Investigation of the effect of rapid and slow external pH increases on Enterococcus faecalis biofilm grown on dentine

Abstract

Background

Calcium hydroxide is a common endodontic medicament and has an anti-microbial effect by increasing the localized pH within the root canal. However, Enterococcus faecalis has shown some resistance to calcium hydroxide.

Method

A flow cell apparatus was used to grow an E. faecalis biofilm on dentine discs. Following 4 weeks growth in Todd Hewitt Broth, flow cells were exposed to either a rapid or slow increase to pH 11.5 or 12.5. Cellular viability was determined using serial plating and the number of colony forming units was normalised against the cellular protein content. Scanning electron microscopy was carried out to qualitatively observe the effects of the different rates of pH increase.

Results

A significant difference in viability between the pH rapid and slow groups was not shown in this study. Compared to pH 11.5 solutions, pH 12.5 solutions were more effective at killing bacteria although some E. faecalis still survived.

Conclusion

E. faecalis did not adapt and develop a greater resistance to high pH following a slow rise in pH compared with a rapid rise in pH. As expected, pH 12.5 was more effective in reducing bacterial numbers compared to pH 11.5 although E. faecalis was not completely eliminated.

This article is protected by copyright. All rights reserved.

http://ift.tt/2ASkPnm