Libros

Aims: To test whether standardized palpation around the lateral pole of the condyle can influence mechanical sensitivity and unpleasantness and evoke referred sensations/pain in healthy individuals. Methods: Palpometers (0.5, 1.0, and 2.0 kg) with spherical extensions were applied around the lateral pole of the condyle in relaxed and protruded positions of the mandible for 2, 5, and 10 s in 30 healthy participants. Mechanical sensitivity, unpleasantness, and referred sensations/pain were assessed using a 0 to 100 numeric rating scale (NRS) for each palpation. The NRS scores were compared using ANOVA and the McNemar test. Results: Participants reported significantly higher mechanical sensitivity and unpleasantness scores for the 2.0-kg stimulus compared with the 0.5- and 1.0-kg stimuli for a duration of 2, 5, and 10 s (mean NRS > 50; p < 0.001). Application of a 1.0-kg stimulus was significantly different from the 0.5- and 2.0-kg stimuli applied for 5 s (mean NRS < 50; p < 0.001). One-third of participants reported referred sensations/pain. Conclusion: Application of a 2.0-kg stimulus around the lateral pole of the condyle is painful and unpleasant regardless of the duration of palpation. Application of a 1.0-kg stimulus for 5 s was found to be nonpainful and not unpleasant in healthy participants. Thus, this study supports the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) recommendation for standardized examination of the temporomandibular joint and indicates that referred sensation/pain is a common finding in healthy individuals. Palabras clave: DC/TMD, lateral pole of the condyle, mechanical sensitivity, palpation, referred sensation/pain

Aims: To investigate whether localized sensitization of the sternocleidomastoid (SCM) muscle using nerve growth factor (NGF) would affect masseter and anterior temporalis muscle sensitivity and pain profiles. Methods: A total of 28 healthy participants attended two sessions (T0 and T1). At T0, the maximum voluntary occlusal bite force (MVOBF), as well as pressure pain thresholds (PPT), mechanical sensitivity, and referred pain/sensations for the SCM, masseter, and temporalis muscles, were assessed. Participants also completed the Pain Catastrophizing Scale (PCS), the Pain Vigilance and Awareness Questionnaire (PVAQ), and the Neck Disability Index (NDI). After these assessments, 14 participants received an injection of NGF into the SCM, and 14 received an injection of isotonic saline solution. At T1 (48 hours postinjection), the participants were again submitted to the same evaluations. Results: NGF caused significant mechanical sensitization in the SCM (P < .025), but not in the masseter or temporalis muscles (P > .208). It also caused significant increases in NDI score (P = .004). No statistically significant differences were found for MVOBF, frequency of referred pain/sensations, or questionnaire scores (P > .248). Conclusion: These results suggest that 48 hours after localized sensitization of the SCM, the primary response is impairment of neck function, but not jaw function. Palabras clave: behavior, masticatory muscles, musculoskeletal pain, neck pain, nerve growth factor

Aims: To compare two pain models of myalgic TMD, delayed-onset muscle soreness (DOMS) and injections of nerve growth factor (NGF), in terms of pain-related and motor function outcomes, as well as activity-related temporal summation. Methods: Fifty age- and gender-matched healthy participants were recruited and randomized into one of three groups: to a repeated eccentric contraction task to cause DOMS (n = 20), to receive NGF injections into the masseter muscle (n = 20), or to a control group (n = 10). Mechanical sensitivity of masticatory muscles, chewing parameters, jaw function limitation, maximum bite force, and activity-related temporal summation were assessed at baseline and at days 1, 2, and 7 following the intervention. Results: Compared to baseline, both model groups showed increased mechanical sensitivity, jaw function limitation, pain on chewing, and decreased chewing efficiency, lasting longer in the NGF group than in the DOMS group (P < .05). Furthermore, also compared to baseline, the NGF group showed increased pain on maximum bite and decreased pain-free maximum opening (P < .05). No increases in activity-related temporal summation were shown for any of the model groups when compared to baseline or the control group (P > .05). Conclusion: Both models produced similar painrelated outcomes, with the NGF model having a longer effect. Furthermore, the NGF model showed a more substantial effect on motor function, which was not seen for the DOMS model. Finally, neither of the models were able to provoke activity-related temporal summation of pain. Palabras clave: experimental pain, mechanical sensitivity, myalgia, temporal summation, trigeminal motor physiology

Aims: To investigate pain sensitivity in the masseter muscle and index finger in response to acute psychologic stress in healthy participants. Methods: Fifteen healthy women (23.7 ± 2.3 years) participated in two randomized sessions: in the experimental stress session, the Paced Auditory Serial Addition Task (PASAT) was used to induce acute stress, and in the control session, a control task was performed. Salivary cortisol, perceived stress levels, electrical and pressure pain thresholds (PTs), and pain tolerance levels (PTLs) were measured at baseline and after each task. Mixed-model analysis was used to test for significant interaction effects between time and session. Results: An interaction effect between time and session occurred for perceived stress levels (P .001); perceived stress was significantly higher after the experimental task than after the control task (P .01). No interaction effects occurred for salivary cortisol levels, electrical PTs, or pressure PTLs. Although significant interactions did occur for electrical PTL (P .05) and pressure PT (P .001), the simple effects test could not identify significant differences between sessions at any time point. Conclusion: The PASAT evoked significant levels of perceived stress; however, pain sensitivity to mechanical or electrical stimuli was not significantly altered in response to the stress task, and the salivary cortisol levels were not altered in response to the PASAT. These results must be interpreted with caution, and more studies with larger study samples are needed to increase the clinical relevant understanding of the pain mechanisms and psychologic stress. Palabras clave: analgesia, facial pain, hyperalgesia, pain, stress

Aims: To assess the pain and/or unpleasantness and the somatosensory changes caused by two experimental models of trigeminal nerve damage (topical application of capsaicin and local anesthetics) in healthy participants using extensive evaluation tools. Methods: This double-blinded, randomized, placebo-controlled, crossover study included 20 healthy adult participants who underwent three separate sessions of testing. In each session, the psychophysical quantitative sensory testing (QST) and the electrophysiologic electrically evoked trigeminal "nociceptive-specific" blink reflex (nBR) investigations were performed at baseline. Following a 15-minute topical application of 0.1% capsaicin, 5% EMLA, or Vaseline (placebo) agents, the maximum numeric rating scale pain and unpleasantness scores were recorded. Additionally, qualitative sensory testing and somatosensory mapping were performed. The QST and nBR investigations were repeated immediately after each application. Data were analyzed using repeatedmeasures analysis of variance. Results: Capsaicin application was associated with significantly higher pain and unpleasantness scores when compared to EMLA and Vaseline (P .001), with varied bidirectional somatosensory changes among the participants and significant loss of thermosensory function (P .030). EMLA application induced loss of thermal and mechanical somatosensory function (P .030) and a significant reduction in electrically evoked pain scores on nBR investigation (P .001). No significant changes were seen in the electrophysiologic component of the nBR after any of the applications (P = .922). Conclusion: Topical capsaicin and EMLA application mimicked certain aspects of somatosensory changes seen in trigeminal nerve damage patients and may be used as surrogate models of such changes. Palabras clave: blink reflex, capsaicin, EMLA, quantitative sensory testing, trigeminal nerve damage

Aims: To compare somatosensory function profiles and psychologic factors in patients with primary burning mouth syndrome (BMS) and healthy controls and to evaluate correlations of subjective pain ratings with somatosensory and psychologic parameters. Methods: A quantitative sensory testing (QST) protocol-including cold detection threshold (CDT), warmth detection threshold (WDT), thermal sensory limen (TSL), paradoxical heat sensation (PHS), cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), wind-up ratio (WUR), and pressure pain threshold (PPT)-was performed at the oral mucosa of the tongue, buccal, and palatal sites in 30 Chinese patients (25 women and 5 men, mean age 50.9 ± 9.2 years) with primary BMS and in 18 age- and gender-matched healthy controls (15 women and 3 men, mean age 53.2 ± 7.0 years). For each BMS patient, z scores and loss/gain scores were computed. Psychologic status was evaluated in both groups using the Self-Rating Anxiety Scale and Self-Rating Depression Scale. Correlations of BMS patients' subjective pain ratings with somatosensory and psychologic profiles were assessed with the use of Pearson or Spearman correlations and multiple linear regression. Results: In BMS patients, 53.3% had somatosensory abnormalities according to z scores vs 22.2% of healthy controls (P = .033). The abnormalities in BMS patients were somatosensory loss to thermal nonnoxious stimuli (TSL = 20.0%, CDT = 13.3%, WDT = 13.3%), mechanical pressure stimuli (PPT = 16.7%), pinprick stimuli (MPT = 6.7%), and thermal pain stimuli (CPT = 3.3%), and somatosensory gain to repetitive pinprick stimuli (WUR = 6.7%), pressure stimuli (PPT = 6.7%), and thermal pain stimuli (HPT = 3.3%). The most frequent loss/gain score was 13.3% for loss of thermal somatosensory function with no somatosensory gain; 13.3% for loss of thermal and mechanical somatosensory function with no somatosensory gain; and 13.3% for gain of mechanical somatosensory function with no somatosensory loss. Mild elevations in anxiety scores were seen in 30% of the BMS patients, and 50% and 36.7% had mild and moderate elevations, respectively, in depression scores. No anxiety or depression was detected in the control group. QST results, but not psychologic scores, were significantly correlated with patients' subjective pain ratings (PHS, Spearman coefficient -0.384, P = .029; CPT, Pearson coefficient -0.370, P = .034; MPT, Pearson coefficient -0.376, P = .032; PPT, Pearson coefficient 0.363, P = .037). Conclusion: The present findings documented distinct differences in somatosensory function in patients with primary BMS compared to controls, indicating a complex pathophysiology and interaction between impairments in nociceptive processing and psychologic functioning. Palabras clave: burning mouth syndrome, psychological changes, quantitative sensory testing, somatosensory profiles

Aims: To investigate the region-specific effects of painful trigeminal capsaicin stimulation in healthy participants. Methods: Twenty healthy participants (10 men and 10 women) participated in four sessions in which they received application of 0.05 mL Vaseline (placebo) or capsaicin cream (0.1%) to a different area innervated by the three branches of the trigeminal nerve: the supraorbital area (V1), the nasal mucosa (V1/V2), and the maxillary (V2) and mandibular (V3) oral mucosa. The participants rated their perceived sensations on a 0-50-100 numeric rating scale (NRS). Thermal (5°C, 23°C, and 50°C) and mechanical (32 mN and 256 mN) sensitivities were assessed. The Schirmer tearing test was used to monitor the lacrimation level as a local measure of autonomic activity, and the Task Force Monitor was used to record systemic autonomic activity. Data were analyzed using repeated measures analysis of variance. Results: Capsaicin application evoked significantly higher overall NRS scores (P .001) and induced significantly higher ratings to the heat stimuli (P .009) in all sessions compared to control. For lacrimation level, capsaicin stimulation resulted in a significant increase compared to control (P .0002) only in the nasal mucosa session. Conclusion: Topical application of capsaicin cream to the different branches of the trigeminal nerve caused higher NRS scores along with an altered somatosensory sensitivity. Furthermore, in the nasal mucosa session, a robust local and generalized parasympathetic activation appeared following capsaicin application. Palabras clave: autonomic nervous system, capsaicin, experimental pain model, trigeminal nociception, trigeminal parasympathetic reflex

Aims: To determine whether patients with painful myofascial temporomandibular disorders (TMD) demonstrate facilitated temporal summation (TS) responses to painful heat stimuli applied to the painful trigeminal and extratrigeminal regions and whether there is a side difference in the trigeminal region for myofascial TMD pain patients compared to healthy controls. Methods: Twenty female Chinese myofascial TMD pain patients and 20 age-matched female volunteers participated in this case-control study. Thermal detection thresholds, thermal pain thresholds, and TS of 20 repetitive noxious thermal stimuli were measured on the skin above the masseter muscle on both sides and the thenar eminence of the less painful side/dominant hand. Numeric rating scale (NRS) scores of pain were provided after the 1st, 5th, 10th, 15th, and 20th stimuli, and TS was calculated as the highest NRS score minus the first NRS score in each test. Results: Evidence of TS was found in the trigeminal and extratrigeminal regions for both groups, but with facilitated TS responses in myofascial TMD pain patients (P .001). Within the myofascial TMD group and control group, there were no side-to-side differences (P > .289). Interestingly, the repetition of the TS test was associated with facilitated responses in myofascial TMD pain patients (P .001). Conclusion: The current findings suggest TS of painful heat stimulation is facilitated in myofascial TMD pain patients with no side difference in the trigeminal region. Palabras clave: hyperalgesia, myofascial pain, temporal summation, temporomandibular disorders, thermal detection

Aims: To test whether standardized palpation around the lateral pole of the condyle can influence mechanical sensitivity and unpleasantness and evoke referred sensations/pain in healthy individuals. Methods: Palpometers (0.5, 1.0, and 2.0 kg) with spherical extensions were applied around the lateral pole of the condyle in relaxed and protruded positions of the mandible for 2, 5, and 10 seconds in 30 healthy participants. Mechanical sensitivity, unpleasantness, and referred sensations/pain were assessed using a 0 to 100 numeric rating scale (NRS) for each palpation. The NRS scores were compared using analysis of variance and McNemar test. Results: Participants reported significantly higher mechanical sensitivity and unpleasantness scores for the 2.0-kg stimulus compared to the 0.5- and 1.0-kg stimuli for 2, 5, and 10 seconds (mean NRS > 50; P .001). Application of a 1.0-kg stimulus was significantly different from the 0.5- and 2.0-kg stimuli applied for 5 seconds (mean NRS 50; P .001). One-third of participants reported referred sensations/pain. Conclusion: Application of a 2.0-kg stimulus around the lateral pole of the condyle is painful and unpleasant regardless of time of palpation. Application of a 1.0-kg stimulus for 5 seconds was found to be nonpainful and not unpleasant in healthy participants. Thus, this study supports the Diagnostic Criteria for TMD recommendation for standardized examination of the TMJ and indicates that referred sensation/pain is a common finding in healthy individuals. Palabras clave: DC/TMD, lateral pole of the condyle, mechanical sensitivity, palpation, referred sensation/pain