Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.
OBJECTIVE
This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points.


METHODS
Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test.


RESULTS
When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (p<0.05) higher M-indexes than the diamond points after any heat treatments. With the SiC wheels, increasing the circumferential speed increased the M-index values for each heat treatment. The specimens heat-treated with AC, HA and IA had similar M-indexes at the lower speeds (500 and 1,000 m/min). The ST specimens exhibited the lowest M-index at the lower speeds. However, at the highest speed (1,500 m/min), there were no significant differences in the M-indexes among the heat treatments except for HA, which showed the highest M-index.


CONCLUSIONS
There was no effect of heat treatment on the machinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.
Watanabe
I
I
Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M University System Health Science Center, 3302 Gaston Avenue, Dallas, TX 75246, USA. iwatanabe@tambcd.edu
Baba
N
N
Watanabe
E
E
Atsuta
M
M
Okabe
T
T
D001831:Body Temperature; D017554:Carbon Compounds, Inorganic; D003735:Dental Casting Technique; D003748:Dental Equipment; D003775:Dental Polishing / Q000295:instrumentation; D018130:Diamond; D006047:Gold Alloys; D006244:Hardness; D006358:Hot Temperature; D008669:Metallurgy / Q000295:instrumentation; D009055:Mouth; D017655:Silicon Compounds
D017554:Carbon Compounds, Inorganic; D006047:Gold Alloys; D017655:Silicon Compounds; D018130:Diamond; C022088:silicon carbide