An Improved CVDD Bur Used in Ultrasonic Dental System for Enamel Removal

The aim of this paper is to increase enamel removal rate of dental diamond bur used in ultrasonic system so as to realize and promote its clinical applications. The cutting performances of the burs made by the electroplated diamond and by the chemical vapor deposition diamond (CVDD) are compared by experiment. It is found that the CVDD bur can achieve a higher removal rate. Detailed observation of the microphotograph of cut surface reveals that the superior performance of the CVDD bur is related to the morphology of the CVDD bur and the chips it produced. There are large amount of small cutting edges on the top of large size diamonds of the CVDD burs which results in tiny cutting chips. The materials along the plowed grooves left by the large size diamonds are removed by the adjacent small cutting edges. This action enables the cutting process to be carried out continuously rather than clogging the downward movement of the tool as experienced by the use of the electroplated diamond bur. But on the other hand, the too small chips also restrict the enamel removal rate. Hence a novel design of improved CVDD bur with fewer small cutting edges is proposed. The amount of cutting edges is reduced by heating the existing bur at 700 °C for various time periods. It is found that the enamel removal rate along and perpendicular to enamel prism directions can be increased by 60% and 30%, respectively as compared with the untreated CVDD bur when it is heated in the nitrogen environment for 10 minutes.