title: Investigating activity of masticatory muscles in patients with hypermobile temporomandibular joints by using EMG.
abstract: BACKGROUND
  Temporomandibular joint hypermobility (TMJH) can manifest higher range of motions in mandible. The aim of this study was to investigate and compare the activity of masticatory muscle of TMJs in healthy individuals and patients with mild, moderate and severe TMJH.
  
  
  METHODS
  In this clinical study, 69 patients (between the ages of 22 to 42) with manifestation of TMJH were included. The patients were divided into three groups based on their maximum mouth opening (MMO): (light) with MMO of 50-55 mm; (moderate) with MMO between 55 to 65 mm; and (severe) with MMO >65 mm. Also, 20 healthy people with profiled tomography in the last 6 months were invited as control group (healthy) with normal MMO (<50 mm). All the groups subjected to electromyogram (EMG) in 2 steps: maximal voluntary clenching (MVC) of the jaws; and during chewing of bread by using one side of the jaws voluntary. The collected data were analyzed by Student T-test and Chi-Square tests using SPSS software version 15 at significant level of 0.05.
  
  
  RESULTS
  Both TMJs of light, moderate and severe groups showed significant differences in frequency, time of activity and rest in comparison with healthy group during chewing and MVC (all p values < 0.01).
  
  
  CONCLUSIONS
  Masticatory muscles activity reduced in relation with the severity of TMJH and higher excessive mouth opening. Key words:Electromyography, joint hypermobility, mouth opening, tempormandibular joint.
authors.affiliation: Dentistry Student, Dental Students Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Amin
authors.initials: A
authors.lastname: Davoudi
authors.affiliation: Assistant Professor of Oral and Maxillofacial Surgery Dental Implants Research Center, Department of Oral and Maxillofacial Surgery, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Haghighat
authors.affiliation: MD Professor of Oral and Maxillofacial Surgery, Department of Surgical Dentistry and Maxillofacial Surgery in plastic and reconstructive surgery of head and neck, Poltava, Ukraine.
authors.forename: Oleg
authors.initials: O
authors.lastname: Rybalov
authors.affiliation: Assistant Professor, Torabinejad Research Center and Departments of Endodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Elham
authors.initials: E
authors.lastname: Shadmehr
authors.affiliation: Dentist, Private practice, Isfahan, Iran.
authors.forename: Amin
authors.initials: A
authors.lastname: Hatami