Interactions between Endodontic Sealers and 2% Chlorhexidine

Objectives: Complete elimination of all microorganisms from the root canal space imposes a great challenge. The antimicrobial properties of the final irrigating solution and the obturating material may therefore affect the outcome of endodontic treatments. Chlorhexidine digluconate (CHX) is widely used as the final irrigant for the root-canal system due to its antimicrobial properties. CHX may affect the properties of the root canal sealers. Information regarding the interaction between CHX left in the root canal after irrigation and endodontic sealers is limited. The aim of the present study was to assess the antimicrobial activity and the physicomechanical properties of three endodontic sealers after contact with CHX for different times.
Methods: The antimicrobial activity of the sealers AH Plus, BioRoot™ RCS, Pulp Canal Sealer (PCS) was investigated using a Modified Direct Contact Test for planktonic growth of Enterococcus faecalis in vitro. The physicomechanical properties were assessed by testing the microhardness, initial setting time and the wettability (contact angle measurements). The sealers were either incubated in continuous contact with 2% CHX for 24 hours or after 1 minute of contact time at 37^oC 100% humidity. Sealers not in contact with CHX were also prepared and incubated for 24 hours as controls. The sealers were placed in three groups according to the setting conditions: group 1, no contact (controls); group 2, 1 minute contact time; and group 3, continuous contact.
Results: Interaction with CHX increased the setting time of AH Plus and BioRoot whilst this was decreased for PCS. Contact angle measurements showed that both AH Plus and PCS became more hydrophilic (decreased contact angles) after contact with CHX, while BioRoot became more hydrophobic (increased contact angles). The microhardness of all sealers was compromised by CHX. CHX increased the antibacterial activity of all the sealers investigated.
Conclusions: CHX improved the antibacterial efficacy of all endodontic sealers tested, and affected their physicomechanical characteristics. Irrigants used for endodontic treatment may interact with endodontic sealers in the root canal and affect their physical, mechanical and antibacterial properties. The potential interaction between endodontic irrigants and sealers need to be further investigated.