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Magnetic Forces in Orthodontics COPYRIGHT AND USE OF THIS THESIS This thesis must be used in accordance with the provisions of the Copyright Act 1968. Reproduction of material protected by copyright may be an infringement of copyright and copyright owners may be entitled to take legal action against persons who infringe their copyright. Section 51 (2) of the Copyright Act permits an authorized officer of a university library or archives to provide a copy (by communication or otherwise) of an unpublished thesis kept in the library or archives, to a person who satisfies the authorized officer that he or she requires the reproduction for the purposes of research or study. The Copyright Act grants the creator of a work a number of moral rights, specifically the right of attribution, the right against false attribution and the right of integrity. You may infringe the author’s moral rights if you: - fail to acknowledge the author of this thesis if you quote sections from the work - attribute this thesis to another author - subject this thesis to derogatory treatment which may prejudice the author’s reputation For further information contact the University’s Copyright Service. sydney.edu.au/copyright MAGNETIC FORCES IN ORTHODONTICS ANGIE C. PHELAN BDSc (Hons I) A thesis submitted in partial fulfilment of the requirements for the degree of Doctorate of Clinical Dentistry – Orthodontics Discipline of Orthodontics Faculty of Dentistry University of Sydney Australia 2010 1 DEDICATIONS To my family and Lachy, Thanks for your support and patience. I could not have made it without your help. 2 ACKNOWLEDGEMENTS I would like to take this opportunity to thank the people who have helped me complete this project: Professor M. Ali Darendeliler, Head of the Department of Orthodontics, University of Sydney for his advice and patience during the preparation of my thesis. Professor Tiziano Baccetti, Professor, Department of Orthodontics, University of Florence for his words of encouragement and involvement with the project. Professor. Dr. Dieter Drescher, Heinrich-Heine-Universität Düsseldorf for his involvement with the project and use of the Robotic Measurement System. Nour Eldin Tarraf, Lecturer, Discipline of Orthodontics, University of Sydney for his help and support during my project. Dr Ralf Hönscheid, Heinrich-Heine-Universität Düsseldorff for his assistance with the measurements. Dr Peter Petocz, Statistician, Department of Statistics, Macquarie University, Sydney for assistance with the statistical analysis 3 Paul Taylor, Honorary clinical lecturer, Department of Orthodontics, University of Sydney for his excellent cases and passion for the Sydney Magnoglide appliance. Dr Carmen Gonzales, Senior lecturer, Department of Orthodontics, University of Sydney for her thoughtful advice with the preparation of my literature review. Dr Okyu Dalci, Lecturer, Department of Orthodontics, University of Sydney for her advice with my literature review and words of encouragement during the preparation of my thesis. The Australian Society of Orthodontists Foundation for Research and Education for their financial support for this thesis. 4 DECLARATION CANDIDATE CERTIFICATE This is to certify that the candidate carried out the work in this thesis in the Orthodontic Department, University of Sydney and has not been submitted to any other University or Institution for a higher degree. Angie C. Phelan 5 TABLE OF CONTENTS DEDICATIONS ACKNOWLEDGEMENTS DECLARATION TABLE OF CONTENTS 1 ABBREVIATIONS ........................................................................................................................ 9 2 INTRODUCTION ........................................................................................................................ 11 3 REVIEW OF THE LITERATURE ............................................................................................... 13 3.1 MAGNETS AND MAGNETIC FIELDS ............................................................................. 13 3.1.1 Magnetisation ................................................................................................................ 15 3.1.2 Magnetic properties of matter ....................................................................................... 16 3.1.3 Permanent magnets ....................................................................................................... 17 3.1.3.1 Alnico Magnets ......................................................................................................... 18 3.1.3.2 Cobalt-platinum Magnets .......................................................................................... 18 3.1.3.3 Ferrite Magnets ......................................................................................................... 18 3.1.3.4 Rare earth magnets .................................................................................................... 18 3.1.3.4.1 Samarium-Cobalt Magnets ................................................................................. 19 3.1.3.4.2 Neodymium-iron-boron magnets ........................................................................ 20 3.1.3.4.3 Samarium-iron-nitride magnets .......................................................................... 20 3.2 BIOLOGICAL CONSIDERATIONS ................................................................................... 21 3.2.1 Surface Oxidation and coating ...................................................................................... 21 6 3.2.2 Static magnetic fields .................................................................................................... 23 3.3 APPLICATION OF MAGNETIC FORCES IN ORTHODONTICS ................................... 26 3.4 MAGNETIC FORCES FOR TOOTH MOVEMENT .......................................................... 27 3.4.1 Molar distalisation......................................................................................................... 28 3.4.2 Extrusion ....................................................................................................................... 29 3.4.3 Magnets and impacted teeth .......................................................................................... 30 3.4.4 Retention ....................................................................................................................... 34 3.5 APPLICATION OF MAGNETIC FORCES FOR TOOTH MOVEMENT IN COMBINATION WITH CLEAR THERMOPLASTIC APPLIANCES.......................................... 35 3.6 CLEAR THERMOPLASTIC APPLICANCES .................................................................... 37 3.6.1 Commercially available systems ................................................................................... 38 3.6.2 Invisalign ....................................................................................................................... 39 3.6.2.1 Indications ................................................................................................................. 40 3.6.2.2 Efficacy of clear aligner therapy ............................................................................... 42 3.6.2.3 Tooth movements ...................................................................................................... 44 3.6.2.4 Advantages ................................................................................................................ 48 3.6.2.5 Disadvantages ........................................................................................................... 50 3.7 ORTHOPAEDIC TREAMENT WITH MAGNETIC FORCES .......................................... 52 3.7.1 Expansion ...................................................................................................................... 52 3.7.2 Openbite ........................................................................................................................ 53 3.7.3 Class III Magnetic Functional Appliances .................................................................... 58 3.7.4 Class II Magnetic Functional Appliances ..................................................................... 59 7 3.8 NEW MAGNETIC FUNCTIONAL APPLIANCE FOR ORTHOPAEDIC CORRECTION .. .............................................................................................................................................. 64 3.9 FUNCTIONAL APPLIANCES IN THE TREATMENT OF CLASS II MALOCCLUSION . .............................................................................................................................................. 65 3.9.1 Class II malocclusion .................................................................................................... 65 3.9.2 History of functional appliances ................................................................................... 68 3.9.3 Types of functional appliances ..................................................................................... 70 3.9.4 Indications ..................................................................................................................... 71 3.9.5 Advantages and Limitations .......................................................................................... 71 3.9.6 Mode of action .............................................................................................................. 72 3.9.7 Effects of functional appliances .................................................................................... 73 3.9.7.1 Animal studies .........................................................................................................
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