Introduction: Missing teeth can be replaced by dental implants. To achieve good results using dental implants, it is important that there is sufficient bone volume. In cases with bone defects, simultaneous augmentation technique becomes an alternative for bone augmentation. To minimize the contamination with oral bacteria during the bone collection, preoperative rinsing with chlorhexidine is today commonly used as a step in the treatment. The aim of this study is to examine the additional effect of preoperative brushing with chlorhexidine gel on avoiding bacterial contamination during the installation of dental implants. Method: 30 patients participated in a randomized, double blinded study. 15 patients were included in the control group and 15 patients underwent an additional step in the treatment with a preoperative brushing with chlorhexidine gel. Bone samples and paperpoint samples were collected and analyzed in a laboratory and a statistic analysis was performed to compare the number of bacterial colonies in samples from the two groups (CFU/ml) present and the degree of contamination. Results: The mean bacterial count in bone samples from all patients in the control group was calculated at 8 126 CFU/ml and 2 946 CFU/ml in the test group. CFU/ml was different between the groups (P = 0.357) but the difference was not significant (P <0.05). Conclusion: Brushing with chlorhexidine gel preoperatively showed no significant effects in the bacterial contamination of bone chips. No recommendation for adding this additional step in the standard treatment with dental implants can therefore be made today.