uncertainty about optimal procedures. For TMD this is not the case, a lot is already known.

The fourth question is: Were the irradiated points chosen by individual palpation to find the most painful points, or were all patients treated according to a pre-set program? The latter program is better from a scientific point of view since it is standardized. But clinically less effective since each patient is different.

I understand that an abstract does not always allow authors more than a certain number of words, but if so, it is necessary that authors need to work on the text and make it possible for a PubMed reader to understand the study. In this case, we have a study bound for failure which will be quoted in future literature as negative. And quite probably without any comment on the reason for failure. This is harsh criticism, but I feel sorry for the fact that the authors have put a lot of effort into a study that was bound for failure from the start. Looking for better advice before the study started would have created something more useful.

Here is the abstract:

The aim of this pilot study was to evaluate the effect of low-level laser therapy on pain, mandibular movements, and occlusal contacts in adolescents and young adults with temporomandibular disorder. Individuals aged 14 to 23 years were evaluated. The Research Diagnostic Criteria for Temporomandibular Disorders were used for the diagnosis of temporomandibular disorders. Pain was assessed with a visual analog scale. Occlusal contacts were recorded using the T-Scan III program (Tekscan, Boston, MA). The participants were randomly allocated to 2 groups: active or placebo laser treatment. The laser parameters were as follows: wavelength of 780 nm, energy density of 33.5 J/cm2, power of 50 mW, power density of 1.67 W/cm2, and 20-second exposure time. The Kolmogorov-Smirnov test was used to determine the normality of the data distribution. The paired t test was used for the comparisons of the pretreatment and post-treatment results. The SPSS program for Windows (version 15.0; SPSS, Chicago, IL) was used for all analyses, with the level of significance set at 5% (P < .05).

No statistically significant differences between groups were found for the right and left anterior temporal muscles (P = .3801 and P = .5595, respectively), superior masseter muscles (P = 087 and P = .1969, respectively), medial masseter muscles (P = .2241 and P = .076, respectively), or inferior masseter muscles (P = .5589 and P = .3268, respectively) after treatment.

No statistically significant differences were found regarding pain, mandibular range of motion, or the distribution of occlusal contacts after treatment with low-level laser therapy. These preliminary results need to be verified in a larger sample of patients to confirm the lack of response to low-level laser therapy.