Dental plaque
Dental plaque is a biofilm of microorganisms that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar, it is often brown or pale yellow. It is commonly found between the teeth, on the front of teeth, behind teeth, on chewing surfaces, along the gumline, or below the gumline cervical margins. Dental plaque is also known as microbial plaque, oral biofilm, dental biofilm, dental plaque biofilm, and bacterial plaque biofilm. Bacterial plaque is one of the major causes for dental decay and gum disease. It has been observed that differences in the composition of dental plaque microbiota exist between men and women, particularly in the presence of periodontitis.
Progression and build-up of dental plaque can give rise to tooth decay, and periodontal problems. Hence it is important to disrupt the mass of bacteria and remove it. Tooth decay is the localized destruction of the tissues of the tooth by acid produced from the bacterial degradation of fermentable sugar. Common periodontal problems include gingivitis and periodontitis. Plaque control and removal can be achieved with correct daily or twice-daily tooth brushing and use of interdental aids such as dental floss and interdental brushes.
Oral hygiene is important as dental biofilms may become acidic causing demineralization of the teeth or harden into dental calculus. Calculus cannot be removed through tooth brushing or with interdental aids, but only through professional cleaning.
Plaque formation
Dental plaque is a biofilm that attaches to tooth surfaces, restorations, and prosthetic appliances if it is left untreated. Understanding the formation, composition, and characteristics of plaque helps with controlling the build up. An acquired pellicle is a layer of saliva that is composed of mainly glycoproteins and forms shortly after cleaning of the teeth or exposure of new teeth. Bacteria then attach to the pellicle layer, form micro-colonies, and mature on the tooth. This will then result in oral diseases.Steps of plaque formation
; 1. Association: Dental pellicle forms on the tooth, and provides bacteria surface to attach.; 2. Adhesion: Within hours, bacteria loosely binds to the pellicle.
; 3. Proliferation: Bacteria spreads throughout the mouth and begins to multiply.
; 4. Microcolonies: Microcolonies are formed. Streptococci secrete protective layer.
; 5. Biofilm formation: Microcolonies form complex groups with metabolic advantage.
; 6. Growth or maturation: The biofilm develops a primitive circulatory system.
Components of plaque
Different types of bacteria are normally present in the mouth. These bacteria, as well as leukocytes, neutrophils, macrophages, and lymphocytes, are part of the normal oral cavity and contribute to the individual's health. Approximately 80–90% of the weight of plaque is water. While 70% of the dry weight is bacteria, the remaining 30% consists of polysaccharides and glycoproteins.Bacteria
The bulk of the microorganisms that form the biofilm are Streptococcus mutans and other anaerobes. However, the precise composition varies by location in the mouth. Examples of such anaerobes include fusobacterium and actinobacteria. S. mutans and other anaerobes are the initial colonizers of the tooth surface, and play a major role in the establishment of the early biofilm community. Streptococcus mutans uses the enzyme glucansucrase to convert sucrose into a sticky, extracellular, dextran-based polysaccharide that allows the bacteria to cohere, forming plaque. Sucrose is the only sugar that bacteria can use to form this sticky polysaccharide. These microorganisms all occur naturally in the oral cavity and are normally harmless. However, failure to remove plaque by regular tooth-brushing allows them to proliferate unchecked and build up in a thick layer, which can cause various dental diseases for the host. Those microorganisms nearest the tooth surface typically obtain energy by fermenting dietary sucrose, and during fermentation they begin to produce acids.The bacterial equilibrium position varies at different stages of formation. Below is a summary of the bacteria that may be present during the phases of plaque maturation:
- Early biofilm: primarily Gram-positive cocci
- Older biofilm : increased numbers of filaments and fusiforms
- 4–9 days undisturbed: more complex flora with rods, filamentous forms
- 7–14 days: Vibrio species, spirochetes, more Gram-negative organisms
Dental plaque as a biofilm
A clean tooth surface would immediately be colonized by salivary pellicles, which acts as an adhesive. This allows the first bacteria to attach to the tooth, colonize, and grow. After some growth of early colonizers, the biofilm becomes more compliant to other species of bacteria, known as late colonizers.
Early colonisers
Source:- mainly Streptococcus species
- Eikenella spp.
- Haemophilus spp.
- Prevotella spp.
- Propionibacterium spp.
- Capnocytophaga spp.
- Veillonella spp.
Late colonisers
- Aggregatibacter actinomycetemcomitans
- Prevotella intermedia
- Eubacterium spp.
- Treponema spp.
- Porphyromonas gingivalis
Some salivary components are crucial for the plaque's ecosystem, such as salivary alpha-amylase which plays a role in binding and adhesion. Proline-rich proteins and statherins are also involved in the formation of plaque.
Supragingival biofilm
Supragingival biofilm is dental plaque that forms above the gums, and is the first kind of plaque to form after brushing your teeth. It commonly forms in between the teeth, in the pits and grooves of the teeth, and along the gums. It is made up of mostly aerobic bacteria, meaning these bacteria need oxygen to survive. If plaque remains on the tooth for a long period of time, anaerobic bacteria begin to grow.Subgingival biofilm
Subgingival biofilm is plaque that is located under the gums. It occurs after the formation of the supragingival biofilm by a downward growth of the bacteria from above the gums to below. This plaque is mostly made up of anaerobic bacteria, meaning that these bacteria will only survive if there is no oxygen. As this plaque attaches in a pocket under the gums, they are not exposed to oxygen in the mouth and will thrive if not removed.The extracellular matrix contains proteins, long-chain polysaccharides and lipids.
The most common reasons for ecosystem disruption are the ecological factors discussed in the [|environment] section. The bacteria that exhibit the most fit plasticity for the change in environment dominate it. Often, this leads to opportunistic pathogens which may cause dental caries and periodontal disease. Pathogenic bacteria that have the potential to cause dental caries flourish in acidic environments; those that have the potential to cause periodontal disease flourish in a slightly alkaline environment.
Antibodies to the oral pathogens Campylobacter rectus, Veillonella parvula, and Prevotella melaninogenica are associated with hypertension.