F. Guitard

Identification of a Sleep Bruxism Subgroup with a Higher Risk of Pain

Sleep bruxism research diagnostic criteria (SB-RDC) have been applied since 1996. This study was performed to validate these criteria and to challenge the hypothesis that pain is associated with lower frequencies of orofacial activities. Polygraphic recordings were made of 100 individuals presenting with a clinical diagnosis of sleep bruxism and 43 control individuals. TwoStep Cluster analyses (SPSS) were performed with sleep bruxism variables to reveal groupings among sleep bruxers and control individuals. Participants completed questionnaires during screening, diagnosis, and recording sessions. Cluster analysis identified three subgroups of sleep bruxers. Interestingly, 45 of the 46 sleep bruxers with values below SB-RDC were classified in the low-frequency cluster. These individuals were more likely to complain of pain and fatigue of masticatory muscles than were the higher-frequency sleep bruxers (odds ratios > 3.9, p < 0.01). Sleep bruxers were distributed among three heterogeneous groups. Sleep bruxers with low frequencies of orofacial activities were more at risk of reporting pain.

Evidence that Experimentally Induced Sleep Bruxism is a Consequence of Transient Arousal

Spontaneous rhythmic masticatory muscle activity (RMMA) during sleep occurs more frequently following spontaneous transient micro-arousal in patients with sleep bruxism (SB) and normal controls. Here, we tested the hypothesis that an experimental arousal would be followed by an increase in RMMA. We identified RMMA on polygraphic recordings taken before and after sensory stimulation to induce experimental arousal in eight SB patients and eight matched normal subjects. The rate of experimental arousal and the level of resting electromyographic activity in masseter and suprahyoid muscles during sleep did not differ between the groups. In both, muscle tone and heart rate increased during the experimental arousal. Although post-arousal RMMA occurred in all SB patients, it was seen in only one normal subject. Moreover, tooth-grinding occurred during 71% of the evoked RMMA in SB patients. These results support the hypothesis that SB is an exaggerated form of oromotor activity associated with sleep micro-arousal.

Quantitative Polygraphic Controlled Study on Efficacy and Safety of Oral Splint Devices in Tooth-grinding Subjects

The efficacy of occlusal splints in diminishing muscle activity and tooth-grinding damage remains controversial. The objective of this study was to compare the efficacy and safety of an occlusal splint (OS) vs. a palatal control device (PCD). Nine subjects with sleep bruxism (SB) participated in this randomized study. Sleep laboratory recordings were made on the second night to establish baseline data. Patients then wore each of the splints in the sleep laboratory for recording nights three and four, two weeks apart, according to a crossover design. A statistically significant reduction in the number of SB episodes per hour (decrease of 41%, p = 0.05) and SB bursts per hour (decrease of 40%, p < 0.05) was observed with the two devices. Both oral devices also showed 50% fewer episodes with grinding noise (p = 0.06). No difference was observed between the devices. Moreover, no changes in respiratory variables were observed. Both devices reduced muscle activity associated with SB.

Variability in sleep bruxism activity over time

Sleep bruxism (SB) is an oral activity associated with jaw movements and tooth grinding. Sleep bruxism is believed to be highly variable over time, with subjects showing no activity on some nights and intense activity on others. Assessment of SB variability in individual patients is necessary for clinical trials designed to estimate the efficacy of SB management strategies. The present study analysed SB night‐to‐night variability over time in nine moderate to severe SB patients. Excluding the first night for habituation, a total of 37 nights were analysed, with a range of 2–8 nights per subject. The interval between the first and the last recording was between 2 months and 7.5 years. The outcomes were the number of SB episodes per hour, number of SB bursts per hour and number of SB episodes with grinding noise. The within subject variability of the three SB oromotor outcomes was evaluated using standard deviation (SD) and coefficient of variation. To verify the diagnosis of subjects over time, the values of the oromotor outcomes were compared with a standard research diagnostic cut‐off: (1) Number of SB episodes per hour >4, (2) Number of SB bursts per hour >25, (3) Number of SB episodes with noise per night >1 ( Lavigne et al. 1996 ). The mean coefficient of variation for the nine subjects was 25.3% for SB episodes per hour, 30.4% for SB bursts per hour and 53.5% for episodes with noise. Linear regression showed that the number of SB episodes per hour of stages 1 and 2 explains a large proportion of the variability. The SB diagnosis remained constant over time for every subject: 35 nights over 37 respected criteria 1 and 2, while grinding was present every night. These results indicate that while the SB diagnostic remains relatively constant over time in moderate to severe sleep bruxers, individual variability could be important in some SB patients.

Experimental pain perception remains equally active over all sleep stages

&NA; The literature on sensory perception during sleep suggests that light sleep (Stage 2) is more responsive to external sensory stimulation (e.g. sound, electrical shock) than deep sleep (Stages 3 and 4) and REM sleep. The main objective of this study was to characterize the specificity of nociceptive stimulation to trigger sleep arousal–awakening over all sleep stages. Thirteen healthy adults (e.g. without pain or sleep problems; six female and seven male of a mean age of 24.2±1.3 years) were included in the study. The responses to noxious intramuscular 5% hypertonic infusion were compared to innocuous vibrotactile and to respective control stimulations: isotonic infusion and auditory stimulations. These stimulations were applied during wakefulness and were repeated during sleep. Polygraphic signals (e.g. brain activity, heart rate) signals were recorded to score sleep arousal over all sleep stages. A subjective assessment of sleep quality was made on next morning. No overnight sensitization or habituation occurred with any of the experimental stimulations. The vibratory–auditory stimulations and the noxious hypertonic infusions triggered significantly (P<0.05) more awakenings in sleep Stage 2 and in REM than their respective control stimulations. In sleep Stage 2, both vibratory+auditory stimulations and the noxious hypertonic infusions has the same awakening response frequency (≈30%), however, with the noxious infusions the response frequency were similar in sleep Stages 3 and 4 (P<0.05) and in REM (trend). Compared to the baseline night, sleep quality was lower following the night with noxious stimulation (90.1±2.7 and 73.3±7.4 mm, respectively; P<0.03). These data suggest that pain during sleep could trigger a sleep awaking response over all sleep stages and not only in light sleep.

Lower number of K-complexes and K-alphas in sleep bruxism: a controlled quantitative study

OBJECTIVES Although patients with sleep bruxism (SB) show a higher incidence of rhythmic masticatory muscle activity (RMMA) during sleep than matched normal controls, they are good sleepers. Sleep macrostructure (e.g. total sleep time, sleep latency, number of awakenings or sleep stage shifts and sleep stage duration) is similar between groups. Differences in sleep microstructure between SB patients and normals have been investigated only in few studies. The aim of the present study was to quantify number of microarousals, K-complexes, K-alphas, EEG spindles, and the density of slow wave activity, in both groups, in order to better understand the pathophysiology of SB. METHODS Ten normal sleepers were matched for age and gender with 10 patients who exhibited frequent tooth-grinding during sleep. Using quantitative polysomnographic measures, we compared the above-mentioned sleep variables in both groups. Data are presented as indices for total sleep and for consecutive non-rapid eye movement (non-REM) episodes over non-REM to rapid eye movement (REM) cycles and per hour of sleep. RESULTS SB patients showed 6 times more RMMA episodes per hour of sleep than normals (P<0.001), with a higher frequency in the second and third non-REM to REM cycles. SB patients presented 42.7% fewer K-complexes per hour of stage 2 sleep, but only normals showed a decline from the first to fourth non-REM episode. Only 24% of SB-RMMA episodes were associated with K-complexes in 60 s. The number of K-alphas was 61% lower in SB patients, no change across non-REM episodes was noted. While no difference in electroencephalographic (EEG) spindles or slow wave activity (SWA) was observed between groups, EEG spindles increased and SWA decreased linearly over consecutive non-REM to REM cycles. CONCLUSIONS According to our observations, good sleep in SB patients is characterized by a low incidence of K-complexes or K-alphas and by the absence of any difference in other sleep microstructure variables or SWA.

Pain and denture condition in edentulous orodyskinesia: Comparisons with tardive dyskinesia and control subjects†

Edentulous orodyskinesia (ED) is a neglected source of aimless oral movements that may be confused with tardive dyskinesia (TD). We attempted to clarify the clinical features, significance, and orodental factors in relation to ED. Fourteen ED subjects, 13 TD patients, and 15 age‐matched controls self‐assessed their oral pain perception, condition, and function using a visual analogue scale. Dyskinesias were classified and rated by a neurologist. Perioral thermal and pressure pain threshold studies, and a standardized orodental examination, were conducted blind to subject group. The perceived oral pain level was low in all groups, and those reporting a significant intensity level of pain (≥50th percentile) were few. The pain thresholds in both dyskinetic groups were comparable to control values. All ED cases wore a complete set of dentures, considered a current source of problems by 85.7% of them. ED cases commonly displayed inadequate dental occlusal relationship (P = 0.014 vs. controls; P = 0.036 vs. TD) and an overclosed vertical dimension (P = 0.006 vs. controls) as well as unstable and unretentive dentures. ED was limited to the oral region, spared the tongue when the mouth is open, and was never severe in our patients. ED has distinct movement characteristics and is often associated with inadequate dentures and biomechanical sources of denture instability. The contribution of the foregoing findings to the expression of oral dyskinesia warrants further studies.