title: Analysis of muscle hardness in patients with masticatory myofascial pain.
abstract: OBJECTIVE
  The aim of the present study was to access any changes in the muscle hardness of the masseter muscle between normal subjects and patients with myofascial pain during brief sustained isometric contractions at various bite force levels, and to compare muscle hardness, especially in terms of the recovery phase, after a clenching task.
  
  
  METHODS
  Ten patients with masticatory myofascial pain and 10 age- and weight-matched normal healthy controls participated in this study. First, the hardness of the right masseter muscle was measured at the bite force of 0, 3, 6, and 9 kgf with a hand-held hardness meter. Then, the subjects were requested to exert a 9 kgf-clenching task for 30 seconds. The muscle hardness was again measured at 5, 30, and 120 seconds after the task, and the data obtained were compared with the muscle hardness before the clenching task.
  
  
  RESULTS
  The results showed that there was no significant difference between the patients and the normal controls, while the muscle hardness increased with contraction in all subjects. The present findings also showed that the patients had a delayed return to baseline after the clenching task compared with the normal subjects, although an immediate increase after the clenching task was seen in all subjects.
  
  
  CONCLUSIONS
  The results indicated that patients with masticatory myofascial pain have different muscle properties in the recovery phase after contraction, probably because of a slower intramuscular reperfusion.
authors.affiliation: Professor, Department of Oral and Maxillofacial Surgery, Miyazaki Medical College, Miyazaki, Japan. kojikash@med.miyazaki-u.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Kashima
authors.forename: Kaori
authors.initials: K
authors.lastname: Igawa
authors.forename: Sho
authors.initials: S
authors.lastname: Maeda
authors.forename: Sumio
authors.initials: S
authors.lastname: Sakoda
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D016022:Case-Control Studies; D005260:Female; D006245:Hardness Tests / Q000379:methods; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology; D009129:Muscle Tonus; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000503:physiopathology*