Chen Weng-Pin, Lee Bor-Shiunn, Chiang Yu-Chih, Lan Wan-Hong, Lin Chun-Pin
Department of Biomedical Engineering, Chung Yuan Christian University, Chungli, Taiwan.
J Formos Med Assoc. 2005 Nov;104(11):830-8.
Previous studies investigating the effects of core or post on the fracture strength of teeth often omitted the periodontal ligament (PDL) because its physical properties are difficult to reliably quantify. This study investigated the effects of various PDL elastic moduli on the stress distribution around a central incisor and surrounding alveolar bone using 3-dimensional finite element stress analyses.
Four 3-dimensional finite element models of an upper central incisor and the dento-alveolar complex were established. Five models were constructed, including: no PDL, as well as a PDL with elastic moduli of 6.9 MPa, 68.9 MPa, and 1750 MPa. Two loading conditions were simulated, one with protrusive force and one with intrusive force. Protrusive loading was generated using a point force of 200 N at 45 degrees inclination to the longitudinal axis of the incisor applied on the lingual side. Intrusive loading was generated using a point force of 200 N applied perpendicular to the incisal edge.
The absence of a PDL had detrimental effects on the surrounding bone, because the applied stress remained concentrated at the bone crest and cervical third of the root. A PDL with a lower elastic modulus, on the other hand, helped to alleviate the magnitude of stress throughout the surrounding bone and the bone crest, in particular, by distributing the stress deeper towards the apical region. The stress distribution at the crown was unaffected by variations in the PDL elastic modulus.
PDL with a lower elastic modulus can help protect the alveolar bone crest from stress concentration.
以往研究牙齿折断强度时，常忽略牙周膜（PDL），因其物理特性难以可靠量化。本研究采用三维有限元应力分析，探究不同牙周膜弹性模量对中切牙及周围牙槽骨应力分布的影响。
建立了上颌中切牙及牙-牙槽复合体的四个三维有限元模型。构建了五个模型，包括：无牙周膜模型，以及弹性模量分别为6.9 MPa、68.9 MPa和1750 MPa的牙周膜模型。模拟了两种加载条件，一种是前伸力加载，另一种是垂直向力加载。前伸加载时，在舌侧施加一个与中切牙纵轴呈45度倾斜的200 N点力。垂直向加载时，在切缘垂直施加一个200 N点力。
无牙周膜对周围骨有不利影响，因为施加的应力集中在牙槽嵴顶和牙根颈1/3处。另一方面，弹性模量较低的牙周膜有助于减轻周围骨及牙槽嵴顶的应力大小，特别是通过将应力更深入地分布到根尖区域。牙周膜弹性模量的变化对牙冠处的应力分布无影响。
弹性模量较低的牙周膜有助于保护牙槽嵴顶免受应力集中。
