title: [Application of near infrared spectroscopy in study of occlusal splints and resistance of masticatory muscles to fatigue pain].
abstract: OBJECTIVE
  To analyze the influence of occlusal splint on resistance capability of masticatory muscles to fatigue.
  
  
  METHODS
  In the study, 25 young male volunteers were randomly divided to 5 groups according to different splint placements: (1) no splint, (2) 1.5 mm thick soft splint, (3) 2 mm thick resin stability splint, (4) 4 mm thick resin stability splint, (5) buccolingual mock splint. Near infrared spectroscopy (NIRS) was used to measure blood oxygen content in human masticatory muscles during constant strong biting before and after the splint placement at seven time points: before, baseline after, 1 week after, and 2 weeks after splint placement, and immediately after, 1 week after, and 5 weeks after removing of splints. The strength of the biting force was maintained constantly at 30% level of the maximum biting force of each subject by biofeedback to the displayed value of an electro-myographic monitor. The time points of muscular fatigue and pain that appeared were recorded and the correlation between the subjective feeling and the NIRS measurement result was analyzed.
  
  
  RESULTS
  The NIRS measurement curve had a point of inflection that had no significant difference with the time point of the muscle pain that appeared. Two weeks after placement of soft splint, the time point of the muscular fatigue and pain that appeared were 2.75 s and 8.00 s delayed respectively compared with that before placement of splint (P<0.01) while they were earlier in the groups of hard splints and there was no significant difference (P>0.05) in the group of mock splint.
  
  
  CONCLUSIONS
  The metabolic status of human masticatory muscles could be monitored in real time by using NIRS; soft splint delayed the appearing of muscle fatigue and muscle pain after two weeks of placement.
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Jiang
authors.forename: Dong-Xu
authors.initials: DX
authors.lastname: Huang
mesh_terms: D000328:Adult; D001732:Bite Force; D004576:Electromyography; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D017090:Occlusal Splints; D010100:Oxygen / Q000097:blood; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D011897:Random Allocation; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D010100:Oxygen