The peritoneal explant test for evaluating tissue tolerance to mouthrinses

The tissue cultures of explants of neonatal rat peritoneum have been demonstrated to be a sensitive test for tissue compatibility with wound antiseptics. The present study investigated the suitability of this method to assess the relative toxicity of mouthrinses to tissue. Mouthrinses containing 0.1% chlorhexidine (Chlorhexamed Fluid 0.1%) (A), 0.3% triclosan (Colgate) (B), essential oil in ethanolic solution (Listerine) (C), and amine/stannous fluoride (Meridol) (D) were tested at use concentration and in dilutions of 10, 1, and 0.1% with exposure times of 1, 10, and 30 min, respectively. The mouthrinses (test) and Ringer's solutions (control) were applied to opened rat peritoneum. After thorough irrigation with Ringer's solution, a piece of peritoneum was removed and 1 x 1 mm explants were cut. The explants were cultivated with a bovine serum culture medium in 24-well plates at 37 degrees C in a CO2 incubator (95% air, 5% CO2). After 10 days, the tissue proliferation for the explants was assessed by a stereo microscope at 10x magnification after ethanol fixing and hemalaun staining. With 24 grafts per test, the proliferation rate was calculated relative to a control, which was run for each mouthrinse and concentration/time combination. Data were analyzed using ANOVA (SPSS 11.0) and post-hoc paired t test. Statistical significance of all correlations was tested by setting the significance level at p < 0.05. At most concentrations, D caused significantly less tissue damage than A or B. There was no difference between C and A or C and B at 100%. However, the toxicity of C was significantly less than A or B at 10, 1, and 0.1%. C and D behaved similarly except for the 10% (30 min) and the 1% (10 min) solutions in which C was significantly less toxic. We concluded that the rat peritoneum explant test was demonstrated to be a sensitive test to assess the relative toxicity of mouthrinses to tissue.