Ceria-Incorporated Biopolymer for Preventing Fungal Adhesion.

Although biopolymers are widely used in biomedical fields, the issue of poor antimicrobial properties remains unsolved, leading to a potential increase in infections. Here, ceria nanoparticles (CNPs) were incorporated into a representative biopolymer, poly(methyl methacrylate) (PMMA), for drug-free antimicrobial properties. After characterizing the CNPs and surface/mechanical properties of the CNP-PMMA nanocomposite, antiadhesive effects against Candida albicans, the most common fungal species responsible for fungal infections, were determined using metabolic activity assays, and the underlying microbial antiadhesive mechanism was revealed. Hydrothermally fabricated CNPs showed a size of ∼20 nm with a zeta potential of 12 ± 2.3 mV and showed catalytic properties as a ROS modulator. Successful incorporation of CNPs into PMMA up to 2 wt % was confirmed by EDS analysis. The surface roughness and mechanical properties such as flexural strength and modulus were relatively unchanged up to 2 wt %. In contrast, the surface energy increased, and the Vickers hardness decreased in the 2 wt % PMMA compared with the control. A drop of up to 90% of adherent Candida albicans was observed in CNP-incorporated PMMA, which was confirmed and quantified via fungus staining images. The antiadhesive mechanism was revealed from the direct antimicrobial effects of CNP via the upregulation of the intracellular ROS level. Taken together, the antimicrobial-adhesive properties of the CNP-PMMA nanocomposite suggest the potential usefulness of CNP as a promising drug-free antimicrobial ingredient for biopolymers, which could lead to the prevention of microbial-induced complications in clinical settings.

Carbon nanotube incorporation in PMMA to prevent microbial adhesion.

Although PMMA-based biomaterials are widely used in clinics, a major hurdle, namely, their poor antimicrobial (i.e., adhesion) properties, remains and can accelerate infections. In this study, carboxylated multiwalled carbon nanotubes (CNTs) were incorporated into poly(methyl methacrylate) (PMMA) to achieve drug-free antimicrobial adhesion properties. After characterizing the mechanical/surface properties, the anti-adhesive effects against 3 different oral microbial species (Staphylococcus aureus, Streptococcus mutans, and Candida albicans) were determined for roughened and highly polished surfaces using metabolic activity assays and staining for recognizing adherent cells. Carboxylated multiwalled CNTs were fabricated and incorporated into PMMA. Total fracture work was enhanced for composites containing 1 and 2% CNTs, while other mechanical properties were gradually compromised with the increase in the amount of CNTs incorporated. However, the surface roughness and water contact angle increased with increasing CNT incorporation. Significant anti-adhesive effects (35~95%) against 3 different oral microbial species without cytotoxicity to oral keratinocytes were observed for the 1% CNT group compared to the PMMA control group, which was confirmed by microorganism staining. The anti-adhesive mechanism was revealed as a disconnection of sequential microbe chains. The drug-free antimicrobial adhesion properties observed in the CNT-PMMA composite suggest the potential utility of CNT composites as future antimicrobial biomaterials for preventing microbial-induced complications in clinical settings (i.e., Candidiasis).

Nano-graphene oxide incorporated into PMMA resin to prevent microbial adhesion.

OBJECTIVE: Although polymethyl methacrylate (PMMA) is widely used as a dental material, a major challenge of using this substance is its poor antimicrobial (anti-adhesion) effects, which increase oral infections. Here, graphene-oxide nanosheets (nGO) were incorporated into PMMA to introduce sustained antimicrobial-adhesive effects by increasing the hydrophilicity of PMMA. METHODS: After characterizing nGO and nGO-incorporated PMMA (up to 2wt%) in terms of morphology and surface characteristics, 3-point flexural strength and hardness were evaluated. The anti-adhesive effects were determined for 4 different microbial species with experimental specimens and the underlying anti-adhesive mechanism was investigated by a non-thermal oxygen plasma treatment. Sustained antimicrobial-adhesive effects were characterized with incubation in artificial saliva for up to 28 days. RESULTS: The typical nanosheet morphology was observed for nGO. Incorporating nGO into PMMA roughened its surface and increased its hydrophilicity without compromising flexural strength or surface hardness. An anti-adhesive effect after 1h of exposure to microbial species in artificial saliva was observed in nGO-incorporated specimens, which accelerated with increasing levels of nGO without significant cytotoxicity to oral keratinocytes. Plasma treatment of native PMMA demonstrated that the antimicrobial-adhesive effects of nGO incorporation were at least partially due to increased hydrophilicity, not changes in the surface roughness. A sustained antimicrobial-adhesive property against Candida albicans was observed in 2% nGO for up to 28 days. SIGNIFICANCE: The presence of sustained anti-adhesion properties in nGO-incorporated PMMA without loading any antimicrobial drugs suggests the potential usefulness of this compound as a promising antimicrobial dental material for dentures, orthodontic devices and provisional restorative materials.

Rechargeable microbial anti-adhesive polymethyl methacrylate incorporating silver sulfadiazine-loaded mesoporous silica nanocarriers.

OBJECTIVES: Even though polymethyl methacrylate (PMMA) resin is widely used as a dental material, it has poor microbial anti-adhesive properties, which accelerates oral infections. In this investigation, silver-sulfadiazine (AgSD)-loaded mesoporous silica nanoparticles (Ag-MSNs) were incorporated into PMMA to introduce long-term microbial anti-adhesive effects and to make PMMA a rechargeable resin. METHODS: After characterization of the Ag-MSNs in terms of their mesoporous characteristics and drug loading capacity, the 3 point flexural test and hardness were evaluated in PMMA incorporating Ag-MSNs (0.5, 1, 2.5 and 5%). Anti-adhesive effects were observed for Candida albicans and Streptococcus oralis with experimental specimens for up to 28days and after recharging with AgSD. RESULTS: A typical spherical morphology and high mesoporosity were observed for the MSNs used for loading AgSD. Incorporation of Ag-MSNs into PMMA (0.5, 1, 2.5 and 5%) sustained its flexural strength but increased its surface hardness. Anti-adhesive effects were observed after 1h of exposure to both microbial species, and the effects accelerated with increasing Ag-MSN incorporation into PMMA. Long-term microbial anti-adhesive effects were observed for up to 14 days, and further long-term (7 days) anti-adhesive effects were observed after reloading the Ag-MSN-incorporated PMMA (aged for 28 days) with AgSD; these effects were largely caused by released silver ions and partially by changes in surface hydrophilicity. No cytotoxicity to keratinocytes was observed. CONCLUSIONS: The improved mechanical properties and the prolonged microbial anti-adhesive effects, which lasted after reloading of the drug, suggest the potential usefulness of Ag-MSN-incorporated PMMA as a microbial anti-adhesive dental material. SIGNIFICANCE: Ag-MSN-incorporated PMMA can be used as a microbial anti-adhesive dental material for dentures, orthodontic devices and provisional restorative materials.

Sol-gel-derived bioactive glass nanoparticle-incorporated glass ionomer cement with or without chitosan for enhanced mechanical and biomineralization properties.

OBJECTIVE: This study investigated the mechanical and in vitro biological properties (in immortalized human dental pulp stem cells (ihDPSCs)) of bioactive glass nanoparticle (BGN)-incorporated glass ionomer cement (GIC) with or without chitosan as a binder. METHODS: After the BGNs were synthesized and characterized, three experimental GICs and a control (conventional GIC) that differed in the additive incorporated into a commercial GIC liquid (Hy-bond, Shofu, Japan) were produced: BG5 (5wt% of BGNs), CL0.5 (0.5wt% of chitosan), and BG5+CL0.5 (5wt% of BGNs and 0.5wt% of chitosan). After the net setting time was determined, weight change and bioactivity were analyzed in simulated body fluid (SBF) at 37°C. Mechanical properties (compressive strength, diametral tensile strength, flexural strength and modulus) were measured according to the incubation time (up to 28 days) in SBF. Cytotoxicity (1day) and biomineralization (14 days), assessed by alizarin red staining, were investigated using an extract from GIC and ihDPSCs. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's post hoc test; p<0.05. RESULTS: BGNs were sol-gel synthesized to be approximately 42nm in diameter with a spherical morphology and amorphous structure. After the bioactivity and suspension ability of the BGNs were confirmed, all the experimental GIC groups had setting times of less than 6min and approximately 1% weight loss after 28days of incubation. In addition, BGNs incorporated into GIC (BG5 and BG5+CL0.5) exhibited surface bioactivity. The mechanical properties were increased in the BGN-incorporated GICs compared to those in the control (p<0.05). Without cytotoxicity, the biomineralization capacity was ranked in the order BG5, BG5+CL0.5, control, and CL0.5 (p<0.05). SIGNIFICANCE: BGN-incorporated GIC showed enhanced mechanical properties such as compressive, diametral tensile and flexural strength as well as in vitro biomineralization properties in ihDPSCs without cytotoxicity. Therefore, the developed BGN-incorporated GIC is a promising restorative dental material, although further in vivo investigation is needed before clinical application.

Development of long-term antimicrobial poly(methyl methacrylate) by incorporating mesoporous silica nanocarriers.

OBJECTIVE: Poly(methyl methacrylate) (PMMA) used as removable denture bases or orthodontic appliances has relatively poor antimicrobial properties, which accelerate oral infection and induce unfavorable odors. Mesoporous silica nanoparticles (MSNs) have been highlighted as a potential additive to overcome this issue because of their drug-loading capacity. Here, we present the long-term antimicrobial effect of MSN-incorporated PMMA with drug-loading capacity. METHODS: After the MSNs were characterized, MSN incorporation into chemically activated PMMA (0.5, 1, 2.5 or 5wt%) relative to the methyl methacrylate powder by mass was fabricated into a rectangular specimen (1.4×3.0×19.0mm) for a 3-point flexural test at a speed of 1mm/min or a disk (∅=11.5mm and d=1.5mm) for investigation of its antimicrobial effects. RESULTS: A typical spherical morphology with a well-ordered mesoporous structure of the MSNs was visualized and is beneficial for loading drugs and combining in matrixes. Among the tested levels of MSN incorporation in PMMA (0.5, 1, 2.5 or 5wt%), only 5wt% decreased the flexural strength (p<0.05), whereas the flexural modulus was not significantly decreased (p>0.05). The surface roughness and surface energy were increased with 2.5wt% or 5wt% incorporation. An anti-adherent effect against Candida albicans and Streptococcus oralis after 1h of attachment was only observed with 2.5 and 5wt% incorporation compared to a lack of MSNs (p<0.05). A long-term antimicrobial effect was observed for 2 weeks with 2.5wt% MSN-incorporated PMMA when amphotericin B was loaded into the MSNs on the PMMA surface. SIGNIFICANCE: The long-term antimicrobial performance after loading amphotericin B into the MSN-incorporated PMMA suggests the potential clinical usefulness of MSN-incorporated PMMA resin.

Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO.

Some weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved.Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements.Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitrorat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC.Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs.Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials.

Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO

AbstractSome weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved.Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements.Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitrorat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC.Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs.Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials.

Development of a novel aluminum-free glass ionomer cement based on magnesium/strontium-silicate glasses.

The effects of strontium substitution for magnesium in a novel aluminum-free multicomponent glass composition for glass ionomer cements (GICs) were investigated. A series of glass compositions were prepared based on SiO2-P2O5-CaO-ZnO-MgO(1-X)-SrOX-CaF2 (X=0, 0.25, 0.5 and 0.75). The mechanical properties of GICs prepared were characterized by compressive strength, flexural strength, flexural modules, and microhardness. Cell proliferation was evaluated indirectly by CCK-8 assay using various dilutions of the cement and rat mesenchyme stem cells. Incorporation of strontium instead of magnesium in the glasses has a significant influence on setting time of the cements and the properties. All mechanical properties of the GICs with SrO substitution at X=0.25 were significantly increased, then gradually decreased with further increase of the amount of strontium substitution in the glass. The GIC at X=0.25, also, showed an improved cell viability at low doses of the cement extracts in comparison with other groups or control without extracts. The results of this study demonstrate that the glass compositions with strontium substitution at low levels can be successfully used to prepare aluminum-free glass ionomer cements for repair and regeneration of hard tissues.

Investigation of the correlation between the different mechanical properties of resin composites.

The aim of this study was to investigate the relationship between the different mechanical properties with the filler fraction of various resin composites. Mechanical properties of eighteen different resin composites were investigated in this study; flexural strength (FS), flexural modulus (FM), fracture toughness (FT), compressive strength (CS), diametral tensile strength (DTS), Barcol hardness (BH), Vickers hardness (HV), and Knoop hardness (HK). The mean values of mechanical properties and the filler fractions (V(f )) obtained from the literature and the manufacturer were analyzed using Pearson's correlation test at p<0.01. The relationships were compared with the data retrieved from previous studies. Strong correlations between Vf and BH/HV/HK and V(f) and FM were evident in the results of the present study and these results were supported by the retrieved data from previous studies. The other relationships between mechanical properties, such as that between FS and FM and between CS and HV were not significant.

Congenitally missing maxillary lateral incisors: treatment.

The 2 major treatment approaches for congenitally missing maxillary lateral incisors are space closure via orthodontic therapy, or space opening to allow prosthodontic replacements either with a fixed prosthesis or single-tooth implant. Both of these treatment approaches can potentially compromise aesthetics, periodontal health, and function. It is essential for an interdisciplinary dental specialty team to establish realistic treatment objectives, communicate the sequence of treatment, interact during treatment, evaluate dental and gingival aesthetics, and position teeth to permit proper prosthetic treatment. If this interdisciplinary approach is used, the aesthetics and long-term dental health of the patient following treatment will be greatly enhanced.