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Fatigue and fatigue crack growth processes in hard tissues: The importance of age and surface integrity.

机译：硬组织中的疲劳和疲劳裂纹增长过程：年龄和表面完整性的重要性。

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摘要

With the progressive increase in partially and fully dentate seniors, fracture has become an increasingly common form of restored tooth failure. Dentin undergoes progressive changes in microstructure with patient age, and studies are now suggesting that there is a reduction in fatigue strength and fatigue crack growth resistance of this tissue. This dissertation explores aging of dentin, the influence of flaws that are introduced during restorative processes on the fatigue properties of dentin, and proposes models for characterizing the damage initiation and growth process during fatigue of dentin.;Results from this investigation show that the fatigue crack growth properties (Paris Law parameters (C, m) andDeltaKth) of human dentin undergo the most significant changes at a patient age of 42 years. Based on the fatigue crack growth responses, three age groups were established including young (age≤33), aged (34≤age ≤49) and old (50≤age) patients for further analysis. There were significant differences in the initiation and growth behavior between the tissues of patients from the three age groups. With regards to the influence of restorative processes, there was no influence on the quasi-static responses of dentin. However, the endurance limit of dentin treated with the dental burs (28 MPa) and abrasive air jet (35 MPa) were approximately 36% and 20% lower than that of the control (44 MPa), respectively. Both cutting processes caused a significant reduction (p≤0.0001) in fatigue strength.;An accumulative damage model was developed to characterize fatigue of the control and bur treated dentin as well as provide a model for fatigue life prediction. The damage models were derived as a function of number of loading cycles (N), and ratio of applied stress to ultimate strength (r). The developed models provide estimations for the initial state of damage, the state of damage during the life, as well as the damage accumulation rate for cyclic loading of dentin. Using the experimental findings, a Damage Effect Model (DEM) was also developed to describe the influence of flaws introduced by bur treatment on fatigue of dentin. The DEM showed that the damage caused by bur treatment is uniform and independent of tubule orientation. Using the developed DEM for dentin with 0° tubule orientation, material constants of bur treated dentin with 90° orientation were estimated and used in predicting fatigue for controlled experimental conditions involving a notched fatigue approach.;Overall, the results of this study provide fundamental knowledge concerning the influence of aging and cutting processes on the fatigue properties of dentin. These findings are of substantial importance to the field of restorative dentistry, and potentially establish the need for treating senior patients with an approach that is unique from that of younger patients. The damage models developed in this investigation are the first that have been developed for hard tissues, and provide a foundation for future research aimed at modeling fatigue processes in hard tissues including bone and dentin.
机译：随着部分和完全牙齿的老年人的逐渐增加，骨折已成为恢复牙齿衰竭的越来越普遍的形式。随着患者年龄的增长，牙本质的微观结构会逐渐发生变化，现在的研究表明该组织的疲劳强度和抗疲劳裂纹扩展性降低。本文探讨了牙本质的老化，修复过程中引入的缺陷对牙本质疲劳特性的影响，并提出了表征牙本质疲劳过程中损伤引发和生长过程的模型。人类牙本质的生长特性（巴黎法参数（C，m）和DeltaKth）在42岁的患者年龄发生最显着的变化。基于疲劳裂纹扩展响应，确定了三个年龄组，包括年轻（年龄≤33），年龄（34≤年龄≤49）和老年（50≤年龄）患者，以进行进一步分析。三个年龄组的患者组织在起始和生长行为上存在显着差异。关于恢复过程的影响，对牙本质的准静态反应没有影响。但是，用牙钻（28 MPa）和空气喷射喷头（35 MPa）处理的牙本质的耐力极限分别比对照（44 MPa）低36％和20％。两种切削过程均导致疲劳强度显着降低（p≤0.0001）。；建立了累积损伤模型以表征对照和经过bur处理的牙本质的疲劳，并提供了疲劳寿命预测模型。得出的损伤模型是载荷循环次数（N）和施加应力与极限强度之比（r）的函数。所开发的模型可以估算出损伤的初始状态，生命中的损伤状态，以及牙本质循环负荷的损伤累积率。利用实验结果，还开发了损伤效应模型（DEM）来描述bur处理引入的缺陷对牙本质疲劳的影响。 DEM显示，由bur处理引起的损害是均匀的，并且与肾小管的方向无关。使用开发的DEM用于0°肾小管取向的牙本质，估算经过bur处理的90°取向牙本质的材料常数，并将其用于预测在有缺口疲劳方法的受控实验条件下的疲劳度;总体而言，本研究的结果提供了基础知识关于老化和切削工艺对牙本质疲劳特性的影响。这些发现对修复牙科领域非常重要，并且有可能建立对年轻患者的独特治疗方法，以治疗老年患者。在这项研究中开发的损伤模型是针对硬组织开发的第一个模型，它为旨在对包括骨骼和牙本质在内的硬组织中的疲劳过程进行建模的未来研究提供了基础。

著录项

  • 作者

    Majd, Hessam.;

  • 作者单位

    University of Maryland, Baltimore County.;

  • 授予单位 University of Maryland, Baltimore County.;
  • 学科 Engineering Mechanical.;Health Sciences Dentistry.;Biophysics Biomechanics.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 258 p.
  • 总页数 258
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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