| The metal lingual appliance has the advantages of beautiful appearance,good utility and a wide range of applicable diseases.Brackets and arch wires are the key components of the lingual appliance.The existing brackets are general-purpose parts produced in a standardized manner,which have the disadvantages of weak tooth sticking and poor applicability for patients.The orthodontic force and orthodontic trajectory of the existing orthodontic arch wires mainly rely on the clinical experience and subjective judgment of orthodontists,resulting in low correction efficiency and poor patient experience.In order to solve the above problems,a new type of lingual personalized appliance was studied.This thesis uses 316L stainless steel as the material,based on metal 3D printing technology(SLM)to complete the design and manufacture of personalized lingual brackets.Based on the biomechanical principles of lingual orthodontic treatment,computer numerical simulation technology is used to obtain the optimal orthodontic force and tooth correction trajectory of the patient’s lingual correction,and to determine the bending and personalized archwire according to the orthodontic force and tooth correction trajectory methods.The main work and research results are listed as follows:(1)A new type of automatic tooth arrangement process is designed.Firstly,the patient’s digital tooth model is obtained by three-dimensional scanning.Furthermore,the occlusal plane is determined according to the three-point method.Secondly,the characteristic points is determined in accordance with the relationship between the occlusal plane and the characteristic points of the dental arch line(θ<15° and d<5mm).Thirdly,the dental arch line is determined by the position parameters of the feature points are brought into the β function.Finally,the deformed teeth of the patients is arranged with a standard of the dental arch line.This process can improve the efficiency of tooth arrangement and provide standards for orthodontics.(2)The optimal position of orthodontic force application is determined to be the middle part of the crown(1/2 of the tooth)through the finite element simulation of the patient’s lingual orthodontics,and the optimal magnitude and direction of the orthodontic force is determined.According to the magnitude and direction of the orthodontic force,the orthodontic trajectory is determined.(3)A personalized self-locking brackets and arch wires suitable for individual patients is designed.The bottom surface of the brackets fully fits the inside of the patient’s teeth,and the brackets structure has self-locking function,which simplifies the process of disassembly of the arch wire.At the same time,based on the simulation results of the tooth orthodontic trajectory,a personalized arch wire production process is established:tooth orthodontic trajectory-arch wire bending parameters-arch wire bending.(4)The influence law and compensation method of brackets 3D printing forming errors are studied.Studies have shown that the factors that cause the vertical errors of the bracket include deep laser penetration,bulging of the outer frame,material shrinkage,and lifting of the forming cylinder,which can be offset by setting the displacement of the forming cylinder.The factors that cause the level errors of the bracket include quite wide melt channel,sticky powder,etc.,which can be eliminated by pickling and polishing.Through the above methods,the brackets that meet the size standards are successfully manufactured,and the maximum relative error is only 0.04%.(5)Post-processing techniques such as heat treatment and laser cladding are used to effectively improve the comprehensive performance of the brackets.The results show that when the normalizing heat treatment temperature is 1050℃,the strength and stiffness of the brackets are the best,which are 715.417Mpa and 2899.919N/mm respectively;when the energy density of laser cladding is 90 J·mm3 and three times of cladding,the surface properties of brackets are the best,the surface roughness Ra is 1.15,the surface hardness is 308.3HV,and the average surface friction coefficient is 0.8.The above research shows that the lingual individualized self-locking appliance designed in this thesis has the advantages of good comprehensive performance,high precision and strong patient applicability,which obtains a high-efficiency tooth arrangement process.The orthodontic simulation shows that the appliance meets the requirements for use,and the research results will promote the development of lingual correction technology at home and abroad. |
