Background
Quantification of motor‐evoked potentials (MEPs) can contribute to better elucidate the central modulation of motor pathways in response to nociceptive inputs. The primary aim of this ...study was to assess the modulatory effects of nerve growth factor (NGF) injection on masseter corticomotor excitability.
Methods
The healthy participants of this randomized, double blind placebo‐controlled experiment were assigned to have injected into the right masseter muscle either NGF (n = 25) or isotonic saline (IS, n = 17). The following variables were assessed at baseline and 48 hr after the injection: right masseter MEP amplitude and corticomotor mapping and clinical assessment of jaw pain intensity and function. Repeated Measures ANOVA was applied to the data.
Results
NGF caused jaw pain and increased jaw functional disability after the injection (p < 0.050). Also, the participants in the NGF group decreased the MEP amplitude (p < 0.001) but the IS group did not present any significant modulation after the injection (p > 0.050). Likewise, the participants in the NGF group reduced corticomotor map area and volume (p < 0.001), but the IS group did not show any significant corticomotor mapping changes after the injection (p > 0.050). Finally, there was a significant correlation between the magnitude of decreased corticomotor excitability and jaw pain intensity on chewing 48 hr after the NGF injection (r = −0.51, p = 0.009).
Conclusion
NGF‐induced masseter muscle soreness can significantly reduce jaw muscle corticomotor excitability, which in turn is associated with lower jaw pain intensity and substantiates the occurrence of central changes that most likely aim to protect the musculoskeletal orofacial structures.
Significance
Intramuscular administration of nerve growth factor into masseter muscle causes inhibitory corticomotor plasticity, which likely occurs to prevent further damage and seems associated with lower pain intensity on function.
: We examined the antioxidant properties in vitro and the antinociceptive effect of carvacrol (CARV) in several models of pain in mice. CARV presented a strong antioxidant potential according to the ...TRAP/TAR evaluation; it also presented scavenger activity against nitric oxide and prevented lipid peroxidation in vitro. In mice, when evaluated against acetic acid‐induced abdominal writhing, CARV (25, 50 and 100 mg/kg, i.p.) reduced (p < 0.001) the number of writhing compared to the control group, without opioid participation. In the formalin test, CARV also significantly inhibited both the early (neurogenic pain) and the late (inflammatory pain) phases of formalin‐induced licking, with inhibition percentage values of 56.8% (100 mg/kg) for the neurogenic phase and 41.2% (25 mg/kg), 73.8% (50 mg/kg) and 99.7% (100 mg/kg) for the inflammatory phase. CARV also produced a significant inhibition of the pain caused by capsaicin (63.1, 67.1 and 95.8%, p < 0.001) and glutamate (46.4, 61.4 and 97.9%, p < 0.01). When assessed in a thermal model of pain, CARV (100 mg/kg, i.p.) caused a significant increase (p < 0.05) in the latency response on the hot‐plate test. Such results were unlikely to be provoked by motor abnormality. Together, these results indicate that the properties of CARV should be more thoroughly examined in order to achieve newer tools for management and/or treatment of painful conditions, including those related to pro‐oxidant states.
Aim
This critical review describes key methodological aspects for a successful oro‐facial psychophysical evaluation of the somatosensory system and highlights the diagnostic value of somatosensory ...assessment and management perspectives based on somatosensory profiling.
Methods
This topical review was based on a non‐systematic search for studies about somatosensory evaluation in oro‐facial pain in PubMed and Embase.
Results
The recent progress regarding the psychophysical evaluation of somatosensory function was largely possible due to the development and application of valid, reliable and standardised psychophysical methods. Qualitative sensory testing may be useful as a screening tool to rule out relevant somatosensory abnormalities. Nevertheless, the patient should preferably be referred to a more comprehensive assessment with the quantitative sensory testing battery if confirmation of somatosensory abnormalities is necessary. Moreover, the identification of relevant somatosensory alterations in chronic pain disorders that do not fulfil the current criteria to be regarded as neuropathic has also increased the usefulness of somatosensory evaluation as a feasible method to better characterise the patients and perhaps elucidate some underpinnings of the so‐called ‘nociplastic’ pain disorders. Finally, an additional benefit of oro‐facial pain treatment based on somatosensory profiling still needs to be demonstrated and convincing evidence of somatosensory findings as predictors of treatment efficacy in chronic oro‐facial pain awaits further studies.
Conclusion
Psychophysical evaluation of somatosensory function in oro‐facial pain is still in its infancy but with a clear potential to continue to improve the assessment, diagnosis and management of oro‐facial pain patients.
This study aimed to evaluate the influence of the frequency of rhythmic masticatory muscle activity per hour (RMMA/h) scored by polysomnography (PSG) recordings on sleep-related factors and orofacial ...pain symptoms.
According to RMMA/h frequency, participants were assigned either to the control group (i.e., CRMMA, n = 40); or the case group according to high (i.e., HRMMA, n = 12) or low (LRMMA, n = 28) RMMA/h frequency. Fisher's exact (nominal variables), One-way Analysis of Variance followed by post-hoc Tukey (continuous variables) and Poisson Regression tests were used to calculate orofacial pain symptoms and sleep-related breathing, behavior, and architecture differences between controls versus cases at a significance level of 5%.
The CRMMA differed from HRMMA and LRMMA subgroups considering orofacial pain, self-reported tooth clenching or grinding, obstructive sleep apnea (OSA), snoring, and most variables considering sleep architecture (P ≤ 0.05). Multivariate adjusted Poisson regression analysis revealed that bruxers, regardless of RMMA/h frequency, presented a significantly higher prevalence rate (PR) related to orofacial pain (PR 1.68; P = 0.025) and self-reported behavior (PR 1.71; P = 0.012).
Significant differences in N1, N2 and N3 stages, arousals, arousal per hour, and sleep onset latency variables were found comparing bruxer with high or low RMMA/h frequency. Compared to controls, bruxers presented higher PR related to headache and self-reported tooth clenching or grinding.
•Bruxers significantly differed from controls considering headache.•Bruxers significantly differed from controls considering sleep-related factors.•Bruxers presented a higher prevalence ratio related to orofacial pain upon waking.
The aim of this investigation was to evaluate the effects of local anaesthesia on nerve growth factor (NGF) induced masseter hyperalgesia. Healthy participants randomly received an injection into the ...right masseter muscle of either isotonic saline (IS) given as a single injection (n = 15) or an injection of NGF (n = 30) followed by a second injection of lidocaine (NGF + lidocaine; n = 15) or IS (NGF + IS; n = 15) in the same muscle 48 h later. Mechanical sensitivity scores of the right and left masseter, referred sensations and jaw pain intensity and jaw function were assessed at baseline, 48 h after the first injection, 5 min after the second injection and 72 h after the first injection. NGF caused significant jaw pain evoked by chewing at 48 and 72 h after the first injection when compared to the IS group, but without significant differences between the NGF + lidocaine and NGF + IS groups. However, the mechanical sensitivity of the right masseter 5 min after the second injection in the NGF + lidocaine group was significantly lower than the second injection in the NGF + IS and was similar to the IS group. There were no significant differences for the referred sensations. Local anaesthetics may provide relevant information regarding the contribution of peripheral mechanisms in the maintenance of persistent musculoskeletal pain.
Introduction
Bruxism is defined as a repetitive masticatory muscle activity that can manifest it upon awakening (awake bruxism‐AB) or during sleep (sleep bruxism‐SB). Some forms of both, AB and SB ...can be associated to many other coexistent factors, considered of risk for the initiation and maintenance of the bruxism. Although controversial, the term ‘secondary bruxism’ has frequently been used to label these cases. The absence of an adequate definition of bruxism, the non‐distinction between the circadian manifestations and the report of many different measurement techniques, however, are important factors to be considered when judging the literature findings. The use (and abuse) of drugs, caffeine, nicotine, alcohol and psychoactive substances, the presence of respiratory disorders during sleep, gastroesophageal reflux disorders and movement, neurological and psychiatric disorders are among these factors. The scarcity of controlled studies and the complexity and interactions among all aforementioned factors, unfortunately, does not allow to establish any causality or temporal association with SB and AB. The supposition that variables are related depends on different parameters, not clearly demonstrated in the available studies.
Objectives
This narrative review aims at providing oral health care professionals with an update on the co‐risk factors and disorders possibly associated with bruxism. In addition, the authors discuss the appropriateness of the term ‘secondary bruxism’ as a valid diagnostic category based on the available evidence.
Conclusion
The absence of an adequate definition of bruxism, the non‐distinction between the circadian manifestations and the report of many different measurement techniques found in many studies preclude any solid and convincing conclusion on the existence of the ‘secondary’ bruxism.
Coexisting factors related to secondary bruxism.
Objective This study investigated the effect of contingent electrical stimulation (CES) on present pain intensity (PI), pressure pain threshold (PPT), and electromyographic events per hour of sleep ...(EMG/h) on probable bruxers with masticatory myofascial pain. Study Design The study enrolled 15 probable bruxers with masticatory myofascial pain in 3 phases: (1) baseline EMG/h recording, (2) biofeedback treatment using a CES paradigm (active group, n = 7) or inactive device (control group, n = 8), and (3) posttreatment EMG/h recording. PI and PPT were assessed after each phase. Analysis of variance models were used to compare results at a 5% significance level. Results Patients in the active group had 35% lower EMG/h in P2 and 38.4% lower EMG/h in P3, when compared with baseline. There were no differences in PI or PPT levels at any phase. Conclusions CES could reduce EMG activity associated with sleep bruxism in patients with masticatory myofascial pain but did not influence perceived pain.
Aim
This topical review presents common patients’ misbeliefs about temporomandibular disorders (TMD) and discusses their possible impact on the diagnosis, treatment and prognosis. We also discussed ...the possible influence of the beliefs and behaviours of healthcare providers on the beliefs of patients with TMD and suggested possible strategies to overcome the negative impacts of such misbeliefs.
Methods
This topical review was based on a non‐systematic search for studies about the beliefs of patients and healthcare professionals about TMD in PubMed and Embase.
Results
Patients’ beliefs can negatively impact the diagnosis, treatment and prognosis of TMD. These beliefs can be modulated by several factors such as culture, psychosocial aspects, gender, level of knowledge and previous experiences. Moreover, primary healthcare professionals, including dentists, may lack sufficient experience and skills regarding TMD diagnosis and treatment. Misbeliefs of the healthcare professionals can be based on outdated evidence that is not supported by rigorous methodological investigations. Education and dissemination of knowledge to patients and the general population are effective for prevention, promotion of health and disruption of the cycle of misinformation and dissemination of misbeliefs.
Conclusion
The lack of basic information about TMD and the dissemination of mistaken and outdated concepts may delay the diagnosis, hinder the treatment, and consequently increase the risk of worsening the condition. Education is key to overcome TMD misbeliefs.
Misbeliefs about temporomandibular disorders (TMD) can be the result of patients beliefs but are also influenced by the health care professionals. TMD misbeliefs can negatively impact the TMD management. Education strategies can disrupt the cycle of misbeliefs.
Background
Changes in quantitative sensory testing (QST) parameters following topical anaesthesia could contribute to better elucidate underlying mechanisms of somatosensory alterations in ...temporomandibular disorder (TMD) pain patients. This placebo‐controlled crossover investigation compared the somatosensory profile following topical anaesthesia between TMD patients (n = 20) and healthy participants (n = 20).
Methods
Cold detection threshold, warm detection threshold, cold pain threshold, heat pain threshold, mechanical detection threshold, mechanical pain threshold, wind‐up ratio and pressure pain threshold were assessed on the skin overlying the masseter at three consecutive days (baseline and immediately after lidocaine 4%/placebo cream). Mixed ANOVA and a coding system that accounts for the diversity of types of peripheral axons associated with the somatosensory parameters were applied for data analysis.
Results
The lidocaine application caused no changes in the somatosensory sensitivity in the masseter region in TMD patients (P > .050), but sensitivity to cold, cold pain, touch and pinprick stimuli were reduced after topical anaesthesia in healthy participants (P < .050). Also, the degree of topical anaesthesia was greater in healthy participants (P = .008). The coding system suggested that TMD patients presented only Aδ‐fibre block, whereas a combination of either Aβ‐ and/or C‐fibre block was observed in 35% of healthy participants in addition to Aδ‐fibre block following lidocaine application.
Conclusion
Quantitative sensory testing can be successfully applied to identify meaningful differences in the degree of hypoalgesia and hypoesthesia following short‐time topical anaesthesia.
The analgesic activity of (−)-linalool (LIN), a monoterpene present in essential oils of
Lamiaceae
species, has been previously demonstrated in rodents. However, its possible use in the treatment of ...fibromyalgia (FM) was never demonstrated. Additionally, as a short half-life is a limitation for the LIN medicinal application, the employment of drug delivery systems has been used to improve pharmaceutical properties of this compound. We investigated the anti-nociceptive effect of LIN, isolated or in β-cyclodextrin complex (LIN–CD), in an animal model of chronic non-inflammatory muscle pain (a FM animal model), as well as its effect on the central nervous system (CNS). Male Swiss mice were subjected to two injections of acidic saline (pH 4; 20 μL/gastrocnemius) and were treated on alternate days, with LIN–CD (25 mg/kg, p.o.), LIN (25 mg/kg, p.o.), tramadol (TRM 4 mg/kg, i.p.), or vehicle (neutral saline). After 60 min, they were screened for mechanical hyperalgesia (von Frey), motor coordination (rotarod), and muscle strength (grip strength meter) for 27 days. The CNS areas involved in the anti-hyperalgesic activity were evaluated by immunofluorescence. LIN or LIN–CD produced a significant reduction (
p
< 0.001) of mechanical hyperalgesia on chronic non-inflammatory muscle pain model, which remained for 24 h only in LIN–CD, and these compounds significantly (
p
< 0.05) activated neurons of the locus coeruleus, nucleus raphe magnus, and periaqueductal gray areas. So, our results suggest that LIN–CD improved analgesic profile of LIN, with a probable involvement of descending pain pathways and the anti-nociceptive effect of linalool in an animal model of chronic non-inflammatory muscle pain. So far, only the investigations in animal models of inflammatory pain and supraspinatus were published.
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