Atomic Layer Deposition of Zirconia on Titanium Implants Improves Osseointegration in Rabbit Bones.

Purpose: Atomic layer deposition (ALD) is a method that can deposit zirconia uniformly on an atomic basis. The effect of deposited zirconia on titanium implants using ALD was evaluated in vivo. Methods: Machined titanium implants (MTIs) were used as the Control. MTIs treated by sandblasting with large grit and acid etching (SA) and MTIs deposited with zirconia using ALD are referred to as Groups S and Z, respectively. Twelve implants were prepared for each group. Six rabbits were used as experimental animals. To evaluate the osteogenesis and osteocyte aspects around the implants, radiological and histological analyses were performed. The bone-to-implant contact (BIC) ratio was measured and statistically analyzed to evaluate the osseointegration capabilities. Results: In the micro-CT analysis, more radiopaque bone tissues were observed around the implants in Groups S and Z. Histological observation found that Groups S and Z had more and denser mature bone tissues around the implants in the cortical bone area. Many new and mature bone tissues were also observed in the medullary cavity area. For the BIC ratio, Groups S and Z were significantly higher than the Control in the cortical bone area (P < 0.017), but there was no significant difference between Groups S and Z. Conclusion: MTIs deposited with zirconia using ALD (Group Z) radiologically and histologically showed more mature bone formation and activated osteocytes compared with MTIs (Control). Group Z also had a significantly higher BIC ratio than the Control. Within the limitations of this study, depositing zirconia on the surface of MTIs using ALD can improve osseointegration in vivo.

Effects of TiO2 Nanotubes and Reduced Graphene Oxide on Streptococcus mutans and Preosteoblastic Cells at an Early Stage.

The effects of TiO2 nanotube (TNT) and reduced graphene oxide (rGO) deposition onto titanium, which is widely used in dental implants, on Streptococcus mutans (S. mutans) and preosteoblastic cells were evaluated. TNTs were formed through anodic oxidation on pure titanium, and rGO was deposited using an atmospheric plasma generator. The specimens used were divided into a control group of titanium specimens and three experimental groups: Group N (specimens with TNT formation), Group G (rGO-deposited specimens), and Group NG (specimens under rGO deposition after TNT formation). Adhesion of S. mutans to the surface was assessed after 24 h of culture using a crystal violet assay, while adhesion and proliferation of MC3T3-E1 cells, a mouse preosteoblastic cell line, were evaluated after 24 and 72 h through a water-soluble tetrazolium salt assay. TNT formation and rGO deposition on titanium decreased S. mutans adhesion (p < 0.05) and increased MC3T3-E1 cell adhesion and proliferation (p < 0.0083). In Group NG, S. mutans adhesion was the lowest (p < 0.05), while MC3T3-E1 cell proliferation was the highest (p < 0.0083). In this study, TNT formation and rGO deposition on a pure titanium surface inhibited the adhesion of S. mutans at an early stage and increased the initial adhesion and proliferation of preosteoblastic cells.

Antibacterial Evaluation of Zirconia Coated with Plasma-Based Graphene Oxide with Photothermal Properties.

The alternative antibacterial treatment photothermal therapy (PTT) significantly affects oral microbiota inactivation. In this work, graphene with photothermal properties was coated on a zirconia surface using atmospheric pressure plasma, and then the antibacterial properties against oral bacteria were evaluated. For the graphene oxide coating on the zirconia specimens, an atmospheric pressure plasma generator (PGS-300, Expantech, Suwon, Republic of Korea) was used, and an Ar/CH4 gas mixture was coated on a zirconia specimen at a power of 240 W and a rate of 10 L/min. In the physiological property test, the surface properties were evaluated by measuring the surface shape of the zirconia specimen coated with graphene oxide, as well as the chemical composition and contact angle of the surface. In the biological experiment, the degree of adhesion of Streptococcus mutans (S. mutans) and Porphyromonas gingivalis (P. gingivalis) was determined by crystal violet assay and live/dead staining. All statistical analyzes were performed using SPSS 21.0 (SPSS Inc., Chicago, IL, USA). The group in which the zirconia specimen coated with graphene oxide was irradiated with near-infrared rays demonstrated a significant reduction in the adhesion of S. mutans and P. gingivalis compared with the group not irradiated. The oral microbiota inactivation was reduced by the photothermal effect on the zirconia coated with graphene oxide, exhibiting photothermal properties.

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.

Effect of Non-Thermal Plasma Treatment of Contaminated Zirconia Surface on Porphyromonas gingivalis Adhesion and Osteoblast Viability.

Plasma treatment on a zirconia surface prevents bacterial contamination and maintains osteoblast activity. To assess the degree of adhesion of Porphyromonas gingivalis on a zirconia surface after non-thermal plasma (NTP) treatment, specimens were treated with plasma for 60, 300, and 600 s, after which P. gingivalis was inoculated onto the surface and incubated for 48 h. To assess osteoblast activity after NTP treatment, osteoblasts (MC3T3-E1) were dispensed onto the specimens contaminated with P. gingivalis immediately after NTP for 60 and 120 s, followed by incubation for 48, 72, and 96 h. P. gingivalis was cultured after 60 s of NTP treatment of zirconia. The NTP and control groups showed no significant difference (p = 0.91), but adhesion was significantly increased following NTP treatment for 300 s or longer (300, 600 s groups) (p < 0.05). After NTP treatment of P. gingivalis-contaminated zirconia, osteoblast activity significantly increased at 72 and 96 h (I60 and I120 s group) in the groups treated with plasma (p < 0.017). Application of NTP to dental zirconia implants for 60 s not only inhibits the proliferation of P. gingivalis, which causes peri-implantitis but also increases osseointegration on zirconia surfaces contaminated with P. gingivalis.

Biological Effects of the Novel Mulberry Surface Characterized by Micro/Nanopores and Plasma-Based Graphene Oxide Deposition on Titanium.

PURPOSE: This paper presents a technique for developing a novel surface for dental implants using a combination of nitriding and anodic oxidation, followed by the deposition of graphene oxide using atmospheric plasma. The effects of various surface treatments on bacterial adhesion and osteoblast activation were also evaluated. METHODS: CP titanium (control) was processed into disk-shaped specimens. Nitriding was conducted using vacuum nitriding, followed by anodic oxidation, which was performed in an electrolyte using a DC power supply, to form the novel "mulberry surface." Graphene oxide deposition was performed using atmospheric plasma with an inflow of carbon sources. After analyzing the sample surfaces, antibacterial activity was evaluated using Streptococcus mutans and Porphyromonas gingivalis bacteria. The viability, adhesion, proliferation, and differentiation of osteoblasts were also assessed. Analysis of variance (ANOVA) with Tukey's post-hoc test was used to calculate statistical differences. RESULTS: We observed that the mulberry surface was formed on samples treated with nitriding and anodic oxidation, and these samples exhibited more effective antibacterial activity than the control. We also found that the samples with additional graphene oxide deposition exhibited better biocompatibility, which was validated by osteoblast adhesion, proliferation, and differentiation. CONCLUSION: The development of the mulberry surface along with graphene oxide deposition inhibits bacterial adhesion to the implant and enhances the adhesion, proliferation, and differentiation of osteoblasts. These results indicate that the mulberry surface and graphene oxide deposition together can inhibit peri-implantitis and promote osseointegration.

Direct-Deposited Graphene Oxide on Dental Implants for Antimicrobial Activities and Osteogenesis.

OBJECTIVE: To determine the effects of graphene oxide (GO) deposition (on a zirconia surface) on bacterial adhesion and osteoblast activation. METHODS: An atmospheric pressure plasma generator (PGS-300) was used to coat Ar/CH4 mixed gas onto zirconia specimens (15-mm diameter × 2.5-mm thick disks) at a rate of 10 L/min and 240 V. Zirconia specimens were divided into two groups: uncoated (control; Zr) group and GO-coated (Zr-GO) group. Surface characteristics and element structures of each specimen were evaluated by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and contact angle. Additionally, crystal violet staining was performed to assess the adhesion of Streptococcus mutans. WST-8 and ALP (Alkaline phosphatase) assays were conducted to evaluate MC3T3-E1 osteoblast adhesion, proliferation, and differentiation. Statistical analysis was calculated by the Mann-Whitney U-test. RESULTS: FE-SEM and Raman spectroscopy demonstrated effective GO deposition on the zirconia surface in Zr-GO. The attachment and biofilm formation of S. mutans was significantly reduced in Zr-GO compared with that of Zr (P < 0.05). While no significant differences in cell attachment of MC3T3-1 were observed, both proliferation and differentiation were increased in Zr-GO as compared with that of Zr (P < 0.05). SIGNIFICANCE: GO-coated zirconia inhibited the attachment of S. mutans and stimulated proliferation and differentiation of osteoblasts. Therefore, GO-coated zirconia can prevent peri-implantitis by inhibiting bacterial adhesion. Moreover, its osteogenic ability can increase bone adhesion and success rate of implants.

Bioinspired Camellia japonica carbon dots with high near-infrared absorbance for efficient photothermal cancer therapy.

Since carbon dots (CDs) exhibit excellent biocompatibility, low cytotoxicity, near-infrared (NIR) absorbance, and superior photostability, many types of CDs are considered as powerful candidates for photothermal therapy (PTT) applications. However, the development of a desirable CD is still difficult due to insufficient photothermal conversion, thus resulting in the use of high laser power densities at a high dose of CDs for the PTT effect. Herein, bioinspired sulfur-doped CDs (S-CDs) with strong NIR absorbance were prepared from Camellia japonica flowers via a facile hydrothermal method for enhancing the photothermal conversion efficiency. The as-prepared S-CDs exhibited various advantages including cost-effective preparation, good water-solubility, high biocompatibility, intense NIR absorption, and excellent photothermal effect with robust photostability. Most importantly, the optimal low dose of S-CDs (45 µg mL-1) successfully led to efficient PTT performance with a high photothermal conversion efficiency (55.4%) under moderate laser power (808 nm, 1.1 W cm-2) for safe and effective cancer therapy.

Effect of Zinc Oxide Nanoparticle Addition to Polycaprolactone Periodontal Membranes on Antibacterial Activity and Cell Viability.

During the design of membranes for guided tissue regeneration (GTR) to treat periodontal diseases, infection of the exposed membranes and postoperative complications can be prevented by increasing bacterial resistance. This study evaluated the antibacterial activity of PCL/ZnO membranes and their effect on cell viability via addition of antibacterial zinc oxide (ZnO) nanoparticles to a biocompatible and biodegradable material such as polycaprolactone (PCL). Neat PCL membranes and PCL/ZnO membranes containing 0.5 wt.% and 5 wt.% ZnO were produced, and divided into PCL (0% ZnO), LZ (0.5 wt.% ZnO), and HZ (5 wt.% ZnO) groups, respectively. The surface characteristics of the membranes including morphological features and changes in composition were analyzed. Adhesion of bacteria, including Streptococcus mutans and Porphyromonas gingi-valis, was analyzed using a crystal violet assay. The proliferation of MC3T3-E1 osteoblasts was evaluated using a WST-8 assay. Significant differences were analyzed using the Kruskal-Wallis test (P < 0.05). The results of groups were compared using the Mann-Whitney test (P < 0.017). ZnO nanoparticles were dispersed in the PCL matrix of PCL/ZnO membranes. Compared with neat PCL membranes, their ability to form crystals decreased and their amorphous structure increased. The adhesion of S. mutans and P. gingivalis in the LZ and HZ groups containing ZnO was significantly decreased compared with that of the neat PCL membranes (P < 0.05). No significant differences were observed in the proliferation of MC3T3-E1 cells between the PCL/ZnO membranes and the neat PCL membranes both on days 2 and 5 of culture (P > 0.05). This study has demonstrated that the PCL membranes carrying the ZnO nanoparticles inhibited bacterial adhesion without affecting the viability of osteoblasts, suggesting the potential application of ZnO in GTR to increase antibacterial activity of membranes.

Atomic Layer Deposition of ZrO2 on Titanium Inhibits Bacterial Adhesion and Enhances Osteoblast Viability.

PURPOSE: The study was intended to create a uniform zirconia layer even on the surface of complex structures via atomic layer deposition (ALD). The impact of crystalline zirconia deposited by ALD on bacterial adhesion and osteoblast viability was assessed via surface treatment of dental implants. METHODS: Amorphous zirconia was deposited using an atomic layer deposition reactor (Atomic Classic, CN1, Hwaseong, Korea) on titanium discs. Heating the samples at 400°C resulted in crystallization. Samples were divided into three groups: the control group, the group carrying amorphous ALD-zirconia (Z group), and the heat-treated group following zirconia ALD deposition (ZH group).The surface of each sample was analyzed, followed by the assessment of adhesion of Streptococcus mutans and Porphyromonas gingivalis, and viability and differentiation of MC3T3-E1 cells. RESULTS: The adhesion of S. mutans and P. gingivalis was significantly reduced in the Z and ZH groups compared with the control group (P < 0.05). The viability of MC3T3-E1 cells was significantly increased in the ZH group compared with the control group (P < 0.001), while no significant differences were observed in the Z group (P > 0.05). Differentiation of MC3T3-E1 cells showed a marginally significant increase in the ZH group compared with the control group (P < 0.1), while no significant differences were found in the Z group (P > 0.1). CONCLUSION: Compared with the pure titanium group, the groups that were coated with zirconia via ALD showed a decreased adhesion of S. mutans during the early stages of biofilm formation and P. gingivalis adhesion inducing peri-implantitis, and an increase in MC3T3-E1 cell viability and differentiation. The findings indicate the possibility of treating the implant surface to reduce peri-implantitis and improve osseointegration.

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.

Effect of Atmospheric Pressure Plasma Treatment on Shear Bond Strength Between Zirconia and Dental Porcelain Veneer.

Various surface treatments on zirconia have been reported for dental porcelain veneer. However, it has not been determined which of these treatments provide the highest bond strength. The purpose of this study is to compare the effect of airborne particle abrasion and atmospheric pressure plasma treatment on the shear bond strength between zirconia and dental porcelain veneer. The groups were divided into four groups according to the surface treatment method: the control group, the atmospheric pressure plasma treated group (group P), the airborne particle abrasion group (group A), the atmospheric pressure plasma treated group after the airborne particle abrasion (group AP). Atmospheric pressure plasma was applied on the specimens using a plasma generator (Plasma JET, POLYBIOTECH Co. Ltd., Gwangju, Korea) and airborne-particle abraded with 110 µm. The characteristics of surface treated zirconia were analyzed by 3D-OP, XRD, XPS and contact angle. The shear bond strength was tested using a universal testing machine. The shear bond strength of group P was significantly increased compared to that of the control group (P < 0.05). The shear bond strength of group AP was significantly increased as compared to group A (P < 0.05). There was no significant difference between the group P and group A (P > 0.05). As a result of this study, the atmospheric pressure plasma treatment showed significantly higher shear bond strength than control group, but similar to the airborne particle abrasion, and the atmospheric pressure plasma treatment after the airborne particle abrasion provided the highest shear bond strength. This study demonstrated that application atmospheric pressure plasma treatment on zirconia may be useful for increasing bond strength between zirconia and dental porcelain veneer.

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.

Effect of Plasma Surface Treatment on Shear Bond Strength with Denture Base Resin in Co-Cr Alloy, Ti-6Al-4V Alloy, and CP-Ti Alloy.

The purpose of this study was to examine the effect of plasma treatment by treating the surface of Co-Cr alloy, Ti-6Al-4V alloy, and CP-Ti alloy as a material for denture metal frameworks with non-thermal atmospheric pressure plasma (NTAPP) and measuring their shear bond strength (SBS) with a heat-cured resin. 20 specimens were prepared for each of Co-Cr, Ti-6Al-4V, and CP-Ti alloys. Each metal alloy group was divided into the following subgroups depending on NTAPP treatment: C (Co-Cr alloy without plasma), T (CP-Ti without plasma), A (Ti-6Al-4V alloy without plasma), CP (Co-Cr alloy with plasma), TP (CP-Ti with plasma) and AP (Ti-6Al-4V alloy with plasma). Specimens were treated with a metal conditioner and bonded to a denture base resin. SBS was measured using a universal testing machine. All data obtained were statistically analyzed using two-way analysis of variance (ANOVA), Tukey's honestly significant difference (HSD) test, and independent t-test. The mean values (SD) of SBS (MPa) were: 10.31 (1.19) for C group; 12.43 (0.98) for T group; 13.75 (2.02) for A group; 13.53 (1.61) for CP group; 16.87 (1.55) for TP group; 17.46 (1.65) for AP group. The SBS of the AP group was the highest while that of the C group was the lowest. SBS of specimen treated with NTAPP was significantly increased regardless of metal alloy types (p < 0.001). Within the limitations of this study, NTAPP can increases the SBS of Co-Cr alloy, CP-Ti alloy, and Ti-6Al-4V alloy with a denture base resin.

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.

Effect of Plasma Treatment and Its Post Process Duration on Shear Bonding Strength and Antibacterial Effect of Dental Zirconia.

We have investigated the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment and the post process time on the bonding strength and surface sterilization of dental zirconia. Presintered zirconia specimens were manufactured as discs, and then subjected to a 30-min argon treatment (Ar, 99.999%; 10 L/min) using an NTAPP device. Five post-treatment durations were evaluated: control (no treatment), P0 (immediate), P1 (24 h), P2 (48 h), and P3 (72 h). The surface characteristics, shear bonding strength (SBS) with two resin cements, and Streptococcus mutans biofilm formation of these plasma-treated dental zirconia were tested. Plasma did not change the roughness, and caused surface element changes and surface energy increase. Due to this increase in surface energy, SBS increased significantly (p < 0.05) within 48 h when RelyXTM U200 was used. However, the increase of surface oxygen significantly decreased (p < 0.05) the SBS of Panavia F 2.0 when using plasma immediately (P0). S. mutans adhesion decreased significantly (p < 0.05) for the P0, P1, and P2 groups compared to the control. The P0 group exhibited lower biofilm thickness than the other experimental groups due to the increased hydrophilicity (p < 0.05). Our study suggests that there is a suitable time window for the post NTAPP treatment regarding bonding strength and antimicrobial growth persist.

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.

The effect of plasma on shear bond strength between resin cement and colored zirconia.

PURPOSE: To investigate the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment on shear bond strength (SBS) between resin cement and colored zirconia made with metal chlorides. MATERIALS AND METHODS: 60 zirconia specimens were divided into 3 groups using coloring liquid. Each group was divided again into 2 sub-groups using plasma treatment; the experimental group was treated with plasma, and the control group was untreated. The sub-groups were: N (non-colored), C (0.1 wt% aqueous chromium chloride solution), M (0.1 wt% aqueous molybdenum chloride solution), NP (non-colored with plasma), CP (0.1 wt% aqueous chromium chloride solution with plasma), and MP (0.1 wt% aqueous molybdenum chloride solution with plasma). Composite resin cylinders were bonded to zirconia specimens with MDP-based resin cement, and SBS was measured using a universal testing machine. All data was analyzed statistically using a 2-way ANOVA test and a Tukey test. RESULTS: SBS significantly increased when specimens were treated with NTAPP regardless of coloring (P<.001). Colored zirconia containing molybdenum showed the highest value of SBS, regardless of NTAPP. The molybdenum group showed the highest SBS, whereas the chromium group showed the lowest. CONCLUSION: NTAPP may increase the SBS of colored zirconia and resin cement. The NTAPP effect on SBS is not influenced by the presence of zirconia coloring.

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.