Strategy for reducing cytotoxicity and obtaining esthetic efficacy with 15 min of in-office dental bleaching.

OBJECTIVES: Evaluate in vitro the esthetic efficacy and cytotoxicity of a bleaching gel containing 35% hydrogen peroxide (BG-35%H2O2), applied for different time intervals, on enamel coated or not with polymeric biomaterials. MATERIALS AND METHODS: Nanofiber scaffolds (NSc) and a primer catalyst (PrCa) were used to coat the bovine enamel/dentin discs before the application of BG-35%H2O2, according to the following groups: G1-negative control (NC, without treatment); G2, G3, and G4-BG-35%H2O2 applied for 3 × 15, 2 × 15, and 15 min; G5, G6, and G7-BG-35%H2O2 applied on enamel coated with NSc and PrCa for 3 × 15; 2 × 15, and 15 min, respectively. The culture medium with components of gel diffused through the discs was applied on MDPC-23 cells, which were evaluated regarding to viability (VB), integrity of the membrane (IM), and oxidative stress (OxS). The quantity of H2O2 diffused and esthetic efficacy (ΔE/ΔWI) of the dental tissues were also analyzed (ANOVA/Tukey; p < 0.05). RESULTS: Only G7 was similar to G1 regarding VB (p > 0.05). The lowest value of H2O2 diffusion occurred in G4 and G7, where the cells exhibited the lowest OxS than G2 (p < 0.05). Despite G5 showing the greatest ΔE regarding other groups (p < 0.05), the esthetic efficacy observed in G7 was similar to G2 (p > 0.05). ΔWI indicated a greater bleaching effect for groups G5, G6, and G7 (p < 0.05). CONCLUSION: Coating the dental enamel with polymeric biomaterials reduced the time and the cytotoxicity of BG-35%H2O2. CLINICAL SIGNIFICANCE: Coating the dental enamel with polymeric biomaterials allows safer and faster BG-35%H2O2 application.

Polymeric biomaterials maintained the esthetic efficacy and reduced the cytotoxicity of in-office dental bleaching.

Evaluate the kinetics of hydrogen peroxide (H2 O2 ) degradation, esthetic efficacy and cytotoxicity of a bleaching gel with 35%H2 O2 applied on enamel previously covered or not with polymeric nanofibrillar scaffold (SNan), polymeric primer catalyst (PPol), and both. Standardized enamel/dentin discs (n = 128) obtained from bovine teeth were adapted to pulp chambers. After covering enamel with the polymeric products, the bleaching gel was applied for 45 min, establishing the following groups: G1: no treatment (negative control); G2: 35%H2 O2 (positive control); G3: SNan; G4: PPol; G5: SNan + PPol; G6: SNan + 35%H2 O2 ; G7: PPol + 35%H2 O2 ; G8: SNan + PPol + 35%H2 O2 . The kinetics of H2 O2 degradation (n = 8), bleaching efficacy (ΔE/ΔWI; n = 8), trans-amelodentinal cytotoxicity (n = 8), and cell morphology (n = 4) were assessed (ANOVA/Tukey test; p < 0.05). Greater H2 O2 degradation occurred in G7 and G8. Bleaching efficacy (ΔE) was higher in G6, G7, and G8 in comparison with G2 (p < 0.05). However, no difference was observed for ΔWI (p > 0.05). G8 presented the lower level of trans-amelodentinal diffusion of H2 O2 , oxidative stress, and toxicity to the MDPC-23 cells (p < 0.05). Polymeric biomaterials increased the kinetics of H2 O2 decomposition, as well as maintained the esthetic efficacy and minimized the cytotoxicity caused by a bleaching gel with 35%H2 O2 . CLINICAL SIGNIFICANCE: Application of a bleaching gel with 35%H2 O2 on enamel previously covered by polymeric biomaterials maintains the esthetic efficacy and reduces the cytotoxicity caused by a single session of in-office dental bleaching.

Positive influence of simvastatin used as adjuvant agent for cavity lining.

OBJECTIVES: To assess the biological, antimicrobial, and mechanical effects of the treatment of deep dentin with simvastatin (SV) before application of a glass-ionomer cement (GIC). MATERIALS AND METHODS: Dentin discs were adapted to artificial pulp chambers and SV (2.5 or 1.0 mg/mL) was applied to the occlusal surface, either previously conditioned or not with EDTA (±EDTA). The extracts (culture medium + SV that diffused through dentin) was obtained and then applied to cultured odontoblast-like MDPC-23 cells. Cell viability, alkaline phosphatase (ALP) activity, and mineralization nodule (MN) deposition were evaluated. Untreated discs were used as control. The antibacterial activity of SV (2.5 or 1.0 mg/mL) against Streptococcus mutans and Lactobacillus acidophilus, as well as the bond strength of GIC to dentin in the presence of SV 2.5 mg/mL (±EDTA) were also assessed. The data were analyzed by ANOVA/Tukey tests (α = 5%). RESULTS: EDTA + SV 2.5 mg/mL significantly enhanced the ALP activity and MN deposition in comparison with the control, without changing in the cell viability (p < 0.05). The association EDTA + SV 2.5 mg/mL + GIC determined the highest ALP and MN values (p < 0.05). SV presented intense antimicrobial activity, and the EDTA dentin conditioning followed by SV application increased bond strength values compared with SV treatment alone (p < 0.05). CONCLUSION: SV presents antimicrobial activity and diffuses across conditioned dentin to biostimulate odontoblast-like pulp cells. CLINICAL SIGNIFICANCE: The use of SV as adjuvant agent for indirect pulp capping may biostimulate pulp cells thus preserving vitality and function of the pulp-dentin complex.

Influence of adhesive restorations on diffusion of H2O2 released from a bleaching agent and its toxic effects on pulp cells.

PURPOSE: To assess the influence of adhesive restorations on hydrogen peroxide (H2O2) diffusion through enamel and dentin and its cytotoxicity to pulp (MDPC-23) cells. MATERIALS AND METHODS: Sound and resin-restored enamel/dentin disks were stored in water for 24 h or 6 months and adapted to artificial pulp chambers. Bleaching gels with 20% or 35% H2O2 were applied to the enamel surface for 45 min, and a culture medium in direct contact with the dentin surface (extract) was applied for 1 h to the MDPC-23 cells. Cell metabolism (MTT assay) and cell morphology (SEM) were assessed. The amount of H2O2 in the extracts was also quantified (peroxidase/leuco-crystal violet reaction). RESULTS: A significant reduction in cell metabolism was observed between the group bleached with the 35% gel and the control group (sound, nonbleached) (p < 0.05). The H2O2 diffusion was directly related to its concentration in the bleaching gel. The variables "presence of restoration" and "time of water storage" did not significantly influence H2O2 diffusion or cell metabolism for either of the bleaching gels (p > 0.05). All bleached groups presented alterations in cell morphology related to the concentration of H2O2 in the bleaching gel. CONCLUSION: The reduction in cell metabolism and the changes in cell morphology were H2O2-concentration dependent, having no relationship with the presence of either new or aged adhesive restorations on teeth subjected to bleaching therapies.