Methods of imparting the Functional Gradient to Some Dental Adhesives

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Among dental adhesives and cements, glass-ionomer cements consist of polyacids and solid particles. It has been shown possible to impart them a functional gradinet by generating a compositional gradient in one direction. In the current study, a simplified system consisting of polyacrylic acid (PAA) and glass particles was employed to represent a glass-ionomer cement system. The sedimentation properties of glass particles with various size, as the model fillers, were investigated under the gravity by observing the change in the turbidity. Sedimentation velocity was mainly dependent on (1) the expansion of co-existing polymers in the media, (2) the concentration of polymers, (3) the size of the dispersed particles. Further invesigation of the mixing effects of the flliers of different type, the effects of ionic strength or viscosity, etc.will help to develope this study. Through these studies, it is highly expected to reveal how the sedimentation is formulated, which describes the compositonal gradient or a composition at all arbitrary point, as a function of time, filler size and so on. Another possible way of generating a compositoinal gradient, an electrophoresis of charged components concerned in the adhesive systems, is also to be examined.Subsidary findings are as follows.1) Fluorescent distance probe was effectively used to find out the conformation of PAA.2) Differential scanning calorimetry was useful in the investigation of adhesive-tooth protein interaction.3) Full-automatic titration system has been developed, which has potintial applicability to many aspects.Those extra findings will also help developing the study of dental materials.