In-process assessment of dental cutting of a leucite-reinforced glass–ceramic

This paper reports an in-process assessment of the dental cutting of a leucite-reinforced glass–ceramic with a high-speed dental handpiece under clinical operating conditions. The dental cutting was performed using a computer-controlled 2-degrees-of-freedom (2-DOF) testing regime and a coarse diamond bur of 106–125 μm grit size. Dynamic forces were monitored during the cutting process using a piezoelectric force dynamometer and a data acquisition system in both time and frequency domains. Bur speeds were found to decrease with the depth of cut and with the feed rate, by a maximum of 10.5% from the free-running speed of 322.2 krpm (1 krpm = 1000 rpm) to 288.4 krpm at the highest feed rate of 60 mm/min and depth of cut of 50 μm. Both the tangential and normal forces increased with the depth of cut and the feed rate, in the ranges of 0.24–1.77 N and 0.60–2.93 N respectively. The torque increased with the depth of cut and feed rate. The specific cutting energy generally decreased with the depth of cut or the feed rate with the exception of a small-scale fluctuation at the higher depth of cut and feed rate. The dental cutting characteristics for the leucite glass–ceramic were similar to those for the feldspathic porcelain but had higher magnitudes.