Journal of Oral & Facial Pain and Headache, 02/2005

Aims: To document and compare the intensity, localization, and quality of pain evoked by glutamate injections into the human masseter or splenius muscles and to determine the effect of glutamate-evoked pain on the pressure pain thresholds (PPTs) in both jaw and neck muscles. Methods: Twenty-six healthy men were given painful injections of glutamate (1.0 mol/L) and control injections of isotonic saline (0.165 mol/L) into the masseter and splenius muscles. The subjects rated the perceived intensity of pain on a visual analog scale (VAS), drew the area of the pain on maps of the face and neck, and filled out a Danish version of the McGill Pain Questionnaire (MPQ). PPTs were used to assess the sensitivity of the masseter and splenius muscles to mechanical stimuli (n = 11). Results: Glutamate injection into the masseter or splenius evoked pain lasting almost 10 minutes. Peak pain intensity usually occurred within 2 minutes of the injection, and VAS scores of peak pain were significantly higher for the masseter muscle compared with the splenius muscle (paired t test, P = .003). The pain area from the masseter injections did not extend into the neck region, although in some subjects the pain from the neck region extended into the temporal region. There were no significant relationships between the area of perceived pain and the VAS pain scores (Pearson correlation, P > .297). Glutamate-evoked pain in either the masseter or splenius muscles was associated with significant decreases in masseter or splenius PPTs, respectively (2-wayANOVAs, P .016). Isometric saline injections were almost pain-free and caused no PPT changes. Conclusion: The data suggest that the masseter muscle is more sensitive to glutamate injections and mechanical stimuli than the splenius muscle. The relatively limited overlap between the sensory manifestations of pain from masseter and splenius muscles may have potential implications for diagnosis and management of myofascial pain complaints in the craniofacial and neck region. Keywords: cervical spine pain disorders, experimental muscle pain, glutamate, temporomandibular disorders, trigeminal pain

Aims: To clarify the effects of experimental trapezius muscle pain on the spread of pain and on jaw motor function. Methods: In 12 male subjects aged 25 to 35 years, experimental pain was induced in the superior border of the trapezius muscle by injecting 0.5 mL of hypertonic (6%) saline. The control infusion consisted of a 0.5-mL isotonic (0.9%) saline solution. Pain intensity was evaluated on a visual analog scale (VAS). An experimental (EX) and a control (CT) injection were administered to the subjects in a randomized sequence. Results: Pain intensity as scored on the VAS increased immediately after the EX injection and decreased gradually after reaching a peak of 68.0 ± 16.1 mm at 60 seconds after injection. The VAS scores in the EX condition were significantly higher than after the CT condition from 30 to 330 seconds after injection (P , .05, analysis of variance [ANOVA]). Mean (± SD) maximal unassisted mouth opening before injection in the EX condition was 54 ± 5.7 mm and decreased immediately after the injection, reaching a low of 47.8 ± 5.1 mm. A gradual recovery to normal was then observed. This reduction of mouth opening in the EX condition was significant compared with the CT condition from immediately after the injection to 60 seconds after the injection (P , .05, ANOVA). According to the subjects, pain spread most often to the infra-auricular zone (n = 6), and the posterolateral part of the neck (n = 10). Conclusion: The present results suggest that experimental trapezius muscle pain can spread over a wide area and is also accompanied by a temporary reduction of mouth opening. Keywords: experimental pain, jaw motor function, limited mouth opening, pain spreading, trapezius muscle

Aims: To investigate the existence of pain outside the facial area as well as pain sensitivity in a population-based sample of 34-year-old subjects with facial pain. Methods: Fifty-two facial pain cases (10 men, 42 women) and 52 pain-free controls (10 men, 42 women) included in the Northern Finland Birth Cohort of 1966 underwent a clinical musculoskeletal examination. Pain outside the facial area during the week prior to the examination was defined by means of a pain drawing. Eighteen fibromyalgia points were palpated in response to digital palpation with an algometer. Pressure pain thresholds were measured from the dorsal side of the wrist and from the highest points of the temporalis muscles. Results: Compared to controls, pain cases reported significantly more pain in areas outside the face, with the exception of the shoulder and lower back. The number of painful fibromyalgia points was significantly higher in cases than in controls. Mean pressure pain thresholds were slightly lower in cases than in controls; the difference was significant in the left wrist. Conclusion: Subjects with facial pain reported more pain and had more muscular tenderness outside the facial area compared to controls. Pain symptoms outside the facial area should be assessed in patients seeking treatment for facial pain, and they should be taken into account when treatment is planned. Keywords: facial pain, generalized pain, pain sensitivity, temporomandibular disorders

Aims: Since cyclic effects on experimental pain response in women with temporomandibular disorders (TMD) have not been adequately studied, the aim of this study was to assess variations in experimental pain response at 4 phases of the menstrual cycle. Methods: Eighteen normally cycling women with TMD, 25 women with TMD and taking oral contraceptives (OC), 25 normally cycling pain-free controls, and 26 pain-free controls taking OC underwent 3 experimental pain procedures at 4 phases during each of 3 menstrual cycles. These procedures included algometer palpations at fixed amounts of pressure and pressure pain thresholds at several body sites, and an ischemic arm pain task. Repeated measures analysis of variance was used to compare cycle phase, TMD group, and OC status differences in experimental pain response. Results: Significant phase-related differences were seen for palpation intensity measures (P values , .05). Normally cycling women with TMD showed higher palpation pain intensity at menses and midluteal phases, while women with TMD taking OC showed stable palpation pain intensity ratings at menses, ovulatory, and midluteal phases, with increased intensity at the late luteal phase. TMD subjects had greater palpation pain and ischemic pain intensity and lower pressure pain thresholds compared to controls. Conclusion: Phase-related differences in experimental pain response were not strong and were more often found for experimental stimuli with greater clinical relevance (ie, palpation pain) compared with an ischemic pain task. Keywords: experimental pain, menstrual cycle, temporomandibular disorders

Aims: To assess the prevalence of temporomandibular disorder (TMD) pain in Swedish adolescents, to evaluate whether there are differences in TMD pain in regard to age, gender, and place of residence (urban or rural), and to evaluate treatment for TMD pain and compare it with documented treatment for teeth with caries. Methods: All youths aged 12 to 19 years in Östergötland County were eligible to participate in the investigation, which took place at public dental clinics during annual examinations in 2000. The subjects were asked 2 questions: (1) "Do you have pain in your temples, face, jaw joint, or jaws once a week or more?" and (2) "Do you have pain when you open your mouth wide or chew once a week or more?" Two hundred dental records of patients with TMD pain and 100 records of patients with documented caries were randomly selected from the population. These records were used to compare the treatment of TMD pain to the treatment of caries. Results: Among the 28,899 youths participating, 4.2% reported TMD pain. The prevalence increased with age, and a significant difference was seen between boys (2.7%) and girls (6.0%) (P .001). In 43% of the patients with TMD pain, the TMD condition was noted in the record. TMD-related treatment was given to 34% of patients with TMD pain in dental clinics, whereas 100% of the patients with caries received restorative treatment. The most common treatment modalities for the TMD group were occlusal splints and information about TMD. Conclusion: The prevalence of self-reported TMD pain was relatively low, increased with age, and was higher among girls than boys. One third of the patients with TMD pain received some form of TMD treatment in the dental clinics. Keywords: adolescents, gender, pain management, prevalence, temporomandibular disorders

Aims: To assess the efficacy of occlusal stabilization splints in the management of sleep bruxism (SB) in a double-blind, parallel, controlled, randomized clinical trial. Methods: Twenty-one participants were randomly assigned to an occlusal splint group (n = 11; mean age = 34.2 ± 13.1 years) or a palatal splint (ie, an acrylic palatal coverage) group (n = 10; mean age = 34.9 ± 11.2 years). Two polysomnographic recordings that included bilateral masseter electromyographic activity were made: one prior to treatment, the other after a treatment period of 4 weeks. The number of bruxism episodes per hour of sleep (Epi/h), the number of bursts per hour (Bur/h), and the bruxism time index (ie, the percentage of total sleep time spent bruxing) were established as outcome variables at a 10% maximum voluntary contraction threshold level. A general linear model was used to test both the effects between splint groups and within the treatment phase as well as their interaction for each outcome variable. Results: Neither occlusal stabilization splints nor palatal splints had an influence on the SB outcome variables or on the sleep variables measured on a group level. In individual cases, variable outcomes were found: Some patients had an increase (33% to 48% of the cases), while others showed no change (33% to 48%) or a decrease (19% to 29%) in SB outcome variables. Conclusion: The absence of significant group effects of splints in the management of SB indicates that caution is required when splints are indicated, apart from their role in the protection against dental wear. The application of splints should therefore be considered at the individual patient level. Keywords: bruxism, occlusal stabilization splint, polysomnography, randomized clinical trial, sleep

Aims: To test the hypotheses that masseteric inflammation produces a reduction of mean bite force and success rates and that classical anti-inflammatory agents prevent inflammation-induced changes in bite force. Methods: Rats were initially trained to produce a bite force greater than 400 g. Once the rats attained above 70% of successful responses in a 10-minute test period, the bite force required for reinforcement was increased gradually to the target force of 1.3 kg. Seven trained rats received bilateral masseteric injections of complete Freund's adjuvant (CFA; 50 µL in isotonic saline). The mean number of attempted bites, the percentage of correct responses, and the bite force measured before and 1, 2, 3, 7, 10, and 14 days following the CFA injection were compared. Five additional trained rats were injected with the same volume of vehicle control. Other rats (n = 10) were treated with anti-inflammatory agents before and after the CFA injection. Results: Intramuscular CFA, but not the vehicle, produced a significant reduction of mean bite force and success rate at days 1, 2, and 3. Bite force and success rate gradually increased; they returned to baseline by 14 days. The CFA-mediated reduction of bite force and success rate was prevented in rats treated with anti-inflammatory agents administered intraperitoneally (dexamethasone, n = 5, or indomethacin, n = 5, 4 mg/kg). Conclusion: These results provide further evidence that bite force measurements in awake rats can be a useful method for the study of inflammatory muscle hyperalgesia. Keywords: bite force, masseter inflammation, rat behavior

Aims: To evaluate the occurrence of professional delay in the diagnosis, referral, and treatment of patients with burning mouth syndrome (BMS). Methods: Fifty-nine patients (51 women and 8 men; average age, 60.5 years; age range, 32 to 88 years) diagnosed with BMS at our institution were retrospectively studied. Data were collected about the onset of oral symptoms, consultations with medical and dental practitioners, and misdiagnosis before definitive BMS diagnosis and treatment. Results: The average delay from the onset of the symptoms to definitive diagnosis was 34 months (range, 1 to 348 months; median, 13 months). The average number of medical and dental practitioners consulted by each patient over this period and who initially misdiagnosed BMS was 3.1 (range, 0 to 12; median, 3). Candidiasis and aspecific stomatitis were the most frequent misinterpretations of the symptoms before appropriate referral. In about 30% of cases, no diagnosis of the oral symptoms was made or explanation given. Conclusion: Professional delay in diagnosing, referring, and appropriately managing BMS patients occurred frequently in the group studied. No significant differences were found in the number of medical and dental practitioners who were consulted. Emphasis must therefore be placed upon educational efforts to improve health care providers' awareness of BMS. This should increase the rate of recognition and appropriate referral or treatment of patients with chronic orofacial pain due to BMS. Keywords: burning mouth syndrome, diagnostic delay, orofacial pain, professional education