When dentin is etched and over-dried, bond strength and sealing potential are compromised.  Wetting agent containing HEMA may help to preserve the collagen network.  Additional antimicrobial properties might reduce microorganisms that are still present.

Objective: The aim of study was to test the bactericidal effects of an experimental rewetting and desensitizing agent containing chlorhexidine. 

Materials and Methods:  Human molars were sectioned into 1 mm thick discs.  Surface areas of the discs were measured by the Quantimet Image Analyzer.  The discs were gas sterilized before being treated with one of the following: Chlorhexidine digluconate (0.12%) as the positive control, HEMA- containing rewetting agent with 0.2% chlorhexidine (AP1), similar HEMA agent with 0.4% chlorhexidine (AP2), and no treatment (negative control).  The discs (n=3 /group) were treated on both the obverse and reverse surfaces and then placed into 1.5 mL of BHI broth with 0.1 mL of Streptococcus sobrinus.  After incubating for 24 hours at 37^oC, the discs were transferred to vials containing 5 ml buffered saline and sonicated for 5 minutes.  Dilutions in BHI broth were at 10^-1-10^-4.  Each dilution was plated in duplicate on BHI agar plates and incubated for 24 hours at 37^oC.  The colonies were then counted, recorded, and analyzed.    The digital images were used to adjust for surface area differences.

Results:  The positive control group showed growth of 48.3x10 colonies/mL, and the negative control (no treatment) 48.8x10⁴ colonies/mL.  AP1 showed growth of 45.2x10⁵ colonies/mL, while AP2 was 17.8x10⁵ colonies/mL.  One-way ANOVA demonstrated significant differences among groups (p<0.001). 

Conclusion:  HEMA's overall charge is negative, and chlorhexidine is attracted to negative charges.  HEMA in AP1 and AP2 might bind to the chlorhexidine and interfere with its bactericidal action.  A higher concentration is recommended for optimal bactericidal effects.

Supported by a grant from Bisco, Inc.