Impact of bisphenol A and analogues eluted from resin-based dental materials on cellular and molecular processes: An insight on underlying toxicity mechanisms

Dental resin systems, used for artificial replacement of teeth and their surrounding structures, have gained popularity due to the Food and Drug Administration's (FDA) recommendation to reduce dental amalgam use in high-risk populations and medical circumstances. Bisphenol A (BPA), an endocrine-disrupting chemical, is an essential monomer within dental resin in the form of various analogues and derivatives. Leaching of monomers from resins results in toxicity, affecting hormone metabolism and causing long-term health risks. Understanding cellular-level toxicity profiles of bisphenol derivatives is crucial for conducting toxicity studies in in vivo models. This review provides insights into the unique expression patterns of BPA and its analogues among different cell types and their underlying toxicity mechanisms. Lack of a consistent cell line for toxic effects necessitates exploring various cell lines. Among the individual monomers, BisGMA was found to be the most toxic; however, BisDMA and BADGE generates BPA endogenously and found to elicit severe adverse reactions. In correlating in vitro data with in vivo findings, further research is necessary to classify the elutes as human carcinogens or xenoestrogens. Though the basic mechanisms underlying toxicity were believed to be the production of intracellular reactive oxygen species and a corresponding decline in glutathione levels, several underlying mechanisms were identified to stimulate cellular responses at low concentrations. The review calls for further research to assess the synergistic interactions of co-monomers and other components in dental resins. The review emphasizes the clinical relevance of these findings, highlighting the necessity for safer dental materials and underscoring the potential health risks associated with current dental resin systems.

Release and toxicity of bisphenol-A (BPA) contained in orthodontic adhesives: A systematic review

OBJECTIVE

The objectives of this systematic review of the literature are to search for BPA release from biomaterials used in orthodontics and to highlight their possible impact on human health.

MATERIALS AND METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model, digital and manual searches were conducted in February 2020 in the database of CENTRAL, MEDLINE and EMBASE. Thirteen parameters relating to the release and biological effects of BPA were identified and analysed.

RESULTS

Thirty-one non-randomized clinical trials were included. In general, the level of evidence was low, and the risk of bias ranged from moderate to high. Furthermore, although at different concentrations, most of in vitro and in vivo studies found BPA release from orthodontic adhesives. The lack of standardized protocols and the clinical and methodological heterogeneity of the studies prevented a valid interpretation of the actual results. Concerning the possible toxicity of BPA, no conclusive scientific evidence could be drawn, but it seems that orthodontic biomaterials containing BPA have potential adverse biological effects in humans.

DISCUSSION AND CONCLUSION

Until we have solid evidence from clinical trials, clinicians should consider that orthodontic adhesives containing BPA have potential short- and long-term adverse biological effects in humans. Careful consideration should therefore be given to bonding, polymerization and debonding protocols in orthodontics.

Comparison of shear bond strength of three different adhesives used as temporary bite raiser in daily orthodontic practice

OBJECTIVE

The aim of this study was to evaluate the shear bond strength of three different adhesives (Transbond XT, Light Cure Adhesive, 3M Unitek; Transbond Plus, Light Cure Band Adhesive, 3M Unitek; Transbond Supreme LV, Low Viscosity Light Cure Adhesive, 3M Unitek), which were applied to the etched enamel of occlusal faces of mandibular molar teeth to gain bite opening. The null hypothesis was that there is no statistically significant difference between shear bond strength of these three adhesives.

MATERIALS AND METHODS

Forty-eight human molar teeth were equally divided into three groups (n=16). Teeth were embedded in self-curing acrylic resin and were polished and etched. Adhesives were applied on the teeth and all adhesives were light cured for 20seconds. Universal Testing Machine was used for shear bond strength tests with a crosshead blade loaded at a crosshead speed of 1mm/min. Evaluating the type of failure was done by using Adhesive Remnant Index (ARI) was used to evaluate the remaining adhesive on the tooth.

RESULTS

One-way analysis of variance (ANOVA) was used to determine the significant differences between the three different orthodontic adhesives. There was no significant difference (P=0.774) between the groups according to ANOVA test. According to Kruskal-Wallis test there was no statistically significant differences in ARI scores among groups (P<0.01).

CONCLUSION

The null hypothesis was accepted. There was no statistically significant difference among their bond strength values. All of three materials can be used as temporary bite openers.

Monomer release from orthodontic retentions: An in vitro study

INTRODUCTION

The adhesives used to bond orthodontic retentions are low-loaded composite resins with a resinous matrix containing bisphenol A diglycidyl ether dimethacrylate synthesized from bisphenol A (BPA), fluidizers such as triethylene glycol dimethacrylate (TEGDMA) and hydrophilic polymers such as hydroxyethylmethacrylate. BPA disrupts the endocrine balance, and TEGDMA has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to evaluate in vitro the release of monomers from orthodontic bonded retentions.

METHODS

A reproducible model of bonded retentions was carried out using calibrated molds. We analyzed the release of monomers by gas phase chromatography coupled with mass spectrometry.

RESULTS

This model allowed us to qualitatively and quantitatively evaluate the in-vitro release of monomers from orthodontic adhesives. The quantitative and qualitative analyses showed no BPA release above the 0.02 ppm detection limit. A greater release of TEGDMA was observed with Transbond LR (31.7 μg/mL) than with Transbond XT (13.12 μg/mL) (both, 3M Unitek, Monrovia, Calif). Other toxic components (iodobenzene, iodobiphenyl, triphenyl stibine, and so on) were also identified.

CONCLUSIONS

Toxic and carcinogenic molecules not mentioned in the material safety data sheets were identified.

Antibacterial nanosilver coated orthodontic bands with potential implications in dentistry

Background & objectives:

Fixed orthodontic treatment, an indispensable procedure in orthodontics, necessitates insertion of dental bands. Insertion of band material could also introduce a site of plaque retention. It was hypothesized that band materials with slow-release antimicrobial properties could help in sustained infection control, prevention of dental plaque formation and further associated health risks. Considering the known antimicrobial proprieties of silver, a coating of silver nanoparticle (SNP) onto the stainless steel bands was done and characterized for its beneficial properties in the prevention of plaque accumulation.

Methods:

Coatings of SNPs on conventional stainless steel dental bands were prepared using thermal evaporation technology. The coated dental bands were characterized for their physicochemical properties and evaluated for antimicrobial activity and biocompatibility. The physiochemical characterization of band material both coated and uncoated was carried out using scanning electron microscope, energy dispersive spectroscopy, atomic force microscopyand contact angle test. Biocompatibility tests for coated band material were carried using L929 mouse fibroblast cell culture and MTT [3-(4, 5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay. Antimicrobial activity of coated band material against Gram-positive bacteria was tested.

Results:

A stable and uniform coating of SNPs was obtained. The coated band materials were biocompatible as well as possessed distinct antimicrobial activity.

Interpretation & conclusions:

The SNP coated dental bands could be potential antimicrobial dental bands for future clinical use. Further studies need to be done to validate the efficiency of coated band materials in oral environments.

Biocompatibility evaluation of orthodontic composite by real-time cell analysis

INTRODUCTION

The aim of this study was to evaluate the cytotoxic effects of three different light-cured orthodontic composites.

MATERIAL AND METHODS

Light Bond (Reliance orthodontic products), Grengloo (Ormco corporation), and Kurasper F (Kuraray Europe GmbH) were selected for the experiment. Specimens were prepared according to the manufacturers' instructions, measuring 5 mm in diameter and 2 mm in thickness. Fibroblast cells were obtained from healthy gingival connective tissues. The composite cylinders were incubated in Dulbecco's modified Eagle's culture medium for 72 h according to ISO 10993-5 standards. The xCELLigence method was used to evaluate fibroblast cell vitality. After seeding 200 mL of the cell suspensions into the wells (20,000 cells/well) of the E-plate 96, gingival fibroblasts were treated with bioactive components released by the orthodontic composite materials and monitored every 15 min for 121 h.

RESULTS

There were no significant differences between the human gingival fibroblast (HGF) cell indexes of the control and all testing groups (p > 0.05) at 24 and 48 h. Light Bond demonstrated statistically significant decrease in HGF index (p < 0.05) at 72 h, but there was no significant difference among the Kurasper F, Grengloo, and untreated control groups (p > 0.05). Light Bond (p < 0.001) and Grengloo (p < 0.05) groups had lower HGF cell index values when compared to untreated control group, but Kurasper F demonstrated no significant differences between the control groups at 96 h (p > 0.05).

CONCLUSION

Orthodontic composite materials include biologically active components and may change oral tissue. So, biocompatible orthodontic bonding composites should be used.

Cytotoxicity of temporary cements on bovine dental pulp-derived cells (bDPCs) using realtime cell analysis

PURPOSE

To evaluate the cytotoxicity of temporary luting cements on bovine dental pulp-derived cells (bDPCs).

MATERIALS AND METHODS

Four different temporary cements were tested: Rely X Temp E (3M ESPE), Ultratemp (Ultradent), GC Fuji Temp (GC), and Rely X Temp NE (3M ESPE). The materials were prepared as discs and incubated in Dulbecco's modified eagle's culture medium (DMEM) for 72 hours according to ISO 10993-5. A real-time cell analyzer was used to determine cell vitality. After seeding 200 µL of the cell suspensions into the wells of a 96-well plate, the bDPCs were cured with bioactive components released by the test materials and observed every 15 minutes for 98 hours. One-way ANOVA and Tukey-Kramer tests were used to analyze the results of the proliferation experiments.

RESULTS

All tested temporary cements showed significant decreases in the bDPCs index. Rely X Temp E, GC Fuji Temp, and Rely X Temp NE were severely toxic at both time points (24 and 72 hours) (P<.001). When the cells were exposed to media by Ultratemp, the cell viability was similar to that of the control at 24 hours (P>.05); however, the cell viability was significantly reduced at 72 hours (P<.001). Light and scanning electron microscopy examination confirmed these results.

CONCLUSION

The cytotoxic effects of temporary cements on pulpal tissue should be evaluated when choosing cement for luting provisional restorations.

Real-time cell analysis of the cytotoxicity of orthodontic brackets on gingival fibroblasts

PURPOSE

The aim of this study was to evaluate the cytotoxic effects of 6 different orthodontic bracket types on human gingival fibroblasts (HGFs) using the xCELLigence system.


METHODS

The orthodontic brackets used in this study were gold-plated steel (Apollo Gold), titanium (Rematitan), stainless steel (Equilibrium 2), lucid ice (Inspire ICE), metal-reinforced ceramic (Clarity) and composite (OrthoFlex). Gingival fibroblasts were isolated from human gingival connective tissue of systemically healthy individuals. Tested brackets were incubated in DMEM culture medium for 72 hours according to ISO 10993-5 standards. Gingival fibroblasts were maintained with Dulbecco modified Eagle medium containing 10% fetal bovine serum. The xCELLigence system was used to evaluate cell survival. The statistical analysis used was ANOVA and Tukey-Kramer multiple comparison tests.


RESULTS

When the data were evaluated in the 30th hour, Apollo Gold showed significant decreases in cell index (P<0.001). It also showed statistically significant decreases (P<0.001) in the 65th hour, but Clarity and Inspire ICE showed significant increases in cell indices (P<0.001, P<0.01). In the 114th hour, Clarity and Equilibrium 2 showed statistically significant increases in cell indices (P<0.001). Inspire ICE and Rematitan demonstrated significant increases (P<0.05). There were significant decreases in cell index of Apollo Gold (P<0.001). 


CONCLUSIONS

The tested brackets are suitable for clinical application, but further studies using different test methods are needed for gold-plated brackets.

Effects of plasma-emulating light emitting diode (LED) versus conventional LED on cytotoxic effects of orthodontic cements as a function of polymerization capacity

Objectives:

The study was aimed at evaluating, in vitro, cytotoxicity of four resin-based orthodontic cements (RBOC) as a function of degree of conversion (DC) and the light curing unit (LCU) employed on mouse fibroblast (L929).

Materials and Methods:

Nine samples were manufactured for each group of cements using plasma-emulating light-emitting diode (LED) and conventional LED. Toxicity was assessed by immersing four specimens to culture medium (24 h/37°C) for extracting residual monomer or cytotoxic substance. Cell mitochondrial activity of L929 cell was evaluated using methyl tetrazolium (MTT) test. DC was evaluated by Fourier transform infrared spectroscopy for five samples.

Results:

Cements, LCUs, and interaction between cements and LCUs were found to play a statistically significant role in cytotoxicity ( p < 0.0001). Opal band cement (OPAL) plasma LED was found noncytotoxic (90–100% cell viability). The other RBOC–LCU combinations were slightly cytotoxic (60–90% cell viability). Cements ( p < 0.01) and LCUs ( p < 0.05) had a statistically significant effect on DC. Conversely, interaction between cement and LCU had no statistically significant role on DC ( p > 0.05). OPAL plasma LED displayed the highest levels of DC. The correlations between cell viability and DC were positive for three RBOCs.

Conclusion:

Therefore, high-intensity LCUs can be said to efficiently affect polymerization, so higher DC rates may achieve higher cell viability rates.

Clinical Relevance:

Cements and LCUs must be matched to each another to result in higher DC and maximal biocompatibility. Dual cure systems presented relatively high cell survival and higher DC, thus expressing superior to single-cure systems with plasma LED.

Real-time cell analysis of the cytotoxicity of the components of orthodontic acrylic materials on gingival fibroblasts

INTRODUCTION

The aim of this study was to evaluate the cytotoxicity of 3 orthodontic acrylic materials and 2 manipulation methods.

METHODS

The orthodontic acrylic materials Orthocryl EQ (Dentaurum, Ispringen, Germany), Orthoplast (Vertex Dental, Zeist, The Netherlands), and O-80 (Imicryl, Konya, Turkey) were prepared with 2 polymerization methods (doughing and spray on). Totally, 60 cylinders (5 × 2 mm), fabricated by using a different acrylic and method, were divided into 6 groups. Gingival fibroblasts were isolated from gingival connective tissue of systemically healthy subjects. Materials were incubated in Dulbecco's modified eagle's medium culture medium (Biological Industries, Beit Haemek, Israel) for 72 hours according to ISO 10993-5 standards (surface area to volume ratio of the specimen to cell-culture medium: 3 cm(2)/mL). Gingival fibroblasts were maintained with Dulbecco's modified eagle medium containing 10% fetal bovine serum. A real-time cell analyzer (RT-CES, xCELLigence; Roche Applied Science, Mannheim, Germany, and ACEA Biosciences, San Diego, Calif) was used to evaluate cell survival. After seeding 200 μL of the cell suspensions into the wells (20,000 cells/well) of the E-plate 96, gingival fibroblasts were treated with bioactive components released by the acrylic materials (1/1 and 1/2 dilutions) and monitored every 15 minutes for 121 hours. For the proliferation experiments, the statistical analyses used were 1-way analysis of variance (ANOVA) and Tukey-Kramer multiple comparisons tests.

RESULTS

There was no significant difference between the cell indexes of the control and study groups for the 1/1 and 1/2 dilutions at 21 and 32 hours. When evaluated at 68 hours, all 1/2 dilutions of acrylic materials showed statistically insignificant differences (P >0.05) except for Orthoplast (P <0.05). But all acrylic materials were different from the control group in the 1/1 dilutions (P <0.001). At 121 hours, all test groups were significantly different from the untreated control group (P <0.001).

CONCLUSIONS

The results indicate that the long cycle increased the cytotoxicity of the tested materials, and there was no significant difference between the spray-on and doughing methods on cytotoxicity.