 - for the sleep bruxism Group: subjects have to fulfill the clinical criteria of the American Academy of Sleep Medicine sleeping partners Report of grinding sounds during sleep within the last 6 months, plus at least one of the following symptoms: abnormal attrition of the teeth or shiny spots on dental restorations, hypertrophy of the masseteric muscle upon palpation, andor self-report of muscle fatigue on awakening. In addition to the clinical criteria for sleep bruxism diagnosis, the following polysomnographic criteria have to be present: bruxism episodeshr 4, bruxism bursthr 25, at least one episode of grinding per sleep period 