Microstructure analysis of dental castings used in fixed dental prostheses—a simple method for quality control
In the present investigation the microstructure and bonding between the wrought and cast elements of the post and core specimens were evaluated with respect to the preheating temperature of the investment. Clinically sized specimens were produced from one type III gold casting alloy in combination with two different wrought wire precious alloys. Preheating temperatures of 500 degrees, 600 degrees, 700 degrees, 800 degrees and 900 degrees C were employed. Microscopic evaluation of polished and etched transverse and longitudinal sections of the specimens indicated that recrystallization of the wrought wire was initiated at 700 degrees C for one type of specimen. The best reproduction of the wax pattern was obtained at 800 degrees C for post and core combinations. The union between the wrought and cast elements was, regardless of wire type, better in the core portion than in the post. The best union between cast and wrought structures was obtained with a non-oxidizing wire at 700 degrees C.