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Unformatted text preview: Lab Exercise: Dental Microbiology- Snyder agar OBJECTIVES 1. To become familiar with organisms responsible for dental carriers in the mouth. 2. To perform experiments that demonstrate susceptibility to caries formation. INTRODUCTION Many microbes are known to be responsible for formation of dental caries, or what we commonly call cavities. These include Lactobacillus acidophilus , Streptococcus mutans , and Actinomyces odontolyticus . These microbes produce organic acids, especially lactic acid, by fermenting carbohydrates found on the surface of the teeth. Long term exposure to these acids breaks down dental enamel and leads to the formation of dental carries. One of the best methods for predicting susceptibility to dental caries is the Snyder test. This test measures the amount of acid produced by lactobacilli on glucose. The test uses a differential medium, Snyder agar (pH 4.7), which contains glucose and a pH indicator, brom cresol green, that gives the medium a green color. Following incubation, Snyder agar cultures containing lactobacilli in 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. The pH indicator will turn yellow at this point. A culture demonstrating a yellow color within 24 to 48 hours is suggestive of the host’s susceptibility to the formation of dental caries. LAB EXERCISES Individual supplies 2 Snyder agar deeps Container for saliva collection Gum or wax candy P200 Pipet and pipet tips 1. Chew a piece of gum or wax candy for approximately 3 minutes without swallowing saliva. Chew a piece of gum or wax candy for approximately 3 minutes without swallowing saliva....
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- Fall '09
- Microbiology, Dental caries, Streptococcus mutans, Snyder, Mitis Salivarius Agar