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Objective: To investigate the effects of quercetin (QU), hesperetin (HT), and taxifolin (TX) on human dental pulp cells (hDPCs) chronically exposed to lipopolysaccharide (LPS)., Methods: First, the cytotoxicity (alamarBlue) and bioactivity (biomineralization, Alizarin Red) of QU, HT, and TX concentrations were evaluated on healthy hDPCs. Then, the effects of non-cytotoxic and bioactive concentrations were investigated on hDPCs after previous stimulation with E. coli LPS (10 µg/mL) for 7 days. Cell culture media with and without LPS were used as positive and negative controls, respectively. Cell viability (alamarBlue), NF-κB activation (immunofluorescence), reactive oxygen species production (ROS, H2DCFDA probe), cell migration (Transwell), inflammation-related gene expression (RT-qPCR), and odontogenic differentiation (RT-qPCR and alizarin red) were evaluated (n = 8). Data were analyzed using confidence intervals and ANOVA (α = 5 %)., Results: The concentrations of 20 µM QU, 20 µM HT, and 200 µM TX reduced cell viability by more than 30 %. The 5 µM QU, 10 µM HT, and 100 µM TX concentrations were cytocompatible and stimulated biomineralization by healthy hDPCs. These concentrations were tested under the LPS challenge, and cell viability and odontogenic differentiation were significantly increased, while ROS production and inflammatory response were significantly decreased. In addition, the flavonoids significantly stimulated cell migration, reduced NF-κB activation, and increased biomineralization by LPS-challenged hDPCs compared to cells exposed to LPS alone and without any other treatment., Conclusion: Flavonoids can modulate the metabolism of hDPCs chronically exposed to LPS in vitro, stimulating cellular events compatible with stem cell-based regenerative processes., Clinical Significance: Flavonoids may be explored as adjuvant therapeutic agents during pulp capping to counteract chronic inflammatory conditions and stimulate regeneration of the dentin-pulp complex in caries-affected teeth, thereby preserving tooth vitality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Objective: This study investigated the bioactive effects of retinoic acid and ascorbic acid on hSCAPs in vitro., Design: Cells were obtained from human third molars (n=4) and characterized for mesenchymal stem cell markers by flow cytometry. The experimental groups: control (α-MEM); vehicle control group (α-MEM + 0.17 % DMSO); retinoic acid 0.1, 1, and 10 µM; and ascorbic acid 3, 30, and 300 µM (n=8) were tested for cell viability (alamarBlue; 1, 3, and 7 days), total collagen synthesis (Sirius Red; 1 and 7 days), mineralized matrix formation (Alizarin red; 14 days), and the regulation of gene expression related to mineralization (ALPL and DSPP), cell migration (ITGAV and CXCL12) angiogenesis (VEGFA) and collagen synthesis (COL1A1 and COL3A1; RT-qPCR) on 1 and 7 days. ACTB and GAPDH were used as reference genes. Data were analyzed by ANOVA and complementary tests at a 5 % significance level., Results: Ascorbic acid 300 µM increased viability, and retinoic acid reduced it dose-dependently. Retinoic acid 0.1 µM and ascorbic acid 30 and 300 µM increased mineralized matrix formation and total collagen synthesis, and retinoic acid 10 µM decreased. On day 1, 0.1 µM retinoic acid upregulated the gene expression of COL1A1, COL3A1, VEGFA, CXCL12, ALPL, DSPP e ITGAV, and 300 µM ascorbic acid upregulated COL1A1, COL3A1 and DSPP. However, on day 7, retinoic acid downregulated ALPL, COL3A1, CXCL12, and VEGFA and downregulated ITGAV and VEGFA., Conclusion: Retinoic acid 0.1 µM and ascorbic acid 300 µM biostimulated hSCAPs to differentiate into pro-regenerative phenotypes with potential application for REPs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objectives: To investigate the transdentinal effects of surface reaction-type pre-reacted glass-ionomer (S-PRG) fillers on odontoblast-like cells., Methods: An eluate of S-PRG fillers was obtained by dissolving the particles in distilled water (1:1 m/v). Dentin discs with similar permeability were mounted into artificial pulp chambers and MDPC-23 cells were seeded on their pulpal surface. The occlusal surface was treated with (n = 10): ultrapure water (negative control - NC), hydrogen peroxide (positive control - PC), S-PRG eluate exposure for 1 min (S-PRG 1 min), or S-PRG filler eluate exposure for 30 min (S-PRG 30 min). After 24 h, cell viability (alamarBlue) and morphology (SEM) were evaluated. The extract obtained from transdentinal diffusion was applied to MDPC-23 pre-cultured in plates for another 24 h to evaluate viability (alamarBlue, 1, 3, and 7 days), gene expression of Col1a1, Alpl, Dspp, and Dmp1 (RT-qPCR, 1 and 7 days), and mineralization (Alizarin Red, 7 days). Data were analyzed with ANOVA (α = 5 %)., Results: While S-PRG 1 min did not differ from NC, S-PRG 30 min reduced 17.9 % viability of cells from discs. S-PRG treatments resulted in low cell detaching from dentin, and the remaining cells exhibited typical morphology or minor cytoplasmic contraction. S-PRG 30 min slightly increased cell viability (6 %) 1 day after contact with the extract. S-PRG treatments upregulated the expression of the investigated genes, especially after 1 day. S-PRG 30 min stimulated mineralization activity by 39.7 %., Conclusions: S-PRG filler eluate does not cause transdentinal cytotoxicity on odontoblast-like cells, and long-term exposure can stimulate their dentinogenic-related mineralization activity., Significance: The transdentinal elution of ions from S-PRG fillers is not expected to be harmful to the dental pulp and may exert bioactive effects by inducing dentin matrix deposition through the metabolism of underlying odontoblasts., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: To evaluate whether coating enamel with a polymeric primer (PPol) containing titanium tetrafluoride (TiF 4 ) before applying a bleaching gel with 35% H 2 O 2 (35% BG) increases esthetic efficacy, prevents changes in morphology and hardness of enamel, as well as reduces the cytotoxicity from conventional in-office bleaching., Materials and Methods: Standardized enamel/dentin discs were stained and bleached for 45 min (one session) with 35% BG. Groups 2TiF 4 , 6TiF 4 , and 10TiF 4 received the gel on the enamel previously coated with PPol containing 2 mg/mL, 6 mg/mL, or 10 mg/mL, respectively. No treatment or application of 35% BG directly on enamel were used as negative control (NC), and positive control (PC), respectively. UV-reflectance spectrophotometry (CIE L*a*b* system, ΔE 00 , and ΔWI, n = 8) determined the bleaching efficacy of treatments. Enamel microhardness (Knoop, n = 8), morphology, and composition (SEM/EDS, n = 4) were also evaluated. Enamel/dentin discs adapted to artificial pulp chambers (n = 8) were used for trans-amelodentinal cytotoxicity tests. Following the treatments, the extracts (culture medium + bleaching gel components diffused through the discs) were collected and applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability (alamarBlue, n = 8; Live/Dead, n = 4), oxidative stress (n = 8), and morphology (SEM). The amount of H 2 O 2 in the extracts was also determined (leuco crystal violet/peroxidase, n = 8). The numerical data underwent one-criterion variance analysis (one-way ANOVA), followed by Tukey's test, at a 5% significance level., Results: Regarding the ΔE 00 , no difference was observed among groups 2TiF 4 , 6TiF 4 , and PC (p > 0.05). The ΔWI was similar between groups 2TiF 4 and PC (p > 0.05). The ΔWI of group 6TiF 4 was superior to PC (p < 0.05), and group 10TiF 4 achieved the highest ΔE 00 and ΔWI values (p < 0.05). Besides limiting enamel microstructural changes compared to PC, group 10TiF 4 significantly increased the hardness of this mineralized dental tissue. The highest cellular viability occurred in 10TiF 4 compared to the other bleached groups (p < 0.05). Trans-amelodentinal H 2 O 2 diffusion decreased in groups 2TiF 4 , 6TiF 4 , and 10TiF 4 in comparison with PC (p < 0.05)., Conclusion: Coating enamel with a PPol containing TiF 4 before applying a 35% BG may increase enamel microhardness and esthetic efficacy and reduce the trans-amelodentinal cytotoxicity of conventional in-office tooth bleaching. The PPol containing 10 mg/mL of TiF 4 promoted the best outcomes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objectives: To investigate the response of pulp cells to the application of silver diamine fluoride (SDF) and potassium iodide (KI) on demineralized dentin., Materials and Methods: The occlusal surfaces of human dentin discs (0.4 mm thick) with similar permeability were subjected to an artificial caries protocol, and then the discs were adapted into artificial pulp chambers. MDPC-23 cells were seeded on the healthy pulp dentin surface, while the demineralized surface was treated with SDF, KI, SDF + KI, or hydrogen peroxide (positive control-PC) (n = 8). The negative control (NC) received ultrapure water. After 24 h, cell viability (alamarBlue) and morphology (SEM) were evaluated. The extracts were then applied to new MDPC-23 cells seeded in culture plates to assess their viability and the formation of mineralized nodules (MN; Alizarin Red) after seven days. The data were analyzed using one-way analysis of variance/Tukey or Games-Howell tests (α = 5%)., Results: SDF and PC significantly reduced the viability of cells seeded on discs (45.6% and 71.0%, respectively). Only cells treated with SDF or PC detached from the dentin substrate, while the remaining cells showed altered morphology. Cells in contact with extracts showed less reduction in viability, but it was still more toxic compared to NC. Only PC reduced MN deposition. SDF + KI or KI alone did not affect the cell response., Conclusions: SDF applied alone showed a mild to moderate transdentinal cytotoxic effect on pulp cells. However, the combination of SDF + KI reduced the cytotoxic effects. Both materials used alone or in combination did not affect the mineralization ability of pulp cells., Clinical Relevance: Besides improving esthetic results, associating potassium iodide with silver diamine fluoride may reduce the transdentinal cytotoxic effects of this cariostatic agent on pulp cells., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Simulating a bacterial-induced pulpitis environment in vitro may contribute to exploring mechanisms and bioactive molecules to counteract these adverse effects., Objective: To investigate the chronic exposure of human dental pulp cells (HDPCs) to lipopolysaccharides (LPS) aiming to establish a cell culture protocol to simulate the impaired odontogenic potential under pulpitis conditions., Methodology: HDPCs were isolated from four healthy molars of different donors and seeded in culture plates in a growth medium. After 24 h, the medium was changed to an odontogenic differentiation medium (DM) supplemented or not with E. coli LPS (0 - control, 0.1, 1, or 10 µg/mL) (n=8). The medium was renewed every two days for up to seven days, then replaced with LPS-free DM for up to 21 days. The activation of NF-κB and F-actin expression were assessed (immunofluorescence) after one and seven days. On day 7, cells were evaluated for both the gene expression (RT-qPCR) of odontogenic markers (COL1A1, ALPL, DSPP, and DMP1) and cytokines (TNF, IL1B, IL8, and IL6) and the production of reactive nitrogen (Griess) and oxygen species (Carboxy-H2DCFDA). Cell viability (alamarBlue) was evaluated weekly, and mineralization was assessed (Alizarin Red) at 14 and 21 days. Data were analyzed with ANOVA and post-hoc tests (α=5%)., Results: After one and seven days of exposure to LPS, NF-κB was activated in a dose-dependent fashion. LPS at 1 and 10 µg/mL concentrations down-regulated the gene expression of odontogenic markers and up-regulated cytokines. LPS at 10 µg/mL increased both the production of reactive nitrogen and oxygen species. LPS decreased cell viability seven days after the end of exposure. LPS at 1 and 10 µg/mL decreased hDPCs mineralization in a dose-dependent fashion., Conclusion: The exposure to 10 µg/mL LPS for seven days creates an inflammatory environment that is able to impair by more than half the odontogenic potential of HDPCs in vitro, simulating a pulpitis-like condition.

Objectives: To evaluate the inhibitory activity of an ion-releasing filler (S-PRG) eluate on dentin collagen-bound metalloproteinases (MMPs) and dentin matrix degradation., Methods: Dentin beams (5 × 2 × 0.5 mm) from human molars were completely demineralized to produce dentin matrix specimens. The dry mass was measured, and a colorimetric assay (Sensolyte) determined the initial total MMP activity to allocate the beams into four treatment groups (n = 10/group): 1) water for 1 min (negative control); 2) 2% chlorhexidine digluconate (CHX - inhibitor control) for 1 min; 3) S-PRG eluate for 1 min; 4) S-PRG eluate for 30 min. After the treatments, the total MMP activity was reassessed. The specimens were stored in simulated body fluid (SBF) at 37 °C for up to 21 days. The dry mass was reassessed weekly. On day 7, the dentin matrix degradation was analyzed for the presence of collagen fragments (CF; Sirius Red) and hydroxyproline (Hyp) in the SBF. Statistical analyses were performed with ANOVA/Tukey, paired t-tests, and RM-ANOVA/Sidak (α = 5%)., Results: S-PRG eluate exposure for 1 and 30 min reduced (p < 0.0001) MMP activity. S-PRG exposure for 30 min presented MMP activity inhibition equivalent to CHX (p = 0.061). S-PRG and CHX decreased CF (p ≤ 0.007) and Hyp (p < 0.046) release. After 21 days of storage, S-PRG-treated beams, regardless of exposure time, presented a reduced (p ≤ 0.017) mass loss, intermediate between CHX and control., Conclusion: Treating demineralized dentin with S-PRG eluate for 1 or 30 min reduced matrix-bound MMP activity and dentin matrix degradation for up to 21 days., Clinical Significance: S-PRG filler may hinder the progression of dentin carious/erosive lesions and enhance the stabilization of dentin bonding interfaces., (Copyright © 2022 Elsevier Ltd. All rights reserved.)