2. Dental caries:
•
def :
• infectious microbiological diseases of the tooth
structure result in the localized dissolution and
destruction of calcified tissue
caries lesion only occur under a mass of bacteria
capable of producing a sufficiency acid
environment to demanerialize tooth structure
Lactic acid : organic weak acid
3. Plaque
• Plaque: Gelatinous mass of bacteria adhering to
the surface is treated
the plaque bacteria metabolize refined
carbohydrates for energy and produce organic
acid as byproduct These acids may cause carious
lesion by dissolution of the tooth surface
Carious lesion progress as series of exoneration
and remission as the PH acid at the tooth surface
various with the change in the plaque
metabolism
4. The groups of oral bacteria :
1. No bacteria no caries
2. Caries developed with bacteria inoculated.
3. Antibiotics inhibited caries
4. Bacteria found in all caries specimens
Conclusion
dental caries may be caused by members of
the commensal oral microflora
5. But
• not any microbe to be considered responsible
for a given condition
• produce great amounts of acids (acidogenic),
• tolerant of acidic environments (aciduric)
MS and lactobacilli
6. the hypotheses concerning the
etiology of dental caries :
• There are two hypotheses concerning the
pathogenicity of plaque.
1- nonspecific plaque hypothesis: which
assumes that all plaque is pathogenic,
2- specific plaque hypothesis : plaque as
pathogenic only when signs of associated
disease are present.
7. Etiology of dental caries :
a. pathogenic bacterial plaque :
• soft, translucent, and tenaciously adherent
material accumulating on the surface of teeth
is commonly called plaque. It is more
accurately described as bacterial plaque
because it is composed almost completely of
bacteria and their by-products.
9. early stage plaque
• After professional removal of all organic
material and bacteria from a tooth surface, a
new coating of organic material begins to
accumulate immediately. Within 2 hours a
cell-free, structureless organic film, the
pellicle, can completely cover the previously
denuded area. The pellicle is formed primarily
from the selective precipitation of various
components of saliva.
10. The functions of the pellicle
are believed to be:
(1) protect the enamel,
(2) reduce friction between the teeth,
(3) possibly provide a matrix for remineralization.
• early secondary succession: S. sanguis along with
Actinomyces viscosus, Actinomyces naeslundii, and
Peptostreptococcus are the main pioneering
species and are capable of attaching to the pellicle
within 1 hour after tooth cleaning."
11. late stage plaque
• The late stages of ecologic succession in
plaque are responsible for causing either
caries or periodontal disease.
