Assessment of Inhibition of Biofilm Formation on Non-Thermal Plasma-Treated TiO2 Nanotubes.

Peri-implantitis is an inflammatory disease similar to periodontitis, caused by biofilms formed on the surface of dental implants. This inflammation can spread to bone tissues and result in bone loss. Therefore, it is essential to inhibit the formation of biofilms on the surface of dental implants. Thus, this study examined the inhibition of biofilm formation by treating TiO2 nanotubes with heat and plasma. Commercially pure titanium specimens were anodized to form TiO2 nanotubes. Heat treatment was performed at 400 and 600 °C, and atmospheric pressure plasma was applied using a plasma generator (PGS-200, Expantech, Suwon, Republic of Korea). Contact angles, surface roughness, surface structure, crystal structure, and chemical compositions were measured to analyze the surface properties of the specimens. The inhibition of biofilm formation was assessed using two methods. The results of this study showed that the heat treatment of TiO2 nanotubes at 400 °C inhibited the adhesion of Streptococcus mutans (S. mutans), associated with initial biofilm formation, and that heat treatment of TiO2 nanotubes at 600 °C inhibited the adhesion of Porphyromonas gingivalis (P. gingivalis), which causes peri-implantitis. Applying plasma to the TiO2 nanotubes heat-treated at 600 °C inhibited the adhesion of S. mutans and P. gingivalis.

Evaluation of Physical Properties of Zirconia Suspension with Added Silane Coupling Agent for Additive Manufacturing Processes.

In this study, we have analysed the effects of a silane coupling agent on the volume fraction of zirconia for digital light processing (DLP)-based additive manufacturing processes. Zirconia suspension was prepared by the incorporation of silane-modified zirconia particles (experimental group) or untreated zirconia particles (control group). Furthermore, the control and experimental group were subdivided into three groups based on the volume fraction (52, 54, and 56 vol%) of zirconia particles. The disk-shaped zirconia samples were 3D (three-dimensional) printed using the DLP technique and their physical and mechanical properties were evaluated. The addition of a silane coupling agent to the zirconia samples was found to have influence of about 6% on the hardness and biaxial flexural strength. Moreover, the decrease in minute air gaps inside the zirconia layers significantly increased the material density (visualized from the microstructure analysis). Thus, from this study, it was established that the silane-modified zirconia particles had a positive effect on the physical properties of the zirconia parts.

Fabrication and Characterization of 45S5 Bioactive Glass/Thermoplastic Composite Scaffold by Ceramic Injection Printer.

45S5 bioactive glass (45S5) scaffolds were fabricated using a novel additive-manufacturing (AM) technology. A ceramic injection printer (CIP) was designed by combining injection molding and fused deposition modeling, for the fabrication of three-dimensional constructs of ceramic materials. A high fraction (50 vol%) of 45S5 powder was mixed with the thermoplastic polymer. The synthesized 45S5 composites were subjected to Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD) analysis, and field-emission scanning electron microscopy (FE-SEM). The BET results of prepared 45S5 powder were confirmed to have a mean pore diameter of 11.402 nm, and specific surface area is 0.966 m²/g. The prepared 45S5/thermoplastic composite powder was subjected to Thermogravimetric/Differential thermal analysis (TG/DTA). The debinding process of polymer occurred at 192.5, 360.8, and 393 °C. The elastic modulus and ultimate stress of these scaffolds were measured to be 312.49±87.36 MPa and 21.83±6.67 MPa, respectively. The XRD results revealed the presence of Na6Ca3Si6O18 phases. The presence of Si, Ca, P, and Na was confirmed via energy-dispersive X-ray spectroscopy (EDS). The printed scaffold exhibited amorphous calcium phosphate (ACP) expression after immersion in simulated body fluid (SBF) and also it was observed that the intensity of the crystalline phase of 45S5 was decreased, as the immersion time increases. Bioactive glass composites with the high volume fraction can be able to construct 3D complex porous scaffolds using CIP.

Wear Behavior of the Human Enamel Antagonist to Different Glazed Zirconia.

In this study, the wear behavior of glazed zirconia was investigated to the antagonist with human enamel after simulated mastication. Twenty Y-TZP specimens were divided into 4 groups: untreated zirconia (Z), glazed zirconia with IPS e.max Ceram (GZE), glazed zirconia with VITA AKZENT® Plus (GZV), and glazed zirconia with glass (GZG). Glazing glass was mainly composed of SiO2, B2O3, Al2O3, Na2O and K2O (nearly 91 wt%). The surface roughness of the specimens was evaluated using roughness profiler. The maxillary premolar teeth were selected as the antagonist. The wear of human enamel against human enamel was used as a control. Five-disc specimens per group were subjected to chewing stimulation CS-4 (SD Mechatronic GmbH, Germany) for 240,000 cycles against human enamel. The wear loss of antagonistic teeth was calculated using a three-dimensional profiling system and the volume loss of the tooth was scanned using a 3D scanner. 3D data obtained before and after testing were overlapped using 3D software (Dentacian Software, EZplant, Korea). The wear loss of glazed zirconia GZE, GZV and GZG groups showed significantly lower than that of human enamel. Whereas, the zirconia (Z) group exhibits significantly lower volume loss than glazed zirconia and enamel. These results show that the wear of the glazing glass is comparable to other commercial glazing materials. Glazing materials are both more susceptible to wear the antagonist relative to zirconia.

Effect on Cell Viability with the Passage of Time After Atmospheric Plasma Treatment on Titanium Dioxide Surface.

Various attempts to modify the surface of dental implants have been made in order to improve the adhesion of osteocytes. Plasma treatment on dental implants has been suggested to improve osseointegration. This study examined the effect on cell viability with the passage of time after atmospheric plasma treatment. An atmospheric plasma generator (PGS-200 Plasma generator, Expantech Co., Korea) was used and the gas was mixed with the Ar2(99%)/O2(1%) composition and applied to the specimens. The passage of time was set to 7 immediately after treatment, after 30 minutes of treatment, after 60 minutes of treatment, after 90 minutes of treatment, after 24 hours of treatment, and after 48 hours of treatment. Surface property change with the passage of time after plasma treatment were confirmed by FE-SEM, surface roughness and X-ray photoelectron spectroscopy. Cell viability was evaluated by the WST-8 assay. The data were analyzed statistically using a 1-way ANOVA and Tukey's multiple comparisons test (α = .05). It was confirmed that the chemical composition of the surface changes as the passage of time increases after plasma treatment. The viability of L-929 cells was the highest immediately after plasma treatment, and cell viability decreased with increasing the passage of time. As a result of this study, it was confirmed that passage of time is a very important factor for the plasma treated surface.

Assessment of Inhibition of Biofilm Formation on TiO2 Nanotubes According to Non-Thermal Plasma Treatment Conditions and the Elapsed Time in the Atmosphere.

Periimplantitis is an inflammation similar to periodontitis, and is caused by biofilms formed on the surface of dental implants. Application of plasma on biomaterials has been reported to decrease the initial adhesion of microorganism by causing chemical changes without changing the surface morphology. The purpose of this study is to evaluate the effect of inhibition of biofilm formation on the elapsed time after plasma treatment. Non thermal plasma generator (PGS-200 Plasma generator, Expantech Co., Korea) was applied to the specimens. The elapsed time in the atmosphere was set to 5 immediately after treatment, after 30 minutes of treatment, after 60 minutes of treatment, after 90 minutes of treatment. Surface property change with the elapsed time in the atmosphere after plasma treatment were confirmed by X-ray photoelectron spectroscopy and contact angle. Inhibition of biofilm formation was evaluated by the fluorescent nucleic acid staining. It was confirmed that the chemical composition and bonding state of the surface changes as the elapsed time in the atmosphere increases after plasma treatment. The adhesion of Porphyromonas gingivalis was the lowest immediately after plasma treatment, and increased again with increasing elapsed time in the atmosphere after plasma treatment. As a result of this study, it was confirmed that elapsed time in the atmosphere is a very important factor for inhibition of biofilm formation.

Evaluation of Cure Depth and Geometrical Overgrowth Depending on Zirconia Volume Fraction Using Digital Light Processing.

The optical properties of zirconia photopolymer suspension for DLP (Digital Light Processing) were evaluated. The light source and intensity were set to 395 nm and 30 mW/cm². Experimental groups were divided into 48, 50, 52, 54, 56 and 58 vol% according to the zirconia volume fraction. The cure depth of all groups was at least 47.35 um when cured for 1 sec, which was higher than layer parameter values of the 3D printer. The geometrical overgrowth showed 28.55% at 48 vol% and 36.94% at 58 vol%. As the volume fraction of zirconia increased, the geometrical overgrowth increased and the cure depth reduced.

Shear Bond Strength of Zirconia to Titanium Implant Using Glass Bonding.

This study evaluated the shear bond strength of zirconia to titanium implant components using silica-based glasses and compared the strength with that of implant components bonded using a commercial resin cement. Forty cylindrical zirconia specimens and forty titanium disks (Grade IV) were divided equally into four groups, depending on the adhesive used: three different types of glasses (group G, group GI, group GIB) and a self-adhesive resin cement (group U200), which was used as a control. The shear bond strength was evaluated using a universal testing machine and failure mode was examined by optical microscope. Data was analyzed using One-way ANOVA with p-value <0.05, which was considered statistically significant. The shear bond strength of the three glass groups was significantly higher than that of group U200 (p<0.05). Failure mode in all groups was a combination of adhesive and cohesive modes. Shear bond strength of zirconia to titanium bonded using glasses was higher than that using self-adhesive resin cement.

Antibacterial Activity and Fibroblast Cell Viability of Zirconia Coated with Glass Ceramic Containing Ag and NaF Nanoparticles.

The aim of this study was to evaluate the antibacterial activity against Streptococcus mutans and fibroblast viability of zirconia coated with glass ceramic powder containing Ag and F nanoparticles. Specimens were divided into eight groups depending on the glass ceramic powders: 5, 10, 15, 20 wt% of NaF and Ag, respectively. Adhesion of Streptococcus mutans on glass-coated zirconia surface was evaluated by antimicrobial test. Fibroblast viability was examined by WST-8 assay. In result, the bacterial activity was reduced by 11.8%, 15.4% in Ag 10 wt% and 20 wt% groups. When 5~15 wt% of NaF was added, bacterial counts decreased to 4.2~65.4%, and when 20 wt% of NaF was added, the number of bacteria increased by 29.4%. Regardless of Ag and NaF content, all zirconia specimens showed cell viability above 70%. Within the limitations of this study, zirconia coated with glass ceramics powder containing Ag and NaF was found to reduce the adhesion of Streptococcus mutans but had no influence on osteoblast activation.

Novel ß-TCP Coated Titanium Nanofiber Surface for Enhanced Bone Growth.

In this study, we examined the effect of ß-tricalcium phosphate (ß-TCP) coating on alkali-treated CP Grade II titanium surface via RF magnetron sputtering on osteoblast like cell (MC3T3-E1) viability and bone formation in rat tibia. The specimens were divided into three groups; commercially pure titanium (control group), alkali-treated titanium with nanofiber structure (NF group) and ß-TCP coating on alkali-treated titanium with nanofiber structure (TNF group). The surface characteristics of specimens were observed under a field emission scanning electron microscope (FE-SEM), and contact angle was measured. The cell viability was assessed in vitro after 1 day, 3 days and 7 days. Implants of 2.0 mm diameter and 5.0 mm length were inserted into the tibia of rats. After 4 wks, the histomorphometric analysis was performed. Group NF and group TNF showed improved hydrophilicity of Ti. Group TNF showed significantly higher cell viability (P < 0.05) after 7 days. The bone to implant contact (BIC) ratio of the control group, NF group, and TNF group were 32.3%, 35.5%, and 63.9%, respectively. The study results suggested that ß-TCP coated alkali-treated titanium surface via RF magnetron sputtering might be effective in implant dentistry due to enhanced hydrophilicity, improved cell response, and better osseointegration.

Hydroxyapatite Coating on TiO2 Nanotube by Sol-Gel Method for Implant Applications.

The aim of this study was to determine the effect of hydroxyapatite (HA) coating on titanium dioxide (TiO2) nanotube by sol-gel process on viability of osteoblast like cell (MC3T3-E1) and bone formation in rat tibia. Specimens were divided into three groups including commercially pure titanium (control group), TiO2 nanotubes (group N), and HA coated TiO2 nanotubes (group HN). Surface characteristics were determined using field emission scanning electron microscope (FE-SEM; S-4700, Hitachi, Japan) and contact angles were measured. Cell viability was investigated in vitro after 1 day, 3 days, and 7 days of incubation. Implants (2.0 mm in diameter and 5.0 mm in length) were inserted into the tibia of rats. After 4 weeks, histomorphometric analysis was performed. Both N and HN groups showed enhanced hydrophilicity compared to control group. After 7 days of implantation, group HN showed higher cell viability with marginal significance (0.05 < P < 0.1). Bone to implant contact (BIC) ratio in the control group, group N, and group HN were 32.5%, 33.1%, and 43.8%, respectively. Results of this study showed that HA coated TiO2 nanotube using sol-gel process could be used to enhance hydrophilicity and improve osseointegration of dental implant surface.

Evaluation of the Fitness of Glass-Infiltrated Zirconia Core in Maxillary Central Incisor.

The purpose of this study was to evaluate the fitness of zirconia cores according to the amount and treated surface of glass infiltration. A maxillary right central incisor customized abutment was milled to have a 6° slope and a 1 mm deep chamfer margin and was manufactured in an intaglio mold using silicone impression material. Fifty-six stone dies were produced by injecting high strength dental stone into a mold and then zirconia cores were milled with CAD/CAM systems. The control group (Control) used non glass-infiltrated zirconia, and the experiment group was divided by one with the glass and distilled water ratio of 1:300 and the other with the ratio of 1:100. Each group was divided into subgroups by glasstreated surface: external surface infiltration, internal surface infiltration, and both surface infiltration. The zirconia cores sintered after glass infiltration were attached to the stone dies and then cut. Afterwards, the absolute marginal discrepancies and internal gaps of the buccal and lingual sides were measured. The buccal absolute marginal discrepancies and lingual internal gaps were influenced by the glass infiltration amount (p < 0.05); while fitness of zirconia core were not affected by the glasstreated surface (p > 0.05). As a result of the above experiments, the glass-infiltrated zirconia cores showed a clinically acceptable fitness, which is within 120 µm. This means that glass infiltration can be clinically used.

Evaluation of Acid Etching on Surface Characteristics, Strength and Biological Response of Glass-Infiltrated Zirconia.

This study evaluated the effect of acid etching on surface characteristics, flexural strength and osteoblast cell response of glass-infiltrated zirconia. Zirconia specimens were divided into six groups: untreated zirconia (Z); glass-infiltrated zirconia (ZG); glass-infiltrated and sandblasted zirconia (ZGS); glass-infiltrated, sandblasted and 5 min acid-etched zirconia (ZGS-E5); glassinfiltrated, sandblasted and 15 min acid-etched zirconia (ZGS-E15); glass-infiltrated, sandblasted and 25 min acid-etched zirconia (ZGS-E25). Surface roughness, biaxial flexural strength and MC3T3-E1 cell proliferation were evaluated. When increasing etching time, surface roughness significantly increased while flexural strength decreased. Cell proliferation rate at day 3 on group ZGS-E15 and ZGS-E25 was significantly higher than that of other groups. Surface roughness and flexural strength of glass-infiltrated zirconia can be controlled by adjusting etching time. Rough surface made by acid etching following glass infiltration significantly enhanced osteoblast cell response. Glass infiltration improved strength of zirconia but severe acid etching slightly reduced strength of zirconia.

Acid etching of glass-infiltrated zirconia and its biological response.

PURPOSE: The purpose of this study was to evaluate the influence of acid etching treatment on surface characteristics and biological response of glass-infiltrated zirconia. MATERIALS AND METHODS: A hundred zirconia specimens were divided into four groups depending on surface treatments: untreated zirconia (group Z); acid-etched zirconia (group ZE); glass-infiltrated zirconia (group ZG); and glass-infiltrated and acid-etched zirconia (group ZGE). Surface roughness, surface topography, surface morphology, and Vickers hardness of specimens were evaluated. For biological response test, MC3T3-E1 cell attachment and proliferation on surface of the specimens were examined. The data were statistically analyzed using one-way ANOVA and Tukey's HSD test at a significance level of 0.05. RESULTS: Group ZGE showed the highest surface roughness (Ra = 1.54 µm) compared with other groups (P < .05). Meanwhile, the hardness of group Z was significantly higher than those of other groups (P < .05). Cell attachment and cell proliferation were significantly higher in group ZGE (P < .05). CONCLUSION: We concluded that effective surface roughness on zirconia could be made by acid etching treatment after glass infiltration. This surface showed significantly enhanced osteoblast cell response.

Effect on Adhesion of Porphyromonas gingivalis by Titanium Nitride Sputter Coating or Plasma Nitriding of Titanium.

Porphyromonas gingivalis (P. gingivalis) is one of main bacteria that adheres to the surface of dental implants and causes peri-implantitis. The purpose of this study was to observe the surface characteristics of titanium processed with either titanium nitride (TiN) sputter coating or plasma nitriding and to evaluate the subsequent adhesion of P. gingivalis. Specimens were divided into three groups: commercially pure (CP) titanium (control group), TiN sputter­coated titanium (group S), and plasma-nitrided titanium (group P). Surface characteristics such as roughness, morphology, and the formation of a thin TiN film or a nitriding layer were assessed. Adhesion of P. gingivalis in the three groups was determined by means of the crystal violet staining assay, and results were compared with one-way ANOVA, with post hoc comparison using Tukey's test (α = 0.05). Surface roughness values for the control group, group S, and group P were 0.08±0.02 µm, 0.19±0.04 µm, and 0.13±0.02 µm, respectively. In group S, the TiN layer was 1.36±0.1 µm thick, and nitrogen was detected on the surface of the specimens in group P, confirming formation of a nitrided layer. The level of adhesion in group P was significantly higher than that in the control group and in group S (p < 0.05), but there was no significant difference between the control group and group S. Within the limitations of this study, TiN sputter coating did not affect adhesion of P. gingivalis on the titanium surface, whereas adhesion was increased on the plasma-nitrided titanium surface.

Surface Characteristics of Bioactive Glass-Infiltrated Zirconia with Different Hydrofluoric Acid Etching Conditions.

The purpose of this study was to examine the surface characteristics of bioactive glass-infiltrated zirconia specimens that underwent different hydrofluoric acid (HF) etching conditions. Specimens were classified into the following six groups: Zirconia, Zirliner, Porcelain, Bioactive glass A1, Bioactive glass A2, and Bioactive glass A3. Zirliner and porcelain were applied to fully sintered zirconia followed by heat treatment. Bioactive glass was infiltrated into presintered zirconia using a spin coating method followed by complete sintering. All the specimens were acid-etched with 10% or 20% HF, and surface roughness was measured using a profiler. The surface roughness of the zirconia group was not affected by the etching time or the concentration of the acid. The roughness of the three bioactive glass groups (A1, A2, and A3) was slightly increased up until 10 minutes of etching. After 1 hour of etching, the roughness was considerably increased. The infiltrated bioactive glass and acid etching did not affect the adhesion and proliferation of osteoblasts. This study confirmed that surface roughness was affected by the infiltration material, etching time, and acid concentration. For implant surfaces, it is expected that the use of etched bioactive glass-infiltrated zirconia with micro-topographies will be similar to that of machined or sand-blasted/acid-etched (SLA) titanium.

Evaluation of Sandblasting on Mechanical Properties and Cell Response of Bioactive Glass Infiltrated Zirconia.

This study investigated the mechanical properties and initial cell response of bioactive glass infiltrated zirconia before and after sandblasting. One hundred zirconia specimens were divided into the following four groups: untreated zirconia (ZR), sandblasted zirconia (ZS), glass infiltrated zirconia (ZG), and sandblasted glass infiltrated zirconia (ZGS). Surface roughness, biaxial flexural strength, hardness and osteoblast cells proliferation were evaluated. ZGS group showed a slight decrease in hardness. However it has improvement in flexural strength (686.2 MPa). After sandblasting, the ZGS group had the highest surface roughness (R a = 1.24 µm) with enhanced osteoblast cells response. Our results indicated that sandblasting method can improve the mechanical properties of bioactive glass infiltrated zirconia with better osteoblast cell response. This new surface is promising for zirconia dental implant application in the future.

The Effect of Glass Layer Thickness on the Shear Bond Strength Between Glass Infiltrated Zirconia and Veneering Porcelain.

This study was to investigate the various glass thicknesses on the shear bond strength between zirconia and veneering porcelain. The zirconia specimens were classified into 5 groups (n = 12). For the control group, the Y-TZP disk was sintered (G0). For the test group, the presintered zirconia disks were spin coated with different W/P ratio glass compositions. The glass thickness on the zirconia was 1 µm (G1), 4 µm (G4), 10 µm (G10), and 40 µm (G40), respectively. All specimens were build-up veneering porcelain and fired. The shear bond strength (SBS) was tested in a universal testing machine (crosshead speed = 0.5 mm/min). As the thickness of the glass decreased, the shear bond strength increased. The G1 group showed significantly higher than the control group (G0) (P < 0.05). The results suggest that the thickness of glass coating on the zirconia structure needs to be made thin for better bonding strength with veneering porcelain.

A New Fast and Simple Border Molding Process for Complete Dentures Using a Compound Stick Gun.

This article describes the use of a newly invented compound stick gun to take impressions for complete denture. The border molding process involves loading the modeling compound in an electric heating device and applying an even thickness of compound on the flange of a custom tray at a proper temperature without hot water tempering. This method provides a quicker and easier border molding process alternative to conventional techniques.

Evaluation of Osteoblast-Like Cell Viability and Differentiation on the Gly-Arg-Gly-Asp-Ser Peptide Immobilized Titanium Dioxide Nanotube via Chemical Grafting.

This study examined the effect of the immobilization of the Gly-Arg-Gly-Asp-Ser (GRGDS) peptide on titanium dioxide (TiO2) nanotube via chemical grafting on osteoblast-like cell (MG-63) viability and differentiation. The specimens were divided into two groups; TiO2 nanotubes and GRGDS-immobilized TiO2 nanotubes. The surface characteristics of GRGDS-immobilized TiO2 nanotubes were observed by using X-ray photoelectron spectroscopy (XPS) and a field emission scanning electron microscope (FE-SEM). The morphology of cells on specimens was observed by FE-SEM after 2 hr and 24 hr. The level of cell viability was investigated via a tetrazolium (XTT) assay after 2 and 4 days. Alkaline phosphatase (ALP) activity was evaluated to measure the cell differentiation after 4 and 7 days. The presence of nitrogen up-regulation or C==O carbons con- firmed that TiO2 nanotubes were immobilized with GRGDS peptides. Cell adhesion was enhanced on the GRGDS-immobilized TiO2 nanotubes compared to TiO2 nanotubes. Furthermore, significantly increased cell spreading and proliferation were observed with the cells grown on GRGDS-immobilized TiO2 nanotubes (P < .05). However, there was no significant difference in ALP activity between GRGDS-immobilized TiO2 nanotubes and TiO2 nanotubes. These results suggest that the GRGDS-immobilized TiO2 nanotubes might be effective in improving the osseointegration of dental implants.