THERMALLY INDUCED CHANGES IN DENTAL PORCELAIN EXPANSION

尽管有科学证据的份量，以及来自 国际健康咨询组织指出，牙科汞释放 汞齐不会对普通人群的健康构成威胁(Mackert和 Berglund，1997 a，b)，一些国家已经将 对牙科汞齐使用的限制。因此，有必要 完善生物相容的牙科材料，如陶瓷，以便它们 在进一步限制的情况下可用作汞齐替代品， 或者是彻底禁止使用牙科汞合金。这项研究中提出的 应用程序旨在开发更强大、更少磨损性的 用于烤瓷的热稳定性更高的牙科陶瓷 金属修复体(PFM)和全瓷修复体。陶瓷有许多可取之处 使它们对牙齿修复有用的特性-半透明， 化学耐久性和生物相容性。然而，有两个主要问题 用于修复因疾病而丧失的牙齿结构 或创伤：他们脆性骨折的潜力和他们的能力 造成相对牙齿结构的磨粒磨损(Rosenblum和Schulman， 1997年)。当瓷器与金属或高强度陶瓷熔合时 核心作为一种手段，以消除它们在实力领域的缺点， 第三个问题的可能性被引入-瓷器过热 膨胀不稳定性和由此产生的热不相容 瓷器和金属或陶瓷芯。五个具体目标是 建议：1.制定各种烤瓷金属的烧成时间表 将热引起的白榴石含量变化降至最低的系统 导致热膨胀变化的；2.继续修改 瓷器，使其更能抵抗热膨胀变化； 3.开发白榴石增强可加工陶瓷，该陶瓷可 在CEREC 2中加工后通过热处理进行强化 CAD/CIM机器；4.用白榴石研制实验瓷器 小于4um的颗粒尺寸作为最小化微裂纹的手段， 提高牙釉质的强度，减少对牙釉质的磨损 评估实验中铝、硅和其他元素的释放情况 在拟开发的陶瓷研究中，比较这些发布 与现有陶瓷的价值相比，并将它们与饮食和 这些元素的其他摄取来源。新的陶瓷配方和 将研究成核剂的组合，以减少 白榴石颗粒大小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.