Cytotoxicity and antimicrobial efficiency of ZrO2 nanoparticles reinforced 3D printed resins

Development of 3-dimensionally printed denture base material utilizing hybrid polymer: A preliminary investigation

STATEMENT OF PROBLEM

Current 3-dimensionally (3D) printed denture bases have inadequate strength and durability for long-term use, and milled denture bases generate excessive waste. Addressing these limitations is crucial to advancing prosthetic dentistry, ensuring improved patient outcomes and promoting environmental responsibility.

PURPOSE

The purpose of this in vitro study was to incorporate microparticles into a commercially available 3D printed denture base resin and compare its mechanical and biological properties with the conventional polymethyl methacrylate (PMMA) denture base material.

MATERIAL AND METHODS

Microparticles were collected from milled zirconia blanks and were blended with a 3D printing denture base resin (NextDent Denture 3D+). The optimal zirconia microparticle content (2%) for blending and printed was determined by using a liquid-crystal display (LCD) 3D printer. The printed specimens were then postrinsed and postpolymerized based on the manufacturer's instructions. Mechanical and biological characterization were carried out in terms of flexural strength, fracture toughness, and fungal adhesion. One-way ANOVA was carried out to analyze the results statistically.

RESULTS

The incorporation of microparticles in the 3D printed denture demonstrated higher mechanical strength (104.77 ±7.60 MPa) compared with conventional heat-polymerized denture base resin (75.15 ±24.41 MPa) (P<.001), but the mechanical strength deteriorated when compared with the unmodified 3D printing resin (122.17 ±11.58 MPa) (P<.001). However, the modified 3D printed denture showed greater antibacterial activity (1184.00 ±243.25 CFU/mL) than the unmodified resin (1486.50 ±103.94 CFU/mL) (P=.045).

CONCLUSIONS

The incorporation of microparticles into the 3D printed denture base resin demonstrated the potential to enhance the mechanical and biological properties of the denture base when compared with conventional techniques. However, when compared with the unmodified 3D printed denture base resin, the mechanical properties deteriorated while the biological properties improved.

Insights into in-vitro studies and molecular modelling of the antimicrobial efficiency of 4-chlorobenzaldehyde and 4-methoxybenzaldehyde derivatives

Owing to the significant gap in the knowledge and understanding of the mechanisms of antimicrobial action and the development of resistance, the optimization of antimicrobial therapies therefore becomes a necessity. It is on this note, that this study seeks to both experimentally and theoretically investigate the antimicrobial efficiency of two synthesized compounds namely; 1-((4-methoxyphenyl) (morpholino)methyl)thiourea (MR1) and diethyl 4-(4-chlorophenyl)-2,6-diphenyl-1,4-dihydropyridine-3,5-dicarboxylate (HRC). Utilizing the density functional theory (DFT), the compounds were optimized at ωB97XD/6-31++G(2d, 2p) level of theory. This provided a clear explanation for their distinct reactivity and stability potentials. More so, the natural bond orbital (NBO) analysis confirmed strong intra and intermolecular interactions, which agreed with the calculated reactivity parameters and density of states (DOS). Upon assessing the antimicrobial efficacy of the synthesized compounds, it was found that they exhibited lower activity against Enterobacter and A. niger, but considerable activity against Moraxella. In contrast, they showed higher activity against B. subtilis and Trichophyton, indicating that the compounds are more effective against gram-positive bacteria than gram-negative ones. Hence, it can be asserted that the synthesized compounds have superior antifungal action than antibacterial activity. A fascinating aspect of the data is that they show interactions that are incredibly insightful, totally correlating with the simulations of both molecular docking and molecular dynamics. Therefore, the alignment between experimental findings and computational simulations strengthens the validity of the study's conclusions, emphasizing the significance of the synthesized compounds in the context of optimizing antimicrobial therapies.Communicated by Ramaswamy H. Sarma.

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Enhancing 3D-printed denture base resins: A review of material innovations

The limited physical and mechanical properties of polymethyl methacrylate (PMMA), the current gold standard, necessitates exploring improved denture base materials. While three-dimensional (3D) printing offers accuracy, efficiency, and patient comfort advantages, achieving superior mechanics in 3D-printed denture resins remains challenging despite good biocompatibility and esthetics. This review investigates the potential of innovative materials to address the limitations of 3D-printed denture base materials. Thus, this article is organized to provide a comprehensive overview of recent efforts to enhance 3D-printed denture base materials, highlighting advancements. It critically examines the impact of incorporating various nanoparticles (zirconia, titania, etc.) on these materials' physical and mechanical properties. Additionally, it delves into recent strategies for nanofiller surface treatment and biocompatibility evaluation and explores potential future directions for polymeric composites in denture applications. The review finds that adding nanoparticles significantly improves performance compared to unmodified resins, and properties can be extensively enhanced through specific modifications, particularly silanized nanoparticles. Optimizing 3D-printed denture acrylics requires a multifaceted approach, with future research prioritizing novel nanomaterials and surface modification techniques for a novel generation of superior performance, esthetically pleasing, and long-lasting dentures.

Effect of nanomodified 3D printed photopolymerizable resin on flexural strength, color, and antimicrobial efficacy: An in vitro study

STATEMENT OF PROBLEM

Three-dimensional (3D) printing has become popular in dentistry, but studies on the influence of incorporating organic and inorganic nanofillers on 3D printed materials are lacking.

PURPOSE

The purpose of this in vitro study was to assess the flexural strength, color, and antimicrobial efficacy of 3D printed photopolymerizable resin upon adding titanium dioxide nanoparticles (TiO2 NPs) and silanized chitosan nanoparticles (sCS NPs).

MATERIAL AND METHODS

A stereolithographic material (VarseoSmile Crown plus; Bego) was used as a control group (VSC resin), and 3 nanocomposite resin groups were prepared by adding nanoparticles as follow: titanium dioxide group (VSC resin + 0.4% wt. TiO2 NPs), chitosan group (VSC resin + 0.4% wt. sCS NPs), and hybrid group (VSC resin + 0.2% wt. TiO2 NPs + 0.2% wt. sCS NPs). A total of 132 specimens were designed by using a free computer-aided design software program, printed, postpolymerized, and divided into 4 groups. The nanocomposite resins were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR). Bar shaped specimens (n=44) were tested for 3-point flexural strength using a universal testing machine followed by the color measurement of disk-shaped specimens (n=44) with a spectrophotometer. Antimicrobial capacity was measured with Streptococcus mutans, and absorbance was measured using a microplate reader (n=44). Statistical assessments were made with 1-way ANOVA followed by the Tukey post hoc test with Bonferroni adjustment (α=.05).

RESULTS

The hybrid group recorded the highest mean value of flexural strength 135.51 MPa, showing a significant difference compared with that of the control group (P=.022). Regarding color, the mean ∆E00 for titanium was 1.18, for chitosan was 4.26, and for the hybrid group was 3.23 (P<.001). The optical density of the chitosan (2.42) was significantly higher than that of the titanium 1.36 (P=.007) and that of the control 1.63 (P=.042).

CONCLUSIONS

The incorporation of nanofillers resulted in an increase in flexural strength, but it adversely affected the color of nanocomposite resins. Antimicrobial efficacy was improved by incorporating titanium nanofillers.

The Synergistic Effect of High Intensity Focused Ultrasound on In-vitro Remineralization of Tooth Enamel by Calcium Phosphate Ion Clusters

Background

Remineralization of dental enamel is an important intervention strategy for the treatment of demineralized lesions. Existing approaches have limitations such as failure to adequately reproduce both the ideal structural and mechanical properties of the native tooth. The ability of ultrasound to control and accelerate the crystallization processes has been widely reported. Therefore, a new approach was explored for in-vitro enamel remineralization involving the synergistic effect of high-intensity focused ultrasound (HIFU) coupled with calcium phosphate ion clusters (CPICs).

Methods

The demineralized enamel was treated with CPICs, with or without subsequent HIFU exposure for different periods (2.5, 5, and 10 min). The specimens were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. The surface hardness and crystallographic properties of the treated specimens were evaluated using Vickers microhardness testing and X-ray diffraction (XRD), respectively.

Results

SEM revealed distinct, organized, and well-defined prismatic structures, showing clear evidence of remineralization in the combined CPIC/HIFU treatment groups. AFM further revealed a decrease in the surface roughness values with increasing HIFU exposure time up to 5 min, reflecting the obliteration of interprismatic spaces created during demineralization. The characteristic Raman band at 960 cm-1 associated with the inorganic phase of enamel dominated well in the HIFU-treated specimens. Importantly, microhardness testing further demonstrated that new mineral growth also recovered the mechanical properties of the enamel in the HIFU-exposed groups. Critical to our aspirations for developing this into a clinical process, these results were achieved in only 5 min.

Conclusion

HIFU exposure can synergise and significantly accelerate in-vitro enamel remineralization process via calcium phosphate ion clusters. Therefore, this synergistic approach has the potential for use in future clinical interventions.

Silver vanadate nanomaterial incorporated into heat-cured resin and coating in printed resin - Antimicrobial activity in two multi-species biofilms and wettability

OBJECTIVES

To incorporate the nanostructured silver vanadate decorated with silver nanoparticles (AgVO3) into denture base materials: heat-cured (HC) and 3D printed (3DP) resins, at concentrations of 2.5 %, 5 %, and 10 %; and to evaluate the antimicrobial activity in two multi-species biofilm: (1) Candida albicans, Candida glabrata, and Streptococcus mutans, (2) Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus, and the wettability.

METHODS

The AgVO3 was added to the HC powder, and printed samples were coated with 3DP with AgVO3 incorporated. After biofilm formation, the antimicrobial activity was evaluated by colony forming units per milliliter (CFU/mL), metabolic activity, and epifluorescence microscopy. Wettability was assessed by the contact angles with water and artificial saliva.

RESULTS

In biofilm (1), HC-5 % and HC-10 % showed activity against S. mutans, HC-10 % against C. glabrata, and HC-10 % and 3DP-10 % had higher CFU/mL of C. albicans. 3DP-5 % had lower metabolic activity than the 3DP control. In biofilm (2), HC-10 % reduced S. aureus and P. aeruginosa, and HC-5 %, 3DP-2.5 %, and 3DP-5 % reduced S. aureus. 3DP incorporated with AgVO3, HC-5 %, and HC-10 % reduced biofilm (2) metabolic activity. 3DP-5 % and 3DP-10 % increased wettability with water and saliva.

CONCLUSION

HC-10 % was effective against C. glabrata, S. mutans, P. aeruginosa, and S. aureus, and HC-5 % reduced S. mutans and S. aureus. For 3DP, 2.5 % and 5 % reduced S. aureus. The incorporation of AgVO3 into both resins reduced the metabolic activity of biofilms but had no effect on C. albicans. The wettability of the 3DP with water and saliva increased with the addition of AgVO3.

CLINICAL SIGNIFICANCE

The incorporation of silver vanadate into the denture base materials provides antimicrobial efficacy and can prevent the aggravation of oral and systemic diseases. The incorporation of nanomaterials into printed resins is challenging and the coating is an alternative to obtain the inner denture base with antimicrobial effect.

Incorporating versus coating antimicrobials for polymethyl methacrylate: A systematic review

STATEMENT OF PROBLEM

Incorporating and coating with antimicrobials are techniques that can confer antimicrobial action on polymethyl methacrylate (PMMA) denture bases, which can accumulate microorganisms and promote oral and systemic disease.

PURPOSE

The purpose of this systematic review was to answer the question: "Do techniques for incorporating and coating antimicrobial agents in PMMA promote antimicrobial action?"

MATERIAL AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist guidelines were followed, and the SCOPUS, PubMed/Medline, EMBASE, and Science Direct databases searched. The studies were selected in 2 stages, reading the titles and abstracts and then reading the selected studies in full. The risk of bias was analyzed by adapting the quasi-experimental studies tool by the Joanna Briggs Institute (JBI).

RESULTS

A total of 970 articles were found in the databases; 71 were duplicates and, after reading the abstracts, 38 were selected for full reading. From these, 6 were excluded because they did not fulfill the inclusion criteria, and 32 studies were included in this review. Autopolymerizing, heat- polymerizing, and light-polymerizing resins were evaluated, with the incorporating technique prevailing over the coating, but both techniques effectively promoted antimicrobial activity.

CONCLUSIONS

Incorporating and coating antimicrobial agents are effective methods of promoting antimicrobial activity in PMMA. Combining the 2 methods led to increased antimicrobial activity compared with each individually.

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.

The Impact of Technology Teaching in the Dental Predoctoral Curriculum on Students' Perception of Digital Dentistry

The goal was to assess dental students' perception of digital technologies after participating in a CAD/CAM exercise for scanning, designing, and manufacturing computer-aided provisional fixed dental restorations. A survey was conducted among second- (pre-D2 and post-D2), first- (D1, negative control), third-, and fourth-year dental students (D3 and D4, positive controls). Only OSU College of Dentistry students who completed the activity and completed the surveys were included. Seven questions were rated, which evaluated changes in knowledge, skill, interest, the importance of technology availability in an office, patients' perception of technology, the importance of having the technology, and the expected frequency of clinics utilizing the technology. Statistical analysis was performed with a significance level of 0.05. A total of 74 pre-D2 and 77 post-D2 questionnaires were completed. Additionally, 63 D1, 43 D3, and 39 D4 participants responded to the survey. Significant differences were found for "knowledge" and "skill" between the pre-D2 and post-D2 and pre-D2 and control groups (p < 0.001). There was a significant difference between the post-D2 participants and all the controls in terms of "interest" (p = 0.0127) and preference for in-practice technology availability (p < 0.05). There were significant results between the post-D2 participants and all the controls regarding the importance of technology availability in an office (p < 0.001) and the expected frequency of clinics utilizing the technology (p = 0.01). No significance was found for "value of technology to patients" and "the importance of having the technology". The presence of technology in practice and in educational academic environments significantly improved students' interest and perception of their knowledge and skill.

Biocompatibility and biofilm formation on conventional and CAD/CAM provisional implant restorations

Dental implant treatment is a complex and sophisticated process, and implant provisional restorations play a vital role in ensuring its success. The advent of computer-aided design and computer-aided manufacturing (CAD/CAM) technology has revolutionized the field of implant restorations by providing improved precision leading to a reduction in chair time and more predictable treatment outcomes. This technology offers a promising solution to the drawbacks of conventional methods and has the potential to transform the way implant procedures are approached. Despite the clear advantages of CAD/CAM over conventional provisional implant restorations including higher accuracy of fit and superior mechanical properties, little research has been conducted on the biological aspect of these novel restorations. This study aims to fill that gap, comprehensively assessing the biocompatibility, gingival tissue attachment and biofilm formation of a range of provisional implant restorations using CAD/CAM technology through milling and 3-D printing processes compared to conventional fabrication. The biocompatibility of the tested restorations was assessed by MTT assay, Calcein-AM assay as well as SEM analysis. The surface roughness of the tested samples was evaluated, alongside the attachment of Human Gingival Fibroblasts (HGF) cells as well as biofilm formation, and estimated Porphyromonas gingivalis (P. gingivalis) cell count from DNA detection.The results showed all tested provisional implant restorations were non-toxic and good HGF cell attachment but differed in their quantity of biofilm formation, with surface texture influenced by the material and fabrication technique, playing a role. Within the limitation of this study, the findings suggest that CAD/CAM-fabricated provisional implant restorations using a milling technique may be the most favourable among tested groups in terms of biocompatibility and periodontal-related biofilm formation.

Physical and mechanical properties of four 3D-printed resins at two different thick layers: An in vitro comparative study

OBJECTIVES

This in vitro comparative study aimed to evaluate the physical and mechanical properties of four 3D-printed resins with two different thickness layers.

METHODS

Four printed resins (VarseoSmile Crown Plus, VSC; NexDent C&B MFH, MFH; Nanolab 3D, NNL; and Resilab 3D Temp, RSL) were printed with 50 µm and 100 µm layer thickness, resulting in 80 bars measuring 25 × 2×2 mm. The specimens underwent a Raman spectroscopy for degree of conversion, confocal laser scanning microscopy for surface roughness (Sa), three-point bending test for flexural strength and elastic modulus, and a Vickers hardness test (VHN). Data was tested for normality using the Shapiro-Wilk, two-way ANOVA, and Tukey test (α = 0.05) for statistical analysis.

RESULTS

The layer thickness affected all performed tests, but the elastic modulus (p < 0.001). Specimens with 100 µm showed, in general, worse results outcomes than those with 50 µm (p < 0.001). However, within the limitations of this comparative in vitro study, it could be concluded that the tested resins and layer thicknesses directly influenced physical and mechanical properties.

SIGNIFICANCE

The physical and mechanical properties of three-dimensional printed restorations can be affected by the layer thickness, which can interfere with the choice of the 3D printing resin for a desired clinical outcome.

Recent Progress and Trends in the Development of Electrospun and 3D Printed Polymeric-Based Materials to Overcome Antimicrobial Resistance (AMR)

Antimicrobial resistance (AMR) developed by microorganisms is considered one of the most critical public health issues worldwide. This problem is affecting the lives of millions of people and needs to be addressed promptly. Mainly, antibiotics are the substances that contribute to AMR in various strains of bacteria and other microorganisms, leading to infectious diseases that cannot be effectively treated. To avoid the use of antibiotics and similar drugs, several approaches have gained attention in the fields of materials science and engineering as well as pharmaceutics over the past five years. Our focus lies on the design and manufacture of polymeric-based materials capable of incorporating antimicrobial agents excluding the aforementioned substances. In this sense, two of the emerging techniques for materials fabrication, namely, electrospinning and 3D printing, have gained significant attraction. In this article, we provide a summary of the most important findings that contribute to the development of antimicrobial systems using these technologies to incorporate various types of nanomaterials, organic molecules, or natural compounds with the required property. Furthermore, we discuss and consider the challenges that lie ahead in this research field for the coming years.

Biomedical Applications of Zirconia-Based Nanomaterials: Challenges and Future Perspectives

ZrO₂ nanoparticles have received substantially increased attention in every field of life owing to their wide range of applications. Zirconium oxide is a commercially economical, non-hazardous, and sustainable metal oxide having diversified potential applications. ZrO₂ NPs play a vast role in the domain of medicine and pharmacy such as anticancer, antibacterial, and antioxidant agents and tissue engineering owing to their reliable curative biomedical applications. In this review article, we address all of the medical and biomedical applications of ZrO₂ NPs prepared through various approaches in a critical way. ZrO₂ is a bio-ceramic substance that has received increased attention in biomimetic scaffolds owing to its high mechanical strength, excellent biocompatibility, and high chemical stability. ZrO₂ NPs have demonstrated potential anticancer activity against various cancer cells. ZrO₂-based nanomaterials have exhibited potential antibacterial activity against various bacterial strains and have also demonstrated excellent antioxidant activity. The ZrO₂ nanocomposite also exhibits highly sensitive biosensing activity toward the sensing of glucose and other biological species.

The Effect of Nano Zirconium Dioxide (ZrO2)-Optimized Content in Polyamide 12 (PA12) and Polylactic Acid (PLA) Matrices on Their Thermomechanical Response in 3D Printing

The influence of nanoparticles (NPs) in zirconium oxide (ZrO₂) as a strengthening factor of Polylactic Acid (PLA) and Polyamide 12 (PA12) thermoplastics in material extrusion (MEX) additive manufacturing (AM) is reported herein for the first time. Using a melt-mixing compounding method, zirconium dioxide nanoparticles were added at four distinct filler loadings. Additionally, 3D-printed samples were carefully examined for their material performance in various standardized tests. The unfilled polymers were the control samples. The nature of the materials was demonstrated by Raman spectroscopy and thermogravimetric studies. Atomic Force Microscopy and Scanning Electron Microscopy were used to comprehensively analyze their morphological characteristics. Zirconium dioxide NPs showed an affirmative reinforcement tool at all filler concentrations, while the optimized material was calculated with loading in the range of 1.0-3.0 wt.% (3.0 wt.% for PA12, 47.7% increase in strength; 1.0 wt.% for PLA, 20.1% increase in strength). PA12 and PLA polymers with zirconium dioxide in the form of nanocomposite filaments for 3D printing applications could be used in implementations using thermoplastic materials in engineering structures with improved mechanical behavior.

The Clinical Potential of 3D-Printed Crowns Reinforced with Zirconia and Glass Silica Microfillers

The development of 3D-printed crown resin materials with improved mechanical and physical properties is an area of growing interest in dentistry. This study aimed to develop a 3D-printed crown resin material modified with zirconia glass (ZG) and glass silica (GS) microfillers to enhance overall mechanical and physical properties. A total of 125 specimens were created and divided into five groups: control unmodified resin, 5% either ZG or GS reinforced 3D-printed resin, and 10% either ZG or GS reinforced 3D-printed resin. The fracture resistance, surface roughness, and translucency parameter were measured, and fractured crowns were studied under a scanning electron microscope. The results showed that 3D-printed parts that were strengthened with ZG and GS microfillers demonstrated comparable mechanical performance to unmodified crown resin but resulted in greater surface roughness, and only the group that contained 5% ZG showed an increase in translucency. However, it should be noted that increased surface roughness may impact the aesthetics of the crowns, and further optimisation of microfillers concentrations may be necessary. These findings suggest that the newly developed dental-based resins that incorporate microfillers could be suitable for clinical applications, but further studies are necessary to optimise the nanoparticle concentrations and investigate their long-term clinical outcomes.

Current and prospective therapeutic strategies: tackling Candida albicans and Streptococcus mutans cross-kingdom biofilm

Candida albicans (C. albicans) is the most frequent strain associated with cross-kingdom infections in the oral cavity. Clinical evidence shows the co-existence of Streptococcus mutans (S. mutans) and C. albicans in the carious lesions especially in children with early childhood caries (ECC) and demonstrates the close interaction between them. During the interaction, both S. mutans and C. albicans have evolved a complex network of regulatory mechanisms to boost cariogenic virulence and modulate tolerance upon stress changes in the external environment. The intricate relationship and unpredictable consequences pose great therapeutic challenges in clinics, which indicate the demand for de novo emergence of potential antimicrobial therapy with multi-targets or combinatorial therapies. In this article, we present an overview of the clinical significance, and cooperative network of the cross-kingdom interaction between S. mutans and C. albicans. Furthermore, we also summarize the current strategies for targeting cross-kingdom biofilm.

Antifungal efficiency and cytocompatibility of polymethyl methacrylate modified with zinc dimethacrylate

Objectives

Considering the high incidence rates of denture stomatitis, research that providing dental biomaterials with antifungal property are essential for clinical dentistry. The objectives of the present study were to investigate the effect of zinc dimethacrylate (ZDMA) modification on the antifungal and cytotoxic properties, as well as the variance in surface characteristics and other physicochemical properties of polymethyl methacrylate (PMMA) denture base resin.

Methods

PMMA with various mass fraction of ZDMA (1 wt%, 2.5 wt% and 5 wt%) were prepared for experimental groups, and unmodified PMMA for the control. Fourier-transform infrared spectroscopy (FTIR) was applied for characterization. Thermogravimetric analysis, atomic force microscopy and water contact angle were performed to investigate the thermal stability and surface characteristics (n=5). Antifungal capacities and cytocompatibility were evaluated with Candida albicans (C. albicans) and human oral fibroblasts (HGFs), respectively. Colony-forming unit counting, crystal violet assay, live/dead biofilm staining and scanning electron microscopy observation were performed to assess antifungal effects, and the detection of intracellular reactive oxygen species production was applied to explore the possible antimicrobial mechanism. Finally, the cytotoxicity of ZDMA modified PMMA resin was evaluated by the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay and live/dead double staining.

Results

The FTIR analyses confirmed some variation in chemical bonding and physical blend of the composites. Incorporation of ZDMA significantly enhanced the thermal stability and hydrophilicity compared with unmodified PMMA (p < 0.05). The surface roughness increased with the addition of ZDMA while remained below the suggested threshold (≤ 0.2 µm). The antifungal activity significantly improved with ZDMA incorporation, and cytocompatibility assays indicated no obvious cytotoxicity on HGFs.

Conclusions

In the present study, the ZDMA mass fraction up to 5 wt% in PMMA performed better thermal stability, and an increase in surface roughness and hydrophilicity without enhancing microbial adhesion. Moreover, the ZDMA modified PMMA showed effective antifungal activity without inducing any cellular side effects.

Photocatalytic Organic Contaminant Degradation of Green Synthesized ZrO2 NPs and Their Antibacterial Activities

The green synthesis of metal oxide nanoparticles is an efficient, simple, and chemical-free method of producing nanoparticles. The present work reports the synthesis of Murraya koenigii-mediated ZrO2 nanoparticles (ZrO2 NPs) and their applications as a photocatalyst and antibacterial agent. Capping and stabilization of metal oxide nanoparticles were achieved by using Murraya koenigii leaf extract. The optical, structural, and morphological valance of the ZrO2 NPs were characterized using UV-DRS, FTIR, XRD, and FESEM with EDX, TEM, and XPS. An XRD analysis determined that ZrO2 NPs have a monoclinic structure and a crystallite size of 24 nm. TEM and FESEM morphological images confirm the spherical nature of ZrO2 NPs, and their distributions on surfaces show lower agglomerations. ZrO2 NPs showed high optical absorbance in the UV region and a wide bandgap indicating surface oxygen vacancies and charge carriers. The presence of Zr and O elements and their O=Zr=O bonds was categorized using EDX and FTIR spectroscopy. The plant molecules’ interface, bonding, binding energy, and their existence on the surface of ZrO2 NPs were established from XPS analysis. The photocatalytic degradation of methylene blue using ZrO2 NPs was examined under visible light irradiation. The 94% degradation of toxic MB dye was achieved within 20 min. The antibacterial inhibition of ZrO2 NPs was tested against S. aureus and E. coli pathogens. Applications of bio-synthesized ZrO2 NPs including organic substance removal, pathogenic inhibitor development, catalysis, optical, and biomedical development were explored.

Metal Nanoparticles to Combat Candida albicans Infections: An Update

Candidiasis is an opportunistic mycosis with high annual incidence worldwide. In these infections, Candida albicans is the chief pathogen owing to its multiple virulence factors. C. albicans infections are usually treated with azoles, polyenes and echinocandins. However, these antifungals may have limitations regarding toxicity, relapse of infections, high cost, and emergence of antifungal resistance. Thus, the development of nanocarrier systems, such as metal nanoparticles, has been widely investigated. Metal nanoparticles are particulate dispersions or solid particles 10-100 nm in size, with unique physical and chemical properties that make them useful in biomedical applications. In this review, we focus on the activity of silver, gold, and iron nanoparticles against C. albicans. We discuss the use of metal nanoparticles as delivery vehicles for antifungal drugs or natural compounds to increase their biocompatibility and effectiveness. Promisingly, most of these nanoparticles exhibit potential antifungal activity through multi-target mechanisms in C. albicans cells and biofilms, which can minimize the emergence of antifungal resistance. The cytotoxicity of metal nanoparticles is a concern, and adjustments in synthesis approaches or coating techniques have been addressed to overcome these limitations, with great emphasis on green synthesis.

Influence of CAD/CAM Milling and 3D-Printing Fabrication Methods on the Mechanical Properties of 3-Unit Interim Fixed Dental Prosthesis after Thermo-Mechanical Aging Process

This study assessed the influence of CAD/CAM milling and 3D-printing fabrication methods on mechanical properties of 3-unit interim fixed dental prosthesis (IFDPs) after thermo-mechanical aging. Forty 3-unit IFDPs were fabricated on a mandibular right second premolar and second molar of a typodont cast. Samples were fabricated from the following materials; auto-polymerized polymethyl methacrylate (conventional resin), CAD/CAM PMMA (milled resin) and two different CAD/CAM 3D-printed composite resins; digital light processing Asiga (DLP AS) and stereolithography NextDent (SLA ND). Mechanical properties were compared between the studied materials using Kruskal−Wallis test, followed by multiple pairwise comparisons using Bonferroni adjusted significance. There was a significant difference in flexural strength and microhardness between the studied materials (p < 0.001), with the highest mean ± SD reported in the milled IFDPs (174.42 ± 3.39, 27.13 ± 0.52), and the lowest in the conventional IFDPs (98.02 ± 6.1, 15.77 ± 0.32). Flexural strengths differed significantly between the conventional IFDPs and all materials except DLP AS. The highest elastic modulus was recorded in the milled group, and the lowest in the SLA ND group (p = 0.02). In conclusion, superior flexural strength, elastic modulus, and hardness were reported for milled IFDPs. SLA ND printed IFDPs showed comparable mechanical properties to milled ones except for the elastic modulus.

Silver-loaded mesoporous silica nanoparticles enhanced the mechanical and antimicrobial properties of 3D printed denture base resin

The aim of this study is to develop a novel 3D printed denture base resin material modified with mesoporous silica nanocarrier loaded with silver (Ag/MSN) to enhance mechanical and antimicrobial properties. Acrylate resin-based was incorporated with various proportion of Ag/MSN (0.0-2.0 wt%). Specimens with different geometry were printed and characterized accordingly for the effect of modification on properties such as: mechanical and physical properties, chemical composition and degree of conversion, as well as biological response in term of biocompatibility and antimicrobial against oral fibroblast and candida biofilm (C. albicans), respectively. The consecutive addition of Ag/MSN improved significantly surface hardness and crack propagation resistance, while flexural strength remained similar to control; however, a negligible decrease was observed with higher concentrations ≥1 wt%. No significant difference was noticed with water sorption, while water solubility had a remarkable trend of reduction associated with filler content. The surface roughness significantly increased when concentration of Ag/MSN was ≥1.0 wt%. A significant reduction in C. albicans biofilm mass, as the inhibition proficiency was correlated with the proportion of the filler. With respect to the amount of Ag/MSN, the modification was compatible toward fibroblast cells. The sequential addition of Ag/MSN enhanced significantly the mechanical and antimicrobial properties of the 3D printed resin-based material without affecting adversely compatibility. The acrylic resin denture base material has susceptibility of microbial adhesion which limits its application. Silver loaded MSN showed a significant performance to enhance antimicrobial activity against C. albicans which is the main cause of denture stomatitis. The proposed invention is a promise technique for clinical application to provide an advanced prosthesis fabrication and serve as long-term drug delivery.