title: Influence of changing occlusal support on jaw-closing muscle electromyographic activity in healthy men and women.
abstract: OBJECTIVE
  To test whether changes in occlusal support differentially modulate masseter and anterior temporalis muscle electromyographic (EMG) activity during controlled maximal voluntary clenching.
  
  
  METHODS
  Forty-seven healthy subjects (32 M and 15 F, 22.9+/-1.3 years) were recruited. Cotton-rolls were used to modify the occlusal contact relations and were positioned on the right, left, or both sides, and either in the molar or premolar regions, i.e. six different occlusal combinations. Surface EMG activity was recorded bilaterally from the masseter and anterior temporalis area and normalized with respect to maximal voluntary clenching in the intercuspal position. Analysis of variance and the paired t-test were used to test the data.
  
  
  RESULTS
  Normalized EMG activity was influenced by changes in cotton-roll modified occlusal support, and there were differences between muscles (p<0.001). In general, EMG activity decreased in both muscles when occlusal support was moved from the molar to the premolar region. When occlusal support was moved from bilateral to unilateral contacts, EMG activity in the balancing-side anterior temporalis muscle and in bilateral masseter muscles decreased. Unilateral clenching on the molars, but not on the premolars, was associated with lower EMG activity in the balancing-side masseter and always associated with lower EMG activity in the balancing-side anterior temporalis compared to the working side (p<0.05).
  
  
  CONCLUSIONS
  Masseter and anterior temporalis muscles respond differently to changes in occlusal support, which may have implications for stability of the mandible during intense clenching.
authors.affiliation: Department of Oral Anatomy and Physiology and TMD, School of Stomatology, Fourth Military Medical University, Xi'an, China. mqwang@fmmu.edu.cn
authors.forename: Mei-Qing
authors.initials: MQ
authors.lastname: Wang
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: He
authors.forename: Kelun
authors.initials: K
authors.lastname: Wang
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D003766:Dental Occlusion; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008410:Masticatory Muscles / Q000502:physiology*; D008437:Maxilla; D009119:Muscle Contraction / Q000502:physiology*; D012016:Reference Values; D012737:Sex Factors; D055815:Young Adult