طراحي و تحليل عملكرد ميني اسكرو جهت استفاده در ارتودنسي

چكيده انگليسي :

Orthodontics Miniscrews Design and Analysis Fatemeh Mottaghi Dastenaei f mottaghi@me iut ac ir Date of Submission 18 01 2015 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor s Name and Email address Mahdi Moghimi Zand mahdimoghimi@ut ac ir SaeedNoorollahian s noorollahian@dnt mui ac ir Abstract Miniscrews are temporary anchorage devices TADs which are widely used for orthodonticsdisplacements aims Miniscrews are used to anchorage teeth and causing orthodontics movements includingspace closure space open open bite treatment and uprighting of posterior teeth Miniscrew loosening is acommon problem which usually occurs at the first two weeks during treatment When the screw loses theprimary stability failure is normally due to loosening Macrodesign can affect stability of miniscrew bychanging in diameter length thread pitch thread shape tapering angle etc The purpose of the present studyis to design an ergonomic miniscrew by considering economical benefits and better properties than minisrewshave gained popularity such as Jeil Screw cortical and spongy bones were modeled in tha CatiaPart Assembly design software Then they were imported to the Abaqus CAE Forces and boundaryconditions BCs were applied too In this study a 3 D finite element analysis FEA has done to show theeffect of thread pitch and thread shape variant on stress distribution pattern of the screw cortical boneinterface and maximum von Mises stresses While orthodontics forces were applied stresses were usuallyconcentrated at the first involved thread of the screw in contact by cortical bone Cortical bone providedsignificant percentage of stability than trabecular bone against orthodontics forces by absorbing most of thestresses Therefore spongy bone was removed from the FEA The changes of maximum von Mises stresseswere shown on the charts in the analysis of thread pitch and thread shape The results showed that stressesdecrease while thread pitch decreases but they enhance when thread pitch becomes less than a certain value The results showed that the stresses increase when the apex angle of the thread decreases Hence the buttressreverse thread is the favor thread shape to gain most pullout strength we decreased the lower angle when theupper angle was fixed on 90 degrees in the means of stress decreasing But no significant influence was seen In each FEA the stresses were concentrated on the tip of the threads But the pattern of stress distributiondiffered when the stresses were enhanced in the gained curve of the thread pitch analysis The results arebeneficial to design an ergonomic miniscrew Based on the results a new dual miniscrew is recommended Adual thread miniscrew is a screw by two different pitches which interface cortical or spongy bone Aftermodeling the results of the FEA showed that new design is better than Jeil design under orthodontics forcesand torque of implantation Also the dual thread screw shows a signi cant lower maximum insertion torque MIT than typical screws when the bone meets microthreads which causes to reduce the risk of fracturesignificantly But we should notice that excess helix angles for a faster insertion may jeopardize the ability ofimplants to transfer axial load So we can design trapezoid shape of microthreads to protect triangular shapeof spongy threads against vertical loads All of these are the reasons to show that new model is moreergonomic than Jeil model Cutting flute was another parameter which was studied in FEM In the final stepof design patient satisfactory was considered too Biometal selection based on biocompatibility propertieswas another section of the study It is forecasted that the laboratory future tests will show positive results Keywords Miniscrew Ergonomic design TADs FEA MIT

متقي دستنائي، فاطمه

طراحي و تحليل عملكرد ميني اسكرو جهت استفاده در ارتودنسي

ريز پيچ , طراحي ارگونومي , تجهيزات موقتي , بررسي اجزاء محدود , بيشينه گشتاور ورود