Antibacterial dental adhesive resins containing nitrogen-doped titanium dioxide nanoparticles

Co-doped titanium dioxide nanoparticles decrease the cytotoxicity of experimental hydrogen peroxide gels for in-office tooth bleaching

OBJECTIVE

To evaluate the efficacy and cytotoxicity of experimental 6% and 35% hydrogen peroxide gels (HP6 or HP35) incorporated with titanium dioxide nanoparticles (NP) co-doped with nitrogen and fluorine and irradiated with a violet LED light (LT).

METHODS

Bovine enamel-dentin disks adapted to artificial pulp chambers were randomly assigned to bleaching (n = 8/group): NC (negative control), NP, HP6, HP6 + LT, HP6 + NP, HP6 + NP + LT, HP35, HP35 + LT, HP35 + NP, HP35 + NP + LT, and commercial HP35 (COM). Color (ΔE00) and whiteness index (ΔWID) changes were measured before and 14 days after bleaching. The extracts (culture medium + diffused gel components) collected after the first session were applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability, oxidative stress, and morphology. The amount of HP diffused through the disks was determined. Data were analyzed by generalized linear models or Kruskal Wallis Tests (α = 5%).  RESULTS: HP6 + NP + LT exhibited ΔE00 and ΔWID higher than HP6 (p < 0.05) and similar to all HP35 groups. HP6 + NP + LT showed the lowest HP diffusion, and the highest cell viability (%) among bleached groups, preserving cell morphology and number of living cells similar to NC and NP. HP6 + LT, HP6 + NP, and HP6 + NP + LT exhibited the lowest cell oxidative stress among bleached groups (p < 0.05). HP35, HP35 + LT, and HP35 (COM) displayed the lowest cell viability.

CONCLUSION

HP6 achieved significantly higher color and whiteness index changes when incorporated with nanoparticles and light-irradiated and caused lower cytotoxicity than HP35 gels. The nanoparticles significantly increased cell viability and reduced the hydrogen peroxide diffusion and oxidative stress, regardless of HP concentration.

CLINICAL SIGNIFICANCE

Incorporation of co-doped titanium dioxide nanoparticles combined with violet irradiation within the HP6 gel could promote a higher perceivable and acceptable efficacy than HP6 alone, potentially reaching the optimal esthetic outcomes rendered by HP35. This approach also holds the promise of reducing cytotoxic damages and, consequently, tooth sensitivity.

Optimization of an ultra-bright real-time high-throughput renilla luciferase assay for antibacterial assessment of Streptococcus mutans biofilms

OBJECTIVE

The present work demonstrates the optimization of a renilla-based real-time, ultra-bright, non-disruptive, high-throughput bioluminescence assay (HTS) to assess the metabolism of intact Streptococcus mutans biofilms and its utility in screening the antibacterial efficacy of experimental nanofilled dental adhesive resins containing varying concentrations of nitrogen-doped titanium dioxide nanoparticles (N_TiO2).

METHODS

Optimization of the assay was achieved by screening real-time bioluminescence changes in intact Streptococcus mutans biofilms imposed by the various experimental biofilm growth parameters investigated (bacterial strain, growth media, sucrose concentration, dilution factor, and inoculum volume). The optimized assay was then used to characterize the antibacterial efficacy of experimental nanofilled dental adhesive resins. The assay's ability to discriminate between bacteriostatic and bactericidal approaches was also investigated.

RESULTS

Relative Light Units (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α = 0.05) and coefficients of variation. An optimized HTS bioluminescence assay was developed displaying RLUs values (brightness) that are much more intense when comparing to other previously reported bioluminescence assays, thereby decreasing the error associated with bioluminescence assays and displaying better utility while investigating the functionalities of antimicrobial nanofilled experimental dental adhesive resins with proven long-term properties.

SIGNIFICANCE

The present study is anticipated to positively impact subsequent research on dental materials and oral microbiology because it serves as a valuable screening tool in metabolic-based assays with increased sensitivity and robustness. The assay reported is anticipated to be further optimized to be used as a co-reporter for other Luc based assays.

Prospectives and challenges of nano-tailored biomaterials-assisted biological molecules delivery for tissue engineering purposes

Nano carriers have gained more attention for their possible medical and technological applications. Tailored nanomaterials can transport medications efficiently to targeted areas and allow for sustained medication discharge, reducing undesirable toxicities while boosting curative effectiveness. Nonetheless, transitioning nanomedicines from experimental to therapeutic applications has proven difficult, so different pharmaceutical incorporation approaches in nano scaffolds are discussed. Then numerous types of nanobiomaterials implemented as carriers and their manufacturing techniques are explored. This article is also supported by various applications of nanobiomaterials in the biomedical field.

Effects of experimental in-office bleaching gels incorporated with co-doped titanium dioxide nanoparticles on dental enamel physical properties

To evaluate the physical properties of enamel submitted to hydrogen peroxide (HP) incorporated with titanium dioxide nanoparticles (NP) co-doped with nitrogen and fluorine and irradiated with violet LED light (LT). Enamel-dentin disks were randomly allocated (T0) into groups, according to HP (HP6, HP15, or HP35) and NP (no NP, 5NP, or 10NP) concentrations, and irradiated or not with LT. A negative control (NC) group was set. After three bleaching sessions (T1, T2, and T3), specimens were stored in saliva for 14 days (T4). Enamel surface microhardness number (KHN), surface roughness (Ra), cross-sectional microhardness (ΔS), energy-dispersive spectroscopy (EDS), scanning electron (SEM), and polarized light (PLM) microscopies were performed. Surface KHN was significantly influenced by NP over time, independently of LT irradiation. At T3 and T4, gels with 5NP and 10NP exhibited no KHN differences compared to NC and baseline values, which were not observed under the absence of NP. NP incorporation did not statistically interfere with the ΔS and Ra. PLM images exhibited surface/subsurface darkening areas suggestive of demineralizing regions. SEM demonstrated some intraprismatic affection in the groups without NP. EDS reported a higher enamel calcium to phosphorus ratio following 10NP gels applications. Gels with NP maintained the enamel surface microhardness levels and seemed to control surface morphology, upholding the mineral content. None of the proposed experimental protocols have negatively influenced the enamel surface roughness and the cross-sectional microhardness.

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.

Recent updates and feasibility of nanodrugs in the prevention and eradication of dental biofilm and its associated pathogens-A review

OBJECTIVES

Dental biofilm is one of the most prevalent diseases in humans, which is mediated by multiple microorganisms. Globally, half of the human population suffers from dental biofilm and its associated diseases. In recent trends, nano-formulated drugs are highly attractive in the treatment of dental biofilms. However, the impact of different types of nanodrugs on the dental biofilm and its associated pathogens have not been published till date. Thus, this review focuses on the recent updates, feasibility, mechanisms, limitations, and regulations of nanodrugs applications in the prevention and eradication of dental biofilm.

STUDY SELECTION, DATA AND SOURCES

A systematic search was conducted in PubMed/Google Scholar/Scopus over the past five years covering the major keywords "nanodrugs, metallic nanoparticles, metal oxide nanoparticles, natural polymers, synthetic polymers, biomaterials, dental biofilm, antibiofilm mechanism, dental pathogens", are reviewed in this study. Nearly, 100 scientific articles are selected in this relevant topic published between 2019 and 2023. Data from the selected studies dealing with nanodrugs used for biofilm treatment was qualitatively analyzed.

CONCLUSIONS

The nanodrugs such as silver nanoparticles, gold nanoparticles, selenium nanoparticles, zinc oxide nanoparticles, copper oxide nanoparticles, titanium oxide nanoparticles, hydroxyapatite nanoparticles and these inorganic nanoparticles incorporated polymer-based nanocomposites, organic/inorganic nanoparticles mediated antimicrobial photodynamic therapy exhibits an excellent antibacterial and antibiofilm activity towards dental pathogens. Finally, this review highlights that bioinspired nanodrugs will be very useful to control the dental biofilm and its associated diseases.

CLINICAL SIGNIFICANCE

Microbial influence on the oral environment is unavoidable; therefore, curing such dental biofilms and pathogens is essential for the impactful reflection of applying biocompatible treatments. In this direction, the current review explains the demand for the nanodrug in inhibiting biofilms for the effective exploration of employing treatments.

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.

Effects of experimental bleaching gels containing co-doped titanium dioxide and niobium pentoxide combined with violet light

OBJECTIVES

The objective of the study is to evaluate the bleaching potential of 6% hydrogen peroxide (6% HP) gels containing NF_TiO2 or Nb2O5 irradiated with a violet LED light and the effects on enamel mineral content and surface morphology.

METHODS

Particles were synthesized, and experimental gels were chemically analyzed by preliminary and accelerated stability tests, pH, and HP decomposition rate. Bovine enamel blocks were treated with 6% HP gels containing (n = 10): 5% NF_TiO2, 5% Nb2O5, 2.5% NF_TiO2 + 2.5% Nb2O5 or without particles (6% HP), irradiated or not with LED, and the control was treated with 35% HP. Color (∆E00) and whitening index (∆WID) variations, surface microhardness (SH), average roughness (∆Ra), Ca-P concentration (EDS), and enamel morphology (SEM) were assessed. Bleaching was performed in 3 sessions of 30 min and 7-day intervals. Data were submitted to two- (pH, decomposition rate, ∆E00, and ∆WID) or three-way ANOVA and Bonferroni (SH), Kruskal-Wallis (∆Ra), and Dunnet tests (α = 0.05).

RESULTS

No changes in the gel's color, odor, or translucency were observed. The pH (6 to 6.5) remained stable over time, and light irradiation boosted the HP decomposition rate. NF_TiO2 and Nb2O5-containing gels displayed higher ∆E00 and ΔWID when light-irradiated (p < 0.05). Nb2O5 and Nb2O5 + NF_TiO2 decreased enamel SH (p < 0.05), but no SH changes were found among groups (p > 0.05). No differences among groups were noted in ∆Ra, Ca-P content, and enamel morphology after treatments (p > 0.05).

CONCLUSION

Experimental light-irradiated 6% HP gels containing NF_TiO2 or Nb2O5 were chemically stable and exhibited bleaching potential comparable with 35% HP.

CLINICAL RELEVANCE

Low-concentrated HP gels containing NF_TiO2 or Nb2O5 and light-irradiated stand as a possible alternative to in-office bleaching.

Mechanical and antibacterial properties of an experimental flowable composite containing Nb2O5 and NF_TiO2 nanoparticles

This study developed an experimental flowable composite incorporated with niobium pentoxide (Nb2O5) combined or not with titanium dioxide co-doped with fluorine and nitrogen (NF_TiO2) and evaluated the mechanical and antibacterial properties. The experimental flowable composite (TEGDMA + BisGMA 1:1 + 60%wt - inorganic filler - borosilicate 0.7 μm) was formulated according to the type and concentration of Nb2O5 and NF_TiO2 (0.5, 1, 1.5 and 2 wt%) or NF_TiO2 + Nb2O5 (0.25, 0.5, 0.75 and 1 wt% - 1:1). The control groups were formed by the experimental composite without the incorporation of Nb2O5 and/or NF_TiO2 (GC-E) and by a commercial flowable composite (GC). The characterization of the surface of the composite and its particles was carried out using scanning electron microscopy (SEM) and energy dispersive x-rays (EDX). Specimens were manufactured and subjected to mechanical tests of flexural strength (FS) (n = 12), flexural modulus (FM) (n = 12), roughness (Ra) (n = 10), microhardness (n = 10), and contact angle (n = 10); and, to evaluate the antibacterial activity, they were submitted to tests of biofilm formation against S. mutans (CFU/mL) (n = 5), biofilm biomass by dry weight (n = 5) and confocal laser microscopy (%LIVE/DEAD) (n = 5). Data were submitted to one-way ANOVA and Tukey's post-hoc and, those that were not homoscedastic, but with normality, were submitted to Welch's ANOVA and Games-Howell's post-hoc. Dunnet's test was used to compare the controls with the other experimental groups (α = 5). The Nb2O5 particles had an average size of 32.4 μm and the nanoparticles (NPs) of NF_TiO2, 10 nm. EDX analysis identified isolated peaks of N, F, Ti, and Nb confirming the presence of these particles in the resin matrix. The 1.5% NF_TiO2 group had a higher FS and FM than the controls (p < 0.05). GC showed higher microhardness between groups (p < 0.05). There was no difference between the experimental groups regarding contact angle and roughness (p > 0.05), except for GC, which had the highest Ra values and the lowest contact angle between groups (p < 0.05). Composites containing 0.5%, 1%, 1.5%, and 2% Nb2O5, 1%, 1.5%, and 2% NF_TiO2 and 2% Nb2O5 + NF_TiO2 showed lower biofilm formation (p < 0.05), lower total biofilm biomass (p < 0.05), and a higher percentage of dead cells (44%, 52%, 52%, 79%, 42% 43%, 62%, 65%, respectively) than GC and GC-E (5% and 1%, respectively). It is concluded that the incorporation of 1.5% NF_TiO2 promoted a greater FS and FM among the experimental composites and that the addition of Nb2O5 particles (0.5%, 1%, 1.5%, and 2%), NF_TiO2 (1%, 1.5% and 2%) and the combination Nb2O5 + NF_TiO2 (2%) showed significant antibacterial effects.

Recent advances on nanomaterials for antibacterial treatment of oral diseases

An imbalance of bacteria in oral environment can lead to a variety of oral diseases, such as periodontal disease, dental caries, and peri-implant inflammation. In the long term, in view of the increasing bacterial resistance, finding suitable alternatives to traditional antibacterial methods is an important research today. With the development of nanotechnology, antibacterial agents based on nanomaterials have attracted much attention in dental field due to their low cost, stable structures, excellent antibacterial properties and broad antibacterial spectrum. Multifunctional nanomaterials can break through the limitations of single therapy and have the functions of remineralization and osteogenesis on the basis of antibacterial, which has made significant progress in the long-term prevention and treatment of oral diseases. In this review, we have summarized the applications of metal and their oxides, organic and composite nanomaterials in oral field in recent five years. These nanomaterials can not only inactivate oral bacteria, but also achieve more efficient treatment and prevention of oral diseases by improving the properties of the materials themselves, enhancing the precision of targeted delivery of drugs and imparting richer functions. Finally, future challenges and untapped potential are elaborated to demonstrate the future prospects of antibacterial nanomaterials in oral field.

Recent advances in the use of inorganic nanomaterials as anti caries agents

Caries is the most prevalent and widespread chronic oral disease. Traditional caries filling materials, due to their lack of anti-caries capabilities, can readily develop secondary caries. Nanomaterials proposed as an effective approach for caries treatment can inhibit biofilm formation. It also can not only reduce demineralization but also promote remineralization. In recent years, nanotechnology in anti-caries materials, particularly nano-adhesive and nano-composite resin, has advanced rapidly. Because inorganic nanoparticles (NPs) interfere with bacterial metabolism and inhibit biofilm development, inorganic NPs have emerged as a new trend in dental applications. Metal and metal oxide NPs by releasing metal ions, oxidative stress induction, and non-oxidative mechanisms showed significant antimicrobial activity. For applying metal and metal oxide NPs as anti caries agents, silver, zinc, titanium, copper, and calcium ions have been shown significant attention. Moreover, fluoride functionalized inorganic NPs were also employed to improve their efficacy of them. The fluoride-functionalized NPs can promote remineralization, and inhibit demineralization by enhancing apatite formation. In this review, we have provided an overview and recent advances in the use of inorganic NPs as anti caries agents. Furthermore, their antimicrobial, remineralizing, and mechanical impacts on dental materials were discussed.

Glutamine coated titanium for synergistic sonodynamic and photothermal on tumor therapy upon targeted delivery

Introduction: The application of titanium dioxide nanoparticles (TiO₂ NPs) for cancer therapy has been studied for decades; however, the targeted delivery of TiO₂ NPs to tumor tissues is challenging, and its efficiency needs to be improved. Method: In this study, we designed an oxygen-deficient TiO_2-x coated with glutamine layer for targeted delivery, as well as the enhanced separation of electrons (e-) and holes (h+) following the joint application of sonodynamic therapy (SDT) and photothermal therapy (PTT). Results: This oxygen-deficient TiO_2-x possesses relatively high photothermal and sonodynamic efficiency at the 1064 nm NIR-II bio-window. The GL-dependent design eased the penetration of the TiO_2-x into the tumor tissues (approximately three-fold). The in vitro and in vivo tests showed that the SDT/PTT-based synergistic treatment achieved more optimized therapeutic effects than the sole use of either SDT or PTT. Conclusion: Our study provided a safety targeted delivery strategy, and enhanced the therapeutic efficiency of SDT/PTT synergistic treatment.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens’ colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.

Characterization of Experimental Nanoparticulated Dental Adhesive Resins with Long-Term Antibacterial Properties

Experimental adhesives with functional nitrogen-doped titanium dioxide nanoparticles (N_TiO₂) have been shown to display improved properties. However, these materials have not been characterized regarding their degree of conversion (DC), biaxial flexure strength (BFS), surface roughness (SR), elastic modulus (EM), and long-term antibacterial functionalities. Experimental adhesives were synthesized by dispersing N_TiO₂ (10%, 20%, or 30%, v/v%) into OptiBond Solo Plus (OPTB, Kerr Corp., USA). Unpolymerized adhesives (volume = 50 μL/drop, n = 3/group) were individually placed onto a heated (37 °C) attenuated total reflectance (ATR) monolithic diamond crystal (Golden Gate, Specac). The spectra of composites were obtained with a Fourier-transform infrared (FTIR) spectrometer (Nicolet IS50; 500-4500 cm^-1; resolution = 4 cm^-1, 10 internal scans/spectrum) before and after polymerization. Disk-shaped specimens (diameter = 6.0 mm, thickness = 0.5 mm) for BFS (n = 12/group), SR and EM (n = 3/group), and for antibacterial testing (n = 18/group/time-point) were fabricated and photopolymerized (1 min each; 385-515 nm, 1000 mW/cm²; VALO). DC values (%) were calculated from pre- and post-polymerization spectra using the two-frequency method and tangent-baseline technique. BFS was assessed using a universal testing machine (Instron 68TM-5, crosshead speed = 1.27 mm/min, 25 °C). SR and EM were investigated using an atomic force microscope (Multimode 8) with aluminum-coated silicon probes (8 nm pyramidal tip, spring constant 40 N/m, Bruker). Antibacterial testing was performed by growing Streptococcus mutans biofilms (UA159-ldh, 37 °C, microaerophilic) on the surfaces of specimens for 24 h and then measuring the relative luminescence units (RLU) with a Biotek Synergy HT multi-well plate reader. Results demonstrate that experimental materials containing 10%, 20%, and 30% of N_TiO₂ displayed higher levels of DC, had better mechanical properties, and were able to exert strong and durable antibacterial properties without visible light irradiation and after extended periods of simulated shelf-life and aging in PBS. The reported experimental materials are expected to increase the service lives of polymer-based bonded restorations by decreasing the incidence of secondary caries.

Metal-Based Nanoparticles: Antibacterial Mechanisms and Biomedical Application

The growing increase in antibiotic-resistant bacteria has led to the search for new antibacterial agents capable of overcoming the resistance problem. In recent years, nanoparticles (NPs) have been increasingly used to target bacteria as an alternative to antibiotics. The most promising nanomaterials for biomedical applications are metal and metal oxide NPs, due to their intrinsic antibacterial activity. Although NPs show interesting antibacterial properties, the mechanisms underlying their action are still poorly understood, limiting their use in clinical applications. In this review, an overview of the mechanisms underlying the antibacterial activity of metal and metal oxide NPs will be provided, relating their efficacy to: (i) bacterial strain; (ii) higher microbial organizations (biofilm); (iii) and physico-chemical properties of NPs. In addition, bacterial resistance strategies will be also discussed to better evaluate the feasibility of the different treatments adopted in the clinical safety fields. Finally, a wide analysis on recent biomedical applications of metal and metal oxide NPs with antibacterial activity will be provided.

Novel Experimental In-Office Bleaching Gels Containing Co-Doped Titanium Dioxide Nanoparticles

The present study reports on the development and testing of novel bleaching agents containing co-doped metaloxide nanoparticles (NP; 0%, 5%, 10% v/w) and hydrogen peroxide (HP, 0%, 6%, 15%, and 35%). Bovine blocks (n = 200, A = 36 mm2) were obtained and randomly distributed into experimental groups (n = 10/group). NPs were incorporated into gels before bleaching (3 sessions, 7 days apart, 30 min/session, irradiated with violet light-LT). Color changes (ΔE00, ΔWID), mineral content (CO32−, PO43−), and topography were assessed (spectrophotometer, ATR-FTIR, and AFM) before and after bleaching procedures (14 days). Metabolic status and three-dimensional components of non-disrupted Streptococcus mutans biofilms were investigated using a multimode reader and confocal microscopy. The results indicate that ΔE00 and ΔWID significantly increased with NPs’ concentrations and LT. The enamel’s mineral ratio was adversely impacted by HP, but alterations were less pronounced when using NP-containing gels. The enamel’s topography was not damaged by the bleaching protocols tested. The bioluminescence results show that bleaching protocols do not render latent antibacterial properties to enamel, and the confocal microscopy results demonstrate that the 3-dimensional distribution of the components was affected by the protocols. The proposed nanotechnology improved the bleaching efficacy of experimental materials independent of hydrogen peroxide or irradiation and did not adversely impact the enamel’s surface properties or its chemical content.

[Mechanical and light-activated antibacterial properties of resin filled with Ag-TiO2 nanoparticles]

The poor mechanical property and vulnerability to bacterial infections are the main problems in clinic for dental restoration resins. Based on this problem, the purpose of this study is to synthesize silver-titanium dioxide (Ag-TiO2) nanoparticles with good photocatalytic properties, and add them to the composite resin to improve the mechanical properties and photocatalytic antibacterial capability of the resin. The microstructure and chemical composition of Ag-TiO2 nanoparticles and composite resins were characterized. The results indicated that Ag existed in both metallic and silver oxide state in the Ag-TiO2, and Ag-TiO2 nanoparticles were uniformly dispersed in the resins. The results of mechanical experiments suggested that the mechanical properties of the composite resin were significantly improved due to the incorporation of Ag-TiO2 nanoparticles. The antibacterial results indicated that the Ag-TiO2 nanoparticle-filled composite resins exhibited excellent antibacterial activities under 660 nm light irradiation for 10 min due to the photocatalysis, and the Ag-TiO2 nanoparticle-filled composite resins could also exhibit excellent antibacterial activities after contact with bacteria for 24 h without light irradiation because of the release of Ag ions. In summary, this study provides a new antibacterial idea for the field of dental composite resins.

Dental Materials for Oral Microbiota Dysbiosis: An Update

The balance or dysbiosis of the microbial community is a major factor in maintaining human health or causing disease. The unique microenvironment of the oral cavity provides optimal conditions for colonization and proliferation of microbiota, regulated through complex biological signaling systems and interactions with the host. Once the oral microbiota is out of balance, microorganisms produce virulence factors and metabolites, which will cause dental caries, periodontal disease, etc. Microbial metabolism and host immune response change the local microenvironment in turn and further promote the excessive proliferation of dominant microbes in dysbiosis. As the product of interdisciplinary development of materials science, stomatology, and biomedical engineering, oral biomaterials are playing an increasingly important role in regulating the balance of the oral microbiome and treating oral diseases. In this perspective, we discuss the mechanisms underlying the pathogenesis of oral microbiota dysbiosis and introduce emerging materials focusing on oral microbiota dysbiosis in recent years, including inorganic materials, organic materials, and some biomolecules. In addition, the limitations of the current study and possible research trends are also summarized. It is hoped that this review can provide reference and enlightenment for subsequent research on effective treatment strategies for diseases related to oral microbiota dysbiosis.

Polymeric Dental Nanomaterials: Antimicrobial Action

This review aims to describe and critically analyze studies published over the past four years on the application of polymeric dental nanomaterials as antimicrobial materials in various fields of dentistry. Nanoparticles are promising antimicrobial additives to restoration materials. According to published data, composites based on silver nanoparticles, zinc(II), titanium(IV), magnesium(II), and copper(II) oxide nanoparticles, chitosan nanoparticles, calcium phosphate or fluoride nanoparticles, and nanodiamonds can be used in dental therapy and endodontics. Composites with nanoparticles of hydroxyapatite and bioactive glass proved to be of low efficiency for application in these fields. The materials applicable in orthodontics include nanodiamonds, silver nanoparticles, titanium(IV) and zinc(II) oxide nanoparticles, bioactive glass, and yttrium(III) fluoride nanoparticles. Composites of silver nanoparticles and zinc(II) oxide nanoparticles are used in periodontics, and nanodiamonds and silver, chitosan, and titanium(IV) oxide nanoparticles are employed in dental implantology and dental prosthetics. Composites based on titanium(IV) oxide can also be utilized in maxillofacial surgery to manufacture prostheses. Composites with copper(II) oxide nanoparticles and halloysite nanotubes are promising materials in the field of denture prosthetics. Composites with calcium(II) fluoride or phosphate nanoparticles can be used in therapeutic dentistry for tooth restoration.

Metal and Metal Oxide Nanoparticles in Caries Prevention: A Review

Nanoparticles based on metal and metallic oxide have become a novel trend for dental use as they interfere with bacterial metabolism and prevent biofilm formation. Metal and metal oxide nanoparticles demonstrate significant antimicrobial activity by metal ion release, oxidative stress induction and non-oxidative mechanisms. Silver, zinc, titanium, copper, and magnesium ions have been used to develop metal and metal oxide nanoparticles. In addition, fluoride has been used to functionalise the metal and metal oxide nanoparticles. The fluoride-functionalised nanoparticles show fluoride-releasing properties that enhance apatite formation, promote remineralisation, and inhibit demineralisation of enamel and dentine. The particles' nanoscopic size increases their surface-to-volume ratio and bioavailability. The increased surface area facilitates their mechanical bond with tooth tissue. Therefore, metal and metal oxide nanoparticles have been incorporated in dental materials to strengthen the mechanical properties of the materials and to prevent caries development. Another advantage of metal and metal oxide nanoparticles is their easily scalable production. The aim of this study is to provide an overview of the use of metal and metal oxide nanoparticles in caries prevention. The study reviews their effects on dental materials regarding antibacterial, remineralising, aesthetic, and mechanical properties.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

OBJECTIVE

To develop an aesthetic resin composite using a nitrogen-doped titanium dioxide (NTiO₂) filler that possesses antimicrobial properties against cariogenic bacteria.

METHODS

N-TiO₂ powder was manufactured by calcining commercial TiO₂ with urea. Free radical release from the N-TiO₂ powder under visible light irradiation was analysed using UV-Vis spectrophotometry. The N-TiO₂ powder was incorporated into a dental resin and the photocatalytic activity assessed using a dye under both visible light and dark conditions. Using XTT assay to measure the cellular metabolic activity, the antibacterial properties of the N-TiO₂ /resin composite discs were tested using Streptococcus mutans.

RESULTS

Doping nitrogen of TiO₂ resulted in a band gap shift towards the visible light spectrum, which enabled the powder to release reactive oxygen species when exposed to visible light. When incorporated into a dental resin, the N-TiO₂/resin composite still demonstrated sustained release of reactive oxygen species, maintaining its photocatalytic activity and showing an antibacterial effect towards Streptococcus mutans under visible light conditions.

SIGNIFICANCE

N-TiO₂ filled resin composite shows great promise as a potential aesthetic resin based adhesive for orthodontic bonding.

Assessment of Streptococcus mutans biofilms on orthodontic adhesives over 7 days

INTRODUCTION

The purpose of this study was to compare the metabolism of Streptococcus mutans biofilms after 1-7 days of growth on different orthodontic adhesives.

METHODS

Specimens of 6 commercial orthodontic adhesives were fabricated in custom-made molds and polymerized using a light-emitting diode light-curing unit. Bioluminescent S mutans (UA159:JM10) biofilms were grown on ultraviolet-sterilized specimens for 1, 3, 5, and 7 days (n = 18 biofilms/d/product) in anaerobic conditions at 37°C. The metabolism of biofilms (relative luminescence unit [RLU]) was measured 0, 2, 4, and 6 minutes after exposure to D-luciferin solution using a microplate reader. A linear mixed-effects model was used to analyze the logarithm of RLU (log RLU). The model included fixed effects of products, days, and minutes. Tukey-Kramer post-hoc tests were then performed on the significant predictors of log RLU (α = 0.05).

RESULTS

Days (P <0.0001) and minutes (P <0.0001) were independent predictors of log RLU, but the products were not (P = 0.5869). After adjusting for minutes, the log RLU was analyzed with a post-hoc test, and all differences between days were significant with the exceptions of day 3 from day 5 (P = 0.0731) and day 5 from day 7 (P = 0.8802). After adjusting for day, log RLU was analyzed with a post-hoc test and all differences in minutes were significant.

CONCLUSIONS

No significant differences in the metabolism of S mutans biofilms were observed among the 6 orthodontic adhesives. Biofilms that were grown for 3 days demonstrated the highest levels of biofilm metabolism as evidenced by higher mean log RLU values relative to 1, 5, and 7-day growth durations.

Physicochemical and Mechanical Properties of Bis-GMA/TEGDMA Dental Composite Resins Enriched with Quaternary Ammonium Polyethylenimine Nanoparticles

Modification of dental monomer compositions with antimicrobial agents must not cause deterioration of the structure, physicochemical, or mechanical properties of the resulting polymers. In this study, 0.5, 1, and 2 wt.% quaternary ammonium polyethylenimine nanoparticles (QA-PEI-NPs) were obtained and admixed with a Bis-GMA/TEGDMA (60:40) composition. Formulations were then photocured and tested for their degree of conversion (DC), polymerization shrinkage (S), glass transition temperature (T_g), water sorption (WS), solubility (SL), water contact angle (WCA), flexural modulus (E), flexural strength (σ), hardness (HB), and impact resistance (a_n). We found that the DC, S, Tg, WS, E, and HB were not negatively affected by the addition of QA-PEI-NPs. Changes in these values rarely reached statistical significance. On the other hand, the SL increased upon increasing the QA-PEI-NPs concentration, whereas σ and a_n decreased. These results were usually statistically significant. The WCA values increased slightly, but they remained within the range corresponding to hydrophilic surfaces. To conclude, the addition of 1 wt.% QA-PEI-NPs is suitable for applications in dental materials, as it ensures sufficient physicochemical and mechanical properties.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

Novel Approaches to Combat Medical Device-Associated BioFilms

Biofilms are aggregates formed as a protective survival state by microorganisms to adapt to the environment and can be resistant to antimicrobial agents and host immune responses due to chemical or physical diffusion barriers, modified nutrient environments, suppression of the growth rate within biofilms, and the genetic adaptation of cells within biofilms. With the widespread use of medical devices, medical device-associated biofilms continue to pose a serious threat to human health, and these biofilms have become the most important source of nosocomial infections. However, traditional antimicrobial agents cannot completely eliminate medical device-associated biofilms. New strategies for the treatment of these biofilms and targeting biofilm infections are urgently required. Several novel approaches have been developed and identified as effective and promising treatments. In this review, we briefly summarize the challenges associated with the treatment of medical device-associated biofilm infections and highlight the latest promising approaches aimed at preventing or eradicating these biofilms.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.

Effect of titanium dioxide nanoparticle reinforcement on flexural strength of denture base resin: A systematic review and meta-analysis

The study was designed to assess the change in flexural strength of unmodified heat cure denture base polymer resin on reinforcement with titanium dioxide nanoparticles in different concentrations. In vitro, randomized control trials reporting flexural strength of titanium dioxide nanoparticle reinforced resin were selected. The review was formulated based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses- Protocol (PRISMA-P) guidelines. Quality assessment was performed according to Consolidated Standards Of Reporting Trials (CONSORT) guidelines and risk of bias Cochrane tool. Six articles in the category of 1%, 3%, 5% weight fractions of titanium dioxide nanoparticles were subjected to a meta-analysis. A meta-analysis was performed using random-effects at a 95% confidence interval. Within the limitations of the study, it can be assumed that there is no precise conformity on the ideal titanium dioxide nanoparticle concentration required to improve the flexural strength of the polymer. Stringent use of standard ISO guidelines may help in obtaining consistent results.

Bibliometric Analysis of Literature Published on Antibacterial Dental Adhesive from 1996-2020

This study aimed to investigate the current state of research on antibacterial dental adhesives. The interest in this field can be drawn from an increasing number of scholarly works in this area. However, there is still a lack of quantitative measurement of this topic. The main aim of this study was to consolidate the research published on the antibacterial adhesive from 1996 to 2020 in Web of Science indexed journals. The bibliometric method, a quantitative study of investigating publishing trends and patterns, was used for this study. The result has shown that a gradual increase in research was found, whereby a substantial increase was observed from 2013. A total of 248 documents were published in 84 journals with total citations of 5107. The highly cited articles were published mainly in Q1 category journals. Most of the published articles were from the USA, China, and other developed countries; however, some developing countries contributed as well. The authorship pattern showed an interdisciplinary and collaborative approach among researchers. The thematic evaluation of keywords along with a three-factor analysis showed that 'antibacterial adhesives' and 'quaternary ammonium' have been used commonly. This bibliometric analysis can provide direction not only to researchers but also to funding organizations and policymakers.

Nanoparticles of Quaternary Ammonium Polyethylenimine Derivatives for Application in Dental Materials

Various quaternary ammonium polyethylenimine (QA-PEI) derivatives have been synthesized in order to obtain nanoparticles. Due to their antibacterial activity and non-toxicity towards mammalian cells, the QA-PEI nanoparticles have been tested extensively regarding potential applications as biocidal additives in various dental composite materials. Their impact has been examined mostly for dimethacrylate-based restorative materials; however, dental cements, root canal pastes, and orthodontic adhesives have also been tested. Results of those studies showed that the addition of small quantities of QA-PEI nanoparticles, from 0.5 to 2 wt.%, led to efficient and long-lasting antibacterial effects. However, it was also discovered that the intensity of the biocidal activity strongly depended on several chemical factors, including the degree of crosslinking, length of alkyl telomeric chains, degree of N-alkylation, degree of N-methylation, counterion type, and pH. Importantly, the presence of QA-PEI nanoparticles in the studied dental composites did not negatively impact the degree of conversion in the composite matrix, nor its mechanical properties. In this review, we summarized these features and functions in order to present QA-PEI nanoparticles as modern and promising additives for dental materials that can impart unique antibacterial characteristics without deteriorating the products' structures or mechanical properties.

Advances of Anti-Caries Nanomaterials

Caries is the most common and extensive oral chronic disease. Due to the lack of anti-caries properties, traditional caries filling materials can easily cause secondary caries and lead to treatment failure. Nanomaterials can interfere with the bacteria metabolism, inhibit the formation of biofilm, reduce demineralization, and promote remineralization, which is expected to be an effective strategy for caries management. The nanotechnology in anti-caries materials, especially nano-adhesive and nano-composite resin, has developed fast in recent years. In this review, the antibacterial nanomaterials, remineralization nanomaterials, and nano-drug delivery systems are reviewed. We are aimed to provide a theoretical basis for the future development of anti-caries nanomaterials.

Sorption, solubility and cytotoxicity of novel antibacterial nanofilled dental adhesive resins

Dental adhesives hydrolyze in the mouth. This study investigated the water sorption (SOR), solubility (SOL) and cytotoxicity (CYTO) of experimental adhesives containing nitrogen-doped titanium dioxide nanoparticles (N_TiO₂). Specimens (n = 15/group [SOR, SOL]; n = 10/group [CYTO]) of unaltered Clearfil SE Protect (CSP), OptiBond Solo Plus (OSP), Adper Scotchbond (ASB) and experimental adhesives (OSP + 25% or 30% of N_TiO₂) were fabricated, desiccated (37 °C) and tested for SOR and SOL according to ISO Specification 4049 (2009). CYTO specimens were UV-sterilized (8 J/cm²) and monomer extracted in growth medium (1, 3 or 7 days). Human pulp cells were isolated and seeded (0.5 × 10⁴) for MTT assay. SOR and SOL data was analyzed using GLM and SNK (α = 0.05) and CYTO data was analyzed with Kruskal–Wallis and SNK tests (α = 0.05). SOR and SOL values ranged from 25.80 μg/mm³ (30% N_TiO₂) to 28.01 μg/mm³ (OSP) and 23.88 μg/mm³ (30% N_TiO₂) to 25.39 μg/mm³ (25% N_TiO₂). CYTO results indicated that pulp cells exposed to experimental materials displayed comparable viabilities (p > 0.05) to those of OSP. Experimental materials displayed comparable SOR, SOL and CYTO values (p > 0.05) when compared to unaltered materials. N_TiO₂ incorporation have not adversely impacted SOR, SOL and CYTO properties of unaltered adhesives.

Advanced characterization of surface-modified nanoparticles and nanofilled antibacterial dental adhesive resins

Nanotechnology can improve the performance of dental polymers. The objective of this study was to modify the surfaces of nanoparticles with silanes and proteins, characterize nanoparticles' agglomeration levels and interfaces between nanoparticles and the polymeric matrix. Undoped (n-TiO2), nitrogen-doped (N_TiO2) and nitrogen-fluorine co-doped titanium dioxide nanoparticles (NF_TiO2) were synthesized and subjected to surface modification procedures in preparation for Small-Angle X-Ray Scattering (SAXS) and Small-Angle Neutron Scattering (SANS) characterizations. Experimental adhesives were manually synthesized by incorporating 20% (v/v) of n-TiO2, N_TiO2 or NF_TiO2 (as-synthesized or surface-modified) into OptiBond Solo Plus (OPTB). Specimens (n = 15/group; d = 6.0 mm, t = 0.5 mm) of OPTB and experimental adhesives were characterized using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), 2-D ToF-SIMS chemical imaging and SANS. SAXS results indicated that surface-modified nanoparticles displayed higher scattering intensities in a particle-size dependent manner. ToF-SIMS results demonstrated that nanoparticles' incorporation did not adversely impact the parental polymer. 2-D ToF-SIMS chemical imaging demonstrated the distribution of Ti+ and confirmed nitrogen-doping levels. SANS results confirmed nanoparticles' functionalization and revealed the interfaces between nanoparticles and the polymer matrix. Metaloxide nanoparticles were successfully fabricated, incorporated and covalently functionalized in a commercial dental adhesive resin, thereby supporting the utilization of nanotechnology in dentistry.

The Applicability of a Drop Penetration Method to Measure Contact Angles on TiO2 and ZnO Nanoparticles

In this study, six solvents (water, diiodomethane, bromonaphthalene, formamide, ethanol and ethylene glycol) were examined for three nanoparticle substrates, zinc oxide and titanium dioxide (21 nm and 100 nm), with the goal of assessing the suitability of a modified drop penetration method (DPM) for orders of magnitude smaller particles. Nanoparticles were compressed into flat discs and the solvent dropped on the surface while the image with time was recorded. Contact angles were in reasonable agreement with literature over the range of 20–80°, but failed to provide acceptable results for surface energy components. It was necessary to eliminate certain solvents and substrates not meeting the selection criteria.

Optimization of a real-time high-throughput assay for assessment of Streptococcus mutans metabolism and screening of antibacterial dental adhesives

Objective.

The present work shows the optimization of a high-throughput bioluminescence assay to assess the metabolism of intact Streptococcus mutans biofilms and its utility as a screening method for nanofilled antibacterial dental materials.

Methods.

The assay was optimized by monitoring changes in bioluminescence mediated by variation of the experimental parameters investigated (growth media and sucrose concentration, inoculum:D-Luciferin ratio, dilution factor, inoculum volume, luminescence wavelength, replicate and luciferase metabolic activity). Confocal microscopy was then used to demonstrate the impact of biofilm growth conditions on the 3-D distribution of extracellular polymeric substance (EPS) within Streptococcus mutans biofilms and its implications as confounding factors in high-throughput studies (HTS).

Results.

Relative Luminescence Unit (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α = 0.05) and coefficients of variation, whereas data from 3-D structural parameters and RLU values of biofilms grown on experimental antibacterial dental adhesive resins were analyzed using General Linear Models and Student–Newman–Keuls post hoc tests (α = 0.05). Confocal microscopy demonstrated that biofilm growth conditions significantly influenced the quantity and distribution of EPS within the 3-D structures of the biofilms. An optimized HTS bioluminescence assay was developed and its applicability as a screening method in dentistry was demonstrated using nanofilled experimental antibacterial dental adhesive resins.

Significance.

The present study is anticipated to positively impact the direction of future biofilm research in dentistry, because it offers fundamental information for the design of metabolic-based assays, increases the current levels of standardization and reproducibility while offering a tool to decrease intra-study variability.

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.

Synthesis and characterization of crustin capped titanium dioxide nanoparticles: Photocatalytic, antibacterial, antifungal and insecticidal activities

Current scenario of bio-nanotechnology, successfully fabrication of ultrafine titanium dioxide nanoparticles (TiO₂NPs) using various biological protein sources for the multipurpose targets. The present research report involves synthesis of TiO₂NPs using antimicrobial peptide (AMP) crustin (Cr). Crustin previously purified from the blue crab, Portunus pelagicus haemolymph, by blue Sepharose CL-6B matrix assisted affinity column chromatography. Synthesized Cr-TiO₂NPs was physico-chemically characterized by UV-Visible spectroscopy (UV-Visible), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High-resolution transmission electron microscopy (HR-TEM) and zeta potential examination. X-ray diffraction analysis for crystalline nature and phase identification of titanium dioxide nanoparticles was absorbed. Functional groups were found through FTIR ranges between 1620 and 1700 cm^-1. HR-TEM analysis showed that the synthesized Cr-TiO₂NPs tetragonal shape and sizes ranging from 10 to 50 nm. Finally, the surface charge of the Cr-TiO₂NPs was confirmed through zeta potential analysis. Furthermore, the characterized Cr-TiO₂NPs exhibited good biofilm inhibition against GPB - S. mutans (Gram Positive Bacteria- Streptococcus mutans), GNB - P. vulgaris (Gram Negative Bacteria- Proteus vulgaris) and fungal Candida albicans. Moreover, photocatalysis demonstrated that the Cr-TiO₂NPs was effectively explored the degradation of dyes. The results suggest that Cr-TiO₂NPs is an excellent bactericidal, fungicidal and photocatalytic agent that can be supportively used for biomedical and industrial applications.

Fueling a Hot Debate on the Application of TiO2 Nanoparticles in Sunscreen

Titanium is one of the most abundant elements in the earth's crust and while there are many examples of its bioactive properties and use by living organisms, there are few studies that have probed its biochemical reactivity in physiological environments. In the cosmetic industry, TiO2 nanoparticles are widely used. They are often incorporated in sunscreens as inorganic physical sun blockers, taking advantage of their semiconducting property, which facilitates absorbing ultraviolet (UV) radiation. Sunscreens are formulated to protect human skin from the redox activity of the TiO2 nanoparticles (NPs) and are mass-marketed as safe for people and the environment. By closely examining the biological use of TiO2 and the influence of biomolecules on its stability and solubility, we reassess the reactivity of the material in the presence and absence of UV energy. We also consider the alarming impact that TiO2 NP seepage into bodies of water can cause to the environment and aquatic life, and the effect that it can have on human skin and health, in general, especially if it penetrates into the human body and the bloodstream.

Application of Antimicrobial Nanoparticles in Dentistry

Oral cavity incessantly encounters a plethora of microorganisms. Plaque biofilm-a major cause of caries, periodontitis and other dental diseases-is a complex community of bacteria or fungi that causes infection by protecting pathogenic microorganisms from external drug agents and escaping the host defense mechanisms. Antimicrobial nanoparticles are promising because of several advantages such as ultra-small sizes, large surface-area-to-mass ratio and special physical and chemical properties. To better summarize explorations of antimicrobial nanoparticles and provide directions for future studies, we present the following critical review. The keywords "nanoparticle," "anti-infective or antibacterial or antimicrobial" and "dentistry" were retrieved from Pubmed, Scopus, Embase and Web of Science databases in the last five years. A total of 172 articles met the requirements were included and discussed in this review. The results show that superior antibacterial properties of nanoparticle biomaterials bring broad prospects in the oral field. This review presents the development, applications and underneath mechanisms of antibacterial nanoparticles in dentistry including restorative dentistry, endodontics, implantology, orthodontics, dental prostheses and periodontal field.