Methamphetamine (METH) is a sympathomimetic amine that belongs to phenethylamine and amphetamine class of psychoactive drugs, which are widely abused for their stimulant, euphoric, empathogenic, and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, METH produces persistent damage to dopamine and serotonin release in nerve terminals, gliosis, and apoptosis. This review summarized the numerous interdependent mechanisms including excessive dopamine, ubiquitin-proteasome system dysfunction, protein nitration, endoplasmic reticulum stress, p53 expression, inflammatory molecular, D3 receptor, microtubule deacetylation, and HIV-1 Tat protein that have been demonstrated to contribute to this damage. In addition, the feasible therapeutic strategies according to recent studies were also summarized ranging from drug and protein to gene level.

The aims of this study were to assess sensory recovery and impact on life quality after tongue reconstruction of oncological defects using different flap types. Thirty-two patients who underwent tongue reconstruction for oncological defects 9·3 months after surgery with non-innervated radial forearm free flaps (RFFFs) (N = 16), non-innervated anterolateral thigh free flaps (ALTFFs) (N = 8) and nasolabial island flaps (NLIFs) (N = 8), and 20 age- and gender-matched healthy controls participated in the study. The modalities assessed were cold detection threshold, warm detection threshold (WDT), cold pain threshold, heat pain threshold (HPT), mechanical detection threshold (MDT), mechanical pain threshold (MPT) and the Chinese version of Oral Health Impact Profile-49. ALTFFs was significantly more sensitive than RFFFs (P = 0·005) and NLIFs (P = 0·014) for WDT, and showed a better sensory recovery than RFFFs for HPT (P = 0·011). ALTFFs and NLIFs showed significantly better sensory recovery than RFFFs for MDT (P < 0·005). NLIFs showed the best sensory recovery for MPT, followed by ALTFFs and lastly RFFFs (P = 0·004). NLIFs also showed the least impact on quality of life measures related to psychological discomfort compared to RFFFs and ALTFFs (P < 0·019). All modalities of sensory recovery in RFFFs did not depend on gender and post-operative radiotherapy (P > 0·05). Different flaps for tongue reconstruction of oncological defects appear to have different patterns of sensory recovery and impact on quality of life measures. A longer follow-up period and larger number of participants will be needed in future studies.

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 non-treatment 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.