Masticatory muscle activity assessment and reliability of a portable electromyographic instrument

Statement of problem. Masticatory muscle hyperactivity is thought to produc e muscle pain and tension headaches and can cause excessive wear or breakag e of restorative dental materials used in the treatment of prosthodontic pa tients. The quantification and identification of this type of activity is a n important consideration in the preoperative diagnosis and treatment plann ing phase of prosthodontic cart. Purpose. This study investigated the quantification process in complete den ture/overdenture patients with natural mandibular tooth abutments and explo red the reliability of instrumentation used to assess this parafunctional a ctivity. Material and methods. The nocturnal EMG activity in asymptomatic c omplete denture/overdenture subjects was assessed with and without prosthes es worn during sleep. Because of the large variance within and between subj ects, the investigators evaluated the reliability of the 3 instruments used to test nocturnal EMG activity in the sample. Results. Electromyographic activity data of denture/overdenture subjects re vealed no differences between prostheses worn versus not worn during sleep but demonstrated a very large variance factor. Further investigation of the instrumentation demonstrated a consistent in vitro as well as in vivo reli ability in controlled laboratory studies. Conclusion. The portable EMG instrumentation used in this study revealed a large, uncontrollable variance factor within and between subjects that grea tly complicated the diagnosis of parafunctional activity in prosthodontic p atients.