title: The effect of acute unilateral inflammation of the equine temporomandibular joint on the kinematics of mastication.
abstract: BACKGROUND
  Diseases of the temporomandibular joint (TMJ) are well reported in man and some domestic animals other than the horse. The pathophysiology of equine TMJ disease and the effects of disease on the kinematics of mastication are unknown.
  
  
  OBJECTIVE
  To determine whether transient unilateral inflammation of the equine TMJ results in alterations in the masticatory cycle.
  
  
  METHODS
  An experimental controlled study utilising 6 horses of various ages with normal dentition.
  
  
  METHODS
  Each horse was equipped with an optical motion tracking (kinematic) system. Horses were observed chewing grass hay over 3 min intervals. Regardless of the initial side of the power stroke in the masticatory cycle, lipopolysaccharide (LPS) was injected in the left TMJ in each horse and the horses were reassessed after 6 h.
  
  
  RESULTS
  Four horses developed effusion of the injected TMJs; 2 of these also began quidding. All horses injected on the original side of the power stroke switched sides while the 2 injected on the contralateral side did not. All horses developed reduced vertical pitch (vertical opening) of the mandible. Overall, rostrocaudal movement of the mandible did not change; however, the timing of this movement relative to the phase of the masticatory cycle did. Injection with LPS did not affect the amount of lateral movement of the mandible.
  
  
  CONCLUSIONS
  Injection of LPS into the TMJ significantly altered the masticatory cycle compared with baseline values representing avoidance behaviour due to inflammation of the joint, despite which the horses continued to eat using the contralateral mandible. Lipopolysaccharide administration also led to quidding and a loss of feed efficiency (in some individuals).
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: T T
authors.initials: TT
authors.lastname: Smyth
authors.affiliation: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: J L
authors.initials: JL
authors.lastname: Carmalt
authors.affiliation: College of Kinesthesiology, University of Saskatchewan, Saskatoon, Canada.
authors.forename: T T
authors.initials: TT
authors.lastname: Treen
authors.affiliation: College of Kinesthesiology, University of Saskatchewan, Saskatoon, Canada.
authors.forename: J L
authors.initials: JL
authors.lastname: Lanovaz
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D006734:Horse Diseases; D006736:Horses; D007249:Inflammation; D008070:Lipopolysaccharides / Q000633:toxicity; D008409:Mastication / Q000502:physiology*; D013704:Temporomandibular Joint / Q000473:pathology / Q000502:physiology*; D013705:Temporomandibular Joint Disorders / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*
chemical_list: D008070:Lipopolysaccharides
keywords: dentition; horse; mastication; temporomandibular joint