Herring S W, Rafferty K L, Liu Z J, Marshall C D
Department of Orthodontics, University of Washington, Box 357446, Seattle, WA 98195-7446, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2001 Dec;131(1):207-19. doi: 10.1016/s1095-6433(01)00472-x.
Among non-mammalian vertebrates, rigid skulls with tight sutural junctions are associated with high levels of cranial loading. The rigid skulls of mammals presumably act to resist the stresses of mastication. The pig, Sus scrofa, is a generalized ungulate with a diet rich in resistant foods. This report synthesizes previous work using strain gages bonded to the bones and sutures of the braincase, zygomatic arch, jaw joint, and mandible with new studies on the maxilla. Strains were recorded during unrestrained mastication and/or in anesthetized pigs during muscle stimulation. Bone strains were 100-1000 micro epsilon, except in the braincase, but sutural strains were higher, regardless of region. Strain regimes were specific to different regions, indicating that theoretical treatment of the skull as a unitary structure is probably incorrect. Muscle contraction, especially the masseter, caused strain patterns by four mechanisms: (1) direct loading of muscle attachment areas; (2) a compressive reaction force at the jaw joint; (3) bite force loading on the snout and mandible; and (4) movement causing new points of contact between mandible and cranium. Some expected patterns of loading were not seen. Most notably, strains did not differ for right and left chewing, perhaps because pigs have bilateral occlusion and masseter activity.
在非哺乳动物脊椎动物中，具有紧密缝合连接的坚硬头骨与高水平的颅骨负荷相关。哺乳动物的坚硬头骨大概起到抵抗咀嚼压力的作用。猪（Sus scrofa）是一种典型的有蹄类动物，其饮食富含抗性食物。本报告综合了先前使用应变片粘贴在脑壳、颧弓、颌关节和下颌骨的骨骼及缝线上的研究工作，以及对上颌骨的新研究。在无约束咀嚼过程中以及/或者在麻醉猪的肌肉刺激过程中记录应变。除脑壳外，骨应变在100 - 1000微应变之间，但缝线应变更高，且与区域无关。应变模式因不同区域而异，这表明将头骨视为单一结构的理论处理可能是不正确的。肌肉收缩，尤其是咬肌，通过四种机制引起应变模式：（1）肌肉附着区域的直接负荷；（2）颌关节处的压缩反作用力；（3）口鼻部和下颌骨上的咬合力负荷；（4）运动导致下颌骨与颅骨之间产生新的接触点。一些预期的负荷模式未被观察到。最显著的是，左右咀嚼时的应变没有差异，这可能是因为猪具有双侧咬合和咬肌活动。
