Selective effect of blue light on multi-species biofilm grown on titanium surfaces

Objectives: The good biocompatibility of titanium metal in human tissue has favored its use as an implant material for the replacement of missing teeth. However, bacterial accumulation into biofilm on the surface of dental implants induces inflammatory changes in the tissues surrounding the implants, that may lead to their progressive destruction by peri-implantitis and ultimately to implant failure. Surface characteristics of implants complicate the conventional treatments, thus alternative antimicrobial approaches using light treatment have been suggested.
Objectives: To examine the effect of blue light treatment in bacterial population of multi- species biofilm grown on titanium surfaces in vitro.
Methods: Multi- species biofilm composed of four oral bacteria: Streptococcus sanguis, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis, were grown on titanium or hydroxyapatite surfaces and exposed to blue light. Biofilm structure and bacterial viability were examined immediately and 6h after light treatment by using the Confocal Scanning Laser Microscopy (CSLM) with live/dead staining. The four bacterial species were quantified immediately after light treatment using selective cultures for viable count test.
Results: Colony Forming Units (CFU) counting showed a significant decrease in the quantity of F.nucleatum after blue light treatment. The total amount of bacteria analyzed showed a similar quantity on the titanium and the hydroxyapatite disks, however, a smaller live/dead bacteria ratio was calculated on the titanium. On both surfaces, a reduction in live/dead bacteria ratio, meaning more dead cells, was observed immediately and 6h after light treatment. In addition, the antibacterial effect of the blue light was demonstrated through all the biofilm layers, and was not limited to surface only
Conclusions: These results indicate a possible enhanced selective susceptibility of bacteria in biofilm accumulated on titanium surfaces to blue light treatment. Blue light may be used for targeting specific periodontal pathogens, thus, potentially altering the equilibrium inside the biofilm