Machinability Evaluation of a Ti-Ag Alloy Using a Dental CAD/CAM

Objectives: In recent years, many dental CAD/CAM systems have been commonly used to fabricate dental prostheses. The durability of tungsten carbide burs is influenced by the machinability of metal. The purpose of the present study was to evaluate the machinability of a Ti-Ag alloy by measuring the durability of the tungsten carbide burs. The durability of the bur was measured after fabricating a framework using a Ti-Ag alloy and commercial pure titanium by a dental CAD/CAM system. Methods: Experimental Ti-20mass% Ag alloy (Ti-Ag) blocks were made using a dental titanium-casting machine, subsequently, the blocks were machined to fabricate the framework using a dental CAD/CAM system (GN-I, GC, Japan). Pure titanium (CP-Ti, JIS grade II) blocks were also machined as a control. Fifteen identically sized blocks were prepared from each metal. Each bur was used to machine three blocks. The cutting edges of the burs were observed by SEM after every use. The attrition parts of the cutting edges of the SEM image were traced. The durability was evaluated by measuring the area of the attrited part of the cutting edges. The data (n=5 for each condition) were compared to the data for Ti-Ag and CP-Ti using Student's t-test (a=0.05). Results: The attrition area of the cutting edges increased with the number of uses, and that of the Ti-Ag alloy was about 68% less than that of CP-Ti after the first use. However, there was no significant difference. After the second use, the area of the Ti-Ag alloy was about 65% less than CP-Ti, and about 55% after the third use. There were significant differences (p<0.05). Conclusion: It was concluded that, in terms of tool life, the machinability of the Ti-20%Ag alloy was superior to that of pure titanium.