Antibacterial glass-ionomer cement restorative materials: A critical review on the current status of extended release formulations

Organic antibacterial modifications of high-viscosity glass ionomer cement for atraumatic restorative treatment: A review

High viscosity glass ionomer cement (HVGIC) has been employed as a restorative material for Atraumatic Restorative Treatment (ART). As residual caries persist after caries removal in ART, the antibacterial activity of HVGIC gains importance. Organic and inorganic substances with antibacterial properties have been incorporated into HVGIC over the years, and their effects on the antibacterial and physical properties have been studied. The objective of this paper is to review the various alterations made to HVGIC using organic compounds, their effect on the antibacterial activity, and the physical properties of the cement. Various in vitro investigations have been conducted by adding antiseptics, antibiotics, and naturally occurring antibacterial substances. Most of these compounds render superior antibacterial properties to HVGIC, but higher concentrations affect physical properties in a dose-dependent manner. However, some naturally occurring antibacterial substances, such as chitosan, improve the physical properties of HVGIC, as they enhance cross-linking and polysalt bridging. There is potential for clinical benefits to be gained from the addition of organic antibacterial compounds to HVGIC. In-depth research is required to determine the optimum concentration at which the antibacterial effect is maximum without affecting the physical properties of the cement.

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.

Improving the Mechanical Properties of Glass Ionomer Cement With Nanocrystalline Cellulose From Rice Husk

This study aimed to evaluate the effect of incorporating nanocrystalline cellulose (NCC) sourced from rice husk on the mechanical properties of a commercial glass ionomer cement (GIC). NCC was isolated through acid hydrolysis, and its crystallinity, chemical structure, and morphology were characterized through x-ray diffractometry, Fourier-transform infrared spectroscopy, and transmission electron microscopy, respectively. Various concentrations of NCC (0%, 0.5%, 1%, and 1.5%) were added to reinforce the GIC matrix. Mechanical tests including compressive strength, flexural strength, hardness, and shear bond strength were conducted on the modified GIC samples. The addition of NCC resulted in increased hardness and shear bond strength values, with 1% NCC showing the highest values compared to other concentrations. However, there was no significant improvement observed in the compressive and flexural strength of the modified GIC. Failure mode test revealed a reduction in adhesive failure with the addition of NCC. Incorporating small amounts of NCC (0.5%-1%) suggests a promising and affordable modification of GIC restorative material using biomass residue, resulting in improved mechanical properties.

Evaluating antimicrobial, cytotoxic and immunomodulatory effects of glass ionomer cement modified by chitosan and hydroxyapatite

OBJECTIVES

This study aimed to assess antimicrobial efficacy, cytotoxicity, and cytokine release (IL-1b, IL-6, IL-10, TNF-α) from human dental pulp stem cells (hDPSCs) of chitosan (CH) and hydroxyapatite (HAp)-modified glass ionomer cements (GIC).

METHODS

GICs with varied CH and HAp concentrations (0 %, 0.16 %, 2 %, 5 %, 10 %) were tested against S. mutans for 24 h or 7 days. Antimicrobial activity was measured using an MTT test. Cytotoxicity evaluation followed for optimal concentrations, analyzing mitochondrial activity and apoptosis in hDPSCs. Cytokine release was assessed with MAGPIX. Antimicrobial analysis used Shapiro-Wilk, Kruskal-Wallis, and Dunnett tests. Two-way ANOVA, Tukey, and Dunnett tests were applied for hDP metabolism and cytokine release.

RESULTS

CH 2 % and HAp 5 % significantly enhanced GIC antimicrobial activity, especially after seven days. In immediate analysis, all materials showed reduced mitochondrial activity compared to the control. After 24 h, CH demonstrated mitochondrial metabolism similar to the control. All groups exhibited mild cytotoxicity (∼30 % cell death). Only IL-6 was influenced, with reduced release in experimental groups.

SIGNIFICANCE

CH 2 % and HAp 5 % were most effective for antibacterial effects. GIC-CH 2 % emerged as the most promising formula, displaying significant antibacterial effects with reduced hDPSC toxicity.

Green Synthesis, Characterization, and Evaluation of the Antimicrobial Properties and Compressive Strength of Hydroxyapatite Nanoparticle-Incorporated Glass Ionomer Cement

Background Glass ionomer cement (GIC) plays a vital role in dental restorative procedures, serving purposes such as filling, luting, and adhesion. However, its inadequate mechanical properties pose challenges, especially in areas experiencing significant stress. To overcome this limitation, nanohydroxyapatite (nHA), known for its bioactive phosphate content, is added to the GIC at specific concentrations to improve its properties. Aim  We aim to evaluate the antimicrobial property and compressive strength of green-mediated nHA-incorporated GIC. Material and methods Green synthesis of hydroxyapatite nanoparticles was prepared using Moringa oleifera extract in a solvent form and eggshell waste served as the calcium source. These nHA powders were then integrated into the GIC at varying concentrations (3%, 5%, and 10%) designated as Group I, Group II, and Group III, respectively, while Group IV (control) consisted of conventional GIC. Specimens were fabricated and subjected to chemical structure analysis through Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The antimicrobial activity and compressive strength of all groups were investigated. The antimicrobial activity against Streptococcus mutans and Lactobacillus was evaluated through the minimum inhibitory concentration (MIC) test, while compressive strength was evaluated by measuring the maximum force endured by the specimen before fracturing. Data analysis utilized IBM SPSS Statistics software, employing repeated measures ANOVA to determine mean MIC values and compressive strength, with Tukey's posthoc test for pairwise comparisons. Results The results of the study showed that the antimicrobial efficacy of nHA GIC improved with increasing weight percent (% wt) of the additive, exhibiting significantly enhanced activity against Streptococcus mutans and Lactobacillus compared to the control group (Group IV) with statistical significance (p < 0.05). Moreover, the compressive strength exhibited notable enhancements in the modified groups, including Group I (172.55 ± 0.76), Group II (178.16 ± 0.760), and Group III (182.45 ± 0.950), when compared to the control (162.46 ± 1.606), with statistically significant differences (p < 0.05). Conclusion The study demonstrates that the incorporation of green-mediated nHA-containing GIC results in superior antimicrobial efficacy and compressive strength compared to the control group (Group IV). In particular, the highest concentration of nHA-modified GIC (10%) exhibited the most favorable antimicrobial properties along with increased strength. Therefore, utilizing green-mediated nHA in the GIC shows promise as an effective restorative material. Future investigations should delve into the molecular chemistry and bonding mechanisms to further explore its potential.

Exploring the biomedical potential of a novel modified glass ionomer cement against the pandrug-resistant oral pathogen Candida albicans SYN-01

Dental caries is an infectious disease that is a major concern for dentists. Streptococci and Lactobacilli were long thought to be the primary etiology responsible for caries. Candida albicans with acidogenic and aciduric characteristics has recently been implicated in the onset and progression of cariogenic lesions. Moreover, due to the increased resistance to common antimicrobials, the discovery of innovative candidates is in high demand. Therefore, our study might be the first report that explores the efficacy of glass ionomer cement (GIC) incorporated with a newly modified carboxylated chitosan derivative (CS-MC) against multidrug-resistant (MDR) and/or pandrug resistant (PDR) C. albicans isolated from the oral cavity. In this work, four CS-MC-GIC groups with different concentrations were formulated. Group four (CS-MC-GIC-4) gave a significant performance as an anticandidal agent against selected PDR Candida strain, with an obvious decrease in its cell viability and high antibiofilm activity. It also, enhanced all the mechanical properties and supports cell viability of Vero cells as a nontoxic compound. Moreover, CS-MC-GIC-4 inhibited neuraminidases completely, which might provide a novel mechanism to prevent dental/oral infections. Thus, findings in this study open up new prospect of the utilization of CS-MC-GIC as a novel dental filling material against oral drug-resistant Candida.

Chitosan Resin-Modified Glass Ionomer Cement Containing Epidermal Growth Factor Promotes Pulp Cell Proliferation with a Minimum Effect on Fluoride and Aluminum Release

The development of biomaterials that are able to control the release of bioactive molecules is a challenging task for regenerative dentistry. This study aimed to enhance resin-modified glass ionomer cement (RMGIC) for the release of epidermal growth factor (EGF). This RMGIC was formulated from RMGIC powder supplemented with 15% (w/w) chitosan at a molecular weight of either 62 or 545 kDa with 5% bovine serum albumin mixed with the same liquid component as the Vitrebond. EGF was added while mixing. ELISA was used to determine EGF release from the specimen immersed in phosphate-buffered saline at 1 h, 3 h, 24 h, 3 d, 1 wk, 2 wks, and 3 wks. Fluoride and aluminum release at 1, 3, 5, and 7 d was measured by electrode and inductively coupled plasma optical emission spectrometry. Pulp cell viability was examined through MTT assays and the counting of cell numbers using a Coulter counter. The RMGIC with 65 kDa chitosan is able to prolong the release of EGF for significantly longer than RMGIC for at least 3 wks due to its retained bioactivity in promoting pulp cell proliferation. This modified RMGIC can prolong the release of fluoride, with a small amount of aluminum also released for a limited time. This biomaterial could be useful in regenerating pulp-dentin complexes.

Current antibacterial agents in dental bonding systems: a comprehensive overview

Dental caries is mainly caused by oral biofilm acid, and the most common dental restoration treatment is composite dental restorations. The main cause of failure is secondary caries adjacent to the restoration. Long-term survival of dental materials is improved by the presence of antibacterial agents, which selectively inhibit bacterial growth or survival. Chemical, natural and biomaterials have been studied for their antimicrobial activities and antibacterial bonding agents have been improved. Their usage has been increased to inhibit the growth of invading and residual bacteria in the oral cavity, as biofilm accumulation increases the risk of treatment failure. In this article, the success and applications of antibacterial agents are discussed in dental bonding systems.

Effect of germanium oxide on the structural aspects and bioactivity of bioactive silicate glass

Ternary silicate glass (69SiO₂-27CaO-4P₂O₅) was synthesized with the sol-gel route, and different percentages of germanium oxide GeO₂ (6.25, 12.5, and 25%) and polyacrylic acid (PAA) were added. DFT calculations were performed at the B3LYP/LanL2DZ level of theory for molecular modelling. X-ray powder diffraction (XRPD) was used to study the effect of GeO₂/PAA on the structural properties. The samples were further characterized using DSC, ART-FTIR, and mechanical tests. Bioactivity and antibacterial tests were assessed to trace the influence of GeO₂ on biocompatibility with biological systems. Modelling results demonstrate that molecular electrostatic potential (MESP) indicated an enhancement of the electronegativity of the studied models. While both the total dipole moment and HOMO/LUMO energy reflect the increased reactivity of the P₄O₁₀ molecule. XRPD results confirmed the samples formation and revealed the correlation between the crystallinity and the properties, showing that crystalline hydroxyapatite (HA) is clearly formed in the highest percentages of GeO₂, proposing 25% as a strong candidate for medical applications, consistent with the results of mechanical properties and the rest of the characterization results. Simulated body fluid (SBF) in vitro experiments showed promising biocompatibility. The samples showed remarkable antimicrobial and bioactivity, with the strongest effect at 25%. The experimental findings of this study revealed that the incorporation of GeO2 into the glass in terms of structural characteristics, bioactivity, antimicrobial properties, and mechanical properties is advantageous for biomedical fields and especially for dental applications.

Exploring the Antimicrobial Activity of Sodium Titanate Nanotube Biomaterials in Combating Bone Infections: An In Vitro and In Vivo Study

The majority of bone and joint infections are caused by Gram-positive organisms, specifically staphylococci. Additionally, gram-negative organisms such as E. coli can infect various organs through infected wounds. Fungal arthritis is a rare condition, with examples including Mucormycosis (Mucor rhizopus). These infections are difficult to treat, making the use of novel antibacterial materials for bone diseases crucial. Sodium titanate nanotubes (NaTNTs) were synthesized using the hydrothermal method and characterized using a Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmission Electron Microscope (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and Zeta sizer. The antibacterial and antifungal activity of the NaTNT framework nanostructure was evaluated using Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Disc Diffusion assays for bacterial activity, and Minimum Fungicidal Concentration (MFC) for antifungal investigation. In addition to examining in vivo antibacterial activity in rats through wound induction and infection, pathogen counts and histological examinations were also conducted. In vitro and in vivo tests revealed that NaTNT has substantial antifungal and antibacterial effects on various bone-infected pathogens. In conclusion, current research indicates that NaTNT is an efficient antibacterial agent against a variety of microbial pathogenic bone diseases.

Characterization of Ag-Ion Releasing Zeolite Filled 3D Printed Resins

There has been profound growth in the use of 3D printed materials in dentistry in general, including orthodontics. The opportunity to impart antimicrobial properties to 3D printed parts from existing resins requires the capability of forming a stable colloid incorporating antimicrobial fillers. The objective of this research was to characterize a colloid consisting of a 3D printable resin mixed with Ag-ion releasing zeolites and fumed silica to create 3D printed parts with antiviral properties. The final composite was tested for antiviral properties against SARS-CoV-2 and HIV-1. Antiviral activity was measured in terms of the half-life of SARS-CoV-2 and HIV-1 on the composite surface. The inclusion of the zeolite did not interfere with the kinetics measured on the surface of the ATR crystal. While the depth of cure, measured following ISO4049 guidelines, was reduced from 3.8 mm to 1.4 mm in 5 s, this greatly exceeded the resolution required for 3D printing. The colloid was stable for at least 6 months and the rheological behavior was dependent upon the fumed silica loading. The inclusion of zeolites and fumed silica significantly increased the flexural strength of the composite as measured by a 3 point bend test. The composite released approximately 2500 μg/L of silver ion per gram of composite as determined by potentiometry. There was a significant reduction of the average half-life of SARS-CoV-2 (1.9 fold) and HIV-1 (2.7 fold) on the surface of the composite. The inclusion of Ag-ion releasing zeolites into 3D-printable resin can result in stable colloids that generate composites with improved mechanical properties and antiviral properties.

An ex vivo evaluation of physico-mechanical and anti-biofilm properties of resin-modified glass ionomer containing ultrasound waves-activated nanoparticles against Streptococcus mutans biofilm around orthodontic bands

BACKGROUND

The present study evaluated the physico-mechanical and antimicrobial properties of ultrasound waves-activated modified-resin glass ionomer containing nanosonosensitizers such as nano-curcumin (n-Cur), nano-emodin (n-Emo), and nano-quercetin (n-Qct) against Streptococcus mutans biofilm on the surface of modified-resin glass ionomer bonded orthodontic bands.

MATERIALS AND METHODS

A total of 50 human molar teeth were used in this study. The shear bond strength (SBS), adhesive remnant index (ARI), setting time, and fluoride release of modified orthodontics cement containing different concentrations of n-Cur, n-Emo, and n-Qct (0, 2, 5, and 10%) were measured. The antimicrobial effectiveness was assessed against S. mutans by the biofilm inhibition test, and the Log₁₀ colony-forming unit (CFU)/mL was evaluated.

RESULTS

SBS and setting time of modified glass ionomer decreased compared with the control group. 5% n-Emo, 2% n-Qct, and 5% n-Cur were the highest concentrations that had an insignificant difference in comparison with Transbond XT (P = 0.647, 0.819, and 0.292, respectively). The groups were not significantly different in terms of ARI score (P > 0.05). The highest and lowest setting time belonged to the control and 5% n-Emo groups, respectively; this difference in setting time was significant (P < 0.05). Ultrasound waves and 0.2% CHX significantly reduced S. mutans biofilms compared with the control group (P < 0.001), and minimum S. mutans colony count was shown in 0.2% CHX and 5% n-Emo groups. The addition of nanosonosensitizers to the glass ionomer did not compromise the fluoride release of the glass ionomer.

CONCLUSION

It could be concluded that resin-modified glass ionomer containing ultrasound waves-activated 5% n-Emo reduces S. mutans biofilm around orthodontic bands with no adverse effect on SBS, ARI, and its application in the clinic.

Modification and Functionalization of Zeolites for Curcumin Uptake

This work shows that hierarchical zeolites are promising systems for the delivery of biologically relevant hydrophobic substances, such as curcumin. The validity of using piperine as a promoter of curcumin adsorption was also evaluated. The use of pure curcumin is not medically applicable due to its low bioavailability and poor water solubility. To improve the undesirable properties of curcumin, special carriers are used to overcome these shortcomings. Hierarchical zeolites possessing secondary mesoporosity are used as pharmaceutical carrier systems for encapsulating active substances with low water solubility. This porosity facilitates access of larger reagent molecules to the active sites of the material, preserving desirable adsorption properties, acidity, and crystallinity of zeolites. In this work, methods are proposed to synthesize hierarchical zeolites based on a commercial FAU-type zeolite. Studies on the application and adsorption kinetics of curcumin using commercial FAU-type zeolite and hierarchical zeolites based on commercial FAU-type zeolite are also included.

Effect Of Nano-Bioactive Glass On Flexural Strength And Antimicrobial Activity Of Resin-Modified Glass Ionomer Cement Containing 58S Nano-Bioactive Glass

Introduction:

Bioactive glass (BAG) is increasingly used in dentistry, aiming to provide superior mechanical properties, optimal chemical stability, and favorable antimicrobial activity in the oral environment. This study aimed to measure the flexural strength (FS) and antimicrobial activity of resin-modified glass ionomer (RMGI) cement containing 58S nano-BAG.

Materials and Methods:

In this in vitro study, 0wt (Weight) %, 10wt%, 20wt%, and 30wt% 58S nano-BAG particles were added to RMGI powder in groups 1 to 4, respectively (n=10). Forty specimens were fabricated in metal molds (2 x 25 x 2 mm), and their FS was measured by using a three-point bending test at a crosshead speed of 0.5 mm/min. The antibacterial activity of the materials against Streptococcus mutants was assessed by the disc diffusion test. In addition to the abovementioned experimental groups, one control group (n=10) containing 100% BAG was also considered. Data were analyzed by one-way ANOVA and Tukey’s test.

Results:

The mean (± standard deviation) FS was 38.71±8.84, 43.61±17.34, 45.62±15.89, and 54.71±14.25 MPa in groups 1 to 4, respectively. No significant difference was noted in FS among the groups (P=0.06). A significant difference was found in the diameter of the growth inhibition zone among the groups (P<0.05), and group 4 containing 30wt% BAG showed minimal bacterial growth.

Conclusion:

The addition of 10wt%, 20wt% and 30wt% nano-BAG to RMGI powder did not significantly change the FS but the addition of 30wt% nano-BAG to RMGI significantly inhibited the bacterial growth.

Randomized Clinical Trial of Heated High Viscosity Glass Ionomer Class II Restorations in Deciduous Molars: 12 Months Follow Up

Objective: New generation High Viscosity Glass Ionomer Cements (HVGICs) have enhanced physical and mechanical properties. By effectively closing the restoration margin, it ensures that the restorations will last longer. The aim of this study was to investigate the clinical performances of heat-cured versus non heated HVGIC in class II restorations of deciduous molars. Methods: This randomized, split mouth, multicentre study was performed in four different centres. A total of 250 deciduous molars from 88 individuals were randomly allocated to one of the following groups: 1) non-heated (n = 125) 2) heated (n = 125) and restored with a HVGIC using LED light for heat application. Restorations were clinically evaluated according to the modified USPHS at the baseline, 6 months and 12 months. The survival analysis was performed by Kaplan Meier and Life Tables. This study was retrospectively registered to the ClinicalTrials.gov with the ID number of NCT04291872 at 2nd March 2020. Results: No statistically significant differences were found between the groups regarding to modified USPHS criteria (p&gt;0.05). Success rate in retention criteria was 94.1% of the heat-cured and 92.6% of the non-heated restorations after 12 months. The mean survival time was 11.8 ±0.1 months in the heated group, while 11.9±0.1 months in the non-heated group. Conclusion: The heat treated HVGIC for Class II restorations did not show any significant differences in 12 months’ follow-up compared with the conventional technique.

Effects of Nanohydroxyapatite Incorporation into Glass Ionomer Cement (GIC)

Glass ionomer cement (GIC) or polyalkenoate cement is a water-based cement that is commonly used in clinical dentistry procedures as a restorative material. It exhibits great properties such as fluoride-ion release, good biocompatibility, ease of use and great osteoconductive properties. However, GIC’s low mechanical properties have become a major drawback, limiting the cement’s usage, especially in high stress-bearing areas. Nanohydroxyapatite, which is a biologically active phosphate ceramic, is added as a specific filler into glass ionomer cement to improve its properties. In this review, it is shown that incorporating hydroxyapatite nanoparticles (nHA) into GIC has been proven to exhibit better physical properties, such as increasing the compressive strength and fracture toughness. It has also been shown that the addition of nanohydroxyapatite into GIC reduces cytotoxicity and microleakage, whilst heightening its fluoride ion release and antibacterial properties. This review aims to provide a brief overview of the recent studies elucidating their recommendations which are linked to the benefits of incorporating hydroxyapatite nanoparticles into glass ionomer cement.

Bond Strength and Microleakage of a Novel Glass Ionomer Cement Containing Silver Diamine Fluoride

Objectives  To investigate the shear bond strength and microleakage of glass ionomer cement (GIC) containing silver diamine fluoride (SDF).

Materials and Methods  Sound human permanent premolars were divided into the following three groups: 1) GIC (Fuji IX), 2) GICSDF-S: GIC + SDF (Saforide), and 3) GICSDF-T: GIC + SDF (Topamine). Shear bond strength ( n  = 14/group) was measured using a universal testing machine and compared between groups (one-way ANOVA and Tukey HSD, p  < 0.05). Microleakage ( n  = 15/group) at enamel and dentin margins was scored using a stereomicroscope (10x) and compared between groups (Chi-square, p  < 0.05).

Results  There were significant differences in shear bond strength between the GIC and GICSDF-S groups and between the GIC and GICSDF-T groups. The GIC group had the lowest shear bond strength among the groups; however, there was no significant difference between the GICSDF-S and GICSDF-T groups. The microleakage test results were not significantly different between groups at the enamel margin or dentin margins. Although the GIC group demonstrated a higher dye penetration score at the enamel and dentin margins, the difference was not significant.

Conclusions  Within the limitations of this study, we conclude that incorporating SDF into GIC results in higher shear bond strength while not increasing microleakage at the enamel and dentin margins.

Solution photo-copolymerization of acrylic acid and itaconic acid: The effect of polymerization parameters on mechanical properties of glass ionomer cements

OBJECTIVE

To synthesize a series of poly (acrylic acid-co-itaconic acid) (P(AA-co-IA)) copolymers with different molecular weights (MWs) through a facile water-based solution photopolymerization and to investigate the operational and mechanical properties of the experimental glass-ionomer (GI) cements made of the ionomers.

METHODS

Thioglycolic acid (TGA) was used as a chain transfer agent to synthesize P(AA-co-IA) ionomers with different MWs through the solution photopolymerization. The chemical structure, MWs, and rheological properties of the copolymers were fully characterized. The GI cements were prepared using the ionomer solutions in different MWs and concentrations. Finally, the operating and mechanical properties of the experimental GI cements were investigated and compared with those of a commercially available GI cement.

RESULTS

The synthesis and composition of the P(AA-co-IA) were approved by spectroscopy analyses. The results revealed that by increasing the TGA content, MW and polydispersity index (PDI) of the synthesized copolymers demonstrate a decreasing trend from 4.5 × 104 g/mol (PDI of 2.45) to 7.4 × 103 g/mol (PDI of 1.62). Accordingly, the viscosity of copolymers decreased with increasing the TGA concentration in the polymerization recipes. Setting times of the cements increased with reducing the MWs and ionomer concentration. The compressive and flexural strengths of GI cements were improved by increasing the MWs, ionomers concentration, and storage time.

SIGNIFICANCE

The solution photopolymerization provides a facile and environmentally safe method to synthesize P(AA-co-IA) copolymers with controlled MWs. The structure-property relationships presented in the study also provide valuable information in the production and improvement of the GI cements.

Human Organs-on-Chips: A Review of the State-of-the-Art, Current Prospects, and Future Challenges

New emerging technologies, remarkably miniaturized 3D organ models and microfluidics, enable simulation of the real in vitro microenvironment ex vivo more closely. There are many fascinating features of innovative organ-on-a-chip (OOC) technology, including the possibility of integrating semipermeable and/or stretchable membranes, creating continuous perfusion of fluids into microchannels and chambers (while maintaining laminar flow regime), embedding microdevices like microsensors, microstimulators, micro heaters, or different cell lines, along with other 3D cell culture technologies. OOC systems are designed to imitate the structure and function of human organs, ranging from breathing lungs to beating hearts. This technology is expected to be able to revolutionize cell biology studies, personalized precision medicine, drug development process, and cancer diagnosis/treatment. OOC systems can significantly reduce the cost associated with tedious drug development processes and the risk of adverse drug reactions in the body, which makes drug screening more effective. The review mainly focus on presenting an overview of the several previously developed OOC systems accompanied by subjects relevant to pharmacy-, cancer-, and placenta-on-a-chip. The challenging issues and opportunities related to these systems are discussed, along with a future perspective for this technology.

Effect of zinc oxide nanoparticles on physical and antimicrobial properties of resin-modified glass ionomer cement

Background:

To improve the limitations, many modifications in the resin-modified glass ionomer (RMGI) composition have been proposed. In this study, we evaluated the effect of different concentrations of zinc oxide (ZnO) nanoparticles incorporated into RMGI cement on its physical and antimicrobial properties.

Materials and Methods:

In this in vitro study, ZnO nanoparticles with 0–4 wt.% concentrations were incorporated into RMGI. The following tests were carried out: (a) Antibacterial activity against Streptococcus mutans tested by disc diffusion method, (b) mechanical behavior assessment by measuring flexural strength (FS) and flexural modulus (FM), (c) micro-shear bond strength (μ-SBS), and (d) fluoride and zinc release. Data were analyzed using the statistical tests of ANOVA, t-test, and Tukey's HSD post hoc in SPSS V22. The level of significancy was 0.05.

Results:

In the disc diffusion method, specimens with 2 wt.% ZnO nanoparticles showed the highest antimicrobial efficacy (P < 0.05). After 1 month of water storage, no significant difference was observed in FS and FM of the samples (P > 0.05). In 2 wt.% ZnO nanoparticles group, μSBS increased in the first 7 days but decreased by 17% after one month, which showed a significant difference with that of the control group. The fluoride release did no change in the ZnO nanoparticle-containing group compared with the control group at all time intervals.

Conclusion:

Incorporation of 2 wt.% ZnO nanoparticles into the RMGI cement adds antimicrobial activity to the cement without sacrificing FS and fluoride release properties, while decreased μSBS.

Microhardness and Fluoride Release of Glass Ionomer Cement Modified with a Novel Al+3 Complex to Enhance Its Antimicrobial Activity

Objectives

To synthesize and characterize a novel Al⁺³ complex with 2-(2-hydroxyphenyl)-1H-benzimidazole (HL) to be added to a restorative glass ionomer cement (GIC) to enhance its antimicrobial activities and to evaluate the Vickers microhardness (HV) and fluoride release (FR) of the modified GIC.

Materials and Methods

Al⁺³ complex was synthesized by the addition of 1 mmol (0.210 g) of HL to 1 mmol (0.342 g) of aluminum sulfate in ethanol. The resulting solution was then refluxed under stirring for 24 h and then collected by filtration and dried in a vacuum desiccator over an anhydrous CaCl₂. Characterization of Al⁺³ complex was carried out by Fourier transform infrared spectroscopy (FTIR), elemental microanalysis, thermal gravimetric analysis (TGA), molar conductance, ¹H NMR spectra, and electron impact-mass spectrometry. The antimicrobial activity of Al⁺³ complex-modified GIC (Al-GIC) was studied by the “cut plug method” against Gram-negative bacteria (Acinetobacter baumannii) and Gram-positive bacteria (Staphylococcus aureus, Enterococcus, and Streptococcus mutants) and fungi (Candida albicans). HV was evaluated by a digital microhardness tester (Zwick/Roell, Indentec, ZHVμ-S, West Midlands, England). Fluoride levels in ppm were obtained using the ion-selective electrode connected to a digital meter. A one-way ANOVA and Bonferroni test were used to analyze the data with the significance level established at p ≤ 0.05.

Results

Synthesis of Al⁺³ complex was confirmed by FTIR, elemental microanalysis TGA, molar conductance, ¹H NMR spectra, and electron impact-mass spectrometry. Al-GICs exhibited an enhanced antibacterial activity against all studied microorganisms as confirmed by the growth of inhibition zones compared to control GIC (C-GIC). Though there was a slight reduction in HV and FR with increasing the added percent of Al⁺³ complex, no significant differences were found between the studied groups.

Conclusions

Addition of Al⁺³ complex to GIC powder enhanced the antimicrobial activity of GIC materials. As there was a negligible insignificant reduction in HV and FR upon the addition of Al⁺³ complex, Al-GICs can be used with a guaranteed degree of clinical success.

Efficacy of antimicrobial photodynamic therapy (aPDT) in reducing cariogenic bacteria in primary deciduous dentine

AIM

The aim is to systematically review the efficacy of aPDT in minimizing cariogenic bacteria in primary dentine when compared to tooth preparation and endodontic debridement.

MATERIALS AND METHODS

The focused question was: Is aPDT (intervention) effective in minimizing the cariogenic bacteria (outcome) in deciduous dentine (participants) after caries removal when compared to before aPDT or mechanical caries removal alone (controls). The keywords that were used were: 'antimicrobial photodynamic therapy', 'dentine', 'primary teeth' and 'deciduous teeth' in different combinations. Following the exclusion of the irrelevant studies, eight (seven clinical studies and one in vitro study) studies were included in the review. The data from each study was extracted and the quality of each article was assessed.

RESULTS

In four out of the eight studies, aPDT with methylene blue or toluidine blue had improved the efficacy of microbial reduction in deciduous dentine when compared to conventional root canal treatment or caries removal. In four studies, no significant improvement in microbial reduction was observed following aPDT compared to caries removal or endodontic debridement without aPDT. Four studies received an overall quality grading of 'medium', three studies were assessed as having a 'low' quality and only one study received an overall grading of 'high' quality.

CONCLUSION

Within the limitations of this review, aPDT may improve the anti-bacterial efficacy of restorative and endodontic procedures in deciduous teeth. However, due to lack of long-term clinical trials and robust study designs, the efficacy of aPDT in minimizing cariogenic bacteria in deciduous dentine is debatable.

Effect of Yellow Propolis on Biocompatibility of Cements: Morphological and Immunohistochemistry Analysis

Objective  The focus of this study was to evaluate the biocompatibility of ionomer cements modified with ethanolic extracts of propolis (EEP) in different concentrations and time intervals.

Materials and Methods  In total, one hundred and thirty-five male Wistar rats were randomized into nine groups: Control, Groups Meron, and Groups Ketac (conventional, and added with 10, 25, 50% EEP, respectively). Histological analyses of inflammatory infiltrate and collagen fibers, and immunohistochemistry of CD68+ for macrophages (MOs) and multinucleated giant cells (MGCs) were performed.

Statistical Analysis  Data were analyzed using the Kruskal—Wallis and Dunn ( p < 0.05) tests.

Results  Intense inflammatory infiltrate was demonstrated in the cements with 10% EEP at 7 days and 15 days ( p < 0.05), only Group Ketac 10% EEP ( p = 0.01) at 30 days. A smaller quantity of collagen fibers was observed in the cements with 10% EEP ( p = 0.01) at 7 days, and Group Meron 10% EEP ( p = 0.04) at 15 days. MOs and MGCs showed significant difference for the cements with 10% EEP ( p = 0.01) at 7 and 15 days. At 30 days, MOs persisted in the Groups with 10% EEP.

Conclusions  The concentration of 10% EEP had the greatest influence on the inflammatory and tissue repair processes. The concentrations of 25 and 50% EEP demonstrated biocompatibility similar to that of cements that did not receive EEP.

Flexural Properties of Bioactive Restoratives in Cariogenic Environments

This study determined the mechanical performance of bioactive restoratives in cariogenic environments and compared the flexural properties of various bioactive materials. The materials evaluated included a conventional resin-based composite (Filtek Z350 [FZ]) and 3 bioactive restoratives, namely an alkasite (Cention N [CN]), a giomer (Beautifil-bulk Restorative [BB]), and an enhanced resin-modified glass ionomer (Activa Bioactive Restorative [AV]). Beam-shaped specimens (12 x 2 x 2 mm) were produced, randomly allocated to 4 groups (n=10), and conditioned in deionized solution, remineralizing solution, demineralizing solution (DE), or pH cycled for 14 days at 37°C. After conditioning/pH cycling, the specimens were subjected to 3-point flexural testing. Flexural data were subjected to statistical analysis using analysis of variance or Tukey's test (α=0.05). Mean flexural modulus and strength ranged from 3.54 ± 0.33 to 7.44 ± 0.28 GPa, and 87.07 ± 8.99 to 123.54 ± 12.37 MPa, respectively. While the flexural modulus of the bioactive restoratives was not affected by cariogenic/acidic conditions, flexural strength usually decreased, with the exception of CN. The strength of BB was significantly reduced by DE and pH cycling, while that of AV was lowered by DE. For all conditioning mediums, AV had a significantly lower modulus than the other materials. Apart from conditioning in DE, where differences in flexural strength was insignificant, FZ and AV were generally significantly stronger than BB and CN. The effect of cariogenic environments on flexural strength was found to be material dependent, and aside from the alkasite material (CN), cariogenic conditions were observed to significantly decrease the strength of bioactive restoratives.

The effect of selective carious tissue removal and cavity treatments on the residual intratubular bacteria in coronal dentine

Background/purpose

The use of cavity treatments may help in the reduction of bacteria remaining in dentinal tubules after selective carious tissue removal. This study aimed to investigate the effect of selective carious tissue removal and treatment with either 35% phosphoric acid +0.12% chlorhexidine or dentine conditioner on the residual intratubular bacteria in coronal dentine of deep carious lesions.

Materials and methods

Thirty carious human molars were randomly divided into three groups; group 1: untreated carious teeth (positive control), group 2: carious teeth treated with 35% phosphoric acid and chlorhexidine disinfectant after selective carious tissue removal and group 3: carious teeth treated with dentine conditioner after selective carious tissue removal. Another six non-carious teeth was used as negative control. The presence of bacteria and depth of bacteria remaining in dentinal tubules were determined by scanning electron microscopy (SEM). Chi square test and one-way, repeated-measures analysis of variance were used for statistical analysis.

Results

Using SEM, coronal dentine of group 1, 2 and 3 revealed cocci, rod and filamentous bacteria within dentinal tubules. Positive rates of bacteria detection in coronal dentine of group 1 were significant higher than those of group 2 and 3 (P < 0.05). The distance of bacteria remaining in the dentinal tubules in group 1, 2 and 3 were 1149.14 ± 384.44, 707.98 ± 357.19 and 869.25 ± 470.75 μm, respectively.

Conclusion

Both treatment groups had similar ability to reduce the number of intratubular bacteria in coronal dentine of carious teeth, but not complete elimination.

A self-cured glass-ionomer cement with improved antibacterial function and hardness

A novel antimicrobial dental self-cured glass-ionomer cement has been developed and evaluated. Alumina filler particles were covalently coated with an antibacterial polymer and blended into a self-cured glass-ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Results showed that the modified cements exhibited a significantly enhanced antibacterial activity along with improved surface hardness. Effects of antibacterial moiety content, alumina particle size and loading, and total filler content were investigated. It was found that increasing antibacterial moiety content, particle size and loading, and total filler content generally increased surface hardness. Increasing antibacterial moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size showed a negative impact on antibacterial activity. The leaching tests indicate no cytotoxicity produced from the modified cements to both bacteria and 3T3 mouse fibroblast cells.

One-year evaluation of a new restorative glass ionomer cement for the restoration of non-carious cervical lesions in patients with systemic diseases: a randomized, clinical trial

OBJECTIVE

This randomized and clinical trial aimed to evaluate the performance of a new restorative Glass Ionomer Cement (GIC) for the restoration of non-carious cervical lesions (NCCLs) of patients with systemic diseases compared with a posterior resin composite after 12 months.

METHODOLOGY

134 restorations were placed at 30 patients presenting systemic diseases by a single clinician. NCCLs were allocated to two groups according to restorative system used: a conventional restorative GIC [Fuji Bulk (GC, Tokyo Japan) (FB)] and a posterior resin composite [G-ænial Posterior (GC, Tokyo Japan) (GP)] used with a universal adhesive using etch&rinse mode. All restorative procedures were conducted according to manufacturer's instructions. Restorations were scored regarding retention, marginal discoloration, marginal adaptation, secondary caries, surface texture, and post-operative sensitivity using modified United States Public Health Service (USPHS) criteria after 1 week (baseline), 6, and 12 months. Descriptive statistics were performed using chi-square tests. Cochran Q and Mc Nemar's tests were used to detect differences over time.

RESULTS

After 12 months, recall rate was 93% and the rates of cumulative retention failure for FB and GP were 4.9% and 1.6% respectively. Both groups presented similar alpha rates for marginal adaptation (FB 86.2%, GP 95.5%) and marginal discoloration (FB 93.8%, GP 97%) at 6-month recall, but FB restorations showed higher bravo scores than GP restorations for marginal adaptation and marginal discoloration after 12 months (p<0.05). Regarding surface texture, 2 FB restorations (3.1%) were scored as bravo after 6 months. All restorations were scored as alpha for secondary caries and postoperative sensitivity after 12 months.

CONCLUSION

Although the posterior resin composite demonstrated clinically higher alpha scores than the conventional GIC for marginal adaptation and discoloration, both materials successfully restored NCCLs at patients with systematic disease after a year.

CLINICAL RELEVANCE

Due to its acceptable clinical results, the tested conventional restorative GIC can be used for the restoration of NCCLs of patients with systemic diseases.

An antibacterial dental light-cured glass-ionomer cement with improved hardness

An antibacterial dental light-cured glass-ionomer cement has been developed and evaluated. An antibacterial furanone derivative was synthesized and covalently attached onto the surface of alumina filler particles. The formed antibacterial fillers were then mixed into a light-curable glass-ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Effects of coated furanone moiety content on the modified fillers, modified alumina filler particle size and loading, and total glass filler content were investigated. Results showed that increasing antibacterial furanone content, modified particle size and loading, and total glass filler content generally increased surface hardness. Increasing furanone moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size decreased antibacterial activity. The leaching tests indicate that the modified experimental cement showed no leachable antibacterial component to bacteria and cells.

Poloxamer: A versatile tri-block copolymer for biomedical applications

Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). Some chemical characteristics of poloxamers such as temperature-dependent self-assembly and thermo-reversible behavior along with biocompatibility and physiochemical properties make poloxamer-based biomaterials promising candidates for biomedical application such as tissue engineering and drug delivery. The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. Poloxamers are also used for the modification of hydrophobic tissue-engineered constructs. This article collects the recent advances in design and application of poloxamer-based biomaterials in tissue engineering, drug/gene delivery, theranostic devices, and bioinks for 3D printing. STATEMENT OF SIGNIFICANCE: Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. However, no reports have systematically reviewed the critical role of poloxamer for biomedical applications. Research on poloxamers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature.

Evaluation of the Physicochemical and Antibacterial Properties of Experimental Adhesives Doped with Lithium Niobate

The aim of the present study was to formulate dental adhesives with different concentrations of LiNbO₃ and to evaluate their physicochemical and antibacterial properties. A dental adhesive was formulated using methacrylate monomers and photoinitiators and used as a control filler-free group. Subsequently, three experimental adhesives doped with LiNbO₃ at different concentrations (1 wt.%, 2 wt.%, and 5 wt.%) were also formulated. All the experimental adhesives were assessed to evaluate the degree of conversion (DC), softening in solvent, immediate and long-term microtensile bond-strength (μ-TBS), radiopacity, ultimate tensile strength, and antibacterial activity. The incorporation of 1 wt.% of LiNbO₃ had no negative effect on the DC of the adhesive resin compared to the control group (p > 0.05). We observed a decrease in the percentage of softening in solvent in the group LiNbO₃ at 1 wt.% (p < 0.05). The addition of LiNbO₃ increased the radiopacity at a concentration above 2 wt.%, and there was also an increase in cohesive strength (p < 0.05). The immediate μ-TBS increased for LiNbO₃ at 5 wt.% (p < 0.05), and there was no statistical difference for the other groups compared to the control (p > 0.05). After six months, the group with 5 wt.% still presented the highest μ-TBS (p < 0.05). The adhesives showed no antimicrobial activity (p > 0.05). LiNbO₃ was successfully incorporated in dental adhesives, increasing the radiopacity and their resistance to degradation. Although LiNbO₃ offered no antibacterial properties, the reliability of LiNbO₃ incorporation in the adhesive encourages new tests to better investigate the antimicrobial action of LiNbO₃ through temperature variation.

Protective Effects of GIC and S-PRG Filler Restoratives on Demineralization of Bovine Enamel in Lactic Acid Solution

This study was aimed at investigating the protective effects of glass ionomer cement (GIC) and surface pre-reacted glass ionomer (S-PRG) fillers used as dental restorative materials on demineralization of bovine enamel. GlasIonomer FX ULTRA (FXU), Fuji IX GP Extra (FIXE), CAREDYNE RESTORE (CDR) were used as GICs. PRG Barrier Coat (BC) was used as the S-PRG filler. They were incubated in a lactic acid solution (pH = 4.0) for six days at a temperature of 37 °C. The mineral was etched from the enamel surface, and a large number of Ca and P ions were detected in solution. The Al, F, Na, Sr, and Sr ions were released in GICs and S-RPG fillers. The Zn ion was released only in CDR and the B ion was released only in BC. The presence of apparent enamel prism peripheries was observed after six days of treatment for the group containing only enamel blocks. pH values for the FXU, FIXE, CDR, BC, and enamel block groups after six days were 6.5, 6.6, 6.7, 5.9, and 5.1, respectively. Therefore, the observed pH neutralization effect suppressed progression of caries due to the release of several ions from the restoratives.

Sustained delivery of olanzapine from sunflower oil-based polyol-urethane nanoparticles synthesised through a cyclic carbonate ring-opening reaction

The forefront horizon of biomedical investigations in recent decades is parcelling-up and delivery of drugs to achieve controlled/targeted release. In this regard, developing green-based delivery systems for a spatiotemporal controlling therapeutic agent have drawn a lot of attention. A facile route based on cyclic carbonate ring-opening reaction has been utilised to synthesise a bio-based polyol-containing urethane bond [polyol-urethane (POU)] as a nanoparticulate drug delivery system of olanzapine in order to enhance its bioavailability. After characterisation, the nanoparticles were also estimated for in vitro release, toxicity, and pharmacokinetic studies. As olanzapine has shown poor bioavailability and permeability in the brain, the sustained release of olanzapine from the designed carriers could enhance pharmacokinetic effectiveness. POU in the aqueous solution formed micelles with a hydrophobic core and embedded olanzapine under the influence of its hydrophobic nature. Drug release from the nanoparticles (90 ± 0.43 nm in diameter) indicated a specific pattern with initial burst release, and then a sustained release behaviour (82 ± 3% after 168 h), by the Higuchi-based release mechanism. Pharmacokinetics assessments of POU-olanzapine nanoparticles were carried in male Wistar rats through intravenous administration. The obtained results paved a way to introduce the POU as an efficient platform to enhance the bioavailability of olanzapine in therapeutic methods.

Electroactive poly (p-phenylene sulfide)/r-graphene oxide/chitosan as a novel potential candidate for tissue engineering

Designing novel biomaterials for tissue engineering purpose is an obvious necessary considering ever increasing need for appropriate biocompatibility and properties to achieve the maximum regeneration. In this research, a new type of biomaterial based on poly (phenylene sulfide) (PPS) and reduced graphene oxide (rGO) was synthesized and applied within chitosan based hydrogel to evaluate its performance as a wound dressing potentially. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM) and compression tests were performed to assess suitability of composite biomaterial. Thermal behavior of the PPS/rGO composite was evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The PPS/rGO composition of 90: 10 (w/w) was selected because of having the highest biocompatibility and utilized in chitosan hydrogel. Chitosan hydrogel swelling ratio was declined from 800 to 200% by PPS/rGO addition; likewise, water vapor transition rate (WVTR) was dropped. A proper biocompatibility and cell attachment was confirmed, where porosity of ca. 80% appeared promising for tissue engineering uses. Overall, the result confirmed the appropriateness of PPS/rGO for tissue engineering uses.

From microporous to mesoporous mineral frameworks: An alliance between zeolite and chitosan

Microporous and mesoporous minerals are key elements of advanced technological cycles nowadays. Nature-driven microporous materials are known for biocompatibility and renewability. Zeolite is known as an eminent microporous hydrated aluminosilicate mineral containing alkali metals. It is commercially available as adsorbent and catalyst. However, the large quantity of water uptake occupies active sites of zeolite making it less efficient. The widely-used chitosan polysaccharide has also been used in miscellaneous applications, particularly in medicine. However, inferior mechanical properties hampered its usage. Chitosan-modified zeolite composites exhibit superior properties compared to parent materials for innumerable requests. The alliance between a microporous and a biocompatible material with the accompaniment of negative and positive charges, micro/nanopores and proper mechanical properties proposes promising platforms for different uses. In this review, chitosan-modified zeolite composites and their applications have been overviewed.

Polymeric and inorganic nanoscopical antimicrobial fillers in dentistry

Failure of dental treatments is mainly due to the biofilm accumulated on the dental materials. Many investigations have been conducted on the advancements of antimicrobial dental materials. Polymeric and inorganic nanoscopical agents are capable of inhibiting microorganism proliferation. Applying them as fillers in dental materials can achieve enhanced microbicidal ability. The present review provides a broad overview on the state-of-the-art research in the field of antimicrobial fillers which have been adopted for incorporation into dental materials over the last 5 years. The antibacterial agents and applications are described, with the aim of providing information for future investigations. STATEMENT OF SIGNIFICANCE: Microbial infection is the primary cause of dental treatment failure. The present review provides an overview on the state-of-art in the field of antimicrobial nanoscopical or polymeric fillers that have been applied in dental materials. Trends in the biotechnological development of these antimicrobial fillers over the last 5 years are reviewed to provide a backdrop for further advancement in this field of research.

The effect of magnesium oxide nanoparticles on the antibacterial and antibiofilm properties of glass-ionomer cement

Objectives

This study examined the antibacterial and antibiofilm properties of conventional glass-ionomer cement (GIC) modified by the addition of magnesium oxide (MgO) nanoparticles.

Materials and methods

MgO nanoparticles were characterised by XRD, FTIR, and SEM analysis and tested for its activity against Streptococcus mutans and Streptococcus sobrinus. MgO nanoparticles were incorporated into GIC powder (Ketac Molar Easymix) at different concentrations and the antibacterial and antibiofilm activity was evaluated using agar disk diffusion and biofilm-CFU counting assays. ANOVA and Tukey's post hoc tests were used for the analysis, and the level of significance was set at p < 0.05.

Results

MgO nanoparticles showed antibacterial activity against both microorganisms (MIC = 500 μg/ml and MBC = 1000 μg/ml). A significant difference in the zones of inhibition was detected (p < 0.005). The effect was evident in the 2.5% MgO nanoparticle modified GIC while the CFU counting biofilm assay showed the effect of the added nanoparticles from 1% with a significant difference between the tested material groups (p < 0.005).

Conclusions

The MgO nanoparticle modified GIC showed effective antibacterial and antibiofilm activity against two cariogenic microorganisms and could be considered for further development as a biocompatible antibacterial dental restorative cement.

Electrically Conductive Materials: Opportunities and Challenges in Tissue Engineering

Tissue engineering endeavors to regenerate tissues and organs through appropriate cellular and molecular interactions at biological interfaces. To this aim, bio-mimicking scaffolds have been designed and practiced to regenerate and repair dysfunctional tissues by modifying cellular activity. Cellular activity and intracellular signaling are performances given to a tissue as a result of the function of elaborated electrically conductive materials. In some cases, conductive materials have exhibited antibacterial properties; moreover, such materials can be utilized for on-demand drug release. Various types of materials ranging from polymers to ceramics and metals have been utilized as parts of conductive tissue engineering scaffolds, having conductivity assortments from a range of semi-conductive to conductive. The cellular and molecular activity can also be affected by the microstructure; therefore, the fabrication methods should be evaluated along with an appropriate selection of conductive materials. This review aims to address the research progress toward the use of electrically conductive materials for the modulation of cellular response at the material-tissue interface for tissue engineering applications.

Ionic Liquid-Assisted Hydrothermal Synthesis of a Biocompatible Filler for Photo-Curable Dental Composite: From Theory to Experiment

Nanostructured hydroxyapatite (HA) is a new class of biocompatible fillers which has been recently utilized in bio hybrid materials by virtue of its excellent tissue bioactivity and biocompatibility. However, the need for higher thermal stability, solubility, surface bioactivity, radiopacity, and remineralization ability suggests a divalent cation substitution of HA for use in light curable dental restorative composites. In this work, structural and optical properties of Sr-doped hydroxyapatite were studied using first-principle calculations based on density functional theory (DFT). Next, Sr-doped hydroxyapatite (HA) was prepared via a new ionic liquid-assisted hydrothermal (ILH) route. Samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) surface area analysis, and cell viability. The obtained experimental data showed that the nucleation and crystal growth process controlled by [BMIM]Br molecules results in uniform products with small and regular particles and high specific surface areas. Finally, cytotoxicity tests showed that the as-prepared Sr-doped HA nanoparticles have good biocompatibility (≥91%), confirming their potential for use in photo-curable dental restorative composites.

Selective Contribution of Bioactive Glasses to Molecular and Cellular Pathways

Over the past few decades, biomedical scientists and surgeons have given substantial attention to bioactive glasses as promising, long-lasting biomaterials that can make chemical connections with the neighboring hard and soft tissues. Several studies have examined the cellular and molecular responses to bioactive glasses to determine if they are suitable biomaterials for tissue engineering and regenerative medicine. In this regard, different ions and additives have been used recently to induce specific characteristics for selective cellular and molecular responses. This Review briefly describes foreign-body response mechanisms and the role of adsorbed proteins as the key players in starting interactions between cells and biomaterials. It then explains the physicochemical properties of the most common bioactive glasses, which have a significant impact on their cellular and molecular responses. It is expected that, with the development of novel strategies, the physiochemical properties of bioactive glasses can be engineered to precisely control proteins' adsorption and cellular functions after implantation.

Incorporation of chlorhexidine and nano-sized sodium trimetaphosphate into a glass-ionomer cement: Effect on mechanical and microbiological properties and inhibition of enamel demineralization

OBJECTIVE

To evaluate the antimicrobial/antibiofilm and mechanical properties, and the effect on enamel demineralization of a resin-modified GIC (RMGIC) containing CHX and nano-sized sodium trimetaphosphate (TMP).

METHODS

RMGIC was associated with CHX (1.25 or 2.5%) and/or TMP (7 or 14%). Antimicrobial and antibiofilm activity were assessed using agar diffusion test and evaluation of biofilm metabolism, respectively. In addition, fluoride (F) and TMP releases as well as the diametral tensile (DTS) and compressive (CS) strength were determined. The percentage of mineral loss (%SH), integrated loss of subsurface hardness (ΔKHN) and enamel F concentrations were also evaluated.

RESULTS

RMGICs containing CHX associated or not with TMP presented higher inhibition zones and effect on S. mutans biofilm. A reduction on CS was observed only for RMGIC + 2.5%CHX and on DTS for RMGIC + 2.5%CHX + 14%TMP. The highest F and TMP releases and lowest %SH and ΔKHN values were detected for RMGIC + 1.25%CHX + 14%TMP and RMGIC + 2.5%CHX + 14%TMP. Higher enamel F concentrations were observed for TMP groups.

CONCLUSION

1.25%CHX and 14%TMP increased antimicrobial/antibiofilm action and the ability to prevent enamel demineralization, with minimal effect on the mechanical properties of RMGIC.

CLINICAL SIGNIFICANCE

RMGIC containing CHX and TMP is an alternative material for patients at high risk for dental caries and can be indicated for low-stress regions or provisional restorations.