A new approach for professional dental bleaching using a polymeric catalyst primer.

OBJECTIVE: Evaluate the influence of a polymeric catalyst primer (PCP) on esthetic efficacy (EE), degradation kinetics of hydrogen peroxide (H2 O2 ), and trans-amelodentinal cytotoxicity (TC) of bleaching gels. MATERIALS AND METHODS: The following groups were established: G1: No treatment (NC, negative control); G2: PCP; G3: 10% H2 O2 ; G4: PCP + 10% H2 O2 ; G5: 20% H2 O2 ; G6: PCP + 20% H2 O2 ; G7: 35% H2 O2 (positive control); G8: PCP + 35% H2 O2 . To determine EE, enamel/dentin discs (E/DDs) were stained and subjected or not to bleaching protocols for 45 min. To assess TC, the E/DDs were adapted to artificial pulp chambers. The extracts (culture medium + gel components diffused through E/DDs) were applied to odontoblast-like MDPC-23 cells. The viability (VB), oxidative stress (OxS), morphology (SEM), amount of H2 O2 diffused and the production of hydroxyl radical (OH• ) were assessed (two-way ANOVA/Tukey/paired Student t-test; p < 0.05). RESULTS: The highest EE was found in G8 (p < 0.05), and G4, G6, and G7 did not differ statistically (p > 0.05). In G4, the limited H2 O2 diffusion reduced OxS and increased cell VB (p < 0.05). CONCLUSIONS: Coating the enamel with PCP containing 10 mg/ml of manganese oxide before applying the 10% H2 O2 bleaching gel maintains the EE of conventional in-office bleaching and minimizes the toxic effects of this esthetic therapy. CLINICAL SIGNIFICANCE: Coating the enamel with a PCP before applying the bleaching gel may potentiate the EE of the conventional in-office tooth bleaching and reduce the toxicity of this professional therapy to the dental pulp.

Proteolytic activity, degradation, and dissolution of primary and permanent teeth.

BACKGROUND: Primary and permanent teeth composition may influence dissolution and degradation rates. AIM: To compare the dissolution and degradation of primary and permanent teeth. DESIGN: Enamel and dentin powders were obtained from primary molars and premolars and incubated within different pH buffers. Calcium and inorganic phosphate release was quantified in the buffers by atomic absorption and light spectrophotometry. A colorimetric assay was used to assess the MMP activity of primary dentin (PrD) and permanent dentin (PeD). Collagen degradation was assessed by dry mass loss, change in elastic modulus (E), and ICTP and CTX release. Data were submitted to ANOVA and Tukey's tests (α = 0.05). RESULTS: Similar dissolution was found between PrD and PeD after 256 hours. At pH 4.5, enamel released more minerals than dentin whereas at pH 5.5 the inverse result was observed. MMP activity was similar for both substrates. PrD showed higher dry mass loss after 1 week. In general, greater reduction in E was recorded for PrD. Higher quantities of ICTP and CTX were released from PrD after 1 week. CONCLUSIONS: Primary and permanent teeth presented similar demineralization rates. Collagen degradation, however, was faster and more substantial for PrD.

Photodithazine-mediated antimicrobial photodynamic therapy against fluconazole-resistant Candida albicans in vivo.

This study evaluated the efficacy of antimicrobial Photodynamic Therapy (aPDT) against fluconazole-resistant Candida albicans in a murine model of oral candidosis. Mice were inoculated with two clinical isolates (R10, R15) and one reference strain (ATCC) of resistant C. albicans to produce oral candidosis. After inoculation, aPDT mediated by Photodithazine® (PDZ) and LED light was performed. The use of PDZ or light only was also investigated. Additional animals were treated with Nystatin (NYS). Untreated or healthy mice were also evaluated. Microbiological evaluation was performed by recovering C. albicans from the tongue via colony-forming units. Animals were killed 24 hours after treatments, and the tongues were removed for histological analysis. Data were analyzed by one-way ANOVA and Tukey test (P < .05). The results demonstrated that all strains showed the same behavior after aPDT and NYS treatment. A significant reduction in C. albicans viability was achieved after both treatments for R15 and ATCC. No significant reduction was verified for C. albicans R10 submitted to aPDT or NYS. The histological analysis revealed that aPDT did not cause side effects on tissues. aPDT was effective for inactivation of two fluconazole-resistant C. albicans of the three strains evaluated.

Responses of dental pulp cells to a less invasive bleaching technique applied to adhesive-restored teeth.

PURPOSE: To assess the cytotoxicity of 35% hydrogen peroxide (HP) bleaching gel applied for 15 min to sound or restored teeth with two-step self-etching adhesive systems and composite resin. MATERIALS AND METHODS: Sound and restored enamel/dentin disks were stored in water for 24 h or 6 months + thermocycling. The disks were adapted to artificial pulp chambers and placed in compartments containing culture medium. Immediately after bleaching, the culture medium in contact with dentin was applied for 1 h to previously cultured odontoblast-like MDPC-23 cells. Thereafter, cell viability (MTT assay) and morphology (SEM) were assessed. Data were analyzed by two-way ANOVA and Tukey's test (a = 5%). RESULTS: In comparison to the negative control group (no treatment), no significant cell viability reduction occurred in those groups in which sound teeth were bleached. However, a significant decrease in cell viability was observed in the adhesive-restored bleached groups compared to negative control. No significant difference among bleached groups was observed with respect to the presence of restoration and storage time. CONCLUSION: The application of 35% HP bleaching gel to sound teeth for 15 min does not cause toxic effects in pulp cells. When this bleaching protocol was performed in adhesive-restored teeth, a significant toxic effect occurred.

Cytotoxicity of resin-based luting cements to pulp cells.

PURPOSE: To evaluate the cytotoxicity of components released from different types of luting cements to two cell lines obtained from pulp tissue. METHODS: Three types of luting cements were evaluated, distributed into the following groups: G1--negative control (no treatment); G2--resin-modified glass-ionomer cement (Rely X Luting 2); G3--self-adhesive resin cement (Rely X U200); and G4--conventional resin cement (Rely X ARC). Standardized cylindrical specimens (14 mm diameter and 1 mm thick) prepared with the dental materials were immersed in culture medium (DMEM) for 24 hours to obtain the extracts (DMEM + components released from the cements). Then, the extracts were applied to cultured odontoblast-like MDPC-23 cells or human dental pulp cells (HDPCs). Finally, cell viability (MTT assay), cell death (Annexin/PI) (Kruskal-Wallis/Mann-Whitney; α = 5%) and cell morphology (SEM) were assessed. Cements' components in contact with cells (SEM/EDS) and pH of the extracts were also evaluated. RESULTS: The resin-modified glass-ionomer cement (G2) caused the most intense toxic effect to the two cell lines; the cell viability reduction was around 95.8% and 89.4% for MDPC-23 cells and HDPCs, respectively, which was statistically significantly different compared with that of the negative control group (G1). Also, a high quantity of particles leached from this ionomeric cement was found on the cells, which showed intense morphological alterations. In the G2 group, 100% necrosis was observed for both cell lines, and an acidic pH was detected on the extract. Conversely, Rely X U200 (G3) and Rely X ARC (G4), which presented low solubility and no alteration in pH, caused only slight cytotoxicity to the cultured cells.

Effect of time between adhesive application and photoactivation on adhesion and collagen exposure.

PURPOSE: To evaluate the influence of the time elapsed between the application and photoactivation of Single Bond 2 (SB) on microtensile bond strength (µTBS) and collagen exposure at the adhesive interface produced in the presence of intrapulp pressure. METHODS: Dentin occlusal surfaces were prepared in 72 molars, and divided into eight groups (n = 9). After acid etching, SB was applied, with or without simulated intrapulp pressure, and remained undisturbed for 0, 20, 40 or 60 seconds, before photoactivation. Three teeth/group were processed for staining with Goldner trichrome and evaluation of the thickness of exposed collagen zone (CZ) at the base of the hybrid layer. Composite resin build-ups were placed on the remaining six prepared teeth prior to sectioning for microtensile testing. Data were submitted to ANOVA and Tukey tests (α = 0.05). RESULTS: In the absence of pressure, immediate photoactivation resulted in the lowest µTBS, while the other groups did not differ among them. Under intrapulp pressure, the lowest values were observed after 60 seconds. There was no difference in the thickness of the exposed collagen zone among the groups without pressure. However, thicker layers were recorded in the presence of pressure after 40 and 60 seconds. Waiting 60 seconds between application and photoactivation of SB significantly reduced resin-dentin bond strength when pulpal pressure was simulated.

Phototoxic effect of curcumin on methicillin-resistant Staphylococcus aureus and L929 fibroblasts.

Photodynamic therapy has been investigated as an alternative method of killing pathogens in response to the multiantibiotic resistance problem. This study evaluated the photodynamic effect of curcumin on methicillin-resistant Staphylococcus aureus (MRSA) compared to susceptible S. aureus (MSSA) and L929 fibroblasts. Suspensions of MSSA and MRSA were treated with different concentrations of curcumin and exposed to light-emitting diode (LED). Serial dilutions were obtained from each sample, and colony counts were quantified. For fibroblasts, the cell viability subsequent to the curcumin-mediated photodynamic therapy was evaluated using the MTT assay and morphological changes were assessed by SEM analysis. Curcumin concentrations ranging from 5.0 to 20.0 µM in combination with any tested LED fluences resulted in photokilling of MSSA. However, only the 20.0 µM concentration in combination with highest fluence resulted in photokilling of MRSA. This combination also promoted an 80% reduction in fibroblast cell metabolism and morphological changes were present, indicating that cell membrane was the main target of this phototherapy. The combination of curcumin with LED light caused photokilling of both S. aureus strains and may represent an alternative treatment for eradicating MRSA, responsible for significantly higher morbidity and mortality and increased healthcare costs in institutions and hospitals.

Low toxic effects of a whitening strip to cultured pulp cells.

PURPOSE: To assess the trans-enamel and trans-dentin toxicity of a 10% hydrogen peroxide (HP) whitening strip to odontoblast-like cells (MDPC-23). METHODS: Enamel surfaces of enamel/dentin discs adapted to artificial pulp chambers were subjected to two 30-minute whitening strip applications to obtain indirect extracts (DMEM + bleaching components that diffused across enamel and dentin). The extracts were applied for 1 hour to the cells for 1 or 5 days. A bleaching gel with 35% HP was used as the positive control. Cell viability (MTT assay) and morphology (SEM) as well as the quantity of HP in the extracts were assessed. RESULTS: Discrete cell viability reduction (21.9%) associated with slight alterations in cell morphology occurred after application of the extracts for 5 days to the MDPC-23 cells (Tukey's test; P < 0.05). Lower enamel/dentin diffusion of HP was observed after the use of the whitening strip compared with the bleaching gel (Mann-Whitney; P < 0.05).

Toxicity of photodynamic therapy with LED associated to Photogem®: an in vivo study.

The aims of this study were to evaluate the effects of Photogem®-mediated photosensitization on rat palatal mucosa and the biodistribution of the photosensitizer in this tissue. A solution of Photogem® (500 or 1000 mg/l) was applied to the palatal mucosa for 30 min and the exposure time to blue LED (460 nm) was 20 min (144 J/cm(2)). At 0, 1, 3, and 7 days, palatal mucosa was photographed for macroscopic analysis. After killing, the palate was removed for microscopic analysis. Thermal mapping evaluated temperature change in the tissue during irradiation. All experimental groups revealed intact mucosa in the macroscopic analysis. Tissue alterations were observed microscopically for only four out of 80 animals subjected to PDT. Fluorescence emitted by Photogem® was identified and was limited to the epithelial layer. A temperature increase from 35 to 41°C was recorded. Photogem®- mediated PDT was not toxic to the rat palatal mucosa.

Correlation between light transmission and permeability of human dentin.

The influence of dentin permeability on transdentinal LED light propagation should be evaluated since this kind of phototherapy may further be clinically used to stimulate the metabolism of pulp cells, improving the healing of damaged pulps. This study evaluated the influence of the dentin permeability on the transdentinal LED light (630 nm) transmission. Forty-five 0.5-mm-thick dentin disks were prepared from the coronal dentin of extracted sound human molars. An initial measurement of transdentinal LED light transmission was carried out by illuminating the discs in the occlusal-to-pulpal direction onto a light power sensor to determine light attenuation. The discs were treated with EDTA for smear layer removal, subjected to analysis of hydraulic conductance, and a new measurement of transdentinal LED light transmission was taken. Spearman's correlation coefficient was used for analysis of data and showed a weak correlation between dentin permeability and light attenuation (coefficient = 0.19). This result indicates that higher or lower dentin permeability does not reflect the transdentinal propagation of LED light. Significantly greater transdentinal propagation of light was observed after treatment of dentin surface with EDTA (Wilcoxon test, p < 0.05). According to the experimental conditions of this in vitro study, it may be concluded that dentin permeability does not interfere in the transdentinal LED light transmission, and that smear layer removal facilitates this propagation.

Pro-inflammatory mediators expression by pulp cells following tooth whitening on restored enamel surface.

This paper aimed to assess the influence of adhesive restoration interface on the diffusion of hydrogen peroxide (H2O2), indirect toxicity, and pro-inflammatory mediators expression by odontoblast-like cells, after in-office tooth whitening. Dental cavities prepared in bovine enamel/dentin discs were adhesively restored and subjected or not to hydrolytic degradation (HD). A whitening gel with 35% H2O2 (WG) was applied for 45 min onto restored and non-restored specimens adapted to artificial pulp chambers giving rise to the groups: SD- intact discs (control); SD/HP- whitened intact discs; RT/HP- restored and whitened discs; and RT/HD/HP- restored and whitened discs subjected to HD. The extracts (culture medium + WG components diffused through enamel/dentin/restoration interface) were collected and applied to odontoblast-like MDPC-23 cells. The study evaluated the amount of H2O2 in the extracts, as well as the cell viability (CV), cell morphology (CM), and gene expression of inflammatory mediators (TNF-α and COX-2) by the pulp cells exposed to the extracts (ANOVA and Tukey tests; 5% significance). All whitened groups presented lower CV than SD (control; p<0.05). The highest CV reduction and gene expression of TNF-α and COX-2 was observed in the RT/HD/HP group in comparison with SD/HP and RT/HP (control; p<0.05). CM alterations occurred in all whitened groups. The intensity of these cell side effects was directly related with the amount of H2O2 in the extracts. We concluded that adhesive restoration of dental cavity increases the H2O2 diffusion after in-office whitening, enhancing the indirect toxicity of this therapy and trigger pro-inflammatory overexpression by MDPC-23 cells.

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

OBJECTIVE: To assess the potential influence of violet LED (V-LED) application time on the esthetic efficacy and cytotoxicity of a 35% H2O2 bleaching gel. METHODOLOGY: Stained 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. RESULTS: Although 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). CONCLUSION: Although 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.

Influence of the activation mode of a self-etch resin-based luting cement upon the metabolism of odontoblast-like cells.

PURPOSE: To evaluate the cytotoxicity of a self-etch resin-based luting cement, RelyXUnicem (RXU) upon chemical or dual cure and with or without interposition of IPS d.SIGN (IPSD) or IPS Empress II (IPSE) ceramic discs between cement and light source. METHODS: 112 RXU specimens were subjected to different curing conditions and incubated in culture medium (DMEM) to obtain extracts. The following groups were formed: G1: DMEM (control); G2: dual RXU; G3: chemical RXU; G4: dual RXU+IPSD; G5: chemical RXU+IPSD; G6: dual RXU+IPSE; and G7: chemical RXU+IPSE. Cultured odontoblast-like cells were incubated for 24 hours in contact with the extracts. Data from cell metabolism (CM), total protein dosage (TPD) and alkaline phosphatase activity (APA) were obtained and analyzed statistically (alpha = 0.05; Kruskal Wallis and Mann-Whitney tests). Cell morphology was analyzed by SEM. RESULTS: CM and APA were significantly lower in G3 and G7 than in G1 (P<0.05). Significant TPD decrease occurred in G5 and G7 compared to G1 (P<0.05). Only G4 and G6 presented CM changes. RXU caused no cytotoxicity when subjected to dual cure without ceramic interposition. However, mild cytopathic effects were observed after chemical setting without ceramic interposition, and after chemical and dual activation under ceramic discs.

Proliferation rate and expression of stem cells markers during expansion in primary culture of pulp cells.

The aim of the present study was to evaluate the proliferation rate and the expression of stem cells markers during expansion in primary culture of dental pulp stem cells (DPSCs), comparing different techniques (explant and enzymatic digestion), subject ages (up to 40 and over 40) and cell passages (#2, #5 and #8). DPSCs were isolated using either the enzymatic digestion (ED) or explant (EX) technique. The number of days needed for the cells to reach confluence was determined. Immunophenotyping was performed by immunofluorescence and flow cytometry analysis using antibodies specific for nestin, vimentin, CD44, CD146, Oct3/4 and CD34. Data were subjected to three-way analysis of variance (n = 6/group). The ANOVA tests were complemented by Tukey's or t-tests (p < 0.05). The variables "donor age" and "technique" were analyzed to define the optimal desirability value using a response optimization. DPSCs presented a high proliferation rate from passages 2 to 5 while cells from passage 8 proliferated at a slower rate. For all markers, no significant difference was observed among passages, irrespective of the technique used or the donor's age. The mean fraction of specific antibodies was 73.7% (± 11.5), 49.0% (± 18.7), 80.1% (± 8.0), 45.2% (± 13.7), 64.7% (± 5.3) and 2.0% (± 1.5) for CD44, OCT, vimentin, nestin, CD146 and CD34, respectively. The highest optimal desirability value was obtained using the ED technique and cells from younger patients (d = 0.92). However, it was concluded that neither the isolation technique nor the donor age or cell passage significantly interfered with the stem cell phenotype and proliferation rate during cell expansion.

Effect of chlorhexidine on bond strength of two-step etch-and-rinse adhesive systems to dentin of primary and permanent teeth.

PURPOSE: To evaluate the influence of chlorhexidine digluconate (CHX) application on the immediate microtensile bond strength (microTBS) of two-step etch-and-rinse adhesive systems to the dentin of primary and permanent teeth. METHODS: Noncarious human teeth (24 primary molars and 24 premolars) were used. The primary and permanent teeth were randomly assigned to three groups (n = 8) according to the adhesive system: Adper Single Bond, Prime & Bond NT and Excite DSC. Each group was further divided in two subgroups (n = 4) in which the phosphoric acid-etched dentin was treated with 20 microL of either 2% CHX or deionized water for 60 seconds prior to adhesive system application. The adhesive systems were applied according to the manufacturers' instructions and resin composite blocks were built up on the treated surfaces. The teeth were vertically sectioned perpendicular to adhesive interface and beam-shaped specimens with a 0.81 mm2 cross-sectional area were obtained and subjected to microTBS testing at a crosshead speed of 0.05 mm/minute. MicroTBS data were analyzed statistically by ANOVA and Tukey's test (alpha = 0.05). The failure modes were verified with a stereomicroscope. RESULTS: CHX application increased significantly (P < 0.05) the microTBS of Prime & Bond NT and Single Bond to the acid-etched primary and permanent dentin, while no positive or negative effect was observed for Excite DSC. There was a predominance of adhesive failures in all control and CHX-treated groups. No fracture distribution pattern was observed.

Direct and transdentinal antibacterial activity of chlorhexidine.

PURPOSE: To evaluate the antibacterial effect of different chlorhexidine (CHX) concentrations against Streptococcus mutans using the agar-diffusion method with and without human dentin discs placed between the bacteria and the test substances. METHODS: For the direct application (agar-well technique), a base layer containing 15 mL of BHI agar and 300 microL of S. mutans inoculum (10(9) cfu/mL) was prepared in Petri dishes. Six wells per dish were made at equidistant points and immediately filled with CHX gels (0.12%, 0.2%, 1% and 2%), 35% phosphoric acid and pure natrosol (n = 6 wells/substance). Paper discs soaked in sterile distilled water served as control group (n = 6). For the indirect application (transdentinal diffusion), 0.2 mm- and 0.5 mm-thick human dentin discs (36 discs/thickness) had the hydraulic conductance determined, which allowed the homogeneous allocation of them to the experimental and control groups. The discs were placed at equidistant points on the Petri dishes containing BHI with the S. mutans inoculum (six discs per dish; one per substance) with the pulpal side in contact with the bacteria. In the discs treated with CHX gels, dentin surface was etched with H3PO4 and rinsed with distilled water before CHX gel application for 1 minute. After both direct and indirect application, the dishes were incubated for 24 hours and the bacterial growth inhibition zones formed around the wells and dentin discs were measured. Data were analyzed statistically by the non-parametric Kruskal-Wallis and Mann-Whitney tests at 5% significance level. RESULTS: In the direct test, all CHX concentrations presented a dose-dependent antibacterial activity against S. mutans. In the indirect test, there were statistically significant differences (P < 0.05) among all groups and the largest microbial growth inhibition zones were observed when 2% CHX was applied on 0.2 mm-thick discs (P < 0.05). It was concluded that all evaluated CHX gels exhibited both direct and transdentinal antibacterial activity against S. mutans. This effect of CHX was strongly influenced by the CHX concentration as well as the dentin barrier thickness.

Bond strength of two-step etch-and-rinse adhesive systems to the dentin of primary and permanent teeth.

OBJECTIVE: The purpose of this study was to compare the immediate microtensile bond strength (microTBS) of two-step etch-and-rinse adhesive systems to the dentin of primary and permanent teeth. STUDY DESIGN: Non-carious human teeth (12 primary molars and 12 premolars) were assigned to 3 groups according to the adhesive system. The adhesive systems were applied to flat superficial coronal dentin surfaces etched with phosphoric acid and composite resin blocks were built up. The teeth were sectioned to produce beam-shaped specimens with 0.81 mm2 cross-sectional area subjected to microTBS testing. MicroTBS data were analyzed statistically by ANOVA and Tukey's test (a = 0.05). RESULTS: The adhesive systems produced statistically similar mean microTBS to each other (p > 0.05) and no significant differences (p > 0.05) were found when the same material was applied to primary or permanent tooth dentin. The mean microTBS values (MPa) obtained were: Prime & Bond NT: 41.7 +/- 14.4 (permanent) and 40.8 +/- 13.4 (primary); Single Bond: 42.9 +/- 8.6 (permanent) and 41.4 +/- 11.9 (primary); Excite DSC: 46.3 +/- 11.3 (permanent teeth) and 43.4 +/- 12.0 (primary). CONCLUSION: There was no difference in the immediate microTBS of two-step etch-and-rinse adhesive systems when applied to the dentin of primary and permanent teeth.

Simvastatin-Enriched Macro-Porous Chitosan-Calcium-Aluminate Scaffold for Mineralized Tissue Regeneration.

The present study evaluated the odontogenic potential of human dental pulp cells (HDPCs) exposed to chitosan scaffolds containing calcium aluminate (CHAlCa) associated or not with low doses of simvastatin (SV). Chitosan scaffolds received a suspension of calcium aluminate (AlCa) and were then immersed into solutions containing SV. The following groups were established: chitosan-calcium-aluminate scaffolds (CHAlCa - Control), chitosan calcium-aluminate with 0.5 µM SV (CHAlCa-SV0.5), and chitosan calcium-aluminate with 1.0 µM SV (CHAlCa-SV1.0). The morphology and composition of the scaffolds were evaluated by SEM and EDS, respectively. After 14 days of HDPCs culture on scaffolds, cell viability, adhesion and spread, mineralized matrix deposition as well as gene expression of odontogenic markers were assessed. Calcium aluminate particles were incorporated into the chitosan matrix, which exhibited regular pores homogeneously distributed throughout its structure. The selected SV dosages were biocompatible with HDPCs. Chitosan-calcium-aluminate scaffolds with 1 µM SV induced the odontoblastic phenotype in the HDPCs, which showed enhanced mineralized matrix deposition and up-regulated ALP, Col1A1, and DMP-1 expression. Therefore, one can conclude that the incorporation of calcium aluminate and simvastatin in chitosan scaffolds had a synergistic effect on HDPCs, favoring odontogenic cell differentiation and mineralized matrix deposition.

Influence of Bisphosphonates on the Behavior of Osteoblasts Seeded Onto Titanium Discs.

Among other factors, types of bisphosphonates and treatment regimens seem to be strongly associated with the success or failure of installation of osseointegrated implants. This study investigated the influence of two bisphosphonates, sodium alendronate (SA) and zoledronic acid (ZA), on the metabolism of osteoblasts. Human osteoblasts (Saos-2) were seeded onto machined or acid-treated titanium discs previously placed on 24-well plates in complete culture medium. After 24 h, cells were exposed to bisphosphonates at 0.5, 1 or 5 µM for 24 h, 48 h or 7 days. The effects of SA and ZA on osteoblasts were assessed based on the adhesion of these cells to the titanium surfaces by direct fluorescence, cell viability, total protein and collagen synthesis. Alkaline phosphatase activity and mineral nodule deposition by these cells were also evaluated. Data were evaluated by ANOVA and Tukey tests (α=0.05). Decreased adhesion of cells to the titanium discs was observed when exposed to both bisphosphonates; however, this lack of cell adhesion was more evident for ZA-treated cells. In addition, the exposure of osteoblasts to ZA decreased the viability, ALP activity and mineral nodule deposition, which may be related to poor osseointegration after implant installation.

Effect of acid etching time on the degradation of resin-dentin bonds in primary teeth.

PURPOSE: To investigate the influence of etching time on the degradation of resin-dentin bonds produced in primary teeth. METHODS: 40 primary molars were randomly divided into four groups according to the adhesive system, Single Bond (SB) and Clearfil SE Bond (CSEB), and acid etching time. SB was applied to dentin after phosphoric acid etching for 15 or 7 seconds, whereas CSEB was applied after the application of SE Primer for 20 or 10 seconds. Resin composite crowns were built-up followed by the production of specimens with a cross-sectional area of 0.49 mm2, which were further divided according to the storage condition, 24 hours, 6 and 12 months in water. Data were submitted to ANOVA and Tukey tests (alpha=0.05). RESULTS: After 24 hours there was no significant difference between bond strengths produced by the adhesive systems, irrespective of the acid etching time. Water storage for 6 and 12 months significantly reduced bond strengths of SB, especially when the dentin was acid etched for 15 seconds. For CSEB, no significant alteration in bond strength was seen up to the storage period of 12 months for both etching times.