Kinematics of the equine temporomandibular joint.
OBJECTIVE
To develop a method of measuring 3-dimensional kinematics of the temporomandibular joint (TMJ) in horses chewing sweet feed.


METHODS
4 mature horses that had good dental health.


METHODS
Markers attached to the skin over the skull and mandible were tracked by an optical tracking system. Movements of the mandible relative to the skull were described in terms of 3 rotations and 3 translations. A virtual marker was created on the midline between the rami of the mandibles at the level of the rostral end of the facial crest to facilitate observation of mandibular movements.


RESULTS
During the opening stroke, the virtual midline mandibular marker moved ventrally, laterally toward the chewing side, and slightly caudally. During the closing stroke, the marker moved dorsally, medially, and slightly rostrally. During the power stroke, the mandible slid medially and dorsally as the mandibular cheek teeth moved across the occlusal surface of the maxillary cheek teeth. The 4 horses had similar chewing patterns, but the amplitudes varied among horses.


CONCLUSIONS
The TMJ allows considerable mobility of the mandible relative to the skull during chewing. The method presented in this report can be used to compare the range of motion of the TMJ among horses with TMJ disease or dental irregularities or within an individual horse before and after dental procedures.
Bonin
Stephanie J
SJ
Mary Anne McPhail Equine Performance Center, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, 48824, USA.
Clayton
Hilary M
HM
Lanovaz
Joel L
JL
Johnson
Thomas J
TJ
D000818:Animals; D001696:Biomechanical Phenomena; D006736:Horses / Q000502:physiology*; D008409:Mastication / Q000502:physiology; D013704:Temporomandibular Joint / Q000502:physiology*