Publisher Summary
Clinical oral microbiology is the study of the specimens that are taken from patients who are suspected of having infections of the mouth and surrounding tissues. The purpose of studying such samples is to obtain the information that would assist the clinician in arriving at a definitive diagnosis and in giving advice about the management of the patient, especially concerning antimicrobial therapy. The more common oral and dental infections, such as caries and periodontal diseases, are different from almost all infections in other parts of the body. In medical microbiology, infections are exogenous and caused by a single pathogenic species, whereas endogenous polymicrobial infections are more common in the mouth. Therefore, in the investigation of many oral and dental infections, it is necessary to assess qualitative and quantitative changes in the normal oral microflora, instead of screening for a single non-commensal pathogen, as occurs in the majority of medical investigations.
Clinical oral microbiology is the study of specimens taken from patients suspected of having infections of the mouth and surrounding tissues. The main purpose of studying such samples is to obtain information which will assist the clinician in arriving at a definitive diagnosis and in giving advice about the management of the patient, especially concerning antimicrobial therapy.
Since many dentists learn about the principles of microbiology during their medical microbiology course, it is important to emphasize that the more common oral and dental infections, e.g. caries and periodontal diseases, are different from almost all infections in other parts of the body. In medical microbiology, infections are often exogenous and caused by a single pathogenic species, whereas endogenous polymicrobial infections are more common in the mouth. As a result, in the investigation of many oral and dental infections, it is necessary to assess both qualitative and quantitative changes in the normal oral microflora, instead of screening for a single non-commensal pathogen, as occurs in the majority of medical investigations.
Microbial infections of the oral and dental tissues are caused by four main groups of microorganisms. Firstly, there are non-specific localized infections caused by bacteria normally found in the mouth, i.e. commensal bacteria, usually in mixed but occasionally in pure culture. It is a characteristic of this group of diseases that they are not usually attributable to any single specific pathogenic agent but are due to the combined activity of a small number of different microbial species, not always the same in every case. Examples of these endogenous infections are dental caries, periodontal diseases, and dentoalveolar infections. The second group of localized infections are caused by specific microorganisms normally present in the oral flora. Examples of these are actinomycosis and candidosis. Thirdly, there are specific systemic infections with associated oral manifestations caused by microorganisms which are not normally present in the oral flora. Examples include bacterial infections, e.g. syphilis, gonorrhoea, tuberculosis, and also a number of viral infections, e.g. herpetic stomatitis, mumps, chickenpox, shingles and herpangina. Fourthly, there are systemic infections without oral symptoms but caused by microorganisms which are members of the oral flora, e.g. infective endocarditis caused by various oral streptococci. Finally, there are a number of systemic infections which have few oral or dental manifestations but, due to the possible risk of cross-infection which may occur during dental treatment, require to be studied by dentists: such infections include hepatitis B and acquired immune deficiency syndrome (AIDS).
A dentist should be able to diagnose, treat or prevent most of the above endogenous infections, as well as some of the exogenous diseases. In addition, he should be competent to assess the possible risks of cross-infection associated with treating a patient infected with a range of specific pathogens. This can be best achieved if the dentist fully understands hostâparasite interactions, i.e. the mechanisms whereby microorganisms are transmitted from one patient to another, the way in which they invade the host tissues and cause tissue destruction, and how the host tissues in turn resist the attack of the microorganisms. It is not necessary for the dentist to know in detail the anatomy, physiology or biochemistry of the microorganisms involved in all oral infections, nor to remember precise details of how they are isolated and identified, although he should possess some information of a general nature about these subjects. The dental clinician requires a sound knowledge of the samples required to diagnose oral infections and how to transport these specimens to the laboratory. In addition, he should appreciate the rationale behind the laboratory tests which are used to assess the sensitivity of microorganisms to antibiotics and the clinical significance of these results. Finally, clinicians should be familiar with the concepts of sterility and disinfection and have a good working knowledge of the methods of sterilization of dental instruments and prevention of cross-infection in the dental surgery.
The aim of this book is to give a clear, concise and up-to-date account of the clinical aspects of oral microbiology and it has been assumed that readers will have a reasonable understanding of the principles of microbiology. The book is intended primarily for dental undergraduate students, although it may be useful to dental postgraduate students, as well as general dental practitioners who wish to update or extend their knowledge of oral microbiology. There are a number of areas in the microbiology of the mouth for which complex and often conflicting data are available. When such a problem has been encountered, we have presented a simplified and personal view which inevitably will not be acceptable to all microbiologists.
Oral microbiology has usually been taught as a preclinical or paraclinical offshoot of general or medical microbiology. This approach is not ideal for undergraduate dental students as they have often had difficulty in integrating this knowledge into the various clinical dentistry specialities which are taught in succeeding years. Therefore, we have attempted to follow a more integrated approach to teaching oral microbiology throughout the book and this is particularly reflected in the broad categorization of the text into five major sections, i.e. oral ecology, diseases related to dental plaque, infections of oral and perioral tissues, diagnostic oral microbiology and cross-infection in dentistry. It is hoped that this framework will enable the reader to obtain a clear, overall picture of the subject. While the general contents of the book should help the novice as well as the postgraduate to expand his knowledge of oral microbiology, some sections, such as diagnostic oral microbiology and cross-infection in dentistry, should have particular appeal to the busy general dental practitioner who wishes to use the text as a quick reference manual.