Fundamentals and Applications of Biophotonics in Dentistry

The following sections are included:

• PREFACE

• CONTENTS

The following sections are included:

• Introduction

• Definition and Significance

• Classification of Biophotonics in Dentistry
  • Diagnostic
  • Therapeutic
  • Research

• Future Opportunities

• Scope of this Book

• References

Photomechanics is the application of optical methods (Photo) to solve problems in mechanics. This field has been growing steadily over the past couple of decades especially with the advent of low cost light sources, detectors and CCD cameras and image processing methodology. This chapter has been divided into 8 sections starting with introduction to the field of mechanics and optics. A good understanding of the basic principles of the two pillars of photomechanics would enable easy application in a wide variety of situations. Following this introduction, specific techniques such as Moiré and Grating methods, Photoelasticity, Speckle and Holography are highlighted. The final section looks at the recent advances in Digital Photomechanics, which has made enormous strides in the last decade and has all but made obsolete the ubiquitous photographic film.

The medical community has a strong interest in new, more sophisticated methods for non- or minimally invasive diagnostic or treatment purpose. Biophotonics is one of the most rapidly changing and promising fields of biomedical imaging undergoing transformation from pure research applications to a clinical setting including studies in oncology, inflammatory processes, wound healing, pharmacokinetics and pharmacodynamics, toxicology, infectious disease, gene expression and more. More reliable, varied and economical light sources (from miniature diode to femto-second tunable lasers), more sensitive and fast detectors (CCD chips, avalanche photodiodes, photomultiplier tubes), and novel interfaces to computers and computational methods, drives the technology development. New concepts of non-invasive imaging (“optical biopsy”, “molecular imaging”) rely on better understanding of the signal's origin, both “native” and exogenous. New reporters (fluorescent proteins, quantum dots) are used for brighter, better-localized, non-bleaching fluorescence imaging. Dynamic assays for oxy-and deoxyhemoglobin ratios, lipid and water content in benign and malignant tissues are being developed using concepts of photon migration and used in cancer research. Multi-modality approaches where different optical imaging modalities synergize with and compliment each other are gaining in momentum and may bring forward many new advantages in biology and medicine in the very near future.

The interaction of electromagnetic radiation with matter is governed by the frequency of the radiation and the properties of the absorber and leads to a variety of phenomena such as scattering, absorption and emission. Different regions of the electromagnetic spectrum and various spectroscopic techniques can be used to extract details of the molecular structure, structural changes and molecular environment of materials. In this chapter, the fundamentals of absorption and emission spectroscopy are discussed with particular reference to biological macromolecules.

This chapter provides an overview of lasers and their interaction with biological tissue and how these are exploited for medical applications. The specific points addressed are – how lasers work and their attributes because of which lasers find such a widespread usage. An overview of optical transport parameters of tissue and laser propagation in tissue is presented next. This is followed by a discussion on the applications of scattered or reemitted light from tissue for diagnosis. The photothermal, photochemical and photomechanical effects of absorbed light and their use for surgical and therapeutic applications are also discussed.

Photodynamic therapy (PDT) is a relatively new treatment modality. It involves the administration of a photosensitizer followed by local illumination with visible light of specific wavelength(s). In the presence of oxygen, the light illumination of photosensitizer can lead to a series of photochemical reactions and consequently the generation of cytotoxic species. The nature, quantity, and location of PDT-induced cytotoxic species determine the nature and consequences of PDT treatment. PDT has received increased attention since the regulatory approvals of several photosensitizers and light applicators in many countries and regions around the world. Much progress has been seen in both basic research and clinical application in recent years. This chapter will introduce the new developments in PDT basic sciences, clinical investigations and clinical applications, and the usefulness of various forms of PDT techniques for curative or palliative treatment of malignant and non-malignant diseases. PDT in dentistry will also be discussed.

This chapter discusses common photomechanical experiments used in dental biomechanics. Methods such as photoelasticity, moiré interferometry and electronic speckle pattern interferometry are described with relevance to applications in dentistry.

The development of tissue-engineered materials that could serve as natural tissue replacements is one of the most exciting areas of investigation in both medicine and dentistry. In the exploration of these new materials, one area that has been largely overlooked is chemical and mechanical characterization of the material/tissue interface. This is a particularly challenging area of investigation since many of the current analytical techniques do not offer the required spatial resolution to study reactions occurring at the interface or the conditions, i.e. temperature, vacuum, and so forth, under which the sample must be analyzed destroy or significantly damage/alter the biologic tissue. To address these problems, we have developed a novel technique using confocal Raman microspectroscopy to characterize and quantify reactions at tissue/tissue and material/tissue interfaces. The analysis is completed under normal atmospheric conditions and the tissue is maintained in a “wet” environment throughout the process. The purpose of this chapter is to provide an overview of the application of this technology to dental substrates and material/tissue interfaces relevant to the development of new materials for dentistry.

This chapter summarizes recent studies on tissue optics and overviews different light scattering approaches that already applied or could be potential for designing of noninvasive technologies for tooth and oral soft tissue examination. Diffusion time- and spatially-resolved, polarization sensitive, optothermal, speckle, and OCT approaches are considered.

Fiber optic technology offers different advantages when applied for diagnosis in health care. This chapter provides an introduction to fiber optics and discusses different configurations and applications of fiber optic based, direct and indirect, diagnostic sensors. Relevant examples of fiber optic diagnostic sensors applied to dentistry are also presented.