Graphene Nanosheets to Improve Physico-Mechanical Properties of Bioactive Calcium Silicate Cements

The impact of print orientation and graphene nanoplatelets on biaxial flexural strength and cytotoxicity of a 3D printable resin for occlusal splints

OBJECTIVES

3D printing found its way into various medical applications and could be particularly beneficial for dentistry. Currently, materials for 3D printing of occlusal splints lack mechanical strength compared to polymethyl methacrylate (PMMA) used for standard milling of occlusal splints. It is known that print orientation and graphene nanoplatelets (GNP) can increase biaxial strength in a variety of materials. Thus, the aim of this study was to assess if adjustment of print orientation and addition of GNP improve biaxial strength and if they affect cytotoxicity of a 3D printable resin for occlusal splints.

METHODS

Specimens were printed vertically and horizontally with a stereolithography (SLA) printer and multilayered GNP powder was added to the resin at different concentrations. Printed specimens were characterized by Raman spectroscopy, optical profilometer analysis and scanning electron microscopy. Biaxial strength was evaluated by biaxial flexural testing. Cytotoxicity of specimens on L929 and gingival stromal cells (GSC) was assessed by the toxdent test, the resazurin-based toxicity assay and live-dead staining.

RESULTS

Horizontally printed specimens showed significantly higher biaxial strength and lower deformation. GNP did not improve biaxial strength and material deformation of 3D-printed resins. None of the specimens were cytotoxic to L929 cells or GSC.

SIGNIFICANCE

Print orientation in SLA printing has a significant impact on biaxial strength and material deformation. 3D printable materials can reach comparable or even improved biaxial strength compared to PMMA when using the optimal print orientation while GNP has no beneficial effects on the biaxial strength of resins for 3D printing of occlusal splints.

Enhancing the Physical, Antimicrobial, and Osteo/Odontogenic Properties of a Sol-Gel-Derived Tricalcium Silicate by Graphene Oxide for Vital Pulp Therapies

OBJECTIVES

This study developed a sol-gel tricalcium silicate/graphene oxide (TCS-GO) composite and examined its physicochemical properties, antimicrobial activity, and osteo/odontogenic effect on dental pulp stem cells.

METHODS

Tricalcium silicate was synthesized and combined with graphene oxide at three different concentrations, namely 0.02%, 0.04%, and 0.08% w/w, while tricalcium silicate and mineral trioxide aggregate served as controls. The setting time, compressive strength, pH, and calcium ion release of the composites were evaluated, as well as antimicrobial properties against Streptococcus mutans and Lactobacillus acidophilus. Additionally, the viability of dental pulp stem cells; apatite forming ability; and the gene expression of Alkaline phosphatase, Dentin sialophosphoprotein, and Runt-related transcription factor 2 were assessed.

RESULTS

TCS-GO (0.08%) showed a significantly shorter setting time and higher compressive strength when compared to MTA (p < 0.05). Additionally, tricalcium silicate and TCS-GO groups showed a higher release of Ca ions than MTA, with no significant difference in pH values among the different groups. TCS-GO (0.08%) also demonstrated a significantly stronger antimicrobial effect against Lactobacillus acidophilus compared to MTA (p < 0.05). ALP expression was higher in TCS-GO (0.08%) than MTA on days 3 and 7, while DSPP expression was higher in TCS-GO (0.08%) than MTA on day 3 but reversed on day 7. There was no significant difference in RUNX2 expression between TCS-GO (0.08%) and MTA on days 3 and 7.

CONCLUSIONS

The TCS-GO (0.08%) composite demonstrated superior physicochemical characteristics and antimicrobial properties compared to MTA. Moreover, the early upregulation of ALP and DSPP markers in TCS-GO (0.08%) indicates that it has the potential to promote and enhance the osteo/odontogenic differentiation of DPSCs.

Microhardness, Surface Roughness, and Wear Resistance Enhancement of Reinforced Conventional Glass Ionomer Cement Using Fluorinated Graphene Oxide Nanosheets

OBJECTIVES

 Conventional glass ionomer cements (GICs) have been considered the most prevalent restorative material however; the reduced mechanical qualities and decreased wear resistance have been the main challenges facing their wide clinical application. This study was designed to assess the mechanical properties of fluorinated graphene (FG) oxide-modified conventional GIC.

MATERIALS AND METHODS

 Composites of FG/GIC samples were prepared using (Medifil from PROMEDICA, Germany, shade A3) at different concentrations (0wt%) control group and (1wt%, 2wt% and 3wt% FG) groups using cylindrical molds (3mm × 6mm). FG was prepared using hydrothermal technique and characterized using XPERT-PRO Powder Diffractometer system for X-ray diffraction analysis and JEOL JEM-2100 high resolution transmission electron microscope. Vickers' hardness and wear resistance of GI samples were measured. Mechanical abrasion was performed via three-body tooth brushing wear test using ROBOTA chewing simulator coupled with a thermocycling protocol (Model ACH-09075DC-T, AD-Tech Technology Co., Ltd., Leinfelden-Echterdingen, Germany).

STATISTICAL ANALYSIS

 Comparisons between groups with respect to normally distributed numeric variables were performed using one-way analysis of variance test followed by posthoc test. While paired t-test was utilized for comparing data within the same group.

RESULTS

The surface roughness values of GICs (1wt% FG) and (2wt% FG) composites were significantly lower than those of the control and 3wt%FG groups. Vickers' hardness numbers were significantly higher in FG/GICs composites than in the control group (p≤0.05).

CONCLUSION

 GIC/FG combinations have sufficient strength to resist the occlusion stresses with improved hardness as compared with conventional GIC. GIC/FG appeared to be a promising restorative material.

Graphene as a promising material in orthodontics: A review

Graphene is an extraordinary material with unique mechanical, chemical, and thermal properties. Additionally, it boasts high surface area and antimicrobial properties, making it an attractive option for researchers exploring innovative materials for biomedical applications. Although there have been various studies on graphene applications in different biomedical fields, limited reviews have been conducted on its use in dentistry, and no reviews have focused on its application in the orthodontic field. This review aims to present a comprehensive overview of graphene-based materials, with an emphasis on their antibacterial mechanisms and the factors that influence these properties. Additionally, the review summarizes the dental applications of graphene, spotlighting the studies of its orthodontic application as they can be used to enhance the antibacterial and mechanical properties of orthodontic materials such as adhesives, archwires, and splints. Also, they can be utilized to enhance bone remodeling during orthodontic tooth movement. An electronic search was carried out in Scopus, PubMed, Science Direct, and Wiley Online Library digital database platforms using graphene and orthodontics as keywords. The search was restricted to English language publications without a time limit. This review highlights the need for further laboratory and clinical research using graphene-based materials to improve the properties of orthodontic materials to make them available for clinical use.

Applications of graphene oxide and reduced graphene oxide in advanced dental materials and therapies

The graphene family of nanomaterials acquired significant attention in the field of dentistry due to a range of interesting properties. Graphene oxide (GO) and reduced graphene oxide (rGO) are the major graphene derivatives that are widely used in dental applications. These derivatives exhibit excellent mechanical properties, superior biocompatibility, good antibacterial properties, extreme chemical stability, and favorable tribological characteristics, thus representing highly materials for dentistry. The amphiphilic nature of GO allows covalent and noncovalent modifications that are favorable for biomedical applications. Graphene can influence the differentiation of dental pulp stem cells (DPSCs) and enhance the properties of other biomaterials. Here, we review the dental applications of GO or rGO with regards to antimicrobial activity, therapeutic drug delivery, restorative dentistry, implants, pulp regeneration, bone regeneration, periodontal tissue regeneration, biosensors, and tooth whitening.

Analysis of the cytotoxicity and bioactivity of CeraSeal, BioRoot™ and AH Plus® sealers in pre-osteoblast lineage cells

BACKGROUND

The objective of the present study was to evaluate in vitro the cytotoxicity and bioactivity of various endodontic sealers (CeraSeal, BioRoot™ and AH Plus®) in pre-osteoblast mouse cells (MC3T3 cells).

METHODS

MC3T3 cells (ATCC CRL-2594) were plated in 1 × 104 cells/well in 96-well plates in contact with endodontic sealers at concentrations of 1:10 and 1:100. Cell viability was evaluated by MTT assay after 24 and 48 h. In addition, sealer bioactivity was measured by RT-PCR for mediator of inflammation (Tnf, Ptgs2) and mineralization (Runx2, Msx1, Ssp1 and Dmp1) after 24 h and by Alizarin Red S Assay of mineralization after 28 days. Data were analyzed using one-way ANOVA followed by the Tukey's post-test at a significance level of 5%.

RESULTS

BioRoot™ presented 24-hour cytotoxicity (p < 0.05) at 1:10 concentration. In the period of 48 h, no endodontic cement was cytotoxic to the cells compared to the control (p > 0.05). TNF-α gene expression was induced by AH Plus® (p < 0.05), while Ptgs2 was induced by the CeraSeal and BioRoot™ (p < 0.05). The expression of Runx2 was stimulated by BioRoot™ and AH Plus® (p < 0.05). In contrast, the expression of Dmp-1 Dmp1 was higher for the CeraSeal and BioRoot™ (p < 0.05). Nonetheless, the sealers did not impact the formation of mineralization nodules (p > 0.05).

CONCLUSION

CeraSeal, BioRoot™ and AH Plus® sealers were not cytotoxic to MC3T3 cells within 48 h, but differentially induced the expression of genes related to inflammation and mineralization without impacting biomineralization by the cells.

Specimen Shape and Elution Time Affect the Mineralization and Differentiation Potential of Dental Pulp Stem Cells to Biodentine

The liquid extract method is commonly used to evaluate the cytotoxicity and bioactivity of materials. Although ISO has recommended guidelines for test methods, variations in elution period, and shape of samples can influence the biological outcomes. The aim of this study was to investigate the influence of material form and elution period of Biodentine on dental pulp stem cells (DPSCs)' proliferation and mineralization. Biodentine (0.2 g) discs or powder were immersed in culture media (10 mL) for 1, 3 or 7 days (D1, D3 and D7). The eluents were filtered and used to treat DPSC. The calcium release profile and pH were determined. Cell proliferation was evaluated by MTS for 3 days, and mineralization and differentiation were assessed by alizarin red S staining (Ca2+/ng of DNA) and qRT-PCR (MEPE, DSPP, DMP-1, RUNX2, COL-I and OCN) for 14 days. Statistical analysis was performed with a one or two-way ANOVA and post hoc Tukey's test (pH, calcium release and proliferation) or Mann-Whitney test (α = 0.05). pH and calcium ion release of powdered eluents were significantly higher than disc eluents. Powdered eluent promoted extensive cell death, while the disc form was cytocompatible. All disc eluents significantly increased the gene expression and mineralization after 14 days compared to the untreated control. D7 induced less mineralization and differentiation compared to D1 and D3. Thus, the materials' form and elution time are critical aspects to be considered when evaluating the bioactivity of materials, since this binomial can affect positively and negatively the biological outcomes.

Nanoparticles and Their Antibacterial Application in Endodontics

Root canal treatment represents a significant challenge as current cleaning and disinfection methodologies fail to remove persistent bacterial biofilms within the intricate anatomical structures. Recently, the field of nanotechnology has emerged as a promising frontier with numerous biomedical applications. Among the most notable contributions of nanotechnology are nanoparticles, which possess antimicrobial, antifungal, and antiviral properties. Nanoparticles cause the destructuring of bacterial walls, increasing the permeability of the cell membrane, stimulating the generation of reactive oxygen species, and interrupting the replication of deoxyribonucleic acid through the controlled release of ions. Thus, they could revolutionize endodontics, obtaining superior results and guaranteeing a promising short- and long-term prognosis. Therefore, chitosan, silver, graphene, poly(lactic) co-glycolic acid, bioactive glass, mesoporous calcium silicate, hydroxyapatite, zirconia, glucose oxidase magnetic, copper, and zinc oxide nanoparticles in endodontic therapy have been investigated in the present review. The diversified antimicrobial mechanisms of action, the numerous applications, and the high degree of clinical safety could encourage the scientific community to adopt nanoparticles as potential drugs for the treatment of endodontic diseases, overcoming the limitations related to antibiotic resistance and eradication of the biofilm.

Effect of incorporation of nano-graphene oxide on physicochemical, mechanical, and biological properties of tricalcium silicate cement

OBJECTIVE

Evaluation of setting time, compressive strength, pH, calcium ion release, and antibacterial activity of mineral trioxide aggregate (MTA) after modification with three different concentrations of nano-graphene oxide (GO) powder compared to unmodified Biodentine as a commercial control.

METHODS

GO powder, unhydrated and hydrated cements were characterized using Environmental Scanning Electron Microscope (ESEM) with Energy Dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman Spectroscopy, and Fourier Transform Infrared spectroscopy (FTIR). GO was also analyzed using Scanning Transmission Electron Microscope (STEM) to determine average lateral dimensions. Specimens were prepared and grouped according to the concentration of GO added to Rootdent MTA (control, 1, 3, and 5 wt%) and the material used (MTA and unmodified Biodentine) into five groups. Setting time was evaluated using Gillmore penetrometer (n = 5). Compressive strength was evaluated using universal testing machine (n = 7). pH and calcium ion release were assessed using pH meter and Induced Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) at 1, 7, 14, and 28 days (n = 7). Antibacterial activity was evaluated against Streptococcus mutans using direct contact test (n = 7). One-way and repeated measures ANOVA followed by Tukey's post hoc test were used for data analysis with significance level set at p ≤ 0.05.

RESULTS

Addition of GO to MTA reduced both initial and final setting time. GO modified MTA groups and unmodified Biodentine showed significantly increased calcium ion release at 14 and 28 days. All cements showed alkaline pH of the storage media at all tested time intervals. 1 wt% GO recorded the highest compressive strength values in MTA modified groups. The increased concentration of GO from 1 to 5 wt% successively increased antibacterial activity of MTA, with Biodentine showing the lowest significant value.

CONCLUSION

Addition of 1 wt% GO can significantly improve the tested properties of tricalcium silicate-based cements without compromising their compressive strength.

CLINICAL SIGNIFICANCE

GO is a promising modification for tricalcium silicate cements to improve setting time, compressive strength, and antibacterial activity to provide a variety of materials for different clinical situations. This in turn can reduce the risk of reinfection and allow placement of the final restoration in a single visit.

Can Graphene Pave the Way to Successful Periodontal and Dental Prosthetic Treatments? A Narrative Review

Graphene, as a promising material, holds the potential to significantly enhance the field of dental practices. Incorporating graphene into dental materials imparts enhanced strength and durability, while graphene-based nanocomposites offer the prospect of innovative solutions such as antimicrobial dental implants or scaffolds. Ongoing research into graphene-based dental adhesives and composites also suggests their capacity to improve the quality and reliability of dental restorations. This narrative review aims to provide an up-to-date overview of the application of graphene derivatives in the dental domain, with a particular focus on their application in prosthodontics and periodontics. It is important to acknowledge that further research and development are imperative to fully explore the potential of graphene and ensure its safe use in dental practices.

Reinforcement of resin-modified glass-ionomer cement with glass fiber and graphene oxide

OBJECTIVE

To evaluate the effect of adding glass fiber and graphene oxide to a resin-modified glass ionomer cement (RMGIC).

METHODS

Experimental RMGICs were prepared by adding separately and simultaneously glass fibers (5, 10, and 20 wt%) and graphene oxide (1, 3, and 5 wt%) to the powder of RMGIC with different ratios. The samples were examined under SEM and XRD. The surface roughness, flexural strength, Vickers microhardness, water sorption, and solubility were investigated. Data were analyzed using ANOVA and Tukey tests (p = 0.05).

RESULTS

Adding fiber and graphene oxide to RMCIS increased the surface roughness, flexural strength, and microhardness. The highest surface roughness value was obtained in the 20% fiber+5% graphene oxide adding group and the lowest in the control group (p < 0.05). The highest microhardness and flexural strength values were acquired in the 20% fiber-adding group and the lowest in the control group (p < 0.05). 10% and 20% fiber addition increased water sorption and solubility (p < 0.05). Adding 3%, 5% graphene oxide, and 20% fiber+5% graphene oxide reduced water sorption (p < 0.05). The highest water sorption was found in the 20% fiber-adding group and the lowest in the 5% graphene oxide and %20 fiber+5% graphene oxide-adding groups (p < 0.05). Graphene oxide alone and together with fiber did not affect the solubility (p > 0.05).

CONCLUSION

The results show that reinforcement of RMGIC with glass fiber and graphene oxide may improve the mechanical properties. But the glass fibers may cause more water sorption and solubility. Graphene oxide may decrease water sorption of RMGIC and fiber-reinforced RMGIC.

Graphene on dentistry: A bibliometric and scientometric analysis

Background

Today, the development of dental materials is a very important issue. Graphene has been used in dentistry to strengthen many materials.

Aim

The aim of this study was to analyze leading countries and to identify the preferred journals, the most commonly used keywords, and the most productive authors in the field of graphene.

Materials and Methods

The search keyword was "graphene" on the Web of Science database; the search was restricted to before 2022. The selected search from the Web of Science database included the title of articles, authors, year of publication, country, citation count, and keywords. An analysis was performed regarding citations and documents, authors, journals, and keywords using a bibliometric software program. All articles were evaluated and subjected to scientometric analysis.

Results

Twenty six articles were included in the study. There has been a remarkable increase in published articles from past to present, and a regular increase is observed in the number of citations. Dental Materials has highest number of publications among the articles included in the present study. Dr. Rosa, who had the highest number of citations, is also the most effective author. Graphene has many studies in dentistry with different materials. As per the data obtained, graphene, graphene oxide, and peri-implantitis are the most used keywords and Singapore and China are at the forefront of the countries where the articles are published.

Conclusion

This bibliometric analysis reveals the progress and trend of research on graphene in dentistry and extensive collaborations between authors, countries, and institutions. The findings of this study can help inspire researchers to plan new studies and collaborate on graphene.

Effect of Fluorographene Addition on Mechanical and Adhesive Properties of a New Core Build-Up Composite

This study aims to develop a restorative material having such mechanical and adhesive properties that it can be used both as a reconstruction material and as a luting cement. The experimental core build-up composite (CBC) was derived from a self-adhesive cement by the modification of its chemical formula, requiring the use of dedicated dentin and ceramic primers. The adhesive properties to zirconia and dentin were analyzed with a micro-Shear Bond Strength test (mSBS). The mechanical properties were analyzed by a flexural strength test. The results were compared with those obtained for other commercially available cements and core build-up materials, both before and after addition of 2 wt.% fluorographene. The CBC obtained average values in the mSBS of 49.7 ± 4.74 MPa for zirconia and 32.2 ± 4.9 MPa for dentin, as well as values of 110.9 ± 9.3 MPa for flexural strength and 6170.8 ± 703.2 MPa for Young's modulus. The addition of fluorographene, while increasing the Young's modulus of the core build-up composite by 10%, did not improve the adhesive capabilities of the primers and cement on either zirconia or dentin. The CBC showed adhesive and mechanical properties adequate both for a restoration material and a luting cement. The addition of 2 wt.% fluorographene was shown to interfere with the polymerization reaction of the material, suggesting the need for further studies.

Research on Graphene and Its Derivatives in Oral Disease Treatment

Oral diseases present a global public health problem that imposes heavy financial burdens on individuals and health-care systems. Most oral health conditions can be treated in their early stage. Even if the early symptoms of oral diseases do not seem to cause significant discomfort, prompt treatment is essential for preventing their progression. Biomaterials with superior properties enable dental therapies with applications in restoration, therapeutic drug/protein delivery, and tissue regeneration. Graphene nanomaterials have many unique mechanical and physiochemical properties and can respond to the complex oral microenvironment, which includes oral microbiota colonization and high masticatory force. Research on graphene nanomaterials in dentistry, especially in caries, periodontitis therapy, and implant coatings, is progressing rapidly. Here, we review the development of graphene and its derivatives for dental disease therapy.

Graphene-Based Nanomaterials for Dental Applications: Principles, Current Advances, and Future Outlook

With the development of nanotechnology, nanomaterials have been used in dental fields over the past years. Among them, graphene and its derivatives have attracted great attentions, owing to their excellent physicochemical property, morphology, biocompatibility, multi-differentiation activity, and antimicrobial activity. In our review, we summarized the recent progress about their applications on the dentistry. The synthesis methods, structures, and properties of graphene-based materials are discussed. Then, the dental applications of graphene-based materials are emphatically collected and described. Finally, the challenges and outlooks of graphene-based nanomaterials on the dental applications are discussed in this paper, aiming at inspiring more excellent studies.

Hardening and Fresh State Behaviour of Ternary Cement for Marine Environments: Modification through Nanoadditives

The use of nanomaterials to enhance the physical and mechanical properties and durability of cement materials in their hardened state has been studied for a long time in many investigations. In comparison, fewer studies focus on nanomaterials’ influence on the fresh state when the cement reaction starts. In addition, if we consider ternary blended cement (as those used for applications in marine environments), this has been rarely studied. Severe stresses in the marine environment require high durability, which is achieved by using pozzolanic additions, to the detriment of a rapid achievement of the properties. The addition of nanomaterials could contribute to increasing the durability and also accelerating the setting of the concrete. In this work, we performed a systematic and comparative study on the influence of adding graphene oxide (GO), nanosilica (NS), and microfibrillated cellulose (MFC) during the setting mechanisms of cement (CEM V/A suitable for concrete subjected to external attacks in marine environments) blended with fly ash and slag. Cement hardening was examined through setting time and rheology within mini-slump tests. The effect of nanoadditives on the cement hydration was analysed by heat flow calorimetry to evaluate the acceleration potential. Exploring the three nanoadditives on the same formulation, we could establish that the retention of mixing water significantly decreased workability for MFC. In contrast, NS increases the hydration of cement particles, acting as nucleation nodes and promoting supplementary cement hydrates (pozzolanic reactions) and accelerating setting time. Finally, GO showed a reduction in workability. We also investigated the dosage effects on mechanical behaviour at an early age and discovered an improvement even at low GO (0.006%) and NS (3%) dosages. We have also analysed the dosage effects on mechanical behaviour at an early age.

Nanomaterials Application in Endodontics

In recent years, nanomaterials have become increasingly present in medicine, especially in dentistry. Their characteristics are proving to be very useful in clinical cases. Due to the intense research in the field of biomaterials and nanotechnology, the efficacy and possibilities of dental procedures have immensely expanded over the years. The nano size of materials allows them to exhibit properties not present in their larger-in-scale counterparts. The medical procedures in endodontics are time-consuming and mostly require several visits to be able to achieve the proper result. In this field of dentistry, there are still major issues about the removal of the mostly bacterial infection from the dental root canals. It has been confirmed that nanoparticles are much more efficient than traditional materials and appear to have superior properties when it comes to surface chemistry and bonding. Their unique antibacterial properties are also promising features in every medical procedure, especially in endodontics. High versatility of use of nanomaterials makes them a powerful tool in dental clinics, in a plethora of endodontic procedures, including pulp regeneration, drug delivery, root repair, disinfection, obturation and canal filling. This study focuses on summing up the current knowledge about the utility of nanomaterials in endodontics, their characteristics, advantages, disadvantages, and provides a number of reasons why research in this field should be continued.

The effect of adding graphene oxide nanoplatelets to Portland cement: Potential for dental applications

Background:

The potential of graphene-based materials to improve the physiomechanical properties of Portland cement-based materials without compromising biocompatibility is of interest to dental researchers and remains to be discovered.

Aim:

This study investigated the effects of adding graphene oxide nanoplatelets (GONPs) on the surface microhardness and biocompatibility of Portland cement.

Materials and Methods:

Three prototype Portland cement powder formulations were prepared by adding 0, 1, and 3 wt % GONPs in powder form to Portland cement. Prototype cement specimens were in the form of disks, with a diameter of 10 mm and a thickness of 2 mm. In experiment 1, surface microhardness was measured using the through indenter viewing hardness tester, 20 surface hardness values were obtained from all specimens. In experiment 2, Balb/C 3T3 fibroblasts were cultured with the material disks and the viability of cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Statistical Analysis:

The data were analyzed using the analysis of variance followed by Dunnett test (α = 0.05) or Tukey test (α = 0.05).

Results:

In response to material disks, the addition of 1 wt % GONPs had a proliferative effect on cells at day 3 and day 7 with a significant difference from the control. The addition of 3 wt % GONPs showed a remarkable increase in surface microhardness; however, it exhibited initial cytotoxicity.

Conclusions:

The addition of 1 wt % GONPs to Portland cement improved surface microhardness without compromising biocompatibility; therefore, it has a greater potential for dental applications. The results of this work give other researchers leads in future assessments of this prototype material.

Nanomaterials in Dentistry: State of the Art and Future Challenges

Nanomaterials are commonly considered as those materials in which the shape and molecular composition at a nanometer scale can be controlled. Subsequently, they present extraordinary properties that are being useful for the development of new and improved applications in many fields, including medicine. In dentistry, several research efforts are being conducted, especially during the last decade, for the improvement of the properties of materials used in dentistry. The objective of the present article is to offer the audience a complete and comprehensive review of the main applications that have been developed in dentistry, by the use of these materials, during the last two decades. It was shown how these materials are improving the treatments in mainly all the important areas of dentistry, such as endodontics, periodontics, implants, tissue engineering and restorative dentistry. The scope of the present review is, subsequently, to revise the main applications regarding nano-shaped materials in dentistry, including nanorods, nanofibers, nanotubes, nanospheres/nanoparticles, and zeolites and other orders porous materials. The results of the bibliographic analysis show that the most explored nanomaterials in dentistry are graphene and carbon nanotubes, and their derivatives. A detailed analysis and a comparative study of their applications show that, although they are quite similar, graphene-based materials seem to be more promising for most of the applications of interest in dentistry. The bibliographic study also demonstrated the potential of zeolite-based materials, although the low number of studies on their applications shows that they have not been totally explored, as well as other porous nanomaterials that have found important applications in medicine, such as metal organic frameworks, have not been explored. Subsequently, it is expected that the research effort will concentrate on graphene and zeolite-based materials in the coming years. Thus, the present review paper presents a detailed bibliographic study, with more than 200 references, in order to briefly describe the main achievements that have been described in dentistry using nanomaterials, compare and analyze them in a critical way, with the aim of predicting the future challenges.

Comparison Study on the Adsorption Behavior of Chemically Functionalized Graphene Oxide and Graphene Oxide on Cement

Chemical functionalization of graphene oxide (GO) is one kind of advanced strategy to eliminate the negative effects on the flowability of cement with GO. The adsorption behavior of admixture on cement plays a vital role in the flowability of cement-based materials. Herein, the comparison study on the adsorption behavior (including adsorption amount, adsorption kinetics, adsorption isotherms and adsorption layer thickness) of three kinds of chemically functionalized graphene oxides (CFGOs) with different polyether amine branched-chain lengths and GO on cement is reported. The results of CFGOs and GO adsorption data on cement particles were all best fitted with the pseudo-second-order kinetic model, and also conformed to the Freundlich isothermal model, indicating that the adsorption of CFGOs and GO on cement both were multilayer type and took place in a heterogeneous manner. The adsorption of CFGOs and GO on cement was not just physical adsorption, but also engaged chemical adsorption. In contrast to GO, the adsorption behavior of CFGOs on cement represented a lesser adsorption amount, weaker adsorption capacity and thinner adsorption layer thickness. Moreover, the longer the branched-chain length of CFGOs, the greater the decreasing degrees of adsorption amount, adsorption capacity and adsorption layer thickness. Due to the consumption of the carboxyl group (-COOH) by chemical functionalization, the anchoring effect of CFGOs was weaker than GO, and the steric hindrance effect generated from branched-chains which weakened the van der Waals forces among CFGOs layers. Moreover, the steric hindrance effect strengthened with the increasing branched-chain length, thus preventing the cement particles from aggregation, which resulted in satisfactory flowability of CFGOs with incorporation of cement rather than GO.

Biological Effects of New Hydraulic Materials on Human Periodontal Ligament Stem Cells

Background: The aim of this study was: to evaluate the biological properties of new hydraulic materials: Bio-C Repair and Bio-C Sealer. Methods: Periodontal ligament stem cells were exposed to several dilutions of Bio-C Repair and Bio-C Sealer. The ion release profile and pH were determined. Metabolic activity, cell migration and cell survival were assessed using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), wound-healing assays and Annexin assays, respectively. Cells were cultured in direct contact with the surface of each material. These were then analyzed via scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Statistical differences were assessed using a two-way ANOVA (α < 0.05). Results: Similar pH was observed in these cements. Bio-C Sealer released significantly more Ca and Si ions (p < 0.05) in comparison with Bio-C Repair. Undiluted Bio-C Sealer induced a significant reduction on cellular viability, cell survival and cell migration when compared to the control (p < 0.05). Moreover, SEM showed abundant cells adhered on Bio-C Repair and a moderate number of cells attached on Bio-C Sealer. Finally, EDX analysis identified higher percentages of Ca and O in the case of Bio-C repair than with Bio-C sealer, while other elements such as Zr and Si were more abundant in Bio-C sealer. Conclusions: Bio-C Repair displayed higher cell viability, cell adhesion and migration rates than Bio-C Sealer.

Artifact expression of polylactic acid/hydroxyapatite/graphene oxide nanocomposite in CBCT: a promising dental material

OBJECTIVE

To evaluate the artifact expression of a new material-polylactic acid (PLA)/hydroxyapatite (HA)/graphene oxide (GO) nanocomposite-and compare it with that of commonly used dental materials, using cone-beam computed tomography.

MATERIALS AND METHODS

Cylinders of amalgam alloy, metal alloy, titanium, gutta-percha, and PLA/HA/GO were individually placed in the center of an acrylic phantom. Three images of each phantom + cylinder set were acquired using a Picasso Trio unit (Vatech, Hwaseong, South Korea) set at 90 kVp, 3.7 mA, 0.2 mm³ voxel size, and 12 × 8.5 cm FOV. Three images of a control group (sound phantom) were also obtained. Eight ROIs were established in each image to evaluate the standard deviation (S.D.) of gray values in the ImageJ Software. The Kruskal-Wallis test with the Student-Newman-Keuls post hoc was employed, considering a significance level of 5%.

RESULTS

There were no significant differences in S.D. between the control and PLA/HA/GO images (p = 0.712). Both control and PLA/HA/GO showed fewer image artifacts than the other materials (p < 0.05). The images of the amalgam alloy did not differ from the metal alloy images (p = 0.691), showing more artifacts than the gutta-percha (p = 0.028) and titanium (p = 0.051).

CONCLUSIONS

The PLA/HA/GO produced fewer artifacts and a better-quality image than the other tested materials.

CLINICAL RELEVANCE

The PLA/HA/GO has physical and biological properties similar to those of dental materials. Since it has produced fewer image artifacts, this new nanocomposite may be employed in the near future, enhancing the diagnosis in CBCT.

A novel, doped calcium silicate bioceramic synthesized by sol-gel method: Investigation of setting time and biological properties

The aim of the current study was to synthesize a fast-setting ion-doped calcium silicate bioceramic by the sol-gel method and to characterize its in vitro apatite-forming ability and cell viability. Calcium silicate (CS), doped calcium silicate with zinc and magnesium, with Ca/Zn molar ratios of 6.7:1 (DCS1), and 4.5:1 (DCS2), were synthesized by the sol-gel method. Matreva white MTA (WMTA, Matreva, CA, Egypt) was used as a control. The synthesized powders were characterized by x-ray diffraction. Setting time was measured using the Gilmore needle indentation technique. The in vitro apatite-forming ability of the materials was evaluated by scanning electron microscope and energy dispersive X-ray. NIH3T3-E1 cells viability was tested using MTT assay. The ion release of Ca, Si, Zn, and Mg was measured using inductive coupled plasma-optical emission spectroscopy (ICP-OES). One-way ANOVA was used to analyze setting time results. The Tukey's HSD post hoc test was used to establish significance (p < 0.001). For nonparametric data, the Kruskal-Wallis H test with Dunn's correction for post hoc comparison was used (p < 0.05). CS, DCS1, and DCS2 showed a significant decrease in setting time 33 ± 1.63 min, 28 ± 1.63 min, and 41.75 ± 2.87 min, respectively, compared to WMTA 91 ± 3.16 min (p < 0.001). DCS1 showed the highest apatite-forming ability and cell viability compared to the other groups. Ca and Si ions release decreased in both DCS1 and DCS2. The physical and biological properties of CS can be successfully improved by the sol-gel synthesis and ions doping. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:56-66, 2020.

Biological effects of acid-eroded MTA Repair HP and ProRoot MTA on human periodontal ligament stem cells

OBJECTIVE

The aim of this study was to analyze the biological effects of MTA Repair HP and ProRoot MTA on human periodontal ligament stem cells (hPDLSCs) after exposure to acidic and neutral environments.

MATERIALS AND METHODS

Discs of each material (n = 30) were exposed to phosphate buffered saline (pH = 7.4) or butyric acid (pH = 5.2) for 7 days, and biological testing was carried out in vitro on hPDLSCs. Cell viability and apoptosis assays were performed using eluates of each root-end filling material. To evaluate cell attachment to the different materials, hPDLSCs were directly seeded onto the material surfaces and analyzed by scanning electron microscopy. The chemical composition of the root-end filling materials was determined by energy-dispersive x-ray and eluates were analyzed by inductively coupled plasma-mass spectrometry. Statistical differences were assessed by ANOVA and Tukey test (p < 0.05).

RESULTS

Under an acidic environment, both materials displayed similar ion release abilities, with the increased release of Si and Ca ions. Substantial changes in microstructure were observed for both materials after exposure to acidic pH. In addition, material exposure to an acidic environment showed a similar degree of cell adherence, and, surprisingly, MTA Repair HP exhibited higher cell viability rates at pH 5.2 than ProRoot MTA.

CONCLUSIONS

Exposure to an acidic environment promoted Si and Ca ion release from ProRoot MTA and MTA Repair HP. Moreover, we observed optimal biological properties of ProRoot MTA and MTA Repair HP in terms of cell viability, cell death, and cell attachment in both environments.

CLINICAL RELEVANCE

These results may suggest that MTA Repair HP and ProRoot exhibited optimal biological properties in terms of cell viability, cell death and cell attachment in acidic environment, being considered as materials for root-end filling and perforations.

Effects of dodecacalcium hepta-aluminate content on the setting time, compressive strength, alkalinity, and cytocompatibility of tricalcium silicate cement

Objective

This study aimed to investigate the effects of dodecacalcium hepta-aluminate (C12A7) content on some physicochemical properties and cytocompatibility of tricalcium silicate (C3S) cement using human dental pulp cells (hDPCs).

Material and Methods

High purity C3S cement was manufactured by a solid phase method. C12A7 was mixed with the cement in proportions of 0, 5, 8, and 10 wt% (C12A7-0, −5, −8, and −10, respectively). Physicochemical properties including initial setting time, compressive strength, and alkalinity were evaluated. Cytocompatibility was assessed with cell viability tests and cell number counts. Statistical analysis was performed by using one-way analysis of variance (ANOVA) and Tukey's test (p<0.05).

Results

The initial setting time of C3S-based cement was shorter in the presence of C12A7 (p<0.05). After 1 day, C12A7-5 showed significantly higher compressive strength than the other groups (p<0.05). After 7 days, the compressive strength of C12A7-5 was similar to that of C12A7-0, whereas other groups showed strength lower than C12A7-0. The pH values of all tested groups showed no significant differences after 1 day (p>0.05). The C12A7-5 group showed similar cell viability to the C12A7-0 group (p>0.05), while the other experimental groups showed lower values compared to C12A7-0 group (p<0.05). The number of cells grown on the C12A7-5 specimen was higher than that on C12A7-8 and −10 (p<0.05).

Conclusions

The addition of C12A7 to C3S cement at a proportion of 5% resulted in rapid initial setting time and higher compressive strength with no adverse effects on cytocompatibility.

Graphene Family Nanomaterials: Properties and Potential Applications in Dentistry

Graphene family nanomaterials, with superior mechanical, chemical, and biological properties, have grabbed appreciable attention on the path of researches seeking new materials for future biomedical applications. Although potential applications of graphene had been highly reviewed in other fields of medicine, especially for their antibacterial properties and tissue regenerative capacities, in vivo and in vitro studies related to dentistry are very limited. Therefore, based on current knowledge and latest progress, this article aimed to present the recent achievements and provide a comprehensive literature review on potential applications of graphene that could be translated into clinical reality in dentistry.

Improvement of the mechanical, tribological and antibacterial properties of glass ionomer cements by fluorinated graphene

OBJECTIVE

The aim of this study was to improve the mechanical properties, wear resistance and antibacterial properties of conventional glass ionomer cements (GICs) by fluorinated graphene (FG), under the premise of not influencing their solubility and fluoride ion releasing property.

MATERIALS AND METHODS

FG with bright white color was prepared using graphene oxide by a hydrothermal reaction. Experimental modified GICs was prepared by adding FG to the traditional GICs powder with four different weight ratios (0.5wt%, 1wt%, 2wt% and 4wt%) using mechanical blending. Compressive and flexural strength of each experimental and control group materials were investigated using a universal testing machine. The Vickers microhardness of all the specimens was measured by a Vicker microhardness tester. For tribological properties of the composites, specimens of each group were investigated by high-speed reciprocating friction tester. Fluoride ion releasing was measured by fluoride ion selective electrode methods. The antibacterial effect of GICs/FG composites on selected bacteria (Staphylococci aureus and Streptococcus mutans) was tested with pellicle sticking method.

RESULTS

The prepared GICs/FG composites with white color were successfully fabricated. Increase of Vickers microhardness and compressive strength and decrease of friction coefficient of the GICs/FG composites were achieved compared to unreinforced materials. The colony count against S. aureus and S. mutans decreased with the increase of the content of FG. And the antibacterial rate of S. mutans can be up to 85.27% when the FG content was 4wt%. Additionally, fluoride ion releasing property and solubility did not show significant differences between unreinforced and FG reinforced GICs.

SIGNIFICANCE

Adding FG to traditional GICs could not only improve mechanical and tribological properties of the composites, but also improve their antibacterial properties. In addition, the GICs/FG composites had no negative effect on the color, solubility and fluoride ion releasing properties, which will open up new roads for the application of dental materials.

Fabrication of GO/Cement Composites by Incorporation of Few-Layered GO Nanosheets and Characterization of Their Crystal/Chemical Structure and Properties

Original graphene oxide (GO) nanosheets were prepared using the Hummers method and found to easily aggregate in aqueous and cement composites. Using carboxymethyl chitosan (CCS) as a dispersant, few-layered GO nanosheets (1-2 layers) were obtained by forming CCS/GO intercalation composites. The testing results indicated that the few-layered GO nanosheets could uniformly spread, both in aqueous and cement composites. The cement composites were prepared with GO dosages of 0.03%, 0.05% and 0.07% and we found that they had a compact microstructure in the whole volume. A special feature was determined, namely that the microstructures consisted of regular-shaped crystals created by self-crosslinking. The X-ray diffraction (XRD) results indicated that there was a higher number of cement hydration crystals in GO/cement composites. Meanwhile, we also found that partially-amorphous Calcium-Silicate-Hydrate (C-S-H) gel turned into monoclinic crystals. At 28 days, the GO/cement composites reached the maximum compressive and flexural strengths at a 0.05% dosage. These strengths were 176.64 and 31.67 MPa and, compared with control samples, their increased ratios were 64.87% and 149.73%, respectively. Durability parameters, such as penetration, freeze-thaw, carbonation, drying-shrinkage value and pore structure, showed marked improvement. The results indicated that it is possible to obtain cement composites with a compact microstructure and with high performances by introducing CCS/GO intercalation composites.