Plaque Health Article

PLAQUE

Dental plaque is a biofilm that forms naturally on the tooth surface. It consists of a diverse microbial community embedded in a polymer matrix of bacterial and salivary origin. Because environmental conditions vary from place to place within the oral cavity, each tooth site with plaque represents its own distinct ecosystem, and the dominant microbial composition at each site depends on the outcome of numerous host-microbe and microbemicrobe interactions. Initial bacterial colonizers quickly become established on a clean tooth surface, and a pattern of subsequent bacterial succession has been identified. If left undisturbed, plaque reaches a maximum bulk after about seven days. Plaque deposition begins supragingivally—on the visible part of the tooth above the gum line—and if left undisturbed can progress subgingivally—into the crevice between the gum and the tooth. Microbial interactions usually keep the bacterial composition of plaque fairly stable, but when this homeostasis breaks down, the shifts in microbial balance can trigger the initiation of dental caries (tooth decay) or gingivitis (gum inflammation). Few bacteria can be isolated from around healthy gum tissue, although with gingivitis there is a considerable increase in the number and complexity of bacteria as the lesion develops. Subgingival plaque, if left undisturbed, can become a calcified matrix (calculus, or tartar) that can harbor harmful bacteria. Not surprisingly, subgingival calculus is closely associated with periodontal diseases. Specifically, Porphyromonas gingivalis and Bacteroides forsythus in subgingival plaque had been associated with both periodontal inflammation and bone loss.

Although dental plaque is commonly depicted in commercial advertising as the cause of both caries and periodontitis, dental plaque also benefits the host by helping to prevent intra-oral colonization by exogenous species. Plaque is also a repository for fluoride and other minerals that serve both to inhibit the demineralization of dental enamel—the first step in the development of a cavity—and to promote remineralization of early lesions. The fact that caries is initiated by a drop in plaque pH, following the fermentation of simple carbohydrates by certain bacteria resident in plaque, further exemplifies plaque's delicate ecology. Controlled plaque is beneficial, uncontrolled plaque can be harmful.

Prevention of plaque-related disease is geared toward plaque control rather than eradication. The goal in preventing periodontitis (diseases of the supporting structures of the tooth) is to prevent fresh plaque from becoming established enough to permit the growth of pathogenic bacteria. This goal is best achieved by thorough toothbrushing at least once per day with a fluoridecontaining toothpaste, plus consistent professional prophylactic care. So long as plaque remains supragingival, it can be controlled by mechanical or chemotherapeutic means. Once plaque becomes established subgingivally, however, an individual cannot remove it and professional intervention is necessary. Carrying out personal oral hygiene with a fluoride-containing toothpaste helps maintain high fluoride levels in plaque and thus inhibits the development of caries.

BRIAN A. BURT

(SEE ALSO: Caries Prevention; Gingivitis; Oral Health; Primary Prevention)