Basic Guide to Dental Radiography

Basic Guide to Dental Radiography BASIC GUIDe to DentAL RADIOGRAPHY Tim Reynolds Education Consultant in Dental Radiology This edition first published 2016 © 2016 by John Wiley & Sons, Ltd Registered Office John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial Offices 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 1606 Golden Aspen Drive, Suites 103 and 104, Ames, Iowa 50010, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley‐blackwell. The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. All rights reserved. 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No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom. Library of Congress Cataloging‐in‐Publication Data Names: Reynolds, Tim (Lecturer in radiography), author. Title: Basic guide to dental radiography / Tim Reynolds. Description: Chichester, West Sussex ; Ames, Iowa : John Wiley & Sons Ltd., 2016. | Includes bibliographical references and index. Identifiers: LCCN 2016024804 | ISBN 9780470673126 (pbk.) | ISBN 9781118916261 (Adobe PDF) | ISBN 9781118916278 (epub) Subjects: MESH: Radiography, Dental–methods Classification: LCC RK309 | NLM WN 230 | DDC 617.6/07572–dc23 LC record available at https://lccn.loc.gov/2016024804 A catalogue record for this book is available from the British Library. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Cover image: ©gmutlu/gettyimages Set in 9/11pt Sabon by SPi Global, Pondicherry, India 1 2016 I dedicate this text to R. F. Farr, Chacket, John Ball, Brian Murphy and to my father who passed away on 27 September 2013 and will never see this text published though he asked me about it often during its preparation. Contents Acknowledgements viii 1 General physics 1 2 X‐ray production 12 3 X‐ray interaction with matter 27 4 Principles of image formation 36 5 Imaging with dental X‐ray film 46 6 Digital imaging recording 61 7 X‐ray equipment 70 8 Radiation doses and dose measurement 78 9 Biological effects of X‐rays 86 10 Legislation: Ionising Radiations Regulations 1999 (IRR 1999) 94 11 Legislation: Ionising Radiation (Medical Exposures) Regulations 2000 (IR(ME)R 2000), Statutory Instrument 1059 108 12 Quality assurance 114 13 Dental intra‐oral paralleling techniques 128 14 Orthopantomography 159 15 Other dental radiographic techniques 170 Appendix A: Adequate training 189 Appendix B: Image quality troubleshooting 192 Index 201 Acknowledgements A massive thank you is due to my wife and two young children for putting up with the hours I have spent, effectively, an absent husband and father while putting together this text. They have missed me and put up with it in good grace; the advantage of being able to quietly get on with the work has been a blessing although there were times that I would have welcomed an interruption. Also many additional thanks to my wife for allowing me to take and to publish a number of photographs of her in less than flattering circumstances (film holders in position). From my past I must thank Mr R. F. Farr and Dr Chacket, both formerly of the Queen Elizabeth Hospital Birmingham. Also Mr John Ball, sadly no longer with us; he was formerly Deputy Principal of the Dudley Road School of Radiography. The three of them together must form what is probably the greatest physics teaching team ever. Whatever understanding I have of the physics, geometry and theories of imaging in radiography comes largely from their teaching. Lastly, Mr Brian Murphy, formerly Principal of the Dudley Road School of Radiography; he was possessed of the greatest breadth of knowledge of radiography that I have ever encountered. Like John Ball, Brian is no longer with us but will always be remembered; he was a great teacher, mentor and in later years a very good friend. The career that I built was through his example and his guidance; I owe him much and he will not be forgotten. These four together have provided the vast bulk of the information contained within these pages. Chapter 1 General physics ATOMS AND MOLECULES Whenever setting out on a project of this type, it is difficult to know what to use as your starting point. Let us start by looking at what makes up the world as we know it. We look around and see lakes, mountains, fields, etc., but what if we could look into these things and see what makes them what they are? We would see atoms and molecules. There can’t be many people who have not heard of these, but what are they? Atoms and molecules are linked to elements and compounds (here is the problem – almost every time we mention anything, it will lead us straight to something else we need to know). Elements are single chemical substances such as oxygen, hydrogen, sulphur, etc. We can take a large amount of an element and keep cutting it down to make it smaller and smaller, but there is a limit to how small we can make it. We come to a point where all that we have is a single atom of the substance; if we then cut it to an even smaller size, we will be breaking down the atom, and it will no longer be that particular substance. • Atoms are the smallest particle of an element that can exist and still behave as that element. Breaking down an atom eventually produces just a collection of the bits that make up the atom. Here we go again! What is smaller than an atom? Or what are atoms made of? There are many so‐called fundamental particles that make up the atoms that provide the basic building blocks for all of the things that we see, touch and know of. Some of these fundamental particles are only now being discovered. For the purposes of fulfilling the basic guide brief, we will concentrate on only three types of particle: protons, neutrons and electrons. Basic Guide to Dental Radiography, First Edition. Tim Reynolds. © 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd. 2 Basic Guide to Dental Radiography Protons and neutrons are large (that’s relative; remember we would need very powerful microscope to see even these particles), and electrons are small. To represent the difference in these particles in a way you can visualise, think of placing a single grape pip on the ground and then standing a person 6 ft tall next to it. The grape pip represents the size of an electron, and the 6‐ft‐tall person the size of a proton or a neutron. Protons and neutrons are slightly different in size, but for our purposes they can be considered to be the same, but electrons are 1840 times smaller than either of the other two particles. L PHYSICS The protons and electrons each have an electrical charge and these charges are of RA opposite poles (like the two ends of a battery). The protons have a positive charge (+ve), and the electrons a negative charge (−ve). Despite the relative size difference of the particles, the two charges, although opposite GENE poles (or signs), are of equal size or strength.

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