WO2020204254A1 - Method for manufacturing hydroxyapatite-coated zirconia implant by means of dip coating using hydroxyapatite sol - Google Patents

Abstract

The present invention relates to: a method for manufacturing a hydroxyapatite-coated zirconia implant, comprising a step of performing dip coating in a hydroxyapatite sol, thereby forming a hydroxyapatite sol coating layer on the entire surface of or a part of the surface of a zirconia implant, and then sintering same at a controlled temperature; and an implant having improved biocompatibility, manufactured thereby.

Description

Manufacturing method of hydroxyapatite coated zirconia implant by dip coating using hydroxyapatite brush

The present invention comprises the step of forming a hydroxyapatite sol coating layer on all or part of a zirconia implant surface by dip coating on a hydroxyapatite brush and then sintering at a controlled temperature, a method for producing a hydroxyapatite-coated zirconia implant, and The present invention relates to an implant having improved biocompatibility.

Titanium and its alloys are widely used in dental implants as materials with excellent biocompatibility and excellent mechanical strength. However, since it is a metal and an aesthetic problem caused by a black gray surface different from that of the teeth, problems such as non-specific immune response and autoimmunity may occur, and side effects such as galvanic corrosion caused by biomaterials such as saliva have been reported.

On the other hand, dental implants using ceramic materials have the advantage of having less corrosion or immune reactions because they have excellent aesthetic effects with a color similar to that of teeth, and have little ion emission. However, conventional ceramic materials have poor mechanical properties and are easily damaged when force is applied. In order to overcome this, recently, dental implants using zirconia having excellent mechanical properties have been studied. Zirconia implants are not reactive enough to solve problems arising from metal implants. In particular, zirconia stabilized using yttrium has excellent fracture resistance and flexural strength, so it is suitable for use as a dental implant.

However, zirconia itself is not suitable for use for implantation in the body due to poor biocompatibility. In addition, bone compatibility is also poor, which is insufficient for use as a dental implant. Therefore, in order to overcome this, a surface treatment method such as adjusting the surface roughness or coating the surface with another material has been used.

Hydroxyapatite is a ceramic that exists a lot in the human body and is the main component of teeth and bones. Therefore, hydroxyapatite is a material having very excellent biological properties, especially bone compatibility. Accordingly, as a surface treatment method for imparting biocompatibility to the zirconia, a method of coating the surface of zirconia using a hydroxyapatite-based ceramic has been proposed. In this regard, a method of coating hydroxyapatite on the surface of the zirconia implant through plasma treatment, or coating the intermediate layer of zirconia and hydroxyapatite using fluorinated hydroxyapatite to prevent the reaction of zirconia and hydroxyapatite during sintering, etc. Was suggested. However, the method of coating through plasma treatment has disadvantages that the zirconia itself is damaged and the coating layer is formed too thick, and the method of using fluorinated hydroxyapatite in the intermediate layer repeats the process of coating with several materials. Therefore, there is a disadvantage in that the process is cumbersome and problems such as adhesion may occur.

As a result of intensive research efforts to discover a simple process for introducing a hydroxyapatite coating layer on the surface of a zirconia-based dental implant, the present inventors made thin hydroxyapatite directly on the surface of a zirconia implant by dip coating using a hydroxyapatite brush of an appropriate concentration. Forming a coating layer, but by controlling the sintering temperature, it was confirmed that hydroxyapatite coating was possible in which by-products were blocked by the reaction of zirconia and hydroxyapatite without an intermediate layer including fluorinated hydroxyapatite, etc. Completed.

One object of the present invention is a first step of preparing a hydroxyapatite sol by mixing a triethylphosphite solution and a calcium nitrate tetrahydrate solution; A second step of forming a hydroxyapatite brush coating layer on the entire or part of the surface of the zirconia implant by dip coating on the hydroxyapatite brush; And a third step of sintering at 650 to 950° C. to provide a method of manufacturing a hydroxyapatite coated zirconia implant.

Another object of the present invention is to provide an implant with improved bone compatibility, comprising a hydroxyapatite coating layer formed to a thickness of 100 to 1000 nm on all or part of the surface of a zirconia implant.

The manufacturing method of the present invention does not generate a by-product due to the reaction of hydroxyapatite and zircotia without an intermediate layer containing fluorinated hydroxyapatite by dip coating hydroxyapatite sol at an appropriate concentration and sintering at a controlled temperature. By evenly coating with a thin thickness within a micron, it is possible to provide a zirconia implant with remarkably improved biocompatibility and bone compatibility while maintaining the strength and non-reactivity of the zirconia implant.

1 is a diagram schematically showing a method of manufacturing a hydroxyapatite sol according to an embodiment of the present invention and a method of manufacturing a zirconia implant having a hydroxyapatite coating layer formed thereon by dip coating using the same.

Figure 2 is a diagram showing the X-ray diffraction pattern of the zirconia implant and the zirconia implant itself by dip coating the hydroxyapatite sol and then sintering at 600, 800 and 1000°C, respectively, to form a hydroxyapatite coating layer on the surface.

3 is a diagram showing the results of observing the surfaces of zirconia implants and untreated zirconia implants formed with a hydroxyapatite coating layer on the surface by dip coating hydroxyapatite sol and then sintering at 800°C with a scanning electron microscope.

4 is a scanning electron microscope image of a cross section of a zirconia implant and an untreated zirconia implant in which a hydroxyapatite coating layer was formed on the surface by dip coating a hydroxyapatite brush and then sintered at 800°C, and the thickness of the coating layer measured by a focused ion beam Is a diagram showing.

5 is a hydroxyapatite brush dip coated and then sintered at 800°C to measure the bonding strength with a stud and a tensioner having adhesion to a zirconia implant and an untreated zirconia implant having a hydroxyapatite coating layer formed on the surface, followed by separation It is a diagram showing an image of a part that has been observed under a scanning electron microscope.

6 is a diagram showing the measured bonding strength of a zirconia implant and an untreated zirconia implant in which a hydroxyapatite coating layer was formed on the surface by dip coating a hydroxyapatite sol and then sintering at 800°C.

Figure 7 shows the results of observing cell adhesion on a zirconia implant and an untreated zirconia implant having a hydroxyapatite coating layer formed on the surface by dip coating a hydroxyapatite brush and then sintering at 800°C with a confocal laser scanning microscope. It is a diagram shown.

Figure 8 is a diagram showing the proliferation of osteoblasts on a zirconia implant and an untreated zirconia implant in which the hydroxyapatite sol was dip coated and then sintered at 800°C to form a hydroxyapatite coating layer on the surface.

Figure 9 shows the image of the tissue after 4 weeks by dip coating the hydroxyapatite sol and then sintering at 800°C to form a hydroxyapatite coating layer on the surface of the zirconia implant and the untreated zirconia implant into the rabbit tibia. Is also.

Figure 10 is a hydroxyapatite sol after dip coating and sintering at 800 °C to form a hydroxyapatite coating layer on the surface of the zirconia implant and the untreated zirconia implant inserted into the rabbit shin bone and measured after 4 weeks bone and implant It is a diagram showing the contact degree and the area of the bone.

As one aspect for achieving the above object, the present invention is a first step of preparing a hydroxyapatite sol by mixing a triethylphosphite solution and a calcium nitrate tetrahydrate solution; A second step of dip coating the hydroxyapatite sole to form a hydroxyapatite sol coating layer on all or part of the surface of the zirconia implant; And it provides a method for producing a hydroxyapatite-coated zirconia implant comprising a third step of sintering at 650 to 950 °C.

The zirconia implant may be zirconia having a stabilized tetragonal structure including yttrium. The zirconia containing yttrium is a zirconia composite having very improved physical properties compared to conventional zirconia, and may be a ceramic composite containing yttrium at 4% or less of the total mass and zirconia at 90% or more. In addition, the zirconia implant may contain less than 6% of the total mass of the total complex of materials other than yttrium, but is not limited thereto.

The hydroxyapatite is a mineral that occurs in nature having a formula of Ca ₅ (PO ₄ ) ₃ (OH), and since a crystal unit cell consists of two individuals, Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ is also used. Hydroxyapatite is a hydroxyl endmember of the complex apatite group, and the OH ^- group may be substituted with fluoride, chloride or carbonate. The crystalline form is hexagonal and pure hydroxyapatite is white. The hydroxyapatite of the present invention may be in a form containing not only pure hydroxyapatite but also the above derivatives, derivatives substituted with silicon, and other metals or ceramics, but is not limited thereto.

The present invention is designed to discover a simple process of introducing a thin and even hydroxyapatite coating layer on the surface of a zirconia-based dental implant in order to improve biocompatibility.After dip coating using a hydroxyapatite brush of an appropriate concentration, at a predetermined temperature It is based on the finding that, by sintering, a thin and even coating is possible without an intermediate layer containing fluorinated hydroxyapatite or the like, without producing a by-product by the reaction of zirconia and hydroxyapatite.

The conventional method of forming the hydroxyapatite coating layer includes sintering at a high temperature of 1000° C. or higher in order to finally crystallize the hydroxyapatite. However, in modifying the surface of a zirconia-based implant, in the case of introducing and sintering a hydroxyapatite coating layer directly on the surface of the implant, it is inevitable to produce calcium zirconate, a by-product due to the reaction of zirconia and hydroxyapatite at high temperature. . Therefore, as a method to block the generation of such by-products, a method including fluorinated hydroxyapatite in the intermediate layer is used, but this requires an additional process, which is cumbersome, and the coating layer is inevitably thickened due to the intervention of the intermediate layer. It is difficult to control the thickness of the material, so it is difficult to apply it to parts that require a microstructure.

Accordingly, the present invention is characterized by discovering a coating method that directly introduces a hydroxyapatite coating layer on the surface of a zirconia implant, but does not generate by-products by lowering the sintering temperature.

In a specific embodiment of the present invention, as a result of analyzing the components of the hydroxyapatite coating layer formed by controlling the sintering temperature through X-ray diffraction, when sintering at a low temperature of less than 650°C, for example, 600°C, a low crystallinity is shown. It was confirmed that it may be difficult to exhibit the desired degree of biocompatibility improvement effect, and when sintering at a high temperature exceeding 950°C, such as 1000°C, calcium zirconate, a by-product produced by the reaction of zirconia and hydroxyapatite, is produced. It was confirmed that it became (Fig. 2).

For example, the manufacturing method of the present invention does not include the step of introducing an intermediate layer of fluorinated hydroxyapatite between the zirconia implant surface and the hydroxyapatite coating layer, but does not produce calcium zirconate, a by-product. To this end, by adjusting the concentration of hydroxyapatite sol to prepare suitable for dip coating, and by sintering the zirconia implant coated with hydroxyapatite sol to a predetermined thickness at a relatively low temperature of less than 1000℃, calcium zirconate It can prevent creation.

For example, the concentration of the triethylphosphite solution used in the preparation of hydroxyapatite sol for dip coating may be used to be 0.1 to 1 M based on the total mixed solution, and at this time, calcium nitrate tetrahydrate is the triethyl phosphite solution. It can be used in a molar concentration of 1.5 to 1.8 times that of ethyl phosphite. For example, the triethyl phosphite solution and the calcium nitrate tetrahydrate solution may each independently have a concentration of 0.1 to 1 M, but are not limited thereto. However, if the concentration of these solutions is less than 0.1 M, it may be difficult to form a coating layer by dip coating or to form a coating layer with a uniform thickness due to the thin concentration of the resulting brush. During dip coating, it may be difficult to form a coating layer with a uniform thickness.

For example, the first step may be achieved by mixing a triethyl phosphite solution and a calcium nitrate tetrahydrate solution at room temperature for 1 to 5 days, and optionally aging at 25 to 50°C for 6 hours to 7 days. have. At this time, when the aging period exceeds 7 days, the hydroxyapatite particles may overgrow, and a non-uniform coating layer may be formed during dip coating.

For example, in the second step, the dip coating using the hydroxyapatite sol may be performed at a rate of 0.1 to 10 mm per minute, but is not limited thereto.

Further, the dip coating may be performed once or repeatedly performed 2 to 9 times, but is not limited thereto, and the number of repetitions may be adjusted until a desired thickness is achieved. However, if the number of coatings exceeds 9, it is difficult to form a coating layer with an appropriate thickness, and the stability and uniformity of the coating layer may be adversely affected.

As described above, when dip coating is repeatedly performed, a step of spinning to remove excess sol solution may be additionally included. The spinning may be performed for 10 to 30 seconds at 100 to 300 rpm after dip coating is repeated every 2 to 4 times, but is not limited thereto. In addition, the spinning may be performed 1 to 3 times. On the other hand, since excessive spinning may rather inhibit the formation of a uniform coating layer, the spinning cycle, the number of times, and conditions may be appropriately changed by a person skilled in the art in consideration of the amount and concentration of the remaining sol solution.

For example, the manufacturing method of the present invention uses a solution excluding hydroxyapatite particles. In order to remove, after the second step, a step of drying at 60 to 90°C may be further included. The drying may be performed for 6 hours to 2 days, but is not limited thereto.

In addition, the present invention provides an implant with improved bone compatibility, including a hydroxyapatite coating layer formed to a thickness of 100 to 1000 nm on all or part of the surface of the zirconia implant.

When the thickness of the coating layer is less than 100 nm or more than 1000 nm, the uniformity and/or stability of the coating may be deteriorated, and it may be difficult to ensure the stability of the coating layer structure itself.

The implant having improved bone compatibility of the present invention may be manufactured by the above-described hydroxyapatite-coated zirconia implant manufacturing method.

For example, the implant of the present invention may be a dental implant.

In particular, the implant of the present invention may have a coating layer formed on a screw portion that comes into contact with a bone when inserted into the body.

The implant of the present invention is characterized by improved bone regeneration ability compared to the zirconium implant itself by the introduction of a hydroxyapatite coating layer. In a specific embodiment of the present invention, the adhesion and/or proliferation of osteoblasts is improved through cell experiments around the hydroxyapatite-coated zirconia implant according to the present invention compared to the non-treated zirconia implant itself. It was confirmed that the contact and/or bone area was increased (FIGS. 9 and 10).

In addition, the implant of the present invention is characterized in that it does not include an intermediate layer made of fluorinated hydroxyapatite between the surface of the zirconium implant and the hydroxyapatite coating layer. Introduction of the intermediate layer not only makes the process cumbersome, but also increases the thickness of the coating layer due to the presence of an additional layer, making it difficult to control and implement a microstructure.

Furthermore, the implant of the present invention is characterized in that it does not contain calcium zirconate, a by-product produced by the reaction of zirconium and hydroxyapatite, without an intermediate layer of fluorinated hydroxyapatite between the zirconium implant surface and the hydroxyapatite coating layer.

Hereinafter, the present invention will be described in more detail through examples. These examples are for explaining the present invention more specifically, and the scope of the present invention is not limited by these examples.

Preparation Example 1: Preparation of hydroxyapatite sol by sol-gel method

In order to prepare hydroxyapatite sol for implant coating, triethylphosphite was dissolved in ethanol at a concentration of 0.6 molar and calcium nitrate tetrahydrate at a concentration of 1 molar, and then for 3 days. It was mixed at room temperature. Thereafter, aging was performed at 37° C. for 1 day to prepare hydroxyapatite sol.

Example 1: Formation of hydroxyapatite coating layer by dip coating

Step 1 : In order to form the hydroxyapatite coating layer on the dental zirconia implant, dip coating was performed using the hydroxyapatite brush prepared according to Preparation Example 1. Specifically, the dip coating was performed 9 times at a speed of 0.5 mm per minute, and the excess brush solution was removed by spinning once every 3 times. Then, the solution was dried at 70° C. for one day to remove the solutions excluding the hydroxyapatite particles.

Step 2 : Since the particles present in the hydroxyapatite brush coated on the implant are not yet high in crystallinity, sintering was performed to increase the crystallinity. Specifically, the dried hydroxyapatite brush-coated zirconia implant obtained from step 1 was put into a furnace and sintered. At this time, the temperature was adjusted to 600, 800 and 1000°C and sintered for 1 hour each, and the effect according to the sintering temperature was confirmed.

Experimental Example 1: Confirmation of Components and Form of Coating Layer

In addition to the three samples prepared by adjusting the sintering temperature according to Example 1 (600, 800 and 1000°C, respectively), as a negative control, a zirconia implant without a hydroxyapatite coating layer was used. First, components and/or structures were confirmed through X-ray diffraction analysis of each specimen, and the results are shown in FIG. 2. As shown in Figure 2, compared with the negative control group, the three samples of Example 1 additionally showed hydroxyapatite-related peaks, and among these, the reaction between zirconia and hydroxyapatite at high temperatures was observed in the samples sintered at 1000°C. Calcium zirconate, which is a by-product formed by, was produced, and the specimen sintered at 600° C. showed somewhat low crystallinity. Therefore, in the subsequent in vitro and in vivo experiments, a product sintered at 800°C was used.

Further, in order to confirm the shape of the hydroxyapatite coating layer formed on the implant surface, the surface and cross section were observed with a scanning electron microscope, and the thickness of the coating layer was confirmed with a focused ion beam, and the results are shown in FIGS. 3 and 4, respectively. As shown in FIG. 4, the hydroxyapatite coating layer introduced on the surface of the zirconia implant was formed with a uniform thickness of 400 nm on average.

Experimental Example 2: Checking the stability of the coating layer

In order to confirm the stability of the hydroxyapatite coating layer formed on the surface of the zirconia implant according to Example 1, the bonding force of the coating layer to the implant surface was measured using a stud and a tensioner having adhesive strength. Specifically, in the zirconia specimen (negative control group) and the specimen (Example) in which the hydroxyapatite ceramic coating layer was formed, the separated part of the adhesive and the specimen was observed with a scanning electron microscope, and the results are shown in FIG. As shown in FIG. 5, the remaining adhesive was confirmed, indicating that a bonding force greater than the bonding force between the adhesive and the stud exists between the coating layer and zirconia. Furthermore, the measured bonding force is shown in FIG. 6. At this time, the measured bonding force was about 40 MPa, which means the bonding force between the adhesive and the stud, and thus it was confirmed that the zirconia and hydroxyapatite coating layer were attached with a greater bonding force. The bonding force in the negative control zirconia itself was also measured to be about 40 MPa, which supports that the bonding force between the aforementioned zirconia and hydroxyapatite coating layer exceeds 40 MPa.

Experimental Example 3: Cell Characteristics Confirmation

In order to confirm the cellular characteristics of the zirconia implant prepared with the hydroxyapatite coating layer prepared according to Example 1, osteoblasts were dispensed onto the coated implant and cultured for 1 day. For comparison, cell culture was performed in the same manner for the zirconia implant without the coating layer. After 1 day, the morphology of the cultured cells was confirmed with a confocal laser scanning microscope, and the results are shown in FIG. 7. As shown in FIG. 7, more cells were attached to the implant in which the hydroxyapatite coating layer was introduced on the surface compared to the negative control zirconia itself, and the shape of the attached cells also extended and strongly adhered. In addition, in order to confirm the effect of the hydroxyapatite coating on cell proliferation, as described above, osteoblasts were dispensed on a zirconia implant with or without a hydroxyapatite coating layer and cultured for up to 5 days, while on the 3rd and 5th days. MTS assay was performed, and the results are shown in FIG. 8. As shown in FIG. 8, as the culture period increased, the cell proliferation rate was significantly increased in the zirconia implant including the hydroxyapatite coating layer. This indicates that the introduction of the hydroxyapatite coating layer enhances the adhesion and/or proliferation of osteoblasts on the implant, and thus, can be usefully used for tissue regeneration.

Experimental Example 4: Transplantation experiment to an animal model

In order to confirm the bone compatibility in vivo of the zirconia implant prepared with the hydroxyapatite coating layer prepared according to Example 1 above, an implantation experiment was performed in an animal model. Specifically, the implant was inserted into the shin bone of a 16-week-old rabbit and killed by asphyxiation using carbon dioxide after 4 weeks orally, and the shape of the implanted implant was observed through histological analysis, and the results are shown in FIG. 9. Further, the bone contact rate with the implant was calculated as the bone contact length compared to the length of the implant, and the bone area rate was calculated as the bone area relative to the area between the high portions of the implant, and the results are shown in FIG. 10. The histological analysis results shown in FIG. 9 show that in the case of the non-surface-treated zirconia specimen, bone cells were not filled much around the implant, whereas in the case of the zirconia specimen on which the hydroxyapatite coating layer was formed, the bone cells were filled around the implant. Indicate that you have lost. This was numerically calculated to calculate the contact degree and the bone area between the bone and the implant, and are shown in FIG. As shown in FIG. 10, when the hydroxyapatite coating layer was present, contact with the bone was significantly improved, and specifically, the values were increased by 40% and 25%, respectively, compared to the negative control group. This indicates that, as confirmed in Experimental Example 3, bone production was promoted due to the increased adhesion and/or proliferative power of cells by the hydroxyapatite coating layer.

Claims (15)

1. A first step of preparing a hydroxyapatite sol by mixing a triethylphosphite solution and a calcium nitrate tetrahydrate solution;

   A second step of dip coating the hydroxyapatite sole to form a hydroxyapatite sol coating layer on all or part of the surface of the zirconia implant; And

   Including a third step of sintering at 650 to 950 ℃,

   Method for producing a hydroxyapatite coated zirconia implant.
2. The method of claim 1,

   That the calcium zirconate is not produced, the manufacturing method.
3. The method of claim 1,

   The triethyl phosphite solution is used at a concentration of 0.1 to 1 M based on the mixed solution with the calcium nitrate tetrahydrate solution, and the calcium nitrate tetrahydrate is used at a molar concentration of 1.5 to 1.8 times that of the triethyl phosphite. Way.
4. The method of claim 1,

   The first step is achieved by mixing the triethyl phosphite solution and the calcium nitrate tetrahydrate solution at room temperature for 1 to 5 days, and optionally aging at 25 to 50° C. for 6 hours to 7 days, Manufacturing method.
5. The method of claim 1,

   The dip coating is to be performed at a rate of 0.1 to 10 mm per minute.
6. The method of claim 1,

   The dip coating is performed by repeating 2 to 9 times, the manufacturing method.
7. The method of claim 6,

   The method further comprising spinning for 10 to 30 seconds at 100 to 300 rpm after repeating every 2 to 4 times.
8. The method of claim 1,

   After the second step, the manufacturing method further comprises a step of drying at 60 to 90 ℃.
9. An implant having improved bone compatibility, comprising a hydroxyapatite coating layer formed to a thickness of 100 to 1000 nm on all or part of the surface of the zirconia implant.
10. The method of claim 9,

    Any one of claims 1 to 8, which is manufactured by the method of claim 1, an implant.
11. The method of claim 9,

    What is a dental implant, an implant.
12. The method of claim 11,

    A coating layer is formed on the screw (screw) portion, the implant.
13. The method of claim 9,

    Compared to the zirconium implant itself, bone regeneration is improved, the implant.
14. The method of claim 9,

    An implant that does not include an intermediate layer of fluorinated hydroxyapatite between the zirconium implant surface and the hydroxyapatite coating layer.
15. The method of claim 9,

    An implant that does not contain calcium zirconate, a by-product produced by the reaction of zirconium and hydroxyapatite.

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