PERIODONTAL DISEASES - PLAQUE, CALCULUS AND REGRESSIVE CHANGES (Page 1 of 4)

Plaque ( Figs 18-1) Plaque is composed of bacteria and a matrix that adheres to the outer tooth surface. The development of plaque is a stepwise process that has been well characterized. The first step is the attachment of the acquired pellicle, a thin film of salivary proteins. Within a few days, gram-positve facultative cocci overlay the pellicle and colonize the tooth surface. Additonal bacterial types such as Veillonella species, a gram-negative anaerobe, Actinomyces, gram positive rod, and Capnocytophaga gram negative rod enter the region and contribute to early-colonization of plaque. Prevotella intermedia and filamentous fusobacterium species colonize the plaque between the first week and third weeks as an anaerobic environment becomes established. Late colonization with porphyromonas gingivalis, motile rods and Treponema species (spirochetes) occurs during and after the third week, if the plaque grows undisturbed. The exact composition of the microbial population within plaque varies based on site, available substrate, salivary components (adhesins and secretory immunoglobulin [sIgA]), duration and oral hygiene practices of the patient.

Plaque is white and soft, and composed not just of bacteria. It also is composed of an extracellular matrix. The matrix is a "glucan", a sticky substance secreted by streptococci that promotes adherence of the bacteria to the pellicle. This stickiness is apparent when trying to remove plaque from teeth.

Supragingival plaque is bacteria adherent above the gingiva, whereas bacteria below the gingiva is called subgingival plaque. Growth in supragingival plaque mass results from nutrients obtained from ingested simple carbohydrates (glucose), lactic acid and other plaque components. Subgingival (plaque) bacteria preferentially uses metabolized peptides and amino acids over glucose that are obtained from tissue breakdown products, the ginvival crevicular fluid and interbacterial feeding. Inflammed gingival tissues produce more gingival crevicular fluid which favors the proliferation of subgingival bacterial replication. Subgingival bacterial populations prefer a no oxygen (anaerobic) environment, whereas supragingival bacterial populations prefer a low oxygen environment, and are called facultative anaerobes. Long-standing plaque is mostly composed of gram-negative anaerobes.

The persistence of microbial plaque can lead to the development of caries, gingivitis, calculus formation, gingival recession, and various manifestations and types of periodontitis.

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