Plaque

A seminar on

ORAL BIOFILM

           
Introduction
Colonization of oral cavity begins within hours after birth. From an ecologic view point, the oropharynx is considered an open growth system. A dynamic equilibrium exists between the adhesion forces of micro organisms and a variety of removal forces originating from-swallowing, mastication and blowing of nose; wash out effect of salivary, nasal and crevicular fluid out flow; tongue and oral hygiene implements; active motion of ciliae. Most organisms can survive only when they adhere to either soft tissues or hard surfaces in teeth, denture or implants. The high turn-over rate of intra-oral epithelial cells,especially gingiva, prevents permanent accumulation of large masses of microorganisms on these surfaces. This is a natural cleansing mechanism.
Structure and composition of dental plaque
Dental plaque is defined clinically as a structured, resilient, yellow-grayish substance that adheres tenaciously to intra-oral hard surfaces, including removable and fixed restorations. Plaque is primarily composed of bacteria in a matrix of salivary glycoproteins and extra cellular polysaccharides. This matrix makes it impossible to remove the plaque by rinsing or use of sprays.
Materia alba refers to soft accumulations of bacteria and tissue cells that lack the organized structure of dental plaque, and is easily displaced with a water spray. Calculus is hard deposit that forms by mineralization of dental plaque, and it is generally covered by a layer of unmineralized plaque.
Dental plaque is composed primarily of microorganism. One gram of plaque (net weight) contains approximately 1011 bacteria. Non bacterial micro-organisms include mycoplasma species, yeasts, protozoa and virus. The microorganisms exist within an inter-cellular matrix that also contains a few host cells, such as epithelial cells, macrophages and leukocytes. The material among bacteria in dental plaque is termed intercellular matrix. It...