Ultrasonic assisted high rotational speed diamond machining of dental glass ceramics

摘要

Subsurface damage and edge chipping remain a persistent technical challenge for the abrasive machining of dental restorations made from glass ceramics, and they impede the fabrication of long-lasting dental restorations. This paper reports on an integration of ultrasonic assistance to dental high-speed rotary abrasive machining for improvement of the surface quality of glass ceramics. An ultrasonic assisted computer-controlled high-speed rotary cutting apparatus was designed and fabricated with functions of ultrasonic vibration, automatic cutting, and force measurement. A multi-phase feldspar glass ceramic with the highest brittleness among glass ceramics was selected for the study. Machining forces, surface roughnesses, and edge chipping damage were evaluated for a range of cutting conditions with and without ultrasonic vibrations. Our most significant finding is that ultrasonic assisted machining led to a clear and consistent reduction of edge chipping and thus subsurface damage. Ultrasonic machining also achieved significant reductions in normal and tangential forces, and surface roughness at higher removal rates (p 0.05). Our results suggest that ultrasonic assisted dental machining may be a way to improve quality and lifetime of ceramic dental restorations, whose failures are rooted in chipping damage and surface flaws using current machining techniques.