| The application of high strength glass ceramics in the field of oral prosthodontics is more and more prominent because of its excellent mechanical properties and unique aesthetics.However,the excellent mechanical properties of high strength glass ceramics also bring severe challenges to the oral adjustment and grinding,which seriously restrict the application of high strength glass ceramics in the oral cavity.Supported by the national natural science foundation of China,this paper proposes an ultrasonic vibration assisted oral grinding method to improve the cutting efficiency and surface quality.The research contents and conclusions are as follows: 1.After conventional oral high-speed grinding of high-strength glass ceramics,it was found that the grinding force was 2~5 times higher than that of low-strength glass ceramics,the grinding energy was 4~6 times higher than that of low-strength glass ceramics,and the edge crushing size was 80% larger than that of low-strength glass ceramics.When the removal rate was 1.8mm3/mm/min,violent vibration occurred,reaching the grinding limit.In addition,a machinability mathematical model was established to quantify the difficulty of dental ceramic cutting.2.In order to solve the problem that conventional oral grinding cannot meet the requirements of high-strength glass ceramics,a method of ultrasonic vibration assisted grinding was proposed.Theoretical research was carried out from the kinematics analysis and the track motion model of abrasive particles,and the ultrasonic vibration assisted grinding experiment system was designed and built.With the help of the experimental system,ultrasonic vibration assisted grinding mechanics experiment and surface quality evaluation experiment were completed.3.The experiment of ultrasonic vibration assisted grinding shows both axial and radial ultrasonic vibration can reduce the grinding force by up to 36%,and it is found that the reduction amplitude of radial ultrasonic vibration assisted grinding is larger.4.Ultrasonic vibration assisted grinding surface quality experiment shows that ultrasonic vibration can improve the roughness of the processed surface and make the surface waveform flatter.At the same time,the surface morphology of grinding can be improved,increasing the plastic area and reducing the fracture phenomenon.In the case of large cutting depth,ultrasonic vibration can also effectively reduce the size of high strength glass ceramic edge breakage,up to 40%.The above research shows that the ultrasonic vibration assisted grinding of high strength glass ceramics can not only reduce cutting force but also improve the quality of fine-grinding.The ultrasonic assisted grinding method provides a new research direction for the fine-grinding of the clinical surface of dental high-strength restorations. |
