Effect of low-level laser therapy on tooth-related pain and somatosensory function evoked by orthodontic treatment

Low-level laser therapy(LLLT) may have an effect on the pain associated with orthodontic treatment. The aim of this study was to evaluate the effect of LLLT on pain and somatosensory sensitization induced by orthodontic treatment. Forty individuals(12–33 years old; mean ± standard deviations: 20.8 ± 5.9 years) scheduled to receive orthodontic treatment were randomly divided into a laser group(LG) or a placebo group(PG)(1:1). The LG received LLLT(810-nm gallium-aluminium-arsenic diode laser in continuous mode with the power set at 400 mW, 2 J·cm–2) at 0 h, 2 h, 24 h, 4 d, and 7 d after treatment, and the PG received inactive treatment at the same time points. In both groups, the non-treated side served as a control. A numerical rating scale(NRS) of pain, pressure pain thresholds(PPTs), cold detection thresholds(CDTs), warmth detection thresholds(WDTs), cold pain thresholds(CPTs), and heat pain thresholds(HPTs) were tested on both sides at the gingiva and canine tooth and on the hand. The data were analysed by a repeated measures analysis of variance(ANOVA). The NRS pain scores were significantly lower in the LG group(P = 0.01). The CDTs,CPTs, WDTs, HPTs, and PPTs at the gingiva and the PPTs at the canine tooth were significantly less sensitive on the treatment side of the LG compared with that of the PG(P < 0.033). The parameters tested also showed significantly less sensitivity on the nontreatment side of the LG compared to that of the PG(P < 0.043). There were no differences between the groups for any quantitative sensory testing(QST) measures of the hand. The application of LLLT appears to reduce the pain and sensitivity of the tooth and gingiva associated with orthodontic treatment and may have contralateral effects within the trigeminal system but no generalized QST effects. Thus, the present study indicated a significant analgesia effect of LLLT application during orthodontic treatment.Further clinical applications are suggested.

The effect of depression on the thermal nociceptive thresholds in rats with spontaneous pain

Objective Recently,there has been growing interest in the interaction between depressive disorders and pain.The purpose of this study was to examine whether depression would lead to a decreased sensitivity to noxious stimuli in rats with spontaneous pain.Methods The olfactory bulbectomized rats were used as a model of depression.The depression-like behaviors were assessed by open field test and changes in body weight.Formalin solution was injected into the rat hindpaw to produce ongoing pain.Noxious thermal stimuli were applied onto the hindpaw contralateral to formalin injection,and the withdrawal thresholds were measured.Results In non-depressive rats,the formalin-treated paw developed hypoalgesia to noxious stimuli while the contralateral paw was not affected.The depressive rats,however,showed a significantly lower sensitivity to noxious thermal stimulus,represented as higher withdrawal thresholds of the contralateral paw,when compared to the non-depressive rats.Conclusion These results demonstrate that depression can alleviate the stimulus-evoked pain even in the context of formalin inflammatory pain,consistent with the previous clinical observations that patients suffering from both depression and persistent pain have decreased sensitivities to noxious experimental stimuli.