Reconstituted Buccal Tissue Integrity and Proinflammatory Response of Commercial Mouthwashes

Objective: To evaluate tissue responses to four commercial mouthwashes – Cool Mint Listerine® (LM), Natural Citrus Listerine® (LC), ACT® Plus Freshening (AP) and ACT® x2™ (AX). Methods: Products were applied onto reconstituted buccal tissue equivalents and cultures were incubated for 10 minutes, and 1, 3 and 24 hours. Parameters evaluated were viability of the buccal equivalents, tissue integrity, cell death, and secretion of IL-1&alpha and IL-1&alpha-receptor antagonist (IL-1RA). Results: The Listerine®-treated buccal equivalents exhibited many atypical and highly vacuolated cells, which increased with exposure time. The ACT®-treated equivalents showed only minor changes in tissue integrity, which were observed mainly after 24 hours of exposure. Caspase-3 staining following 24 hours of exposure showed high levels of dead cells in the Listerine®-treated equivalents, but only few apoptotic cells in the ACT®-treated equivalents. The effect of AX (11% alcohol) on tissue integrity was similar to that of AP (no alcohol). Another clear separation between the two Listerine® and the two ACT® products was in their irritation potential, as measured by IL-1&alpha and IL-1RA secretion. IL-1&alpha secretion induced by the Listerine® mouthwashes compared to the ACT® mouthwashes was slightly increased following three hours and about three times higher following 24 hours of exposure. IL-1RA secretion induced upon exposure to the Listerine® products was at least 10 times higher than the level induced by the ACT® products at all time points. No difference in IL-1&alpha and IL-1RA secretion was observed between the two Listerine® products or between the two ACT® products. Conclusions: These data suggest that an ingredient in mouthwash preparations other than alcohol may affect irritancy and oral tissue integrity. Alternatively, a critical level of alcohol (>11%) could be required to induce the proinflammatory and cell death responses.