Potential of Fluoride-Containing Zinc Oxide and Copper Oxide Nanocomposites on Dentin Bonding Ability.

Despite recent advances in bonding restorations, which are the basis of restorative dentistry, secondary caries are still able to form. Previously, a novel fluoride-containing zinc and copper (ZCF) nanocomposite was introduced to prevent the formation of caries due to its antibacterial activity. In this study, we studied the impact of ZCF nanoparticles on the adhesive strength of bonding restorations through micro-tensile bond strength (µTBS) testing. The impact of antibacterial and matrix metalloproteinase (MMP) inhibitors on the nanoparticles was also examined. The nanocomposites were prepared using a simple one-step homogeneous co-precipitation method at a low temperature. A self-etch adhesive was applied to 10 extracted caries-free human molars with (test group) and without (control group) the ZCF nanoparticles. This was followed by composite resin build-up and µTBS testing, MMP activity assays, and evaluation of the antibacterial effects. The results showed no significant differences in the µTBS between the ZCF and the control groups. However, the ZCF exhibited a significant inhibitory effect against MMP-2, MMP-8, and MMP-9, in addition to an antibacterial effect on Streptococcus mutans. Therefore, the present study demonstrated that the addition of ZCF nanoparticles to adhesive systems can result in MMP inhibition and antibacterial action while maintaining the mechanical properties of the bonding restorations.

Surface analysis of titanium disks with strontium coating.

Peri-implantitis is one of the most common complications after dental implant placement. Researchers have demonstrated that the peri-implantitis tends to occur around dental implants with a rough surface rather than those with a smooth surface. We aimed to investigate the ability of a smooth titanium (Ti) surface containing strontium (Sr) to enhance bone formation as a result of strontium's capacity to support osteoblast proliferation and differentiation. A thin titanium oxide film was formed on an as-mirror polished Ti surface by dipping in 5% sodium hypochlorite (NaOCl) solution for 24 h, followed by thermal treatment at 350°C. The Ti surface was then treated with 1% strontium nitrate (Sr(NO3)2) solution and turned in spin coater. The surface morphology, chemical composition, and release of strontium ions (Sr2+) were evaluated. The results demonstrate that strontium in the form of Sr2+ was successfully doped into the titanium dioxide (TiO2) film by this simple chemical treatment.

Protective Effects of GIC and S-PRG Filler Restoratives on Demineralization of Bovine Enamel in Lactic Acid Solution.

This study was aimed at investigating the protective effects of glass ionomer cement (GIC) and surface pre-reacted glass ionomer (S-PRG) fillers used as dental restorative materials on demineralization of bovine enamel. GlasIonomer FX ULTRA (FXU), Fuji IX GP Extra (FIXE), CAREDYNE RESTORE (CDR) were used as GICs. PRG Barrier Coat (BC) was used as the S-PRG filler. They were incubated in a lactic acid solution (pH = 4.0) for six days at a temperature of 37 °C. The mineral was etched from the enamel surface, and a large number of Ca and P ions were detected in solution. The Al, F, Na, Sr, and Sr ions were released in GICs and S-RPG fillers. The Zn ion was released only in CDR and the B ion was released only in BC. The presence of apparent enamel prism peripheries was observed after six days of treatment for the group containing only enamel blocks. pH values for the FXU, FIXE, CDR, BC, and enamel block groups after six days were 6.5, 6.6, 6.7, 5.9, and 5.1, respectively. Therefore, the observed pH neutralization effect suppressed progression of caries due to the release of several ions from the restoratives.

Inhibition of enamel demineralization by an ion-releasing tooth-coating material.

PURPOSE: To evaluate the inhibitory effect of a surface pre-reacted glass-ionomer (S-PRG) filler-containing tooth-coating material on enamel demineralization. The outer surface of the S-PRG filler is in a state in which ions are readily released. METHODS: Human enamel blocks were incubated in lactic acid solution (pH 4.0) with and without a disk (n=6) made of the cured tooth-coating material. Test solutions were changed every 24 hours and incubation was continued for 4 days. The pH and amount of fluoride released were measured with an electrode and ion meter, respectively. The concentrations of ions (aluminum, boron, calcium, phosphorus, silicon, sodium, and strontium) were measured by inductively coupled plasma atomic emission spectroscopy. The surface of the enamel block was observed with a scanning electron microscope. RESULTS: Enamel demineralization was not observed in an enamel block incubated with a disk of the tooth-coating material. Ions released from S-PRG filler had an acid buffering action in the low pH lactic acid solution. However, in the enamel block-only solution showing high levels of calcium ion release, the degree of demineralization was correlated with morphological changes of the enamel surface. CLINICAL SIGNIFICANCE: Due to the buffering effects of the pre-reacted glass-ionomer surface by ion release, the S-PRG filler-containing tooth-coating material inhibited enamel demineralization by neutralizing the acidic environment at an early time point.

Designing an antibacterial acrylic resin using the cosolvent method -Effect of ethanol on the optical and mechanical properties of a cold-cure acrylic resin.

Antimicrobial cetylpyridinium chloride (CPC) has low miscibility with acrylic resin monomer but can be homogeneously mixed using ethanol as a cosolvent. This study investigated the effects of ethanol addition on the properties of a cold-cure acrylic resin. Ethanol was an excellent cosolvent for CPC and methyl methacrylate monomer (MMA), but the cured resin exhibited a strong change in coloration to yellow (ΔE*ab>8) and a drastically reduced bending strength (from 97 to 25 MPa) and elastic modulus (from 2.7 to 0.6 GPa) when equal volumes of ethanol and monomer were used together, possibly due to the solvation and deactivation of radicals by ethanol. However, these unfavorable effects diminished when the ethanol/MMA ratio was reduced to 0.25, and became smaller when each specimen was depressurized and excess ethanol was removed. Thus, it may be possible to develop a molecularly uniform antibacterial acrylic resin with acceptable color and strength using this simple technique.

Biological activation of zirconia surfaces by chemical modification with IGF-1.

The purpose of this study was to improve the adhesion and extension of human gingival epithelial cells (HGECs) to the yttria-stabilized zirconia polycrystal (Y-TZP) surfaces by immobilization of insulin-like growth factor 1 (IGF-1). Surface analyses by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that IGF-1 was successfully immobilized on the Y-TZP surfaces. There was no significant difference between the number of cells attached to the IGF-1-immobilized Y-TZP surfaces and on the as-polished Y-TZP surfaces either at 3 or 72 h. However, IGF-1-immobilized Y-TZP surfaces yielded a significantly higher expression of integrin ß4 mRNA and laminin-5 mRNA, and enhanced adhesion strength of HGECs after 72 h of incubation. There was no difference between the amount of adhered Streptococcus gordonii (S. gordonii) found on the IGF-1-immobilized Y-TZP surfaces and on the as-polished Y-TZP surfaces. These results suggested that the IGF-1-immobilized Y-TZP surfaces developed using the method reported herein enhanced the adhesion and extension of HGECs to the Y-TZP surfaces without enhancing S. gordonii adhesion.

Inhibition of initial bacterial adhesion on titanium surfaces by lactoferrin coating.

Because dental implant abutments are located at transmucosal sites, their surface should inhibit bacterial accumulation to prevent peri-implantitis. The authors examined the effects of human lactoferrin (LF), an antibacterial protein present in saliva, as an antibacterial coating on the titanium surface and evaluated its effects before and after mucin-containing artificial saliva (AS) incubation. In the control group, titanium disks were soaked in distilled water, whereas in the LF group, titanium disks were soaked in LF solution to coat the disks. In the control-AS and LF-AS groups, half of the control and LF disks were incubated with AS. To confirm LF adsorption, the fluorescence intensity of fluorescein isothiocyanate-labeled LF was measured. The LF and LF-AS groups showed significantly higher intensity than the control and control-AS groups (P < 0.01). There was no significant difference between the LF and LF-AS groups (P > 0.05). The amount of adhered Streptococcus gordonii significantly increased by incubation with AS (P < 0.01) and significantly decreased by adsorption of LF (P < 0.01). There was no interaction between the two factors, LF adsorption and AS incubation (P = 0.561). These results suggest that the adsorbed LF inhibited bacterial adhesion following AS incubation. According to qualitative LIVE/DEAD analysis, viable bacteria appeared to be decreased in the presence of LF and SEM observation indicated that altered morphologies increased in LF and LF-AS groups. These results suggest that the adsorbed LF remained on the titanium surface after incubation with AS, and the remaining LF inhibited bacterial adhesion and exhibited bactericidal effects. Therefore, the adsorption of LF on the abutment material appears to be effective in preventing peri-implantitis.

Analysis of residual stress in the resin of metal-resin adhesion structures by scanning acoustic microscopy.

The residual stress caused by polymerization shrinkage and thermal contraction of a heat-curing resin containing 4-META on a metal-resin structure was measured by a scanning acoustic microscope. The tensile residual stress in the resin occurred within 70 µm of the adhesion interface with a flat plate specimen. The maximum tensile stress was about 58 MPa at the interface. On a metal plate specimen with retention holes, ring-like cracks in the resin occurred around the retention holes with the adhesive specimen and many linear cracks occurred in the resin vertical to the longitudinal direction of the metal frame with the non-adhesive specimens. There was tensile residual stress on the resin surface at the center of the retention holes of the adhesion specimen, indicating that the stress in the specimen with surface treatment for adhesion was higher than in that without surface treatment.