T. Wallace MacFarlane

Chapter 9 – Fungal infections

Publisher Summary A variety of diseases that are caused by fungi might appear in the oral and perioral regions, either as localized lesions or as manifestations of systemic mycoses. However, candida infections of the oral cavity are the predominant group of fungal infections, which the dental practitioners frequently encounter; although rare mycoses, such as blastomycosis and mucormycosis might be seen, particularly in immunocompromised and sometimes in immigrant population groups. This chapter focuses on candida infections of the oral mucosa; it discusses the uncommon mycoses. A number of local and general predisposing factors play a contributory role in the pathogenesis of oral fungal infections. Debilitated individuals, such as those receiving antibiotics, steroid, or cytotoxic therapy, are particularly predisposed, as are patients with uncontrolled diabetes mellitus, other hormonal disorders such as hypoadrenocorticism, and haematogenous and malignant disorders. Certain age groups, especially the young and the old, and the pregnant are prone to oral yeast infections.

Chapter 3 – Oral ecosystem and dental plaque

Publisher Summary The human mouth is lined by a stratified squamous epithelium, which is modified in different areas according to function. The oral mucous membrane is interrupted by salivary ducts and by teeth, if present. The gingival tissues are bound to the tooth surface by the epithelial attachment, and crevicular fluid passes into the mouth from the gingival crevice. A thin layer of saliva bathes the surface of the mucosa and contained in this layer are epithelial squames, polymorphonuclear leucocytes, and members of the oral commensal microflora. However, within the general environment of the mouth, there exist a number of different microenvironments or niches, each of which supports its own peculiar microflora. The microbiological differences between some sites are qualitative and quantitative, while quantitative differences exist between other surfaces. These variations are because of the complex interactions of a wide range of ecological factors.

Chapter 5 – Microbiology of periodontal diseases

Publisher Summary Periodontal diseases occur in all parts of the world and few individuals live out their natural life span without becoming affected. However, in the majority of individuals, the common chronic inflammatory diseases which involve the gingival and periodontal tissues can be controlled, if not cured, using mechanical cleansing techniques and encouraging good oral hygiene. A small but significant number of patients experience rapidly progressive disease which requires assessment and treatment by periodontologists. While there is no doubt that microorganisms play an important role in the aetiology of most forms of periodontal disease, there is dispute as to whether their involvement is of a specific or non-specific nature. At present, clinical and radiological examination are unable to diagnose active disease or to predict which patients are likely to experience severe progressive periodontitis. Tissue destruction can be recorded with certainty only in a retrospective manner. Therefore, much of the current research in periodontology is directed towards developing laboratory tests which will allow high-risk patients and active disease to be identified early and ensure that subsequent specialized treatment is effective. An area of current interest is AIDS-related periodontal disease which is described in Chapter 16.

Microbiology in endodontic therapy

Publisher Summary The most common diseases that affect the dental pulp and periapical tissues are caused by bacteria. The sources and routes of infection that involve pulp and periapical tissues are: (1) carious dentine via dentinal tubules; (2) subgingival plaque bacteria present in deep periodontal pockets via lateral canals normally present in the apical two thirds of teeth; (3) from the oral environment secondary to tooth fracture or mechanical exposure; and (4) anachoresis—a mechanism whereby diseased tissue attracts bacteria present in bacteraemias. The clinical presentation and severity of these infections are related to the way in which the host defenses interact with the infective agents that are present in the pulp cavity. The initial defense mechanism of the pulp to infection is to prevent access of microorganisms to host tissues by depositing sclerotic or irregular secondary dentine in their pathway. Within the pulp, acute inflammation with phagocytosis might also occur, especially in the early stages of invasion, and later a chronic response might supervene with associated antibody-mediated immune reactions.

Chapter 15 – Viral hepatitis

Publisher Summary Viral hepatitis, common with acquired immune deficiency syndrome (AIDS), is one of the few blood-borne viral hazards that the dentist has to contend with in his practice. Although the AIDS epidemic has aroused the greatest concern regarding disease transmission, hepatitis B infection can be more dangerous to the patient and the dentist, because of the relatively high infectivity of hepatitis B virus compared with human immunodeficiency virus (HIV). Hepatitis A occurs in parts of the world where sewage disposal measures and food hygiene are unsatisfactory. Although the transmission of the virus might rarely occur via contaminated needles, it is usually contracted by the faecal-oral route through contaminated food and water. Hepatitis B virus is usually spread by the parenteral route rather than the faeco-oral route. Non-A non-B (NANB) hepatitis has also been recognized. This disease, sometimes called hepatitis C, occurs most commonly after blood transfusion and parenteral drug abuse. However, delta hepatitis is caused by a recently discovered “defective” RNA virus, which coexists with the hepatitis B virus.

Chapter 10 – Viral infections

Publisher Summary There are numerous species of viruses that are capable of infecting humans and the organisms are primarily classified according to the type of nucleic acid present in their genome, that is, DNA or RNA viruses. However, other features such as the arrangement of the protein subunits surrounding the nuclear material, the size of the virion and whether the virion is naked or enveloped are useful in subdividing and speciating the viruses. Certain species of viruses show affinity for specific mammalian cells. This phenomenon, known as tissue tropism, is exemplified by herpes and hepatitis viruses, which replicate in epithelial cells and hepatocytes, respectively. Viruses that show tropism for oral and facial skin epithelium and elicit clinical manifestations in these regions include herpes simplex virus (I and II), varicella zoster virus and the Coxsackie viruses. All of these viruses share a common feature by producing vesiculoulcerative lesions in the oral and perioral regions, accompanied by lymphadenopathy. The papovavirus also infects oral epithelium but it produces papillary rather than vesiculobullous lesions. Cytomegalovirus and mumps virus demonstrate tropism for salivary gland tissue with sialadenopathy as the major clinical finding.

Chapter 8 – Bacterial infections

Publisher Summary Specific bacterial infections of the mouth are uncommon, with tonsillitis in children caused by Strep. pyogenes being the most common. Other bacterial causes of pharyngitis that are rarely diagnosed include C. diphtheriae and the fusospirochaetal complex associated with Vincents angina. Specific infections of the oral mucosa that are rare, and are usually manifestations of systemic infections, include diseases such as tuberculosis, syphilis, and gonorrhea. Sore throat is a common symptom of a number of specific infections and is accompanied by a variable degree of constitutional upset. Gonorrhea is a venereal infection with a worldwide distribution that has reached epidemic proportions in some countries. Although, at present, syphilis is not encountered frequently, it is an important disease with a variety of oral manifestations. Human-type and bovine-type tuberculosis are caused in man by Mycobacterium tuberculosis and Mycobacterium bovis, respectively. Other opportunist mycobacteria might also cause human infections. Leprosy is caused by an acid-alcohol-fast bacillus, Mycobacterium leprae, which in general prefers to grow near the cooler body surfaces of man. Tetanus is caused by a strictly anaerobic spore-bearing Gram-positive bacillus, Clostridium tetani.

Chapter 11 – Salivary gland infections

Publisher Summary Salivary gland infections are not uncommon. The most frequently encountered infection of the salivary glands is caused by the mumps virus. However, a number of other agents, particularly bacteria, are responsible for acute sialadenitis. The parotid glands are more commonly infected than the submandibular salivary glands and most reports deal with bacterial parotitis, although the submandibular glands might be similarly affected. Infections of the accessory salivary gland can occur but are rare. Apart from mumps, the majority of salivary gland infections are seen in adults. However, there are two rather ill-defined clinical entities termed “neonatal suppurative parotitis” and “recurrent parotitis of childhood” that are confined to the first decade of life. As in other infectious diseases, initiation and progression of salivary gland infections would appear to depend on the host resistance to infection and the virulence of the causative organism. The decrease in host resistance in the present context could be either because of general factors such as debility and dehydration or local factors including sialolithiasis, ductal strictures, and salivary gland pathology.

Chapter 6 – Dentoalveolar infections

Publisher Summary Pus-producing or pyogenic infections which are associated with a tooth and surrounding supporting structures, such as the periodontal membrane, cementum and alveolar bone, have been described using a number of terms such as periapical abscess, apical abscess, chronic periapical dental infection, dental pyogenic infection, periapical periodontitis, and dentoalveolar abscess. In this chapter the last term will be used. The clinical presentation is variable and is related to the interaction of a number of factors such as the virulence of the causative microorganisms, the state of the local and systemic defence mechanisms of the host and a number of anatomical features. Depending on how these factors interact, the resulting infection may present as an abscess localized to the tooth which initiated the infection, as a diffuse cellulitis which spreads along fascial planes, or a mixture of both. The primary source of microorganisms in these infections is either from the apex of a necrotic tooth or from periodontal pockets. Usually the source of infection in the periapical region is from dental caries via the pulp chamber and root canal.

Chaptet 16 – Human immunodeficiency virus and acquired immune deficiency syndrome

Publisher Summary Infection with human immunodeficiency virus (HIV) is probably the most lethal infection which can be contracted via parenteral routes. This is because the scientific community has not yet developed an antiviral agent or a vaccine which successfully combats the virus. Although the theoretical possibility of contracting hepatitis B in the dental clinic is far greater than that of acquired immune deficiency syndrome (AIDS), this is counterbalanced by the very high mortality and, indeed, the stigma and social consequences associated with the latter. These, together with the extensive media coverage and intense public awareness of AIDS, mean that the average patient would probably be more concerned about contracting AIDS than hepatitis B. Therefore, the dental practitioner should be knowledgeable on AIDS, firstly to diagnose patients who may present to him with early signs and symptoms of the disease, secondly to implement appropriate infection control measures and finally to educate, advise and allay the public fears concerning AIDS transmission both within and outwith the dental clinic environment.