European journal of oral sciences
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Pressure pain thresholds (PPTs) of the bilateral masseter and temporalis muscles were assessed over a single day and in between 2 days with the aid of an electronic algometer in 11 males and 11 females. Using a mixed model approach, covariance results were controlled for confounding of gender, day, time of the day and the within-session replications of the measurements. For every jaw muscle, the first PPT measurement of a session was markedly higher than the last one of that same session. ⋯ The inter-individual variability of PPTs was 2.3 to 9 x higher than the variability observed between trials, sessions or days. The results indicate that the PPT measurement will not be systematically influenced by the time of registration (morning/afternoon) or inbetween consecutive days. In addition, the important inter-individual differences favor the use of longitudinal within-subject studies.
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Verbal rating scales (VRS), composed of ranked pain descriptors, are often employed in pain research. Factors that may influence the subjective pain intensity values, however, are not well established. In this study, 5 common pain descriptor adjectives were represented on a visual analogue scale (VAS) by a group of 80 dental students, by a group of 48 patients undergoing periodontal therapy, and by a group of 31 dental phobic patients. ⋯ No correlation was found with gender. The descriptors did not divide the analogue scale into equal segments. 71% of all subjects gave the adjective "mild" a lower pain intensity representation than the adjective "weak", while the order was reversed among remaining subjects. Findings cast doubt on the reliability of VRS and the data handling methods commonly adopted in clinical pain research.
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In a controlled polysomnographic (PSG) study that we recently performed in our laboratory, we noticed that some patients with a chief complaint of sleep bruxism reported concomitant non-myofascial pain in their masticatory muscles. To study the influence of such pain on the pattern of bruxism motor activity, we re-assessed the 2nd out of 2 consecutive PSG and masseter electromyographic (EMG) recordings of 7 bruxers without pain and 6 bruxers with concomitant jaw muscle pain. ⋯ Although there were no significant differences between both subgroups of bruxers in the number of bruxism bursts per episode and the root-mean-squared EMG level per bruxism burst, bruxers with pain had 40% less bruxism episodes per hour of sleep. This suggests that non-myofascial jaw muscle pain decreases the number of initiations of bruxism episodes, but leaves their contents unaffected.