dental caries Flashcards
zones of enamel caries
dental caries is an irreversible progressive microbial disease of the calcified teeth characterised by demineralisation of inorganic portion and distortion of organic substance of tooth which leads to cavitation
Zone : ranslucent Zone
♦ It is the deepest zone lies at the advancing front of the
enamel lesion.
♦ This zone is more porous than normal enamel.
♦ Pores are larger than the normal enamel.
♦ Pore volume is 1%.
♦ This zone appears structureless.
♦ This zone contains more fluoride than normal enamel.
Zone : Dark Zone
♦ Dark zone is located just superficial to the translucent zone
and its dark appearance is due to the excessive demineralization of the enamel.
♦ Zone is narrower in rapidly advancing caries and it is wider
in slowly advancing lesion.
♦ Zone contains 2 to 4% pore volume.
♦ Pores are larger than normal but smaller than those of
translucent zone.
♦ This zone reveals some degree of remineralization of
carious lesion.
Zone : ody of eison
♦ Zone is situated between the dark zone and the surface
layer of enamel.
♦ It represents the area of greatest demineralization.
♦ Pore volume is 5 to 25%.
♦ This zone contains appetite crystals larger than those of
the normal enamel.
♦ Large crystals results from the reprecipitation of minerals
dissolved from the deeper zone.
Zone : urface Zone
♦ Surface zone when examined by the polarizing light appears relatively unaffected, it may be due to the surface
remineralization by the salivary mineral ions.
role of lactobacillus and pH in caries
Among the Lactobacillus rods in the oral cavity occur: L.
acidophilus, L. casei, L. fermentum, L. delbrueckii, L. plantarum,
L. jensenii, L. brevis, L. salivarius and L. gasseri. Lactobacilli are
divided into two main groups: homofermentative which in the
fermentation process of glucose produce mainly lactic acid, e.g.
Lactobacillus casei, Lactobacillus acidophilus, heterofermentative
which in addition to lactic acid produce acetate, ethanol and
carbon dioxide, e.g. Lactobacillus fermentum.
Lactobacilli are isolated from deep caries lesions but rarely just
before the development of dental caries and in the early tooth
decay. It is believed that they are pioneering microorganisms
in the caries progress, especially in dentin.
Critical pH is the pH at which saliva appears to be saturated with the calcium and phosphorus ions. Value of
critical pH is 5.5, below the critical pH inorganic portion of
tooth starts dissolving. As there is increase in concentration
of hydrogen ion in cariogenic plaque, this leads to the loss
of more phosphate ions from the tooth.
♦ Buffering property of saliva leads to diffusion of bicarbonate ions in dental plaque and neutralizes the acid during
caries process.
zones of dentin caries
Zone : ormal Dentin
♦ This zone represents the inner most layer of the carious
dentin, here the dentinal tubules appears normal.
♦ There is evidence of fatty degeneration of the Tome’s
process.
♦ No crystals in the lumen of the tubules.
♦ No bacteria in the tubules.
♦ Inter tubular dentin has normal cross banded collagen and
normal dense appetite crystals.
Zone : ub-transparent Dentin
♦ This is the zone of dentinal sclerosis and is characterized
by the deposition of very fine crystal structures within the
dentinal tubules.
♦ Superficial layer shows area of demineralization and damage of the odontoblastic processes.
♦ No bacteria in the tubules.
♦ Dentin is capable of remineralization.
Zone : ransparent Dentin
♦ This zone appears transparent and this is because of decalcification of dentin.
♦ It is softer than normal dentin.
♦ No bacteria in tubules.
♦ Cross banded inter tubular collagen is still intact.
♦ This zone is capable of self repair and remineralization.
Zone : urbid Dentin
♦ This zone is marked by widening and distortion of dentinal
tubules, which are packed with microorganisms.
♦ There is very little amount of minerals in dentin, denaturation of collagen fibers also takes place.
♦ Zone cannot undergo self repair or remineralization.
♦ This zone must be removed before restoration.
Zone : nfected Dentin
♦ This is the outermost zone of the carious dentin.
♦ It is characterized by complete destruction of dentinal
tubules.
♦ In this zone the area of decomposition of dentin, which
occur along the direction of dentinal tubules are called
“Liquefaction foci of Miller”, which occur perpendicular
to dentinal tubules are called “Transverse clefts”.
♦ In the process, the entire dentinal structures become
destroyed and cavitation begins from dentino enamel
junction
