The present investigation attempts to describe the correlation between sleep-time masticatory muscle activity (MMA) and psychological symptoms by the use of a four-channel electromyography (EMG) home-recording device in a group of 15 healthy volunteers completing a battery of psychometric questionnaires for the assessment of anxiety, depression and anger. The integrated EMG signal was adopted to quantify the work (μV × s) produced by each of the four muscles (bilateral masseter and temporal) during the 5-h recording span and per each 1-h increment. The duration of MMA events and the muscle work during the first hour of sleep was related to trait anxiety scores for both masseter (P = 0·007) and temporalis muscles (P = 0·022). Trait anxiety was also significantly correlated to the total amount of MMA duration (in seconds) of the temporalis muscles (r = 0·558; P = 0·031). The present investigation provides support to the hypothesis that the duration of sleep-time masticatory muscle activity, especially during the early phases of a night's sleep, may be related to anxiety trait and not to anxiety state, depression or anger. These findings may support the view that features related to the individual management of anxiety, viz. trait, are likely to be more important than acute episodes of anxiety, viz. state, in the aetiology of sleep-time masticatory muscle activity. The role of other psychological symptoms is likely to be less important.

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Several works showed a decreased role for occlusion in the etiology of temporomandibular disorders (TMD). Nonetheless, it may be hypothesized that occlusion acts as a modulator through which bruxism activities may cause damage to the stomatognathic structures. To test this hypothesis, a logistic regression model was created with the inclusion of clinically diagnosed bruxism and eight occlusal features as potential predictors for temporomandibular joint (TMJ) pain in a sample of 276 consecutive TMD patients. The final logit showed that the percentage of the total log likelihood for TMJ pain explained by the significant factors was small and amounted to 13.2%, with unacceptable levels of sensitivity (16.4%). The parameters overbite > or = 4 mm combined with clinically diagnosed bruxism [OR (odds ratio) 4.62], overjet > or = 5 mm (OR 2.83), and asymmetrical molar relationship combined with clinically diagnosed bruxism (OR 2.77) were those with the highest odds for disease, even though none of those values was significant with respect to confidence intervals. Thus, the hypothesis under evaluation has to be rejected. It is possible that future studies with a higher discriminatory power for the different bruxism activities might be indicated to get deeper into the analysis of the potential mechanisms through which occlusion may play a role, even if small, in the etiology of the different TMD.

We reviewed the literature from 1985 to 1996 concerning the preliminary treatment of disc dislocation with reduction (DDWR) by means of occlusal splints, pinpointing two main methods. The conflicting results of many papers induced us to make a literature meta-analysis of those articles with the necessary requirements in order to verify the effectiveness of the two therapeutic means more frequently used in DDWR; the repositioning splint and the bite plane. A statistical comparison between the two kinds of treatment has demonstrated that the repositioning splint is more effective both in the resolution of the articular click and of the pain at a level of P < or = 0.00001, which is noteworthy and highly significant.

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