Cytotoxicity evaluation of three light-cured dentin adhesive materials on human gingival fibroblasts, ex vivo

Effect of Rapid High-Intensity Light-Curing on Increasing Transdentinal Temperature and Cell Viability: An In Vitro Study

BACKGROUND

This study investigated effects of rapid high-intensity light-curing (3 s) on increasing transdentinal temperature and cell viability.

METHODS

A total of 40 dentin discs (0.5 mm) obtained from human molars were prepared, included in artificial pulp chambers (4.5 × 5 mm), and subjected to four light-curing protocols (n = 5), with a Valo Grand light curing unit: (i) 10 s protocol with a moderate intensity of 1000 mW/cm2 (Valo-10 s); (ii) 3 s protocol with a high intensity of 3200 mW/cm2 (Valo-3 s); (iii) adhesive system + Filtek Bulk-Fill Flow bulk-fill composite resin in 10 s (FBF-10 s); (iv) adhesive system + Tetric PowerFlow bulk-fill composite resin in 3 s (TPF-3 s). Transdentinal temperature changes were recorded with a type K thermocouple. Cell viability was assessed using the MTT assay. Data were analyzed using one-way ANOVA and Tukey tests for comparison between experimental groups (p < 0.05).

RESULTS

The 3 s high-intensity light-curing protocol generated a higher temperature than the 10 s moderate-intensity standard (p < 0.001). The Valo-10 s and Valo-3 s groups demonstrated greater cell viability than the FBF-10s and TPF-3 s groups and statistical differences were observed between the Valo-3 s and FBF-10 s groups (p = 0.023) and Valo-3 s and TPF-3 s (p = 0.025), with a potential cytotoxic effect for the FBF-10 s and TPF-3 s groups.

CONCLUSIONS

The 3 s rapid high-intensity light-curing protocol of bulk-fill composite resins caused a temperature increase greater than 10 s and showed cell viability similar to and comparable to the standard protocol.

A Look Into the Cytotoxicity of Composite Fillings: Friend or Foe?

Dental resin composites are widely used restorative materials in dentistry for the treatment of carious and non-carious lesions as well as pit and fissure sealants, cavity liners, and endodontic sealers. They consist of two parts: an organic resin matrix and an inorganic/organic filler. The organic resin matrix phase is made up of multifunctional monomers and light-sensitive initiators, while the inorganic/organic filler phase is made up of micro/nano-sized fillers that primarily serve as reinforcement. Despite being a very promising dental material, its monomeric component has some drawbacks. It is well known for leaching out during incomplete polymerization, which can result in cytotoxicity. Bis-GMA (bisphenol A-glycidyl methacrylate) is the most cytotoxic of all monomeric components that exhibit synthetic estrogenic effects. The purpose of this article is to assess the cytotoxic effects of dental composite, understand the possible mechanism behind them, and explore ways to screen for and reduce this harmful effect, as well as shed light on its future prospects.

Cytotoxicity of universal dental adhesive systems: Assessment in vitro assays on human gingival fibroblasts

Universal adhesives are the most important innovation in restorative dentistry. They are composed of different monomers, solvents and fillers. The potential cytotoxic effect of these materials is an important scientific aspect in recent literature. The aim of this study was to determine, using different in vitro techniques, the cytotoxicity evaluation of seven universal enamel-dental adhesives on human gingival fibroblasts. For this purpose, seven universal dental enamel adhesives have been evaluated by in vitro cytotoxicity tests using direct contact tests (an unpolymerized and a polymerized method) and an indirect contact test: preparation of extracts. The polymerized method showed a cytotoxicity range from 36% (G-PremioBond, GPB) to 79% (FuturaBond M+, FB). With the unpolymerized direct methods the range was from 4% (Prime&Bond Active, PBA) to 40% (Ibond Universal, IB) for undiluted adhesives; generally passing to the major dilutions the test showed a strong inhibitory activity by all the adhesives. Whereas with the indirect method by diluting the extracts of all dental adhesives the cell viability increased. The data obtained from the work has shown a lower cytotoxic effect of Optibond Solo Plus (OB) and Adhesive Universal (AU) with more reliable results with the extracts technique. The choice of reliable in vitro cytotoxic technique could represent, in dental practice, an important aid for clinical procedures in the use of adhesive systems.

Factors affecting the outcomes of direct pulp capping using Biodentine

Introduction

This study aimed to evaluate the prognostic value of factors with regard to the treatment outcome of direct pulp capping using Biodentine (Septodont, Saint-Maur-des-Fossés, France), in permanent teeth in which the pulps were exposed during caries removal.

Methods

Between 2010 and 2014, 112 teeth with deep carious lesions underwent direct pulp capping. The patients were followed up at 2–3 months and 1–1.5 years with a routine examination on both recall visits. Periapical radiographs were taken at 1–1.5 years. Lack of patient complaints, positive reactions to cold and electric testing, no sensitivity to percussion, and no widening of the periapical ligament indicated success. The Fisher exact test was used for statistical analysis. The significance level was P = .05.

Results

Eighty-six teeth were available for 1–1.5 years follow-up. The overall success rate was 82.6%. Only age had a significant effect on the pulpal survival rate: the success rate was 90.9% in patients younger than 40 years and 73.8% in patients 40 years or older (P = .0480). Sex, initial or secondary caries treatment, occlusal or cervical/proximal caries, delayed placement of permanent filling, tooth position, and arch type did not influence the outcome.

Conclusions

A patient’s age influenced the outcome of direct pulp capping using this new calcium silicate cement.

Clinical relevance

Asymptomatic vital permanent teeth with cariously exposed pulp can be treated successfully by direct pulp capping using Biodentine.

Cytotoxicity of Etch-and-Rinse, Self-Etch, and Universal Dental Adhesive Systems in Fibroblast Cell Line 3T3

The aim of this study was to evaluate in fibroblast cultures the direct cytotoxic effects of etch-and-rinse, self-etch, and universal adhesive systems. The sterile glass cover slips (n = 3) were then immersed in culture medium to obtain the eluates for the experimental groups: (1) Adper™ Single Bond 2; (2) Ambar; (3) Adper™ Scotchbond™ Multi-Purpose; (4) Scotchbond™ Universal; (5) Ambar Universal; and (6) OptiBond All-In-One. As a negative control, sterile glass cover slips were immersed in culture medium only. After 24 h, the eluate obtained was applied on fibroblast culture. Cell viability and cell morphology were evaluated by MTT assay and SEM, respectively. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (α = 0.05). All adhesive systems except universal reduced cell viability in 3T3 cells to between 26.04% and 56.57%, and Scotchbond Universal and Ambar Universal reduced cell viability to 2.13% and 3.57%, respectively, when compared to the negative control. Cytoplasmic membrane shrinkage and cell-free areas with residual membrane fragments from dead cells were observed. In conclusion, improvements in universal adhesive system formulations and their mechanisms of action are not accompanied by increased toxicity compared with those in other systems, warranting commitment to the use of these dentin-pulp complexes.

In vitro dentin barrier cytotoxicity testing of some dental restorative materials

OBJECTIVES

To investigate the cytotoxicity of four dental restorative materials in three-dimensional (3D) L929 cell cultures using a dentin barrier test.

METHODS

The cytotoxicities of light-cured glass ionomer cement (Vitrebond), total-etching adhesive (GLUMA Bond5), and two self-etching adhesives (GLUMA Self Etch and Single Bond Universal) were evaluated. The permeabilities of human dentin disks with thicknesses of 300, 500, and 1000μm were standardized using a hydraulic device. Test materials and controls were applied to the occlusal side of human dentin disks. The 3D-cell scaffolds were placed beneath the dentin disks. After a 24-h contact with the dentin barrier test device, cell viabilities were measured by performing MTT assays. Statistical analysis was performed using the Mann-Whitney U test.

RESULTS

The mean (SD) permeabilities of the 300-μm, 500-μm, and 1000-μm dentin disks were 0.626 (0.214), 0.219 (0.0387) and 0.089 (0.028) μlmin^-1cm^-2cm H₂O^-1. Vitrebond was severely cytotoxic, reducing the cell viability to 10% (300-μm disk), 17% (500μm), and 18% (1000μm). GLUMA Bond5 reduced the cell viability to 40% (300μm), 83% (500μm), and 86% (1000μm), showing moderate cytotoxicity (300-μm) and non-cytotoxicity (500-μm and 1000-μm). Single Bond Universal and GLUMA Self Etch did not significantly reduce cell viability, regardless of the dentin thicknesses, which characterized them as non-cytotoxic.

CONCLUSIONS

Cytotoxicity varied with the materials tested and the thicknesses of the dentin disks.

CLINICAL SIGNIFICANCE

The tested cytotoxicity of materials applied on 300-, 500-, and 1000-μm dentin disks indicates that the clinical use of the test materials (excepting self-etching adhesives) in deep cavities poses a potential risk of damage to the pulp tissues to an extent, depending on the thickness of the remaining dentin.

Citotoxicity evaluation of three dental adhesives on vero cells in vitro

BACKGROUND

To evaluate, in vitro, the potential cytotoxicity of three different dental adhesives systems (Adper Single Bond 2 -SB, Silorane System Adhesive Bond -SSAB and Single Bond Universal -SBU) on cultivated Vero cells after different contact times.

MATERIAL AND METHODS

The cells were cultured in a concentration of 2 x 105 cells/mL for 24h and grown to sub-confluent monolayers. VERO cells were exposed to 25µl of conditioned extracts obtained from 24h, 48h and 72h immersion of adhesive samples in culture medium (DMEM), immediately after polymerization. Fresh DMEM was used as negative control. Cell metabolism was evaluated by the MTT assay (3-(4,5-dimethylthiazol-2-yl)-2, 5diphenyl-tetrazolium bromide). The data were analyzed statistically by ANOVA, considering a significance of 5%.

RESULTS

The values of cell viability ranged from 94.2% at 72h (SBU) to 109.6% at 48h (SB). The mean percentage of viability after exposure to the extracts of SB, SSAB and SBU were 103.2%, 100.63% and 97.43%, respectively. There was no statistically significant difference (p= 0.342) between the experimental and negative control groups.

CONCLUSIONS

At all exposure times, all adhesives tested in this study presented no cytotoxicity to Vero cells in vitro. Key words:Biocompatibility, cytotoxicity, dental adhesives, Vero cells.

Clinical and Histological Evaluation of Direct Pulp Capping on Human Pulp Tissue Using a Dentin Adhesive System

Objective. This study presents a clinical and histological evaluation of human pulp tissue responses after direct capping using a new dentin adhesive system. Methods. Twenty-eight caries-free third molar teeth scheduled for extraction were evaluated. The pulps of 22 teeth were mechanically exposed and randomly assigned to 1 of 2 groups: Single Bond Universal or calcium hydroxide. Another group of 6 teeth acted as the intact control group. The periapical response was assayed, and a clinical examination was performed. The teeth were extracted after 6 weeks, and a histological analysis was performed. The pulp status was assessed, and the thickness of the dentin bridge was measured and categorized using a histological scoring system. Results. The clinical phase was asymptomatic for Single Bond Universal patients. Patients in the calcium hydroxide group reported mild symptoms of pain, although the histological examination revealed that dentin bridges with or without limited pulpitis had begun forming in each tooth. The universal adhesive system exhibited nonsignificantly increased histological signs of pulpitis (P > 0.05) and a significantly weaker thin mineralized tissue layer (P < 0.001) compared with the calcium hydroxide group. Conclusion. The results suggest that Single Bond Universal is inappropriate for human pulp capping; however, further long-term studies are needed to determine the biocompatibility of this agent.

Influence of light-curing distance on degree of conversion and cytotoxicity of etch-and-rinse and self-etch adhesives

BACKGROUND

The degree of conversion (DC) of resin based materials depends, beside other factors, on the light-intensity applied during light curing. A lower DC might be correlated with an increased cytotoxicity of the respective materials. Therefore, aim of the present study was to investigate the influence of the distance between light-curing tip and adhesives on their cytotoxicity and degree of conversion (DC).

METHODS

For the cytotoxicity assay, a total of 98 bovine dentine samples were prepared, distributed to seven groups (G1-G7; n = 14) and treated as follows: G1: untreated; G2-G4: OptiBond FL; G5-G7: OptiBond All-In-One. Adhesives were light-cured (1200 mW/cm(2)) at 1 mm (G2;G5), 4 mm (G3;G6) or 7 mm (G4;G7) distance. Samples were stored in culture media for 24 h and extracts were added to cell cultures (dental pulp cells and gingival fibroblasts) for a further 24 h. Finally, released lactate dehydrogenase activity (LDH) was photometrically determined, as measure for the cytotoxic effects of the extracts. The cytotoxicity assay was performed three times. Additionally, the DC of the adhesives was determined by FTIR spectroscopy. DC measurements were performed five times.

RESULTS

For both cell types, no significant difference of LDH release was observed between untreated control group (G1) and treated groups G2-G7 (p > 0.05, respectively), between the groups treated with same adhesive and light-cured at different distance (p > 0.05, respectively), as well as between groups treated with different adhesives and light-cured at the same distance (p > 0.05, respectively). Within the respective adhesive, no significant difference in the DC was observed when light-cured at different distance (p > 0.05, respectively), while OptiBond FL showed significantly higher DCs compared to OptiBond All-In-One when light-cured at same distances (p < 0.05, respectively).

CONCLUSIONS

The distance between light-curing tip and adhesive surface does not significantly influence either the cytotoxicity or the DC of the tested adhesives.

Laser phototherapy enhances mesenchymal stem cells survival in response to the dental adhesives

Background. We investigated the influence of laser phototherapy (LPT) on the survival of human mesenchymal stem cells (MSCs) submitted to substances leached from dental adhesives. Method. MSCs were isolated and characterized. Oral mucosa fibroblasts and osteoblast-like cells were used as comparative controls. Cultured medium conditioned with two adhesive systems was applied to the cultures. Cell monolayers were exposed or not to LPT. Laser irradiations were performed using a red laser (GaAlAs, 780 nm, 0.04 cm², 40 mW, 1 W/cm², 0.4 J, 10 seconds, 1 point, 10 J/cm²). After 24 h, cell viability was assessed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide reduction assay. Data were statistically compared by ANOVA followed by Tukey's test (P < 0.05). Results. Different cell types showed different viabilities in response to the same materials. Substances leached from adhesives were less cytotoxic to MSCs than to other cell types. Substances leached from Clearfil SE Bond were highly cytotoxic to all cell types tested, except to the MSCs when applied polymerized and in association with LPT. LPT was unable to significantly increase the cell viability of fibroblasts and osteoblast-like cells submitted to the dental adhesives. Conclusion. LPT enhances mesenchymal stem cells survival in response to substances leached from dental adhesives.