Fundamentals and Applications of Biophotonics in Dentistry Anil Kishen Anand Asundi Imperial College Press Vol.4 Series on Biomaterials and Bioengineering Fundamentals and Applications of Biophotonics in Dentistry SERIES ON BIOMATERIALS AND BIOENGINEERING Series Editors: A W Batchelor (Monash Univ. Sunway Campus Malaysia Sdn Bhd) J R Batchelor (UK) Margam Chandrasekaran (Singapore Institute of Manufacturing Technology, Singapore) Vol. 1: An Introduction to Biocomposites by Seeram Ramakrishna (National University of Singapore, Singapore), Zheng-Ming Huang (Tongji University, China), Ganesh V Kumar (National University of Singapore, Singapore), A W Batchelor (Monash University Malaysia, Malaysia) Joerg Mayer (TECIM, Switzerland) Vol. 2: Life-Enhancing Plastics: Plastics and Other Materials in Medical Applications by Anthony Holmes-Walker (Biolnteractions Ltd, UK) Vol. 3: Service Characteristics of Biomedical Materials and Implants by Andrew W Batchelor (Monash University Malaysia, Malaysia) and Margam Chandrasekaran (Singapore Institute of Manufacturing Technology, Singapore) Vol.4 Series on Biomaterials and Bioengineering Fundamentals and Applications of Biophotonics in Dentistry Anil Kishen National University of Singapore, Singapore Anand Asundi Nanyang Technological University, Singapore Jft^ Imperial College Press Published by Imperial College Press 57 Shelton Street Covent Garden London WC2H 9HE Distributed by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. FUNDAMENTALS AND APPLICATIONS OF BIOPHOTONICS IN DENTISTRY Series on Biomaterials and Bioengineering — Vol. 4 Copyright © 2007 by Imperial College Press All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 1-86094-704-2 Printed by Fulsland Offset Printing (S) Pte Ltd, Singapore PREFACE Biophotonics is revolutionizing the field of medicine, biology and chemistry and creating a new breed of medical engineers while at the same time getting engineers a taste of medicine. From an engineer's perspective, biophotonics is the application of photonics - the technology of generating and harnessing packet of light energy called photons - to image, detect and manipulate biological materials. In biology the understanding of molecular mechanisms, function of proteins and molecules has seen great new advances. In biomedical engineering detection, diagnoses and treatment targeting both macro-objects like the teeth or bone as well as micro-objects such as bacteria have seen better understanding through the development of new tools. There is another school of thought, albeit much smaller that defines biophotons as a quantum of light that is permanently and continuously emitted by all living systems. For example, humans emit radiation similar to a blackbody with maximum power being emitted at a wavelength of about 10 um. Regardless of definition, biophotonics is a multi-disciplinary field that bridges engineering, the sciences and medical fields. This diversity of sciences and technologies usually makes for challenging and interesting projects - that could be driven by engineers and clinicians alike. However, there is still the need that clinicians understand some concepts in photonics while engineers get a feel for medical and bio-chemical sciences. Towards this end, this book is written by persons from different fields such as engineering, sciences and medical field. The book is roughly divided into two sections - the first introduces the readers to some basic concepts in the field of biophotomechanics. As the name suggests, this topic looks at the use of optical methods (photo) for the study of mechanical behaviour (mechanics) of biological objects v VI Preface in the macro-scale such as teeth and bone. The next chapter introduces some recent techniques on bioimaging such as fluorescence microscopy and optical coherence tomography amongst others. Chapter 4 introduces spectroscopy - a erstwhile tool in biophotonics while chapter five deals with lasers and laser tissue interaction. Finally Chapter 6 provides an introduction to Photodynamic therapy a growing technology for targeted application of photonic radiations. The second half of the book applies some of these basic concepts to the field of dentistry to highlight some of the features and adaptation of photonics in this area. Dental photomechanics provides an understanding of mechanical and thermal characteristics of dentine and permits a better understanding of the causes of damage and failure of certain treatments. Chapter 8 uses spectroscopic methods specifically Micro-Raman spectroscopy for a better understanding of the materials aspects of dentine and adhesives. The next chapter on Dental and Oral Optics describes tools and techniques for imaging and optical properties of dentine and enamel. The final chapter on fiber optic sensors explores new sensor development for effective and fast ways of detecting and diagnosing oral bacteria. We, as editors, feel that the book would be just as informative for final year undergraduate, graduate students in bioengineering as it would to clinicians and dental surgeons to gain a better understanding of a process or treatment. Anil Kishen and Anand Asundi CONTENTS Preface Chapter 1 Chapter 2 FUNDAMENTALS Introduction 1.1. 1.2. 1.3. 1.4. 1.5. Introduction Definition and Significance Classification of Biophotonics in Dentistry 1.3.1. Diagnostic 1.3.2. Therapeutic 1.3.3. Research Future Opportunities Scope of this Book Photomechanics 2.1. 2.2. 2.3. 2.4. Introduction to Mechanics 2.1.1. Force and Stress 2.1.2. Deformation and Strain 2.1.3. Stress-Strain Equations Basic Optical Engineering 2.2.1. Geometric Optics 2.2.2. Physical (Wave) Optics 2.2.3. Photonics . Photomechanics 2.3.1. Moire and Grid Methods 2.3.2. Speckle Methods 2.3.3. Photoelasticity 2.3.4. Holography 2.3.5. Digital Photomechanics Concluding Remarks 1 2 3 3 4 5 7 8 9 10 13 16 16 17 19 27 30 31 40 46 54 58 60 VI! Vlll Contents Chapter 3 Biomedical Imaging 3.1. Introduction 64 3.2. Non-Linear Optical Microscopy (NLOM): 65 Multiphoton Excited Fluorescence (MPEF) and Second Harmonic Generation (SGH) 3.2.1. Principles of NLOM 66 3.2.2. Development and Applications 69 of NLOM 3.2.3. NLOM in Dentistry 72 3.3. Optical Coherence Tomography (OCT) 73 3.3.1. Principles of OCT 74 3.3.2. Developments and Applications 75 of OCT 3.3.3. OCT in Dentistry 80 3.4. Coherent Anti-Stokes Raman Scattering 82 (CARS) and Modulated Imaging (MI) 3.5. Fluorescence Contrast Enhancement 85 3.6. Concluding Remarks 87 Chapter 4 Spectroscopy 4.1. Introduction 93 4.2. Molecular Orbitals and Transitions 94 4.3. Transition Dipole Moment 99 4.4. Spin Selection Rule 100 4.5. Franck-Condon Principle 102 4.6. Jablonski Diagram 104 4.7. Stokes Shift 107 4.8. Spectrophotometry 108 4.9. Fluorescence Intensity and Lifetime 110 4.10. Spectrofluorimetry 112 4.11. Fluorescence Quenching 115 4.12. Fluorescence Resonance Energy Transfer 116 (FRET) 4.13. Fourier Transform Infrared (FTIR) 117 Spectroscopy 4.14. Concluding Remarks 120 Contents IX Chapter 5 Lasers and Laser Tissue Interaction 5.1. Introduction 123 5.2. Laser Basics 124 5.2.1. Characteristics of Lasers 126 5.3. Light Propagation in Tissue 128 5.4. Optical Imaging and Diagnosis 131 5.4.1. Optical Imaging 131 5.4.2. Optical Spectroscopic Diagnosis 133 5.5. Optical Processing of Tissue 141 5.5.1. Photothermal Effects 142 5.5.2. Photomechanical Effects 144 5.5.3. Photochemical Effects 144 5.5.4. Applications of Laser Processing 145 of Tissue 5.6. Concluding Remarks 148 Chapter 6 Mechanisms and Applications of Photodynamic Therapy 6.1. Historical Background 154 6.2. Photosensitizers 155 6.3. Light Applicators 156 6.4. PDT Mechanisms 161 6.4.1. Photophysics and Photochemistry 161 6.4.2. Biological Effect 162 6.5. PDT Dosimetry 166 6.6. Progress in Clinical Application 167 6.6.1. Non-Malignant Diseases 168 6.6.2. Malignant Diseases 169 6.7. PDT in Dentistry 175 6.7.1. Technical Challenges 175 6.7.2. Current Status 176 6.8. Concluding Remarks 177 [...]... clinical applications 1.3 Classification of Biophotonics in Dentistry Biophotonics in Dentistry is crucial for the early detection of diseases, to carry out more effective minimally-invasive targeted-therapies and to restore diseased tissues functionally and esthetically Different applications of biophotonics in health care are shown in Fig 1.1 Biophotonics in Dentistry can be broadly categorized into... strain in the x-direction Similarly shear strain is the change in the angle between two lines which were initially at right angles to each other Shear strains are represented by the symbol y with subscripts defining the plane of the angle 14 Fundamentals and Applications of Biophotonics in Dentistry Fig 2.3 Displacement and strain Thus from Fig 2.3, we have two normal strains and one shear strain which... gums and benign mouth lesions Bioimaging: Optical and x-ray imaging has influenced the practice of dentistry dramatically Reconstruction of images in both two and threedimensions has allowed better visualization of models and disease processes, allowing quantification of disease changes over time, thus assisting the treatment planning decisions and improving patient care Some of these innovations are in. .. Currently, biophotonics is entering a new era of rigorous clinical testing and evaluation As photonics find major application in health care, it is particularly important that the basic principles and potential pitfalls of technology is also understood Although optical spectroscopy may one 8 Fundamentals and Applications of Biophotonics in Dentistry day replace some of the conventional clinical techniques,... Wave Light Interaction with Tissues 9.3 Time-Resolved Diffusion Measurements 9.4 Optical Properties of Dental Enamel and Dentin 9.4.1 Structure of Enamel and Dentin 9.4.2 Spectral Properties of Enamel and Dentin 9.4.3 Scattering Properties of Enamel 9.4.4 Scattering Properties of Dentin 9.4.5 Waveguide Effects 9.5 Propagation of Polarized Light in Tissues 9.5.1 Basic Principles 9.5.2 Transillumination... less than in clinical Medicine and Surgery Current dental practice has been emphasizing more on (1) early diagnosis and preventions of common oral diseases and (2) to conserve tooth structure as much as possible during restorative procedures Thus Atraumatic and Non Invasive Treatment (ANIT) modalities have been the key thrust in Dentistry today Keeping in mind the tremendous l 2 Fundamentals and Applications. .. needles) of biochemical substances for diagnostic and therapeutic purposes Raman spectroscopy, which is based on Raman scattering, measures the inelastic scattering when high-energy photon interact with a molecule (or crystal lattice) This analytical technique is finding significant application in pharmaceutical industry There is a 6 Fundamentals and Applications of Biophotonics in Dentistry growing interest... generating and harnessing light (photons) to image, detect and manipulate biological materials It is applied in Medicine and Dentistry to understand, diagnosis and treatment of diseases Biophotonics mainly involves the interaction between light with biological tissues, and is used to study biological tissues and biological processes at different scales that ranges from micro to nano-levels Biophotonics integrates... 10 Fundamentals and Applications ofBiophotonics in Dentistry object Hence there are few standard geometric and loading conditions which form the basis of all complex objects and loading systems 2.1.1 Force and Stress External forces acting on a body may be due to mechanical loads or as support reactions Under the action of these forces, the body is said to be in equilibrium if the sum of forces and. .. electrical and optical efficiency In Dentistry the soft lasers have been used for acceleration of wound healing, enhanced remodelling and repair of bone, restoration of normal neural function following injury, normalization of abnormal hormonal function and modulation of the immune system Although low-level light offers many potential advantages in Dentistry, further research is warranted before serious clinical . of Manufacturing Technology, Singapore) Vol. 4 Series on Biomaterials and Bioengineering Fundamentals and Applications of Biophotonics in Dentistry Anil. understanding of mechanical and thermal characteristics of dentine and permits a better understanding of the causes of damage and failure of certain treatments.