Bonin S J, Clayton H M, Lanovaz J L, Johnston T
McPhail Equine Performance Center, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48854, USA.
Equine Vet J. 2007 May;39(3):258-62. doi: 10.2746/042516407x157792.
Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published.
The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets.
An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle.
Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds.
The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets.
These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing.
以往研究表明，颞下颌关节（TMJ）的运动学取决于所咀嚼食物的类型，但关于马匹咀嚼不同饲料时颞下颌关节运动的精确测量尚未见报道。
与颗粒饲料相比，马匹咀嚼干草时颞下颌关节的运动范围更大。
使用光学运动捕捉系统跟踪7匹马在咀嚼干草和颗粒饲料时颅骨和下颌骨上的皮肤标记物。在第四前磨牙水平的下颌骨之间的中线上创建一个虚拟标记物，以代表咀嚼周期中下颌骨相对于颅骨的整体运动。
咀嚼干草时咀嚼周期的频率低于颗粒饲料。与颗粒饲料相比，咀嚼干草时虚拟下颌标记物在所有三个方向上的偏移都显著更大。咀嚼这两种饲料时，咀嚼周期中虚拟下颌标记物的平均速度相同。
咀嚼干草时，下颌骨的内外侧位移范围足以使上下牙弓完全咬合接触，而咀嚼颗粒饲料时则不然。
这些发现支持了以下观点，即食用高浓缩饲料的马匹可能需要更频繁的牙齿预防性检查和治疗，以避免咀嚼时下颌运动较小导致牙齿排列不齐。
