Plaque Flashcards
Types of tooth deposits
- acquired pellicle
- dental plaque biofilm
- mature plaque / materia Alba
- food debris
- supra gingival calculus
- subgingival calculus
- staining
Acquired pellicle
Organic, tenacious(adherent) , membranous, amorphous microscopic layer which forms over exposed teeth surfaces as well as restorations, calculus etc.
Very thin , 0.1-0.8 microns
Forms very shortly after removal , removed by tooth brushing but reforms within minutes.
Becomes colonised very quickly by microorganisms ( 1st stage plaque development). Formed from glycoproteins of saliva supragingivally and from crevicular fluid subgingivally. Unstained pellicle is clear and translucent. If stained with a disclosing agent will take up a very slight/pale stain.
Possible for pellicle to take up extrinsic stain from another source eg smoking or red wine it may appear grey or pink.
ROLE:
Form layer of protection against acids. It is one mode of attachment of dental calculus to the tooth surface. Most significantly it is considered the very first stage of plaque development as it serves as a layer for the deposition and colonisation of bacteria.
Plaque ( basic points )
- 80% water. Adherent enough to avoid removal ie by 3 in 1. This is due to presence of certain carbohydrates which create a sticky substance.
- micro organisms in plaque play an important role in both periodontal diseases and caries.
- plaque classified according to its location on the tooth so either supra or sub gingival.
- formation begins at the gingival margin area like particularly on interdental surfaces but increases rapidly if left undisturbed moving on towards gingival and middle third of teeth.
- more rapid deposition on rough and difficult to clean areas. Examples include:
Restoration over hangs, appliances, gingival hyperplasia , crowns, bridges, partial bridges, overcrowding, partially erupted tooth, periodontal pockets , pits and fissures, calculus.
Formation of plaque
3 basic steps: pellicle formation , bacterial colonisation and plaque maturation. These can be subdivided into 5 stages.
- Pellicle formation- forms within minutes. Salivary glycoproteins are absorbed onto dental enamel to form pellicle.
- Bacteria attach to pellicle - initial attachment of bacteria to the pellicle is by selective absorption of specific bacteria from oral environment. Innate characteristics of the bacteria and the pellicle determine the adhesive interactions which make a particular bacteria attach to a particular pellicle.
- Bacterial multiplication- micro colonies form as the bacteria multiply and grow. With increased size of these colonies they eventually meet and join up, known as coalescing. This results in continuous bacterial mass.
- Plaque growth and Maturation - the increase in the mass and thickness of plaque results from continued bacterial multiplication plus continuous absorption of new/ different bacteria to the layer.
- The antimicrobial substance is derived from salivary products , crevicular products and more significantly polysaccharides eg GLUCANS, DEXTRANS, FRUCTANS. These polysaccharides produced / synthesised from refined carbohydrates that are taken in the diet by bacteria present in plaque. They are very sticky and contribute to adhesion of the plaque to the tooth and the aggregation of the bacteria and provide a much thicker , adherent plaque layer.
Terminology of bacteria
AEROBE - a bacteria that can live and grow only in the presence of oxygen.
ANAEROBE - a bacteria that can live and grow only in the absence of oxygen.
FACULTATIVE ORGANISM - able to grow in the presence or absence of oxygen. These are adaptable and found at the bottom of a periodontal pocket.
OBLIGATE ORGANISM - not adaptable.
Microorganisms
Micro organisms/ bacteria usually classified according to shape.
COCCI - spherical bacteria which form different arrangements eg when growing in chains they’re referred to as streptococci( found in early plaque) and when found in clusters known as staphylococci.
BACILLI - these are elongated rod shaped organisms(found in early plaque ). Fusiform bacilli have tapered ends.
VIBRIO- these are curved/comma shaped. This comes later in plaque.
SPIROCHEATES - are spiral / cork screw shaped. Really damaging in plaque.
FILAMENTOUS BACTERIA/ FILAMENTS - long and thread like.
GRAMS staining - techniques used to distinguish bacteria and classify them. One commonly used is GRAM and this is distinguishes bacteria as either aerobic ( gram + ) or anaerobic ( gram - ). Gram negative bacteria present in mature plaque and play significant role in initiation and progression of periodontal diseases. Gram + more linked to caries.
Bacterial development of plaque
PLAQUE AT 3-8 HOURS( not detectable clinically).
As previously stated, bacteria are soon attracted to the pellicle once it has formed and the early colonisers are mainly gram + cocci and gram + bacilli . Eg streptococcus sanguis, streptococcus mutans and streptococcus mitior. Gram + bacilli examples include actinomyces viscosus and actinomyces neaslundii.
PLAQUE AT APPROX 24 HOURS +
At this stage a clinically detectable layer will be present. The existing bacteria continue to multiply with a rapid increase in numbers . At the end of this period you may detect gram- cocci( anaerobic).
PLAQUE AT 3-5 DAYS APPROX
Organisms are increasing in numbers and the plaque layer is becoming thicker and denser. The anaerobic bacteria are increasing and there are gram - bacilli , along with fusiform bacilli and filaments present. Some of these bacteria present at this stage are known as bridging bacteria , attaching early colonisers and plaque mass with later colonisers.
PLAQUE AT 7+ DAYS
This is mature plaque and at this stage most of early colonisers have disintegrated and died off so there is a marked decrease in the aerobic organisms and a marked increase in the anaerobic. There now exists a complex micro flora of large numbers of Gram - bacilli ( inc fusiform) , vibrio, filamentous bacteria and spirocheates.
Points about sub gingival sites
Subgingival sites are retentive areas that form a relatively stagnant environment where bacteria that cannot adhere to the tooth may survive and avoid removal by OH, salvias self cleansing etc.
Motile bacteria are mainly found in periodontal pockets are not reliant on attachment to the plaque mass , they are always anaerobic but also facultative , meaning they can survive if oxygen is introduced.
The nutrient supply in the area differs from saliva rich supra gingival area.
Micro flora subgingivally has direct access to protein rich crevicular fluid which differs both in quantity and quality to the hosts diet and saliva which form the bulk of nutrients for supra gingival .
Subgingival plaque is initially a downgrowth of supra gingival plaque. However more complex as oxidation reduction potential. Some examples of bacteria found exclusively subgingivally eg spirocheates eg treponema group , many gram bacilli eg prevotella and porphyromonas.
Composition of plaque
Inorganic elements - mainly calcium and phosphates but traces of others.
Organic elements - products of bacteria metabolism.
ACIDS - formed by action of bacteria on refined carbohydrates of diet ie lactic and pyruvic.
ANTIGENS - large molecules usually proteins on surface of cells. Trigger immune response.
ENZYMES - bacterial enzymes ie collagenase, hyaluronidase ( breaks down hyaluronic acid important as a tissue cementing substance found between epithelial cells and chondroitin sulphatase involved in breakdown of connective tissue.
TOXINS - once of significance in perio disease are formed as result of breakdown of gram - bacteria. Powerful mediators of inflammatory and immune response.
CARBOHYDRATES - ones synthesised by bacteria from dietary sources which are the polysaccharides eg dextran and fructan. These provide source of nutrients to bacteria and act like a glue causing adherence of plaque.
PROTEINS- derived from saliva
SHED EPITHELIAL CELLS
LEUCOCYTES - from gingival crevice
ERYTHROCYTES - from inflamed gingivae
BROKEN DOWN CELLS
TRACES OF FOOD DEBRIS
Additional micro organisms
STREPTOCOCCUS - gram + species include strep sanguis and strep mitis.
ACTINOMYCES - gram- bacilli
LACTOBACILLUS - gram+ bacilli
VEILLONELLA - gram- cocci, obligately anaerobic. May play beneficial role in caries converting lactic acid into a weaker acid.
AGGREGATIBACTER - gram - bacilli , A.actinomycetemcomitans(AA) . Implicated in particularly aggressive form of perio disease in younger adults. Produce powerful toxin leucotoxin which is active against neutrophil LEUCOCYTES.
FUSOBACTERIUM - gram- filaments. Obligately anaerobic . Long filamentous bacteria that bridge early and late colonising bacteria.
PREVOTELLA - gram- bacteria. High in perio disease.
PORPHYROMONAS - gram- bacilli. Found in perio disease.
TREPONEMA - gram - spirocheates. Subgingival sites.
Additional plaque info
Plaque is example of biofilm. This is a consortium of interacting micro organisms attached to a surface embedded in matrix of polymers/polysaccharides.
Mouth provides warm, moist environment for growth. Results in different flora from anywhere else. Bacteria do not colonise naked tooth , the pellicle needs to be present.
Most oral bacteria are non motile and get to tooth surface by saliva. Some bacteria unable to bind directly to pellicle but are able to interact wig molecules on bacteria already attached, known as co adhesion.
These secondary colonisers generally more fastidious in growth requirements. Many anaerobic bacteria only colonise once plaque has started to develop.
One bacteria FUSOBACTERIUM nucleatum can do adhere with almost all other bacteria in plaque and are key bridging organisms.
Role of plaque in disease
In absence of effective oral hygiene plaque can accumulate to levels that are no longer compatible with health , therefore predisposing to caries or perio disease. There is a shift in the balance of the flora away from those species that are found in healthy sites. Eg micro flora of carious sites contains high proportions of acid producing and acid tolerating species step mutans.
Periodontal diseases associated with an increased plaque mass and a shift towards a micro flora containing anaerobic gram- bacteria.
Some of these are able to subvert the host defences and provoke inappropriate and aggressive immune responses that while attacking the microbial challenge causes bystander damage to perio tissues.
Detection of plaque
Very early plaque not detectable to naked eye but once over 24 hours plus it can be detected clinically.
Direct vision- thick layer will make tooth look matted and fur like.
Use of an explorer - plaque will adhere to probe.
Tactile examination- when mature plaque begins to calcify it will slightly grainy to the probe.
Use of disclosing agent - best way.
Factors affecting accumulation and retention of plaque.
Poor / inadequate OH is primary factor. However factors that can play a part:
- stagnation areas such as overhanging restorations , bridges etc
- high refined carbohydrate diet which contributed to adherence , density and nutrients available to bacteria.
- saliva flow will cause no natural cleansing.
- complicated interaction between pecllie, bacteria and tooth.
- susceptibility
Materia Alba
Loosely adherent , unstructured white or greyish white mass of oral debris and bacteria which lies over plaque. Vigorous rinsing and water irrigation can remove it.
Derived by incidental mechanical accumulation.
Soft and cheese like , creamy , may extend over gingival margin. Covers surfaces not exposed to cleaning and may cover entire surface of a crown out of occlusion. Collects in open interdental areas. Heaviest on lingual Mandibular molars, buccal ,maxillary molars and buccal cervical third.
Can be removed by tooth brushing and vigorous rinsing. Forms readily when teeth not cleaned regularly.
