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Abstract:The purpose of this study is to compare the tensile strength of Ni-Cr base metal presoldered joints, soldered by focused energy of infra-red (Infra-red soldering) with torch soldering technique.The results indicate the following.1. The tensile strength of presoldered joints, soldered by Infra-red soldering isstatistically stronger than presoldered joints, soldered by torch soldering (a =0.01).2. In case of torch soldering joints, porosities appeared to have a greater tendency than Infra-red soldering joints. Torch soldering joints porosities are seven times as many as the other.3. Correct tensile strength (Maximum Load: Kg/Sectional area of specimen-Porosityarea: mm2) of presoldered joints, soldered by both method are similar.It means that, tensile strength is correlate closely with certainly soldering area.

Our department has been researching the influences of changes in particle size distribution on the physical properties of luting agents.It is said that luting agents are largely affected by contact with water. In the present study, changes in the physical properties after contact with water at the time of cementation were determined in several types of glass-ionomer cement for Luting (G cement), which differed in particle size distribution, by using an ivory or agar jig. The physical properties of G cement were also examined after pretreatment of the abutment tooth with a surfacetreatment agent and a temporary cement inside the ivory jig.As a result, the greater the content of fine particles was, the greater the compressive strenght, tensile strength and scratch hardness of G cement tended to be. G cement containing high proportions of fine particles was not likely to be affected by water. Pretreatment suchas temporary cementation or surface-treatment prior to cementation for crown or bridge formation was found to be effective for preventing deterioration of the physical properties of G cement.

For improvement of film thickness of final cementation, 2 brands (Shofu HY-BOND GLASS -IONOMER CX and GC Fuji-I) of Glass Ionomer Cement were milled and the experimental fine particle powder was produced. Ohmae et al. reported the retention, total film thickness, and physical properties in a previous study. In this study, the setting characteristics of these experimental cements, specific surface area