Research On Ultrasonic Vibration Assisted Grinding Technology Of Zirconia Ceramic Denture

With the all ceramic crowns widely used,Zirconia ceramics as dental materials that are closest to the human tooth have been widely used in dental restoration,owning to their superior biocompatibility,high strength,excellent wear resistance,and chemical stability.In conventional machining dental prosthesis process,more and more problems for presintered zirconia ceramics are exposed,such as difficult to control shrinkage,high fracture rate.Base on the material properties and complex surface topography of zirconia ceramic crowns,it is very difficult to machine sintered zirconia ceramics by conventional technologies.These problems severely restricted the development of prosthodontics technology.in this paper,a new method which used ultrasonic vibration assisted grinding(UVAG)zirconia.ceramics denture is proposed.The basic theory and the feasibility of UVAG on zirconia ceramics are studied through.the research of grinding cutting force,temperature and surface quality experiment.The work conducted in this paper is as follows:(1)This paper presents a mathematical model for feed direction cutting force in UVAG of zirconia under the consideration of amplitude and frequency,and assuming that brittle fracture is the primary mechanism of material removal in UVAG of zirconia ceramics.Besides,the number of active abrasive particles is calculated with analyzing the influences of lateral cracks and ultrasonic vibration.Through the combination of model prediction and validation experiments,the influences of tool parameters,grinding parameters and vibration parameters on grinding force are clarified and the rationality and effectiveness of the model are verified.(2)Based on the analysis of the grinding temperature field and the established grinding force model,a mathematical model of grinding temperature of zirconia ceramic by UVAG is proposed.The effects of tool parameters,grinding parameters and vibration parameters on grinding force are clarified.Finally,pilot experiments are carried out to validate the rationality and effectiveness of the model.(3)The experimental research on the surface quality in UVAG of zirconia ceramic was carried out.Then,the effects of grinding parameters and ultrasonic vibration parameters on surface roughness,surface texture,and surface topography of dental zirconia ceramics are analyzed.And the advantages of ultrasonic vibration assisted grinding are analyzed by comparison with conventional grinding.The experimental results show that UVAG can effectively reduce the surface roughness and surface damage.It also could improve the three-dimensional surface morphology.Tis study provides theoretical and experimental basis for the application of UVAG in the field of dental prosthetics.