An in vitro study to evaluate the effects of addition of zinc oxide to an orthodontic bonding agent

The Impact of Orthodontic Adhesive Containing Resveratrol, Silver, and Zinc Oxide Nanoparticles on Shear Bond Strength: An In Vitro Study

Introduction The goal of orthodontic treatment is to provide patients with esthetic smiles and functional occlusion. Despite best efforts and continuous evolution of materials, white spot lesions present a persistent hindrance to the desired treatment outcome. Nanoparticles have shown efficacy in reducing microbial activity; however, currently, there is a need for natural anti-cariogenic compounds with minimal side effects. Resveratrol is a natural compound belonging to the polyphenol group and has shown promising anti-microbial efficacy. This study aimed to evaluate the influence of dentin bonding agents incorporated with the following three different nanoparticles on shear bond strength: silver nanoparticles (Ag-Np), zinc oxide nanoparticles (ZnO-Np), and resveratrol nanoparticles (RSV-Np). Materials and methods A total of 40 premolar teeth therapeutically extracted were assigned to four equal groups of n=10 each. Groups 1, 2, and 3 used experimental adhesives doped with silver, zinc oxide, and resveratrol nanoparticles, respectively. Group 4 was bonded using unmodified adhesive. The bonded teeth were then subjected to shear bond strength (SBS) testing which was measured using a Universal Testing Machine (model no. UNITEST-10; Pune, India: ACME Engineers). Statistical analyses were performed using SPSS version 21 (Armonk, NY: IBM Corp.), employing one-way ANOVA and Tukey's post-hoc test for pairwise comparisons. Results Shear bond strength testing revealed that the control group with unmodified adhesive (8.6 MPa) had the highest SBS, followed by RSV-Np (7.6 MPa), Ag-Np (6.3 MPa), and ZnO-Np (5.65 MPa). Although the experimental groups demonstrated decreased SBS compared to the control, the values for Ag-Np and RSV-Np fell within the acceptable range. Conclusion Resveratrol nanoparticles had the least impact on shear bond strength among the experimental groups. These findings suggest that the incorporation of resveratrol nanoparticles in dentin bonding agents can provide anti-cariogenic effect without significantly impacting the adhesive's mechanical properties thereby providing a new and promising alternative to synthetic nanoparticles. Further studies are recommended to optimize the balance between anti-microbial efficacy and bond strength in clinical applications.

Design, Synthesis and Evaluation of a Series of Zinc(II) Complexes of Anthracene-Affixed Multifunctional Organic Assembly as Potential Antibacterial and Antibiofilm Agents against Methicillin-Resistant Staphylococcus aureus

A novel class of zinc(II)-based metal complexes, i.e., [Zn₂(acdp)(μ-Cl)]·2H₂O (1), [Zn₂(acdp)(μ-NO₃)]·2H₂O (2), and [Zn₂(acdp)(μ-O₂CCF₃)]·2H₂O (3) (Cl^- = chloride; NO₃^- = nitrate; CF₃CO₂^- = trifluoroacetate) of anthracene-affixed multifunctional organic assembly, H₃acdp (H₃acdp = N,N'-bis[anthracene-2-ylmethyl]-N,N'-bis[carboxymethyl]-1,3-diaminopropan-2-ol), have emerged as promising antibacterial and antibiofilm agents in the domain of medicinal chemistry. Accordingly, complexes 1-3 were synthesized by utilizing H₃acdp in combination with ZnCl₂, Zn(NO₃)₂·6H₂O, and Zn(CF₃CO₂)₂·H₂O respectively, in the presence of NaOH at ambient temperature. The complexation between H₃acdp and Zn²⁺ was delineated by a combined approach of spectrophotometric and spectrofluorometric titration studies. The stoichiometry of acdp^3-/Zn²⁺ in all three complexes is observed to be 1:2, as confirmed by spectrophotometric/spectrofluorometric titration data. Elemental analysis (C, H, N, Zn), molar conductance, FTIR, UV-vis, and thermoanalytical (TGA/DTA) data were effectively used to characterize these complexes. Besides, the structures of 1-3 were established by density functional theory (DFT) calculation using B3LYP/6-311G, specifying a self-assembled compact geometry with average Zn···Zn separation of 3.4629 Å. All three zinc complexes exhibited significantly high antibacterial and antibiofilm activity against methicillin-resistant Staphylococcus aureus (MRSA BAA1717). However, complex 1 showed a more recognizable activity than 2 and 3, with minimum inhibitory concentration (MIC) values of 200, 350, and 450 μg/mL, respectively. The antimicrobial activity was tested by employing the minimum inhibitory concentration (MIC) and time-kill assay. The crystal violet (CV) assay and microscopic study were performed to examine the antibiofilm activity. As observed, complexes 1-3 had an effect on the production of extracellular polymeric substance (EPS), biofilm cell-viability, and other virulence factors such as staphyloxanthin and hemolysin production, autoaggregation ability, and microbial cell-surface hydrophobicity. Reactive oxygen species (ROS) generated due to inhibition of staphyloxanthin production in response to 1-3 were also analyzed. Moreover, complexes 1-3 showed an ability to damage the bacterial cell membrane due to accumulation of ROS resulting in DNA leakage. In addition, complexes 1-3 displayed a synergistic/additive activity with a commercially available antibiotic drug, vancomycin, with enhanced antibacterial activity. On the whole, our investigation disclosed that complex 1 could be a promising drug lead and attract much attention to medicinal chemists compared to 2 and 3 from therapeutic aspects.

Antimicrobial properties of glass-ionomer cement incorporated with zinc oxide nanoparticles against mutans streptococci and lactobacilli under orthodontic bands: An in vivo split-mouth study

Background

The aim of this study was to assess the effect of incorporation of zinc oxide nanoparticles (ZnO-NPs) to glass-ionomer cement (GIC) (Fuji II SC, GC Corp., Tokyo, Japan) on subgingival accumulation of mutans streptococci and lactobacilli under orthodontic bands.

Materials and Methods

In order to conduct this in vivo split-mouth study, 20 patients aged between 7 and 10 years who required lingual holding arch on their mandibular first molars were divided into two groups. In one group, Fuji II SC GIC was used for cementation of the right molar band, and the same cement containing 2 wt% ZnO-NPs was used for the left one. The opposite was performed for the second group while the operator was blinded to the cement types. Subgingival microbial sampling was performed 16 weeks after cementation of lingual arch. Mutans streptococci and lactobacilli colony counts were compared. Paired t-test was used to compare the two cement groups. Data were analyzed using SPSS version 21, and P ≤ 0.05 was considered statistically significant.

Results

The mean colony counts of mutans streptococci, lactobacilli, and total bacterial count in Fuji II SC containing ZnO-NPs were significantly lower than the corresponding values in plain Fuji II SC group.

Conclusion

Incorporation of ZnO-NPs into GIC reveals antimicrobial features against mutans streptococci and lactobacilli under orthodontic bands.

Anticariogenic and Mechanical Characteristics of Resin-Modified Glass Ionomer Cement Containing Lignin-Decorated Zinc Oxide Nanoparticles

This study aims to synthesize and characterize lignin-decorated zinc oxide nanoparticles before incorporating them into resin-modified glass ionomer cement (RMGIC) to improve their anticariogenic potential and mechanical properties (shear bond strength and microhardness). Probe sonication was used to synthesize lignin-decorated zinc oxide nanoparticles which were then characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Following characterization, these were incorporated in RMGIC (Gold label, Fuji II LC). Three major groups, experimental group A (EGA), experimental group B (EGB), and control group (CG), were outlined. EGA and EGB were divided into numbered subgroups based on the ascending concentrations of nanoparticles (5, 10, and 15%) of lignin-coated zinc oxide and zinc-oxide, respectively. CG served as a control and comprised cured RMGIC samples without any incorporation. Anticariogenic analysis was conducted on experimental RMGIC samples via disk-diffusion (n = 3) and direct contact test (n = 3) against Streptococcus mutans (ATCC 25175). Optical density values for days 1, 3, and 5 were recorded via a UV-Vis spectrophotometer. A shear bond strength test was performed using 35 premolars. The adhesive remnant index was used to estimate the site of bond failure. For the Vickers microhardness test (n = 3), 100 g of load at 10 s dwell time was set. Atomic absorption spectroscopy was performed over 28 days to determine the release of zinc from the samples. All tests were analyzed statistically. The anticariogenic potential of EGA and EGB was significantly greater (p ≤ 0.05) than that of the control. The shear bond strength test reported the highest value for EGA15 with all groups exhibiting failure at the bracket/RMGIC interface. The microhardness of EGA15 yielded the highest value (p ≤ 0.05). Release kinetics displayed a steady release with EGB15 exhibiting the highest value. The EGA and EGB samples displayed good anticariogenic potential, which was sustained for 28 days without any deleterious effect on the shear bond strength and microhardness.

Assessment of Zinc-Bound Phosphate-Based Glass-Coated Denture-Relining Material with Antifungal Efficacy for Inhibiting Denture Stomatitis

This study investigated the surface properties, biocompatibility, and antifungal activity against Candida albicans of a denture-relining material coated with zinc-bound phosphate-based glass. First, zinc-bound phosphate-based glass was fabricated. A polymerized denture-relining disk was coated with zinc-bound phosphate-based glass (2%, 4%, and 6%). The surface properties of the control and experimental groups were measured, including the wettability, microhardness, color difference, and gloss. The biocompatibility was evaluated using the MTT assay according to ISO 10993-5. The antifungal activity was investigated by counting the number of colony-forming units of Candida albicans. The results were analyzed using a one-way ANOVA and Tukey's test (p = 0.05). The results of this study indicate that, despite the antimicrobial effect of zinc-bound phosphate-based glass, a coated denture-relining material does not degrade the surface properties and biocompatibility. Therefore, this novel material is considered promising for use as a dental material with antimicrobial properties that can potentially prevent denture stomatitis.

Zinc Oxide Nanoparticles: A Review on Its Applications in Dentistry

Nanotechnology in modern material science is a research hot spot due to its ability to provide novel applications in the field of dentistry. Zinc Oxide Nanoparticles (ZnO NPs) are metal oxide nanoparticles that open new opportunities for biomedical applications that range from diagnosis to treatment. The domains of these nanoparticles are wide and diverse and include the effects brought about due to the anti-microbial, regenerative, and mechanical properties. The applications include enhancing the anti-bacterial properties of existing restorative materials, as an anti-sensitivity agent in toothpastes, as an anti-microbial and anti-fungal agent against pathogenic oral microflora, as a dental implant coating, to improve the anti-fungal effect of denture bases in rehabilitative dentistry, remineralizing cervical dentinal lesions, increasing the stability of local drug delivery agents and other applications.

An overview of recent progress in dental applications of zinc oxide nanoparticles

Nanotechnology is an emerging field of science, engineering, and technology concerning the materials in nanoscale dimensions. Several materials are used in dentistry, which can be modified by applying nanotechnology. Nanotechnology has various applications in dentistry to achieve reliable treatment outcomes. The most common nanometals used in dental materials are gold, silver, copper oxide, magnesium oxide, iron oxide, cerium oxide, aluminum oxide, titanium dioxide, and zinc oxide (ZnO). ZnO nanoparticles (NPs), with their unparalleled properties such as high selectivity, enhanced cytotoxicity, biocompatibility, and easy synthesis as important materials were utilized in the field of dentistry. With this background, the present review aimed to discuss the current progress and gain an insight into applications of ZnO NPs in nanodentistry, including restorative, endodontic, implantology, periodontal, prosthodontics, and orthodontics fields.

Development of a Bioactive Flowable Resin Composite Containing a Zinc-Doped Phosphate-Based Glass

Flowable resins used for dental restoration are subject to biofilm formation. Zinc has antibacterial properties. Thus, we prepared a zinc-doped phosphate-based glass (Zn-PBG) to dope a flowable resin and evaluated the antibacterial activity of the composite against Streptococcus mutans (S. mutans) to extrapolate the preventative effect toward secondary caries. The composites were prepared having 0 (control), 1.9, 3.8, and 5.4 wt.% Zn-PBG. The flexural strength, elastic modulus, microhardness, depth of cure, ion release, inhibition zone size, and number of colony-forming units were evaluated and analyzed using ANOVA. The flexural strength of the control was significantly higher than those of Zn-PBG samples (p < 0.05). However, all samples meet the International Standard, ISO 4049. The microhardness was not significantly different for the control group and 1.9 and 3.8 wt.% groups, but the 5.4 wt.% Zn-PBG group had a significantly lower microhardness (p < 0.05). Further, the composite resins increasingly released P, Ca, Na, and Zn ions with an increase in Zn-PBG content (p < 0.05). The colony-forming unit count revealed a significant reduction in S. mutans viability (p < 0.05) with increase in Zn-PBG content. Therefore, the addition of Zn-PBG to flowable composite resins enhances antibacterial activity and could aid the prevention of secondary caries.

Chitosan capping of CuO nanoparticles: Facile chemical preparation, biological analysis, and applications in dentistry

This investigation is vital contribution to the healthcare system utilizing techniques of nanobiotechnology. It interestingly applies chitosan capped CuO nanoparticles in the field of medicine and restorative dentistry. The CuO nanoparticles and CuO-Chitosan nanoparticles are prepared by co-precipitation, and their characterization is performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The average crystallite size of these nanoparticles has been found to be in the dimensions of <40 nm and <35 nm, respectively. CuO-Chitosan nanoparticles show significant enhancement in in vitro antibacterial, antioxidant, cytotoxic, and antidiabetic activity as compared to CuO nanoparticles. In addition, the successful amalgamation of CuO nanoparticles and CuO-Chitosan nanoparticles into dentine bonding agents results in providing efficient remedy against secondary caries. CuO-Chitosan nanoparticles reinforced dental adhesive discs cause significant upsurge in reduction of Lactobacillus acidophillus and Streptococcus mutans. Also, the augmentation of mechanical properties, water sorption and solubility plus slow and sustained release profile and slight variation of shear bond strength is attained. Taken together, the chemically synthesized CuO nanoparticles and CuO-Chitosan nanoparticles have proven to be promising candidates having enormous potential to be utilized in drug delivery and nanotheranostics.

The effect of incorporation Nano Cinnamon powder on the shear bond of the orthodontic composite (an in vitro study)

Objectives

One of the causes of dental caries that occurs due to orthodontic treatment is the lack of antibacterial properties in orthodontic adhesive. This study was designated to investigate the effect of orthodontic resin modified by incorporating Nano Cinnamon powder on the shear bond strength of orthodontic brackets.

Materials and methods

Heliosit Orthodontic Resin, a photo-activated light cure resin was modified by the addition of Cinnamon in the form of Nano particle powder. Twenty uniform disks were made, 5 as a control and 5 for each concentration of the 1%, 3% and 5% wt/wt Cinnamon modified resin. Their antimicrobial activity against Streptococcus Mutans was tested using the disk diffusion method. Then, the most effective concentration of the modified resin was used to bond metal orthodontic brackets to human extracted premolars. The universal testing machine was used to record the shear bond strength of the control and the modified resin. Also, the adhesive remnant index was measured.

Results

Disc diffusion method showed that the 3% wt/wt Cinnamon powder modified resin was more effective than 1% with a larger bacterial inhibition zone. Shear bond strengths of the control were 8.50 MPa and 7.20 MPa for the 3% Cinnamon modified resin with no significant difference between them. Also, no significant difference was recorded in the adhesive remnant index scores between the control and the modified resin groups.

Conclusion

Findings of this study revealed that the incorporation of 3% Cinnamon Nano particles in orthodontic resin produced an antibacterial effect against Streptococcus mutans without compromising the shear bond strength.

Clinical relevance

Incorporation of Cinnamon Nano particles in orthodontic resin may reduce caries formation around brackets during treatment course.

Flexural strength, biocompatibility, and antimicrobial activity of a polymethyl methacrylate denture resin enhanced with graphene and silver nanoparticles

OBJECTIVE

The study evaluates the effect of adding graphene-Ag nanoparticles (G-AgNp) to a PMMA auto-polymerizing resin, with focus on antibacterial activity, cytotoxicity, monomer release, and mechanical properties.

MATERIALS AND METHODS

Auto-polymerizing acrylic resin (M) was loaded with 1 wt% G-AgNp (P1) and 2 wt% G-AgNp (P2). Methyl methacrylate monomer release (MMA) was measured after immersion of the samples in chloroform and cell medium respectively. Cell viability was assessed on dysplastic oral keratinocytes (DOK) and dental pulp stem cells. Oxidative stress and inflammatory response following exposure of dysplastic oral keratinocytes to the experimental resins was evaluated. Antibacterial activity against Staphylococcus aureus, Streptococcus mutans and Escherichia coli and also flexural strength of the resins were assessed.

RESULTS

Residual monomer: For samples immersed in chloroform, MMA concentration reached high levels, 10.27 μg/g for sample P1; MMA increased at higher G-AgNp loading; 0.63 μg/g MMA was found in medium for P1, and less for sample P2. Cell viability: Both cell lines displayed a viability decrease, but remained above 75%, compared to controls, when exposed to undiluted samples. Inflammation: proinflammatory molecule TNF-α decreased when DOK cultures were exposed to G-AgNp samples. MDA levels indicated increased oxidative stress damage in cells treated with PMMA, confirmed by the antioxidant mechanism activation, while samples containing G-AgNp induced an antioxidant effect. All tested samples showed antibacterial properties against Gram-positive bacteria. Samples containing G-AgNp also exhibited bactericide action on E. coli. Mechanical properties: both samples containing G-AgNp improved flexural strength compared to the sample resin, measured through elastic strength parameters.

CONCLUSIONS

PMMA resin loaded with G-AgNp presents promising antibacterial activity associated with minimal toxicity to human cells, in vitro, as well as improved flexural properties.

CLINICAL RELEVANCE

These encouraging results obtained in vitro support further in vivo investigation, to thoroughly check whether the PMMA loaded with graphene-silver nanoparticles constitute an improvement over current denture materials.

A systematic review on antibacterial activity of zinc against Streptococcus mutans

OBJECTIVES

The aim of this study was to systematically review the growth inhibition effectiveness of zinc against Streptococcus mutans. The main question was, "Does the zinc inhibit the growth of oral Streptococcus mutans in vitro?

METHODS

Literature search on PubMed, Medline, and science direct databases was carried out for in vitro studies published in English from 1990 to 2016, and the reported outcomes of minimum inhibitory concentration (MIC), minimum bactericidal concentrations (MBC), zone of inhibition (ZOI) and bacterial count method using colony forming unit (CFU) were used to assess the antibacterial effectiveness of zinc.

RESULTS

Seventeen studies were included in this review. Seven studies reported MIC and MBC. Four studies reported ZOI, and eight studies reported CFU. MIC values using zinc chloride and zinc oxide nanoparticles were ranged from 0.025 to 0.2 mM and 0.390 to 500 ± 306.18 µg/ml respectively. MBC values using zinc oxide nanoparticles have ranged from 3.125 to 500 µg/ml. ZOI ranged from no inhibition zone to 21 ± 1.4 mm using 23.1% zinc oxide. A considerable reduction in the bacterial count was reported after adding zinc. However, only two studies have reported no inhibitory effect of zinc.

CONCLUSION

This review indicated a significant growth inhibition effectiveness of zinc even at lower concentrations which indicate it's safely to be used in oral health products.

Comparative evaluation and influence on shear bond strength of incorporating silver, zinc oxide, and titanium dioxide nanoparticles in orthodontic adhesive

OBJECTIVE

To investigate the influence of silver (Ag), zinc oxide (ZnO), and titanium dioxide (TiO₂) nanoparticles on shear bond strength (SBS).

MATERIALS AND METHODS

One hundred and twenty extracted premolars divided into four groups with thirty specimens in each group. Group 1 (control): brackets (American Orthodontics) were bonded with Transbond XT primer. Groups 2, 3, and 4: brackets (American Orthodontics) were bonded with adhesives incorporated with Ag, ZnO, and TiO₂ nanoparticles in the concentration of 1.0% nanoparticles of Ag, 1.0% TiO₂, and 1.0% ZnO weight/weight, respectively. An Instron universal testing machine AGS-10k NG (SHIMADZU) was used to measure the SBS. The data were analyzed by SPSS software and then, the normal distribution of the data was confirmed by Kolmogorov-Smirnov test. One-way ANOVA test and Tukey's multiple post hoc procedures were used to compare between groups. In all statistical tests, the significance level was set at 5% (P < 0.05).

RESULTS

A significant difference was observed between control (mean [standard deviation (SD)] 9.43 [3.03], confidence interval [CI]: 8.30-10.56), Ag (mean [SD]: 7.55 [1.29], CI: 7.07-8.03), ZnO (mean [SD]: 6.50 [1.15], CI: 6.07-6.93), and TiO₂ (mean [SD]: 6.33 [1.51], CI: 5.77-0.89) with SBS (F = 16.8453, P < 0.05) at 5% level of significance.

CONCLUSION

Incorporation of various nanoparticles into adhesive materials in minimal amounts may decrease SBS and may lead to the failure of bracket or adhesive. The limitation of this study is that it is an in vitro research and these results may not be comparable to what the expected bond strengths observed in vivo. Further clinical studies are needed to evaluate biological effects of adding such amounts of nanoparticles and approve such adhesives as clinically sustainable.