title: Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing.
abstract: OBJECTIVE
  This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects.
  
  
  METHODS
  The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head-neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test.
  
  
  RESULTS
  EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups.
  
  
  CONCLUSIONS
  The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.
authors.affiliation: Institute for Research in Dental Sciences, Faculty of Dentistry, University of Chile , Santiago , Chile.
authors.forename: Aler Daniel
authors.initials: AD
authors.lastname: Fuentes
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Miralles
authors.forename: Hugo
authors.initials: H
authors.lastname: Santander
authors.forename: Mario Felipe
authors.initials: MF
authors.lastname: Gutiérrez
authors.forename: Ricardo
authors.initials: R
authors.lastname: Bull
authors.forename: Conchita
authors.initials: C
authors.lastname: Martin
mesh_terms: D002182:Candy; D003768:Dental Occlusion, Centric; D004576:Electromyography / Q000295:instrumentation / Q000379:methods*; D005260:Female; D019416:Head Movements / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D027845:Malus; D008409:Mastication / Q000502:physiology*; D008963:Molar / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology*; D013703:Temporal Muscle / Q000502:physiology*; D055815:Young Adult
keywords: Electromyography; mastication; masticatory muscles; neck muscles