Influence of blue light on Streptococcus mutans re-organization in biofilm

► We examined new biofilms formed by previously exposed bacterial biofilm to blue light. ► Sublethal light dose does not interfere with bacterial capability to reform a new biofilm. ► A decrease in bacterial viability was found in the newly formed biofilms. ► Dead bacteria were mainly at the outer layers of the biofilm. ► Blue light has a delayed antibacterial effect on the re-organize bacteria in biofilm.