Journal of Oral & Facial Pain and Headache, 04/2001

Aims: To correlate histologic changes with the stress developed by various disc interferences via a model of partial anterior disc displacement in the rabbit temporomandibular joint (TMJ). Methods: Eighteen male New Zealand rabbits were operated on to expose the temporomandibular disc without severing its attachments. A suture was passed around the lateral part of the disc over the condylar attachments and the 2 strands were fixed in the orbital cavity. In 9 rabbits, a resorbable suture was used to secure the disc displacement. In the other 9, a nonresorbable suture was fixed with a nickel-titanium spring to displace and maintain tension on the disc. Three non-operated animals served as controls. The animals were sacrificed at 12 and 24 weeks after surgery, and the TMJs were prepared for undecalcified histology. Results: In the first group, the disc remained in a normal position, but its morphology was modified and small histologic changes were observed in the cartilage. In the second group, the disc was displaced in various positions corresponding to the strength delivered by the spring. Conclusion: Adaptive changes were observed in joints with a slightly displaced disc, while degenerative changes were associated with larger disc displacements. In each experimental joint, histologic changes increased from the medial to lateral parts. This phenomenon was related to the stress gradient induced by axial disc rotation over the condyle. Any disc displacement always resulted in changes in the cartilage. Keywords: temporomandibular joint disc, temporomandibular joint, internal derangement, animal study, histology, mandibular condyle

Aims: To determine whether sex differences exist in tissue oxygen saturation (StO2) and the hemoglobin (Hb) oxygenation state of the resting human masseter muscle. Methods: Near-infrared spectroscopy (NIRS) was used to measure StO2 and Hb oxygenation state in 20 healthy adult volunteers (10 women and 10 men). To determine the measurement range and reliability of the NIRS recording probe, the probe was set up on 12 layers of white acrylic resin plate, each 3 mm thick. Total hemoglobin levels were measured while a red vinyl resin plate, 1 mm thick, was inserted in turn between each of the 12 layers. Distances from the skin surface to the lateral surface (S-L) and to the medial surface (S-M) of the right masseter at the middle portion of the masseter were measured on T1- weighted magnetic resonance images (repetition time 500 ms, echo time 23 ms). Thickness of the masseter was calculated by subtraction [(S-M) - (S-L)]. For the study of Hb oxygenation state, the probe was positioned at the same position on the skin surface at the mandibular postural (rest) position. Results: The measurement range of the NIRS probe was from 9 to 21 mm under the skin, and the reliability of the probe was judged by intra- and inter-class correlation coefficients. There was no sex difference in S-L and the thickness of the masseter; the means of S-L and masseter thickness were 9.3 mm and 15.5 mm in men and 9.8 mm and 14.3 mm in women, respectively. Except for StO2 values, there were significant sex differences in the Hb oxygenation parameters, with the mean values in the men being approximately twice those in the women. Conclusion: These results provide evidence that a sex difference in the Hb oxygenation state may exist in the masseter muscle of normal healthy subjects. Keywords: hemoglobin oxygenation, hemodynamics, blood flow, masseter muscle

Aims: To determine via a prospective investigation whether the presence of neuropsychologic or cognitive deficiencies could be identified in patients with temporomandibular disorders (TMD) and used to predict treatment outcome. This was based on the theory that measurable reductions in neuropsychologic and cognitive function might have a negative impact on treatment outcome in patients with essentially nontraumatic TMD, as has been shown for patients with posttraumatic TMD. Methods: Various neuropsychologic, psychosocial, and clinical parameters (including but not limited to the Peterson-Peterson Consonant Trigram Test and the California Verbal Learning Test) were used to pretest patients suffering from TMD prior to treatment. Patients were then entered into treatment, after which determination of treatment success was made both by the use of visual analog scales for pain and global transitional outcome measures (eg, "better," responders versus "same/worse," nonresponders). After determination of treatment success was made, treatment response was correlated with the various clinical, cognitive, and neuropsychologic test scores. Results: Overall, the nonresponders did worse in both the neuropsychologic and psychosocial assessments, with greater memory deficits, sleep disturbances, depression, and fatigue and lower energy levels as compared to responders. Among the best predictors of treatment outcome were the Peterson- Peterson Consonant Trigram Test scores, as well as the scores on the California Verbal Learning Test (ie, poorer test outcomes predicted nonresponse). Neither responders nor nonresponders could be distinguished from one another based on clinical parameters of maximum interincisal opening or muscle tenderness. Three psychosocial variables were also found to be predictors of poor outcome: sleep disturbance, fatigue, and income. Pretreatment pain on chewing was also found to be a reliable predictor of poor treatment outcome. Conclusion: We conclude that various neuropsychologic, psychosocial, and some clinical parameters may provide pretreatment prediction of treatment outcome in an idiopathic TMD population. Keywords: temporomandibular disorders, psychological tests, treatment outcome, cognition, prospective study

Aims: Recently, the use of selective serotonin reuptake inhibitors (SSRIs) has been associated with the occurrence or worsening of bruxism. The aim of this study was to obtain a first indication of the prevalence of SSRI-associated bruxism reported to family physicians, the main prescribers of SSRIs. Methods: A questionnaire, with questions about prescription rate, already registered adverse reactions, and bruxism-related side effects of 4 different types of SSRIs, was sent to all family physicians in greater Amsterdam (n = 391). Results: With a response rate of 42.5%, frequent observations of already registered side effects were found. In addition, 5 family physicians (3.2%) reported the occurrence of bruxism in relation to the use of SSRIs. Conclusion: The use of SSRIs might be associated with the occurrence of bruxism. A case report is provided that corroborates this suggestion. Keywords: bruxism, serotonin reuptake inhibitors, adverse drug reaction reporting systems, questionnaire, case report