Research On The Theory And Technology Of High Precision Chairside Molding Of Polyetheretherketone Denture

With the improvement of people’s living standards and the application of new materials in the field of restorative dentistry,people are beginning to be dissatisfied with the restorative experience provided by current dental materials such as ceramics and composite resins.Polyetheretherketone(PEEK)is considered as one of the most promising dental materials due to its excellent biocompatibility,fatigue resistance,radiation transmittance and mechanical properties.In this thesis,we have systematically investigated the use of PEEK as a chairside denture forming technology to obtain a combination of highly efficient denture forming parameters under high precision constraints,which is important for the use of PEEK as a chairside dental material for dental prosthetics.Firstly,theoretical research was conducted on the fast and efficient acquisition method of high precision denture 3D models.The difficult problems of PEEK denture milling and shaping were investigated,including the milling process,tool parameters and process parameters of the PEEK denture.The tool trajectories for the roughing and finishing stages were planned rationally,laying the theoretical foundation for the design and development of subsequent PEEK milling experiments and the milling and shaping of PEEK prostheses.Two ways of obtaining high precision milling and shaping parameters for the chairside PEEK denture were identified,one being the optimization of high efficiency milling parameters in the roughing stage and the other being the multi-objective optimization of high efficiency and precision milling parameters in the finishing stage of the denture.Secondly,aiming at the high efficiency requirement of PEEK denture chairside forming,the mathematical model of material removal rate(MRR)and key milling parameters was established.PEEK milling simulations based on the Abaqus platform were used to obtain cutting force constraint functions to meet the environmental requirements of chairside restorations.Genetic Algorithm(GA),which simulates the superiority of natural populations,was used to solve for the optimal combination of parameters for the maximum material removal rate in the roughing stage of PEEK denture milling and shaping.Using the optimal parameter combinations for the rough machining of PEEK anatomical full crowns,it was found that machining times were reduced by more than 50% compared with that before optimization.Then,effect of the main milling parameters on the surface roughness of PEEK was investigated in relation to the high precision requirements of chairside denture forming.The results indicated that the feed of per tooth had the deepest effect on PEEK surface roughness,followed by radial depth of cut and the smallest axial depth of cut.The spindle speed affected the surface roughness of PEEK but without significant effect,and there was no significant coupling between the milling parameters.Backpropagation(BP)neural network was trained based on the experimental data to map the surface roughness values to the key milling parameters.The GA was used to optimize the structure of the BP neural network to improve the prediction accuracy and stability of the model.The prediction error of the established GABP neural network was within 4% and can be applied to predict the surface roughness of the PEEK denture after finishing.Finally,in the PEEK chairside milling and shaping finishing stage,the multiobjective optimization problem was studied based on the NSGA-II intelligent algorithm.The obtained MRR and GABP neural network models were determined as the optimization objective functions for high efficiency and high precision,respectively.The solution sets for the combination of parameters with lower surface roughness values and larger material removal rates under the accuracy constraints were obtained.The superiority of the established NSGA-II-MRR-GABP neural network optimization model was verified by comparative analysis.Six sets of parameter combinations were also randomly selected from the solution set for the finishing of PEEK anatomical full crowns.The results showed that all PEEK anatomical full crowns met the high precision requirements and the finishing time was within 23 minutes and the total machining time was within 35 minutes,fulfilling the clinical requirement of efficient and high precision for chairside restorations.