間接法歯型の膨縮変形に関する綜合的研究

抄録

In making well fitting inlays and crowns, it is necessary to know the dimensional and formal changes of the dies compared with the original preparation, and find methods to reduce such errors. By measuring only the free changes of impression and die materials individually, as hitherto done, the real accuracy of the dies cannot be known. In our studies, the distances between outside walls or inside of the specimen dies were measured. For this measurement the author first originated a set of specially constructed gauges. Measurement of dimensional changes of small specimens of the same size as the practical dies in clinic, with the precision to 0.01%, became possible for the first time by using these gauges together with comparator microscope.
The author originated another set of gauges for use in complementary experiments, by which the distances of the inside walls of specimen dies could be measured comparatively with that of the outside walls under similar conditions. The real dimensional changes are computed by averaging both figures.
Important informations were obtained by using these two kinds of gauges, which will serve the rational use of indirect technique and the improvement of dental materials.
In these studies, alginate and compound were used as impression materials. Hydrocals (Plastone and Duroc), Phosphosilicate cement, Zinc-phosphate cement, Cu-amalgam and Ag-Sn amalgam were used as die materials. The dimensional changes of various dies made of these materials were compared with the original models. Various clinical conditions were introduced into these tests to determine their effects on dimensional and formal changes. The influences of time and separating mediums upon the completed dies were also studied experimentally.