Method: Streptococcus mutans and sanguis were cultured in blood agar . cholorhexidin , salt and acetic acid were diluted using sterilewater. Soaking paper discs in each of them we put the paper in the plates which the bacteria was cultured in. In each plate a paper soaked in sterilewater was as a control. Then we evaluated the plates for the area of " no growth" Then after culturing bacteria in "tripson soy broth" minimum inhibiting concentration (MIC) of each was determined.
Result: Minimum inhibiting concentration (MIC) of cholorhexidin for streptococcus mutans was 0.5 μg/ml and for streptococcus sanguis was 4 μg/ml .MIC of salt for both kinds of bacteria was 5 %. Both of them were resistance to acetic acid (MIC> 4096 μg/ml).The "no growth" area was just around the disk soaked in cholorhexidin 0.2%.
Conclusion: The inhibitory effect of cholorhexidin on streptococcus mutans is more than streptococcus sanguis, reduces the mutans to sanguis ratio ; so that its anti caries effect is significant. Salt can be used as mouthwash to inhibit dental caries.
Keywords: Antimicrobial agents/inhibitors, Bacterial, Caries and cholorhexidin