The relationship between selective sleep deprivation, nocturnal jaw-muscleactivity and pain in heal thy men

The relationship between nocturnal jaw-muscle activity and temporomandibula r disorders (TMD) is still controversial. The aim of this study was to inve stigate the effect of selective slow wave sleep (SWS = non-rapid-eye-moveme nt (NREM) stage 3 + 4) deprivation on jaw-muscle activity using a new autom atic system. Ten healthy men without signs of symptoms of TMD participated. The subjects slept in the laboratory for six continuous nights including o ne adjustment night, one baseline night, three nights with experimental sle ep deprivation and one recovery night. Polysomnographic recordings:of elect roencephalography (EEG) and electromyography (EMG) were obtained for recogn ition of sleep stages and masseter muscle activity. During the three experi mental nights, computer-controlled sound stimulation (60-90 dB(A), 1000 Hz) were given as long as the subjects were in SWS. Maximum voluntary occlusal force (MVOF), pain pressure threshold (PPT) and visual analogue scales (VA S) were used to assess the state of the masseter muscles every morning and evening during the study period. The results showed that the time spent in SWS was significantly decreased during the first sleep deprivation night, b ut there were no significant effects on nocturnal EMG activity (i.e. the nu mbers of bruxism episodes per hour of sleep, bruxism bursts per episodes br uxism bursts per hour of sleep), MVOF, VAS or PPT. Furthermore, the automat ic system only deprived the SWS in five subjects for the following two nigh ts although the sound stimulation was given at the maximum intensity. These results suggest that deprivation of SWS may not interact immediately with nocturnal jaw-muscle activity and jaw-muscle pain.