SURFACE-MODIFIED DENTAL ZIRCONIA MATERIAL AND METHOD FOR PREPARING SAME

Abstract

The present invention relates to a dental zirconia material of which the surface is modified by plasma treatment, an implant, and a method for preparing same. The zirconia material and the implant prepared according to the present invention have improved cell adhesion and anti-bacterial effect, and thus can exhibit improved biocompatibility and minimize an inflammatory response of a user and the like.

Claims

1. A zirconia material with a surface modified by plasma treatment.

2. The zirconia material with a surface modified according to claim 1, wherein the material is for dental use.

3. The zirconia material with a surface modified according to claim 1, wherein the material has a surface C/O ratio of 1 to 3.

4. The zirconia material with a surface modified according to claim 1, wherein the plasma is a plasma formed under atmospheric pressure conditions.

5. The zirconia material with a surface modified according to claim 1, wherein the plasma contains N.sub.2 or N.sub.2/Ar as a carrier gas.

6. The zirconia material with a surface modified according to claim 5, wherein the N.sub.2/Ar mixed gas contains N.sub.2 and Ar in a molar ratio of 1 to 5:5 to 50.

7. The zirconia material with a surface modified according to claim 1, wherein the material is treated with plasma for 0.1 second to 10 minutes.

8. A dental titanium implant with a surface modified by plasma treatment.

9. The dental zirconia implant according to claim 8, wherein the implant has a surface C/O ratio of 1 to 3.

10. The dental zirconia implant according to claim 8, wherein the plasma is a plasma formed under atmospheric pressure conditions.

11. The dental zirconia implant according to claim 8, wherein the plasma contains N.sub.2 or N.sub.2/Ar as a carrier gas.

12. A method of modifying the surface of a zirconia material, including the steps of: (a) filling a plasma generating device with a carrier gas; (b) generating plasma in the plasma generating device; and (c) irradiating the generated plasma to zirconia.

13. The method of modifying the surface of a zirconia material according to claim 12, wherein the surface-modified zirconia material has a surface C/O ratio of 1 to 3.

14. The method of modifying the surface of a zirconia material according to claim 12, wherein the material is for dental use.

15. The method of modifying the surface of a zirconia material according to claim 12, wherein the carrier gas is N.sub.2 or N.sub.2/Ar.

16. The method of modifying the surface of a zirconia material according to claim 12, wherein the plasma in step (b) is generated by supplying a voltage of 0.1 kV to 20 kV and a frequency of 10 to 30 kHz to the plasma generating device.

17. The method of modifying the surface of a zirconia material according to claim 12, wherein the plasma generated in step (b) is radiated under conditions of room temperature and atmospheric pressure.

18. The method of modifying the surface of a zirconia material according to claim 12, wherein the plasma in step (c) is irradiated to the zirconia for 0.1 seconds to 10 minutes.

19. A method of manufacturing a surface-modified dental implant, including the steps of: (a) preparing an implant made of zirconia material; (b) filling a plasma generating device with a carrier gas; (c) generating plasma in the plasma generating device; and (d) irradiating the generated plasma to the implant in step (a).

20. The method of manufacturing a surface-modified dental implant according to claim 19, wherein the surface-modified dental implant has a surface C/O ratio of 1 to 3.

21. The method of manufacturing a surface-modified dental implant according to claim 19, wherein the carrier gas is N.sub.2 or N.sub.2/Ar.

22. The method of manufacturing a surface-modified dental implant according to claim 19, wherein the plasma in step (c) is generated by supplying a voltage of 0.1 kV to 20 kV and a frequency of 10 to 30 kHz to the plasma generating device.

23. The method of manufacturing a surface-modified dental implant according to claim 19, wherein the plasma generated in step (c) is radiated under conditions of room temperature and atmospheric pressure.

24. The method of manufacturing a surface-modified dental implant according to claim 19, wherein the plasma in step (d) is irradiated to the implant for 0.1 seconds to 10 minutes.

Description

DESCRIPTION OF DRAWINGS

[0060] FIG. 1 is an image schematically illustrating a method of modifying a surface of a zirconia material according to an embodiment of the present invention.

[0061] FIG. 2 shows the results of confirming the contact angle in water and diiodomethane after irradiating a zirconia specimen with plasma composed of each of Ar, HeO.sub.2, N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0062] FIG. 3 shows the results of separately confirming the surface free energy for a dispersion component and a polar component after irradiating a zirconia specimen with plasma composed of each of Ar, HeO.sub.2, N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0063] FIG. 4 shows the results of separately confirming three-dimensional surface roughness parameters Sa (average), Sq (standard deviation), and Sv (maximum valley depth) after irradiating a zirconia specimen with plasma composed of each of Ar, HeO.sub.2, N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0064] FIG. 5 shows an SEM image after irradiating a zirconia specimen with plasma composed of each of Ar, HeO.sub.2, N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0065] FIG. 6 shows the results of confirming a percentage (at %) of each atom, a concentration of N nitrogen atom, and a carbon/oxygen (C/O) ratio present on the surface after irradiating a zirconia specimen with plasma composed of each of Ar, HeO.sub.2, N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0066] FIG. 7 shows the results of confirming the number of bacteria present on the surface after irradiating a zirconia specimen with plasma composed of each of N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0067] FIG. 8 shows the results of confirming the effect of reducing the adhesion ability of Porphyromonas gingivalis (hereinafter referred to as P. gingivalis) on the surface of zirconia after irradiating a zirconia specimen with plasma composed of N.sub.2/Ar carrier gas according to an embodiment of the present invention.

[0068] FIG. 9 is a schematic diagram of a cell proliferation test experiment according to an embodiment of the present invention.

[0069] FIG. 10 shows the results of confirming the proliferation of osteoblasts over time after irradiating a zirconia specimen with plasma composed of each of N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0070] FIG. 11 shows the results of confirming the motility of osteoblasts over time after irradiating a zirconia specimen with plasma composed of N.sub.2 carrier gas according to an embodiment of the present invention.

[0071] FIG. 12 shows the results of confirming the motility of osteoblasts over time after irradiating a zirconia specimen with plasma composed of N.sub.2/Ar carrier gas according to an embodiment of the present invention.

[0072] FIG. 13 shows the results of confirming the extracellular release of H.sub.2O.sub.2 from osteoblasts over time after irradiating a zirconia specimen with plasma composed of each of N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0073] FIG. 14 shows the results of confirming the extracellular release of NO.sub.2 from osteoblasts over time after irradiating the osteoblasts with plasma composed of each of N.sub.2, and N.sub.2/Ar carrier gases according to an embodiment of the present invention.

[0074] FIG. 15 shows the results of confirming the adhesion ability of osteoblasts over time after irradiating a zirconia specimen with plasma composed of N.sub.2/Ar carrier gas according to an embodiment of the present invention.

[0075] FIG. 16 shows the results of confirming the adhesion ability of osteoblasts over time after irradiating a zirconia specimen with plasma composed of N.sub.2 carrier gas according to an embodiment of the present invention.

BEST MODES OF THE INVENTION

[0076] Hereinafter, the present invention will be described in detail by way of examples in order to aid understanding of the present invention. However, the following examples are only for illustrating the contents of the present invention, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to explain the present invention more completely to those skilled in the art.

[0077] The present invention is to provide a zirconia material having improved cell proliferation ability, adhesion ability and motility, and also having improved antibacterial effect. The zirconia material of the present invention is plasma treated and thus has reduced water contact angle and diodomethane contact angle, and undergo plastic deformation on the surface, resulting in high chemical activity and reactivity. In addition, the zirconia material of the present invention has a low C/O ratio on the surface and thus is highly reactive with cells.

[0078] In the present invention, plasma can be generated by supplying a specific pressure, voltage, or frequency to a carrier gas. The carrier gas in the present invention may be at least one gas selected from the group consisting of nitrogen, helium, argon, and oxygen, but is not limited thereto. Preferably, it may be composed of a mixture of at least two gases among nitrogen, helium, argon, and oxygen, and most preferably, may be nitrogen (N.sub.2) or a mixture of nitrogen and argon (N.sub.2/Ar), but is not limited thereto. In the present invention, the mixture of nitrogen and argon may be a mixture of N.sub.2 and Ar in a molar ratio of 1 to 5:5 to 50, preferably in a molar ratio of 1:9.

[0079] The plasma of the present invention can be generated by supplying a voltage of 0.1 kV to 20 kV and/or a frequency of 10 to 30 kHz to the carrier gas. Most preferably, it can be generated by applying a voltage of 5 kV and/or a frequency of 25 kHz.

[0080] In the present invention, surface modification refers to imparting physical, chemical, and biological properties that were not present in an original material to the surface of the material. In the present invention, by plasma treatment, the water contact angle and diodomethane contact angle on the surface of the zirconia material are reduced, plastic deformation occurs on the surface, thereby increasing chemical activity and reactivity, lowering C/O ratio, and thus increasing reactivity with cells.

[0081] According to one embodiment of the present invention, the water contact angle and diiodomethane contact angle on the zirconia surface are overall reduced by plasma treatment (see FIGS. 1 and 2). In particular, when treated with plasma, the surface free energy increases, and in particular, in the case of plasma composed of N.sub.2/Ar (as a carrier gas), the polar component (.sup.p) increases (see FIG. 3), indicating that the surface-modified zirconia material according to the present invention has improved cell adhesion ability.

[0082] In addition, according to an embodiment of the present invention, in the case of zirconia whose surface was modified by plasma treatment, there is no significant difference in surface roughness (see FIG. 5), but in the case of plasma composed of N.sub.2/Ar (as a carrier gas), plastic deformation occurs, accelerating oxygen uptake on the surface of the modified material, and increasing chemical activity (chemical reactivity) and reactivity (kinetics of surface reactions).

[0083] The composition of the surface of zirconia whose surface has been modified according to the present invention may vary depending on plasma treatment. When treated with plasma using N.sub.2/Ar as a carrier gas according to an embodiment of the present invention, the carbon/oxygen (C/O) ratio on the zirconia surface is as low as 1 to 3, 1.5 to 3, or 2 to 3, resulting in increased reactivity with cells (see FIG. 6).

[0084] In the case of the zirconia material whose surface is modified according to the present invention, the antibacterial effect increases and the adhesion ability of bacteria decreases, making it suitable for use as a dental material. The zirconia material of the present invention has an antibacterial effect against bacteria existing in the oral cavity, and has an antibacterial (sterilizing) effect against at least one bacterium selected from the group consisting of Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola (see FIGS. 7 and 8).

[0085] In addition, the zirconia material manufactured according to the present invention has improved cell proliferation ability, cell motility, and cell adhesion ability in relation to cells (preferably, osteoblasts), making it suitable for use as a medical material. As described above, the zirconia material of the present invention has improved cell proliferation ability, motility, and adhesion ability in reactions with osteoblasts, and thus, the effectiveness of bone formation and osseointegration is improved when used as a dental material (see FIGS. 10 to 16).

[0086] In the present invention, treatment with plasma refers to irradiating zirconia (or a specific material made of zirconia) with plasma. In the present invention, the plasma may be radiated under conditions of room temperature and atmospheric pressure, and may be irradiated to the zirconia at a distance of 10 mm for 0.1 seconds to 10 minutes, preferably 60 seconds.

[0087] The zirconia material of the present invention may be used as a dental material, and may be used for implants, crowns, inlays, posts, and orthodontic brackets, and most preferably, as a dental implant material, but is not limited thereto.

[0088] A dental implant generally refers to a replacement that restores the original function of a tooth by implanting and adhering a fixture to an alveolar bone from which the natural tooth root has come out to replace the lost tooth root, and then fixing an artificial tooth on top of the fixture.

[0089] In the present invention, dental zirconia implant with a surface modified by plasma treatment may be made of the zirconia material with a modified surface, or may be manufactured by treating an implant made of zirconia with plasma.

[0090] Hereinafter, the present invention will be described in more detail by way of examples. These examples are only for illustrating the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not interpreted as limited by these examples.

Statistical Analysis

[0091] Statistical significance of the data was assessed by one-way analysis of variance (ANOVA) with Tukey's honesty significant difference (HSD) post hoc test at =0.05. All analyzes were performed using statistical software (IBM SPSS Statistics, v25.0, IBM Corp., Chicago, IL, USA).

Example 1

Sample Preparation and Plasma Surface Treatment

[0092] In the present invention, 3Y-TZP (KATANA ML, Kuraray Noritake Dental, Osaka, Japan) sintered at 1500 C. for 2 hours was used. A total of 140 plate-shaped samples (10.0 mm10.0 mm1.0 mm) were prepared and polished with a uniform finish using 800 grit SiC paper. After ultrasonic washing for 20 minutes, plasma irradiation was performed at room temperature using a low-temperature atmospheric pressure DBD plasma generator (PR-ATO-001, ICD Co., Anseong, Gyeonggi-do, Korea). Plasma was applied perpendicular to the sample surface at a distance of 10 mm for 60 seconds. A schematic diagram of the device used in the experiment is shown in FIG. 1. All samples were randomly assigned to five groups (n=28), wherein four groups were treated with plasmas composed of four different gases (Ar, N.sub.2, N.sub.2/Ar mixture (10% nitrogen/90% argon), and He/O.sub.2 mixture (15% helium/85% oxygen), and one group was used as a control without plasma treatment. The input voltage was fixed at 5 kV using a high-voltage transformer, and the operating frequency was set to 25 kHz using a digital oscilloscope (MSO4032, Tektronix, Beaverton, OR, USA). The mass flow controller maintained a constant gas flow rate of 10 standard liters per minute (slm).

Example 2

Analysis of Properties of Zirconia Surface after Plasma Treatment

2-1. Confirmation of Changes in Surface Contact Angle and Surface Free Energy According to Plasma Treatment

[0093] The surface wettability of the samples was measured using a contact angle meter (Phoenix 300 Touch, S.E.O., Suwon, Gyeonggi-do, Korea). The contact angle was measured by the sessile drop technique at room temperature and 60% relative humidity using distilled water (n=10) and nonpolar diiodomethane (n=10), and all measurements were performed at the center of the samples.

[0094] The surface free energy was calculated by measuring the contact angle of two liquids (distilled water and nonpolar diodomethane) according to the Owens-Wendt equation. The total surface free energy (.sup.total) including the dispersion component (.sup.d) and the polar component (.sup.p) was calculated.

[0095] FIGS. 2 and 3 show sessile drop images (FIG. 2) and contact angles together with total, d, and p values (FIG. 3) of zirconia samples treated with plasma made of different types of gases, respectively, and the measured contact angles are shown in Table 1. After exposure to plasma, the water contact angle of all samples significantly decreased, and the lowest value of 69 was measured in the sample treated with plasma composed of nitrogen and argon mixed gas (N.sub.2/Ar). In all plasma-treated samples except for argon (Ar), the contact angle of diodomethane is maintained almost constant (FIG. 2 and Table 1). In all samples, the total surface energy was greatly increased after the plasma treatment, which was mainly consistent with an increase in .sup.p value, and the .sup.p value was most greatly increased in the sample treated with plasma composed of nitrogen and argon mixed gas (N.sub.2/Ar) (FIG. 3).

[0096] The contact angles of the zirconia specimens treated with plasma according to the present invention are shown in Table 1 below. In Table 1, the average with the same superscripts in each column are not significantly different from each other according to Tukey's honest significant difference post hoc test (p>0.05).

TABLE-US-00001 TABLE 1 Contact angle() Plasma group Water Diiodomethane Control 98.75 2.70.sup.a 45.66 4.30.sup.d,e HeO.sub.2 75.59 3.38.sup.b 44.72 3.16.sup.e N.sub.2/Ar 69.00 3.98.sup.c 49.39 3.33.sup.d N.sub.2 76.86 3.30.sup.b 47.21 4.14.sup.d,e Ar 73.22 3.00.sup.b 39.60 3.19.sup.f

2-2. Surface Shape Change

[0097] Three-dimensional (3-D) surface properties were analyzed using a confocal laser scanning microscope (CLSM; LEXT OLS3000, Olympus, Tokyo, Japan) at 50 magnification in an area of 256192 m.sup.2 (n=5). Surface texture parameters, in particular arithmetic mean height Sa; root mean square height, Sq; and maximum pit height Sv were calculated according to ISO 25,178. Surface analysis was performed independently at two locations in the center, and a total of 10 measurements were made for each sample treated with plasma composed of different types of gases.

[0098] The surface microstructure of the samples was evaluated using a scanning electron microscope (SEM; JSM-7800F Prime, JEOL, Tokyo, Japan) at an acceleration voltage of 5.0 kV and a working distance (WD) of 6.0 mm at 3000, 10,000, and 30,000 magnification (n=1).

[0099] Enlarged confocal images and SEM images of samples treated with plasma composed of different types of gases are shown in FIG. 5. The surface texture parameters Sa, Sq and Sv measured in CLSM are shown in FIG. 4.

[0100] Referring to FIG. 4, as a result of analyzing the surface roughness, there was no statistically significant difference between the surface roughness of the zirconia surface after plasma treatment and the surface roughness before plasma treatment, and as a result of checking the SEM images after each plasma treatment in FIG. 5, all four plasma treatments also did not change the surface shape of zirconia.

[0101] Accordingly, it was confirmed as follows whether chemical changes exist on the zirconia surface when treated with plasma.

2-3. Confirmation of Chemical Changes

[0102] The elemental composition of zirconia samples treated with plasma composed of different types of gases was analyzed using a monochromatic Al K X-ray source (1486.6 eV) at 12 kV and 3 mA through X-ray photoelectron spectroscopy (XPS) (K-alpha, Thermo Fisher Scientific Inc., Waltham, MA, USA) (n=1). Additionally, data were collected and core-level spectra were analyzed using software (Thermo Avantage v5.980, Thermo Fisher Scientific Inc., Waltham, MA, USA). All XPS spectra were calibrated to a C Is peak at 284.6 eV.

[0103] FIGS. 6 and 7 show the atomic percentages (at %) of the carbon, oxygen, nitrogen, zirconium (Zr), and yttrium (Y), respectively, as determined by XPS, and FIG. 8 shows the carbon/oxygen ratios in all samples. Referring to FIG. 8, the zirconia surface treated with N.sub.2Ar plasma had the highest oxygen (O) and nitrogen (N) components and the lowest C/O ratio. This suggests that the zirconia surface treated with N.sub.2Ar plasma has high reactivity with cells.

[0104] In conclusion, referring to FIG. 8, it can be seen that the value of the C/O ratio is lowered in the case of the zirconia sample whose surface was modified by plasma treatment according to the present invention, suggesting that the zirconia surface treated with plasma composed of N.sub.2 gas has high reactivity with cells.

Example 3

Confirmation of P. gingivalis Sterilization Effect on Zirconia Surface by Plasma Treatment

[0105] As a result of analyzing the characteristics of the zirconia surface treated with each of four types of plasma (Ar, HeO.sub.2, N.sub.2, N.sub.2Ar) for 1 minute, N.sub.2Ar, the plasma with the highest surface energy, and the control (N.sub.2) were selected, and the sterilizing power of each plasma against P. gingivalis bacteria was measured. N.sub.2 plasma, which induced high sterilizing power and reduced adhesion to P. gingivalis when treating zirconia, was used as a control.

[0106] After P. gingivalis was smeared on the zirconia surface, each plasma was irradiated and the number of bacteria over time was measured.

[0107] The experimental process according to this example is as follows. First, the bacteria stored in a deep freezer were taken out and thawed at room temperature, and then, the stored bacteria were diluted in ImL TSB medium (tryptic soy broth) so as to become 2*10.sup.5 bacteria. Thereafter, they were washed twice with DW/PBS (all of glycerol, a storage solvent, was removed through the washing process) (1 ml of DW.fwdarw.vortex.fwdarw.removal of DW was repeated twice). After washing, 1 ml of TSB medium (tryptic soy broth) was added and mixed well so that the bacteria were homogeneous. Afterward, 100 ul was picked (10.sup.4) and smeared on the medium using a spreader. After smearing, it was treated with plasma according to each plasma treatment time (10 minutes, 20 minutes, 30 minutes) and then incubated at a temperature of 37 degrees.

[0108] When counting the number of bacteria in this example, 2 to 3 plates were smeared for each sample and then each plate was counted. The control sample was set to grow 10,000 colonies on the plate through several experiments, and then the experiment was performed in the same amount. When counting (counting 100 or more), the bacteria within 1 cm.sup.2 were counted for each plate according to the dense plate measurement method and then multiplied by 65 to calculate the number of bacteria on the plate, which was shown in FIG. 7 (unit: cfu/ml).

[0109] Referring to FIG. 7, no bacteria remained on the zirconia specimen when treated with N.sub.2 plasma for 10 minutes (zero, 100% sterilization effect). In the case of N.sub.2Ar plasma, there was a sterilization effect of 93% when treated for 10 minutes, a sterilization effect of 98.5% when treated for 20 minutes, and a sterilization effect of 100% when treated for 30 minutes.

[0110] That is, according to this example, when the zirconia is treated with N.sub.2 or N.sub.2Ar plasma, the growth of harmful bacteria, including P. gingivalis, may be inhibited. It can be seen that the antibacterial (sterilization) effect of the surface-modified zirconia and the surface-modified dental zirconia implant according to the present invention is improved.

Example 4

Confirmation of the Effect of Plasma Treatment on Reducing P. gingivalis Adhesion to the Zirconia Surface

[0111] In this example, the effect of reducing the adhesion of P. gingivalis to the zirconia surface treated with N.sub.2/Ar plasma was measured.

[0112] First, a certain amount of P. gingivalis was applied to zirconia specimens that had been treated with N.sub.2/Ar plasma for 10, 20, and 30 minutes, respectively, and reacted for about 30 minutes. Afterward, the bacteria in the reacted specimens were washed, placed in a culture medium, and smeared on a solid medium. The smeared medium was cultured for one day to measure the bacterial CFU (number of viable microorganisms per 1 mL (Colony Forming Unit, CFU)). The results are shown in FIG. 8.

[0113] Referring to FIG. 8, among the zirconia specimens treated with N.sub.2/Ar plasma for 10, 20, and 30 minutes, the zirconia specimen treated for 30 minutes showed a 10% decrease in P. gingivalis adhesion (90% remained).

[0114] That is, it can be seen that when treated with the plasma made of N.sub.2/Ar gas, there is an effect of weakening the adhesion of bacteria on the surface of the material.

Example 5

Confirmation of Osteoblast Proliferation Ability (Cell Proliferation) on Zirconia Surface by Plasma Treatment

[0115] When each zirconia sample was treated with N.sub.2 or N.sub.2/Ar plasma for 30 seconds under 10% FBS conditions, approximately 0.4% of osteoblasts were proliferated in the case of plasma composed of N.sub.2 compared to the control, and 11% of osteoblasts were proliferated in the case of N.sub.2/Ar plasma compared to the control. In addition, when treated with each plasma for 60 seconds, it could be confirmed that about 10% of osteoblasts were proliferated when treated with N.sub.2 plasma, and about 11% of osteoblasts were proliferated when treated with N.sub.2/Ar plasma (see FIGS. 9 and 10).

[0116] Under the 1% FBS condition, there was no statistical significance in the N.sub.2 condition compared to the control, and 0.3% and 15% of osteoblasts were proliferated when treated for 30 seconds and 60 seconds under the N.sub.2Ar condition, respectively. That is, it can be seen that the N.sub.2/Ar plasma can contribute to cell proliferation activation of osteoblasts.

Example 6

Confirmation of Osteoblast Motility on Zirconia Surface by Plasma Treatment

[0117] In this example, the motility (migration effect) of osteoblasts on the zirconia surface treated with N.sub.2 or N.sub.2/Ar plasma was confirmed. When treated with N.sub.2 plasma for 30 or 60 seconds according to this example, no effect was observed (see FIG. 11), but when treated with N.sub.2Ar plasma for 30 seconds, the migration of osteoblasts was confirmed (FIG. 12). In this case, however, it can be confirmed that extracellular H.sub.2O.sub.2 did not appear (see FIG. 13), but when comparing extracellular NO.sub.2 over time, the NO.sub.2 was expressed significantly higher in N.sub.2Ar plasma than in N.sub.2 plasma (see FIG. 14).

[0118] That is, it can be seen that according to this example, the motility of osteoblasts is improved on the zirconia surface treated with N.sub.2 or N.sub.2/Ar plasma.

Example 7

Confirmation of Osteoblast Adhesion Ability on Zirconia Surface by Plasma Treatment

[0119] In this example, MC-3T3E1 cell (mouse osteoblast cell) was used as a cell line in order to confirm the osteoblast adhesion ability on the zirconia surface by plasma treatment. Alpha MEM+10% fetal bovine serum (FBS) was used as a culture medium, and each sample was pretreated with N.sub.2 or N.sub.2Ar plasma for 10 and 20 minutes, respectively, and then 210.sup.4 cells were seeded. Afterward, SYTOX staining (green staining (nucleus stain, 1:30,000)) was performed for 15 minutes, and the cell adhesion ability was confirmed by dividing the field of the zirconia sample.

[0120] Referring to FIG. 15, there was no change in the cell number of osteoblasts on the zirconia specimen when treated with N.sub.2 plasma for 10 minutes, and there was no change in the cell number of osteoblasts even in the zirconia treated for 20 minutes.

[0121] On the other hand, there was no increase in the cell number of osteoblasts on the zirconia specimens when treated with N.sub.2Ar plasma for 10 minutes, but the cell number of osteoblasts increased in the zirconia treated for 20 minutes (see FIG. 16). That is, the adhesion ability of osteoblasts appears to be higher in N.sub.2/Ar plasma.

[0122] In other words, it can be seen that the adhesion ability of osteoblasts appears on both the surfaces of zirconia treated with N.sub.2 plasma and N.sub.2/Ar plasma, but is higher when treated with N.sub.2/Ar plasma.

[0123] It is to be understood that the description of the present invention described above is for illustrative purposes only, and can be easily modified into other specific embodiments by those of ordinary skill in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the examples described above are illustrative in all respects and not restrictive.