The purpose of this study is to test whether severe masticatory muscle spasms during sleep
(e.g. teeth clenching and grinding, known as "bruxism" in technical jargon) demonstrably
decrease after application of botulinum toxin type A (Xeomin®). Xeomin® has so far been used
to relieve spasms of other muscles and is an approved drug in Switzerland. This study is now
intended to test the suitability of this drug for relaxation of the masseter muscle.