Journal of Oral & Facial Pain and Headache, 01/2004

Critical evaluation of treatment methods has become an important part of health care and will certainly have a major influence on decisions about acceptable treatment methods in the future. Evidence-based medicine (EBM) means the systematic, explicit, and judicious implementation of the best evidence in patient care. The most reliable sources of evidence are high-quality systematic reviews and randomized controlled trials (RCTs). A systematic EBM approach could be particularly useful in the treatment of temporomandibular disorders (TMD), where controversial and conflicting ideas about management are common. In this field, concerns about the lack of evidence are often expressed. This article aims to elucidate and discuss the application of EBM to the treatment of TMD, using the most controversial treatments (ie, occlusal treatments) as an example. By applying the principles of EBM to TMD treatments, we wish to highlight some of the important issues that form the basis for high-quality care in this field. A systematic review of occlusal treatments (occlusal splints and occlusal adjustment) updated to January 2003 revealed 16 RCTs of occlusal splints and 4 of occlusal adjustment. The overall quality of the trials was fairly low. Recently, however, some high-quality RCTs of occlusal splints have been published. The most obvious methodologic shortcomings in published trials included problems in defining the patient population, inadequacies in performing randomization and blinding, problems in defining the therapies or appropriate control treatments, short follow-ups, and problems in monitoring patient compliance. Occlusal splint studies yielded equivocal results. Even in the most studied area, stabilization splints for myofascial face pain, the results do not justify definite conclusions about the efficacy of splint therapy. Their clinical effectiveness to relieve pain also seems modest when compared with pain treatment methods in general. None of the occlusal adjustment studies provided evidence supporting the use of this treatment method. The clinical implications of the findings and future perspectives are discussed. Keywords: dentistry, evidence-based medicine, occlusal adjustment, occlusal splints, randomized controlled trials, temporomandibular disorders

Aims: To examine the jaw-stretch reflex after injection of local anesthetic (LA) into painful temporomandibular joints (TMJs), since the functional role of jaw-stretch reflexes in patients with painful temporomandibular disorders is still not well understood. Methods: Thirteen female patients with a clinical diagnosis of disc displacement without reduction and TMJ pain participated in this open study. Reflex responses were evoked by fast stretches at 15% of the maximal voluntary contraction level before and after injection of 1 mL carbocaine into the painful TMJ. Electromyographic (EMG) activity was recorded from the left and right masseter and temporalis muscles, and the mean level of prestimulus EMG activity and peak-to-peak amplitude of the stretch reflex were measured. Visual analog scale ratings of TMJ pain and TMJ pressure pain thresholds (PPTs) were also obtained. Eleven healthy women were examined with the same protocol (except for PPT determinations) before and after injection of LA into the TMJ. Results: In patients, injection of LA reduced the TMJ pain during jaw movements and maximum clenching (P < .021) and increased the PPTs in the painful TMJ (P < .01). The prestimulus EMG activity in the masseter on the painful side (feedback muscle) was unaffected by the injection of LA (P > .262). There were no significant side-toside asymmetries of latency or amplitude measures of the stretch reflex in the patient group. Both the peak-to-peak amplitude and the normalized peak-to-peak amplitude of the stretch reflex were reduced in the masseter and temporalis muscles on the painful side and in the masseter on the nonpainful side after LA injections (P < .048). There were no effects of LA injections into the TMJ in the healthy group on any EMG or stretch parameters. Conclusion: These results do not support the notion of asymmetries in the jawstretch reflex in patients with TMJ pain, but they do suggest that the reflex sensitivity can be influenced by nociceptive activity from the TMJ area. Keywords: local anesthesia, pain, pain thresholds, stretch reflex, temporomandibular joint, trigeminal nerve

Aims: Previous work suggests that hyperexcitability of central nociceptive neurons may play a role in the pain of temporomandibular disorders (TMD). The aim of this study was to test this theory by assessing differences, between myalgic TMD patients and pain-free controls, in temporal summation of mechanically evoked pain and aftersensations following repetitive noxious stimulation. Methods: Sixteen series of 10 repetitive, mildly noxious mechanical stimuli were applied to the fingers of 25 female TMD patients with masticatory myofascial pain and 25 age-matched, pain-free female subjects. All subjects rated the pain intensity and unpleasantness evoked by the first, fifth, and tenth stimuli in the series and their aftersensations at 15 seconds and 1 minute following the last stimulus. Data were analyzed by 3-way repeated-measures analysis of variance. Results: Pain and unpleasantness ratings increased with repetition of the stimulation (P < .0001). In addition, there was a significant trial number x group interaction for the pain intensity ratings, such that TMD patients provided higher ratings than controls for the tenth stimulus (P < .001). The increase in unpleasantness ratings with repetitive stimulation was also higher for the patient group (P < .0001). Moreover, TMD patients rated the intensity of aftersensations as higher (P < .005) and reported painful aftersensations at significantly greater frequency (P < .05). Conclusion: A generalized hyperexcitability of central nociceptive processing in this TMD patient group is indicated by their more pronounced temporal summation of pain and greater aftersensations following repetitive noxious digital stimulation versus controls. Such hyperexcitability may contribute to the pathophysiology of TMD pain. Keywords: myofascial pain syndromes, pain thresholds, temporal summation, temporomandibular disorders, wind-up

Aims: To investigate whether there are any correlations between increased masticatory loading, degree of tooth wear, and the size, form, and macroscopic surface of the temporomandibular joints (TMJs). Methods: The degree of tooth wear and different TMJ variables were compared in 2 groups of domestic pigs. One group of 8 pigs had been raised indoors (ID group), and the other group of 9 pigs had been raised outdoors (OD group). The pigs in the ID group were fed a soft diet and were not provided any straw in their pens. The OD group was fed a solid diet and could also grub in the soil, resulting in an exposure to more abrasive components and to greater chewing demands. All pigs were sacrificed at the age of 22 months. Results: The pigs in the OD group exhibited significantly more tooth wear compared to the ID group. No difference in mediolateral size of the condyles could be found between the 2 groups. Form and surface changes of the TMJs varied substantially between individuals, but not between the 2 groups. No correlation could be found between the degree of tooth wear and any of the TMJ variables. Conclusion: Exposure to a tougher diet containing more abrasive substances has a significant impact on the degree of tooth wear but seems to have no consequences either for the size of the TMJ condyles or for form or surface changes of the TMJs. Keywords: animal trial, osteoarthrosis, temporomandibular joint, tooth attrition

Aims: To study the effect of dexamethazone and dipyrone on sensory changes in the innervation territories of the inferior alveolar, infraorbital, and lingual nerves caused by third molar extractions. Methods: Fourteen patients (8 men and 6 women) were divided randomly into 2 groups. The first group received dipyrone preoperatively, while the second group received dipyrone and dexamethazone preoperatively. All patients in the study received a prophylactic preoperative dose of amoxicillin (500 mg) as well as dipyrone postoperatively. In all patients, a single mandibular third molar was removed, while in 2 patients the contralateral third molar was removed at a subsequent time. Electrical detection thresholds were assessed in the inferior alveolar, lingual, and infraorbital nerve regions prior to surgery and 2 and 8 days following surgery. The level of perioperative pain, difficulty of extraction, and distance of molar root apices from the inferior alveolar nerve canal were also assessed. Results: Patients who received only dipyrone had significantly reduced lingual and inferior alveolar nerve electrical detection thresholds 2 days after surgery, which returned to nearly baseline values by the eighth day postoperatively. In patients who received dexamethasone, no significant reduction in the electrical detection threshold was found. Conclusion: Preoperative treatment with dexamethasone and dipyrone but not dipyrone alone prevents sensory hypersensitivity following third molar extraction. Keywords: dexamethasone, dipyrone, pain measurement, third molar, tooth extraction