Biocompatibility of resin-modified filling materials

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.

Effects of washing agents on the mechanical and biocompatibility properties of water-washable 3D printing crown and bridge resin

Three-dimensional (3D) printing, otherwise known as additive manufacturing in a non-technical context, is becoming increasingly popular in the field of dentistry. As an essential step in the 3D printing process, postwashing with organic solvents can damage the printed resin polymer and possibly pose a risk to human health. The development of water-washable dental resins means that water can be used as a washing agent. However, the effects of washing agents and washing times on the mechanical and biocompatibility properties of water-washable resins remain unclear. This study investigated the impact of different washing agents (water, detergent, and alcohol) and washing time points (5, 10, 20, and 30 min) on the flexural strength, Vickers hardness, surface characterization, degree of conversion, biocompatibility, and monomer elution of 3D printed samples. Using water for long-term washing better preserved the mechanical properties, caused a smooth surface, and improved the degree of conversion, with 20 min of washing with water achieving the same biological performance as organic solvents. Water is an applicable agent option for washing the 3D printing water-washable temporary crown and bridge resin in the postwashing process. This advancement facilitates the development of other water-washable intraoral resins and the optimization of clinical standard washing guidelines.

Evaluation of the amount of residual monomer released from different flowable composite resins

Today, resin materials are used in the restoration of permanent and deciduous teeth or as fissure sealants. The materials can contain different types of monomers (Bis-GMA, UDMA, TEGDMA). These monomers can be released into the oral cavity after polymerization. Residual monomers released from resin-containing restorative materials after polymerization have been reported to have negative effects on mechanical properties. The aim of our study is to evaluate the amount of residual monomers released after polymerization of different flowable composite resin materials using two different modes of LED light source. Composite disc samples (8 mm diameter/2 mm depth) prepared for each material group were polymerized using two different modes of the LED light device (Standard mode and extra power mode). HPLC (High Performance Liquid Chromatography) device was used to measure the amount of residual monomer release at 1 h, 1 day, 3 days and 7 days periods. Pairwise comparison of the differences between the materials was performed by Post-hoc test. For each residual monomer, the Kruskal Wallis test was used to analyze the difference between the materials in standard mode and the difference between the materials in extra power mode. According to the results of the study; Grandio flow flowable composite showed the highest release of TEGDMA and Bis-GMA while SDR® Flow flowable composite showed the lowest release of TEGDMA, Bis-GMA and UDMA. For all materials, the extra power mode resulted in more residual monomer release. TEGDMA and Bis-GMA release was detected in all tested flowable composites at all time periods.

Gustation-Inspired Dual-Responsive Hydrogels for Taste Sensing Enabled by Machine Learning

Human gustatory system recognizes salty/sour or sweet tastants based on their different ionic or nonionic natures using two different signaling pathways. This suggests that evolution has selected this detection dualism favorably. Analogically, this work constructs herein bioinspired stimulus-responsive hydrogels to recognize model salty/sour or sweet tastes based on two different responses, that is, electrical and volumetric responsivities. Different compositions of zwitter-ionic sulfobetainic N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (DMAPS) and nonionic 2-hydroxyethyl methacrylate (HEMA) are co-polymerized to explore conditions for gelation. The hydrogel responses upon adding model tastant molecules are explored using electrical and visual de-swelling observations. Beyond challenging electrochemical impedance spectroscopy measurements, naive multimeter electrical characterizations are performed, toward facile applicability. Ionic model molecules, for example, sodium chloride and acetic acid, interact electrostatically with DMAPS groups, whereas nonionic molecules, for example, D(-)fructose, interact by hydrogen bonding with HEMA. The model tastants induce complex combinations of electrical and volumetric responses, which are then introduced as inputs for machine learning algorithms. The fidelity of such a trained dual response approach is tested for a more general taste identification. This work envisages that the facile dual electric/volumetric hydrogel responses combined with machine learning proposes a generic bioinspired avenue for future bionic designs of artificial taste recognition, amply needed in applications.

Effect of repeated preheating on monomer elution from a bulk-fill composite resin

Background

Due to incomplete polymerization of composite resin restorations, residual monomers adversely affect their mechanical properties and biocompatibility. Preheating of composite resins is advised to increase the degree of conversion and reduce monomer elution. This study aimed to analyze the effect of preheating and repeated preheating on the amount of monomer released from a bulk-fill composite resin.

Methods

Forty samples were prepared using Filtek One Bulk Fill Restorative composite resin. Samples in one group were fabricated at room temperature, whereas the composite resins in the other groups were cured after 1, 10, or 20 repeated preheating cycles (55 °C), 10 in each group. Eluted urethane dimethacrylate (UDMA) and bisphenol-A-glycidylmethacrylate (BisGMA) monomers were measured with high-performance liquid chromatography (HPLC) 24 hours and 30 days after immersion. The data were evaluated using one-way ANOVA and post hoc Tukey tests. Paired-sample t tests were used to test the differences between time intervals.

Results

At both time intervals, the greatest amounts of released BisGMA, UDMA, and total monomers were obtained from the control group, whereas 10 preheating cycles resulted in the least monomer elution. The decrease in monomer elution was not statistically significant after 10 preheating cycles compared with that after one preheating cycle (P>0.05). The group with 20 preheating cycles showed a greater amount of monomer elution compared to that with 1 and 10 cycles, which was statistically significant (P < 0.05). The amount of released monomers on day 30 was significantly higher than on day 1 (P<0.01).

Conclusion

Preheating of the bulk-fill composite resin was shown to be effective in reducing monomer elution. However, monomer elution was adversely affected after repeated preheating cycles of 20.

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.

Effect of Storage Temperature on Selected Strength Parameters of Dual-Cured Composite Cements

Direct restorations are currently the most popular restorations used in dental prosthodontics. Due to the increased requirements for materials used in the fabrication of fixed restorations, there is a need for evaluation of strength parameters of these materials, including dental cements. The present study investigated the change in selected strength parameters of four dual-cured composite cements as a function of storage temperature. The following were investigated: three-point flexural strength (FS), flexural modulus in bending (FM), diametral tensile strength (DTS) and Vickers hardness (HV). Four dual-cured composite cements were tested, i.e., Multilink Automix (Ivoclar Vivadent), seT PP (SDI), MaxCem (Kerr), and Bifix Hybrid Abutment (VOCO). Each of the tested cements was stored for 7 days at one of the selected temperatures: 8 °C, 15 °C, 25 °C, or 35 °C, before the samples were made. Strength properties (DTS, FS) are not strongly dependent on the storage temperature in the range of 8-35 °C. Some statistical differences were observed between the hardness of MaxCem and Multilink Automix storage in various temperatures. FS and FM were lowest for Bifix Hybrid Abutment, MaxCem and Multilink Automix storage at 25 °C, and highest for Bifix Hybrid Abutment, MaxCem, and seT PP stored in 35 °C. The cement with the highest filler content (70% by weight) showed the highest FS and HV.

Influence of the Polymerization Modes on the Methacrylic Acid Release from Dental Light-Cured Materials-In Vitro Study

The study focuses on the problem of lowering the pH around a composite filling concerning the polymerization modes and methacrylic acid release, which may affect not only the oral health but also the whole organism. A total of 90 specimens (30 of each: Filtek Bulk Fill, Evetric and Riva LC) were placed in 90 sterile hermetic polyethene containers with saline and incubated at 37 °C. Ten samples of each material were light-cured for 40 s with one of the three curing modes: full power mode (FPM), ramping mode (RM) and pulse mode (PM). The pH and methacrylic acid release evaluation were performed at the following time points: after 2 h and after 3, 7, 21 and 42 days from the specimen preparation. Regardless of light-curing mode, all used materials were characterized by a gradual elevation in methacrylic acid concentration. Only for Filtek Bulk Fill, increased methacrylic acid release was closely associated with lower pH. The choice of the polymerization mode has no significant influence on the methacrylic acid release. However, further research about composite light-curing is necessary to create the procedure algorithm, reducing the local and systemic complications associated with composite fillings.

N-Acetyl Cysteine-Mediated Improvements in Dental Restorative Material Biocompatibility

The fibroblast-rich gingival tissue is usually in contact with or adjacent to cytotoxic polymer-based dental restoration materials. The objective of this study was to determine whether the antioxidant amino acid, N-acetyl cysteine (NAC), reduces the toxicity of dental restorative materials. Human oral fibroblasts were cultured with bis-acrylic, flowable composite, bulk-fill composite, self-curing acrylic, and titanium alloy test specimens. Cellular behavior and function were analyzed on and around the materials. Impregnation of the bulk-fill composite and self-curing acrylic with NAC reduced their toxicity, improving the attachment, growth, and function of human oral fibroblasts on and around the materials. These mitigating effects were NAC dose dependent. However, NAC impregnation of the bis-acrylic and flowable composite was ineffective, with no cells attaching to nor around the materials. Although supplementing the culture medium with NAC also effectively improved fibroblast behaviors, direct impregnation of materials with NAC was more effective than supplementing the cultures. NAC-mediated improvements in fibroblast behavior were associated with reduced production of reactive oxygen species and oxidized glutathione together with increased glutathione reserves, indicating that NAC effectively directly scavenged ROS from materials and reinforced the cellular antioxidant defense system. These results establish a proof of concept of NAC-mediated improvements in biocompatibility in the selected dental restorative materials.

Comparative chemical properties, bioactivity, and cytotoxicity of resin-modified calcium silicate-based pulp capping materials on human dental pulp stem cells

OBJECTIVES

This study investigated the cytotoxicity, the residual monomer release, degree of conversion (DC), calcium ion (Ca²⁺) release, and crystal structure of TheraCal PT (ThPT) by comparison with TheraCal LC (ThLC) and mineral trioxide aggregate (MTA).

MATERIALS AND METHODS

The cytotoxicity of the cured materials was evaluated on human dental pulp stem cells (hDPSCs) isolated from third molars by the water-soluble tetrazolium salt (WST-1) method. The monomer release and DC of the resin-containing materials were analyzed by high-performance liquid chromatography (HPLC) and Fourier transform infrared (FTIR), respectively. The chemical composition and Ca²⁺ release of the materials were determined by scanning electronic microscopy-energy-dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. Statistical differences were evaluated with one-way ANOVA, repeated measure ANOVA, and the Tukey test (p < 0.05).

RESULTS

MTA showed significantly lower cytotoxicity than either ThLC or ThPT after 1, 3, and 7 days (p < 0.05). TEGDMA release of ThPT is significantly higher than ThLC (p < 0.05). All materials showed calcium Ca²⁺ release, with MTA significantly higher than the others (p < 0.05).

CONCLUSIONS

MTA showed low cytotoxicity and high Ca²⁺ release compared to ThLC and ThPT.

CLINICAL RELEVANCE

The cytotoxicity and residual monomer release of ThLC and ThPT may raise concerns about the viability of hDPSCs. Further investigations with the use of in vivo research models are required to validate in vitro bioactivity properties and the potential adverse biological effects of ThLC and ThPT on hDPSCs.

Analysis of Monomer Release from Different Composite Resins after Bleaching by HPLC

(1) Background: This study aimed to examine the effect of bleaching agents on the release of triethylenae glycol dimethacrylate, 2-hydroxyethyl methacrylate, bisphenol A, urethane dimethacrylate, and bisphenol A-glycidyl methacrylate monomers, which are released from different composite resins, using the high-performance liquid chromatography (HPLC) method. (2) Methods: Ninety disc-shaped specimens were produced and immersed in artificial saliva. After different bleaching applications [office type bleaching (OB) and home type bleaching (HB)], the specimens were immersed in a 75 wt% ethanol/water solution, and the released monomers were analyzed by HPLC at predefined time intervals: 1, 7, and 28 days. The Kruskal−Wallis and Mann−Whitney U tests were conducted for statistical analysis (p = 0.05). (3) Results: The monomers were released at all times from all composite specimens. The monomer release was increased over time. The highest monomer release was detected on day 28. Bleaching applications affected monomer release. No statistical difference was found between OB and HB applications (p > 0.05). The most released monomer was Bisphenol-A in all composites. (4) Conclusion: Given that a residual monomer release from composite resins has a toxic effect and that bleaching treatments increase this release, a treatment protocol should be made in accordance with the manufacturer’s instructions.

Investigating the Cytotoxicity of Dual-Cure Bulk-Fill Resin Materials on L929 Cells

The aim of this in vitro study was to investigate cytotoxic effects of dual-cure bulk-fill resin materials polymerized with a third-generation LED light-curing unit (LCU) on L929 fibroblast cells in terms of morphology and viability. Three novel dual-cure, flowable bulk-fill materials (Fill-Up!™), a bioactive material (ACTIVA™ BioACTIVE-RESTORATIVE™), and a dual-cure bulk-fill composite material (HyperFIL® HAp) polymerized by LED LCU (VALO™ Cordless) were tested. Each material was placed in plastic rings (4 mm × 5 mm) in a single layer. Unpolymerized rings filled with each material were placed in direct contact with cells and then polymerized. After polymerization, the removed medium was readded to wells. In this study, four control groups were performed: the medium-free control group, medium control group, physical control group, and light applied control group. Three samples were prepared from each group. After 24 h, the morphology of cells was examined and a WST-1 test was performed. The percentage of cell viability (PCV) of each group was calculated. The experiment was repeated three times. Data were analyzed by a Kruskal–Wallis Test and a Mann–Whitney U test. p < 0.05 was considered significant. The PCV of all groups were found to be significantly lower than the medium control group (p < 0.05). The lowest PCV was obtained in HyperFIL® Hap, while highest was in the Fill-Up!™. In the morphology of cells related to the experimental groups, it was observed that the spindle structures of cells were disrupted due to cytotoxicity; cells became rounded and intercellular space increased. There were no significant differences between the control groups (p > 0.05). All control groups showed acceptable PCV (>70%) and cells were spindle-like, similar to the original fibroblast cells. It can be suggested that clinicians should pay attention when applying dual-cure bulk-fill materials in deep cavities, or they should use a liner material under these materials.

Methacrylate Polymers With “Flipped External” Ester Groups: A Review

Current resin composites have favorable handling and upon polymerization initial physical properties that allow for efficient material replacement of removed carious tooth structure. Dental resin composites have long term durability limitations due to the hydrolysis of ester bonds within the methacrylate based polymer matrix. This article outlines the importance of ester bonds positioned internal to the carbon-carbon double bond in current methacrylate monomers. Water and promiscuous salivary/bacterial esterase activity can initiate ester bond hydrolysis that can sever the polymer backbone throughout the material. Recent studies have custom synthesized, with the latest advances in modern organic chemical synthesis, a novel molecule named ethylene glycol bis (ethyl methacrylate) (EGEMA). EGEMA was designed to retain the reactive acrylate units. Upon intermolecular polymerization of vinyl groups, EGEMA ester groups are positioned outside the backbone of the polymer chain. This review highlights investigation into the degradation resistance of EGEMA using buffer, esterase, and microbial storage assays. Material samples of EGEMA had superior final physical and mechanical properties than traditional ethylene glycol dimethacrylate (EGDMA) in all degradation assays. Integrating bioinformatics-based biodegradation predictions to the experimental results of storage media analyzed by LC/GC-MS revealed that hydrolysis of EGEMA generated small amounts of ethanol while preserving the strength bearing polymer backbone. Prior studies support investigation into additional custom synthesized methacrylate polymers with “flipped external” ester groups. The long term goal is to improve clinical durability compared to current methacrylates while retaining inherent advantages of acrylic based chemistry, which may ease implementation of these novel methacrylates into clinical practice.

Monomer release from dental restorative materials containing dimethacrylate resin after bleaching

OBJECTIVE

The aim of this study is to determine the type and amount of monomer released over time after bleaching was applied to dental restorative materials containing dimethacrylate resin.

MATERIALS AND METHODS

Thirteen different restorative materials containing dimethacrylate resin were used in this study. Twenty samples were prepared from each material and the samples were randomly divided into 4 subgroups, namely, office bleaching, home bleaching, and separate control group for each of the bleaching methods. After bleaching, the samples were stored in 75% ethanol solution for 1, 14, and 28 days. Analysis of the samples collected to determine the type and amount of residual monomer released from the materials was performed using a liquid chromatography-tandem mass/mass spectrometer (LC-MS/MS). Data were analyzed using Friedman and Kruskal-Wallis tests. Statistical significance level was taken as p < 0.05.

RESULTS

In terms of bleaching groups, mostly no significant difference was found between the groups in each time period in restorative materials (p > 0.05). In terms of time periods, it was determined that the amount of release of all monomers was decreased over time. In terms of restorative materials, the highest monomer release was detected in composite resin groups and the least monomer release was detected in CAD/CAM blocks.

CONCLUSION

Although monomers were released from all materials, bleaching did not affect the amount of released monomer. Amounts of released monomers were generally below toxic limits.

CLINICAL RELEVANCE

Within the limits of this study, bleaching does not significantly affect monomer release in restorative materials containing dimethacrylate resin.

Modeling Liquids and Resin-Based Dental Composite Materials—A Scoping Review

Several lubricant materials can be used to model resin-based composites (RBCs) during restorative procedures. Clinically, instruments or brushes are wet with bonding agents (BAs) or modeling liquids (MLs) for sculpturing purposes. However, a knowledge gap exists on their effects on the mechanical properties of RBCs, requiring greater insight. Five databases were searched, including 295 in vitro studies on the use of lubricant materials for modeling RBCs during restorative procedures. Only articles in the English language were included, with no limits on the publication date. The last piece of research was dated 24 March 2022. In total, 16 studies were included in the review process, together with a paper retrieved after screening references. A total of 17 BAs and 7 MLs were investigated. Tensile (n = 5), flexural strength (n = 2), water sorption (n = 2), color stability (n = 8) and translucency (n = 3), micro-hardness (n = 4), roughness (n = 3), degree of conversion (n = 3), and monomer elution (n = 2) tests were carried out. In general, a maximum of 24 h of artificial storage was performed (n = 13), while four papers tested the specimens immediately. The present review identifies the possibilities and limitations of modeling lubricants used during restorative procedures on the mechanical, surface, and optical properties of RBCs. Clinicians should be aware that sculpturing RBCs with modeling resins might influence the composite surface properties in a way that is material-dependent.

Resin-based composite materials: elution and pollution

Pollution arises from all human activity and the provision of oral healthcare using resin-based composite restorative materials (RBCs) should be considered. This paper aims to provide a comprehensive review of the potential pollutant risk to the environment from the chemical compounds found in resin-based restorative materials, by including: 1) the principal pollutant compounds present in the resin matrix; 2) the degradation process of RBCs and its consequences; 3) the methods used for the detection and quantification of monomer elution and RBC microparticles; and 4) a review of the release mechanisms of eluates and RBC microparticles into the environment.

RBCs are pollutants by virtue of the compounds created during the degradation processes. These are in the form of the constituent eluted monomers and microparticles. Their impact on the environment and biodiversity is unknown. These materials are currently one of the main direct-placement restorative materials and their success is unquestionable when used and maintained correctly. Mitigation strategies for reducing the impact of pollution on the environment should be considered and implemented by all stakeholders and processes in the supply chain, from manufacturing, clinical use and waste management.

All the constituent components of resin-based composites have the potential to act as environmental pollutants as a consequence of their breakdown and subsequent elution.

Microparticles have a pollution potential as they are easily dispersed in solution and have an increased surface area that potentiates the elution of monomers.

Strategies to reduce their pollution impact should include: a) development of innovative direct-placement restorative materials; b) minimising waste; and c) providing good-quality preventive dentistry that minimises restoration failure and requirement for replacement.

Galloylated proanthocyanidins in dentin matrix exhibit biocompatibility and induce differentiation in dental stem cells

Aim

Grape seed extract contains a complex mixture of proanthocyanidins (PACs), a plant biopolymer used as a biomaterial to improve reparative and preventive dental therapies. Co-polymerization of PACs with type I collagen mechanically reinforces the dentin extracellular matrix. This study assessed the biocompatibility of PACs from grape seed extract on dental pulp stem cells (DPSCs) in a model simulating leaching through dentin to the pulp cavity. The aim was to determine the type of PACs (galloylated vs. non-galloylated) within grape seed extract that are most compatible with dental pulp tissue.

Methodology

Human demineralized dentin was treated with selectively-enriched dimeric PACs prepared from grape seed extract using liquid-liquid chromatography. DPSCs were cultured within a 2D matrix and exposed to PAC-treated dentin extracellular matrix. Cell proliferation was measured using the MTS assay and expression of odontoblastic genes was analyzed by qRT-PCR. Categorization of PACs leaching from dentin was performed using HPLC-MS.

Results

Enriched dimeric fractions containing galloylated PACs increased the expression of certain odontoblastic genes in DPSCs, including Runt-related transcription factor 2 (RUNX2), vascular endothelial growth factor (VEGF), bone morphogenetic protein 2 (BMP2), basic fibroblast growth factor (FGF2), dentin sialophosphoprotein (DSPP) and collagen, type I, alpha 1 (COLI). Galloylated dimeric PACs also exhibited minor effects on DPSC proliferation, resulting in a decrease compared to control after five days of treatment. The non-galloylated dimer fraction had no effect on these genes or on DPSC proliferation.

Conclusions

Galloylated PACs are biocompatible with DPSCs and may exert a beneficial effect on cells within dental pulp tissue. The observed increase in odontoblastic genes induced by galloylated PACs together with a decrease in DPSC proliferation is suggestive of a shift toward cell differentiation. This data supports the use of dimeric PACs as a safe biomaterial, with galloylated dimeric PACs exhibiting potential benefits to odontoblasts supporting dentin regeneration.

Effect of natural and commercially produced juices on colour stability of microhybrid and nanohybrid composites

Objective

This study aims to evaluate the discoloration rate of two types of composites, microhybrid and nanohybrid, after exposure to natural and commercially-produced juices.

Materials and methods

In this experimental study, 90 disc-shaped specimens with a thickness of 2 mm and a diameter of 10 mm were taken from two composites, microhybrid P₄ (Kerr-ITALY) and nanohybrid Filtek Z250XT (3M-ESPE-USA) (two groups of 45). Then, the samples of each group were divided into five subgroups of nine and were immersed for 10 days for 4 h in five solutions of commercially-produced orange juice, natural orange juice, commercially-produced pomegranate juice, natural pomegranate juice, and distilled water (control group). The colour of the samples was measured by a reflective spectrophotometer using the CLEl*a*b colour space at baseline and after discoloration.

Result

The independent t-test showed that the mean discoloration rate (∆E) of nanohybrid composite exposed to commercially-produced orange juice, natural pomegranate juice, and commercially-produced pomegranate juice was significantly higher than microhybrid composite (P < 0.01). In addition, the test found that the highest discoloration rate of the nanohybrid composite was related to the effect of commercially-produced orange juice (∆E = 13.03) and the highest discoloration rate of microhybrid composite was related to the effect of natural pomegranate juice (∆E = 4.79).

Conclusion

According to the results, it seems that microhybrid composites are more resistant to discoloration than nanohybrid composites. According to the results, consumption of dyed drinks, particularly natural pomegranate juice, commercially-produced orange juice, and commercially-produced pomegranate juice, is not recommended in the first few days after composite restoration.

Influence of curing modes on monomer elution, sorption and solubility of dual-cure resin-cements

OBJECTIVE

To explore the effect of two curing modes, for dual-cure resin cements, on their monomer elution, water sorption and solubility after 30 d water storage and 30 d dry reconditioning.

METHODS

Eight dual-cure resin-cements were investigated (Bifix SE, Nexus Third Generation, PANAVIA SA, PANAVIA V5, RelyX Ultimate Universal, RelyX Unicem 2, RelyX Universal and SpeedCEM Plus). Six disk-shaped specimens were made per curing mode: light-cure (LC) versus self-cure (SC) to measure amounts of eluted monomers after 30 d of water storage at 37 °C. Ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC MS/MS) was performed to identify and quantify three eluted monomers (Bis-GMA, UDMA and TEGDMA). Water sorption/ solubility specimens were prepared according to ISO 4049. Specimens from each curing mode (LC/SC) were immersed separately in distilled water for 30 d and then reconditioned for 30 d; all at 37 °C. Mass change was measured at different time intervals. Data were analyzed via one-way ANOVA, Tukey post-hoc tests and independent sample t-tests (α = 0.05).

RESULTS

After 30 d of water storage, the three monomers Bis-GMA, UDMA and TEGDMA were detected in water. All monomers showed a variable extent of elution into water and were significantly higher (p < 0.0001) with SC compared to LC curing modes. BSE had the highest quantity of eluted monomers. After 30 d of water sorption (μg/mm³), all rein-cements showed significantly higher sorption (p < 0.05) of SC compared to LC curing modes except for PV5, RXU and CEM (p > 0.05). After 30 d of water solubility (μg/mm³), all resin-cements showed significantly higher solubility (p < 0.0001) of SC compared to LC curing mode. BSE had the highest water sorption and solubility. The total amounts of eluted monomers correlated positively with solubility: r² = 0.95 for LC and r² = 0.93 for SC.

SIGNIFICANCE

Whenever light access is possible, light curing remains beneficial to reduce the extent of resin degradation and related properties of dual-cure resin cements. BSE showed statistically the highest extent of eluted monomers, sorption and solubility.

Effect of Adhesive Resin as a Modeling Liquid on Elution of Resin Composite Restorations

Background

Adhesive resin is increasingly used as a modeling liquid for composite. Based on previous studies, elution of some components from the composite mass negatively affects the oral tissues. Since few studies have focused on the effect of adhesive resin on composite mass, this study aimed to investigate the effect of dental adhesion factors as modeling liquid on the elution of substances from composite restorations.

Materials and Methods

Sixty-four composite specimens (6 × 2 mm diameter × height) were prepared in four groups (n = 16) by using a Teflon ring. Composite mass was incrementally applied in four layers (0.5 mm). The control group contained no material between the layers, but other groups had one of the single bond, SE bond, and wetting resin adhesives between the layers. Specimens were immersed in distilled water and methanol. The amount of released triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and camphorquinone (CQ) was monitored by gas chromatography after 24 hours and 7 days. Data were analyzed with SPSS software through Kruskal–Wallis and Mann–Whitney U tests (α = 0.05).

Results

The highest rate of released TEGDMA comonomer was seen in the wetting resin group in the water medium. The highest rate of released UDMA monomer was seen in SE bond and wetting resin groups in the methanol medium after 24 hours. The highest amount of released CQ in the methanol medium was observed in the SE bond group after 7 days.

Conclusion

Single bond adhesive can be used as modeling liquid since it has no significant effect on the elution of components from composite mass. Whereas, wetting resin and SE bond adhesives are not suitable to be used as modeling liquid due to the high amounts of released TEGDMA and UDMA.

Preparation of new bio-based antibacterial acrylic bone cement via modification with a biofunctional monomer of nitrofurfuryl methacrylate

The new bio-based antibacterial p(NFMA-co-MMA) bone cement exhibits excellent antibacterial performance in the treatment of osteoporotic vertebral compression fracture.

Effect of post-polymerization with autoclaving treatment on monomer elution and mechanical properties of 3D-printing acrylic resin for splint fabrication

OBJECTIVES

To evaluate the effect of post-treatment autoclaving on monomer elution and mechanical properties of three-dimensionally (3D) printed resin for splint fabrication.

METHODS

Photopolymer resin specimens (Dental LT Clear) were 3D-printed and processed according to the manufacturer's instructions. The specimens were randomly divided to different post-treatment protocols: water storage, autoclaving at different temperatures (121 °C or 132 °C), times (4 or 30 min) and no treatment as a control. The elution of UDMA, HEMA, and EGDMA monomers was determined using high-performance liquid chromatography (HPLC) by immersing the specimens in 75% ethanol for 72 h. The flexural modulus, surface microhardness and linear dimensional changes were measured. The monomer elution and flexural modulus were statistically analyzed using Welch's ANOVA followed by Dunnett's T3 tests, while the surface microhardness and dimensional changes were analyzed using one-way ANOVA followed by Bonferroni tests (α = 0.05).

RESULTS

The overall monomer elution concentrations were significantly highest for the control group and lowest for specimens treated in an autoclave at 132 °C for 4 min. The flexural modulus was not significantly different between all groups. The surface microhardness was significantly higher for all autoclaved groups than the control and water storage groups. The linear expansion was significantly higher after post-treatment autoclaving in contrast to water storage.

SIGNIFICANCE/CONCLUSIONS

Post-polymerization autoclave treatment of the 3D-printed resin reduced monomer elution and improved surface microhardness without deteriorating the flexural modulus. Post-treatment with an autoclave at 132 °C for 4 min can be recommended for 3D-printed resin for splint fabrication.

An updated review on application of 3D printing in fabricating pharmaceutical dosage forms

The concept of "one size fits all" followed by the conventional healthcare system has drawbacks in providing precise pharmacotherapy due to variation in the pharmacokinetics of different patients leading to serious consequences such as side effects. In this regard, digital-based three-dimensional printing (3DP), which refers to fabricating 3D printed pharmaceutical dosage forms with variable geometry in a layer-by-layer fashion, has become one of the most powerful and innovative tools in fabricating "personalized medicine" to cater to the need of therapeutic benefits for patients to the maximum extent. This is achieved due to the tremendous potential of 3DP in tailoring various drug delivery systems (DDS) in terms of size, shape, drug loading, and drug release. In addition, 3DP has a huge impact on special populations including pediatrics, geriatrics, and pregnant women with unique or frequently changing medical needs. The areas covered in the present article are as follows: (i) the difference between traditional and 3DP manufacturing tool, (ii) the basic processing steps involved in 3DP, (iii) common 3DP methods with their pros and cons, (iv) various DDS fabricated by 3DP till date with discussing few research studies in each class of DDS, (v) the drug loading principles into 3D printed dosage forms, and (vi) regulatory compliance.

Assessing the estrogenic activity of chemicals present in resin based dental composites and in leachates of commercially available composites using the ERα-CALUX bioassay

OBJECTIVE

The biocompatibility of resin based dental composites has not yet been fully characterized even though certain monomers used in these composites are synthesized from Bisphenol A (BPA), a well-known estrogenic endocrine disruptor. As a result, they show structural relationship to BPA and can contain it as an impurity. Therefore, the estrogenic activity of 9 monomers, 2 photoinitiators, one photostabilizer and leachates of 4 commercially available composites was determined.

METHODS

The ERα-CALUX bioassay was used to determine both agonistic and antagonistic estrogenic activities of the pure compounds (BPA, BisDMA, BisGMA, BisEMA(3), BisEMA(6), BisEMA(10), TEGDMA, TCD-DI-HEA, BADGE, UDMA, HMBP, DMPA, CQ) and the leachates of cured composite disks. The leachates of 4 commercially available composites (Solitaire 2, Ceram.x Spectra ST, G-ænial Posterior and Filtek Supreme XTE) in water and 0.1 M NaOH (pH = 13, 'worst-case scenario') were tested for estrogenic activity (pooled leachates from 10 cured composite disks).

RESULTS

Agonistic estrogenic activity was found for the monomer BisDMA, the photostabilizer HMBP and photoinitiator DMPA. All leachates from the 4 tested composites showed significant agonistic estrogenic activity higher than the DMSO control, and the highest activity (potency and efficacy) was found for Solitaire 2, followed by Ceram.x Spectra ST. Furthermore, antagonistic estrogenic activity was found in the leachates from G-ænial Posterior.

SIGNIFICANCE

These results show that significant estrogenic activity was found in all leachates of the cured composite disks, and that this estrogenicity is most likely due to a mixture effect of multiple estrogenic compounds (including BPA, HMBP and DMPA). This indicates that further research into the endocrine activity of all the compounds that are present in these composites (even at low quantities) and their possible mixture effect is warranted to guarantee their safe use.

Cytotoxic Evaluation and Determination of Organic and Inorganic Eluates from Restorative Materials

Over the last years, diverse commercial resin-based composites have dominated as dental filling materials. The purpose of the present study was to determine organic and inorganic eluates from five restorative materials using GC/MS and ICP–OES and to compare the effect on cell survival of human gingival fibroblasts of a conventional and a bioactive resin. Five commercially available restorative materials were employed for this study: Activa^TM Bioactive Restorative, ENA HRi, Enamel plus HRi Biofunction, Fuji II LC Capsule, and Fuji IX Capsule. Disks that were polymerized with a curing LED light or left to set were immersed in: 1 mL methanol or artificial saliva for GC/MS analysis, 5mL deionized water for ICP–OES, and 5mL of culture medium for cell viability. Cell viability was investigated with a modified staining sulforhodamine B assay.The following organic substances were detected: ACP, BHT, BPA, 1,4-BDDMA, CQ, DBP, DMABEE, HEMA, MCE, MeHQ, MOPA, MS, TMPTMA, and TPSb and the ions silicon, aluminum, calcium, sodium, and barium. Activa Bioactive Restorative was found to be biocompatible. Elution of organic substances depended on material’s composition, the nature of the solvent and the storage time. Ions’ release depended on material’s composition and storage time. The newly introduced bioactive restorative was found to be more biocompatible.

Cytotoxicity and estrogenicity in simulated dental wastewater after grinding of resin-based materials

OBJECTIVE

This study evaluated the cytotoxic and estrogenic effects of dust and eluates released into simulated wastewater after grinding of dental resin-based materials.

METHODS

Four materials were used: ceram.x® universal, Filtek™ Supreme XTE, Lava™ Ultimate and Core-X™ flow. From each composite material, samples (5 × 2 mm, n = 50) were prepared according to the manufacturers' instructions. Lava™ Ultimate was used as blocks. All samples were ground to dust with a diamond bur (106 μm) and suspended in distilled water at 60 mg/mL. After storage for 72 h, the suspensions were separated into a soluble (eluate) and a particulate (dust) fraction. Eluates and dusts were evaluated for inhibition of Vibrio fischeri bioluminescence and cytotoxicity on human A549 lung cells (WST-1-Assay). The estrogenic activity was assessed by YES-Assay using Saccharomyces cerevisiae. Additionally, dental monomers (BisGMA, BisEMA, UDMA, TEGDMA, HEMA) and Bisphenol A were investigated.

RESULTS

All eluates showed inhibition of V. fischeri bioluminescence at concentrations above 1.1 mg/mL (p < 0.05). The activity of the eluates of ceram.x® universal and Filtek™ Supreme XTE was significantly higher than Lava™ Ultimate and Core-X™ flow (p < 0.05). In the WST-1-Assay, all materials induced cytotoxic effects at concentrations of 0.1 mg/mL (p < 0.05), while no significant differences were detected among them. The tested materials revealed no estrogenic activity. All dental monomers and Bisphenol A showed concentration dependent cytotoxic effects (p < 0.05), whereas only Bisphenol A induced an estrogenic effect (p < 0.01).

SIGNIFICANCE

Dust and eluates of resin-based dental materials released into wastewater exert bactericidal and cytotoxic effects in vitro. However, they reveal no estrogenic effect.

Recent update on potential cytotoxicity, biocompatibility and preventive measures of biomaterials used in dentistry

Dental treatment is provided for a wide variety of oral health problems like dental caries, periodontal diseases, periapical infections, replacement of missing teeth and orthodontic problems. Various biomaterials, like composite resins, amalgam, glass ionomer cement, acrylic resins, metal alloys, impression materials, bone grafts, membranes, local anaesthetics, etc., are used for dental applications. The physical and chemical characteristics of these materials influence the outcome of dental treatment. It also impacts on the biological, allergic and toxic potential of biomaterials. With innovations in science and their positive results, there is also a need for awareness about the biological risks of these biomaterials. The aim of dental treatment is to have effective, yet safe, and long-lasting results for the benefit of patients. For this, it is important to have a thorough understanding of biomaterials and their effects on local and systemic health. Materials used in dentistry undergo a series of analyses before their oral applications. To the best of our knowledge, this is the first and original review that discusses the reasons for and studies on the toxicity of commonly used biomaterials for applications in dentistry. It will help clinicians to formulate a methodical approach for the selection of dental biomaterials, thus providing an awareness for forecasting their risk of toxic reactions.

Safety and In Situ Antierosive Effect of CaneCPI-5 on Dental Enamel

The sugarcane cystatin (CaneCPI-5) was recently cloned and showed strong binding force to dental enamel and protection against initial erosion. However, evaluations on its safety and efficacy in a situation closer to the clinical condition are necessary. In the present study we analyzed 1) the cytotoxicity of CaneCPI-5 on human gingival fibroblasts (HGFs); 2) the ability of CaneCPI-5 to reduce enamel erosion and erosion+abrasion in situ. In part 1, HGFs were treated with CaneCPI-5 (0.025, 0.05, 0.1, 0.5 or 1.0 mg/mL) or no treatment (control). The cytotoxicity was assessed after 60 s and 24 h by mitochondrial activity (MTT), confocal microscopy, and hematoxylin/eosin staining. In part 2, 15 volunteers participated in a double-blind crossover protocol consisting of 3 phases, according to the following treatments: 1) 0.1 mg/mL CaneCPI-5; 2) SnCl₂/NaF/AmF (Elmex; positive control); 3) water (negative control). The volunteers wore an appliance containing 4 bovine enamel specimens for 5 d. Each day, the specimens were individually treated with 50 µL of the tested solutions per 60 s and then subjected to erosive challenges (0.1% citric acid, pH 2.5, for 90 s, 4 times per day). After the first and last erosive challenge each day, 2 samples were abraded (toothbrushing, 15 s). Enamel wear was measured by contact profilometry. One or two-way analysis of variance (ANOVA)/Tukey's or Sidak's tests (P < 0.05) were applied. Regardless of the concentration and the experimental time, CaneCPI-5 did not decrease the cell viability compared to the negative control (P < 0.05). Erosion+abrasion led to significantly greater wear compared to erosion only. For both conditions, the lowest wear was found for SnCl₂ and CaneCPI-5, which did not differ significantly from each other, but showed significant protection when compared to the negative control. In conclusion, CaneCPI-5 is safe on HGFs and reduces enamel erosive wear to the same extent as a commercial solution used to control erosive tooth wear (ETW).

Physical Characterization of Bismuth Oxide Nanoparticle Based Ceramic Composite for Future Biomedical Application

Employment and the effect of eco-friendly bismuth oxide nanoparticles (BiONPs) in bio-cement were studied. The standard method was adopted to prepare BiONPs-composite. Water was adopted for dispersing BiONPs in the composite. A representative batch (2 wt. % of BiONPs) was prepared without water to study the impact of water on composite properties. For each batch, 10 samples were prepared and tested. TGA (thermogravimetric analysis) performed on composite showed 0.8 wt. % losses in samples prepared without water whereas, maximum 2 wt. % weight losses observed in the water-based composite. Presence of BiONPs resulted in a decrease in depth of curing. Three-point bending flexural strength decreased for increasing BiONPs content. Comparative study between 2 wt. % samples with and without water showed 10.40 (±0.91) MPa and 28.45 (±2.50) MPa flexural strength values, respectively, indicating a significant (p < 0.05) increase of the mechanical properties at the macroscale. Nanoindentation revealed that 2 wt. % without water composites showed significant (p < 0.05) highest nanoindentation modulus 26.4 (±1.28) GPa and hardness 0.46 (±0.013) GPa. Usage of water as dispersion media was found to be deleterious for the overall characteristics of the composite but, at the same time, the BiONPs acted as a very promising filler that can be used in this class of composites.

Evaluation of the cytotoxic and genotoxic effects of different universal adhesive systems

Objectives:

The objective of this study was to evaluate and compare the cytotoxicity and genotoxicity of different universal adhesive systems in the mouse fibroblast cell line L929.

Materials and Methods:

L929 (mouse fibroblast) cells were exposed to G-Premio Bond (GPB) (GC Europe, Belgium), Prime&Bond Universal (Dentsply Sirona, USA), Universal Bond Quick (Kuraray, USA), Single Bond (SB) Universal (3M ESPE, USA), and Tokuyama Universal Bond (TB) (Tokuyama, USA). Cell viability was assessed by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide test, whereas oxidative DNA damage was assessed by determining the 8-hydroxydeoxyguanosine level using an enzyme-linked immunoassay kit. Statistical analysis was performed by one-way analysis of variance, followed by Bonferroni post hoc tests.

Results:

Cytotoxic and genotoxic effects of TB and SB Universal groups were significantly higher than the other groups (P < 0.05). Among the adhesives tested, GPB (93.0 ± 1.3) had the least cytotoxicity, while TB (67.3 ± 3.0) had the most cytotoxic effect. In terms of genotoxicity, GPB (2.2 ± 0.3) had the least genotoxic effect, while Tokuyama Bond Universal (4.17 ± 0.4) had the most genotoxic effect.

Conclusions:

Universal adhesive systems used in dentistry have cytotoxic and genotoxic effects in live cells. Universal adhesive systems should, therefore, be used with caution due to their cytotoxic and genotoxic effects in clinical applications.

Urethane Dimethacrylate Influences the Cariogenic Properties of Streptococcus Mutans

Concerns regarding unbound monomers in dental composites have increased with the increased usage of these materials. This study assessed the biological effects of urethane dimethacrylate (UDMA), a common monomer component of dental composite resins, on the cariogenic properties of Streptococcus mutans. Changes in the growth rate, biofilm formation, interaction with saliva, surface hydrophobicity, adhesion, glucan synthesis, sugar transport, glycolytic profiles, and oxidative- and acid-stress tolerances of S. mutans were evaluated after growing the cells in the presence and absence of UDMA. The results indicated that UDMA promotes the adhesion of S. mutans to the underlying surfaces and extracellular polysaccharide synthesis, leading to enhanced biofilm formation. Furthermore, UDMA reduced the acid tolerance of S. mutans, but enhanced its tolerance to oxidative stress, thus favoring the early stage of biofilm development. UDMA did not significantly affect the viability or planktonic growth of cells, but diminished the ability of S. mutans to metabolize carbohydrates and thus maintain the level of intracellular polysaccharides, although the tendency for sugar transport increased. Notably, UDMA did not significantly alter the interactions of bacterial cells with saliva. This study suggests that UDMA may potentially contribute to the development of secondary caries around UDMA-containing dental materials by prompting biofilm formation, enhancing oxidative tolerance, and modulating carbon flow.

The Cytotoxicity Assessment of Novel Formulation Developed to Reduce Dentin Hypersensitivity Utilizing Dehydrogenase Assay

The problem of real treatment of teeth hypersensitivity is still important and unsolved. The main goal of the experiment was to calculate the possible toxic effects on the fibroblasts cells CCL-1™ (NCTC clone 929) caused by original preparation to reduce tooth surfaces’ hypersensitivity, compared to the marketable preparation Seal & Protect (Dentsply). The assessment was made through measuring lactate dehydrogenase (LDH assay). Lactate dehydrogenase releases from the cell’s cytoplasm to the culture medium as a result of cell membrane damage and lysis of the cells. The measurement is based on an assessment of the ability of LDH to oxidize lactic acid to pyruvic acid, which is dependent on the increase of the release level. The increase of LDH activity in the supernatants of cell cultures shows a relationship with the percentage of dead cells (increased cytotoxicity correlates with the increasing content of dead cells). In the LDH assay, both formulations evaluated after 24 h obtained results which were located below the control values. After seven days, the mean values obtained in cytotoxicity assay LDH are measurable and lower for the original formulation in comparison to the commercial one at the dilution of 1:5. At the dilution with 1:10 ratio, they are comparable and within the range of accepted values. At the maximal dilution of 1:15, the results are higher for the experimental formulation in comparison to the marketable formulation. The polymerization process is beneficial for the cytotoxicity test results in case of both tested preparations. Average values of cytotoxicity of both preparations attain an acceptable level of less than 22.6 ± 8.1%, reliant on the degree of dilution and the remark time. Original formulation is characterized by a greater homogeneity of results. The marketable preparation has a larger diversity of effects, dependent on the time of observation and attenuation; however, the cytotoxicity values are lower when paralleled to the experimental formulation in the test conducted after seven days. This should not have a disastrous effect on the pulp, as the values of both as the values of both preparations are within expected ranges. The obtained results allows to assume that will be possible to introduce the original formulation to the stage of clinical trials in the future.

In vitro cytotoxicity of different dental resin-cements on human cell lines

Adhesive resin-cements are increasingly used in modern dentistry. Nevertheless, released substances from resin materials have been shown to cause cellular toxic effects. Disc-shaped specimens from 12 different resin cements and one conventional zinc phosphate cement were prepared and used for direct stimulation of five different human cell lines via transwell cell culture system or in an indirect way using conditioned cell culture media. Cytotoxicity was determined using LDH and BCA assays. All tested cements led to a decrease of cell viability but to a distinct extent depending on cell type, luting material, and cytotoxicity assay. In general, cements exhibited a more pronounced cytotoxicity in direct stimulation experiments compared to stimulations using conditioned media. Interestingly, the conventional zinc phosphate cement showed the lowest impact on cell viability. On cellular level, highest cytotoxic effects were detected in osteoblastic cell lines. All resin cements reduced cell viability of human cells with significant differences depending on cell type and cement material. Especially, osteoblastic cells demonstrated a tremendous increase of cytotoxicity after cement exposure. Although the results of this in vitro study cannot be transferred directly to a clinical setting, it shows that eluted substances from resin cements may disturb osteoblastic homeostasis that in turn could lead to conditions favoring peri-implant bone destruction. Thus, the wide use of resin cements in every clinical situation should be scrutinized. A correct use with complete removal of all cement residues and a sufficient polymerization should be given the utmost attention in clinical usage.

Cytotoxicity assessment of different doses of ozonated water on dental pulp cells

Background

The purpose of this study was to assess the cytotoxicity of various concentrations of ozonated water (OW) on human primary dental pulp cells.

Methods

Human primary dental pulp cells were isolated from exfoliated primary canine teeth of an 11-year-old patient with good systemic and oral health. Afterwards, cells were divided into 6 experimental groups; four groups of OW in concentrations of 2 mg/L, 4 mg/L, 8 mg/L, and 16 mg/L, untreated control group, and cell culture without cells. Cytotoxicity was evaluated after exposure for 5-min exposure using Mosmann’s Tetrazolium Toxicity (MTT) assay at 0 h and 48 h time points. Data were analyzed using a repeated measures analysis of variance and Post-hoc tests were performed using Bonferroni correction for multiple comparisons.

Results

All experimental groups showed proliferation at 0 h time point. However, all groups also experienced a decrease in overtime at 48 h time point (p < 0.05). At both time points 2 mg/L OW showed the highest cell viability as well as proliferation. At 0 h time point, the increase in cell viability for all experimental groups was found statistically significant when compared to positive control group (p < 0.05). At 48 h time point, although 8 mg/L and 16 mg/L OW showed statistically significant reduction in compare to 0 h time point, 2 mg/L and 4 mg/L OW groups didn’t experience any statistically significant difference (p < 0.05).

Conclusion

Considering our findings, due to ozonated water's induced a higher proliferation rate of dental pulp cells, indicating their biocompatibility and a possible adjuvant on irrigating agent in regenerative endodontic procedures.

Class II biocompatible E-Shell 300 3D printing material causes severe developmental toxicity in Danio rerio embryos and reduced cell proliferation in vitro – implications for 3D printed microfluidics

Additive manufacturing is a new technology that represents a highly promising, cheap, and efficient solution for the production of various tools in the biomedicine field. In our study, the toxicity of the commercially available E-Shell 300 series photopolymer, which is used in the manufacture of hearing aids and other implants and which could be potentially exploited in microfluidic device fabrication, was tested using in vivo and in vitro biological models. We examined B14 cell proliferation in direct contact with the three-dimensional (3D)-printed material as well as in water extracts to evaluate in vitro cytotoxicity. Similarly, in vivo tests were performed using an OECD-standardized fish embryo acute toxicity (FET) test on Danio rerio embryos in direct contact with the material and in extracts as well. Despite E-Shell 300 3D-printed material being declared as class-IIa biocompatible, in the case of direct contact with both biological models, the results demonstrated a considerable negative impact on cell proliferation and severe developmental toxicity. In this study, up to 84% reduced cell proliferation in vitro and 79% mortality of in vivo models were observed. In contrast, a negligible toxic influence of E-Shell 300 water extracts was present. Four different post-processing treatments to reduce the toxicity were also tested. We observed that post-printing treatment of 3D-printed material in 96% ethanol can reduce embryonic mortality in the FET test by 71% and also completely eliminate negative effects on cell proliferation. We analyzed leachates from the polymeric structures by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy, and we discovered the presence of surfactant residues. In summary, our results indicate the importance of biocompatibility testing of the 3D printing photopolymer material in direct contact with the given biological model. On the other hand, the possibility of eliminating toxic effects by an appropriate post-processing strategy opens the door for broader applications of E-Shell 300 photopolymers in the development of complex microfluidic devices for various biological applications.

E-Shell 300 3D-printed material demonstrated a considerable negative impact on cell proliferation and severe developmental toxicity due to release of surfactant residues. Post-treatment with ethanol improved the biocompatibility of the material.

Rapid Fabrication of Sterile Medical Nasopharyngeal Swabs by Stereolithography for Widespread Testing in a Pandemic

The 3D printing of nasopharyngeal swabs during the COVID-19 pandemic presents a central case of how to efficiently address a break in the global supply chain of medical equipment. Herein a comprehensive study of swab design considerations for mass production by stereolithography is presented. The retention and comfort performance of a range of novel designs of 3D-printed swabs are compared with the standard flocked-head swab used in clinical environments. Sample retention of the 3D swab is governed by the volume, porosity density, and void fraction of the head as well as by the pore geometry. 3D-printed swabs outperform conventional flock-head swabs in terms of sample retention. It is argued that mechanically functional designs of the swab head, such as corkscrew-shaped heads and negative Poisson ratio heads, maximize sample retention and improve patient comfort. In addition, available designs of swab shafts for an optimized sample collection procedure are characterized. The study is conducted in vitro, using artificial mucus, covering the full range of human mucus viscosities in a 3D-printed model of a nasal cavity. The work sets the path for the resilient supply of widespread sterile testing equipment as a rapid response to the current and future pandemics.

Biological activities of a recombinant fortilin from Fenneropenaeus merguiensis

Human Fortilin, an antiapoptotic protein, has also been implicated in several diseases; however, several potential uses of fortilin have also been proposed. Bearing the implications of fortilin in mind, fortilin analog, which has no complication with diseases, is required. Since a recombinant full-length fortilin from Fenneropenaeus merguiensis (rFm-Fortilin (FL)) reported only 44% (3e-27) homologous to human fortilin, therefore the biological activities of the Fm-Fortilin (FL) and its fragments (F2, F12, and F23) were investigated for potential use against HEMA toxicity from filling cement to pulp cell. The rFm-Fortilin FL, F2, 12, and F23 were expressed and assayed for proliferation activity. The rFm-Fortilin (FL) showed proliferation activity on human dental pulp cells (HDPCs) and protected the cells from 2-hydroxy-ethyl methacrylate (HEMA) at 1-20 ng/ml. In contrast, none of the rFm-Fortilin fragments promoted HDPC growth that may be due to a lack of three conserved amino acid residues together for binding with the surface of Rab GTPase for proliferative activity. In addition, rFm-Fortilin (FL) activated mineralization and trend to suppressed production of proinflammatory cytokines, including histamine (at 10 ng/ml) and TNF-α (at 100 ng/ml). Besides, the rFm-Fortilin (FL) did not mutate the Chinese hamster ovary (CHO) cell. Therefore, the rFm-Fortilin (FL) has the potential use as a supplementary medical material to promote cell proliferation in patients suffering severe tooth decay and other conditions.

Cytotoxicity of contemporary resin-based dental materials in contact with dentin

In this study, the cytotoxicity of different combinations of contemporary resin-based restoratives (adhesives, composites, luting agents) against human keratinocytes (HaCaT) was evaluated under two conditions, whether materials were applied to dentin or not. Adhesives (3-step etch-and-rinse/3ER: OptiBond FL; 2-step self-etch/2SE Clearfil SE Bond; Single Bond Universal/UNI), composites (conventional composite resin/CCR: Filtek Z350XT; flowable/FCR: Filtek Z350XT Flow; self-adhesive composite resin/SACR: Dyad Flow), and luting agents (conventional luting agent/CLA: Variolink-II; self-adhesive luting agent/SLA: RelyXU200) were combined according to their clinical use. Eluates from polymerized specimens applied to dentin were placed in contact with cells grown for 1 and 7 d. The controls were defined by cells without material contact. Cell viability was determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)] assay. C=C conversion was investigated using Fourier-transform infrared spectroscopy. After 1 d of incubation, when dentin was not present, 2SE yielded the highest cell viability, whereas 3ER, UNI, and SACR showed higher cell viability in the presence of dentin. After 7 d, when dentin was absent, 2SE and CLA achieved significantly higher cell viability. The presence of dentin resulted in a drastically higher cell viability for all materials, except 2SE and CLA. UNI had the lowest C=C conversion. The presence of dentin was a significant factor, which resulted in higher cell viability than what was seen for the material specimens per se. All materials resulted in a lower viability of HaCaT than what was seen under the no-material control conditions, with effects mainly limited to the first 24 h.

Molecular Response of Pulp Fibroblasts after Stimulation with Pulp Capping Materials

This in vitro study evaluated cell viability and metabolism, nitric oxide release and production of two chemokines and one cytokine by cultured human dental pulp fibroblasts (HDPF) in contact with two glass ionomer cements (Ketac Molar-KM and Vitrebond-VB), Single Bond (SB) and calcium hydroxide (Dycal-DY). Cultures of HDPF were established by means of an explant technique. The specimens were prepared under sterile conditions and in disks measuring 5 mm x 2 mm obtained from a prefabricated mold and placed on a permeable membrane to avoid direct contact with the cells. Cytotoxicity was assessed by Trypan Blue exclusion method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Nitric oxide release in cell supernatant was detected by the Griess Method whereas stromal derived factor-1 alpha (SDF-1α or CXCL12), chemokine (C-X-C motif) ligand 8 [Interleukin 8 (IL-8 or CXCL8)] and interleukin-6 (IL-6) were detected by ELISA. RT-qPCR was employed for gene expression analysis. Statistical analyses were performed by One-way ANOVA followed by Tukey's post hoc test for materials independent of the time, and Two-way ANOVA followed by Bonferroni correction test for the comparisons between materials and experimental time (p<0.05). Cytotoxic tests showed significant differences only for DY. Protein levels and mRNA expression were significantly increased for IL-8 for both periods of time. IL-6 production increased when fibroblasts were stimulated by KM. SDF-1α protein production and mRNA expression were not affected by any of the materials. There was a decrease in nitrate/nitrite levels only for KM. Although DY caused intense cell death and did not stimulate the production of the inflammatory mediators evaluated in this work, it is known that this event seems to be fundamental for the process of repair of the pulp tissue and formation of mineralized barrier. KM and VB increased production of proteins related to the inflammatory process, thus favoring tissue repair. Therefore, although these glass ionomer cements did not lead to large cell death, they should be used with caution.

Chemistry of novel and contemporary resin-based dental adhesives

The chemistry of resin-based dental adhesives is critical for its interaction with dental tissues and long-term bonding stability. Changes in dental adhesives composition influences the materials' key physical-chemical properties, such as rate and degree of conversion, water sorption, solubility, flexural strength and modulus, and cohesive strength and improves the biocompatibility to dental tissues. Maintaining a suitable reactivity between photoinitiators and monomers is important for optimal properties of adhesive systems, in order to enable adequate polymerisation and improved chemical, physical and biological properties. The aim of this article is to review the current state-of-the-art of dental adhesives, and their chemical composition and characteristics that influences the polymerisation reaction and subsequent materials properties and performance.

Biocompatibility Evaluation and Enhancement of Elastomeric Coatings Made Using Table-Top Optical 3D Printer

In this experimental report, the biocompatibility of elastomeric scaffold structures made via stereolithography employing table-top 3D printer Ember (Autodesk) and commercial resin FormLabs Flexible (FormLabs) was studied. The samples were manufactured using the standard printing and development protocol, which is known to inherit cytotoxicity due to remaining non-polymerized monomers, despite the polymerized material being fully biocompatible. Additional steps were taken to remedy this problem: the fabricated structures were soaked in isopropanol and methanol under different conditions (temperature and duration) to leach out the non-polymerized monomers. In addition, disc-shaped 3D-printed structures were UV exposed to assure maximum polymerization degree of the material. Post-processed structures were seeded with myogenic stem cells and the number of live cells was evaluated as an indicator for the material biocompatibility. The straightforward post-processing protocol enhanced the biocompatibility of the surfaces by seven times after seven days soaking in isopropanol and methanol and was comparable to control (glass and polystyrene) samples. This proposes the approach as a novel and simple method to be widely applicable for dramatic cytotoxicity reduction of optically 3D printed micro/nano-scaffolds for a wide range of biomedical studies and applications.

Cytotoxicity of Different Nano Composite Resins on Human Gingival and Periodontal Ligament Fibroblast Cell Lines: An In Vitro Study

The aim of this study is to determine the cytotoxicity of three different nano composite resins (CRs) on human gingival fibroblast (hGF) and periodontal ligament fibroblast (hPDLF) cell lines. These CRs selected were nanohybrid organic monomer-based Admira Fusion (AF), nanohybrid Bis-(acryloyloxymethyl) tricyclo [5.2.1.0.sup.2,6] decane-based Charisma Topaz (CT), and supra nano filled resin-based Estelite Quick Sigma (EQS). MTT assay was performed to assess the cytotoxicity of CRs at 24 h and one week. AF and EQS applied on hGF cells at 24 h and one week demonstrated similar cytotoxic outcomes. Cytotoxicity of CT on hGF cells at one week was higher than 24 h (p = 0.04). Cytotoxicity of CT on hGF cells was higher at 24 h (p = 0.002) and one week (p = 0.009) compared to control. All composites showed higher cytotoxicity on hPDLF cells at one week than the 24 h (AF; p = 0.02, CT; p = 0.02, EQS; p = 0.04). AF and EQS demonstrated lower cytotoxicity on hPDLF cells than the control group at 24 h (AF; p = 0.01, EQS; p = 0.001). CT was found more cytotoxic on hPDLF cells than the control (p = 0.01) and EQS group (p = 0.008) at one week. The cytotoxicity of CRs on hGF and hPDLF cells vary, according to the type of composites, cell types, and exposure time.

New Materials for 3D-Printing Based on Polycaprolactone with Gum Rosin and Beeswax as Additives

In this work, different materials for three-dimensional (3D)-printing were studied, which based on polycaprolactone with two natural additives, gum rosin, and beeswax. During the 3D-printing process, the bed and extrusion temperatures of each formulation were established. After, the obtained materials were characterized by mechanical, thermal, and structural properties. The results showed that the formulation with containing polycaprolactone with a mixture of gum rosin and beeswax as additive behaved better during the 3D-printing process. Moreover, the miscibility and compatibility between the additives and the matrix were concluded through the thermal assessment. The mechanical characterization established that the addition of the mixture of gum rosin and beeswax provides greater tensile strength than those additives separately, facilitating 3D-printing. In contrast, the addition of beeswax increased the ductility of the material, which makes the 3D-printing processing difficult. Despite the fact that both natural additives had a plasticizing effect, the formulations containing gum rosin showed greater elongation at break. Finally, Fourier-Transform Infrared Spectroscopy assessment deduced that polycaprolactone interacts with the functional groups of the additives.