Department of Oral Health Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
J Prosthet Dent. 2010 Sep;104(3):191-8. doi: 10.1016/S0022-3913(10)60120-5.
Composite mandibular resection resulting in mandibular discontinuity can alter jaw motion, occlusal forces, and mastication, whether or not the jaw is reconstructed. The biomechanical events associated with these changes are difficult to assess clinically and, therefore, are not well documented or researched.
The purpose of this study was to model movements of a mandible with a discontinuity defect, and to compare them to movements of a mandible with its continuity restored by alloplastic reconstruction.
Computational models were created with a novel simulation platform. The variables designed into the models included gravity, external forces, and jaw muscle activity. Each jaw was observed at rest, when opened by external force or by muscle drive, and during the generation of unilateral occlusal force on the nonoperated side. Scarring was simulated with springlike forces. Outputs included individual muscle forces and torques, as well as mandibular incisor and condylar motions.
Both models displayed plausible resting postures, and jaw opening with deviation toward the defect side when scarring was simulated. Opening caused by downward force on the incisors differed from that due to muscle activation. Jaw rotations during unilateral molar contact on the unaffected side were muscle specific and influenced by mandibular discontinuity.
Plausible jaw movements after hemimandibulectomy and/or alloplastic reconstruction could be predicted by dynamic modeling. The effect of soft tissue forces on jaw posture and movements varied with the condylar support available. In both models, different opening trajectories were produced by external force on the jaw and by jaw muscle activation. Mandibular rotation during unilateral molar contact depended on which muscles were activated, and the availability of bilateral condylar support.
下颌骨复合切除术导致下颌骨连续性中断会改变下颌运动、咬合力和咀嚼功能，无论是否重建下颌骨。与这些变化相关的生物力学事件很难在临床上进行评估，因此，这些事件并没有得到很好的记录或研究。
本研究的目的是模拟具有不连续缺陷的下颌骨的运动，并将其与通过同种异体重建恢复连续性的下颌骨的运动进行比较。
使用新颖的模拟平台创建了计算模型。模型中设计的变量包括重力、外部力和颌骨肌肉活动。观察每个下颌在休息时、由外部力或肌肉驱动打开时以及在非手术侧产生单侧咬合力时的运动。瘢痕用弹性力模拟。输出包括单个肌肉力和扭矩，以及下颌切牙和髁突的运动。
两个模型都显示出合理的休息姿势，当模拟瘢痕时，下颌开口会偏向缺陷侧。由切牙向下的力引起的开口与由肌肉激活引起的开口不同。在未受影响侧进行单侧磨牙接触时，下颌的旋转是肌肉特异性的，并受下颌不连续性的影响。
通过动态建模可以预测半下颌切除术后和/或同种异体重建后的下颌运动。软组织力对下颌姿势和运动的影响因髁突的支撑情况而异。在两个模型中，外部力对下颌的作用和下颌肌肉的激活都会产生不同的开口轨迹。单侧磨牙接触时的下颌旋转取决于激活的肌肉以及双侧髁突的支撑情况。
