Additional disinfection with a modified salt solution in a root canal model

Objectives
The aim of this study is to investigate the disinfecting properties of a modified salt solution (MSS) and calcium hydroxide (Ca(OH)2) in a non-direct-contact ex-vivo model.
Methods
Seventy-four single-canal roots infected with Enterococcus faecalis were treated with 1% sodium hypochlorite (NaOCl) irrigation or with NaOCl irrigation with subsequent dressing with MSS or Ca(OH)2. After removal of the dressings, the roots were filled with bacterial growth medium and incubated for seven days to enable the surviving bacteria to repopulate the root canal lumen. Growth was determined by sampling the root canals with paper points before treatment (S1), after treatment (S2) and incubation after treatment (S3). The colony forming units were counted at S1 and S2. At S3, growth was determined as no/yes regrowth. The Kruskal-Wallis, McNemar and χ2 test were used for statistical analyses.

Results
At S2, in the NaOCl group, growth was found in 5 of 19 root canals. After the removal of MSS or Ca(OH)2 bacteria were retrieved from one root canal in both groups. At S3, repopulation of the root canals had occurred in 14 of 19 roots after sole NaOCl irrigation, 6 of 20 roots after MSS-dressing and in 14 of 20 roots after Ca(OH)2-dressing. MSS was more effective in preventing regrowth than Ca(OH)2 (P = 0.009).

Conclusions
The modified salt solution prevented regrowth in roots which indicates that it can eliminate persistent bacteria. Dressing the root canals with Ca(OH)2 did not provide additional disinfection after NaOCl irrigation.