TMD and lasers – why the conflicting results? A very personal review

By Jan Tunér

The literature is the area of treating temporomandibular disorders (TMD) is rather numerous but still rather poor. In this article, some explanations will be presented and a suggestion for future improvement as well. Uniquely, no references will be listed and no names dropped. No use crying over spilled milk.

At first, let us consider the indication “TMD”. What does it mean? “Disorders” in a system comprising two joints, many muscles, many teeth and an owner reacting to tension in this area according to his physiological and psychological status. Could LPT “cure” any such combination of backgrounds? The simple answer is no. And honestly, no other single therapeutic modality is perfect. But why then, is LPT not readily accepted as a useful tool in this multifactorial condition?

Let me list a number of reasons for failures in the literature:

  • Too many papers have misunderstood the fundamental difference between “dose” (J/cm2) and “energy” (joules). Believe me, I have reviewed several rejected papers… Here are a few examples: Group A applied 6.3 J/cm2 in a study and quoted Group B as using 3.5 J/cm2. But Group A used 0.3 J per point and Group B 6 J per point! That is obvious after checking the parameters of Group A but not obvious for the casual reader. What seemed to be high was actually very low. The “high” dose is obtained just by using a thin laser probe. Reporting the dose only leads the reader wrong. Group C stated parameters: 904 nm, 17 mW, 1000 Hz, 180 seconds, 3 J, 3 J/cm2. The stated dose can only be correct provided that the laser aperture was one cm2, which it most probably was not. Group D states 500 mW, 20 s, 4 J/point, but 500 x 20 = 10 J.
  • While on energy and dose: What does WALT say? 4 J, 1-2 points. But this is obviously for TMJD (temporomandibular JOINT disorders). The joint is a small and superficial structure. So quite enough. What about the most common feature in TMD – painful muscles? The closest similar condition in the WALT recommendations could be for the biceps humeri – recommendation 6 J. Per point, that is, not in total.
  • Don’t believe everything that you read. An author from the late 90s claimed that HeNe (632.8 nm) has the best penetration into muscles. Doesn’t have to be true (and it isn’t) just because someone published it. But it was recently quoted.
  • So what about the diagnosis? Is it muscular or is it arthralgia – or both? Goes together like a horse and carriage if there is an inflammatory erosion in the TMJ. So then this latter condition should be attended to first. LPT studies claiming arthralgia should have an X-ray confirmation about the condition of the joint. TMD is multifactorial and each patient is different. Thus the problem of finding a homogenic group for research with a pre-set protocol.
  • Now the muscles. They are many and their involvement can only be found by a thorough palpation. The outcome of the palpation can lead the dentist to a treatment plan. Could include a bite splint, a recommendation to visit a physiotherapist or even a psychologist. The lateral pterygoids are seldom seen in LPT papers on TMD. And the neck?
  • Palpation: how many points? Some authors have selected a limited number of points, generally the tenderest points. Could be a good set-up but there are many muscles!
  • What about NSAIDs? A preliminary palpation procedure can of course be performed, but before a therapy program is decided upon, the patient should stop all consumption of analgesics. The analgesics will “hide” the tender points and possibly limit the biological effect of LPT.
  • In a scientific situation an energy per point has to be pre-determined and followed. But clinically, the best method is to palpate the tender point, irradiate a tentative energy (3-6 J) and re-palpate. If the patient still experiences the same level of pain, add another irradiation on the same point. The goal is not to remove the palpation pain. As soon as the patient confirms that the palpation pain is clearly reduced, we have irradiated enough on that point. The aim is to start a process, not to dumb a muscle for a while. Anything from 3 to 12 J can be needed to satisfy this ambition.
  • 50 or 500 mW? Both will work, if infrared. 50 takes time, but the long duration of irradiation has biological advantages. But too slow for my personal liking. But as always, when people ask “Which laser should I use?” my answer is “The one that you have”.

So, 9 negative points. Where are the positive ones? Only one: Read the 9 points and don’t make the same mistakes. LPT is an excellent adjunct method to use in TMD therapy.

It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.
(Mark Twain)