Violet LED Research Articles

Improved esthetic efficacy and reduced cytotoxicity are achieved with a violet LED irradiation of manganese oxide-enriched bleaching gels.

Gels with high concentrations of hydrogen peroxide (H2O2) have been associated with cytotoxicity and consequent post-bleaching tooth sensitivity. This study assessed the bleaching efficacy (BE) and cytotoxicity (CT) of bleaching gels with low concentrations of H2O2 containing manganese oxide (MnO2) and photocatalyzed with violet LED (LEDv). The following groups were established: G1: no treatment (negative control, NC); G2: 35% H2O2 (positive control, PC); G3: LEDv; G4: 10% H2O2; G5: 6% H2O2; G6: 10% H2O2 + MnO2 + LEDv; G7: 6% H2O2 + MnO2 + LEDv. To analyze BE, standardized enamel/dentin discs (E/DDs) were subjected to the bleaching procedures for 45min (1 session). The color change was determined before and after performing the bleaching protocols (ΔE00; ΔWI). To analyze CT, the E/DDs were adapted to artificial pulp chambers, and the extracts (culture medium + diffused gel components) were applied to cultured odontoblast-like MDPC-23 cells. Then, the cells were assessed concerning their viability (VB), oxidative stress (OxS), and Live/Dead. The amount of H2O2 diffused was also determined (ANOVA/Tukey; p < 0.05). Cell viability decreased in all bleached groups compared to G1 (NC; p < 0.05). The cells in G6 and G7 presented higher viability than in G2, G4, and G5 (p < 0.05). The BE in G7 was similar to G2 (PC; p < 0.05). The lowest OxS and H2O2 diffusion values were found in G6 and G7, compared to the other bleached groups (G2, G4, and G5; p < 0.05). The 6% H2O2 bleaching gel (G7) submitted to both methods of catalysis (MnO2 + LEDv) caused only a mild cytotoxicity and maintained the excellent esthetic outcome promoted by in-office conventional tooth bleaching.

Photoluminescent Properties of Phosphor Based on Perovskite CsPbBr3 Nanocrystals Combined with Violet Leds.

The characteristics of an LED lighting system consisting of a commercial violet LED and a green phosphor based on CsPbBr3 nanocrystals are studied in the context of development of LED illumination sources with antibacterial effects but without harmful effects on human health. The internal efficiency of the nanocrystalline phosphor in a silicone compound was found to exceed 40%, dropping noticeably because of heating for an electric current of ~0.1 A (phosphor excitation intensity ~0.1 W/mm2). This undesirable feature can be diminished by using a remote phosphor design for the illuminators and by using chemical techniques to improve the thermal stability of the nanocrystals.

(Invited) Advancing Human-Centric Lighting

The concept of human-centric lighting stems from the evolution of sunlight’s intensity and color temperature throughout the course of a day. This natural progression of bright cold-white light during the middle of the day to a softer warm-white light in the evening stimulates intrinsic photosensitive retinal ganglion cells that control our circadian rhythm. The blue-hue of daylight activates these cells to produce dopamine and cortisol while suppressing melatonin, the sleep hormone, to keep humans awake and alert. The current generation of energy-efficient LED lights reproduce daylight by converting a blue-emitting LED into a broad-spectrum white light using inorganic phosphors. Unfortunately, the resulting intense blue-hue generated by cheap LED bulbs and the underlying blue light from even the most expensive bulbs have been shown to cause macular degeneration, cataract formation, mood disorders, and circadian disruption, resulting in insomnia and fatigue. This talk will investigate the production of a ‘human-centric’ light that minimizes blue light by using a violet LED chip and inorganic phosphors. We report a new phosphor, Na2MgPO4F:Eu2+, which can be readily excited by violet light to produce a bright blue emission. This material possesses all the necessary requirements for LED lighting, including a high quantum yield, thermally robust emission, and impressive chemical stability. Incorporating this material into a prototype device demonstrates our ability produce a warm-white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component.

Far-red-emitting Cr3+-doped CaAl12O19 phosphors with excellent color purity and good quantum efficiency for plant growth LEDs

Single-phase far-red-emitting CaAl12O19:x%Cr3+ (x = 0.1 – 3.0 mol%) phosphors were successfully synthesized by a sol-gel method. Besides a small absorption peak at 263 nm, the phosphors have two broad excitation bands in the UV-blue (350 – 475 nm) and green-red (500 – 600 nm) regions, centered at 414 and 573 nm, respectively. They give a broad emission band in the 650 – 800 nm range and several narrow emission peaks at 665, 688, 695, 700, and 709 nm under violet (414 nm) and orange (573 nm) excitations. The optimum annealing temperature and doping concentration of Cr3+ ions are 1500 °C and 0.3%, respectively. Further, the optimized CAO: 0.3%Cr3+ phosphor exhibits an excellent color purity of 100%, activation energy of 0.4 eV, a long lifetime of 4.2 ms, and good quantum efficiency of 46.2%. A prototype of plant growth LED with the CIE coordinate of (x = 0.3050; y = 0.1264) was fabricated by coating CaAl12O19:0.3%Cr3+ phosphor on a violet (410 nm) LED chip. The obtained EL spectrum of plant growth LED is well-matched with the far red phytochrome (PFr) absorption spectra, demonstrating that CaAl12O19:Cr3+ is a potential far-red-emitting phosphor for violet-pumped plant growth LEDs.

New Possibilities on the Application of Violet Light in Dentistry Combining Aesthetics and Microbiological Control: Report of Two Clinical Cases

Dental bleaching performed in a dental office is considered among the bleaching techniques one of the most safety avoiding damages to the mucous membranes and to the gastrointestinal tract of the patient. The application of violet light appears as an innovative reality in dental bleaching with effective results. The aim of this study was to show the new possibilities of violet LED light (405 nm, 165 mW/cm2) with liquid peroxide solution used during the dental bleaching in two clinical cases. Dental bleaching was done using a violet LED light source and simultaneous irrigation used hydrogen peroxide liquid on the dental arches with the aim of also promoting oral decontamination in the patient. Based on the results, it was possible to show that violet light has real applicability in tooth whitening and potential to be used in oral decontamination. In addition, the violet light accelerates the whitening process allowing excellent results and minimizing the aggressiveness of this procedure to the patients. Thus, violet light is a new tool for tooth whitening with the advantage of combining the control and prevention of diseases initiated by microorganisms in the oral cavity.

Violet LED associated with high concentration hydrogen peroxide: Effects on bleaching efficacy, pH, and temperature

BackgroundThis study aimed to evaluate the bleaching efficacy, pH, and temperature of 35% hydrogen peroxide (HP) gel used alone or associated with violet LED. MethodsSixty bovine crowns were sectioned (5 × 5 × 2mm). After staining with black tea, the specimens were randomized into four groups (n = 10) according to the bleaching protocol: HP35R: 3 × 15 min 35% HP; HP35: 1 × 45 min 35% HP; HP35VR: 3 × 8min 35% HP + Violet LED; HP35V: 1 × 24 min + Violet LED. Two bleaching sessions were performed for all the groups. Color change was evaluated before, 24h after each session, 7 days and 15 days after the last session. The variables ∆E00 [CIEDE2000] and WID were used for color analysis. The pH variation (initial and final) and the temperature of the gel were recorded (n = 5). ANOVA two-way for repeated measures and Bonferroni post-test was used at a significance level of 5%. ResultsHP35VR and HP35V the most noticeable color change(p < 0.05). The final values of pH were lower than the initial ones, but with no difference between the groups (p > 0.05). Groups HP35VR and HP35V showed an increase in temperature in relation to HP35R (p < 0.05). ConclusionsViolet LED improved the bleaching efficacy of 35% HP in a time-saving manner without negatively affecting the pH and temperature of 35% HP. The renewal of HP did not influence the outcomes.

PHOTOLUMINESCENT PROPERTIES OF THE PEROVSKITE CsPbBr3 NANOCRYSTALS BASED PHOSPHOR COMBINED WITH VIOLET LEDS

In the context of development of LED luminaries with antibacterial effect but without harmful effects on human health, the characteristics of an LED lighting system consisting of a commercial violet LED and a green phosphor based on CsPbBr3 nanocrystals are studied. Internal efficiency of the nanocrystalline phosphor in a silicone compound was found to exceed 40% falling down noticeably because of heating for electric current of the order of 0.1 A (excitation intensity of the order of 0.1 W/mm2). This nondesirable feature can be diminished using remote phosphor design of luminaries as well as by rising thermal stability of nanocrystals with chemical techniques.

Direct dentin bleaching: Would it be possible?

This study aims to evaluate in vitro the effect of violet LED when applied directly to dentin tissue pigmented by different substances. We analyzed the chromatic alteration, the bleaching effect and the temperature variation. Hence, 60 bovine dentin tissue discs were divided into five groups: NNatural Pigmentation; T-Black Tea; C-Soluble Coffee; W-Red Wine; B-Equine Blood. Individualized pigmentation protocols were performed and all groups reached the same chromatic change value. Subsequently, we simultaneously performed a bleaching session and measured temperature variation using a K-type thermocouple device. Data on chromatic change (∆E, ∆E00, ∆a, ∆b and ∆L), whitening effect (WID) and temperature variation were subjected to one-way Anova and Tukey's post-test at a 5% significance level. The C group showed the most relevant chromatic change values, similar to the N group, responding positively to the treatment. However, the B group differed from the control group, which showed difficulty to respond to the treatment. Regarding the whitening index, only the W group showed lower results than the others. The B group showed the greatest temperature changes. We conclude that the violet LED offered chromatic change, which generated a bleaching effect. Pigmentations with red wine and blood showed the greatest difficulty to respond to treatment, also promoting a higher temperature rise in teeth pigmented with blood.

Prototype Measuring Levels of Dissolved Ammonia Based on TSL2561 Sensor Calibrated Thermo Scientific Genesys 30 Visible Spectrophotometer

In this study, a prototype measuring instrument for dissolved ammonia levels based on the TSL2561 sensor and calibrated thermo scientific Genesys 30 visible spectrophotometers has been realized, which aims to create a system for reading dissolved ammonia levels. This measuring instrument uses a violet LED as a light source, Arduino UNO as the central processor, and an I2C LCD to display measured values. This research was carried out by reading sensor tests on artificial instruments and spectrophotometer with dissolved ammonia samples with levels varying from 0-0.3 mg/l to obtain an equation for converting the absorbance value of the artificial measuring instrument into the dissolved ammonia level value, which was implemented in the Arduino program. Furthermore, an artificial measuring instrument is applied by measuring the dissolved ammonia level in the wastewater sample, namely the wastewater from the shrimp seeds tank, artemia tank, and tilapia tank. This measuring instrument has a measurement range from 0-0.3 mg/l. The sensor test results show that the greater the dissolved ammonia level, the greater the absorbance value. The results of the application of artificial measuring instruments obtained the value of dissolved ammonia levels in the wastewater of the shrimp seeds tank of 0.2811 mg/l, the wastewater of the artemia tank of 0.0672 mg/l, and the wastewater of the tilapia pond at 0.0156 mg/l. Based on the calculation results, it was obtained that the average accuracy and precision for the shrimp seeds tank wastewater was 98.63% and 98.47%, the Artemia tank wastewater was 97.72% and 98.08%, while for the pond wastewater tilapia by 95.71% and 99.74 %.

The influence of violet LED application time on the esthetic efficacy and cytotoxicity of a 35% H2O2 bleaching gel

ObjectiveTo assess the potential influence of violet LED (V-LED) application time on the esthetic efficacy and cytotoxicity of a 35% H2O2 bleaching gel. MethodologyStained and standardized enamel/dentin discs were subjected to one in-office tooth bleaching session (45 min), and the gel was either irradiated or not with V-LED. Thus, the following groups were established (n = 8): G1: No treatment (negative control, NC); G2: 35% H2O2 (positive control, PC); G3: 35%H2O2 + V-LED/15 min; G4: 35%H2O2 + V-LED/30 min; G5: 35%H2O2 + V-LED/45 min. First, esthetic efficacy was assessed (ΔE00 and ΔWI). Discs assembled in artificial pulp chambers were subjected to the same bleaching treatments. Then, the extracts (culture medium + diffused bleaching gel components) were collected and applied to MDPC-23 pulp cells, which were analyzed for viability (Live/Dead, MTT) and oxidative stress (OxS). The amount of H2O2 in the extracts was also determined (leuco crystal-violet/peroxidase). The data were subjected to ANOVA/Tukey at a 5% significance level. ResultsAlthough esthetic efficacy did not differ among the irradiated groups (G3, G4, and G5) (p > 0.05), their results were higher than in G2 (PC; p < 0.05). In the irradiated groups, the cell viability and OxS as well as the amount of H2O2 in the extracts were statistically similar to G2 (PC), regardless of irradiation time (p > 0.05). ConclusionAlthough V-LED improves the esthetic outcome of in-office tooth bleaching, increasing irradiation time does not effect the color changes and cytotoxicity of this professional therapy.

Symmetrically-substituted Thiazolo[5,4-d]thiazole derivatives as both photoinitiators and dyes for 3D printing under violet LED

The outstanding photochemical properties of thiazolothiazole and its derivatives make them attractive as potential photoinitiators. Two homosubstituted thiazolo[5,4-d]thiazole derivatives, 2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole and 2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole, were investigated as photoinitiators for both the free radical and the cationic polymerization upon the light irradiation from LED@410 nm. In particular, steady-state photolysis, fluorescence quenching experiments, and electron paramagnetic resonance spin-trapping techniques were used to study their photochemical mechanisms in generating active species. When coupled with one or two additives, these thiazolothiazole-based photoinitiating systems showed effective photoinitiation abilities on both the free radical and the cationic photopolymerization. Specifically, 2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole- and 2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-based photoinitiating systems were found to be of similar efficiency on the free radical photopolymerization of trimethylolpropane triacrylate and the dental resin (the blend of bisphenol A glycidyl methacrylate and triethylene glycol dimethacrylate) with minor shrinkage but presented different performance in cationic photopolymerization of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate. Moreover, the curing depth of the samples and 3D printing capability were also investigated to determine their potential applications.

Whitening efficacy of low concentration hydrogen peroxide photoactivated with blue or violet LED

BackgroundBleaching protocols using low concentration hydrogen peroxide (HP) photoactivated with LED sources have been widely discussed. Herein, we evaluated the whitening efficacy of 15% HP photoactivated with blue or violet LED compared to 35% HP. MethodsThirty bovine crowns were sectioned into 5 × 5 × 2 mm specimens. After staining in black tea, the specimens were randomized into three groups (n = 10): 35% HP, 15% HP + blue LED and 15% HP + violet LED. Two bleaching sessions were performed and the color assessment (∆L*, ∆a*, ∆b*, ∆Eab [CIELab], ∆E00 [CIEDE2000] and WID) was performed before, 24h after each session, 7 days and 1 month after the last session. Data were evaluated by two-way repeated measures ANOVA and Bonferroni post-test at a significance level of 5%. ResultsAll groups showed effective and similar results over 1 month of follow-up (p > 0.05), with only intragroup differences among the time intervals (p < 0.05). ConclusionsThe use of 15% HP photoactivated with blue or violet LED showed similar whitening efficacy compared to 35% HP. Thus, the association of low concentration bleaching gels with blue or violet LED sources can provide successful and less-aggressive treatment in terms of color change.

Hetero-valent substitution design of high thermal stability reddish-orange Sr3Ga2Sn1·5Si2·5O14:Sm3+ phosphor for healthy lighting white-light-emitting-diodes applications

In this paper, a novel violet excited reddish-orange emitting Sr3Ga2Sn1·5Si2·5O14:Sm3+ (SGSSO:Sm3+) phosphor with high thermal stability was designed and synthesized by the high temperature solid state reaction method for the first time. The photoluminescence (PL) properties of the SGSSO:Sm3+ phosphors were investigated systematically. Under 402 nm violet light excitation, SGSSO:Sm3+ phosphor shows reddish-orange emission at 598 nm that is attributed to the 4G5/2 → 6H7/2 transition of the Sm3+ ions. Importantly, the PL intensity of SGSSO:Sm3+ at 423 K can maintain 87% of the initial value at room temperature. The high thermal stability of Sm3+ in SGSSO was speculated to be attributed to the energy transfer mechanism of trap formed by the hetero-valent substitution of Sm3+ at Sr2+ sites. Finally, a WLED has been fabricated by combing the violet LED chip with the as-prepared reddish-orange emitting phosphor, commercial blue BaMgAl10O17:Eu2+ (BAM:Eu2+) and green (Ba,Sr)2SiO4:Eu2+ ((Ba,Sr)S:Eu2+) phosphors. The results indicated that the as-prepared SGSSO:Sm3+ phosphor can be a potential candidate of the reddish-orange component for violet chip pumped white-light-emitting-diodes.

Effectiveness of violet LED dental bleaching compared to 35% hydrogen peroxide: An in vitro study

AimThis in vitro study assessed the efficacy and adverse effects of violet LED bleaching with or without bleaching agents. Material and MethodsDental blocks (n=40) were randomly distributed in 4 groups: violet LED (VL), 35% hydrogen peroxide (HP35), the association of hydrogen peroxide 35% with violet LED (VHP35) and the association of hydrogen peroxide 35% with blue LED (BHP35). Specimens were analyzed for Vickers microhardness initially, immediately after and seven days after ending bleaching protocol. The color analysis of the specimens was evaluated for bleaching effectiveness (ΔE2000, ΔE1976) and whiteness index (ΔWID) with EasyShade spectrophotometer, before bleaching protocol and seven days after ending bleaching protocol. The mineral composition of the enamel was evaluated by percentage of phosphorus and calcium on the enamel surface with energy dispersive spectroscopy (EDS). The color and the microhardness data were analyzed using one-way ANOVA with post-hoc Tukey (α=0.05). ResultsThe microhardness test showed a difference among the groups only immediately after the completion of the protocol, in which there was a reduction in the value for the groups HP35 from 277,36 ± 21,56 to 198,76 ±32,2 (p<0,01); and BHP35 from 261,14 ± 36,01 to 212,66 ± 25,99 (p<0,01), but the microhardness was reestablished after seven days. Regarding EDS analysis, a reduction in the mineral percentage immediately after bleaching with the use of VL was observed, however, after seven days it was reestablished. Regarding the color analysis, there was no difference among the groups evaluated. ConclusionsThe use of VL was effective as a dental bleaching tool and did not adversely affect the enamel surface after seven days of the ending of the bleaching protocol.

Homogeneity of dental curing unit beam profile and its effect on microhardness of dental composites with varying thicknesses

ObjectivesThe dental curing unit (DCU) has been reported to emit inhomogeneous light. However, there are no studies on which elements could affect the inhomogeneity of DCUs. This study aimed to analyze the effect of attenuating factors such as the aperture of the lens or neutral density (ND) filters on the DCU's beam profile and evaluate the effect of DCU's inhomogeneous beam profile on the microhardness distribution on composite resin specimens with different thicknesses. MethodsRadiant emittance and spectrum of eight DCUs were investigated with and without ND filters using different optical density (OD) values. Beam profiles of eight DCUs were photographed while increasing the OD values of the ND filter. The change in the beam profile while changing the f-number of the aperture and the OD value of the ND filters were recorded. The Vickers microhardness of Filtek Z350XT and SDR cured by Bluephase Style 20i with 1, 2, 3, and 4 mm specimens of nine points on each surface was measured. ResultsIrradiance and spectrum of DCUs uniformly decreased after attenuation by the ND filters. The beam profile of the DCUs blurred when the f-number of the aperture was higher. The microhardness of Filtek Z350XT showed differences between the central and peripheral areas, and between the points under violet LED and the center on the bottom surface of the 4 mm specimen. The microhardness of the SDR did not show any differences. SignificanceThe inhomogeneity of the beam profile can be affected by attenuation conditions. DCU's inhomogeneous beam profile may have different effects on the composites depending on the thicknesses and types of composite resin used.

Influence of violet LED associated or not with peroxide gel on inflammation, mineralization, and collagen fiber maturation in dentin and pulp tissue

ObjectivesTo evaluate the influence of violet LED, associated or not with a 17.5% hydrogen peroxide (HP) bleaching gel, on inflammation, mineralization in pulp tissue, and collagen fiber maturation in dentin and pulp tissue. Materials and methodsThe maxillary molars of eighty Wistar rats were distributed into four groups (n = 10): CONT – without treatment; HP – 30 min application of 17.5% HP; LED – 20 min application of violet LED; and HP+LED – application of PH and violet LED. Rats were euthanized and jaws were processed for histologic and immunohistochemical evaluation (IL-17, IL-23, and osteocalcin) and picrosirius red immediately after (T0), and at 7 (T1), 15 (T2), and 30 days (T3) post-treatment, with Wilcoxon, Mann-Whitney, paired T-test, and T-test (α = 0.05). ResultsHP and HP+LED presented necrosis and severe inflammatory infiltrate. When compared to CONT group, LED presented severe osteocalcin (OCN) immunostaining in T2 and less immature fibers in T2 and T3. ConclusionThe violet LED caused no severe damage to the pulp tissue, increased IL-17 and IL-23 expression in T0 when associated with HP, and had no influence on pulp tissue mineralization, besides accelerating the maturation of collagen fibers of dentin. Clinical relevance: Violet LED therapy induced no inflammation in the pulp tissue of rats and played no role in pulp tissue fibrosis, besides accelerating the maturation of dentin collagen fibers.

Photoinactivation of Salmonella enterica exposed to 5-aminolevulinic acid: Impact of sensitization conditions and irradiation time.

The photodynamic inactivation (PDI) represents the potential alternative to traditional antibiotic therapy, and can be applied to treat various bacterial infections, including those caused by Gram-negative bacterial strains. One of the treatment modalities is based on the capacity of bacterial cells to synthesize the excess amounts of porphyrins after exposure to an externally applied 5-aminolevulinic acid (5-ALA), which makes them photosensitive and leads to reduced survival after irradiation with an appropriately selected light source. This study focuses on the sensitization and the photoinduced inactivation of Salmonella enterica cells in PBS containing 0.5mM 5-ALA, incubated at 37°C for 4h or for 20h and afterwards irradiated with violet LED light (11.1mW/cm2, a peak at 400nm). It has been found that both amounts and composition of endogenous porphyrins not only depended on the incubation duration, but also were affected by externally induced photo- and chemo-oxidation reactions. The application of different sensitization conditions has revealed that the increasing amounts of endogenously produced porphyrins do not ensure the proportional reduction of bacterial cell survival numbers. The comparative investigations also demonstrated that the presence of endogenously produced porphyrins in the medium results in secondary sensitization of bacterial cells and causes a notably stronger photoinactivation effect in comparison to their externally applied standards.

Bleaching effect of violet LED of 405–410 nm on stained endodontically treated teeth

AimTo evaluate in vitro the whiteness index (WID) and the whiteness index variation (ΔWID), as well as the color stability of stained endodontically treated teeth after bleaching with violet LED (VL) and with hydrogen peroxide 35% (HP) associated or not to VL. MethodsTwenty-four lower incisors were selected. The color was measured using a spectrophotometer at the following times: baseline, after staining, bleaching, and thermocycling, to determine the whiteness index and variation (WID and ΔWID). For the staining process, the teeth were immersed in human blood and centrifuged. After biomechanical preparation, the specimens were distributed into three groups (n = 8): control group (HP); violet LED (VL); and HP 35% + VL (HP+VL), and one session was performed for both bleaching procedures every week for three weeks, followed by thermocycling, where 10,000 cycles were performed. After color analysis, the data obtained were submitted to statistical analysis (RM ANOVA, p < 0,05). ResultsThe staining of the teeth reduced the WID values for all experimental groups compared to baseline, and the bleaching protocols increased WID values, with the lowest WID values for group VL. There was no statistically significant difference after thermocycling for all groups compared to bleaching. Staining and thermocycling reduced the ΔWID values, and no difference was found between treatments at these assessment times. Bleaching increased the ΔWID values, with less pronounced changes in the VL group. ConclusionVL used alone has a lower bleaching effect compared to the bleaching treatment with HP, whether or not associated with VL, and the color stability was observed for all groups.

Innovative strategy for in-office tooth bleaching using violet LED and biopolymers as H2O2 catalysts

ObjectiveTo assess the influence of coating the enamel with a nanofiber scaffold (NS) and a polymeric catalyst primer (PCP) on the esthetic efficacy, degradation kinetics of hydrogen peroxide (H2O2), and trans-amelodentinal cytotoxicity of bleaching gels subjected or not to violet-LED irradiation. MethodologyThe following groups were established (n = 8): G1- No treatment (negative control); G2- NS+PCP; G3- LED; G4- NS+PCP+LED; G5- 35% H2O2 (positive control); G6- NS+PCP+35% H2O2+LED; G7- 20% H2O2; G8- NS+PCP+20% H2O2+LED; G9- 10% H2O2; G10- NS+PCP+10% H2O2+LED. For esthetic efficacy analysis, enamel/dentin discs were stained and exposed for 45 min to the bleaching protocols. To assess the cytotoxicity, the stained enamel/dentin discs were adapted to artificial pulp chambers, and the extracts (culture medium + components diffused through the discs) were collected and applied to MDPC-23 cells, which had their viability, oxidative stress, and morphology (SEM) evaluated. The amount of H2O2 diffused and hydroxyl radical (OH•) production were also determined (two-way ANOVA/Tukey/paired Student t-test; p < 0.05). ResultsG6 had the highest esthetic efficacy compared to the other groups (p < 0.05). Besides the esthetic efficacy similar to conventional in-office bleaching (G5; p > 0.05), G10 also showed the lowest toxic effect and oxidative stress to MDPC-23 cells compared to all bleached groups (p < 0.05). ConclusionCoating the enamel with a nanofiber scaffold and a polymeric catalyst primer, followed by the application of 10%, 20%, or 35% H2O2 bleaching gels irradiated with a violet LED, stimulates H2O2 degradation, increasing esthetic efficacy and reducing the trans-amelodentinal toxicity of the treatment.

Influence of various types of light on growth and physicochemical composition of blueberry (Vaccinium corymbosum L.) leaves

It is important to use light that has a positive effect on plants. For plant growers, achieving the lowest possible cost of shrub production is crucial. We investigated the influence of light (white and violet LEDs as well as fluorescent white and red light) on the rooting and growth of blueberry cuttings (V. corymbosum L.) 'Aurora' and 'Huron'. Blueberry cuttings (4 cm tall) were planted into boxes with peat, which were placed in a phytotron at 22 °C and illuminated for 16 hours a day. The plants died under the red fluorescent light source and, therefore, we discontinued its use. The other three light sources had a positive effect on plant growth and development. The light source had little effect on the content of macroelements in the leaves. Plants grown under white fluorescent and white LED light did not significantly differ in the height (22.0-25.8 cm), proline (4.67-7.23 μmol g-1), and polyphenol content (4987-5212 mg 100 g-1). In both cultivars, the violet LED light reduced plant growth and increased the content of polyphenols (6,448 mg 100 g-1) and proline (8.11-9.06 μmol g-1) in the leaves, which may indicate abiotic stress. &#x0D; During the rooting of highbush blueberry cuttings, it is advisable to use white LED light. It has a positive economic impact on crop production due to low electricity consumption and it benefits the environment by eliminating mercury. The plant quality is similar to that of fluorescent white light.