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20 Cards in this Set
- Front
- Back
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List three common microorganisms found in the mouth. |
Lactobacillus acidophilus Streptococcus mutans Actinomyces odontolyticus |
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Regarding the above microorganisms, do they produce organic acids? |
Yes. Especially lactic acid, by the fermentation of carbohydrates that adhere to the surface of teeth. |
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What happens to dental enamel in the continued presence of lactic acid? |
It decalcifies and becomes softer, which results in the formation of tiny perforations called dental caries. |
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What is Dextransucrase? |
S. mutans excretes this enzyme, also called glycosyl transferase), which can polymerize sucroses into a larger polymer called glucan, plus fructose. |
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How is the dental plaque formed? |
The polysaccharide formed adheres strongly to the teeth and forms dental plaque, where the streptococci reside and ferment fructose with the formation of lactic acid. |
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Does L. acidophilus produce lactic acid? |
Yes. It is produced as an end product of CHO fermentation. |
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Can oral lactobacilli metabolize glucose? |
Yes. As a result, organic acids are produced that reduce the oral acid concentration to a pH of less than 5. It is at this pH that decalcification occurs. |
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What exactly is the Snyder test? |
This is one microbiological method used for determining the susceptibility to dental caries. |
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What does the Snyder test measure? |
It measures the amount of acid produced by the action of the lactobacilli on glucose. |
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What does the Snyder test employ? |
It uses a differential medium, Snyder agar(pH 4.7), bromcresol green, that imparts a green color to the medium. |
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What do Snyder agar cultures reveal following incubation? |
Those containing lactobacilli from the saliva will show glucose fermentation with the production of acid, which tends to lower the pH to 4.4, the level of acidity at which dental caries form. At this pH, the medium will turn yellow. |
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What can be inferred from the yellow color? |
A culture showing a yellow color within 24 to 48 hours is suggestive of the host's susceptibility to the formation of dental caries. |
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What can be inferred from a culture that shows no color change? |
This suggests lower susceptibility. |
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During the preparation phase, what is placed on the culture? |
Organisms of the normal flora present in saliva. |
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During culture preparation what are the first two steps? |
1. Melt 2 appropriately labeled Synder agar deep tubes and cool to 45C. 2. Chew one square of paraffin for about 3 minutes without swallowing the saliva. Collect the saliva in a sterile test tube. |
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What are steps 3 and 4 of preparation? |
3. Shake the collected saliva sample and transfer .2 ml of saliva with a sterile pipette into one the Snyder test medium tubes that have been cooled to 45C 4. Mix the contents of the tube thoroughly by rolling the tubes between the palms of your hands or by tapping it with your finger. |
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What are the final steps of preparation? |
5. Rapidly cool the inoculated tube of Synder agar in an ice water bath. 6. Repeat steps 3-5 to inoculate a seconf tube. 7. Incubate tubes for 72 hours at 37C. Observe cultures at 24, 48, and 72 hours. |
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If 5 tubes are in a stand, from left to right, the tube on the left is dark green. What does this indicate. |
It is an uninoculated Synder tube. if the nest tube is lighter, but still green, this is no color change to slight color change, and may indicate no or little susceptibility to dental caries. |
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The third tube is a lighter lime green. What does this suggest? |
Slight color change indicates mild susceptibility to forming dental caries. If the next tube is a greenish-yellow, this is a significant color change. This indicates moderate susceptibility. |
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If the last tube is clear yellow, what does this suggest? |
Complete color change indicates high susceptibility to forming dental caries. |
