b. Cariogenic Plaque. Plaque containing microorganisms which cause dental
decay (caries) are called cariogenic plaque. When refined carbohydrates, such as
sucrose (table sugar), are put into solution in the mouth fluids, they are able to
penetrate into the plaque. Once inside the plaque, microorganisms metabolize the
carbohydrates and produce an acid. This acid, held in the plaque and adhering directly
against the tooth surface, starts the process of dental caries by the destruction of
(demineralizing) enamel.
c. Periogenic Plaque. Periogenic plaque forms at or near the gingival tissue
level on the tooth. It affects the periodontal structures (tissue, periodontal ligament, and
bone), provoking an inflammatory response, which is seen as periodontal disease. The
microorganisms do not produce damage by demineralization as in the case of
cariogenic plaque. This plaque becomes mineralized to form a hard substance known
as calculus. The organized microorganisms in this plaque produce toxins which first
destroy the integrity of the epithelium covering the gingiva and, eventually, affect the
other periodontal tissues.
2-11. CALCULUS
a. General. In time, calcium salts from the saliva precipitate into the periogenic
plaque. This calcific accretion is called calculus. Present on the outer layer of the
calculus is the periogenic plaque which continues to produce toxins that irritate and
destroy the periodontal tissues. Some plaque may reach maximum mineral content in
two days. Other plaque may be 50 percent calcified in two days and 60 to 90 percent
calcified in 12 days. Most calculus is 70 to 90 percent inorganic, consisting mostly of
calcium salts. Calculus, once hardened, can no longer be effectively removed by the
patient but must be scaled away by a dental specialist, preventive dental specialist, or
dentist.
b. Supragingival Calculus. Supragingival calculus (salivary calculus) collects
on the clinical crown (tooth surfaces not covered by gingival tissue). See figure 2-3. It
is a hard, calcified material removed by the preventive dental specialist during an oral
prophylaxis. Supragingival calculus is usually white to creamy-white, but it may be
stained darker by food, tobacco, or other material. It may be found anywhere in the
mouth, especially on the lingual and proximal surfaces of mandibular anterior teeth and
the facial and proximal surfaces of the maxillary first and second molars. These are
common sites for calculus formation because they are near the openings of salivary
ducts. Saliva is the main source of inorganic material for formation of calculus. The
inorganic structure of supragingival calculus is primarily calcium phosphate (76
percent), mainly in the form of hydroxyapatite crystals (58 percent). The organic portion
(10 to 30 percent) consists of dead microorganisms, epithelial cells, plaque matrix, and
margin.
MD0513
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