Lactobacillus plantarum lipoteichoic acid disrupts mature Enterococcus faecalis biofilm.

Apical periodontitis is caused by biofilm-mediated root canal infection. Early phase oral bacterial biofilms are inhibited by Lactobacillus plantarum lipoteichoic acid (Lp.LTA). However, mature biofilms that develop over 3 weeks are more resistant to traditional endodontic medicaments. Therefore, this study examined the effectiveness of Lp.LTA on disrupting mature Enterococcus faecalis biofilms, and on enhancing the effects of endodontic medicaments. LTA was purified from L. plantarum through butanol extraction followed by hydrophobic and ion-exchange chromatography. E. faecalis biofilms were formed over 3 weeks on glass bottom dishes and in dentin blocks obtained from human single-rooted premolars. These mature biofilms were treated with or without Lp.LTA for 1 h, followed by additional treatment with either chlorhexidine digluconate (CHX), calcium hydroxide (CH), or triple antibiotics for 24 h. Biofilms on glass were live/dead stained and quantified by ZEN through confocal laser microscopy. Bio-films in dentin were fixed, sputter coated and analyzed by ImageJ with scanning electron microscopy. Preformed E. faecalis mature biofilms on the culture dishes were dose-dependently disrupted by Lp.LTA. Lp.LTA potentiated the effects of CHX or CH on the disruption of mature biofilm. Interestingly, CHX-induced disruption of preformed E. faecalis mature biofilms was synergistically enhanced only when pre-treated with Lp.LTA. Furthermore, in the dentin block model, Lp.LTA alone reduced E. faecalis mature biofilm and pre-treatment with Lp.LTA promoted the anti-biofilm activity of CHX. Lp.LTA could be an anti-biofilm or supplementary agent that can be effective for E. faecalis-biofilm-induced diseases.

Effects of root canal irrigants on the push-out strength and hydration behavior of accelerated mineral trioxide aggregate in its early setting phase.

INTRODUCTION: The purpose of this study was to evaluate the effects of endodontic irrigants on the push-out strength and hydration behavior of accelerated mineral trioxide aggregate (MTA) in its early setting phase. METHODS: In an in vitro perforation model, MTA with or without 10% CaCl(2) was condensed and allowed to initial set for 10 minutes. The samples were divided into four groups (n = 10) to be immersed into either 3.5% sodium hypochlorite (NaOCl) or 2% chlorhexidine gluconate (CHX) for 30 minutes and then allowed to set for 48 hours. In the control group, a wet cotton pellet was placed over MTA. The maximum force applied to the set MTA mixture before dislodgement was recorded. Irrigant-treated surfaces were examined using a scanning electron microscope (SEM). Chemical elements of these surfaces were also analyzed by energy dispersive x-ray spectroscope (EDS). RESULTS: The push-out strength of group A1 (NaOCl-treated accelerated MTA) was the highest of all groups. When compared with nonaccelerated MTA, CaCl(2)-accelerated MTA showed significantly higher push-out strength (p < 0.05). NaOCl-treated groups showed significantly higher push-out strength than CHX-treated groups (p < 0.05). Scanning electron microscopic examination and EDS analysis showed that the formation of calcium hydroxide crystals on accelerated MTA exposed to NaOCl was increased compared with those of the control group. CONCLUSION: These findings imply that the use of accelerated MTA under the NaOCl irrigation was effective in perforation repair without altering its hydration behavior even in the early setting phase.

Effect of smear layer and chlorhexidine treatment on the adhesion of Enterococcus faecalis to bovine dentin.

The aim of this in vitro study was to determine the effects of a smear layer and chlorhexidine (CHX) treatment on the adhesion of Enterococcus faecalis to bovine dentin. Forty dentin blocks from bovine incisors were prepared and randomly divided into four groups of 10 each. The blocks in group 1 were placed in sterile saline for 5 minutes, while those in group 2 were treated with 17% EDTA for 5 minutes. The blocks in group 3 were placed in 2% CHX for 7 days. The blocks in group 4 were treated with 17% EDTA for 5 minutes, and then placed in 2% CHX for 7 days. All the blocks were immersed in a suspension of E. faecalis for 3 hours. The bacteria adhering to the dentin surface were counted by examination using a scanning electron microscope. The most significant amount of bacteria was retained on the samples from group 1 (p < 0.05) and the smallest amount of bacteria adhered to the samples from group 4. These results suggest that a smear layer enhances the adherence of E. faecalis to the dentin, and CHX is effective in reducing the adherence of microorganisms.