MICROBIAL FLORA OF THE MOUTH
In a person's oral cavity are three bacteria that have a tendency to cause
dental caries. These are:
1. Lactobacillus acidophilus
2. Streptococcus mutans
3. Actinomyces odontolyticus
These organisms have the ability to ferment carbohydrates, producing an
end product of Lactic Acid.
This acid is produced when the bacteria adhere to the teeth, breaking down
the carbohydrates that are coating the teeth.
Lactic acid will cause your teeth to soften and decalcify if you do not brush
this molecule off your teeth.
Example: Streptococus mutans:
a. This microorganism will excrete the enzyme dextransucrase.
b. This enzyme synthesizes glucan, it is created from the
polymerization of sucroses.
c. Fructose, a monosaccharide is also synthesized.
d. Glucan binds tightly with the teeth. The S. mutans now ferments
this polymer and fructose to produce lactic acid, which is an acid
end product, so it may cause cavities as the enamel of your teeth
TEST FOR DENTAL CARIES:
1. Use Snyder Agar Deeps. This agar contains glucose and Brom
Cresol Green which is the pH indicator.
2. Add 0.2 ml of saliva to a liquified Snyder Deep tube.
3. Mix by rotating between the hands. Place in a rack to solidify.
4. If the glucose is fermented, the pH will change to 4.4 because of
the presence of lactic acid.
5. A pH of 4.4 turns the green a yellow due to the lactic acid.