A study of the influence of low intensity laser therapy on painful temporomandibular disorders

Abstract

An analgesic effect is one of the reported results of Low Intensity Laser Therapy (LILT). Even though this therapy has been extensively used to treat musculoskeletal injury, pain and inflammation, there is still a lack of research concerning the ideal parameters and mechanism of action of LILT on painful Temporomandibular Disorders (TMD). This thesis sets out to compare clinical responses to the 820 nm Gallium Aluminium. Arsenide (GaAlAs) laser at two energy levels and placebo laser in TMD Pain patients. Additionally, in vitro studies were conducted to explore the effect of 820 nM radiation on Prostaglandin E2 (PGE2) production by myoblast cultures undergoing stretching and stimulation by Interleukin I alpha (IL-1). A double-blind clinical trial was conducted on 30 female TMD pain patients. The patients were randomly allocated into three groups based on LILT regimes namely 820 nm GaAlAs at energy density of 21 and 107 J/cml and placebo laser. Each patient had three LILT treatments in a week. The pressure pain threshold (PPT) of trigger points in masticatory muscles, unassisted maximum mouth opening without pain (MOSP) and symptom severity index (SSI) were recorded as baseline data and monitored after every treatment. jaw kinesiology and electromyography (EMG) were also recorded as baseline and final results. The analysis of covariance and the further analysis showed that the higher energy density laser group had significant increases in PPT and EMG amplitude recorded from voluntary clenching (cEMG) compared with the placebo group at P values 0.0001 and 0.022 respectively. A significantly greater number of patients recovered from myofascial. pain and TMJ arthralgia as assessed clinically in the higher energy group compared with the placebo (P value = 0.012 and 0.001 respectively). There was no statistically significant difference of parameters of assessment among the groups at aP value 0.05. At a period of 2 to 4 weeks review after LILT, there was an average 52% reduction of pain as assessed by SSI pain questionnaire. The control in vitro studies on the influence of LELT on PGE2 production were conducted on differentiated C202 skeletal muscle cells stimulated by mechanical stretching and IL-I supplement. The two models of PGE2 stimulation showed significantly higher amounts of PGE2 production compared with the no intervention group. The results from the model using mechanical stretching to stimulate PGE2 synthesis showed no inhibitory effect from 820 nm GaAlAs laser at least in the energy densities used in this study which were 0.6 J/CM2 and 3.1 J/cmI. In the other experiment, IL-1 supplement was used to stimulate PGE2 which was observed to occur in the sham laser and lower energy laser at 4 J/CM2 groups. However, the higher energy laser group at 19 J/cm' showed reduced PGE2 synthesis with no statistically significant difference from a no intervention group where no IL-1 was added. This indicates that 820 nm radiation at higher energy density appears capable of inhibiting PGE2 formation and this may be one of the mechanisms of the analgesic effect of GaAlAs LILT on trigger points in muscle. Overall Low Intensity Laser Therapy (LILT) given at high energy density has been shown to be a valuable addition to the repertoire of treatment methods for Temporomandibular Pain Disorder.