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

Antibiofilm capacity of PMMA surfaces: A review of current knowledge

The emergence of microorganisms resistant to antimicrobial therapies, associated with the decline in the development of new drugs, including antibiotics, antifungals, and antivirals, highlights the need for alternative strategies to combat microorganisms that cause infections, especially multidrug-resistant bacteria. Polymethylmethacrylate (PMMA) is a material widely used in the biomedical field, with uses ranging from surgical implants, bone cements, and dental devices, to laboratory equipment and three-dimensional models for surgical planning. Despite its multiple applications, PMMA has the disadvantage of favoring microbial adhesion, due to the porous nature of the material, associated with poor bond strength, thermal instability and water sorption in the oral environment, which can contribute to infection development. To mitigate this problem, the scientific community is looking to modify PMMA to give it antimicrobial properties. This review presents possible approaches that include changes to the topography of PMMA, creating textured or nanostructured surfaces, and chemical modifications, such as incorporating antimicrobial agents into the PMMA matrix or surface treatments. Both strategies aim to hinder the adhesion and growth of microorganisms. In addition, combining these approaches seeks a synergistic effect and could become a promising mechanism for preventing infections.

Development and characterization of 3D-printed denture base resin composites having self-healing potential

OBJECTIVE

This study aims to develop and characterize 3D-printed denture resin composites containing self-healing polyurea formaldehyde (PUF) microcapsules (TEGDMA as the core healing agent) for arresting microcracks formation and enhancing the mechanical durability of 3D-printed dentures.

METHODS

The PUF microcapsules containing TEGDMA as core material were synthesized in oil-in-water emulsion and characterized for size, surface morphology and thermal stability. 3D-printed denture base resin with 0, 5, 15, and 25 wt% content of the synthesized PUF were printed and evaluated by degree of conversion, surface morphology, topography, surface hardness, flexural strength, fracture toughness, self-healing efficiency, and fluorescent microscopic visualization of the microcracks' self-healing event through the in-situ release of rhodamine B labelled healing agent from ruptured PUF microcapsules inside the resin matrices.

RESULTS

As compared to the control, a slight decrease was observed in the degree of conversion, surface hardness and flexural strength of the 3D-printed denture base composite modified with the PUF microcapsules. Results demonstrated that an increase in the microcapsule content significantly (p ≤ 0.05) enhances the fracture toughness and self-healing efficiency. The HPLC results analysis of the experimental groups demonstrated a controlled release profile of healing agent over time with the maximum release on day 7. The microscopic visualization findings demonstrated the successful encapsulation and intentional triggered release of the rhodamine B. labelled healing agent in the crack plane.

SIGNIFICANCE

The 3D-printed denture base resin composites modified with the PUF microcapsules showed a significant potential for microcrack self-healing and enhanced fracture toughness based on the content (wt%) of microcapsules.

Mechanical and optical properties of additively manufactured denture base resin in different colors modified with antimicrobial substances: An in vitro study

STATEMENT OF PROBLEM

Acrylic denture base resins are subject to colonization by oral and nonoral bacteria, contributing to the onset of denture stomatitis. However, how the addition of antimicrobial substances affects the mechanical and optical properties of additively manufactured denture base resin remains unclear.

PURPOSE

The purpose of this in vitro study was to investigate the surface roughness, color stainability, and flexural strength of antimicrobial-modified, additively manufactured polymethyl methacrylate (PMMA) denture base resin in tooth and gingiva colors.

MATERIAL AND METHODS

Three antibacterial agents, e-poly-L-lysine+ methacryloyloxyethyl phosphorylcholine (e-MP), silver nanoparticles (AG-P), quaternized ammonium monomer (QA-P) synthesized via the reaction of octyl bromide and DMAEMA, were separately incorporated into tooth- or gingiva-colored 3-dimensionally (3D) printable PMMA specimens, simulating an implant-supported overdenture base or the artificial teeth (n=80). Unaltered specimens served as controls. Autopolymerizing acrylic resin was used to attach titanium matrix housings to gingiva-colored specimens. All specimens underwent coffee thermal cycling (CTC) comprising 10 000 cycles between 5 °C and 55 °C, and their color coordinates were measured. Surface roughness, color change (ΔE00), and flexural strength were calculated before and after CTC. The results were analyzed and compared by using ANOVA and the Tukey post hoc test (α=.05).

RESULTS

All antibacterial agent-incorporated specimens showed lower ΔE00 values than the control (P=.001), with eM-P exhibiting the least color change (P=.001). The control group had the highest post-CTC roughness (Ra) values (P<.001), while all test groups demonstrated higher flexural strength than the control (P=.001). CTC had no significant effect on flexural strength (P>.115).

CONCLUSIONS

The addition of antimicrobial agents to 3D printable implant overdenture base resin in tooth and gingiva color affected the materials' surface properties, color stainability, and flexural strength. Smoother surface, lower color stainability, and higher flexural strength were observed with the addition of eM-P.

Antimicrobial Effect of Three Different Nanoparticles-Modified 3D-Printed Denture Resin: An In Vitro Study

Aim

This study aimed to determine the antibacterial effectiveness of adding zirconia nanoparticles (NPs; ZrO2NPs), silver NPs (AgNPs), and titanium dioxide NPs (TiO2NPs) in various concentrations to three-dimensional (3D)-printed denture resin against Candida Albicans, Streptococcus pyogenes, and Staphylococcus aureus, this study was carried out.

Materials and Methods

The antimicrobial efficacy of 150 disk-shaped specimens with a diameter of 15 mm × 2 mm of unmodified (n = 15) and modified (n = 135) 3D-printed denture resin specimens after the addition of silanated ZrO2NPs, AgNPs, or TiO2NPs (n = 45) in varying concentrations (n = 15) of 0.5%, 1%, and 1.5% were compared using three oral bacteria (S.pyogenes, S. aureus, and C. albicans) as test subjects. Antimicrobial activity was tested by disk diffusion methods.

Results

According to the results, when the three tested NPs (ZrO2NPs, AgNPs, and TiO2NPs) were added, the bacterial count significantly decreased compared with the unmodified 3D-printed resin. Additionally, the findings showed that as the concentration of the studied NPs increased, so did their antibacterial activity. At 1.5% and 1% concentrations, the AgNPs' antibacterial activity was negligible. However, the in vitro study's findings showed that, in terms of the kinds of microorganisms studied, there were no appreciable variations between the three tested NPs.

Conclusion

The inclusion of ZrO2NPs, AgNPs, and TiO2NPs significantly had antimicrobial action against (S. pyogenes, S. aureus, and C. albicans).

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.

Antibacterial activity of a silver-incorporated vancomycin-modified mesoporous silica against methicillin-resistant Staphylococcus aureus

Since conventional antibiotics are almost ineffective on methicillin-resistant Staphylococcus aureus (MRSA) strains, designing their antibacterial alternatives is necessary. Besides, the use of vancomycin is applied for specific detection of the bacteria. Silver-incorporated vancomycin-modified mesoporous silica nanoparticles (MSNs@Van@Ag NPs) were designed for detection and treatment of MRSA bacteria. Mesoporous silica nanoparticles (MSNs) were synthesized through the template method, modified with vancomycin, and finally incorporated with silver nanoparticles (Ag NPs). The MSNs@Van@Ag NPs with a homogenously spherical shape, average size of 50-100 nm, surface area of 955.8 m2/g, and thermal stability up to 200°C were successfully characterized. The amount of Ag incorporated into the MSNs@Van@Ag was calculated at 3.9 ppm and the release amount of Ag was received at 2.92 ppm (75%) after 100 h. The in vitro antibacterial susceptibility test showed the MIC of 100 μg mL-1 for MSNs@Van and 50 μg mL-1 for MSNs@Van@Ag, showing in vitro enhanced effect of Ag and vancomycin in the bactericidal process. An in vivo acute pneumonia model was performed and biochemical assays and pathological studies confirmed the nanomedicine's short-term safety for in vivo application. Cytokine assay using ELISA showed that MSN@Van@Ag causes a reduction of pro-inflammatory cytokines and bacterial proliferation leading to alleviation of inflammatory response.

The effect of mesoporous silica doped with silver nanoparticles on glass ionomer cements; physiochemical, mechanical and ion release analysis

BACKGROUND

The purpose of the study was to evaluate the effect of adding mesoporous silica with silver nanoparticles to conventional glass ionomer cements (GIC) on its, physical, chemical, mechanical properties and ion release analysis.

METHODS

Synthesized mesoporous silica with silver nanoparticles were added in 1, 3 and 5% by weight to the liquid component of GIC forming three experimental groups and compared with plain GIC as control group. Physical and chemical characterization were conducted using nano-computerized tomography (NanoCT) and Fourier transform infrared spectroscopy. Surface microhardness, water sorption and solubility were analyzed. Ion release was investigated using Inductive Coupled Plasma-Optical Emission Spectroscopy and High Performance Liquid Chromatography. Statistical analysis between different groups for the set parameters using parametric and non-parametric tests. The results were analysed using one way analysis of variance (p < 0.05).

RESULTS

Synthesized mesoporous silica with silver nanoparticles were of 7.28 ± 5.0 nm in diameter with a spherical morphology. NanoCT revealed less porosities for 3 wt %. Microhardness showed a statistically significant difference for 5 wt% at day 1 and 21 ( p < 0.0001). Water sorption values decreased significantly on day 14 compared to day 7 for control, 1, 3 and 5 wt%. Control specimens showed highest concentration of fluoride release followed by 5, 3 and 1 wt%.

CONCLUSION

Mesoporous silica with silver nanoparticles modified glass ionomer cements showed comparable microhardness to conventional GIC. Ion release was evident from the modified specimens. Silver remained within the GIC for atleast four weeks following incorporation.

Impact of printing layer thickness on the flexural strength of nanocomposite 3D printed resins: An in vitro comparative study

Background

This study evaluated the influence of various printing layer thicknesses with silicon dioxide nanoparticles (SiO2NPs) incorporated as a reinforcement material on the flexural strength of 3D-printed denture base resins.

Material and Methods

Asiga (DentaBASE, Asiga, Erfurt, Germany) and NextDent (Denture 3D+, NextDent B.V., Soesterberg, The Netherlands) 3D-printed resins were modified with different concentrations of SiO2NPs (0.25 % and 0.5 wt%). A total of 180 specimens (bar-shaped, 64 × 10 × 3.3 mm) were fabricated (N = 90/resin). Each resin was subdivided into three groups (n = 30) according to the SiO2NP concentration (0 %, 0.25 %, and 0.5 wt%) Each concentration was divided into three groups (n = 10) according to the printing layer thickness (50 µm, 75 µm, and 100 µm). Specimens were printed according to the manufacturer's instructions and then subjected to 10,000 thermal cycles. A three-point bending test was used to measure the flexural strength (MPa). One-way analysis of variance (ANOVA) and Tukey's post hoc tests were used to analyze the data (α = 0.05).

Results

For both resins, printing layer thicknesses of 50 µm and 75 µm exhibited significantly higher flexural strength than 100 µm (P < 0.001). The 50 µm thickness showed the greatest flexural strength values (81.65 ± 4.77 MPa and 84.59 ± 6.21 MPa for Asiga and NextDent, respectively). The 100 µm thickness showed the lowest flexural strength values (74.35 ± 5.37 and 73.66 ± 5.55 MPa) for Asiga and NextDent, respectively. The flexural strength significantly increased with the addition of SiO2NPs with printing layer thicknesses of 50 µm and 75 µm (P < 0.001), whereas the modified and unmodified groups printed with a 100 µm layer thickness did not differ significantly. Asiga 0.25 %/50 µm and NextDent 0.5 %/50 µm showed the highest flexural strength values (97.32 ± 6.82 MPa and 97.54 ± 7.04 MPa, respectively). Scanning electron microscopy fractured surfaces analysis revealed more lamellae and irregularities with lower printing layer thicknesses and SiO2NP concentrations.

Conclusion

The flexural strength increased with printing layer thicknesses of 50 µm or 75 µm combined with SiO2NP reinforcement.

Biaxial flexural strength of nanoglass and multiwalled carbon nanotubes reinforced 3D-printed denture base resins and their shear bond strength to 3D-printed and acrylic denture teeth

OBJECTIVE

Evaluation of biaxial flexural strength (BFS) of nanoglass (NG) and multiwalled carbon nanotubes (MWCNTs) reinforced 3D-printed denture base resins and their shear bond strength (SBS) to 3D-printed and acrylic denture teeth.

METHODS

Silanized NG and MWCNTs were added to 3D-printed denture base resin to obtain four groups: Control, 0.25 wt% NG, 0.25 wt% MWCNTs, and a combination group with 0.25 wt% of both fillers. All specimens were tested before and after 600 cycles of thermal aging. BFS (n = 88) was tested using disk-shaped specimens (12 ×2 mm) centralized on an O ring in a universal testing machine. Weibull analysis was conducted to assess predictability of failure. SBS (n = 176) was tested for acrylic and 3D-printed denture teeth attached to bar-shaped specimens in a universal testing machine followed by failure mode analysis using stereomicroscope. Two and three-way ANOVA tests followed by Tukey post hoc test were conducted for BFS and SBS. Kruskal-Wallis test compared percent change among groups with subsequent Dunn post hoc test with Bonferroni correction (α = 0.05).

RESULTS

BFS was affected significantly by filler content (P < 0.001) and thermal cycling (P < 0.001), with thermal cycling displaying the uppermost effect (Ƞp2 =0.551). A significant interaction between filler content, thermal cycling, and teeth type was displayed by SBS results (P < 0.001, F=10.340, Ƞp2 =0.162). The highest BFS values belonged to 0.25 % MWCNTs while the highest SBS to printed teeth was displayed by the combination.

SIGNIFICANCE

The combination group displayed higher BFS and SBS to printed teeth compared to control which allows 3D-printed materials to have a long-term clinical success.

Reinforcement of 3D-printed resins for denture base by adding aramid fibers: Effect on mechanical, surface, and optical properties

PURPOSE

The present study evaluated the mechanical, surface, and optical properties of 3D-printed resins for removable prostheses reinforced by the addition of aramid fibers.

MATERIALS AND METHODS

According to ISO 20795-1:2013 standards, specimens were printed using a digital light processing 3D printer and divided into two groups (n = 06/group): 3D-printed resin for denture base as the control group, and a group with the same 3D-printed resin in addition of 5% aramid fibers as the experimental group. Red aramid fibers were chosen for aesthetic characterization. The specimens were evaluated for their mechanical properties, such as elastic modulus (GPa), flexural strength (MPa), and superficial properties by their surface microhardness (KHN), surface roughness (μm), and surface free energy (mJ/m2). Optical properties were evaluated by the color difference (∆E00) between groups. The statistical test chosen after the exploratory analysis of the data was One-way ANOVA followed by Tukey's HSD (α = 0.05).

RESULTS

The results showed statistical differences in elastic modulus (p < 0.0001), flexural strength (p < 0.0001), surface free energy polar variable (p = 0.0322), total surface free energy (p = 0.0344), with higher values for the experimental. Surface hardness and surface roughness showed no statistical difference (p ≥ 0.05). The color difference (∆E00) obtained through the CIEDE2000 calculus was below the perceptibility threshold (≤1.1).

CONCLUSION

Adding aramid fibers to 3D-printed resin for denture bases resulted in better mechanical properties, without major alterations in surface properties. In addition, it is an easy-to-apply choice for mechanical reinforcement and aesthetic characterization, with the expression of small blood vessels in the 3D-printed resin for removable denture bases.

Effectiveness of postprocessing on 3D printed resin biocompatibility in prosthodontics: A systematic review

STATEMENT OF PROBLEM

Additive manufacturing is used in prosthodontics for producing casts, surgical guides, and interim and definitive prostheses. Printed resin components that will be in contact with the oral mucosa must meet biocompatibility requirements in accordance with current standards for medical devices. Despite such approvals being obtained by the manufacturer, the dentist remains responsible for following the manufacturer recommendations. Evidence for the effect of postprocessing 3-dimensionally (3D) printed resin components on biocompatibility is lacking PURPOSE: The purpose of this systematic review was to assess the effectiveness of 3D printing postprocessing on the biocompatibility of resins that will be in contact with the oral mucosa.

MATERIAL AND METHODS

The PubMed, Scopus, and DOSS search engines were used to identify articles. Two independent researchers conducted the systematic review by following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines and by following a combination of keywords.

RESULTS

Of a total of 249 articles, 27 were selected, including only 1 in vivo study. Thirty-two commercially available and a few experimental resins were tested. The main applications were removable denture bases and denture teeth, interim and definitive fixed restorations, occlusal splints, and surgical guides. Postprocessing procedures were those recommended by the manufacturer, experimental, or not implemented and involving alcohol, ultrasonic or centrifugal rinsing, photopolymerization at different UV wavelengths, a nitrated atmosphere chamber with air drying or compressed air drying and with heat treatment. The majority of postprocessed 3D printed resins were reported to be noncytotoxic, implying sufficient biocompatibility.

CONCLUSIONS

The heterogeneity of materials and methods did not allow the identification of an ideal postprocessing protocol or of the need for additional steps after following the manufacturer's recommendations.

Evaluation of microhardness, degree of conversion, and abrasion resistance of nanoglass and multiwalled carbon nanotubes reinforced three-dimensionally printed denture base resins

PURPOSE

To assess the effect of nanoglass (NG) particles and multiwalled carbon nanotubes' (MWCNTs) addition on Vickers hardness (VH), degree of conversion (DC), and abrasion resistance of 3D-printed denture base resin.

MATERIALS AND METHODS

3D-printed denture base resin was reinforced using silanized NG and MWCNTs to obtain four groups: Control, 0.25 wt% NG reinforced resin, 0.25 wt% MWCNTs reinforced resin, and a combination group of 0.25 wt% of both fillers. All specimens (N = 176) were tested before and after thermal aging (600 cycles) for VH (n = 22), DC, and abrasion resistance (n = 22). Abrasion resistance specimens were subjected to 60,000 brushing strokes, and then assessed for surface roughness (Ra) and weight loss. Specimens were then scanned with a benchtop scanner before and after abrasion to produce a color map of topographical changes from superimposed images. Data were analyzed using ANOVA tests followed by Tukey post hoc test. Kruskal-Wallis test was used to compare percent change among groups, followed by Dunn post hoc test (α = 0.05).

RESULTS

The interaction between nanofiller content and thermal cycling displayed a significant effect on VH and DC. The 0.25% NG expressed the highest VH before aging but revealed the highest percent decrease after aging. Nanofiller content, thermal aging, and brushing displayed a significant interaction impact on the Ra values.

CONCLUSIONS

The addition of nanofillers resulted in an overall improvement in resin microhardness and abrasion resistance. The 0.25% MWCNTs group revealed the lowest Ra with the least percent change in VH and DC, while the combination one displayed the least change in weight.

Post-processing of a 3D-printed denture base polymer: Impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity

OBJECTIVES

To investigate the impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity of an additively manufactured denture base polymer.

METHODS

The tested specimens were prepared by digital light processing (DLP). A centrifugation method (CENT) was used to remove the residual uncured resin. In addition, the specimens were post-processed with different post-rinsing solutions: isopropanol (IPA), ethanol (EtOH), and tripropylene glycol monomethyl ether (TPM), respectively. A commercial heat-polymerized polymethyl methacrylate was used as a reference (REF). First, the values of surface topography, arithmetical mean height (Sa), and root mean square height (Sq) were measured. Next, flexural strength (FS) and modulus were evaluated. Finally, cytotoxicity was assessed using an extract test. The data were statistically analyzed using a one-way analysis of variance, followed by Tukey's multiple comparison test for post-hoc analysis.

RESULTS

The Sa value in the CENT group was lower than in the IPA, EtOH, TPM, and REF groups (p < 0.001). Moreover, the CENT group had lower Sq values than other groups (p < 0.001). The centrifugation method showed a higher FS value (80.92 ± 8.65 MPa) than the EtOH (61.71 ± 12.25 MPa, p < 0.001) and TPM (67.01 ± 9.751 MPa, p = 0.027), while affecting IPA (72.26 ± 8.80 MPa, p = 0.268) and REF (71.39 ± 10.44 MPa, p = 0.231). Also, the centrifugation method showed no evident cytotoxic effects.

CONCLUSIONS

The surfaces treated with a centrifugation method were relatively smooth. Simultaneously, the flexural strength of denture base polymers was enhanced through centrifugation. Finally, no evident cytotoxic effects could be observed from different post-processing procedures.

CLINICAL SIGNIFICANCE

The centrifugation method could optimize surface quality and flexural strength of DLP-printed denture base polymers without compromising cytocompatibility, offering an alternative to conventional rinsing post-processing.

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.

Development of an antimicrobial, 3D printable denture base material with K18 quaternary ammonium silane-functionalized methyl methacrylate and filler

STATEMENT OF PROBLEM

Denture base materials are highly susceptible to microbial colonization, which can lead to denture stomatitis. In addition, patients who sleep with their dentures have an increased chance of contracting pneumonia. Commercially available antimicrobial denture base materials to prevent or combat microbial colonization are lacking.

PURPOSE

The purpose of this in vitro study was to determine the effects of K18 quaternary ammonium methacryloxy silane-functionalized filler (K18-Filler) and methyl methacrylate (K18-MMA) on the polymerization of 3D printed denture base material and its esthetic, mechanical, and antimicrobial properties.

MATERIAL AND METHODS

K18-Filler (0%, 10%, 20% w/w) and K18-MMA (0%, 5%, 12.5% w/w) were added to a 3D printable denture base resin (Denture Base Resin, Original Pink; Formlabs Inc) and 3D printed. Specimens were tested by using the Rockwell15T hardness, near infrared FTIR monomer-to-polymer degree of conversion (DoC), transparency parameter (TP), color shift, and 3-point bend and by counting colony forming units against Streptococcus aureus, Streptococcus sanguinis and Candida albicans tests. Data were analyzed using analysis of variance with the Tukey-Kramer HSD post hoc test.

RESULTS

Control resins had significantly higher Rockwell15T hardness than most of the K18 groups (P<.05) but had comparable DoC with all K18 groups except one, showing that all groups were well polymerized. Controls had significantly higher TP than most K18 groups, but most K18 groups had ΔE<3.3, so the color shift was not noticeable. However, the 12.5% K18-MMA with 10% and 20% K18-Filler groups, which were also the groups used to test for antimicrobial activity, had ΔE>8. All K18 groups had comparable or greater moduli than the controls, but the controls had significantly higher ultimate transverse strengths than most K18 groups (P<.05). All 12.5% K18-MMA with K18-Filler groups had significant antimicrobial activity against S. aureus, S. sanguinis, and C. albicans.

CONCLUSIONS

12.5% K18-MMA and K18-Filler produced 3D printable denture materials with comparable polymerization properties and significant antimicrobial properties against S. mutans, S. sanguinis, and C. albicans. High K18-MMA and K18-Filler concentrations caused significant color shifts and reductions in ultimate strengths.

Mapping the research landscape of nanoparticles and their use in denture base resins: a bibliometric analysis

BACKGROUND

Nanoparticles are increasingly used in dentistry for various applications, including enhancing the mechanical properties of denture base resins. This study aimed to comprehensively review and analyze the research landscape of nanoparticles and their effect on the flexural strength of denture base resins to identify key research areas and trends and to highlight the importance of collaboration between authors and institutions.

METHODS

A Bibliometric Analysis was conducted using the Keywords "Nanoparticle*" AND "Denture*" OR "CAD/CAM." The literature search from the WOS database was restricted to the publication years 2011 to 2022.

RESULTS

Key findings encompass an increase in research publications but a decline in citations. Saudi Arabia, China, and Iraq led this research, with specific institutions excelling. Notable journals with high impact factors were identified. Authorship patterns show variations in citation impact. Additionally, keyword analysis revealed that current research trends offer insights into influential authors and their networks.

CONCLUSIONS

The analysis of nanoparticles and denture base resins reveals a dynamic and evolving landscape that emphasizes the importance of collaboration, staying current with research trends, and conducting high-quality research in this ever-evolving domain.

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.

Strategies for Preventing and Treating Oral Mucosal Infections Associated with Removable Dentures: A Scoping Review

Oral infections occur due to contact between biofilm rich in Candida albicans formed on the inner surface of complete dentures and the mucosa. This study investigated historical advances in the prevention and treatment of oral mucosal infection and identified gaps in the literature. Bibliographic research was conducted, looking at PubMed, Embase, Web of Science, and Scopus, where 935 articles were found. After removing duplicates and excluding articles by reading the title and abstract, 131 articles were selected for full reading and 104 articles were included. Another 38 articles were added from the gray literature. This review followed the PRISMA-ScR guidelines. The historical period described ranges from 1969 to 2023, in which, during the 21st century, in vitro and in vivo studies became more common and, from 2010 to 2023, the number of randomized controlled trials increased. Among the various approaches tested are the incorporation of antimicrobial products into prosthetic materials, the improvement of oral and denture hygiene protocols, the development of synthetic and natural products for the chemical control of microorganisms, and intervention with local or systemic antimicrobial agents. Studies report good results with brushing combined with sodium hypochlorite, and new disinfectant solutions and products incorporated into prosthetic materials are promising.

Advances in Nanomaterials and Composites Based on Mesoporous Materials as Antimicrobial Agents: Relevant Applications in Human Health

Nanotechnology has emerged as a cornerstone in contemporary research, marked by the advent of advanced technologies aimed at nanoengineering materials with diverse applications, particularly to address challenges in human health. Among these challenges, antimicrobial resistance (AMR) has risen as a significant and pressing threat to public health, creating obstacles in preventing and treating persistent diseases. Despite efforts in recent decades to combat AMR, global trends indicate an ongoing and concerning increase in AMR. The primary contributors to the escalation of AMR are the misuse and overuse of various antimicrobial agents in healthcare settings. This has led to severe consequences not only in terms of compromised treatment outcomes but also in terms of substantial financial burdens. The economic impact of AMR is reflected in skyrocketing healthcare costs attributed to heightened hospital admissions and increased drug usage. To address this critical issue, it is imperative to implement effective strategies for antimicrobial therapies. This comprehensive review will explore the latest scientific breakthroughs within the metal-organic frameworks and the use of mesoporous metallic oxide derivates as antimicrobial agents. We will explore their biomedical applications in human health, shedding light on promising avenues for combating AMR. Finally, we will conclude the current state of research and offer perspectives on the future development of these nanomaterials in the ongoing battle against AMR.

Synthesis of novel metal silica nanoparticles exhibiting antimicrobial potential and applications to combat periodontitis

Periodontitis is a severe form of gum disease caused by bacterial plaque that affects millions of people and has substantial worldwide health and economic implications. However, current clinical antiseptic and antimicrobial drug therapies are insufficient because they frequently have numerous side effects and contribute to widespread bacterial resistance. Recently, nanotechnology has shown promise in the synthesis of novel periodontal therapeutic materials. Nanoparticles are quickly replacing antibiotics in the treatment of bacterial infections, and their potential application in dentistry is immense. The alarming increases in antimicrobial resistance further emphasize the importance of exploring and utilizing nanotechnology in the fight against tooth diseases particularly periodontitis. We developed 16 different combinations of mesoporous silica nanomaterials in this study by ageing, drying, and calcining them with 11 different metals including silver, zinc, copper, gold, palladium, ruthenium, platinum, nickel, cerium, aluminium, and zirconium. The antibacterial properties of metal-doped silica were evaluated using four distinct susceptibility tests. The agar well diffusion antibacterial activity test, which measured the susceptibility of the microbes being tested, as well as the antibacterial efficacy of mesoporous silica with different silica/metal ratios, were among these studies. The growth kinetics experiment was used to investigate the efficacy of various metal-doped silica nanoparticles on microbial growth. To detect growth inhibitory effects, the colony-forming unit assay was used. Finally, MIC and MBC tests were performed to observe the inhibition of microbial biofilm formation. Our findings show that silver- and zinc-doped silica nanoparticles synthesized using the sol-gel method can be effective antimicrobial agents against periodontitis-causing microbes. This study represents the pioneering work reporting the antimicrobial properties of metal-loaded TUD-1 mesoporous silica, which could be useful in the fight against other infectious diseases too.

Preparation of arginine-loaded mesoporous silica nanoparticles (Arg@MSNs) to improve the mechanical and antibacterial properties of denture base resin

STATEMENT OF PROBLEM

Whether the incorporation of arginine-loaded mesoporous silica nanoparticles (Arg@MSNs) into denture base resin can improve the mechanical and antibacterial properties is unclear.

PURPOSE

The purpose of this in vitro study was to synthesis Arg@MSNs and explore how Arg@MSNs incorporation affects the mechanical and antibacterial properties of denture base resin.

MATERIAL AND METHODS

Arg@MSNs were synthesized via a sol-gel process and characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). The prepared Arg@MSNs at different weight ratio concentrations were added into denture base resin as the experimental group, and unmodified denture base resin was the control. The fracture surface and arginine release behavior of each specimen were detected using scanning electron microscopy (SEM) and ultra-high-performance liquid chromatography-tandem mass spectrometer (UHPLC-HESI-MS/MS), respectively. Three-point bend tests were applied using a universal testing machine for evaluation of the mechanical properties of each group (n=5). Antibacterial efficiency (n=3) was evaluated by both quantitative and qualitative analysis using Streptococcus mutans. The cytotoxic effect of the Arg@MSN-modified denture base resin was investigated using a cell counting kit (CCK)-8 test. Data were subjected to 1-way analysis of variance followed by the post hoc Tukey honestly significant difference test (ɑ=.05).

RESULTS

The prepared Arg@MSNs had good monodispersity and spherical morphology. Arg@MSN concentration at 0.5 wt%, 1 wt%, and 2.5 wt% resulted in enhanced mechanical properties, while those at 5 wt% were adversely impacted. Biofilm pH values increased with the incorporation of Arg@MSNs, and the antibacterial performance was improved. The CCK-8 test revealed that all formulations were not cytotoxic.

CONCLUSIONS

The addition of Arg@MSNs into denture base resin can enhance its mechanical properties and improve its antibacterial performance without any apparent cytotoxic effect.

Potential Applications and Additive Manufacturing Technology-Based Considerations of Mesoporous Silica: A Review

Nanoporous materials are categorized as microporous (pore sizes 0.2-2 nm), mesoporous (pore sizes 2-50 nm), and macroporous (pore sizes 50-1000 nm). Mesoporous silica (MS) has gained a significant interest due to its notable characteristics, including organized pore networks, specific surface areas, and the ability to be integrated in a variety of morphologies. Recently, MS has been widely accepted by range of manufacturer and as drug carrier. Moreover, silica nanoparticles containing mesopores, also known as mesoporous silica nanoparticles (MSNs), have attracted widespread attention in additive manufacturing (AM). AM commonly known as three-dimensional printing is the formalized rapid prototyping (RP) technology. AM techniques, in comparison to conventional methods, aid in reducing the necessity for tooling and allow versatility in product and design customization. There are generally several types of AM processes reported including VAT polymerization (VP), powder bed fusion (PBF), sheet lamination (SL), material extrusion (ME), binder jetting (BJ), direct energy deposition (DED), and material jetting (MJ). Furthermore, AM techniques are utilized in fabrication of various classified fields such as architectural modeling, fuel cell manufacturing, lightweight machines, medical, and fabrication of drug delivery systems. The review concisely elaborates on applications of mesoporous silica as versatile material in fabrication of various AM-based pharmaceutical products with an elaboration on various AM techniques to reduce the knowledge gap.

The effects of nano-silver loaded zirconium phosphate on antibacterial properties, mechanical properties and biosafety of room temperature curing PMMA materials

Polymethyl methacrylate (PMMA) frequently features in dental restorative materials due to its favorable properties. However, its surface exhibits a propensity for bacterial colonization, and the material can fracture under masticatory pressure. This study incorporated commercially available RHA-1F-II nano-silver loaded zirconium phosphate (Ag-ZrP) into room-temperature cured PMMA at varying mass fractions. Various methods were employed to characterize Ag-ZrP. Subsequently, an examination of the effects of Ag-ZrP on the antimicrobial properties, biosafety, and mechanical properties of PMMA materials was conducted. The results indicated that the antibacterial rate against Streptococcus mutans was enhanced at Ag-ZrP additions of 0%wt, 0.5%wt, 1.0%wt, 1.5%wt, 2.0%wt, 2.5%wt, and 3.0%wt, achieving respective rates of 53.53%, 67.08%, 83.23%, 93.38%, 95.85%, and 98.00%. Similarly, the antibacterial rate against Escherichia coli registered at 31.62%, 50.14%, 64.00%, 75.09%, 86.30%, 92.98%. When Ag-ZrP was introduced at amounts ranging from 1.0% to 1.5%, PMMA materials exhibited peak mechanical properties. However, mechanical strength diminished beyond additions of 2.5%wt to 3.0%wt, relative to the 0%wt group, while PMMA demonstrated no notable cytotoxicity below a 3.0%wt dosage. Thus, it is inferred that optimal antimicrobial and mechanical properties of PMMA materials are achieved with nano-Ag-ZrP (RHA-1F-II) additions of 1.5%wt to 2.0%wt, without eliciting cytotoxicity.

Amorphization of Low Soluble Drug with Amino Acids to Improve Its Therapeutic Efficacy: a State-of-Art-Review

Low aqueous solubility of drug candidates is an ongoing challenge and pharmaceutical manufacturers pay close attention to amorphization (AMORP) technology to improve the solubility of drugs that dissolve poorly. Amorphous drug typically exhibits much higher apparent solubility than their crystalline form due to high energy state that enable them to produce a supersaturated state in the gastrointestinal tract and thereby improve bioavailability. The stability and augmented solubility in co-amorphous (COA) formulations is influenced by molecular interactions. COA are excellent carriers-based drug delivery systems for biopharmaceutical classification system (BCS) class II and class IV drugs. The three important critical quality attributes, such as co-formability, physical stability, and dissolution performance, are necessary to illustrate the COA systems. New amorphous-stabilized carriers-based fabrication techniques that improve drug loading and degree of AMORP have been the focus of emerging AMORP technology. Numerous low-molecular-weight compounds, particularly amino acids such as glutamic acid, arginine, isoleucine, leucine, valine, alanine, glycine, etc., have been employed as potential co-formers. The review focus on the prevailing drug AMORP strategies used in pharmaceutical research, including in situ AMORP, COA systems, and mesoporous particle-based methods. Moreover, brief characterization techniques and the application of the different amino acids in stabilization and solubility improvements have been related.

Comparative Evaluation of TiO2 Nanoparticle Addition and Postcuring Time on the Flexural Properties and Hardness of Additively Fabricated Denture Base Resins

Three-dimensionally (3D)-printed fabricated denture bases have shown inferior strength to conventional and subtractively fabricated ones. Several factors could significantly improve the strength of 3D-printed denture base resin, including the addition of nanoparticles and post-curing factors. This study evaluated the effect of TiO2 nanoparticle (TNP) addition and the post-curing time (PCT) on the flexural properties and hardness of three-dimensionally (3D)-printed denture base resins. A total of 360 specimens were fabricated, with 180 specimens from each type of resin. For evaluating the flexural properties, bar-shaped specimens measuring 64 × 10 × 3.3 mm were used, while, for the hardness testing, disc-shaped specimens measuring 15 × 2 mm were employed. The two 3D-printed resins utilized in this study were Asiga (DentaBASE) and NextDent (Vertex Dental B.V). Each resin was modified by adding TNPs at 1% and 2% concentrations, forming two groups and an additional unmodified group. Each group was divided into three subgroups according to the PCT (15, 60, and 90 min). All the specimens were subjected to artificial aging (5000 cycles), followed by testing of the flexural strength and elastic modulus using a universal testing machine, and the hardness using the Vickers hardness test. A three-way ANOVA was used for the data analysis, and a post hoc Tukey's test was used for the pairwise comparisons (α = 0.05). Scanning electron microscopy (SEM) was used for the fracture surface analysis. The addition of the TNPs increased the flexural strength in comparison to the unmodified groups (p < 0.001), while there was no significant difference in the elastic modulus and hardness with the 1% TNP concentration. Among the TNP groups, the 2% TNP concentration significantly decreased the elastic modulus and hardness (p < 0.001). The SEM showed a homogenous distribution of the TNPs, and the more irregular fracture surface displayed ductile fractures. The PCT significantly increased the flexural strength, elastic modulus, and hardness (p < 0.001), and this increase was time-dependent. The three-way ANOVA results revealed a significant difference between the material types, TNP concentrations, and PCT interactions (p < 0.001). Both concentrations of the TNPs increased the flexural strength, while the 2% TNP concentration decreased the elastic modulus and hardness of the 3D-printed nanocomposites. The flexural strength and hardness increased as the PCT increased. The material type, TNP concentration, and PCT are important factors that affect the strength of 3D-printed nanocomposites and could improve their mechanical performance.

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.

Antibacterial and fluorescent clear aligner attachment resin modified with chlorhexidine loaded mesoporous silica nanoparticles and zinc oxide quantum dots

OBJECTIVES

To develop an antibacterial and fluorescent clear aligner attachment resin via the incorporation of chlorhexidine loaded pore-expanded mesoporous silica nanoparticles (CHX@pMSN) and amino-silane functionalized zinc oxide quantum dots (aZnO_QDs), and to evaluate its antibacterial activity, fluorescence capability, esthetic properties, mechanical performance and biocompatibility.

METHODS

CHX@pMSN and aZnO_QDs were incorporated into the commercial resin composites (Filtek Z350 XT, 3M) at different mass fractions, control group: Filtek; fluorescent attachment resin (FAR): Filtek + 3 wt% aZnO_QDs; antibacterial and fluorescent attachment resin (AFAR)-1: Filtek + 3 wt% aZnO_QDs + 1 wt% CHX@pMSN; AFAR-2: Filtek + 3 wt% aZnO_QDs + 3 wt% CHX@pMSN; AFAR-3: Filtek + 3 wt% aZnO_QDs + 5 wt% CHX@pMSN. CHX release, antibacterial activity, fluorescence capability, color change, stain resistance, degree of conversion, depth of cure, polymerization shrinkage, water sorption and solubility, softening in solvent, flexural strength, flexural modulus, shear bond strength, and cytotoxicity were evaluated comprehensively.

RESULTS

CHX could be continuously released from the AFAR groups for up to 30 days. CFU, MTT, lactic acid production, SEM and CLSM evaluation showed AFAR-2 and AFAR-3 could effectively inhibit S. mutans biofilms even after 1-month aging. Only AFAR-3 showed clinically perceptible color change and all the experimental groups were not more susceptible to staining. AFAR-1 and AFAR-2 could suppress polymerization shrinkage and enhance the resistance to degradation without compromising other properties, including degree of conversion, water sorption and solubility, flexural strength, flexural modulus, and shear bond strength. Depth of cure of all the four experimental groups was significantly decreased (p < 0.05) but still within the ISO standard. CCK-8 assay and live/dead cell staining denied the cytotoxicity of experimental resins. Fluorescence intensity tests showed that FAR and AFAR-2 could emit strong yellowish fluorescence under the excitation of ultraviolet for up to six months.

CONCLUSIONS

AFRA-2 possessed long-term antibiofilm activity, strong fluorescence capability and satisfying biocompatibility without compromising esthetic and mechanical properties. This study proposed a new strategy for reducing bacteria accumulation around the attachment, which is also promising in helping orthodontists to remove the attachment thoroughly and precisely.

Changes in mechanical and bacterial properties of denture base resin following nanoceria incorporation with and without SBA-15 carriers

Poly (methyl methacrylate) (PMMA) is a commonly used material for the fabrication of biomedical appliances. Although PMMA has several advantages, it is susceptible to microbial insults with practical use. Therefore, different bioactive nanomaterials, such as nanoceria (CeN), have been proposed to enhance the properties of PMMA. In this study, we investigated the effect of the incorporation of CeN into PMMA with and without the use of mesoporous silica nanoparticle (SBA-15) carriers. The unmodified PMMA specimens (control, CTRL) were compared to groups containing SBA-15, CeN, and the synthesized SBA-15 impregnated with CeN (SBA-15@CeN) at different loading percentages. The mechanical and physical properties of the different SBA-15@CeN groups and their effects on cell viability were investigated, and the optimal CeN concentration was identified accordingly. Our results revealed that flexural strength was significantly (P < 0.01) reduced in the SBA-15@CeN_3× group (containing 3-fold the CeN wt. %). Although the surface microhardness increased with the increase in the wt. % of SBA-15@CeN, cell viability was significantly reduced (P < 0.001). The SBA-15@CeN_1× group had the optimal concentration and displayed significant resistance to single-and multispecies microbial colonization. Finally, the enzymatic activity of CeN was significantly high in the SBA-15@CeN_1× group. The proinflammatory markers (IL-6, IL-1β, TNF-α, CD80, and CD86) showed a significant (P < 0.001) multifold reduction in lipopolysaccharide-induced RAW cells treated with a 5-day eluate of the SBA-15@CeN_1× group. These results indicate that the addition of SBA-15@CeN at 1.5 wt % improves the biological response of PMMA without compromising its mechanical properties.