THERMALLY INDUCED CHANGES IN DENTAL PORCELAIN EXPANSION

尽管科学证据的分量，以及来自 国际卫生咨询小组，从牙科释放的汞 汞合金不会对一般人群构成健康威胁（Mackert和 Berglund，1997 a，B），一些国家已经将 限制使用牙科汞合金。 因此，有必要 以完善生物相容性牙科材料，如陶瓷， 在进一步限制的情况下可以作为汞合金替代品， 或彻底禁止牙科汞合金。 这项研究提出， 本申请旨在开发更强、更少磨损和 更热稳定的牙科陶瓷， 金属（PFM）和全陶瓷涂层。陶瓷有许多可取的 使它们可用于牙齿清洁的性能-透明性， 化学耐久性和生物相容性。 然而，两个主要问题 在它们被用作因疾病而丧失的牙齿结构的替代物时出现 或创伤：他们的脆性骨折的潜力和他们的能力， 导致相对的齿结构的磨损（Rosenblum和Schulman， 1997年）。 当瓷器与金属或高强度陶瓷融合时 核心作为一种手段，消除他们的缺点，在该地区的力量， 引入了第三个潜在问题-瓷热 膨胀不稳定性和由此产生的热不相容性 陶瓷和金属或陶瓷芯。 五个具体目标是 建议：1.制定各种金属陶瓷的烧成制度 使白榴石含量的热致变化最小化的系统 导致热膨胀变化; 2.继续修改 陶瓷，使它们更能抵抗热膨胀变化; 3.开发一种白榴石增强的可加工陶瓷， 在CEREC 2中进行机加工后通过热处理进行强化 CAD/CIM机; 4.用白榴石研制实验瓷 小于4 μ m的粒度作为使微裂纹最小化的手段， 增加强度，并减少相对釉质的磨损;以及5.到 评估Al，Si和其他元素从实验中的释放 拟在陶瓷开发中进行研究，比较这些释放 现有陶瓷的价值，并将其与饮食和 这些元素的其他摄入来源。新的陶瓷配方和 将研究成核剂的组合以减少 白榴石粒度作为影响这些物理性质的手段 改进.

Despite the weight of scientific evidence, as well as assurances from international health advisory groups, that mercury release from dental amalgam poses no health threat to the general population (Mackert and Berglund, 1997a, b), a number of countries have already placed restrictions on the use of dental amalgam. There is, therefore, a need to perfect biocompatible dental materials such as ceramics so that they can serve as amalgam substitutes in the event of further restriction, or an outright ban, on dental amalgam. The research proposed in this application is directed toward developing stronger, less abrasive, and more thermally stable dental ceramics for use in porcelain-fused-to- metal (PFM) and all-ceramic restorations. Ceramics have many desirable properties that make them useful for dental restorations - translucency, chemical durability, and biocompatibility. However, two major problems arise in their use as replacements for tooth structure lost to disease or trauma: their potential for brittle fracture and their capacity to cause abrasive wear of opposing tooth structure (Rosenblum and Schulman, 1997). When porcelains are fused to metal or to a high-strength ceramic core as a means of obviating their shortcomings in the area of strength, the potential for a third problem is introduced - porcelain thermal expansion instability and the resulting thermal incompatibility between the porcelain and the metal or ceramic core. Five specific aims are proposed: 1. To develop firing schedules for various porcelain metal systems to minimize the thermally induced changes in leucite content that lead to thermal expansion changes; 2. To continue modification of porcelains to render them more resistant to thermal expansion changes; 3. To develop a leucite-reinforced machinable ceramic that can be strengthened via heat treatment following machining in the CEREC 2 CAD/CIM machine; 4. To develop experimental porcelain with a leucite particle size of less than 4 um as a means of minimizing microcracking, increasing strength, and reducing wear of opposing enamel; and 5. To evaluate the release of Al, Si, and other elements from the experimental ceramics to be developed in the proposed research, compare these release value to those of existing ceramics, and relate them to dietary and other sources of intake of these elements. New ceramic formulations and combinations of nucleating agents will be investigated to reduce the leucite particle size as means to effect these physical properties improvements.