Chlorhexidine and thymol release from a varnish system.

The release of chlorhexidine and/or thymol from an antimicrobial containing varnish in an in vitro model was investigated. Four varnishes with the same polymer base were studied; one with chlorhexidine only, one with thymol only, one with both agents and a placebo varnish without the active agents. Microscope glass slides were covered with the varnishes and stored in water. During the following three months liquid samples were regularly withdrawn and analysed for chlorhexidine and thymol content. The released amounts of chlorhexidine and/or thymol were determined by means of U.V. spectrophotometry. The results showed that chlorhexidine was released slowly from the chlorhexidine-only varnish compared with the thymol release from the thymol-only varnish. In the case of the clinically tested varnish (containing both active ingredients chlorhexidine and thymol) the amounts of thymol and chlorhexidine released were comparable. Most important, however, was the observation that in the last mentioned case both agents continued to be released after 3 months.