Modification of metallic materials for a white appearance without coating and plating

PurposeThe purpose of this study was to develop white-colored metals for metal injection moldings, and white-colored surface preparation for metals to satisfy the esthetic demands of patients.Materials and methodsTwo methods for white coloration of metals were developed for two kinds of metals. For white-colored silver metal, silver powder was baked at 700 °C for 15 min with or without the alumina plate. For white-colored surface preparation, titanium wire, orthodontic brackets and dental implants were baked at 1000 °C for 15 min. Two kinds of white-colored specimens were used for evaluation of coloration, mechanical strength and the components.ResultsTreated silver metal was visually white, and closed to the color of white porcelain panel evaluated by a colorimeter. From the results of load-deflection tests, the mechanical strength of white-colored silver metal was almost same as that of non-treated one. Surface prepared titanium objects were also visually white, and closed to the color of white porcelain, and thickness of white color layer was 10–50 μm. Load-deflection tests revealed that white-colored titanium metal was fragile compared to non-treated one. The component of white-colored silver metal was approximately 100% Ag. On the other side, the surface component of white-colored titanium metal was titanium dioxide.ConclusionTwo methods of white coloration for metals were developed. One method is use of injection molding especially for prevention of crushing of ceramics when combined with them. The other is a white-colored surface preparation for dental appliances, including orthodontic appliances.