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首页> 外文期刊>The Journal of Prosthetic Dentistry >Corono-radicular reconstruction of pulpless teeth: A mechanical study using finite element analysis.
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Corono-radicular reconstruction of pulpless teeth: A mechanical study using finite element analysis.

机译：无牙髓牙冠冠放射重建：使用有限元分析的力学研究。

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Statement of Problem. Following endodontic therapy, teeth need to be protected, particularly in the cervical region, where the majority of fractures occur. The likelihood of a fracture depends on the condition of the crown and the type of reconstruction performed. Purpose. This simulation study was designed to compare the effect of different corono-radicular reconstruction methods on stress transmission to dental tissues. Material and Methods. The study software performed stress analysis of complex structures by finite element analysis. Seven 3-dimensional models were created, each representing a tooth embedded in a bony medium. The following parameters affecting corono-radicular restoration were studied: 2 levels of coronal destruction, core materials, post materials when present, and absence of post. The 2 levels of coronal tissue loss were (1) total tissue loss of the coronal dentin and (2) partial tissue loss of the coronal dentin with 2-mm surviving dentin walls. Teeth with 2 different levels of tissue loss (first study parameter) were reconstructed by 4 different techniques: nickel chromium (NiCr) cast post and core, NiCr post and composite core combination, carbon fiber post and composite core combination, and composite restoration without post. A NiCr crown covered each of the models and received a 30 degrees oblique occlusal load at a constant intensity of 100 N. The software computed the stresses (local tensile stress inducing cracks and compressive stress) for each of the models, comparing maximum intensity observed, localization, and concentration. Results. Whatever the type of stress (tensile or compressive), the greatest stress was observed in the cervical region, regardless of the model. Only tensile stresses potentially responsible for fractures were compared. Cervical tensile stresses exceeded 230 Pa in the absence of a ferrule and were less than 140 Pa when a ferrule was present. In the absence of a ferrule, the NiCr composite/post combination generated greater cervical stress (254 Pa) than the cast post and core (235 Pa). Results with a ferrule showed 92 Pa for the NiCr composite/post combination and 90.5 Pa for the cast post and core. In the presence of a ferrule, the tensile stress intensities generated by the composite restoration with no root canal post (139 Pa) were 51% greater than those generated by the NiCr/composite combination and approximately 26% greater than those generated by the composite/carbon combination. Conclusion. Within the limitations of this study, it was confirmed that all simulated reconstructed teeth were more subject to stress in the cervical region. The absence of a cervical ferrule was found to be a determining negative factor, giving rise to considerably higher stress levels. When no ferrule was present, the NiCr post/composite combination generated greater cervical stress than cast post and cores. Nevertheless, the peripheral ferrule seemed to cancel the mechanical effect of the reconstruction material on the intensity of the stresses. With a ferrule, the choice of reconstruction material had no impact on the level of cervical stress. The root canal post, the purpose of which is to protect the cervical region, was also shown to be beneficial even with sufficient residual coronal dentin. In the presence of a root canal post, cervical stress levels were lower than when no root canal post was present. Moreover, the higher the elasticity modulus, the lower the stress levels.
机译：问题陈述。牙髓治疗后，需要保护牙齿，尤其是在大多数骨折发生的宫颈区域。骨折的可能性取决于牙冠的状况和所进行重建的类型。目的。这项模拟研究旨在比较不同冠状放射重建方法对应力传递至牙齿组织的影响。材料与方法。该研究软件通过有限元分析对复杂结构进行了应力分析。创建了七个3维模型，每个模型都代表一个嵌入骨质介质中的牙齿。研究了以下影响冠状放射修复的参数：2级冠状破坏，核心物质，存在的柱状材料和不存在柱状材料。冠状组织损失的2个水平是（1）冠状牙本质的总组织损失和（2）存活2mm的牙本质壁的冠状牙本质的部分组织损失。通过4种不同的技术重建具有2种不同组织损失水平的牙齿（第一个研究参数）：镍铬（NiCr）铸造桩和核，NiCr桩和复合核的组合，碳纤维桩和复合核的组合以及无桩的复合修复。 NiCr胎冠覆盖每个模型，并以100 N的恒定强度承受30度的斜向咬合载荷。软件计算每个模型的应力（局部拉应力引起的裂纹和压应力），比较观察到的最大强度，本地化和集中化。结果。无论哪种类型的应力（拉应力或压应力），无论型号如何，在宫颈区域都可观察到最大的应力。仅比较了可能导致断裂的拉伸应力。在没有套圈的情况下，宫颈拉伸应力超过230 Pa，在有套圈的情况下小于140 Pa。在没有套圈的情况下，NiCr复合材料/柱组合产生的颈应力（254 Pa）要比铸柱和芯的组合（235 Pa）大。带有密封垫圈的结果显示，NiCr复合材料/立柱组合为92 Pa，铸造立柱和型芯为90.5 Pa。在有套圈的情况下，无根管桩的复合修复体产生的拉伸应力强度（139 Pa）比NiCr /复合材料组合产生的拉伸应力强度高51％，比复合材料/复合材料产生的拉伸应力强度高约26％。碳组合。结论。在本研究的范围内，已证实所有模拟的重建牙齿在宫颈区域均更容易受到压力。发现不存在子宫颈套圈是决定性的不利因素，从而导致相当高的压力水平。当不存在套圈时，NiCr柱/复合材料组合物产生的宫颈应力要大于铸造柱和芯。尽管如此，外围套圈似乎抵消了重建材料对应力强度的机械作用。使用套圈时，重建材料的选择不会对宫颈压力产生影响。根管柱的目的是保护颈椎区域，即使有足够的残留冠状牙本质也被证明是有益的。在有根管桩的情况下，颈椎压力水平低于没有根管桩的情况。此外，弹性模量越高，应力水平越低。

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