In this study, we aimed to evaluate the effect of the addition of powdery cellulose nanofibers (CNFs) on the mechanical properties of glass ionomer cement (GIC) without negatively affecting its chemical properties. Commercial GIC was reinforced with powdery CNFs (2–8 wt.%) and characterized in terms of flexural strength, compressive strength, diametral tensile strength, and fluoride-ion release properties. Powdery CNFs and samples subjected to flexural strength testing were observed via scanning electron microscopy. CNF incorporation was found to significantly improve the flexural, compressive, and diametral tensile strengths of GIC, and the corresponding composite was shown to contain fibrillar aggregates of nanofibers interspersed in the GIC matrix. No significant differences in fluoride-ion release properties were observed between the control GIC and the CNF-GIC composite. Thus, powdery CNFs were concluded to be a promising GIC reinforcement agent.

Glass-ionomer-cement (GIC) is helpful in Minimal Intervention Dentistry because it releases fluoride ions and is highly biocompatible. The aim of this study is to investigate the mechanisms by which hydroxyapatite (HAp) improves the mechanical strength and bioactive functioning of GIC when these materials are combined to make apatite ionomer cement (AIC). A conventional GIC powder was mixed with porous, spherical-HAp particles (HApS), crystalline HAp (HAp200) or one of two types of cellulose. The micro-compressive strengths of the additive particles were measured, and various specimens were evaluated with regard to their compressive strengths (CS), fluoride release concentrations (fluoride electrode) and multi-element release concentrations. The AIC was found to release higher concentrations of fluoride (1.2 times) and strontium ions (1.5 times) compared to the control GIC. It was detected the more release of calcium originated from HApS than HAp200 in AIC. The CS of the AIC incorporating an optimum level of HAp was also significantly higher than that of the GIC. These results suggest that adding HAp can increase the release concentration of ions required for remineralization while maintaining the CS of the GIC. This effect does not result from a physical phenomenon, but rather from chemical reactions between the HAp and polyacrylic acid of GIC.

Human mesenchymal stem cells can differentiate into various cell types and are useful for applications in regenerative medicine. Previous studies indicated that dental pulp exfoliated from deciduous teeth is a valuable alternative for dental tissue engineering because it contains stem cells with a relatively high proliferation rate. For clinical application, it is necessary to rapidly obtain a sufficient number of cells in vitro and maintain their undifferentiated state; however, the abundance of stem cells in the dental pulp tissue is limited. Non-thermal atmospheric pressure plasma (NTAPP) has been applied in regenerative medicine because it activates cell proliferation. Here, we examined the effects of NTAPP to activate the proliferation of human deciduous dental pulp fibroblast-like cells (hDDPFs) in vitro. Compared with untreated cells, NTAPP increased cell proliferation by 1.3-fold, significantly upregulated well-known pluripotent genes for stemness (e.g., Oct4, Sox2, and Nanog), and activated the expression of stem cell-specific surface markers (e.g., CD105). Overall, NTAPP activated the proliferation of various mesodermal-derived human adult stem cells while maintaining their pluripotency and stemness. In conclusion, NTAPP is a potential tool to expand the population of various adult stem cells in vitro for medical applications.

The purpose of this study was to examine the anti-oral microorganism effects of fluorine and/or silver ions implanted into acrylic resin (PMMA) using plasma-based ion implantation (PBII) with argon gas. The experimental PMMA specimens were implanted with F and Ag ions alone or simultaneously by the PBII method using Ar or Ar/F₂ gases and Ag mesh. The surface characteristics were evaluated by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM). Moreover, the antibacterial activity against Streptococcus mutans (S. mutans) and the antifungal activity against Candida albicans (C. albicans) were examined by the adenosine-5’-triphosphate (ATP) emission luminescence method. XPS spectra of the modified specimens revealed peaks due to F in the Ar/F and the Ar/F+Ag groups, and due to Ag in the Ar+Ag and the Ar/F+Ag groups. The water contact angle increased significantly due to the implantation of Ar, F, and Ag. In the AFM observations, the surface roughness of the Ar/F and the Ar/F+Ag groups increased significantly by less than 5 nanometers. The presence of F and Ag was found to inhibit S. mutans growth in the Ar+Ag and the Ar/F+Ag groups. However, this method provided no significant antifungal activity against C. albicans.

Human mesenchymal stem cells are capable of differentiating into various cell types and are useful for applications in regenerative medicine. Previous studies have indicated that stem cells can be isolated from dental pulp, and dental pulp exfoliated from deciduous teeth has become a useful alternative for dental tissue engineering because of its higher proliferation rate. For clinical application, it is necessary to culture cells in vitro and to obtain sufficient numbers of cells as quickly as possible. Furthermore, it is necessary to confirm the change in cells cultured in vitro in order to ensure that they have suitable characteristics. In this study, to investigate the changes in human deciduous dental pulp cells cultured with serum-free media, we analyzed cell proliferation, cell morphology and gene expression changes by microarray analysis. We found a high cell proliferation rate in cells that were cultured in STK2 that is a serum-free medium, and cells tended to remain in close contact with one another in cell morphology. In addition, 3248 genes were expressed at >2-fold higher levels in dental pulp cells from deciduous teeth cultured with STK2 compared with medium containing fetal bovine serum for 3 days.