- 學位論文
牙周膜韌帶厚度與牙柱釘尺寸對於根管治療後正中門齒及周圍齒槽骨應力之影響
Effects of Periodontal Ligament Thickness and Post Size on the Stress Distributions of Endodontically Treated Incisor and the Surrounding Alveolar Bone
摘要
牙周膜韌帶所伴隨的力學機制於牙科生物力學極其重要，而現今探討牙柱釘力學效應的研究大多忽略牙周膜韌帶的影響性，並未探討牙柱釘與牙周膜韌帶的交互作用。並且牙醫師選擇牙柱釘的尺寸僅以剩餘齒質為依據，並未考量到病患的牙周情況，例如牙周膜韌帶厚度等等。 因此，本研究以植入冠柱體之復形方式為基礎，建構上顎正中門齒及其牙周組織，並根據門齒幾何尺寸建構三種長度與三種直徑之牙柱釘，總共九種不同尺寸之牙柱釘模型。利用有限元素法給予適當的材料參數與邊界負載條件，首先比較線彈性與黏彈性牙周膜韌帶之差異，以確定黏彈性牙周膜韌帶的必要性。接著，比較玻璃纖維牙柱釘與金屬牙柱釘何者為修復牙齒之較佳選擇。最後，探討不同牙柱釘尺寸對應不同牙周膜韌帶厚度的情況下，牙齒與齒槽骨受負載之應力分佈情形，盼能給予臨床醫師在牙齒復形時選擇牙柱釘之參考。 有限元素分析結果證實了牙周膜韌帶的材料性質確實會影響牙齒的力學反應，黏彈性牙周膜韌帶能有效紓緩應力生成，以減少應力集中現象，並能夠接近實際牙齒咬合之力學行為。此外，本研究也證實了玻璃纖維牙柱釘較能均勻地分散應力於牙本質，故置入玻璃纖維牙柱釘之牙齒具有較佳的生物力學行為。於力量負載的情況下，越厚牙周膜韌帶能提供牙齒越大的移動度；於位移負載的情況下，越厚之牙周膜韌帶越具有緩衝能力，以有效減緩整體應力。牙柱釘尺寸主要影響牙柱釘及牙本質之應力，牙齒受位移負載下，長度越長且直徑越大之牙柱釘越能有效降低牙本質應力，而牙柱釘直徑對於牙本質的影響性大於長度。 基於本研究之有限元素結果與臨床觀點，我們可以建議臨床醫師在牙齒復形時，牙周膜韌帶較厚之青少年可選擇的牙柱釘尺寸範圍最為廣泛，牙周膜韌帶厚度居中之成年患者的選擇範圍次之，而牙周膜韌帶最薄之中老年患者的選擇最少，以有效降低牙本質上之應力。
並列摘要
The mechanical mechanism of a periodontal ligament (PDL) plays an extremely important role in dental biomechanics. However, the mechanical effect of the PDL on the post system was usually ignored in many studies. When dentists selecting dental post size, only the geometry of residual dentin of the tooth is considered and the PDL condition is often not taken into account. Therefore, the objective of this study was to evaluate the influence of PDL material properties on the stress distributions using finite element analysis (FEA) in pulpectomy. The maxillary incisor and the periodontal tissues were constructed. A total of 9 post models were included by changing the post diameter and length according to the incisor geometry. First, the linear elastic and viscoelastic materials of the PDL were compared to determine their effects on the stress distribution. Moreover, glass fiber and metal posts were compared to estimate the effect on the tooth and surrounding alveolar bone. Finally, the PDL thicknesses and post sizes were varied to assess the stress distributions of the incisor and the surrounding alveolar bone. The mechanical response of the tooth was affected by the material property setting of the PDL according to the FEA results. Not only the stress could be reduced but also the mechanical behavior of the tooth could be mimicked when the PDL was assigned with viscoelastic material properties. Moreover, the stress was uniformly transferred from the post to the dentin. There is a better biomechanical behavior using glass fiber than the metal post. The displacement of the tooth was increased and the stress was decreased when the thickness of the PDL was increased. Furthermore, the stress of the dentin was noticeably decreased when the dimensions (diameter and length) of the post was increased. However, the sensitivity of the post diameter was greater than the length for dentin stress distributions. Based on the FEA results of this study, it can provide guidelines for clinical dentists to choose suitable post sizes for younger and older patients.
參考文獻
延伸閱讀
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