Effects of antibacterial coating on monomer exudation and the mechanical properties of denture base resins.

STATEMENT OF PROBLEM: Denture base resin may be exposed to different conditions for long periods, resulting in the loss of monomer by exudation and a decrease in mechanical properties. PURPOSE: The purpose of this in vitro study was to evaluate monomer loss by exudation from denture base resins doped with antibacterial coatings and their mechanical properties after long-term water immersion. MATERIAL AND METHODS: Four kinds of dental base resin materials were used as experimental materials. The specimens of each resin were divided into an experimental group (coated) and a control group (uncoated). Monomer exudation was tested at 7 and 28 days by gas chromatography after materials were immersed in distilled water or a solution of 75% alcohol/distilled water. Flexural strength and elastic modulus were tested with a universal testing machine after immersion for 2 and 180 days. The surface morphology was characterized with atomic force microscopy. The data were analyzed using 3-way ANOVA followed by the Tukey-Kramer honest significant difference test (α=.05). RESULTS: In both of the immersion media, each of the 3 factors (materials, coating, and immersion time) significantly affected the monomer exudation (P<.05). In addition, the interaction between any 2 of those factors or among the 3 factors had a significant interaction effect on the monomer exudation of the denture base (P<.05). The mechanical properties of the tested materials were different, and the immersion time had a significant effect on the flexural properties (P<.05). For flexural strength, a significant interaction effect occurred among the 3 factors (material, coating, and immersion time) (P<.05). The coating has a significant effect on the elastic modulus of denture base resin (P<.05) and on the interaction between the material and immersion time (P<.05). CONCLUSIONS: The silver-loaded mesoporous silica antibacterial coating can effectively reduce monomer exudation and enhance the flexural properties of denture base resin after immersion.

Effects of organic-inorganic hybrid coating on the color stability of denture base resins.

STATEMENT OF PROBLEM: Denture base resin may be exposed to different conditions for long periods, resulting in varying degrees of staining, discoloration, and distortion. PURPOSE: The purpose of this in vitro study was to evaluate whether an organic-inorganic hybrid coating for base resins can improve color stability and reduce water absorption and solubility. MATERIAL AND METHODS: An organic-inorganic hybrid coating was prepared, and resin sheets made from 4 types of base resin materials were divided into an experimental group (surface coating) and a control group (without coating). The water absorption and solubility in each group were tested. The resin sheets were immersed in tea, red wine, coffee, and cola. The color change (ΔE values) of resin sheets in different soaking solutions was evaluated at 1, 7, and 28 days. RESULTS: Statistical analysis showed that water absorption and solubility in the experimental group were significantly lower than in the control group (P<.05). The 4 staining solutions (tea, red wine, coffee, and cola) caused base resin discoloration in a time-dependent manner. This staining and discoloration was also influenced by the type of resin material. About 85% of ΔE values in the experimental group were significantly lower than those in the control group (P<.05). At 28 days, almost all ΔE values in the experimental group were significantly lower than those in the control group (P<.05). CONCLUSIONS: The organic-inorganic hybrid coating effectively reduced the water uptake and solubility of base resins and significantly improved the color stability of the denture base.

Enhancing glass-ionomer cements with flake-shaped glass: A new frontier in dental restoration.

This study aims to investigate whether the combined use of thin sheet glass (FSG) and polyurethane acrylate (PUA) can enhance the mechanical properties and biocompatibility of glass ionomer cements (GICs) to improve the overall performance of commercial GICs. In this study, an innovative approach was employed by incorporating diluents and photoinitiators into PUA to develop a novel light-curable PUA material. The PUA was then used to modify the GIC to obtain PUA-modified GIC. Subsequently, physical and chemical methods were employed to corrode and chemically modify the glass fiber surface to acquire dried thin sheet glass (FSG). Different proportions of FSG (10%, 20%, and 30% by mass) were mixed with PUA-GIC to obtain FSG-PUA modified GIC. Mechanical and biocompatibility tests were conducted on regular GIC, PUA-GIC, resin-modified glass ionomer cement (RMGIC), and various proportions of FSG-PUA-GIC materials, including flexural strength, surface hardness, water absorption rate, solubility, shear strength, compressive strength (CS), in vitro cytotoxicity, as well as short-term oral toxicity and subcutaneous implantation trials. A novel FSG-PUA modified GIC was successfully prepared, which not only retained the excellent biocompatibility and fluoride ion release capacity of the original GIC but also significantly enhanced its mechanical strength and durability. The application of this innovative method provides a new direction for the development of dental restorative materials, particularly in addressing the shortcomings of GICs in terms of mechanical performance. The addition of FSG notably increased the flexural strength and surface hardness of GICs, especially at a 20% additive level, demonstrating superior performance compared with standard Fuji IX (F9) and slightly better than RMGIC. Water absorption rate and solubility initially decreased and then increased with an increase in FSG content, and significantly outperformed F9 and RMGIC at 10% and 20% additive levels. Shear strength and CS decreased with an increase in FSG content but remained superior to commercial groups. Material incubation with cells in vitro for 24-48 h showed no significant impact on cell viability, with cell viability exceeding 90%. Short-term oral toxicity tests demonstrated good biocompatibility of the material, and subcutaneous implant trials did not observe any significant inflammation or pathological changes within 12 weeks of observation. The use of FSG-PUA materials effectively enhances the mechanical properties of GIC materials, demonstrating excellent biocompatibility and significant potential as dental restorative materials. Among them, the 20% FSG-PUA modified GICs exhibited significantly superior flexural strength, surface hardness, shear strength, water absorption, and solubility compared with F9 and slightly surpassing RMGIC, showcasing the best mechanical performance.

Photocurable and elastic polyurethane based on polyether glycol with adjustable hardness for 3D printing customized flatfoot orthosis.

Orthopedic insoles is the most commonly used nonsurgical treatment method for the flatfoot. Polyurethane (PU) plays a crucial role in the manufacturing of orthopedic insoles due to its high wear resistance and elastic recovery. However, preparing orthopedic insoles with adjustable hardness, high-accuracy, and matches the plantar morphology is challenging. Herein, a liquid crystal display (LCD) three-dimensional (3D) printer was used to prepare the customized arch-support insoles based on photo-curable and elastic polyurethane acrylate (PUA) composite resins. Two kinds of photo-curable polyurethanes (DL1000-PUA and DL2000-PUA) were successfully synthesized, and a series of fast-photocuring polyurethane acrylate (PUA) composite resins for photo-polymerization 3D printing were developed. The effects of different acrylate monomers on the Shore hardness, viscosity, and mechanical properties of the PUA composite resins were evaluated. The PUA-3-1 composite resin exhibited low viscosity, optimal hardness, and mechanical properties. A deviation analysis was conducted to assess the accuracy of printed insole. Furthermore, the stress conditions of the PUA composite resin and ethylene vinyl acetate (EVA) under the weight load of healthy adults were compared by finite element analysis (FEA) simulation. The results demonstrated that the stress of the PUA composite resin and EVA were 0.152 MPa and 0.285 MPa, and displacement were 0.051 mm and 3.449 mm, respectively. These results indicate that 3D-printed arch-support insole based on photocurable PUA composite resin are high-accuracy, and can reduce plantar pressure and prevent insoles premature deformation, which show great potential in the physiotherapeutic intervention for foot disorders.

3D bio-printing of photocrosslinked anatomically tooth-shaped scaffolds for alveolar ridge preservation after tooth extraction.

Alveolar ridge preservation techniques have been developed as a possible method to maintain the optimum ridge contour and dimensions. Grafting a bone substitute is paramount to prevent alveolar ridge resorption after tooth extraction. However, it remains a great challenge to develop alveolar ridge preservation materials with sufficient mechanical strength, bioactivity, and osteoinductivity and favorable tooth extraction socket morphological matching. In this work, a novel photocrosslinked composite ink consisting of nacre, polyurethane (PU) and polyhedral oligomeric silsesquioxane (POSS) was prepared and used to fabricate 3D porous scaffolds for alveolar ridge preservation. This nacre/PU/POSS (NPP) composite was characterized in terms of its rheological behavior, mechanical properties, and surface hydrophilicity. The biomineralization of these NPP scaffolds was confirmed via in vitro experiments. MC3T3-E1 cells were distributed homogeneously on the NPP scaffolds and stimulated cellular proliferation. When the NPP scaffolds were grafted into the sockets after extraction of mandibular incisors, the height and width of alveolar bone resorption were reduced, and new bone formation was observed. These NPP composites are promising scaffold materials for alveolar ridge preservation and 3D printing of bone grafts in future.

A novel resin cement to improve bonding interface durability.

Bonding failure is one of the main causes of failure of dental restorations. The bonding strength, aging resistance, and polymerization shrinkage of cement can affect the stability of the bonding interface and lead to marginal microleakage. To reduce the bonding failure rate of restorations, a novel polyurethane (PU) cement was designed to improve the mechanical properties, hydrophobicity, degree of conversion (DC), polymerization shrinkage, bond strength and aging resistance of cement by introducing isophorone diisocyanate (IPDI) and hydroxyethyl methacrylate (HEMA) and adjusting the polyester : polyether ratio to increase the degree of cross-linking. Experimental results verified that the novel PU could increase the mechanical properties and thermal stability of the cement, reduce polymerization shrinkage during the curing reaction, improve the bonding performance and DC, endow the cement with hydrophobic properties, and improve its ability to resist aging in the salivary environment to maintain the long-term stability of interfacial bonding under the influence of comprehensive factors. The results of this study provide a new direction and insights to reduce microleakage and improve the success rate of restorations.

Photopolymerizable and moisture-curable polyurethanes for dental adhesive applications to increase restoration durability.

In this study we evaluated dual-cure polyurethanes (PUs) as dental adhesives and investigated their effect on the durability of the resin-dentin bonding interface. Different novel photopolymerizable and moisture-curable PUs based on polyester polyol, polyether polyol, and hydroxyethyl methacrylates (HEMAs) were prepared, and their structural characteristics were evaluated by Fourier transform infrared spectroscopy. The tensile strength, elongation at break, and water sorption/solubility of the PU adhesives and the application for bonding with dentin were evaluated. The water sorption and solubility of the PU adhesives were significantly lower than those of two commercial control groups. The bond strength of the PU adhesives after 30 days of storage increased compared with their immediate bond strength, and the microleakage detection of Class V restorations showed less occurrence of marginal leakage compared with the commercial control groups. Cytotoxicity testing has shown that the PU adhesives have low toxicity to pulp cells. The results of this study may shift the future research focus of composite resin dental restoratives from original rigid bonding of the interface to a flexible bonding based on the use of PU adhesives. This may become a new strategy for decreasing the occurrence of microleakage and improving the durability of the bonding interface.

Fabrication of superhydrophobic coating for preventing microleakage in a dental composite restoration.

Superhydrophobic coatings were successfully fabricated by photo-crosslinked polyurethane (PU) and organic fluoro group-functionalized SiO2 nanoparticles (F-SiO2 NPs), and were introduced for preventing microleakage in a dental composite restoration. The F-SiO2 NPs possessed low surface energy and the PU can not only improve the mechanical stability but also promote F-SiO2 NPs to form multiscale structure, which could facilitate the properties of the as-prepared superhydrophobic coating by synergetic effect. The morphology and properties of the resulted superhydrophobic coatings with different PU/F-SiO2 ratios were studied using 1H NMR spectrum, fourier transform infrared spectra, scanning electron microscopy, atomic force microscopy and UV-vis spectrophotometry. The results showed that the superhydrophobic coatings with low PU/F-SiO2 ratio (1:3) possessed excellent hierarchical papillae structure with trapped air pockets, high contact angle (160.1°), low sliding angle (<1°) and good transparency. Additionally, MTT experiments results certified the prominent cell viability and biocompatibility for clinical application. Based on its fantastically superhydrophobic property, the as-prepared superhydrophobic coatings effectively prevented water permeation in resin composite restoration evaluation. This research may provide an effective method to solve the problem of microleakage and will efficiently increase the success rate of dental composite restorations.

[The effect of denture base resins coated with antibacterial coating on water sorption, solubility and monomer elution].

PURPOSE: To determine the influence of denture base resins coated with antibacterial coating on water sorption, solubility and monomer elution. METHODS: The values of water sorption and solubility were measured according to YY 0270-2003 and gas chromatography was used to examine the leachability of 4 commercially available heat-cured acrylic resins between experimental group and control group. Degree of crosslinking of the experimental heat-cured acrylic denture bases we remeasured by soxhlet extraction method. The data was analyzed by 17.0 software package. RESULTS: The values of water sorption, solubility and monomer elution of experimental group were lower compared to the control group. Degree of crosslinking of Heraeus reins was the highest among the experimental heat-cured acrylic denture bases. CONCLUSIONS: There is a same trend among water sorption, degree of crosslinking and the monomer elution. When the degree of crosslinking increases, the values of water sorption and monomer elution decrease. Antibacterial coating can improve the comprehensive properties of the denture base resins.