Temporomandibular disorders (TMD) are a series of diseases which affect the masticatory system including temporomandibular joint (TMJ). Low reactive-level laser therapy (LLLT) has beenr eported as having good effects in various joint related pains and conditions. In this study, a suitable LLLT treatment protocol was proposed and the preliminary outcome was demonstrated in a short-term period of follow-up. Thirty (2 men and 28 women) patients with TMD who did not respond to initial conservative therapy were enrolled. The patients were divided into three groups according to their clinical signs, symptoms, and imaging modalities: disk derangement with clicking (DDC), disk derangement with locking (DDL), and osteoarthritis (OA). Low level laser therapy (LLLT) was administrated using a pulsed Nd:YAG laser at an output of 2.8 Watts and 20 pps. The treatment was started by bilaterally irradiating the C1/C2 zone, followed by irradiation of the TMJ area on the affected side. Subsequent treatment was given at intervals of 1 or 2 weeks for a total of two to five sessions. Although LLLT with the pulsed Nd:YAG laser significantly decreased pain in general, some patients, especially those in the DDL group, experienced little decrease in pain. Mean vertical maximal mouth opening increased from 36.8 to 40 mm. However, LLLT did not substantially improve maximal mouth opening in patients with severe impairment of mouth opening (i.e. closed lock). In total, LLLT was effective in 21 of 30 (70 %) of the subjects. The results suggest that LLLT at the wavelength and parameters used in the present study is somewhat effective for reducing pain in the TMJ area, but produces little improvement in mouth opening in patients with closed lock. The degree of efficacy, however, warrants the investigation of other wavelengths and parameters for LLLT for TMD.

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Many studies, using low level laser irradiation (LLLI), have been performed to investigate the influence of laser irradiation on the healing process of wounds or lesions. It has been proposed that the low incident levels of laser irradiation may stimulate the growth of bacterial cells and normal tissue cells. This study was performed to determine whether LLLI has a promotive effect on the healing of experimentally infected wounds and which irradiation type has the more promotive healing effect in the rat model. The most and least proliferative pulses found effective in a previous study were used in this study. The laser was a pulsed gallium arsenide (GaAs) semiconductor laser with a wavelength of 904 nm. The incident average powers were 1 mW and 10 mW. Circular, full-thickness skin defects measuring about 6 mm in diameter were produced on the gluteus superficialis of both hind limb in each rat. Staphylococcus aureus was inoculated on the wounds. In addition to comparing the two pulsing frequencies, irradiation around the periphery of the wound was compared with irradiation of the wound bed. The wound contraction rate was measured after irradiation accoring to irradiation and pulse types. There was a significant increase in wound contraction rates in the irradiation groups for both pulse types compared with the unirradiated contralateral control wounds. Comparing the healing effects of peripheral and wound bed irradiation, however, there was no significant difference between the effects of the two irradiation types.

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To identify any gene whose expression is enhanced by irradiation with low incident levels of laser energy, we previously constructed the cDNA library of the osteoblastic cell line MC3T3-E1, using a stepwise subtraction procedure between cells with and without laser irradiation. In the present study, we focused on one cDNA clone, designated as MCL-60. Our preliminary sequencing experiment indicated that this clone exhibited high homology with the gene coding for mouse CDC46 (cell division cycle 46 gene which is involved in the initiation of DNA replication of eukaryotic cells. To confirm the gene product, the DNA sequence of the cDNA clone MCL-60 was determined and assessed in the GenBank and EMBL nucleic acid databases. The transcription level of the cDNA clone MCL-60 wag examined by Northern blot analysis. The DNA sequence of clone MCL-60 exhibited 99.6% homology with that of CDC46 /MCM5 (minichromosome maintenance 5), and the deduced amino acid sequence exhibited 100% homology. Higher CDC46 mRNA levels were observed in laser irradiated cells compared to the levels in non-irradiated cells. Furthermore, DNA synthesis was increased by laser irradiation. These findings suggest that low incident levels of laser irradiation may play a principal role in stimulating proliferation of osteoblasts with enhancement of the gene expression of CDC46.

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We report on a 130 month retrospective study of pain entities treated with 830 nm diode laser therapy carried out at the authors' clinic. In 11,139 mostly chronic pain patients (M:F 1:1.5) presenting with a total of 19,275 symptoms, an overall efficacy rate of 82 ± 5.7% was achieved (mean ± standard error of deviation, range of efficacy, 67.8% ∼ 88.9%). The results were recorded under five grades: excellent (total pain removal, no recurrence, >9 point improvement on 11 point visual analogue scale [VAS] score); good (very noticeable attenuation, little or no regression, > 7 point improvement on VAS); fair (some improvement, some recurrence, >5 point improvement on VAS); unchanged (little or no improvement, <4 point improvement on VAS); and poor (exacerbation of pain). The overall efficacy was achieved by adding the ‘excellent ’ and ‘good ’ scores, i.e. a minimum of > 7 VAS points, thereby possibly removing some of the ‘placebo effect ’. The efficary rate of 82% for low level laser therapy (LLLT) in chronic pain entities is consistent with previous reports from the authors and others. Only one patient in the entire study reported exacerbation of their symptoms. While recognizing that this is not a ‘scientific ’ controlled study, the authors suggest that the stringent criteria used to calculate the overall efficacy, the large patient population and clearly delineated pain entities lend strong credence to the data. In any event, as general practitioners, the authors firmly believe that the placebo effect may well be a useful component of laser therapy, always provided it is an effect which can be maintained and improved on by the actual documented physiological effects attributed to laser therapy. LLLT using a diode laser at 60 mW, 830 nm, continuous wave, in the contact pressure technique as used in the study, is therefore considered as a safe, effective and side effect free adjunctive therapeutic modality for intractable chronic and other pain types. However, in addition to intense training and continuing education for the therapists, their clinical environment and motivation are also important components in achieving consistently excellent therapeutic results in LLLT for pain attenuation in the private clinic.

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The indication of the laser in therapeutic applications has increased dramatically during the last decade, and particularly significantly during the last few years. With the increase of indications has come a concomitant increase in possible classification of laser reactions. The author presents a classification which is based on the laser/tissue reaction. when the level of tissue reactivity to very low incident power and energy densities is well below the cells’ damage threshold so that instead of being damaged the cells are directly activated by the low incident photon density, the changes in the irradiated tissue are photoactivative and reversible: the author refers to this group of reactions as low reactive-level laser therapy (LLLT), or more generally as laser therapy. LLLT is further subdivided into three main types: mono-type LLLT (Mo-LLLT, single laser therapy; multi-type LLLT (Mu-LLLT, multi-laser therapy); and concomitant LLLT (Cc-LLLT), in which any of the above LLLT types can be used in combination with conventional treatment methods. Mo-LLLT in turn contains pure LLLT (Pu-LLLT), single laser, single reaction; and auto-simultaneous LLLT (ASi-LLLT), single laser with a range of reaction types, each of which has its own abbreviation. Mu-LLLT contains two main sub-types, combined LLLT (Cb-LLLT) and compound LLLT (Cp-LLLT). Cb-LLLT concerns the same condition whereas Cp-LLLT is used to describe 2 or more conditions treated with the same or different lasers. Both Cb-LLLT and Cp-LLLT are further subclassified into the homogeneous and xenogeneous types, referring to the use of the same or different types of laser, respectively. If the lasers are applied at the same time, that is homo- or xeno-simultaneous laser therapy (HoSi-LLLT, XeSi-LLLT), and if at different times the term is homo- or xeno-succesive LLLT (HoSu-LLLT, XeSu-LLLT). The various sub-sets of Mono-type and Multi-type laser therapy are further expanded, to give an accurate, treatment-based categorization of LLLT. When the above classification is understood and used, the author feels this offers an accurate and simple method of classifying laser/tissue reactions by the reaction, rather than by the laser used to produce the reaction.

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