Plaque

Dental plaque is a sticky film, made up of microorganisms, that clings to and grows on surfaces in the mouth. It can be found on all the surfaces of the teeth both above and below the gumline, as well as on dental restorations, prosthetic devices, and orthodontic appliances, and is one of the most significant causes of gum disease and tooth decay; its regular removal is one of the most important steps in reducing the likelihood of these common diseases. The microorganisms found in dental plaque include bacteria as well as fungi, and the composition of dental plaque differs depending on where in the mouth it is located. When dental plaque remains on the teeth for a prolonged period, the moisture in the film dries up and leaves behind a calcified precipitate known as dental calculus, or tartar. Once dental plaque has hardened and become calculus, it cannot be removed safely with traditional home hygiene tools and must be removed professionally. Because dental calculus creates a rough, pocketed surface on the teeth, it encourages the proliferation of additional dental plaque, which can dry in layers on top of existing calculus and create a cycle of bacterial invasion that encourages disease.

Dental plaque begins with a layer of saliva called an acquired pellicle. The acquired pellicle begins forming almost immediately after the teeth are cleaned, or immediately upon the eruption of a new tooth. Bacteria cling to the pellicle layer and form colonies that mature on the teeth, spreading throughout the oral cavity and multiplying. If left intact, each of these colonies develop complex metabolic advantages that are specifically intended to increase their survival under conditions specific to their location in the mouth.

Almost 90% of bacterial plaque, by weight, is made of water. Otherwise, the primary component of plaque is bacteria, and the remaining proportion is microscopic debris from food and beverages. The majority of bacteria in plaque is a strain of the Streptococcus bacteria. On their own, these bacteria are harmless; when allowed to colonize and proliferate, however, they can wreak havoc on the tissues of the oral cavity. When these bacteria ferment sucrose that enters the oral cavity, they begin to produce acids that upset the equilibrium of the oral microbiome and continue to mutate and mature. While the Streptococcus bacteria is often present when dental plaque is first forming, more than 1,000 different species of bacteria have been found in dental plaque upon clinical examination. Streptococcus is considered an early colonizer, but, as these later colonizers develop, they encourage the growth of different types of late colonizers, increasing the complexity of the composition of the dental plaque biofilm. Dental plaque that forms above the gumline, which is known as supragingival plaque biofilm, is made up primarily of aerobic bacteria that need oxygen to survive. Plaque that develops below the gumline, or subgingival plaque biofilm, forms as supragingival plaque proliferates and is made up primarily of anaerobic bacteria, allowing this film to thrive in the oxygen-depleted environment that exists in the small crevices between the gums and the teeth. Toxins emitted by these different bacteria may be more acidic, which helps them contribute to tooth decay, or they may be more alkaline, which helps them contribute to gum disease. Because of the complexity and sheer destructive potential of dental plaque, proper oral hygiene, which is intended to reduce or remove dental plaque early in its life cycle, is an integral part of the prevention and management of the diseases of the oral cavity.