Violet-blue light and streptococcus mutans biofilm-induced carious lesions

Abstract

Dental caries is a continuum of disease process. Early carious lesions are reversible and preventable. The primary etiological factor of dental caries is oral biofilm also known as dental plaque. It is an aggregate of oral bacteria, and one of the principal cariogenic bacteria is a facultative anaerobic microbe, Streptococcus mutans, which is indispensable for the initiation of caries. Management of prevention of carious lesions at the microbial level begins with reducing, eliminating and inhibiting the attachment of oral biofilm. Non-invasive phototherapy is widely studied to control oral biofilm as an alternative method to overcome the emergence of antibiotic resistant strains. In vitro studies demonstrated that Violet-Blue light with a peak wavelength of 405 nm had an inhibitory effect on S. mutans biofilm cells irradiated for 5 min. Metabolic activity of S. mutans cells was significantly reduced immediately after treatment with some recovery at 2 and 6 hrs. An in vitro translational study was conducted to determine the inhibitory effect of Violet-Blue light with twice daily treatments for 5 min over a period of 5 days on S. mutans biofilm cells grown on human enamel and dentin specimens. Bacterial viability was significantly reduced in the Violet-Blue light treated group for both dentin and enamel. Lesion depth, obtained by imaging fluorescence loss through Quantitative Light Induced Fluorescence (QLF-D) Biluminator and through transverse microradiography (TMR), was significantly reduced in S. mutans grown in tryptic soy broth with 1% sucrose (TSBS) for dentin. Mineral loss obtained through TMR in the absence of sucrose (TSB) was significant with enamel. However, all the parameters in the Violet-Blue treated groups were numerically reduced, albeit some being not significant. Accurate Mass Quadrupole Time of Flight Mass Spectrometry was used to identify Protoporphyrin IX (PP-IX) in S. mutans biofilm that may play a role in the photoinactivation and emission of fluorescence within specific wavelengths of the visible spectrum namely Violet-Blue light.