Response of pulp cells to resin infiltration of enamel white spot-like lesions

ObjectivesTo investigate the trans-enamel and trans-dentinal biological effects of treating enamel white spot-like lesions (EWSLs) with resin infiltration components (RICs) on odontoblast-like cells (MDPC-23) and human dental pulp cells (HDPCs).MethodsEWSLs were induced in 60 enamel/dentin discs (4.0 ± 0.2 mm thick) using S. mutans. The discs were adapted into artificial pulp chambers and MDPC-23 were seeded on the dentin surface. The components of a resin infiltration system (Icon) were applied individually or in combination on the enamel surface as following (n = 10/treatment): Etch, Infiltrant, Etch+Infiltrant, or Etch+Dry+Infiltrant. The application of water or hydrogen peroxide served as negative and positive controls, respectively. After 72 h, MDPC-23 viability was evaluated. The extracts were exposed for 72 h to pre-cultured MDPC-23 and HDPCs in 96-well plates to evaluate cell viability, alkaline phosphatase activity (ALP), mineralized nodule formation (MN), and the expression of inflammatory cytokines (ICs) and mineralization-related genes (MRs). Data were analyzed by ANOVA complemented with Tukey or Games-Howell post-hocs (α = 5%).ResultsCell viability, ALP activity, and MN formation were significantly reduced in response to the RICs, presenting intermediate values compared to positive and negative controls. Likewise, ICs were upregulated, whereas MRs were downregulated. Among the RICs, the Etch component caused the most notorious detrimental effects.SignificanceResin infiltration of EWSLs negatively affected the metabolism of pulp cells in vitro. Therefore, even though resin infiltration is a micro-invasive therapy for non-cavitated caries in enamel, it should be closely followed up seen that components may diffuse and unbalance pulp homeostasis.     

Biocompatibility of resin-based dental materials applied as liners in deep cavities prepared in human teeth

BACKGROUND: Since only a few data have been published concerning the effects of resinous dental materials on the pulp-dentin complex, the aim of this study was to evaluate the biocompatibility of resin-based materials applied as liners in deep cavities prepared in human teeth. METHODS: After preparing class V cavities, the following dental materials were applied on the axial walls: group 1, Vitrebond (VIT; 3M ESPE); group 2, Ultra-Blend Plus (UBP; Untradent); and group 3, Clearfil SE Bond (CSEB; Kuraray). In group 4 (control), the hard-setting calcium hydroxide cement Dycal (CH; Caulk/Dentsply) was used. The teeth extracted at 7 days or between 30 and 85 days after the clinical procedures were processed for histological evaluation. RESULTS: For all the experimental and control groups, most of specimens exhibited no pulpal response or slight inflammatory reaction associated with slight tissue disorganization at 7-day period. Moderate inflammatory pulpal response occurred only in one tooth (RDT = 262 microm) of group 3 in which transdentinal diffusion of resin components was observed. CONCLUSION: The resin-based dental cements VIT and UBP as well as the bonding agent CSEB presented acceptable biocompatibility when applied in deep cavities prepared in sound human teeth.     

Bleaching effectiveness,hydrogen peroxide diffusion,and cytotoxicity of a chemically activated bleaching gel

Objectives

The objective of this study was to evaluate the bleaching effectiveness, hydrogen peroxide diffusion (H₂O₂), and cytotoxicity of a bleaching gel with 35 % H₂O₂ either associated with ferrous sulfate (FeSO₄) or not.

Materials and methods

Enamel/dentin discs adapted to artificial pulp chambers were placed in compartments containing a culture medium (Dulbecco's Modified Eagle's Medium (DMEM)) and distributed into the following groups: G1—no treatment (negative control), G2—10 % carbamide peroxide (one application for 4 h), G3—35 % H₂O₂ (three applications for 15 min), and G4—35 % H₂O₂ + 0.004 g FeSO₄ (three applications for 15 min). After treatments, the extracts (DMEM + bleaching components that diffused across enamel and dentin) were applied on human dental pulp cells (HDPCs) and odontoblast-like cells (MDPC-23). Cell viability (MTT assay, Kruskal–Wallis and Mann–Whitney, α?=?5 %), quantification of H₂O₂ diffusion, and color change of the enamel/dentin discs (Commission Internationale de I'Eclairage L*a*b* system) were assessed (analysis of variance and Tukey's tests, α?=?5 %).

Results

For both cells, a significant reduction in cell viability was observed for G3 and G4 compared with G1 and G2. No statistical difference was observed between G3 and G4. The rate of H₂O₂ diffusion was significantly higher in G3 compared with that in G2 and G4. The ΔE value for G4 was statistically higher than that of the other groups.

Conclusions

Chemical activation of H₂O₂ by FeSO₄ improves the bleaching effectiveness. However, this metal ion has no significant protective effect against pulp cell cytotoxicity.

Clinical relevance

Although the chemical activation of H₂O₂ by adding FeSO₄ to the bleaching agent improved the bleaching effectiveness, this metal ion has no significant protective effect against pulp cell cytotoxicity.     

Transdentinal cytotoxicity of resin-based luting cements to pulp cells

Objectives

The aim of this study was to evaluate the transdentinal cytotoxicity of components released from different resin-based luting cements to cultured MDPC-23 odontoblast-like cells and human dental pulp cells (HDPCs).

Materials and methods

Artificial pulp chamber (APC)/dentin disc sets were distributed into four groups according to the materials tested (n = 10), as follows: G1, control (no treatment); G2, resin-modified glass-ionomer cement (RelyX Luting 2); G3, self-adhesive resin cement (RelyX U200); and G4, conventional resin cement (RelyX ARC). The materials were applied to the occlusal surfaces (facing up) of the dentin discs adapted to the APCs. The pulpal surfaces of the discs were maintained in contact with culture medium. Then, an aliquot of 400 μL from the extract (culture medium + resin-based components that diffused through dentin) of each luting cement was applied for 24 h to HDPCs or MDPC-23 cells previously seeded in wells of 24-well plates. Cell viability analysis was performed by the MTT assay (1-way ANOVA/Tukey test; α = 5 %).

Results

For MDPC-23 cells, RelyX ARC (G4) and RelyX Luting 2 (G2) caused greater reduction in cell viability compared with the negative control group (P < 0.05). Only the HDPCs exposed to RelyX ARC (G4) extract showed a tendency toward viability decrease (9.3 %); however, the values were statistically similar to those of the control group (G1) (P > 0.05).

Conclusions

In accordance with the safe limits of ISO 10993-5:1999 (E) recommendations, all resin-based luting cements evaluated in this study can be considered as non-toxic to pulp cells.

Clinical relevance

Cytotoxicity of resin-based luting cements is material-dependent, and the different protocols for the application of these dental materials to dentin may interfere with their cytotoxicity.

     

Effect of dentin conditioners on the microtensile bond strength of a conventional and a self-etching primer adhesive system.

OBJECTIVE: To investigate the effect of different dentin treatments on the microtensile bond strength of a self-etching primer and a simplified, total-etch adhesive system. METHODS: Flat dentin surfaces were created on extracted human third molars. The surfaces were treated with one of the following conditioners: self-etching primer for 20 s (Clearfil SE Primer), 37% phosphoric acid for 15 s or 0.5 M EDTA for 30 s. Conditioned surfaces were then bonded with either Clearfil SE Bond or Single Bond followed by resin composite (Z250) build-ups constructed incrementally. Application of SE Primer was included when Clearfil SE Bond was used, after phosphoric acid and EDTA conditioning. After 24 h storage in water at 37 degrees C, the teeth were longitudinally sectioned across the bonded interface to produce beams with 1.0 mm2 of adhesive area, tested with the microtensile method at a rate of 0.5 mm/min. Data were analyzed using two-way ANOVA and Tukey's test. RESULTS: The highest bond strength mean was found for the combination SE Primer/Single Bond (58.5+/-20.8 MPa), followed by the EDTA/Clearfil SE Bond (47.8+/-15.1 MPa) and phosphoric acid/Single Bond (40.9+/-14.3 MPa). The remaining combinations showed statistically similar (p>0.05) tensile bond strength. SIGNIFICANCE: The bond performance of the adhesives tested was dependent on the dentin conditioner. Pre-treatment with a mild etchant such as 0.5 M EDTA improved the bond strength of Clearfil SE Bond. Single Bond performed better when a self-etching primer was used as the dentin conditioner, probably by preventing the formation of a defective zone at the base of the hybrid layer. Overall results indicate that higher bond strengths can be achieved by conditioning dentin with milder etchants, suggesting that deeper demineralization may prevent proper resin infiltration, hence compromising the bond.     

Positive influence of simvastatin used as adjuvant agent for cavity lining

Clinical Oral Investigations - To assess the biological, antimicrobial, and mechanical effects of the treatment of deep dentin with simvastatin (SV) before application of a glass-ionomer cement...     

Cytotoxic effects of different concentrations of chlorhexidine

PURPOSE: To evaluate the cytotoxic effects of different concentrations of Chlorhexidine (Chx) to the odontoblast cell line MDPC-23. METHODS: The odontoblast-like cells were seeded (30,000 cells/cm2) in 60 wells of 24-well dishes and then incubated in contact with the following experimental and control solutions: Group 1: 0.0024% Chx; Group 2: 0.004% Chx; Group 3: 0.02% Chx; Group 4: Phosphate buffer saline solution (PBS, negative control); and Group 5: 0.06% H2O2 (positive control). Cell metabolic activity was measured by MTT assay and the cell morphology was analyzed by SEM. RESULTS: The cytotoxic effects of Chx are dose-dependent. The reduction in the cell metabolism for Groups 1, 2, and 3 was 24.8%, 29.9% and 70.8%, respectively. No statistical difference was observed between the Groups 1 and 2 in which no significant cell morphology changes occurred. Consequently, it was concluded that 0.02% Chx solution presents high cytotoxicity to the odontoblast-like cells MDPC-23. On the other hand, 0.0024% and 0.004% Chx causes slight cytopathic effects to the cultured cells.