title: Variability of musculoskeletal strain on dentists: an electromyographic and goniometric study.
abstract: BACKGROUND
  Dentists and hygienists are strongly affected by musculoskeletal disorders (MSDs). As workstation concepts are supported by subjective arguments only, the aim of this study was to use objective measurements to compare the variability of strain in various concepts: a dental chair equipped with a cart or an over-the-patient delivery system without an assistant, and Dr Daryl Beach's concept with an assistant.
  
  
  METHODS
  Goniometric and electromyographic recordings were made on 8 subjects, during a scaling operation. The electrical activity of their trapezius and lumbar muscles was compared, as were their cervical and lumbar ranges of motion.
  
  
  RESULTS
  The results showed that there was a wide variability depending on the workstation. However, the Beach concept tended to reduce physical strain on most parameters: duration of left lumbar muscle activity (2% compared to 15% of time spent in > 10% maximal voluntary contraction, MVC), time spent in cervical side bending (4% compared to 30%), cervical flexion of > 20° (9% compared to 40%), and left trapezius activity (9% of time spent > 10% MVC compared to 28%).
  
  
  CONCLUSIONS
  Practitioners and students should adjust their workstations to reduce the prevalence of MSDs.
authors.affiliation: Department of Public Health, Université Paul Sabatier, Toulouse, France. d.blanc3@gmail.com.
authors.forename: David
authors.initials: D
authors.lastname: Blanc
authors.affiliation: Department of Public Health, Université Paul Sabatier, Toulouse, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Farre
authors.affiliation: Department of Public Health, Université Paul Sabatier, Toulouse, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Hamel
mesh_terms: D000328:Adult; D000368:Aged; D003748:Dental Equipment; D003815:Dentists; D004576:Electromyography; D004867:Equipment Design; D006804:Ergonomics; D005260:Female; D006801:Humans; D007374:Interior Design and Furnishings; D007596:Joints / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D059352:Musculoskeletal Pain / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D009784:Occupational Diseases / Q000517:prevention & control*; D016272:Occupational Health; D011187:Posture / Q000502:physiology*; D013180:Sprains and Strains / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D017132:Workplace; D055815:Young Adult