Radu Michael, Marandici Mircea, Hottel Timothy L
Department of Restorative Dentistry, College of Dental Medicine, Nova Southeastern University, Fort Lauderdale, Florida, USA.
J Prosthet Dent. 2004 Feb;91(2):171-9. doi: 10.1016/j.prosdent.2003.10.011.
Clinicians often disagree about the acceptable position of the condyle in the articular fossa. Agreement as to what position the condyle-disk assembly assumes on the articular eminence while subjected to the forces of the elevator muscles of the mandible is important.
This simulation study investigated the position of the condyle-disk assembly on the articular eminence while subjected to the forces of the elevator muscles of the mandible during clenching.
Using the 2 conditions of static equilibrium, a vector analysis of a 2-dimensional model of the temporomandibular joint was developed. The dynamics of the condyle-disk assembly during muscle loading were analyzed. The vector sum of the masticatory muscle forces was determined by assuming that the maximum force developed by each contributing muscle was proportional with the physiologic cross section of the muscle. The effect of the resultant force vector of the combined muscle action applied to the condyle was analyzed for the orthogonal and acute angle situations.
When the vector sum was orthogonal on the eminence, the condyle was in stable equilibrium. The stable equilibrium was found in the anterior-superior position in the fossa. When the vector sum was at an acute angle to the eminence, the condyle was subject to a translation force that displaced it into the anterior-superior equilibrium position.
Within the limitation of this study, vector analysis suggested that the anterior-superior position of the condyle-disk assembly on the eminence was the most stable equilibrium position. All other tested positions of the condyle were less stable and maintained at the expense of other structures.
临床医生对于髁突在关节窝内的可接受位置常常存在分歧。对于在下颌升肌力量作用下，髁突-盘状结构在关节结节上处于何种位置达成共识很重要。
本模拟研究调查了在紧咬过程中，在下颌升肌力量作用下，髁突-盘状结构在关节结节上的位置。
利用静态平衡的两种情况，建立了颞下颌关节二维模型的矢量分析。分析了肌肉加载过程中髁突-盘状结构的动力学。咀嚼肌力的矢量和是通过假设每块参与肌肉产生的最大力量与肌肉的生理横截面积成正比来确定的。针对正交和锐角情况，分析了施加于髁突的联合肌肉作用合力矢量的影响。
当矢量和在关节结节上呈正交时，髁突处于稳定平衡。在关节窝的前上方位置发现了稳定平衡。当矢量和与关节结节呈锐角时，髁突受到一个平移力，使其移位到前上方平衡位置。
在本研究的局限性内，矢量分析表明，髁突-盘状结构在关节结节上的前上方位置是最稳定的平衡位置。髁突的所有其他测试位置稳定性较差，且是以牺牲其他结构为代价维持的。
