title: Normalizing surface electromyographic measures of the masticatory muscles: Comparison of two different methods for clinical purpose.
abstract: OBJECTIVE
  To compare a new normalization technique (wax pad, WAX) with the currently utilized cotton roll (COT) method in surface electromyography (sEMG) of the masticatory muscles.
  
  
  METHODS
  sEMG of the masseter and anterior temporalis muscles of 23 subjects was recorded while performing two repetitions of 5s maximum voluntary clenches (MVC) on COT and WAX. For each task, the mean value of sEMG amplitude and its coefficient of variation were calculated, and the differences between the two repetitions computed. The standard error of measurement (SEM) was calculated. For each subject and muscle, the COT-to-WAX maximum activity increment was computed. Participant preference between tasks was also recorded.
  
  
  RESULTS
  WAX MVC tasks had larger maximum EMG amplitude than COT MVC tasks (P<0.001), with COT-to-WAX maximum amplitude increments of 61% (temporalis) and 94% (masseter) (P=0.006). WAX MVC had better test-retest repeatability than COT. For both MVC modalities, the mean amplitude (P>0.391) and its coefficient of variation were unchanged (P>0.180). The WAX task was the more comfortable for 18/23 subjects (P=0.007).
  
  
  CONCLUSIONS
  WAX normalization ensures the same stability level of maximum EMG amplitude as COT normalization, but it is more repeatable, elicits larger maximum muscular contraction, and is felt to be more comfortable by subjects.
authors.affiliation: Department of Biomedical Sciences for Health, Functional Anatomy Research Center (FARC), Università degli Studi di Milano, Milano, Italy; Private Practice, SST Dental Clinic, Segrate, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mapelli
authors.affiliation: Department of Biomedical Sciences for Health, Functional Anatomy Research Center (FARC), Università degli Studi di Milano, Milano, Italy; Private Practice, SST Dental Clinic, Segrate, Italy.
authors.forename: Gianluca Martino
authors.initials: GM
authors.lastname: Tartaglia
authors.affiliation: Department of Oral and Maxillofacial Surgery, University of California and San Francisco Veterans Affairs, San Francisco, CA, United States.
authors.forename: Stephen Thaddeus
authors.initials: ST
authors.lastname: Connelly
authors.affiliation: Department of Biomedical Sciences for Health, Functional Anatomy Research Center (FARC), Università degli Studi di Milano, Milano, Italy.
authors.forename: Virgilio Ferruccio
authors.initials: VF
authors.lastname: Ferrario
authors.affiliation: Department of Ophthalmology, Otorhinolaryngology, and Head and Neck Surgery, School of Medicine, Ribeirão Preto, Craniofacial Research Support Centre, University of São Paulo, Brazil.
authors.forename: Claudia Maria
authors.initials: CM
authors.lastname: De Felicio
authors.affiliation: Department of Biomedical Sciences for Health, Functional Anatomy Research Center (FARC), Università degli Studi di Milano, Milano, Italy; Institute of Bioimaging and Molecular Physiology, National Research Council, Segrate, Italy. Electronic address: chiarella.sforza@unimi.it.
authors.forename: Chiarella
authors.initials: C
authors.lastname: Sforza
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D004576:Electromyography / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology*; D008875:Middle Aged; D009119:Muscle Contraction; D012016:Reference Values
keywords: Dental clinics; Dental occlusion; Masticatory muscles; Proprioception; Reference standards; Surface electromyography