Microbiology Dental Caries Dr. Esra Hassan Dental caries is a infectious microbiologic disease of the teeth that results in localized dissolution and destruction of calcified tissues According to who

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Dental Caries

Dr.Esra Hassan

Dental caries is a infectious microbiologic disease of the teeth that results in localized dissolution and destruction of calcified tissues

According to WHO: is defined as localized post eruptive pathological process of external origin involving softening of the hard tooth tissue and proceeding to the formation of cavity.

It is defined it as a "microbial disease" of the calcify. tissues of the teeth, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth

carious teeth

Dental Caries: A Bacterial Infection

There are two specific groups of bacteria found in the mouth that are responsible for dental caries ;

1. Mutans streptococci (Streptococcus mutans)

2. Lactobacilli

They are found in relatively large numbers
in the dental plaque.

Transmission of Caries Causing Bacteria

Mutans streptococci are transmitted through saliva, most frequently the mother’s, to the infant.

When mothers have high counts of mutans streptococci in their mouths, the babies also have high counts of the same bacteria in their mouth.

Women should be certain their own mouths are healthy.

When the number of caries causing bacteria in the mouth increases, the risk for developing dental caries also increases.

rout of transmission from mother to baby .

Microbial Ecology in Health and Disease

Interactions between mutans streptococci and lactobacilli contribute towards the microbial challenge of dental caries. A comparison was made between numbers of mutans streptococci and lactobacilli in plaque from primary teeth in healthy children and between caries-free teeth and carious lesions in the same mouth of children with caries.

Streptococcus mutans


Streptococcus mutans are gram-positive cocci shaped bacteria. These facultative anaerobes are commonly found in the human oral cavity, and is a major contributor of tooth decay. The result of decay can greatly affect the overall health of the individual

S. mutans are mesophilic and grow at temperatures between 18-40 degrees Celsius. Streptococcus mutans is a cariogenic microorganism that breaks down sugar for energy and produces an acidic environment, which de-mineralizes the superficial structure of the tooth. The result of the conversion disintegrates the coating of the tooth then later dissolves the Calcium molecule creating a hole. Transmission of S. mutans can be found in people of all ages although it is more common for infants and children. The transfer of genotypes are responsible for the transmission of S. mutans from mothers to their children although, there is a genotypic variation from one population to the next.

Streptococcus mutans possesses three virulence factors: water insoluble glycans, acid tolerance, and production of lactic acid

■ A toothache is the most common symptom of tooth decay. An infection or irritation of the tooth pulp usually causes the pain.

streptococcus mutans negative stain

under microscope


Streptococcus mutans is considered to be part of the "normal" flora of the human mouth, which is associated with dental caries also known as tooth decay. Dental caries is an infectious and communicable dental disease that affects people of all ages. Streptococcus mutans can be passed from one person to the next via horizontal or vertical transmission. The transmission route of Streptococcus mutans is to colonize itself among human hosts. Children and infants are more prone to the diagnosis of Streptococcus mutans and studies show that many receive it from their primary caregivers

S. mutans favors hard non-shedding surfaces to establish permanent colonies, which implies that levels of S. mutans are undetected in infants until the primary teeth extravasate. Typically between the ages of one and two, teeth erupt, which allows S. mutans to establish flourishing colonies on teeth, and causes cavities. The indication of cavity formation is the appearance of detectable levels of bacteria on teeth.

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