Study Of Orthodontic Wire Bending And Processing Method Based On Visual-touch Fusion

This paper addresses the problems of low processing efficiency,high labor cost and poor precision caused by the manual bending of orthodontic archwires by dentists,which affect the wearing comfort and orthodontic effect,etc.By systematically analyzing the status quo of the automatic bending and 3-dimensional dimensional inspection technologies of orthodontic archwires at home and abroad,we established a binocular stereo vision 3-dimensional dimensional inspection method for orthodontic archwires and analyzed the relationship between bending force and rebound during the bending of archwires,and established a robotic bending system for orthodontic archwires based on the visual-touch fusion control method,and verified the feasibility of the method through the bending tests of archwires of different materials.Firstly,a binocular stereo vision measurement scheme was established for the structural characteristics of orthodontic archwires.The camera was calibrated by the Zhang-Youzheng calibration method,the orthodontic archwire images were enhanced by median filtering noise reduction and histogram equalization,and the contours extracted based on the improved seed filling method were refined by the Zhang-Suen refinement algorithm.The refined contour of the archwire is treated as a deformable linear target,and the line features of the main body of the archwire are extracted using the improved Hough transform algorithm after determining the candidate search region of the improved Hough transform by the feature points extracted by the Harris algorithm.The 3D model of the orthodontic archwire was obtained based on the stereo matching of the line features.Then,we established a mathematical model of the rebound of orthodontic archwire of different materials by analyzing the rebound deformation process of orthodontic archwire bending.Based on the finite element analysis technique,the rebound simulation model of orthodontic archwire bending process was established by simplifying the archwire model,and the stress changes of the archwire before and after the rebound and the influence of the bending angle on the rebound angle were solved,which provided the basis for the preliminary determination of the bending force of the archwire.Finally,a tactile fusion orthodontic archwire processing control scheme with binocular stereo vision and robotic hand was established.The orthodontic archwire bending test platform was built with Barrett Hand BH8-280 robotic hand and WAM^TMrobotic arm,and the visual-touch fusion control system software was written based on Visual Studio Code development environment.The maximum deviation between the standard orthodontic archwire model and the processed archwire was less than 1.00mm,which verified the feasibility of the processing method through the testing of nickel-titanium alloy archwire,cobalt-chromium-nickel alloy wire,β-titanium alloy archwire and chromium-nickel stainless steel wire.