Epidemiology And Clinical Relevance

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Orofacial and odontogenic infections are diverse in etiology and clinical presentation. Elderly patients are particularly at risk because of poor oral health and relatively high prevalence of dental caries and periodontal disease. Such infections in the elderly may be localized and indolent, or invasive and life-threatening. Patients with systemic underlying diseases such as diabetes mellitus are also prone to more serious infections. The increasing need for valvular and joint replacements in the elderly also exposes this population to a greater risk for serious complications such as infective endocarditis or prosthetic infections from hematogenous seeding of odontogenic infections (1).

Virtually all infectious agents can present intraorally. Although bacterial and fungal infections of the oral mucosa usually result from direct inoculation of opportunistic pathogens from the external or resident microflora, viral infections of the oral mucosa generally arise by hematogenous dissemination or reactivation of a latent infection. Due to physiologic changes, such as blunted fever responses, chronic or coexisting diseases, and a tendency to underreport symptoms, the clinical presentation of odontogenic infections in the elderly may be atypical, and the diagnosis or severity of infection may be unrecognized or underestimated (2).

1.1. Prevalence of Dental Caries and Periodontal Disease in the Elderly

A survey among adults and senior citizens in the United States revealed that the fraction of individuals aged 65 yr or older who retained some or all of their natural teeth had risen from 40% in 1957 to 60% in 1986 and 72% in 1991 (3,4). These surveys document the notion that edentulism is no longer the norm in the aging population, and that oral health and dental care (including the appropriate diagnosis, management, and prevention of odontogenic infections) is an increasingly important issue in geriatric medicine.

In the 1988-1991 national survey, the prevalence of dental caries, particularly on root surfaces of the affected teeth, increased dramatically with age, from 47% in those 65-75 yr old to 56% in those 75 yr of age or older (5). Diseases of the periodontium are also extremely common in the elderly. In the same survey, 46% of individuals 65 yr or older suffered moderately severe gingival recession (more than 3 mm), and over 80 % experienced modest periodontal attachment loss (at least 3 mm) (6).

From: Infectious Disease in the Aging Edited by: Thomas T. Yoshikawa and Dean C. Norman © Humana Press Inc., Totowa, NJ

Longitudinal studies of oral health in the aging person are generally rare. Nordstrom and colleagues (7) conducted a 9-yr longitudinal study of dental and periodontal status in 70- and 79-yr-old city cohorts in northern Sweden. The frequency of reported annual dental visits increased in the younger but not in the older cohort during the 9-yr period. Clinical examination showed an increasing prevalence of tooth loss, root caries, and periodontal disease with advancing age. Among dentulous persons, 1.7 teeth per subject were lost from 1981 to 1990 in the younger cohort, compared with 2.6 teeth per subject in the older cohort. The number of good teeth decreased very little in the younger cohort (from 3.44-3.34) but did decrease more dramatically in the older cohort (from 3.47-2.65) during the 9-yr period. The frequency of surfaces with periodontal attachment loss exceeding 3 mm increased statistically from 1981-1990 in the older cohort. In general, subjects with annual dental visits had fewer oral problems.

The oral health of elderly patients in long-term care facilities was investigated during 1993 among 250 residents in a suburban community in Norway (8). Results were compared with an identical examination of the residents in the same facilities in 1980. In general, the oral hygiene was poor. The mean number of remaining teeth per person was 11.7 (confidence interval [CI], 10.3-13.1). The mean number of filled teeth was (5.1 CI, 4.1-6.0), and the mean number of decayed teeth was 1.8 (CI, 1.4-2.2). The mean number of residual roots per person was 0.8 (CI, 0.5-1.1). Periodontal pockets exceeding 4 mm were observed in 5% of all teeth. Edentulousness had decreased from 80% in 1980 to 54% in 1993, and more remaining and filled teeth and fewer residual roots per person were observed in the 1993 population. These data underscore the need for resources to prevent periodontal disease and caries among elderly patients in long-term care facilities.

1.2. Microbial Etiology of Dental Caries and Periodontal Disease

Dental caries are caused by a variety of oral bacteria, particularly Streptococcus mutans and Lactobacillus spp., which colonize the tooth surface as a dental plaque (9). The ingestion of carbohydrates, especially monosaccharides and disaccharides, results in the generation of acids on the tooth surface by these plaque bacteria, causing dem-ineralization of the protective enamel coating and subsequent tooth decay. The tooth has at least three intrinsic mechanisms protecting it from carious decay: (1) constant flow of saliva of neutral pH that buffers and washes away bacterial acids, and supplies calcium and phosphate to remineralize and repair damaged tooth surfaces; (2) acquisition of an acellular, structureless, bacteria-free coating of salivary origin, known as the acquired pellicle, which acts as a surface barrier to dietary and bacterial damage; and (3) cleansing action of the tongue and buccal membranes that actively removes food particles from the proximity of the tooth. The saliva and its various constituents, such as lactoferrin, lysozyme, lactoperoxidase, P-lysin, and immunoglobulins, also possess important antimicrobial activity against dental plaque-associated bacteria. As well, the act of tooth brushing and flossing serves to remove food particles and bacterial plaques adherent to the tooth surface. However, with aging and poor dental hygiene, the acquired pellicle becomes colonized with bacteria, and is replaced by supragingival and subgingival bacterial plaques that ultimately progress to dental caries.

Unlike dental caries, diet does not appear to have a significant role in the pathogenesis of periodontal disease. Factors most commonly associated with gingivitis are inadequate oral hygiene and development of the supragingival or subgingival dental plaque. Plaques that accumulate above the gingival margin are composed mainly of Grampositive facultative and microaerophilic cocci and bacilli; plaques that accumulate below the gingival margin are composed mainly of Gram-negative anaerobic bacilli and motile forms including spirochetes. Periodontal disease is mainly caused by microorganisms within the subgingival dental plaque, which penetrate the gingival epithelium and elicit an inflammatory host response. This ultimately results in destruction of the periodontium comprising the alveolar bone surrounding the root of the tooth, the periodontal membrane, and the gingiva (10). This tissue destruction causes an apical migration of gingival tissues (gingival recession), loss of periodontal attachment, and an increase in the depth of the gingival crevice (periodontal pocket formation). The microflora associated with gingivitis is predominated by Actinomyces viscosus and Bacteroides gingivalis, whereas those closely associated with advanced periodontitis include Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, and B. forsythus (11). A unifying hypothesis postulating the microbial shift from a plaque-free tooth surface and progression to supragingival and subgingival plaque organisms and various odontogenic infections is shown in Fig. 1.

1.3. Factors Predisposing to Orofacial and Odontogenic Infections in the Elderly

Several factors in the elderly may predispose to the development of dental caries and periodontal disease. These include difficulty in performing oral hygiene due to impaired manual dexterity or physical disability, inadequate fluoride exposure, frequent sugar consumption, gingival recession, and reduced sensory or motor function in the oral cavity and around the teeth (12). Although individuals of all ages are susceptible to the development of dental plaque if daily oral care is withheld, older persons form dental plaques more rapidly than do younger people. Gingival recession, which is both common and more severe with advancing age, also renders the elderly more susceptible to the development of root caries by exposing the underlying tooth surfaces to subgingival dental plaques without the protection from enamel covers. Chronic medical illness, physical disability, and socioeconomic factors may also limit access to appropriate dental care in the elderly, either due to immobility, cost of transportation and treatment, or long-term care institutionalization (13).

Salivary gland hypofunction with diminished salivary flow and the development of xerostomia, is an important contributor to poor oral hygiene in the elderly that ultimately leads to both dental caries and periodontal disease. Without an adequate volume or normal composition of saliva, chewing and swallowing becomes more difficult, and repeated irritation of the gingiva and other soft tissues results in gingivitis, mucositis, aphthous ulcers, and an increased rate of tooth decay. It is important to note that aging per se does not appear to lead to salivary hypofunction, and in healthy older adults there is no significant alteration either in the volume or composition of saliva produced (13,14). The frequent finding of decreased salivary output and xerostomia is most likely caused by systemic diseases and their treatments rather than by the normal

Fig. 1. Microbial etiology of odontogenic infections. A unifying hypothesis postulating the microbial shift from a plaque-free tooth surface and progression to supragingival and subgingival plaque organisms and various odontogenic infections. Modified with permission from ref. 24.

biologic sequelae of aging. For example, agents used to manage urinary incontinence, hypertension, depression, and other major medical problems in the elderly, particularly anticholinergic drugs, are especially common causes of xerostomia (15). In addition, several classes of medications frequently prescribed to older people, such as calcium channel blockers (e.g., diltiazem, verapamil, nifedipine), anticonvulsants (e.g., phenytoin), and immunosuppressants (e.g., cyclosporin), are associated with the development of gingival hyperplasia. If left untreated, this can also predispose to both dental caries and destructive periodontitis (12).

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