Mechanisms Of Radial Ultrasonic-Assisted Dental Abrasive Adjustments Using High-Speed Handpieces

Dental abrasive adjustments using high-speed handpieces and burs is an essential and key procedure in dentistry.In order to improve the quality of ceramic restorations and the comfort of patients,a novel ultrasonic-assisted dental abrasive adjustment method is proposed.The mechanisms of the radial ultrasonic vibration on the traditional dental adjustments are studied.This project is supported by the National Natural Science Foundation of China.The main results are as follows:An ultrasonic-assisted dental abrasive adjustment instruments was designed,which could in real time monitor ultrasonic vibration parameters and adjustment parameters in the process of experiment.Through the device,the influence of the radial ultrasonic vibration on the grinding force in the dental abrasive adjustments was studied.The results showed that the normal force could be decreased by 5.71%~ 47.15%.Meanwhile,the tangential force could be reduced by 0.24%~43.78% by using standard burs after adding ultrasonic vibration of 0.2W.The normal force could be reduced by 8.39%~22.74% and the tangential force could be decreased by 16.44%~38.41% when using fine burs after adding ultrasonic vibration of 0.4W.In the aspect of diamond bur wear,the influence of radial ultrasonic vibration on dental abrasive adjustments was studied by the tungsten filament scanning electron microscope.The results showed that the wear of the standard bur was mainly abrasive shedding when feed speed was 30mm/min.The wear was light when feed speed was 15mm/min.The phenomenon of abrasive shedding was significantly improved after adding radial ultrasonic vibration.The grain breaking of the fine bur was serious and its surface was blocked by abrasive dust when dry grinding.Abrasive dust was removed after adding cooling liquid.The number of the dropped grains was decreased by 14.75% after adding radical ultrasonic vibration.In the aspect of surface quality,the surface roughness and surface morphology were systematically studied by means of non-contact 3D roughness tester and scanning electron microscope.Arithmetical mean height and maximum height were reduced after adding radial ultrasonic vibration of 0.2W.The values of Sa and Sz would be instable after the power was increased.Radical ultrasonic vibration not only made plastic removal zone and tiny broken zone increase,but also improved ragged edges of ceramic prostheses when using standard burs.The above results indicate that ultrasonic vibration can effectively decrease the grinding force and improve surface quality in the dental adjustment using high-speed handpieces and burs,which has opened up a new method for the dental adjustment technology.