Antibacterial and Antifungal Activities of PMMAs Implanted Fluorine and/or Silver Ions by Plasma-Based Ion Implantation with Argon.

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.

Surface modification of stainless steel by plasma-based fluorine and silver dual ion implantation and deposition.

The aims of this study were to modify dental device surface with fluorine and silver and to examine the effectiveness of this new surface modification method. Stainless steel plates were modified by plasma-based fluorine and silver ion implantation-deposition method. The surface characteristics and brushing abrasion resistance were evaluated by XPS, contact angle and brushing abrasion test. XPS spectra of modified specimens showed the peaks of fluoride and silver. These peaks were detected even after brushing abrasion test. Water contact angle significantly increased due to implantation-deposition of both fluorine and silver ions. Moreover, the contact angle of the modified specimen was significantly higher than that of fluorine only deposited specimen with the same number of brushing strokes. This study indicates that this new surface modification method of fluorine and silver ion implantation-deposition improved the brushing abrasion resistance and hydrophobic property making it a potential antimicrobial device.

Mechanical and Functional Properties of a Novel Apatite-Ionomer Cement for Prevention and Remineralization of Dental Caries.

Especially in pediatric dentistry, prevention by the control of initial lesions prior to cavitation is very important, and application of a pit and fissure sealant is essential to achieve this. Numerous reports have suggested that resin-based sealants are inferior to sealants based on glass-ionomer cement (GIC), because of GIC's many advantages, such as fluoride ion release properties and its good adhesion to tooth structures. However, the use of GIC is impeded due to its low flexural strength and fracture toughness. In this paper, we developed and characterized an apatite-ionomer cement (AIC) that incorporates hydroxyapatite (HAp) into the GIC; this development was aimed at not only reinforcing the flexural and compressive strength but also improving some functional properties for the creation of the material suitable for sealant. We examined the influence of differences in the compounding conditions of GIC powder, liquid, and HAp on flexural and compressive strengths, fracture toughness, fluoride ion release property, shear bond strength to bovine enamel, surface pH of setting cements, and acid buffer capability. These methods were aimed at elucidating the reaction mechanism of porous spherical-shaped HAp (HApS) in AIC. The following observations were deduced. (1) HAp can improve the mechanical strengths of AIC by strengthening the cement matrix. (2) The functional properties of AIC, such as acid buffer capability, improved by increasing the releasing amounts of various ions including fluoride ions. The novel AIC developed in this study is a clinically effective dental material for prevention and remineralization of tooth and initial carious lesion.

Effects of Powdery Cellulose Nanofiber Addition on the Properties of Glass Ionomer Cement.

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.

Influence of Porous Spherical-Shaped Hydroxyapatite on Mechanical Strength and Bioactive Function of Conventional Glass Ionomer Cement.

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.

Plasma-based fluorine ion implantation into dental materials for inhibition of bacterial adhesion.

The aims of this study were to evaluate the fluorine depth profiles of pure titanium (Ti), stainless steel (SUS), and polymethyl methacrylate (PMMA) modified by plasma-based fluorine ion implantation and the effects of fluorine ion implantation on contact angle, fluoride ion release, and S. mutans adhesion. Fluorine-based gases used were Ar+F2 and CF4. By means of SIMS, it was found that the peak count of PMMA was the lowest while that of Ti was the highest. Then, up to one minute after Ar sputtering, the presence of fluorine and chromic fluoride could be detected by XPS in the surface and subsurface layer. As for the effects of using CF4 gas for fluorine ion implantation into SUS substrate, the results were: contact angle was significantly increased; no fluoride ion release was detected; antibacterial activity was significantly increased while initial adhesion was decreased. These findings thus indicated that plasma-based fluorine ion implantation into SUS with CF4 gas provided surface antibacterial activity which was useful in inhibiting bacterial adhesion.

Effects of porous-hydroxyapatite incorporated into glass-ionomer sealants.

The purpose of the present study was to evaluate the mechanical and chemical properties of a novel glass ionomer cement for use as a pit and fissure sealant containing a porous hydroxyapatite, namely, apatite ionomer cement (AIC). Control sealant samples were used Fuji III (GIC-S). The experiment sealant samples (AIC-S) consisted of porous spherical hydroxyapatite (HApS) particles added at 28 wt% to GIC-S powder. The GIC-S and AIC-S samples were evaluated through mechanical strength measurements, scanning electron microscopy observations, energy dispersive X-ray spectroscopy analysis, fluoride ion release tests, and antibacterial tests. The flexural strength of the AIC-S was significantly higher than that of GIC-S for each period, 1 h, 24 h and 1 year. The fluoride release dose for AIC-S was consistently higher than that for GIC-S. In addition, the antibacterial properties of AIC-S were superior to those of GIC-S. The novel AIC-S may be a more suitable sealant material for pits and fissures with intact and/or infected enamel.

Antibacterial effect of acrylic dental devices after surface modification by fluorine and silver dual-ion implantation.

The purpose of the present study was to examine the effectiveness of fluorine and silver ions implanted and deposited into acrylic resin (poly(methyl methacrylate)) using a hybrid process of plasma-based ion implantation and deposition. The surface characteristics were evaluated by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy. In addition, an antibacterial activity test was performed by the adenosine-5'-triphosphate luminescence method. XPS spectra of modified specimens revealed peaks due to fluoride and silver. The water contact angle increased significantly due to implantation and deposition of both fluorine and silver ions. In addition, the presence of fluorine and silver was found to inhibit bacterial growth. These results suggest that fluorine and silver dual-ion implantation and deposition can provide antibacterial properties to acrylic medical and dental devices.

Hydroxyapatite particle characteristics influence the enhancement of the mechanical and chemical properties of conventional restorative glass ionomer cement.

The aims of this study were to improve the mechanical and chemical properties of conventional restorative glass ionomer cement (GIC) by adding hydroxyapatite (HAp) preparations with different characteristics, and to investigate the underlying reaction mechanisms. Fuji IX GP® was used as the control GIC. The experimental GICs consisted of four HAp-particles with different characteristics added at 8 mass% to Fuji IX-powder. All cements were prepared by mixing with Fuji IX-liquid (P/L=3.6). Four HAp-particles were analyzed, and then the mechanical strengths and the fluoride-ion- release-recharge-behaviors of five GIC groups were evaluated. The results of this study demonstrate that the addition of HAp particles with highly reactive properties such as high specific surface area can enhance the flexural strength and fluoride ion release properties of conventional restorative GIC. Our results further indicate that HAp functions as an adsorbent and an ion exchangeable agent, resulting in improved mechanical and chemical properties of GIC.