Murakami Kazuhiro, Sugiura Tsutomu, Yamamoto Kazuhiko, Kawakami Masayoshi, Kang Yu-Bong, Tsutsumi Sadami, Kirita Tadaaki
Department of Oral and Maxillofacial Surgery, Nara Medical University, Kashihara City, Nara, Japan.
J Oral Maxillofac Surg. 2011 Jun;69(6):1798-806. doi: 10.1016/j.joms.2010.07.052. Epub 2011 Jan 26.
This study investigated the biomechanical behavior of the mandible after marginal resection by tensile test in a human cadaveric mandible and finite element (FE) analysis.
Human cadaveric mandibular models after marginal resection were prepared with residual heights of 5, 10, and 15 mm. The strength in each of these mandibular models was examined by tensile testing. In addition, FE models of the mandible after marginal resection were prepared with residual heights of 5, 7.5, 10, 12.5, and 15 mm. Distribution and magnitude of von Mises stress were analyzed by applying bite forces of 151 N as a point load on the incisal region and 355.2 and 478.1 N on the premolar and molar regions on the nonresected and resected sides, respectively. At the molar region of the resected side, bite forces of 368.5 N and 286.9 N (80% and 60%, respectively, of 478.1 N) were also applied.
On tensile testing, all cadaveric mandibular models were broken at the posterior resection corner. The tensile force was significantly larger in the model with a residual height of 15 mm compared with that of those with a 5- or 10-mm residual height. On FE analysis, von Mises stress was concentrated at the resection corner. The region of maximal von Mises stress concentration in FE models was consistent with that showing destruction on tensile testing. The relationship between the residual height and von Mises stress in the resection area was linear in models of the incisal, premolar, and molar loading on the nonresected side and quadratic in models of the premolar and molar loading on the resected side. The maximal von Mises stress in the resection area was highest during molar loading on the resected side under the present loading condition and exceeded the threshold for the development of pathologic fracture in the model with a residual height of around 10 mm or less. However, the maximal von Mises stress decreased in parallel with the reduction of bite force in the molar region of the resected side.
The residual height and bite force are critical factors for the prevention of pathologic fracture of the mandible after marginal resection. Currently, a residual height of more than 10 mm and reduction of bite force are recommended to reduce the risk of fracture.
本研究通过对人体尸体下颌骨进行拉伸试验及有限元（FE）分析，探究边缘切除术后下颌骨的生物力学行为。
制备边缘切除术后的人体尸体下颌骨模型，剩余高度分别为5mm、10mm和15mm。通过拉伸试验检测这些下颌骨模型各自的强度。此外，制备边缘切除术后下颌骨的FE模型，剩余高度分别为5mm、7.5mm、10mm、12.5mm和15mm。通过分别在未切除侧的切牙区施加151N的点载荷、前磨牙区施加355.2N以及磨牙区施加478.1N咬合力，在切除侧的磨牙区分别施加368.5N和286.9N（分别为478.1N的80%和60%）咬合力，分析冯·米塞斯应力的分布和大小。
在拉伸试验中，所有尸体下颌骨模型均在切除后角处断裂。与剩余高度为5mm或10mm的模型相比，剩余高度为15mm的模型的拉伸力显著更大。在FE分析中，冯·米塞斯应力集中在切除角处。FE模型中冯·米塞斯应力最大集中区域与拉伸试验中显示破坏的区域一致。在未切除侧切牙、前磨牙和磨牙加载模型中，切除区域的剩余高度与冯·米塞斯应力之间呈线性关系，而在切除侧前磨牙和磨牙加载模型中呈二次关系。在当前加载条件下，切除侧磨牙加载时切除区域的最大冯·米塞斯应力最高，在剩余高度约为10mm或更小的模型中超过了病理性骨折发生的阈值。然而，切除侧磨牙区咬合力降低时，最大冯·米塞斯应力也随之降低。
剩余高度和咬合力是预防边缘切除术后下颌骨病理性骨折的关键因素。目前，建议剩余高度超过10mm并降低咬合力以降低骨折风险。
