Effects of phthalimidoperoxycaproic acid (PAP+) associated or not with LED irradiation as a bleaching agent: an in vitro study

This study evaluated the photoactivation of hydrogen peroxide gels at different concentrations using blue or violet LED in terms of whitening efficacy and tooth sensitivity. Forty patients were randomly divided into 4 groups: HP6V(violet LED and 6% hydrogen peroxide), HP6B(blue LED and 6% hydrogen peroxide), HP35V(violet LED and 35% hydrogen peroxide), and HP35B (blue LED and 35% hydrogen peroxide). The L*, a* and b* values were measured before, 1 week and 3 months after treatment, and the ΔE and ΔWID values were calculated. Tooth sensitivity was measured using a visual analogue scale (VAS) before, immediately after, and 24h after bleaching. The ΔE, ΔWID and bleaching sensitivity values were subjected to the ANOVA test and Bonferroni post-test. HP35V and HP35B showed higher whitening efficacy than HP6VL, while HP6V did not show statistical differences compared to the other groups. Regarding bleaching-related sensitivity, the HP6V and HP6B groups presented the lowest values when compared to HP35V and HP35B. HP6V showed whitening efficacy comparable to HP35V and HP35B but with reduced tooth sensitivity. TRIAL REGISTRATION NUMBER: NCT06165458; registration date: 12/09/2023.

Effects of tooth bleaching protocols with violet LED and hydrogen peroxide on enamel properties

Effectiveness and color stability of non-vital dental bleaching photoactivated by violet LED on blood-stained teeth

This study aims to conduct a single-blind randomized controlled trial to evaluate the bleaching efficacy and tooth sensitivity (TS) following the use of violet LED associated or not with 35% hydrogen peroxide. Eighty-four participants were randomly allocated into three groups according to bleaching treatments (n = 28): 35% hydrogen peroxide (HP) only, Violet LED only (VLED), and an association of 35% HP with violet LED (HP + VLED). Three sessions were performed, with an interval of seven days between each one. Changes in the objective (ΔEab and ΔE00) and subjective (ΔSGU) color and the Whiteness Index for Dentistry (ΔWID) were calculated based on before, and seven and thirty days after treatment using colorimetric measurements. Participants self-reported the risk and intensity of TS on a visual analogue scale (VAS). The color assessments seven and 30 days after bleaching were analyzed by two-way ANOVA and Tukey's test. The absolute TS risk was analyzed by Fisher's exact test. The significance level adopted was α = 0.05. HP and HP + VLED treatments showed higher and significant bleaching values (ΔEab, ΔE00, ΔSGU, and ΔWID) compared to VLED. The HP + VLED and HP groups presented a higher risk and intensity of TS compared to the VLED group (p < 0.05). The bleaching efficacy of VLED alone was lower compared to the HP and HP + VLED protocols both seven and 30 days after the end of treatments.

Hydrogen peroxide (HP) at 35% is effective for dental bleaching but may reduce enamel mineral content and induce structural changes. This study developed a bleaching-hydrogel containing 6%HP and manganese-oxide-doped Biosilicate (MnO_BioS), activated by violet LED, under in situ conditions. Pigmented enamel blocks were attached to palatal devices (n=12) and kept intraorally for 15 days, being removed only for bleaching sessions. Experimental groups were as follows: 35%HP (positive control) and 6%HP gel containing BioS or MnO_BioS (0/10wt%), with or without violet LED irradiation. Bleaching consisted of three 30-min sessions with 7-day intervals. Color change (ΔE00), whiteness index (ΔWID), color coordinates (ΔL*, Δa*, Δb*), surface hardness recovery (%SHR), and enamel inorganic content (CO3 2-/PO4 3- ratio by Fourier-transform infrared) were evaluated at baseline (T0) and after treatment (T1), with scanning electron microscopy analysis at T1. Data were analyzed using analysis of variance and Tukey's-test (α=0.05). 6%HP_MnO_BioS_LED showed the highest bleaching effectiveness (ΔE00=8.90±1.18; ΔWID=20.86±3.26), surpassing 35%HP in ΔWID (15.53±1.33) and showing comparable ΔE00 (6.48±1.81). MnO_BioS groups increased enamel CO3 2-/PO4 3- ratios after bleaching (0.475±0.02; 0.466±0.01) compared with baseline (0.431±0.01; 0.429±0.01; p<0.05). Hardness recovery improved (%SHR=4.14±1.88; 5.45±2.54), whereas it decreased in 35%HP (-1.32±1.67) and 6%HP_LED (-2.60±0.96). 6%HP hydrogel containing MnO_BioS activated by violet LED enhanced bleaching efficacy while preserving enamel mineral-related parameters.

Color stability of dental enamel bleached with violet LED associated with or without Low concentration peroxide gels.

The aim of this study was to evaluate in vitro color change, surface morphology and mineral content of enamel submitted to bleaching with violet LED(LED) combined or not with 35% hydrogen(HP) or 37% carbamide peroxide(CP). Bovine crowns stained with black tea were randomly distributed into whitening groups(n=10): LED/HP, HP, LED/CP, CP, LED and C – control. Color change(?E, ?L, ?a e ?b) was spectrophotometrically determined among staining and 14 days elapsed from bleaching. Enamel surface was analyzed by means of SEM. Sixty additional enamel blocks were obtained, polished and submitted to initial surface michorhardness(KHN) for selection. One week elapsed from interruption of same protocols, calcium to phosphorous ratio(Ca/P) was determined under ?-EDXRF spectrometry. ?E, ?L and Ca/P ratio were tested with two-way ANOVA and Tukey’s test. ?a e ?b were evaluated under Kruskal-Wallis and Mann-Whitney tests(?= 5%). Although ?E and ?b were comparable among LED/HP and HP(p>0.05), CP’s was lower than LED/CP(p<0.05). ?E, ?L, ?a and ?b for LED were significantly higher than C(p<0.05). Even though whitening gels provoked irregularities, depressions and affected interprismatic spaces of enamel, LED did not exacerbate such condition. Even though CP’s Ca/P was significant lower than C, LED did not influence impact of gels on Ca/P. Thus, LED enhanced the effectiveness of only CP at the same time it did not exacerbate enamel surface and mineral changes caused by high-concentrated gels.

Evaluation of photoluminescence from milk with various vitamin B2 concentrations

This study evaluated the influence of hydrogen peroxide (HP) with or without titanium dioxide nanotubes (TiO2) associated with violet LED (VL) regarding: a) the temperature change in the pulp chamber and facial surface; b) the decomposition of HP; and c) the cytotoxicity of the gels on pulp cells. The experimental groups were: HP35 (35% HP/Whiteness HP, FGM); HP35+VL; HP35T (HP35+TiO2); HP35T+VL; HP7 (7.5% HP/White Class 7.5%, FGM); HP7+VL; HP7T (HP7+TiO2); and HP7T+VL. TiO2 was incorporated into the bleaching gels at 1%. Eighty bovine incisors were evaluated to determine temperature change in 8 experimental groups (n=10/group). A k-type thermocouple was used to evaluate the temperatures of the facial surface and in the pulp chamber, achieved by enabling endodontic access to the palatal surface, throughout the 30-minute session. HP decomposition (n=3) of gels was evaluated by using an automatic potentiometric titrator at the initial and 30-minute time points. Trans-enamel and trans-dentinal cell viability were assessed with a pulp chamber device as well as enamel and dentin discs (n=6), and the treatment extracts (culture medium + diffused components) were collected and applied to MDPC-23 odontoblast cells to evaluate cell viability according to the MTT test. A temperature increase in the pulp chamber was observed in the presence of VL at 30 minutes (p<0.05) (Mann-Whitney test). Also at 30 minutes, HP35 showed greater decomposition in the presence of VL rather than in its absence (p<0.05) (mixed linear models and the Tukey-Kramer test). HP7 provided greater cell viability than the groups treated with HP35 (p<0.05) (generalized linear models test). Cell viability was significantly lower for HP7 in the presence of VL (p<0.05). Pulpal temperature increased with VL (maximum of 1.9°C), but did not exceed the critical limit to cause pulp damage. Less concentrated HP resulted in higher cell viability, even when associated with VL.

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

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

This study evaluate the effect of whitening with violet LED (LED) combined or not with 37% carbamide (CP) or 35% hydrogen peroxide on enamel stained with cigarette smoke (SK), coffee (CF) and red wine (RW). Bovine dental blocks were obtained and stained with extrinsic pigments (n=50): SK, CF, RW or control (C). Specimens were whitened following protocols: LED, LED/CP, CP, LED/HP or HP. Color change (DE) was measured considering after staining (T0), 24 hours elapsed from bleaching (TB) and 7 days after treatments (T7) times by means of spectrophotometry. Data was tested by two-way ANOVA and Tukey’s Test. Enamel’s surface morphology was analysed under scanning electron microscope (SEM). Regardless of the extrinsic pigment, LED promoted statistically greater DE for stained groups in comparison to C (p 0.05), but for CF (p=0,020). LED/HP DE was significantly higher than HP only for CF (p=0.012). Outcomes were mantained after seven days. Topography of enamel suffered alterations under peroxides, but this was not exacerbated by LED irradiation. Effectiveness of LED alone on tooth whitening is enhanced in the presence of extrinsic pigments. Violet LED influenced effectiveness of CP and HP depending on staining type. LED did not change patterns of enamel surface morphology.

Chemical, morphological and microhardness analysis of coronary dentin submitted to internal bleaching with hydrogen peroxide and violet LED

The aim is to evaluate the effect of violet light (VL) and nonthermal atmospheric plasma (NTAP) combined with or without 35% hydrogen peroxide (HP) and 37% carbamide peroxide (CP). Bovine crowns were divided into (n = 10) VL, VL/HP, VL/CP, NTAP, NTAP/HP, NTAP/CP, HP, CP, and C (control) groups. Color and whiteness change (CIELAB-Δ Eab, CIEDE2000-Δ E00 , whiteness index-ΔWID ), color parameters (ΔL, Δa, and Δb), and intrapulpal concentration (μL/mL) of HP were assessed by spectrophotometry. Scanning electron microscopy evaluated the morphology of enamel surface. Data were analyzed by two-way analysis of variance and Tukey (Δ Eab , ΔE00 , ΔWID , ΔL, and μL/mL) and Kruskal-Wallis and Mann-Whitney tests (Δ a and Δ b, α = 5%). VL increased ΔEab and ΔWID of CP (P < .05). VL and NTAP alone resulted in perceptible color and whiteness change, but lower than those in the gel-treated groups (P < .05). Activation modes increased ΔL compared with that of C, but only VL enhanced Δb when applied alone or combined with CP. VL and NTAP did not increase HP diffusion (P > .05) or cause alterations in enamel morphology. However, HP and CP promoted topographical changes. VL and NTAP changed color to a lesser extent than bleaching gels. VL produced supplementary effectiveness only for CP (ΔEab and ΔWID ), without increasing HP diffusion or changing enamel morphology. Although violet LED light and nonthermal atmospheric plasma (NTAP) promoted in vitro perceptible bleaching without compromising enamel morphology, bleaching gels (hydrogen peroxide and carbamide peroxide) were more effective than VL or NTAP. VL or NTAP did not increase intrapulpal diffusion of peroxide.

Although hydrogen peroxide (HP) at 35% is effective in dental bleaching, the cytotoxicity associated with its use remains a significant concern. In this context, this study aimed to develop a bleaching hydrogel containing 6% HP, Biosilicate® (BioS) doped with manganese oxide (MnO_BioS), and irradiated with violet LED light (LED). Enamel/dentin discs were submitted to the following bleaching treatments (n=08): 35%HP (positive control), 6%HP gel containing BioS or MnO_BioS (0 and 10 wt%), with or without LED irradiation. The discs were adapted to artificial pulp chambers (APCs), with the enamel exposed for bleaching and the dentin facing the culture medium (DMEM). Bleaching was performed in three 30-minute sessions with 7-day intervals. After bleaching, the extracts (DMEM + bleaching gel components diffused through the discs) were collected and applied to the odontoblast-like MDPC-23 cells. Color change (ΔE00) and changes in the whiteness index (ΔWID) were determined before (T0) and after the last bleaching session (T2). Cell viability (MTT, %), HP diffusion (µg/mL), oxidative cell stress (OxS), and cell fluorescence (live/dead assay, by confocal microscopy) were assessed after the first session (T1). The data were analyzed using ANOVA and Tukey's test (p=0.05). The addition of 6%HP_MnO_BioS_LED exceeded ΔWID compared to 35%HP, showing statistical differences from the other groups, while ΔE00 was statistically similar to 35%HP. 6%HP_MnO_BioS_LED demonstrated higher cell viability, lower HP diffusion, and reduced oxidative stress (OxS) compared to the other groups (p<0.05). 6%HP_MnO_BioS_LED increased bleaching potential and presented lower cytotoxicity compared to 35%HP.