Mesquita Renata V, Geis-Gerstorfer Jürgen
Department of Prosthodontics, Section Medical Materials and Technology, University of Tuebingen, Osianderstr. 2-8, 72076 Tuebingen, Germany.
Dent Mater. 2008 May;24(5):623-32. doi: 10.1016/j.dental.2007.06.025. Epub 2007 Sep 10.
The first aim of this study was to determine the visco-elastic properties of two direct (DiamondLite and Grandio) and two indirect (Artglass and Vita Zeta LC) dental composites over a wide range of temperatures, in order to avoid choosing a composite that would undergo sudden changes in its mechanical properties during service.
Within this objective the composites were tested immediately after fabrication or after storage at 37 degrees C, either in air or distilled water for 1 day, 7 or 90 days. During dynamic testing, the elastic modulus (E'), viscous modulus (E'') and loss tangent (tandelta) were determined using a dynamic mechanical analyzer (DMA) over a temperature range from 0 to 200 degrees C, at an approximate masticatory frequency of 1 Hz.
Based on their high glass transition temperatures (Tg) and on the fact that materials are basically equilibrated at 37 degrees C in the mouth and are not thermal conductors, temperature changes from 37 degrees C are expected to be small and should lead to only modest changes in both moduli. However, composites might improve their initial degree of conversion when exposed to normal mouth temperature and higher temperatures due to the ingestion of hot food and beverages. This event can have positive and negative effects on the restoration, such as greater rigidity and additional micro-leakage, respectively.
According to these results it could be said that monitoring the visco-elastic properties of dental composites under conditions that simulate the oral environment seems to be a useful tool to predict their clinical performance as restorative materials.
本研究的首要目的是测定两种直接法（DiamondLite和Grandio）和两种间接法（Artglass和Vita Zeta LC）牙科复合材料在较宽温度范围内的粘弹性特性，以避免选用在使用过程中机械性能会发生突然变化的复合材料。
在此目标下，复合材料在制备后或在37℃下于空气或蒸馏水中储存1天、7天或90天后立即进行测试。在动态测试过程中，使用动态机械分析仪（DMA）在0至200℃的温度范围内，以约1Hz的近似咀嚼频率测定弹性模量（E'）、粘性模量（E''）和损耗角正切（tanδ）。
基于它们较高的玻璃化转变温度（Tg）以及材料在口腔中基本在37℃达到平衡且不是热导体这一事实，预计从37℃开始的温度变化较小，并且只会导致两种模量出现适度变化。然而，由于摄入热的食物和饮料，复合材料在暴露于正常口腔温度和更高温度时可能会提高其初始转化率。这一情况可能对修复体产生积极和消极影响，例如分别导致更大的刚性和额外的微渗漏。
根据这些结果，可以说在模拟口腔环境的条件下监测牙科复合材料的粘弹性特性似乎是预测其作为修复材料临床性能的一种有用工具。
