Background: Previous studies on the effect of the chlorhexidine and thymol-containing varnish (Cervitec((R))) have consistently shown a reduction in STREPTOCOCCUS MUTANS, while the data on the caries-inhibiting effect are conflicting.

Aim: To measure the effect of a chlorhexidine- and thymol-containing varnish (Cervitec) on approximal caries in a low caries population.

Material: Eighty-five schoolchildren, 13 years of age, entered the study after being selected on the basis of bitewing radiographs. Children with at least one approximal lesion were included after informed consent.

Methods: The study was carried out as a double-blind, randomized controlled trial according to a split-mouth design using Cervitec on one side and a placebo varnish on the other side. All approximal surfaces between molars and premolars were treated every 3rd month. After 2 years new bitewing radiographs were taken. A total of 73 children completed the 2-year study.

Results: Neither the difference in number of new lesions between the Cervitec-treated and the placebo-treated side (d: -0.21; 95% CI: -0.57; 0.16) nor the mean difference in number of already existing lesions that progressed (d: -0.01; 95% CI: -0.33; 0.30) were statistically significant (paired t test; p > 0.05).

Conclusion: The results of our study do not indicate an effect of Cervitec on initiation or progression of approximal caries in a population with a low DMFS.