The Snyder Test is used to determine a personís susceptibility to dental caries (cavities). The susceptibility is correlated with acid production that is assumed to result from fermentation by cariogenic Lactobacillus species on the teeth or in other areas of the mouth.
The Snyder Test agar contains 2% glucose and the pH indicator bromcresol green. The pH of the agar is ~ 4.8, which inhibits the growth of most organisms, but it is ideal for acidophiles such as Lactobacillus species. Saliva samples are inoculated into the tubes and allowed to incubate. If Lactobacillus is present in the saliva, it will ferment the glucose and produce lactic acid, causing the pH to drop to ~ 4.4. This causes the bromcresol green to change from green to yellow. A culture demonstrating a yellow color indicates a person is susceptible to the formation of dental caries.
Tube 1: Uninoculated Synder tube
Tube 2: No color change indicates little or no susceptibility to forming dental caries
Tube 3: Sight color change indicates mild susceptibility to forming dental caries
Tube 4: Significant color change indicates moderate susceptibility to forming dental caries
Tube 5: Complete color change indicates high susceptibility to forming dental caries.
Back to Tutorial