Abstract: Objective: To explore the microbial inhibitory effect of phenol-formaldehyde resin in sealing up pits and fissures. Methods: Thirty extracted human molars whose pits and fissures on the occlussal surface had been inoculated with Escherichia coli were randomly divided into three groups: group A was treated with newly confected phenol-formaldehyde resin which resinified the dental fissure contents, group B was sealed Bis-GMA resin in pits and fissures and group C as the control group was only treated by cleaning. Then, after slicing along the fissure, each of the teeth was put in LB medium for culturing to observe the growth of the microbe. Result: The bacteriostatic effect of the phenol-formaldehyde resin group was the best of the three groups. Conclusion: Phenol formaldehyde resin has a strong bacteriostatic effect when used as a pit and fissure sealant. In this respect it is superior to Bis-GMA resin.

Key words: Pit and fissure sealant technigue, Phenolic resin, Bis-GMA resin, Bacteriostatic effect, Escherichia coli