Abstract
The aim of this study was to evaluate the effect of specific parameters of low-level laser therapy (LLLT) on biofilms formed by Streptococcus mutans, Candida albicans or an association of both species. Single and dual-species biofilms--SSB and DSB--were exposed to laser doses of 5, 10 or 20 J/cm(2) from a near infrared InGaAsP diode laser prototype (LASERTable; 780 ± 3 nm, 0.04 W). After irradiation, the analysis of biobilm viability (MTT assay), biofilm growth (cfu/mL) and cell morphology (SEM) showed that LLLT reduced cell viability as well as the growth of biofilms. The response of S. mutans (SSB) to irradiation was similar for all laser doses and the biofilm growth was dose dependent. However, when associated with C. albicans (DSB), S. mutans was resistant to LLLT. For C. albicans, the association with S. mutans (DSB) caused a significant decrease in biofilm growth in a dose-dependent fashion. The morphology of the microorganisms in the SSB was not altered by LLLT, while the association of microbial species (DSB) promoted a reduction in the formation of C. albicans hyphae. LLLT had an inhibitory effect on the microorganisms, and this capacity can be altered according to the interactions between different microbial species.
Highlights
The action of low-level laser therapy (LLLT) seems to be related to biostimulatory events [1]
The present study evaluated the effect of LLLT (780 nm) on singlespecies biofilms (SSB) and dual-species biofilms (DSB) of S. mutans and C. albicans, which are typical oral microorganisms [20] and are involved in the pathogenesis of diseases of high incidence, such as caries and candidiasis [14]
The protocols adopted in the present study showed a significant reduction in succinic dehydrogenase (SDH) production when S. mutans (SSB) was irradiated with a LLLL emitting at 780 nm
Summary
The action of low-level laser therapy (LLLT) seems to be related to biostimulatory events [1]. LLLT has been shown to have a significant bactericidal potential without causing damage to the oral tissues [3]. It has been shown that LLLT associated or not with a photosensitizer can cause destruction of oral bacterial and fungal species [7]. In these cases, the antibacterial mechanism of action of LLL seems to be related to thermal effects and photo-disruption [7]. LLLT may not cause immediate cell death, but it causes sublethal damages, such as destruction of the bacterial cell wall and accumulation of denatured protein in the bacterial cytoplasm [8]. Cytoplasmic accumulation of denatured proteins may induce cellular stress in an
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