Nanomaterials in dentistry: a cornerstone or a black box?

Noninvasive assessment of novel nanohybrid resin cement adaptation using cross-polarization optical coherence tomography

OBJECTIVES

Zein-coated magnesium oxide nanoparticles (zMgO NPs) can potentially improve cement adaptation to the tooth-restoration interface, which would aid in minimizing marginal leakage and secondary caries. The aim of this study was to assess the effect of incorporating zMgO NPs on the adaptation of self-adhesive resin cement using cross-polarization optical coherence tomography (CP-OCT) and scanning electron microscopy (SEM).

METHODS

Resin inlays were fabricated to be cemented in Class-I cavities of extracted human molars. All specimens were randomly divided into five groups (n = 10), and the resin inlays were cemented using self-adhesive resin cement with various concentrations of zMgO NPs (0% [control], 0.3%, 0.5%, 1%, 2%). Characterization was done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and SEM. The specimens were examined for interfacial adaptation under CP-OCT. Floor and wall adaptation measurements were analyzed by software on 20 B-scans, and samples were sectioned for interfacial measurement by SEM.

RESULTS

Results for CP-OCT and SEM showed a statistically significant increase of adaptation in the floor and wall of resin cement filled with zMgO NPs compared to the control. The samples enhanced with 0.3% and 0.5% showed a statistically significantly better adaptation in floor and wall in CP-OCT and SEM. However, there was no significant difference between the 1%, 2%, and control groups for CP-OCT and SEM analysis.

SIGNIFICANCE

The incorporation of zMgO NPs in self-adhesive resin cement can enhance the cement's properties by significantly improving its wall and floor adaptation.

Influence of inorganic nanoparticles on dental materials' mechanical properties. A narrative review

Inorganic nanoparticles have been widely incorporated in conventional dental materials to help in improving their properties. The literature has shown that incorporating nanoparticles in dental materials in different specialties could have a positive effect on reinforcing the mechanical properties of those materials; however, there was no consensus on the effectiveness of using nanoparticles in enhancing the mechanical properties of dental materials, due to the variety of the properties of nanoparticles itself and their effect on the mechanical properties. This article attempted to analytically review all the studies that assessed the effect of different types of inorganic nanoparticles on the most commonly used dental materials in dental specialties such as polymethyl methacrylate, glass ionomer cement, resin composite, resin adhesive, orthodontic adhesive, and endodontic sealer. The results had shown that those inorganic nanoparticles demonstrated positive potential in improving those mechanical properties in most of the dental materials studied. That potential was attributed to the ultra-small sizes and unique physical and chemical qualities that those inorganic nanoparticles possess, together with the significant surface area to volume ratio. It was concluded from this comprehensive analysis that while a definitive recommendation cannot be provided due to the variety of nanoparticle types, shapes, and incorporated dental material, the consensus suggests using nanoparticles in low concentrations less than 1% by weight along with a silane coupling agent to minimize agglomeration issues and benefit from their properties.

Effect of dental composite dust on human gingival keratinocytes

OBJECTIVE

The aim was to investigate the effect of particles released during grinding of dental composites on human gingival keratinocytes (HGK).

METHODS

Specimens from Filtek™ Supreme XTE and ceram.x® universal were prepared and ground to dust. The dust was filtered (≤ 5 µm) and the particle size distribution was examined using NANO-flex®-180° dynamic light scattering (DLS). Suspensions at five concentrations (3, 10, 30, 100 and 300 µg/mL) were prepared using keratinocyte growth medium (KGM). These suspensions, as well as a positive (CuO) and a negative control (KGM) were added to HGK. The cells treated with Filtek™ Supreme XTE suspensions were analyzed by real-time monitoring using RTCA iCELLigence™. In addition, light and scanning electron microscopic images of the exposed cells were taken. Indirect immunofluorescence staining was performed to detect the extracellular matrix protein fibronectin.

RESULTS

In distilled water, DLS showed similar particles' range (171.9 nm- 2.7 µm) for both composites. In saliva, larger particles were detected (Filtek™ Supreme XTE: 243 nm-6,5 µm; ceram.x® universal: 204 nm- 4,6 µm). iCELLigence™ revealed similar results of cell growth parameters for HGK incubated with composite dust (≤ 5 µm) at different concentrations. The microscopic images indicated unaltered cell structures and formation of large agglomerates with high particle concentration (> 100 µg/mL). Exposure to composite dust resulted in upregulation of fibronectin expression.

SIGNIFICANCE

Grinding of dental composite materials generates dust particles of different sizes. The particle size distribution seems to be more influenced by the suspending medium than the material itself. While cell growth of HGK seem not to be affected by the particles, an upregulation of fibronectin in the intercellular space concomitant by increasing particle concentration may indicate an increase of cell migration/mobility.

Color behavior of composite resin enhanced with different shapes of new antimicrobial polymer coated nanoparticles

BACKGROUND

Zein-coated magnesium oxide nanoparticles (zMgO NPs) demonstrate a potent antimicrobial effect, endorsing it as a compelling additive to dental materials formulations for oral health care advances. However, currently there is no data on the imprint of zMgO NPs on the color permanence of dental composites. The objective of this study is to evaluate the color stability of different types of composite enhanced with antimicrobial zein-coated magnesium oxide nanoparticles (zMgO NPs) of different shapes before and after thermocycling.

METHODS

Two hundred composite samples were divided into four groups: Gp1: Tetric N-Flow with zMgO nanowires, Gp2: Tetric N-Flow with zMgO nanospheres, Gp3: Tetric N-Ceram with zMgO nanowires; Gp4: Tetric N-Ceram with zMgO nanospheres. Each group was subdivided into 5 subgroups (n = 10) with concentrations of zMgO NPs 0%, 0.3%, 0.5%, 1% and 2%. The characterization of the modified composite containing the zMgO was done via X-ray Diffraction, Field Emission Scanning Electron Microscopy (FESEM), and Fourier Transform Infrared Spectroscopy (FTIR). Colorimetric evaluation was performed through spectrophotometry with a white background. Samples underwent color assessment using a spectrophotometer, followed by thermocycling, and then another color assessment.

RESULTS

FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the composite and FTIR illustrated no change in the spectra. However, the XRD spectra exhibited an amorphous pattern in the composite enhanced with zMgO NPs. There was no compelling discrepancy in color variation ΔE among the different groups before and after thermocycling (p > 0.05). A statistically notable variation in ΔL was found amid the control and N-Flow and N-Ceram with 2% zMgO nanospheres before and after thermocycling respectively (p < 0.05). While after thermocycling, there was a statistically significant difference in Δa in N-Flow and N-Ceram wires amid the control and the different groups (p < 0.05). Additionally, after thermocycling there was a statistically significant difference in Δb in N-Flow and N-Ceram wires between the control and the different groups (p < 0.05). The Tukey test exhibited no variation among the groups with different zMgO concentrations (p > 0.05).

CONCLUSION

Enhancing N-Flow and N-Ceram composite with antimicrobial zMgO nanowires and nanospheres did not alter the total color stability of the materials before and after thermocycling.

Hazards Associated With Nanotechnology in Clinical Dentistry

Nanotechnology has transformed the field of dentistry with immense potential to provide comprehensive oral health care using nanomaterials, advanced clinical tools, and devices. New materials with superior properties can be developed using nanotechnology by making use of their atomic or molecular properties. Although there are numerous ways in which nanomaterials impact our health, the primary cause is that they comprise chemicals that may have an inadvertent reaction in the body. Moreover, they are used on a daily basis, increasing human contact with them. It is observed to be smaller in size than the physiological barrier in our bodies, making it much simpler for them to pass through and enter the body and they are being used more frequently. It is observed to be smaller in size than the physiological barrier in our bodies, making it much simpler for them to pass through and enter the body and being used more frequently. Although there are numerous ways in which nanomaterials impact our health, the primary cause is they comprise chemicals that may have an inadvertent reaction in the body. The review discusses various types of toxicity, including the cytotoxicity of composites, carbon nanoparticles, silver nanoparticles (SNPs), and quantum dots. It also covers genotoxicity, the effect of nanoparticles on salivary secretion, oral and gastrointestinal mucosa passage of nanoparticles, the tooth surface microenvironment, and interactions with engineered nanomaterials (ENMs). It is concluded that there is scarce information regarding the presence of chemicals that are released from nanoparticles used in dental materials. Nanotechnology is at an infant stage, although it has progressed by leaps and bounds, hailing a new age that provides better treatment modalities in various branches of dentistry. Although the development and application of nanodentistry are of considerable interest, knowledge regarding the possible toxicity of such materials must be meticulously evaluated, and potential benefits must be weighed against the risks to identify potential gaps in the safety assessment. Further research is needed on workplace exposure to nanoparticles in dentistry.

Effects of Bio-Aging on Mechanical Properties and Microbial Behavior of Different Resin Composites

Under challenging oral environments, the overall performance of resin composites is affected by bio-aging. This study investigated the effects of saliva biofilm-induced bio-aging on the mechanical properties and microbial behavior of composites with different filler types. Microhybrid, nanohybrid, nano-filled and nano-filled flowable composites were bio-aged with saliva biofilm for 30 days. Surface morphology, roughness, mechanical and aesthetic properties were determined. A 48 h saliva biofilm model was used to evaluate the microbial behavior of different composites in vitro. Biofilm metabolic activity, lactic acid production and live/dead bacterial staining were tested. Six volunteers were selected to wear intra-oral appliances with composite slabs for 24 h and biofilms were collected and analyzed using 16S rRNA sequencing to assess the biofilm formation over those materials in situ. Although there were increasing trends, surface roughness, water resorption and material solubility had no significant changes for all groups after bio-aging (p > 0.05). There were no significant changes in elastic modulus for all groups after aging (p > 0.05). However, a decrease in flexural strength in all groups was observed (p < 0.05), except for the nanoflow composite group (p > 0.05). The Vickers hardness remained stable in all groups after aging (p > 0.05), except for the nano-filled group (p < 0.05). The nanoflow composite showed distinct color changes compared to the micro-hybrid group after aging (p < 0.05). Biofilm metabolic activity and lactic acid production in vitro increased slightly after bio-aging in all groups, but with no statistical significance (p > 0.05). The Shannon index diversity of biofilms in situ decreased after aging (p < 0.05), while no significant difference was shown in species composition at the genus level in all groups (p > 0.05). Resin composites with different sized fillers displayed a relatively stable mechanical performance and uncompromised microbial behavior both in vitro and in situ after 30 days of bio-aging. Based on the results, composites with different filler types can be selected flexibly according to clinical needs. However, a longer time for bio-aging is still needed to confirm the mechanical properties and microbial behaviors of composites in the long run.

Craniofacial therapy: advanced local therapies from nano-engineered titanium implants to treat craniofacial conditions

Nano-engineering-based tissue regeneration and local therapeutic delivery strategies show significant potential to reduce the health and economic burden associated with craniofacial defects, including traumas and tumours. Critical to the success of such nano-engineered non-resorbable craniofacial implants include load-bearing functioning and survival in complex local trauma conditions. Further, race to invade between multiple cells and pathogens is an important criterion that dictates the fate of the implant. In this pioneering review, we compare the therapeutic efficacy of nano-engineered titanium-based craniofacial implants towards maximised local therapy addressing bone formation/resorption, soft-tissue integration, bacterial infection and cancers/tumours. We present the various strategies to engineer titanium-based craniofacial implants in the macro-, micro- and nano-scales, using topographical, chemical, electrochemical, biological and therapeutic modifications. A particular focus is electrochemically anodised titanium implants with controlled nanotopographies that enable tailored and enhanced bioactivity and local therapeutic release. Next, we review the clinical translation challenges associated with such implants. This review will inform the readers of the latest developments and challenges related to therapeutic nano-engineered craniofacial implants.

Applications of Nanomaterials in Dentistry: A Review

Aim and Objective

Currently, the major priority in the field of nanotechnology or nanoscience is research and development at the atomic- or molecular-level sciences. Almost every aspects of human health, including pharmaceutical, clinical research and analysis, and supplemental immunological systems, are significantly impacted by it. Diverse dental applications to the realm of nanotechnology, which also reflect developments in material sciences, have given rise to the field of nanodentistry and nanocatalytic drug development, especially in oral nanozyme research and application. This review is aimed to provide readers an in-depth analysis of nanotechnology's characteristics, varied qualities, and applications toward dentistry.

Materials and Methods

A query was carried out in PubMed and Google Scholar databases for the articles published from 2007 to 2022 using the keywords/MESH term nanomaterials, dentistry, nanoenzymes, metals, and antibacterial activity. Data extraction and evidence synthesis have been performed by three researchers individually.

Results

A total of 901 articles have been extracted, out of which 108 have been removed due to repetitions and overlapping. After further screening following exclusion and inclusion criteria, 74 papers were considered to be pertinent and that primarily addressed dental nanotechnology were chosen. Further, the data havebeen extracted and interpreted for the review. The results of the review indicated that the development of multifunctional nanozymes has been continuously assessed in relation to oro-dental illnesses to show the significant impact that nanozymes have on oral health.

Conclusion

As evidenced by the obtained results, with the advent of ongoing breakthroughs in nanotechnology, dental care could be improved with advanced preventive measures.

Tests of Dental Properties of Composite Materials Containing Nanohybrid Filler

Complex composite materials are used in many areas of dentistry. Initially, chemically hardened materials were also used, and in this group nanohybrid composites are highly valued. They are often used today, mainly for the direct reconstruction of damaged hard tooth tissue materials for rebuilding damaged tissues using indirect adhesive techniques. The research was conducted to determine the mechanical properties of materials with nanofillers. The article focuses on methods of important test methods for dental prosthetics: resilience, abrasion, wear test, impact strength, hardness, SEM, and chemical analysis. As part of this work, five different series of hybrid composites with nano-fillers were tested. The mechanical properties of composites, such as compressive strength, microhardness, flexural strength, and modulus of elasticity, depend mainly on the type, particle size, and amount of filler introduced. The obtained test results showed that the type and amount of nanofiller have a significant influence on the mechanical and tribological properties. The introduction of nanofillers allowed us to obtain higher mechanical properties compared to classic materials discussed by other researchers. The study observed a change in vibrations in the IR spectrum, which allowed a comparison of the organic structures of the studied preparations.

Noninvasive Adaptation Appraisal of Antimicrobial Nano-Filled Composite

OBJECTIVE

The aim of this research was to assess the effect of incorporating zein-coated magnesium oxide (zMgO) nanofillers to resin-based composite on the internal adaptation of the restorations using cross-polarisation optical coherence tomography (CP-OCT).

METHODS

Thirty noncarious human molar teeth were used. Class V cavities (3 × 5 mm) were prepared on the buccal and lingual surfaces of each tooth. Clearfil SE Bond 2 was applied to all the cavities and then the teeth were divided into 3 groups (n = 10) as follows: group 1-restored with N-Flow composite; group 2 and group 3-restored with N-Flow composite mixed with different zMgO nanoparticle concentrations (0.3% and 0.5% by weight, respectively) and then light cured using an LED curing device. Specimens were examined for interfacial adaptation examination under CP-OCT. Characterisation of the dental composite incorporating zMgO was done by Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Results were analysed with Kruskall-Wallis test followed by Mann-Whitney U test, at a significance level of P < .05.

RESULTS

XRD spectra exhibited the sharp peaks of zMgO in the composite enhanced with zMgO nanoparticles. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the composite and FTIR illustrated no change in the spectra. The gap percentage along the cavity floor was significantly lower in groups 2 and 3 in comparison to group 1 (P < .05). Also there was a significant difference in gap percentages between groups 2 and 3 (P < .05), with group 3 showing the lowest gap percentage.

CONCLUSIONS

The incorporation of 0.3% and 0.5% zMgO nanoparticles in flowable composite assists in improving the internal adaptation of the composite to the tooth surface.

TiO2 nanotube-containing glass ionomer cements display reduced aluminum release rates

Titanium dioxide nanotubes (TiO2-nts) were incorporated into a glass ionomer cement (GIC) with improved mechanical properties and antibacterial activity. The aims of the present in vitro study were to define the elemental characterization, aluminum (Al) release rate, and initial working time for GIC reinforced with TiO2-nts, in an experimental caries model. TiO2-nts were incorporated into GIC powder components at 5% by weight, and compared with unblended GIC. Experimental approaches used energy-dispersive spectrometry (EDS), atomic absorption spectrophotometry (AAS), and brightness loss to define surface element properties, Al release rates, and initial working time, respectively. Statistical analysis was performed by 2-way ANOVA, Tukey's test, generalized linear models, and Student's t test (a = 0.05). EDS data analysis revealed that TiO2-nts incorporated into GIC had no significant impact on the typical elemental composition of GICs in an in vitro caries model. Regarding the demineralizing solution, GIC with TiO2-nt significantly decreased the Al release rate, compared with the control group (p < 0.0001). Moreover, TiO2-nt incorporated into GIC did not alter the initial working time of the material (p > 0.05). These findings add information to our scientific body of knowledge concerning the potential impact of TiO2-nt on the performance of conventional GICs.

Nanomaterials in Dentistry: Current Applications and Future Scope

Nanotechnology utilizes the mechanics to control the size and morphology of the particles in the required nano range for accomplishing the intended purposes. There was a time when it was predominantly applied only to the fields of matter physics or chemical engineering, but with time, biological scientists recognized its vast benefits and explored the advantages in their respective fields. This extension of nanotechnology in the field of dentistry is termed ‘Nanodentistry.’ It is revolutionizing every aspect of dentistry. It consists of therapeutic and diagnostic tools and supportive aids to maintain oral hygiene with the help of nanomaterials. Research in nanodentistry is evolving holistically but slowly with the advanced finding of symbiotic use of novel polymers, natural polymers, metals, minerals, and drugs. These materials, in association with nanotechnology, further assist in exploring the usage of nano dental adducts in prosthodontic, regeneration, orthodontic, etc. Moreover, drug release cargo abilities of the nano dental adduct provide an extra edge to dentistry over their conventional counterparts. Nano dentistry has expanded to every single branch of dentistry. In the present review, we will present a holistic view of the recent advances in the field of nanodentistry. The later part of the review compiled the ethical and regulatory challenges in the commercialization of the nanodentistry. This review tracks the advancement in nano dentistry in different but important domains of dentistry.

Dental Implant Healing Screws as Temporary Oral Drug Delivery Systems for Decrease of Infections in the Area of the Head and Neck

Background

Periimplantitis is continuously one of major threats for the uneventful functioning of dental implants. Current approaches of drug delivery systems are being more commonly implemented into oral- and maxillofacial biomaterials in order to decrease the risk of implant failure due to bacterial infection. Silver nanoparticles and their compounds have been proven in eradicating oral bacteria responsible for peri-implant infections. Nevertheless, their evaluation as coating for implant abutments has not been extensively evaluated so far. This article describes a novel coating consisting of zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs). This coating was used to modify healing abutments that could be used as drug delivery systems in oral implantology.

Materials and Method

Nanoparticles with a ZnO + 0.1% Ag composition were produced by microwave solvothermal synthesis and then incorporated into the surface of titanium healing abutments by high-power ultrasonic deposition. Surface morphology, roughness, wettability were evaluated. Ability of biofilm formation inhibition was tested against S. mutans, S. oralis, S. aureus and E. coli.

Results

ZnO+0.1%Ag NPs were sufficiently deposed on the surface of the abutments creating nanostructured coating which increased surface roughness and decreased wettability. Modified abutments significantly decreased bacterial biofilm formation. Bacteria present in SEM studies were unlikely to settle and replicate on the experimental abutments as their cells were rounded, insufficiently spread on the surface and covered with released NPs.

Conclusion

Experimental nanostructured abutments were easily manufactured by high-power ultrasonic deposition and provided significant antibacterial properties. Such biomaterials could be used as temporary drug delivery abutments for prevention and treatment of intra- and extraoral peri-implant infections in the area of the head and neck.

Role of Nanoparticles in Environmental Remediation: An Insight into Heavy Metal Pollution from Dentistry

Environmental damage is without a doubt one of the most serious issues confronting society today. As dental professionals, we must recognize that some of the procedures and techniques we have been using may pose environmental risks. The usage and discharge of heavy metals from dental set-ups pollute the environment and pose a serious threat to the ecosystem. Due to the exclusive properties of nanosized particles, nanotechnology is a booming field that is being extensively studied for the remediation of pollutants. Given that the nanoparticles have a high surface area to volume ratio and significantly greater reactivity, they have been greatly considered for environmental remediation. This review aims at identifying the heavy metal sources and their environmental impact in dentistry and provides insights into the usage of nanoparticles in environmental remediation. Although the literature on various functions of inorganic nanoparticles in environmental remediation was reviewed, the research is still confined to laboratory set-ups and there is a need for more studies on the usage of nanoparticles in environmental remediation.

Current and Advanced Nanomaterials in Dentistry as Regeneration Agents: An Update

In modern dentistry, nanomaterials have strengthened their foothold among tissue engineering strategies for treating bone and dental defects due to a variety of reasons, including trauma and tumors. Besides their finest physiochemical features, the biomimetic characteristics of nanomaterials promote cell growth and stimulate tissue regeneration. The single units of these chemical substances are small-sized particles, usually between 1 to 100 nm, in an unbound state. This unbound state allows particles to constitute aggregates with one or more external dimensions and provide a high surface area. Nanomaterials have brought advances in regenerative dentistry from the laboratory to clinical practice. They are particularly used for creating novel biomimetic nanostructures for cell regeneration, targeted treatment, diagnostics, imaging, and the production of dental materials. In regenerative dentistry, nanostructured matrices and scaffolds help control cell differentiation better. Nanomaterials recapitulate the natural dental architecture and structure and form functional tissues better compared to the conventional autologous and allogenic tissues or alloplastic materials. The reason is that novel nanostructures provide an improved platform for supporting and regulating cell proliferation, differentiation, and migration. In restorative dentistry, nanomaterials are widely used in constructing nanocomposite resins, bonding agents, endodontic sealants, coating materials, and bioceramics. They are also used for making daily dental hygiene products such as mouth rinses. The present article classifies nanostructures and nanocarriers in addition to reviewing their design and applications for bone and dental regeneration.

Emerging nanomaterials for dental treatments

The emergence of nanomaterials for dental treatments is encouraged by the nanotopography of the tooth structure, together with the promising benefits of nanomedicine. The use of nanoparticles in dentistry, also termed as 'nanodentistry', has manifested in applications for remineralisation, antimicrobial activity, local anaesthesia, anti-inflammation, osteoconductivity and stem cell differentiation. Besides the applications on dental tissues, nanoparticles have been used to enhance the mechanical properties of dental composites, improving their bonding and anchorage and reducing friction. The small particle size allows for enhanced permeation into deeper lesions, and reduction in porosities of dental composites for higher mechanical strength. The large surface area to volume ratio allows for enhanced bioactivity such as bonding and integration, and more intense action towards microorganisms. Controlled release of encapsulated bioactive molecules such as drugs and growth factors enables them to be delivered more precisely, with site-targeted delivery for localised treatments. These properties have benefitted across multiple fields within dentistry, including periodontology and endodontics and reengineering of dental prosthetics and braces. This review summarises the current literature on the emerging field of nanomaterials for dental treatments.

Efficient non-contact heat generation on flexible, ternary hydroxyapatite/curdlan/nanomagnetite hybrids for temperature controlled processes

The ternary HAp/curdlan/nanomagnetite hybrids with ceramic and polymer phase incorporation of magnetite nanoparticles (MNPs) were fabricated to study their heating ability under action of the alternating magnetic field (AMF), 808 nm near infrared laser radiation (NIR) and their synergic stimulation. The energy conversion was evaluated in terms of the specific absorption rate (SAR) as a function of the MNPs concentration in composites and to estimate their potential in temperature-controlled regenerative processes and hyperthermia. Measurements were carried out on dry and Ringer's solution soaked composite materials in order to mimic in situ conditions. It was found that the MNPs release during prolonged experiment is limited and has no significant effect on energy conversion emphasizing stability of the hybrids. Incorporation of the MNPs in polymer phase of the hybrid can additionally limit particle leaking as well as plays a role as insulating layer for the heat dissipation lowering the risk of sample overheating. In general, it was shown that maximum temperature of hybrid can be achieved in a relatively short time of exposure to stimulating factors whereas its control can be done through optimization of experiment conditions. MNPs incorporation into the curdlan (polymer phase) lead to strengthening of the mechanical properties of the whole network.

Application of Nanotechnology in Orthodontic Materials: A State-of-the-Art Review

Nanotechnology refers to the science that manipulates matter at molecular and atomic levels, and studies matter at the nanoscale level to detect and exploit the useful properties that derive from these dimensions; materials with components less than 100 nm in at least one dimension are called nanomaterials. Nanotechnology is applied in many fields, such as medicine (nanomedicine) and dentistry (nano-dentistry). The purpose of these innovations and research in this field is to improve human life and health. This article aims to summarize and describe what the most recent and known innovations of nanotechnology in dentistry are, focusing on and paying particular attention to the branch that is orthodontics, and on the application of new nanomaterials in the realization, for example, of orthodontic elastomeric ligatures, orthodontic power chains, and orthodontic miniscrews. We also address a very important topic in orthodontics, which is how to reduce the friction force.

Effect of Fiber Posts on Stress Distribution of Endodontically Treated Upper Premolars: Finite Element Analysis

By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial–occlusal–distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal–palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin.

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphoslogies

Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO NMs) more popular in numerous consumer products. In recent years, particular attention has been drawn to the development of various methods of ZnO NMs synthesis, which above all meet the requirements of the green chemistry approach. The application of the microwave heating technology when obtaining ZnO NMs enables the development of new methods of syntheses, which are characterised by, among others, the possibility to control the properties, repeatability, reproducibility, short synthesis duration, low price, purity, and fulfilment of the eco-friendly approach criterion. The dynamic development of materials engineering is the reason why it is necessary to obtain ZnO NMs with strictly defined properties. The present review aims to discuss the state of the art regarding the microwave synthesis of undoped and doped ZnO NMs. The first part of the review presents the properties of ZnO and new applications of ZnO NMs. Subsequently, the properties of microwave heating are discussed and compared with conventional heating and areas of application are presented. The final part of the paper presents reactants, parameters of processes, and the morphology of products, with a division of the microwave synthesis of ZnO NMs into three primary groups, namely hydrothermal, solvothermal, and hybrid methods.

Applications of nano-materials in diverse dentistry regimes

Research and development in the applied sciences at the atomic or molecular level is the order of the day under the domain of nanotechnology or nano-science with enormous influence on nearly all areas of human health and activities comprising diverse medical fields such as pharmacological studies, clinical diagnoses, and supplementary immune system. The field of nano-dentistry has emerged due to the assorted dental applications of nano-technology. This review provides a brief introduction to the general nanotechnology field and a comprehensive overview of the synthesis features and dental uses of nano-materials including current innovations and future expectations with general comments on the latest advancements in the mechanisms and the most significant toxicological dimensions.

Nanoparticles And Human Saliva: A Step Towards Drug Delivery Systems For Dental And Craniofacial Biomaterials

Aim

The aims of this study were to investigate new nano-formulations based on ZnO and Ag nanoparticle (NP) compounds when used against clinical strains of oral gram-positive and gram-negative bacteria, and to examine the stability and behaviour of nano-formulation mixtures in saliva based on different compositions of Ag NPs, ZnO NPs and ZnO+x·Ag NPs. Methods: ZnO NPs with and without nanosilver were obtained by microwave solvothermal synthesis. Then, antibacterial activity was evaluated against bacteria isolated from human saliva. Behavior and nanoparticle solutions were evaluated in human saliva and control (artificial saliva and deionized water). Results were statistically compared.

Results

The NP mixtures had an average size of 30±3 nm, while the commercial Ag NPs had an average size of 55±5 nm. The suspensions displayed differing antibacterial activities and kinetics of destabilisation processes, depending on NPs composition and fluid types.

Conclusion

The present study showed that all NPs suspensions displayed significant destabilisation and high destabilisation over the 24 h of the analyses. The agglomeration processes of NPs in human saliva can be reversible.

Polymer Membranes Sonocoated and Electrosprayed with Nano-Hydroxyapatite for Periodontal Tissues Regeneration

Diseases of periodontal tissues are a considerable clinical problem, connected with inflammatory processes and bone loss. The healing process often requires reconstruction of lost bone in the periodontal area. For that purpose, various membranes are used to prevent ingrowth of epithelium in the tissue defect and enhance bone regeneration. Currently-used membranes are mainly non-resorbable or are derived from animal tissues. Thus, there is an urgent need for non-animal-derived bioresorbable membranes with tuned resorption rates and porosity optimized for the circulation of body nutrients. We demonstrate membranes produced by the electrospinning of biodegradable polymers (PDLLA/PLGA) coated with nanohydroxyapatite (nHA). The nHA coating was made using two methods: sonocoating and electrospraying of nHA suspensions. In a simulated degradation study, for electrosprayed membranes, short-term calcium release was observed, followed by hydrolytic degradation. Sonocoating produced a well-adhering nHA layer with full coverage of the fibers. The layer slowed the polymer degradation and increased the membrane wettability. Due to gradual release of calcium ions the degradation-associated acidity of the polymer was neutralized. The sonocoated membranes exhibited good cellular metabolic activity responses against MG-63 and BJ cells. The collected results suggest their potential use in Guided Tissue Regeneration (GTR) and Guided Bone Regeneration (GBR) periodontal procedures.

Zinc Oxide Nanoparticles Cytotoxicity and Release from Newly Formed PMMA-ZnO Nanocomposites Designed for Denture Bases

The goal of the study was to investigate the level of zinc oxide nanoparticles (ZnO NPs) release from polymethyl methacrylate (PMMA)-ZnO nanocomposites (2.5%, 5%, and 7.5% w/w), as well as from the ZnO NPs layer produced on pure PMMA, and the impact of the achieved final ZnO NPs concentration on cytotoxicity, before the potential use as an alternative material for denture bases. The concentration of ZnO nanoparticles released to the aqueous solution of Zn²⁺ ions was assessed using optical emission spectrometry with inductively coupled plasma (ICP-OES). In the control group (pure PMMA), the released mean for ZnO was 0.074 mg/L and for individual nanocomposites at concentrations of 2.5%, 5%, and 7.5% was 2.281 mg/L, 2.143 mg/L, and 3.512 mg/L, respectively. The median for the ZnO NPs layer produced on PMMA was 4.878 mg/L. In addition, in vitro cytotoxicity of ZnO NPs against the human HeLa cell line was determined through the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) dye. The cytotoxicity studies demonstrate that ZnO nanoparticles in the concentrations up to 20 mg/L have no adverse effect on HeLa cells. When compared with the released and cytotoxic concentrations of ZnO NPs, it can be expected that ZnO released from dental prostheses to the oral cavity environment will have no cytotoxic effect on host cells.

Nanoparticle Size Effect on Water Vapour Adsorption by Hydroxyapatite

Handling and properties of nanoparticles strongly depend on processes that take place on their surface. Specific surface area and adsorption capacity strongly increase as the nanoparticle size decreases. A crucial factor is adsorption of water from ambient atmosphere. Considering the ever-growing number of hydroxyapatite nanoparticles applications, we decided to investigate how the size of nanoparticles and the changes in relative air humidity affect adsorption of water on their surface. Hydroxyapatite nanoparticles of two sizes: 10 and 40 nm, were tested. It was found that the nanoparticle size has a strong effect on the kinetics and efficiency of water adsorption. For the same value of water activity, the quantity of water adsorbed on the surface of 10 nm nano-hydroxyapatite was five times greater than that adsorbed on the 40 nm. Based on the adsorption isotherm fitting method, it was found that a multilayer physical adsorption mechanism was active. The number of adsorbed water layers at constant humidity strongly depends on particles size and reaches even 23 layers for the 10 nm particles. The amount of water adsorbed on these particles was surprisingly high, comparable to the amount of water absorbed by the commonly used moisture-sorbent silica gel.

Zein/gelatin/nanohydroxyapatite nanofibrous scaffolds are biocompatible and promote osteogenic differentiation of human periodontal ligament stem cells

In bone tissue engineering, it is important for biomaterials to promote the osteogenic differentiation of stem cells to achieve tissue regeneration.

Structural and Magnetic Properties of Co‒Mn Codoped ZnO Nanoparticles Obtained by Microwave Solvothermal Synthesis

Zinc oxide nanoparticles codoped with Co2+ and Mn2+ ions (Zn(1−x−y)MnxCoyO NPs) were obtained for the first time by microwave solvothermal synthesis. The nominal content of Co2+ and Mn2+ in Zn(1−x−y)MnxCoyO NPs was x = y = 0, 1, 5, 10 and 15 mol % (the amount of both ions was equal). The precursors were obtained by dissolving zinc acetate dihydrate, manganese (II) acetate tetrahydrate and cobalt (II) acetate tetrahydrate in ethylene glycol. The morphology, phase purity, lattice parameters, dopants content, skeleton density, specific surface area, average particle size, average crystallite size, crystallite size distribution and magnetic properties of NPs were determined. The real content of dopants was up to 25.0% for Mn2+ and 80.5% for Co2+ of the nominal content. The colour of the samples changed from white to dark olive green in line with the increasing doping level. Uniform spherical NPs with wurtzite structure were obtained. The average size of NPs decreased from 29 nm to 21 nm in line with the increase in the dopant content. Brillouin type paramagnetism and an antiferromagnetic interaction between the magnetic ions was found for all samples, except for that with 15 mol % doping level, where a small ferromagnetic contribution was found. A review of the preparation methods of Co2+ and Mn2+ codoped ZnO is presented.

Effect of Microwave Radiation Power on the Size of Aggregates of ZnO NPs Prepared Using Microwave Solvothermal Synthesis

This paper reports the possibility of changing the size of zinc oxide nanoparticles (ZnO NPs) aggregates through a change of synthesis parameters. The effect of the changed power of microwave heating on the properties of ZnO NPs obtained by the microwave solvothermal synthesis from zinc acetate dissolved in ethylene glycol was tested for the first time. It was found that the size of ZnO aggregates ranged from 60 to 120 nm depending on the power of microwave radiation used in the synthesis of ZnO NPs. The increase in the microwave radiation power resulted in the reduction of the total synthesis time with simultaneous preservation of the constant size and shape of single ZnO NPs, which were synthesized at a pressure of 4 bar. All the obtained ZnO NPs samples were composed of homogeneous spherical particles that were single crystals with an average size of 27 ± 3 nm with a developed specific surface area of 40 m²/g and the skeleton density of 5.18 ± 0.03 g/cm³. A model of a mechanism explaining the correlation between the size of aggregates and the power of microwaves was proposed. This method of controlling the average size of ZnO NPs aggregates is presented for the first time and similar investigations are not found in the literature.