Novel Microscopic Methods to Study the Structure and Metabolism of Oral Biofilms

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Abstract
INTRODUCTION Uniquely in the human body, the tooth surface provides a non-shedding surface for microbial attachment. As a result, large numbers of microorganisms accumulate, together with their metabolic products, to form dental plaque, especially at occluded sites. Dental plaque was the first biofilm described by van Leeuwenhoek (1683), who noted the unusual resistance of the ‘animalcules’ he observed to treatment with vinegar (McHugh, 1999). Since this time, dental plaque has probably been the most studied of biofilms, with some justification: dental plaque is the most accessible of human-associated biofilms and is responsible for the most common diseases affecting man in the developed world – dental caries and periodontal diseases. This chapter provides a brief historical view of light and electron microscopic studies of dental plaque. The major focus of the chapter is then to describe how novel microscopic approaches are providing new insights into the structure and metabolic activities of dental plaque biofilms. LIGHT AND ELECTRON MICROSCOPIC STUDIES OF DENTAL PLAQUE DEVELOPMENT Since van Leewenhoek's time, vast numbers of light microscopic studies (especially of dental plaque) have examined the structure of biofilms. Furthermore, the development of electron microscopy (EM) began to unearth the diversity within, and structures of, developing dental plaque (Saxton, 1973; Listgarten, 1976, 1999). The development of dental plaque can be divided into several arbitrary stages. Pellicle formation occurs almost instantaneously on a cleaned tooth surface (Figure 8.1a). After a cleaned tooth surface has been exposed for 4 hours to the oral environment, relatively few bacteria are found.