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The aim was to test the hypothesis of a direct association between sleep-disordered breathing and sleep bruxism. The frequency of masseter contraction (MC) episodes and rhythmic jaw movements (RJM) was measured in patients with mild and moderate obstructive sleep apnoea (OSA). The diagnosis of sleep bruxism was made from a combination of questionnaire, clinical observation and all-night polysomnographic recording which included masseter electromyography. A total of 21 patients (19 males/two females, mean age 40.0 years+/-9.2 SD) were randomly selected from a provisional diagnosis of snoring and OSA by a sleep physician. In the patients with mild OSA [n=11, mean apnoea hypopnoea index (AHI)=8.0+/-4.1 SD, body mass index (BMI)=29.1+/-5.0], the diagnosis of sleep bruxism was made in six out of 11 patients (54%); similarly, four out of 10 patients (40%) with moderate OSA (n=10, mean AHI=34.7+/-19.1, BMI=30.6+/-5.0) were identified as bruxists. Although the combination of clinical, subjective estimation and nocturnal electromyographic recording of masseter muscle might provide a more solid base for the diagnosis of sleep bruxism, the result is biased by the variation in the bruxing activity. MC episodes were associated with the termination of apnoea or hypopnoea episodes in only 3.5% of the mild group and 14.4% of the moderate group (p<0.05). It appears that sleep bruxism is rarely directly associated with apnoeic events, but is rather related to the disturbed sleep of OSA patients.

Study Objectives: To measure the effects of a titratable anterior mandibular repositioner on airway size and Obstructive Sleep Apnea (OSA) and to evaluate its compliance., Design: Before and after insertion sleep studies were obtained in a total of 38 OSA patients of varying severity from three different sites. Covert compliance was measured by means of a newly-developed, miniaturized, temperature-sensitive, imbedded monitor. Validity testing was completed in six adult volunteers who wore monitors imbedded into small acrylic appliances., Measurements and Results: The mean RDI before treatment was 32.6 (SEM 2.1) and after the insertion of the appliance, the RDI was reduced to 12.1 (SEM 1.7, p<0.001). RDI was reduced to less than 15/hour in 80% of a group of moderate OSA patients (RDI 15 to 30) and in 61% of a group of severe OSA patients (RDI > 30) with respect to baseline RDI. Fiber optic video endoscopy was performed on 9 OSA patients with and without the appliance. No significant differences in hypopharynx or oropharynx cross sectional areas were found, but at the level of the velopharynx, the airway size was significantly increased (p<0.05). The index of agreement was 0.99 between the monitor clock time and the subject's log sheets. Compliance data from eight OSA subjects instructed to wear the appliance during sleep indicated that it was worn for a mean of 6.8 hours with a range of 5.6 to 7.5 hours per night., Conclusion: The titratable adjustable mandibular advancement appliance, made from thermoelastic acrylic, significantly reduces RDI in moderate to severe OSA patients, has a direct effect on airway size and is well worn throughout the night.

Vertical mandibular posture is thought to be related to narrowing of the upper airway, because mouth opening is associated with an inferior-posterior movement of the mandible and the tongue which influences pharyngeal airway patency. To test whether the mandibular posture is related to the occurrence and/or termination of obstructive sleep apnoea (OSA), the vertical mandibular position was recorded intraorally using a magnet sensor during a standard sleep study in seven patients with OSA. Measurements were recorded during sleep both in the supine and lateral recumbent positions. The percentage of total sleep time spent with mandibular opening greater than 5 mm was significantly larger (p<0.001) in patients with OSA (69.3+/-23.3%) compared with our previous results obtained from healthy adults without OSA (11.1+/-11.6%). The stage of sleep affected the vertical mandibular posture during sleep in the supine position, but not in the lateral recumbent position in patients with OSA. In non-rapid eye-movement sleep, mandibular opening increased progressively during apnoeic episodes and decreased at the termination of apnoeic episodes. In contrast, no significant change in mandibular posture occurred in apnoeic episodes during rapid eye-movement sleep. It was concluded that the vertical mandibular posture is more open during sleep in patients with OSA than in healthy adults and that mandibular opening increases progressively during apnoeic episodes and decreases at the termination of those episodes.

To test whether the mandible opens more during deep sleep and whether the mandibular position is affected by body position during sleep, the vertical mandibular position was recorded intraorally using a magnet sensor at the same time as a standard sleep study in seven normal healthy male adults. Measurements were recorded during the period before sleep onset (WAKE) and during sleep. Two-way ANOVA showed that vertical mandibular position was significantly affected by sleep stage but not by body position (supine vs lateral recumbent). The proportion of time during which the mandible was in a near-closed position (0-2.5 mm) significantly and progressively decreased, and significantly more time was spent at wider gaps (2.5-5 mm) as non-rapid-eye-movement (NREM) sleep deepened. In REM sleep, the proportion of time during which the mandible was at wider gaps was significantly greater than in WAKE and stage 1 (but not later stages) of NREM sleep. It was concluded that mandibular posture during sleep in healthy adults is significantly influenced by sleep stage but not by body position. Mandibular opening progressively increases with the depth of NREM sleep stage, and the mandible is more open in REM sleep than in light NREM sleep.

The purpose of this study was to investigate the effect of the beta-adrenergic antagonist, propranolol, on the nocturnal masseter muscle activity of a heavy sleep bruxist. Three all-night polysomnographic registrations were performed with bilateral masseter muscle EMG recordings. The first night study served as the baseline night, the second night registration was performed after total sleep deprivation and the third night registration was made with propranolol. Sleep deprivation decreased the masseter contraction (MC) index by 61% and propranolol by 72% when compared to the level of the baseline night. This preliminary observation is in line with our hypothesis suggesting a link between autonomic regulation of circulation and rhythmic activation of masticatory muscles, especially when associated with body movements during sleep.

To examine the hypothesis of disturbed autonomic function, non-invasive cardiovascular reflex tests were performed on 11 sleep bruxists in the waking state. The tests included the Valsalva manoeuvre, a deep-breathing test, and an orthostatic test (standing up). The R-R intervals were monitored continuously, and blood pressure was measured non-invasively and continuously using the Finapres method. In total, 64% of bruxists showed abnormalities in at least two variables reflecting the cardiovascular autonomic function. Abnormalities were found in blood pressure regulation during the Valsalva strain, and in the immediate biphasic heart rate response during standing up, but not in the vagally mediated deep-breathing difference. These findings suggest that bruxism is accompanied by abnormalities in autonomic function, particularly in sympathetic vasoconstrictor function.

The purpose of this study was to compare the effects of a modified Herbst appliance (mHA) and a muscle relaxation appliance (MR) on nocturnal breathing and body movement activity in patients with obstructive sleep apnoea syndrome (OSAS). To increase the airway space posterior to the tongue base without severely affecting the craniomandibular joint, the mHA was adjusted to anchor the mandible at 50% of maximum protrusion. MR producing an occlusal coverage but no protrusion served as a control appliance. All-night static charge-sensitive bed (SCSB) and finger oximeter recordings were done to six male patients in three conditions: first without dental device and then with mHA and with MR, in a random order, after a 2 month period of habituation. The oxyhaemoglobin desaturation events were 44.7 h-1 of recording observed during the control night, 29.6 h-1 with mHA (P = 0.087). The frequency of body movements decreased from 34.9 to 20.4 h-1 (P = 0.0079), respectively. MR had no significant effects either on the frequency of the desaturation events or the frequency of body movements, but the increased respiratory resistance breathing, indicating presence of partial upper airway obstruction, was reduced from 14.3 to 6.9% of the time in bed (P = 0.022). We conclude that 50% protrusion chosen for these experiments, produced with a mHA, brought about some alleviation of upper airway obstruction in our preselected patients, but did not lead to sufficient control of apnoea. The reduction of partial upper airway obstruction induced with a MR warrants further studies in a larger patient population.

To investigate the nocturnal motor activity associated with teethgrinding, 12 patients and 12 controls were recorded during sleep with the masseter muscle electromyogram (EMG) and the static charge-sensitive bed movement sensor. The frequency of body movements per hour was 21.4 in the teethgrinders and 14.0 (P less than .05) in the control group. The movement time was 87.4 seconds per hour in the teethgrinders and 55.2 seconds per hour (P less than .01) in the controls. The differences were most obvious in the body movements with temporal association to EMG elevation during the first stage of sleep. The number of isolated EMG elevations showed great interindividual variation and did not differ between groups. The teethgrinders complained more frequently of delayed sleep onset and daytime tiredness. The data suggest that the motor disturbance of teethgrinding is not limited to masticatory muscles but is manifested also as increased general body movement activity.