Hayriye Esra Ülker

Cytotoxicity Testing of Temporary Luting Cements with Two- and Three-Dimensional Cultures of Bovine Dental Pulp-Derived Cells

This study evaluated the cytotoxicity of eugenol-containing and eugenol-free temporary luting cements. For cytotoxicity testing, bovine pulp-derived cells transfected with Simian virus 40 Large T antigen were exposed to extracts of eugenol-containing (Rely X Temp E) and eugenol-free (Provicol, PreVISION CEM, and Rely X Temp NE) temporary luting cements for 24 h. The cytotoxicity of the same materials was also evaluated in a dentin barrier test device using three-dimensional cell cultures of bovine pulp-derived cells. The results of the cytotoxicity studies with two-dimensional cultures of bovine dental pulp-derived cells revealed that cell survival with the extracts of Rely X Temp E, Provicol, PreVISION CEM, and Rely X Temp NE was 89.1%, 84.9%, 92.3%, and 66.8%, respectively. Rely X Temp NE and Provicol showed cytotoxic effects on bovine dental pulp-derived cells (P < 0.05). The results of the dentin barrier test revealed that cell survival with the above-mentioned temporary cement was 101.5%, 91.9%, 93.5%, and 90.6%, respectively. None of the temporary luting cements significantly reduced cell survival compared with the negative control in the dentin barrier test (P > 0.05). Biologically active materials released from temporary luting cements may not influence the dentine-pulp complex if the residual dentine layer is at least 0.5 mm thick.

Residual monomer release from orthodontic adhesives cured with different light sources

Abstract Introduction: The aim of this study was to evaluate the residual monomer release from orthodontic adhesives cured with light-emitting diode (LED) and halogen light sources. Methods: Seven hundred and twenty stainless steel brackets were divided into 3 groups according to the adhesive system used (Transbond XT light-cure adhesive [TXT], Transbond LR capsule [LR], and Light Bond light-cure adhesive paste [LB]), and each group was divided into 2 subgroups according to light-curing procedure (LED or halogen). Brackets were bonded with adhesives onto tooth buccal surfaces and polymerized. Each specimen contained 24 brackets that simulated the oral environment (n = 5). The specimens were immersed in a 75% ethanol/water solution at 37 °C for 10 min, 1 h, 1 d, 7 d, 14 d, and 30 d, respectively. Eluted monomers (Bis-GMA, UDMA, and TEGDMA) were detected using HPLC. Results: There was residual monomer release at all time periods, and the highest amount of release was observed cumulatively on the 30th day. The cumulative Bis-GMA released from adhesives was not different (p > 0.05). The cumulative TEGDMA released from adhesives was statistically different (p < 0.05). There was no statistical difference between QTH and LED light-curing units for each adhesive (p > 0.05). Conclusions: The release of residual monomers stays at a high level for a long time after polymerization. The total leaching of residual monomers from the Light Bond light-cure sealant resin plus Light Bond light-cure adhesive paste was higher than that of other materials for both curing units. Different curing units (LED or QTH) did not affect the monomer release from the orthodontic adhesives.

Intrapulpal Thermal Changes during Setting Reaction of Glass Carbomer® Using Thermocure Lamp

Objectives. To measure the temperature increase induced during thermocure lamp setting reaction of glass carbomer and to compare it with those induced by visible light curing of a resin-modified glass ionomer and a polyacid-modified composite resin in primary and permanent teeth. Materials and Methods. Nonretentive class I cavities were prepared in extracted primary and permanent molars. Glass carbomer (GC) was placed in the cavity and set at 60°C for 60 sn using a special thermocure lamp. Resin-modified glass ionomer (RMGIC) and polyacid-modified composite resin (PMCR) were placed in the cavities and polymerized with an LED curing unit. Temperature increases during setting reactions were measured with a J-type thermocouple wire connected to a data logger. Data were examined using two-way analysis of variance and Tukeys honestly significant difference tests. Results. The use of GC resulted in temperature changes of 5.17 ± 0.92°C and 5.32 ± 0.90°C in primary and permanent teeth, respectively (p > 0.05). Temperature increases were greatest in the GC group, differing significantly from those in the PMCR group (p < 0.05). Conclusion. Temperature increases during polymerization and setting reactions of the materials were below the critical value in all groups. No difference was observed between primary and permanent teeth, regardless of the material used.

Cytotoxicity evaluation of dentin contacting materials with dentin barrier test device using erbium-doped yttrium, aluminum, and garnet laser-treated dentin

Objectives: The effect of dentin contacting materials on three-dimensional cultures of pulp-derived cells was evaluated in a dentin barrier test device using erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser-treated dentin. Methods: The test materials (iBond®, G-Bond™, and Vitrebond™) were applied on laser-treated or untreated dentin discs. After 24 h of exposure with perfusion of the test chamber, cell survival was evaluated by enzyme activity and related to a nontoxic control material. The mean values of control tissues were set to represent 100% viability. Data were analyzed using Kruskal–Wallis and Mann–Whitney U test. Results: Vitrebond was the most toxic material for both laser-treated and untreated dentin. On untreated dentin, G-bond was cytotoxic to the pulp-derived cells (p < 0.05), and iBond was similar to the negative control group (p > 0.05). However, G-Bond and iBond were not cytotoxic when they were applied to Er:YAG laser-treated dentin (p > 0.05). Conclusion: Er:YAG laser treatment of dentin may protect the pulp cells from toxic substances of dentin contacting restorative materials; however, this effect is material related. Taking into consideration the limitations of this in vitro study, the Er:YAG laser treatment of dentin before restoration might be an option for decreasing the cytotoxic effects of the dental materials. Further research is required for clinical applications.

Evaluation of HEMA released from four different adhesive systems by HPLC

Purpose This study evaluated the elution of 2-hydroxyethyl methacrylate (HEMA) from 4 different adhesives, using high-performance liquid chromatography (HPLC). Materials and Methods The adhesives were applied on a bovine dentin surface and polymerized using an LED curing unit (n=5). After polymerization, specimens were stored in 75% ethanol solution (6 mL). Residual HEMA that was eluted from adhesives (after 10 minutes, 1 hour, 24 hours, 7 days and 30 days) was analyzed using HPLC. Statistical analyses were performed using 1-way ANOVA, Tukey HSD test and paired 2-sample t-test. Results There were statistically significant differences among adhesive systems for the cumulative released HEMA and among the time periods (p<0.05). Clearfil SE Bond showed the highest amount of HEMA released, while Easy Bond showed the lowest. Among the time periods, the highest eluted HEMA value was detected in 10 minutes for all adhesives, and elution continued for up to 30 days. Conclusions The HEMA eluted from adhesives was in different amounts, and the elution continued for a long time. The amount of eluted HEMA from adhesives used in this study was not viewed as critical for toxic reactions in biological tissues.

Effect of endodontic irrigants on microtensile bond strength of a self-etching adhesive system

Aim: The aim of this in vitro study was to evaluate the effect of two different irrigation solutions, alone or in combination, with different application times on the dentin bond strength of a self-etching adhesive. Materials and Methods: Twenty-eight extracted non-carious human third molars were randomly distributed into seven groups according to the irrigant. The crowns of the molars were sectioned vertically through bucco-lingual direction. Solutions of 5% sodium-hypochlorite (NaOCl), 3% hydrogen-peroxide (H 2 O 2 ), and a combination of NaOCl and H 2 O 2 were applied to the dentin surface for various lengths of time. The adhesive system (Clearfil SE Bond; Kuraray, Japan) was applied according to the manufacturers′ directions and then the dentin surfaces were built up with a hybrid composite resin (Clearfil AP-X Kuraray, Japan). Specimens were sectioned into 15 sticks; each of them had a 0.65 mm 2 bonding area. Microtensile bond strength was determined (MPa), and the results were statistically analyzed using one-way ANOVA and Tukey′s HSD test. Results: Irrigation with NaOCl alone showed similar micro-tensile bond strength values with the control group (P > 0.05). In comparison to control group, irrigation with H 2 O 2 alone for 5 min and 30 min and the irrigation with H 2 O 2 /NaOCl combination each for 15 min decreased the microtensile bond strength. Conclusion: The use of H 2 O 2 significantly reduced the bond strengths of the self-etching adhesive when applied alone or in combination with NaOCl for a long time.

Effects of five different resin-based sealers on L929 and Saos-2 cell viability

The aim of this study was to evaluate the cytotoxic effects of five different resin-based root canal sealers: EndoREZ, Epiphany SE, EZ-Fill, MMSeal and AHPlus. Set materials were extracted in culture medium and cytotoxicity was determined in two cell lines, human osteosarcoma cell line (Saos-2) and mouse skin fibroblast cells (L929). The cells were incubated in contact with elutes for 24 h. The cell mitochondrial activity was evaluated by the methylthiazole tetrazolium assay. Results with demonstrated that all sealers showed a reduced vital cell number in comparison with the control group (P < 0.05). For L929 cells, the ranking of the most to the least toxic material was: EZ-Fill (12.0%) = EndoREZ (12.1%) = AHPlus (12.4%) > MMSeal (44%) = Epiphany SE (46.2 %). For Saos-2 cells revealed that cell survival with extracts of EndoREZ, Epiphany SE, EZ-Fill, MMSeal and AHPlus was 33.9%, 32.9 %, 33.1%, 35.3% and 34.6%, respectively, all tested sealers showed moderate cytotoxicity. Based on the results obtained from the present study, all tested resin-based sealers appear to show toxicity potential to both cells in spite of different toxicity degrees. Therefore, better sealers need to be developed with acceptable biological properties for root canal filling.