Design Of Personalized Dental Appliance And Preparation Technology Of Laser Selective Melting

The lingual dental appliance has the advantages of high concealment and high aesthetics,and is widely used in the orthodontic industry.However,there are still problems such as low accuracy,inaccurate expression of orthodontic force,and poor mechanical performance.In response to the above issues,this thesis designed a personalized lingual dental appliance,and used Ti6Al4 V powder as the raw material to study laser selective melting molding and post processing technology.The obtained dental appliance not only meets the requirements of mechanical properties,wear resistance,and corrosion resistance,but also shows that the appliance has high orthodontic accuracy and accurate orthodontic force expression through in vitro simulation testing.The main research content and results of this thesis are as follows:(1)Research on digital dental alignment system.Using reverse modeling to construct a three-dimensional model of orthodontic patients’ teeth,determine the optimal occlusal surface,analyze key factors that affect the shape of the dental arch curve,and fit the personalized optimal dental arch curve.Based on the dental arch curve,OpenGL graphics library is configured in Visual Studio 2019 to achieve digital dental alignment through mutual conversion of three-dimensional coordinates,obtaining a model of expected orthodontic effects for patients,laying the foundation for personalized and accurate orthodontics.(2)Biomechanical simulation of precise orthodontic treatment of teeth.Based on the theory of orthodontic medicine,using periodontal membrane stress and tooth movement efficiency as evaluation indicators,the optimal location and size of orthodontic load application were analyzed by finite element simulation.The results show that when moving obliquely,the middle 1/3 remote midplane is the best loading position;During rotational movement and overall movement,the remote middle surface of the neck 1/3 is the best position for applying load.The optimal range of orthodontic force application during oblique movement is 24.0 to 152.13 g.When rotating and moving,the torque application range is 34.18 to 168.24 g·mm.When moving as a whole,the torque to force ratio ranges from 0 to 5.1.(3)Personalized lingual tooth self-locking appliance design.Based on the results of finite element analysis and existing dental appliance design theories,a personalized lingual tooth self-locking appliance was designed.The appliance is closely attached to the lingual side of the tooth,which is beneficial to improving the bonding strength.Using a double hole structure that combines circular and square holes,the circular hole applies orthodontic force and the square hole applies torque,which helps to improve the orthodontic accuracy of teeth.The overall structure is self-locking,avoiding the use of ligation wires to bind the arch wires,effectively reducing friction resistance,shortening the orthodontic cycle,and improving orthodontic efficiency.(4)Error analysis and control of laser selective melting molding.Through block forming experiments,the formation rules and control methods of laser selective melting forming errors are analyzed.The research shows that the Zdirection error is always greater than the X-Y direction error,and the Z-direction error is proportional to the number of molding layers,which can be offset by error compensation.The X and Y direction errors mainly come from the "splash phenomenon" generated during laser selective melting molding.Reasonable energy density and spot compensation radius can effectively reduce the "splash phenomenon".The experimental results indicate that the forming process of the orthodontic appliance is:laser compensation radius 0.1mm,laser power 120 W,scanning speed 900 mm/s,slice thickness 0.03 mm,scanning spacing 0.08 mm,the absolute error in X and Y directions decreases by 59.62%,and the Z direction decreases by 41.67%.(5)The influence of post treatment technology on the comprehensive performance of the appliance.To study the effect of heat treatment process on the comprehensive performance of dental appliances.The results show that after heat treatment at different temperatures,the mechanical properties first increase and then decrease.After being kept at 900℃ for 2 hours and cooled in the furnace,the mechanical properties reach the best,with a tensile strength of 1199.58 MPa,increasing by 62.64%;The bending strength reached 2765.26 MPa,increasing by 13.38%.The grain size is significantly increased,the grain boundaries are relatively clear,the phase content gradually increases,and the proportion of equiaxed tissue decreases sharply.The surface hardness reaches 495.55 HV,the surface friction coefficient is 0.35,and the corrosion current density is 0.08 A/cm2.After sandblasting and polishing the surface of the dental appliance,the surface roughness Ra reaches 2.19 μm,and all the above properties meet the national standards.After in vitro simulation testing,it is shown that the personalized dental appliance prepared in this thesis not only has high accuracy,accurate expression of orthodontic force,but also has good mechanical properties,and has a broad application prospect in the orthodontic industry.