Abstract: Disclosed is an interdental tooth cleaning appliance for use in cleaning a space formed between adjacent teeth. In order to clean more effectively as compared with a known appliance, the cross-sectional shape of the bristles as seen in a plane perpendicular to the longitudinal axis of the brush is such as to provide three circumferentially spaced groups of bristles which are longer than the remaining bristles. The interdental tooth cleaning appliance of this invention is provided with a guide which makes it a more convenient one. It also has a device for injecting a liquid medicine.

Abstract: A low-carat corrosion-resistant gold alloy which is not blacked in its skin surface color upon being cast is provided. The alloy is used as cast alloy for reparation of tooth crowns, as general decorative articles, or as contact alloy used in electrical apparatus. The alloy is composed essentially of gold, palladium and silver, with addition thereto of indium in place of copper contained in the conventional alloys, and necessary amounts of zinc or tin as deoxidant. Copper contents have been desired in view of improving the castability and mechanical strength of the alloy but the skin surface of the cast alloy may thereby be blacked to detract from aesthetic effects thus making it necessary to wash off the blacked oxide film by use of strong acid washing agents. The indium added in place of copper affords necessary mechanical properties to the alloy while providing aesthetically desirable silver to gray skin color and making the washing with strong acids unnecessary.