Kikuchi M
Department of Dental Materials Science, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan.
Aichi Gakuin Daigaku Shigakkai Shi. 1990 Dec;28(4):1287-302.
The rheological properties of elastomeric impression materials are important because they are major determinants in the handling characteristics and adaptation to the soft and hard tissues of the mouth. Of particular interest is the rheology of the elastomeric impression materials as supplied by the manufacture since this strongly influences the ease with which the two pastes can be mixed and placed. Additionally, the flow characteristics of the mixed impression materials are also important as these will have an important bearing on the accuracy and reproduction of surface detail which are influenced by the working time. Generally, rheological properties can be defined as the study of the flow characteristics of viscos materials such as elastomeric impression materials. In the context of impression materials used in dentistry the variation of these flow characteristics over short time intervals is extremely important in the making of clinically acceptable impressions. The purpose of these studies were to measure a variety of rheological characteristic for the unmixed elastomeric impression materials and to relate this information to clinical dental procedures. The elastomeric impression materials used in this study were polysulfides, condensation cured silicone, addition cured silicone rubbers in common clinical use and specimens of adding increasing increments of filler (SiO2, TiO2 or PbO2) to a main constituent part (Thiokol LP2, Chloridparaffin, Silicone or Vinylsilicone) of each impression paste. The viscosity of these materials were measured by using the Ishida-Giken cone and plate high shear rheometer. The changes in shear stress with time were recorded for a shear rate of 5 s-1 at 23 degrees C. The relation of shear rate to shear stress were accomplished with a range of shear rates from 0 s-1 to 20 s-1. The viscosity behavior which were the flow characteristic, apparent viscosity, the yield value and the areas of hysterisis loop, were determined from both the shear stress-time and the shear stress-shear rate curves. The results of this study of elastomer impression material pastes have shown that: 1. All impression pastes exhibited non-Newtonian viscosity characteristic, apparent viscosity decreasing with increasing shear rate. 2. Surflex F base pastes (polysulfide rubber), Flexicone injection type base paste (condensation-cured silicone rubber) and Exaflex injection type base paste (addition cured silicone rubber) were pseudoplastic behavior, and other impression pastes were virtually thixotropic behavior. 3. All impression paste had yield value, especially Surflex F accelerator pastes which had a markedly higher yield value.(ABSTRACT TRUNCATED AT 400 WORDS)
弹性印模材料的流变特性很重要，因为它们是决定操作特性以及与口腔软硬组织贴合度的主要因素。特别值得关注的是制造商提供的弹性印模材料的流变学，因为这会极大地影响两种糊剂混合和放置的难易程度。此外，混合后印模材料的流动特性也很重要，因为它们将对表面细节的准确性和再现性产生重要影响，而这又受操作时间的影响。一般来说，流变特性可定义为对诸如弹性印模材料等粘性材料流动特性的研究。在牙科用印模材料的背景下，这些流动特性在短时间间隔内的变化对于制作临床上可接受的印模极为重要。这些研究的目的是测量未混合弹性印模材料的各种流变特性，并将这些信息与临床牙科操作联系起来。本研究中使用的弹性印模材料是多硫化物、缩合固化硅橡胶、常用的加成型固化硅橡胶，以及在每种印模糊剂的主要成分（聚硫橡胶LP2、氯化石蜡、硅橡胶或乙烯基硅橡胶）中添加递增增量填料（二氧化硅、二氧化钛或二氧化铅）的样本。这些材料的粘度通过使用石田技研锥板高剪切流变仪进行测量。在23摄氏度下，以5 s-1的剪切速率记录剪切应力随时间的变化。在0 s-1至20 s-1的一系列剪切速率下完成剪切速率与剪切应力的关系测定。从剪切应力-时间曲线和剪切应力-剪切速率曲线确定作为流动特性的粘度行为、表观粘度、屈服值和滞后回线面积。对弹性体印模材料糊剂的这项研究结果表明：1. 所有印模糊剂均表现出非牛顿粘度特性，表观粘度随剪切速率增加而降低。2. Surflex F基糊剂（多硫化橡胶）、Flexicone注射型基糊剂（缩合固化硅橡胶）和Exaflex注射型基糊剂（加成型固化硅橡胶）表现出假塑性行为，其他印模糊剂实际上表现出触变性行为。3. 所有印模糊剂都有屈服值，尤其是Surflex F促进剂糊剂的屈服值明显更高。（摘要截选至400字）
