calculus

lec 5 Dental Calculus Dr.Hussein Al dabbagh

Acquired Pellicle : Following tooth eruption or a dental prophylaxis, a thin, saliva- derived layer, called the acquired pellicle, covers the tooth surface.

Dental Plaque is defined as a specific but highly variable structural entity resulting from sequential colonization and growth of microorganisms on the surfaces of teeth and restoration consisting of microorganisms of various strains and species are embedded in the extra cellular matrix, composed of bacterial metabolic products and substance from serum, saliva and blood.

Materia Alba refers to soft accumulations of bacteria and tissue cells that lack the organized structure of dental plaque.
Dental calculus : is a hard deposit that is formed by calcification of dental plaque primarily composed of calcium phosphate mineral salts which is deposited on natural teeth and restorations and is covered by a layer of unmineralized plaque. These hard deposits may form coronal to or apical to the gingival margin, hence named accordingly as supragingival and subgingival calculus respect tively
The primary cause of gingival inflammation is bacterial plaque, other predisposing factors including calculus, faulty restoration, complication associated with orthodontic therapy, self-inflicted injuries, use of tobacco, and others.
Calculus consists of mineralized bacterial plaque that forms on the surface of natural teeth and dental prosthesis.

Supra and sub-gingival calculus:

Supra-gingival calculus is located coronal to the gingival margin and therefore visible in the oral cavity, it's usually white to yellowish in color, hard with claylike consistency and easily detected from the tooth surface, after removal, it may rapidly recur, especially in the lingual area of the mandibular incisors, it's color is influenced by contact with such substances as tobacco and food pigments. It may localize on a single tooth or group of teeth or it may be generalized throughout the mouth.
The two most common locations for supra-gingival calculus to develop are the buccal surface of maxillary molars and the lingual surface of mandibular anterior teeth, saliva from the parotid gland flows over the facial surface of the upper molars via the parotid duct, while the submandibular and sublingual gland empty onto lingual surface of lower incisors via the submandibular and lingual ducts respectively.
Sub-gingival calculus is located below the crest of the marginal gingiva and therefore not visible on routine clinical examination, the location and extent of the sub-gingival calculus may be evaluated by careful tactile perception with a delicate dental instruments such as a dental explorer, sub-gingival calculus is typically hard and dense, frequently appears dark brown or greenish black in color firmly attached to the tooth surface.
When the gingival tissue recede, sub-gingival calculus become exposed and it's therefore classified as supra-gingival, a reduction in the gingival inflammation and probing depths with a gain in clinical attachment can be observed after the removal of sub-gingival plaque and calculus.
Both supra and sub gingival calculus maybe seen by radiograph.

Composition:

Inorganic content: supra-gingival calculus consist of inorganic (70% to 90%) and organic components(20-3o%), the major inorganic proportions of calculus have been reported as approximately 76% calcium phosphate Ca3(PO4); 3% calcium carbonate CaCO3; traces of magnesium phosphate Mg3(PO4) and other metals.
The percentage of inorganic constituents in calculus is similar to that in other calcified tissue of the body, the principle inorganic components have been reported as approximately 39% calcium, 19% phosphate, 2% carbon dioxide and 1% magnesium and trace amounts of sodium, zinc, strontium, bromine, copper, manganese, tungsten, aluminum and silicon.
At least two thirds of the inorganic component is crystalline in structure, the four main crystal forms and their approximate percentage are as follows:
hydroxyapatite 58%
magnesium white-lockite 21%
octacalcium phosphate 12%
and brushite 9%.
Generally two or more crystal forms are typically found in the sample of calculus hydroxyapatite and octacalcium phosphate are detected most frequently (i.e. in 97% to 100% of the supra-gingival calculus) and constitute the bulk of the specimen.
Brushite is more common in the mandibular anterior region and magnesium white-lockite is in the posterior areas, the incidence of the four crystals varies with the age of the deposit.
The composition of sub-gingival calculus is similar to that of supra-gingival calculus with some differences, it has the same hydroxyapatite content, more magnesium white-lockite, and less brushite and octacalicium phosphate.
Organic content: the organic component of calculus consist of a mixture of protein-polysaccharide complexes, desquamated epithelial cells, Leukocytes and various types of microorganisms.
Salivary proteins present in supra-gingival calculus are not found sub-gingivally, dental calculus, salivary duct calculus, and calcified dental tissue are similar in inorganic composition.


Attachment of calculus to the tooth:
Attachment by means of organic pellicle.
Mechanical inter locking between the surface irregularities such as resorption lacunae and caries.
Penetration of calculus bacteria into cementum.
Close adaptation of calculus under surface dispersions to the gently sloping mounds of the unaltered cementum surface.

Formatiom:

Calculus is dental plaque that has undergone mineralization; the soft plaque is hardened by precipitation of mineral salts which is usually started between first and fourteenth days of plaque formation. Calcification started as soon as 4-8 hours, calcifying plaque may become 50% mineralized in 2 days, 60%-90% mineralized in 12 days. However, the formation of dental calculus with the mature crystalline composition of old calculus may require months to year. All plaque not necessarily undergo calcification, early plaque contains small amounts of inorganic material which increase as the plaque develop into calculus. Microorganisms are not always essential in calculus formation because calculus occurs readily in germ free rodents, saliva is the source of mineralization for supra-gingival calculus whereas the serum transudate (gingival crevicular fluid) is source of mineralization of sub-gingival calculus.
Early plaque of patients who one heavy calculus formers contain more calcium, more phosphorus (three times) and less potassium than that of non-calculus formers (i.e., phosphorus is critical in calculus formation).
Calcification entails the binding of calcium irons to carbohydrates-protein complex of organic matrix and the precipitation of crystalline calcium phosphate salts.
Crystals form initially in the intercellular matrix and on the bacterial surface and finally within the bacteria.
Calcification begins along the inner surface on the supra-gingival plaque and in the attached component of sub-gingival plaque adjacent the tooth.
Separate foci of calcification increase in size and coalesce to form solid masses of calculus, the initiation of calcification and rate of accumulation vary among teeth in same individual, so person may be heavy, moderate or slight calculus former.
Calculus formation continues until it reaches maximum after which it reduced in amount due to mechanical wear from food and the cheeks, lip and tongue, also the use of anti-calculus (anti tarter) dentifrices reduce both quality and quantity of calculus.

Theories regarding the mineralization of calculus :

The theoretical mechanisms by which plaque becomes mineralized can be stratified into two categories:
Mineral precipitation results from a local rise in the degree of saturation of calcium and phosphate irons, which may be brought about in the following several ways:
A rise in the PH of the saliva causes precipitation of calcium phosphate salts by lowering the precipitation constant. The PH may be elevated by the loss of carbon dioxide and the formation of ammonia by dental plaque bacteria or by protein degradation during stagnation.
Colloidal proteins in saliva bind calcium and phosphate irons and maintain a supersaturated solution with respect to calcium phosphate salts. With stagnation of saliva, colloids settle out of the supersaturated state is on longer maintained, leading to precipitation of calcium phosphate salts.
Phosphate liberated from dental plaque, desquamated epithelial cells, or bacteria precipitates calcium phosphate by hydrolyzing organic phosphates in saliva, thus increasing the concentration of free phosphate irons. Esterase is another enzyme that is present in the cocci and filamentous organisms, leukocytes, macrophages, and desquamated epithelial cells of dental plaque. Esterase may initiate calcification by hydrolyzing fatty esters into free fatty acids. The fatty acids form soaps with calcium and magnesium that are later converted into the less-soluble calcium phosphate salts.
Seeding agents induce small foci of calcification that enlarge and coalesce to form a calcified mass. This concept has been referred to as the epitactic concept or more appropriately, hetero-geneous nucleation. The seeding agents in calculus formation are not known, but it is suspected that the intercellular matrix of plaque plays an active role. The carbohydrate-protein complexes may initiate calcification by removing calcium from the saliva (chelation) and binding with it to form unclei that induce subsequent deposition of minerals.


Role of microorganisms in mineralization of calculus
Mineralization of plaque generally starts extracellularly around both gram-positive gram-negative organisms but may also start interacellularly. Filamentous organisms, diphtheroids and bacteriomena and veillonella species have the ability to form intercellular apatite crystal. Mineralization spreads until the matrix and bacteria are calcified.bacteria plaque may actively participate in the mineralization of calculus by forming phosphates, which changes the HP of the plaque and induces mineralization but the prevalent opinion is that these bacteria are only passively involved and are simply the occurrence of calculus like deposits in gram-free animals supports this opinion.
difference between plaque and calculus:
Plaque is the sticky, colorless film that constantly forms on your teeth. Bacteria live in plaque and secrete acids that cause tooth decay and irritate gum tissue. This irritation causes an inflammatory reaction by your body that can eventually lead to gingivitis and periodontal disease. If plaque is not removed regularly by tooth brushing and flossing, it hardens to create calculus (also known as tartar). Calculus cannot be removed with a toothbrush; only a dental professional can remove it during an oral cleaning. To keep plaque and calculus under control, it is essential to brush your teeth twice every day, floss at least once every day, and see your dental professional for regular cleanings.