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 caries2. Caries developed with bacteria inoculated.3. Antibiotics inhibited caries4. Bacteria found in all caries specimensConclusiondental 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.
8. • - early stage plaque -late stage plaque
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 pellicleare 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.