Methods: The efficacy against microorganisms was evaluated by calculating the inhibition zones as radii caused by the gel when placed in small wells on agar plate cultures of Strep-tococcus mutans (S.m.), S. sobrinus (S.s.), Lactobacillus casei (L.c.), Actinomyces naes-lundii (A.n.) and Candida albicans (C.a.). Viscosity was measured using a controlled strain and stress rheometer at shear rates of 1 to 100s-1. Fluoride release was determined by plac-ing the gel in a petri dish with deionized water which was horizontally shaken. The released amount of fluoride was quantified employing an ion selective electrode.
Results: A gel formulation was developed containing 0.2% CHXdG and sodium fluoride each and providing good handling and antimicrobial properties. Inhibition zones were largest for A.n. (11.0mm), followed by S.m. (6.3mm), S.s. (6.0mm), L.c. (5.0mm) and C.a. (2.5mm). The gel shows shear thinning properties: 20 Pa*s and 1.5 Pa*s at a shear rate of 1s-1 and 100s-1. The fluoride is completely released by dissolution of the gel within 1 minute.
Conclusion: The oral health care product Cervitec® Gel with 0.2% CHXdG shows very good antimicrobial properties against oral microorganisms comparable to those of similar products even with higher chlorhexidine concentrations (1.0% CHXdG). The shear thinning properties and the low viscosity at higher shear rates enables a convenient handling promoting an easy application of the fast fluoride releasing gel.