A pilot study of ambulatory masticatory muscle activities in temporomandibular joint disorders diagnostic groups

L. R. Iwasaki, Y. M. Gonzalez, H. Liu, D. B. Marx, L. M. Gallo, J. C. Nickel

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Objective: To determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups. Setting and sample population: Seventy-one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo. Material and methods: Research diagnostic criteria and imaging data were used to categorize subjects according to the presence/absence (+/-) of TMJ disc placement (DD) and chronic pain (P) (+DD+P, n = 18; +DD-P, n = 14; -DD-P, n = 39). Electromyographic (EMG)/bite-force calibrations determined subject-specific masseter and temporalis muscle activities per 20 N bite-force (T20N, μV). Over 3 days and nights, subjects collected EMG recordings. Duty factors (DFs, % of recording time) were determined based on threshold intervals (5-9, 10-24, 25-49, 50-79, ≥80% T20N). anova and Tukey-Kramer post hoc tests identified 1) diagnostic group differences in T20N and 2) the effects of diagnostic group, gender, time and interval on muscle DFs. Results: Mean (± SE) temporalis T20N in +DD+P subjects was significantly higher (71.4 ± 8.8 μV) than masseter T20N in these subjects (19.6 ± 8.8 μV; p = 0.001) and in -DD-P subjects (25.3 ± 6.0 μV, p = 0.0007). Masseter DFs at 5-9% T20N were significantly higher in +DD-P women (3.48%) than +DD-P men (0.85%) and women and men in both other diagnostic groups (all p < 0.03), and in +DD+P women (2.00%) compared to -DD-P men (0.83%; p = 0.029). Night-time DFs at 5-9% T20N in +DD-P women (1.97%) were significantly higher than in -DD-P men (0.47%) and women (0.24%; all p < 0.01). Conclusions: Between-group differences were found in masticatory muscle activities in both laboratory and natural environmental settings.

Original languageEnglish (US)
Pages (from-to)146-155
Number of pages10
JournalOrthodontics and Craniofacial Research
Issue numberS1
StatePublished - Apr 1 2015
Externally publishedYes


  • Ambulatory
  • Duty factor
  • Electromyographic
  • Masticatory muscle
  • Temporomandibular joint disorder

ASJC Scopus subject areas

  • Orthodontics
  • Surgery
  • Oral Surgery
  • Otorhinolaryngology


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