Low intensity lasers differently induce primary human osteoblast proliferation and differentiation.

Among various compounds used in research and clinic for degenerative bone diseases, low level laser therapy (LLLT), comprising low level lasers (LLL) and light emitting diodes (LEDs), has been investigated regarding its effects on bone metabolism. They have specific wavelengths but in general act as a cellular biomodulator, and as a therapeutic agent, rebalancing and normalizing their activity. However, they are not standardized yet, since their parameters of use are relevant for the effects and mechanisms of action. Therefore, the aim of this study was to compare the influence of two spectrums of LLL and LED phototherapy, at the same energy densities (10 and 50J/cm(2)), on human osteoblasts proliferation and differentiation. The involvement of ERK signaling on proliferation was also investigated by evaluating its activation during proliferation under different phototherapies by western blotting and CFSE-based osteoblast proliferation was measured in a presence or absence of the ERK-specific inhibitor. Osteogenic differentiation was evaluated through in vitro mineralization and gene expression of type I collagen (COL1A1) and osteonectin (SPARC) by Real Time- PCR. Increases in viable cells and proliferation were obtained after irradiation, regardless of LLLT type. However, only red at 10J/cm(2) and infrared at both doses, but not LED, induced ERK1/2 activation. In the presence of ERK inhibitor, the LLL-induced proliferation was prevented. In addition, while COL1A1 gene expression was upregulated by red laser, SPARC does so by infrared stimulation. However, LED, at both doses, increased both COL1A1 and SPARC expression. All LLLT increased mineralization, dependent on the dose and time. Thus, LLL and LED differently modulated the metabolism of human osteoblasts, increasing proliferation by mechanism dependent or not of ERK signaling activation and osteogenic differentiation markers.

Photodynamic potential of curcumin and blue LED against Streptococcus mutans in a planktonic culture.

BACKGROUND: The photodynamic therapy (PDT) involves the use of light of specific wavelength to activate a nontoxic photosensitizing agent or dye in the presence of oxygen for eradication of target cells. In dentistry, this therapy is used to suppress the growth of microorganisms involved directly with dental decay and periodontitis process. There are evidences that curcumin dye is able to control microbial activity when illuminated with specific wavelength. The purpose of this study was to evaluate the in vitro efficacy of PDT using curcumin dye (Cur-C) in combination with a blue LED (L) device on a planktonic model of Streptococcus mutans (S. mutans). METHODS: Suspensions (0.5 mL) containing S. mutans at 1×10(7)CFU mL(-1) were prepared and divided into 4 groups: Group C-L- (control: no treatment and 1 experimental condition), Group C+L- (curcumin at 3 different concentrations: 2000; 4000 and 8000 µM and 3 experimental conditions), Group C-L+ (LED at 3 different dosages: 24, 48 and 72 Jcm(-2) and 3 experimental conditions), and Group C+L+ (PDT group: curcumin at respective concentrations combined to LED dosages and 9 experimental conditions). Samples of each experimental condition were cultured in Petri dishes of BHI agar. Incubation in micro-aerophilia at 37°C for 48 h was performed for subsequent visual counting of CFU/mL. Data were transformed into log10 and analyzed by two-way ANOVA and Tukey's test at p<0.05. RESULTS: Group C+L+, in specific experimental conditions, demonstrated a log bacterial reduction 70% higher than Group C-L-. Both groups C-L+ and C+L- presented a slight decrease in log bacterial counting. CONCLUSION: This in vitro method was able to reduce the number of S. mutans in a planktonic suspension.