Preparation method and application of dendrimer surface functionalized nanohydroxyapatite

Abstract

The present invention provides a preparation method and application of dendrimer surface functionalized nanohydroxyapatite, comprising the following steps: S1. mixing diammonium hydrogen phosphate solution with hexadecyltrimethylammonium bromide powder to obtain a modified diammonium hydrogen phosphate solution; S2. adding the modified diammonium hydrogen phosphate solution dropwise to a calcium nitrate solution, adding ammonia water, and obtaining a colloidal suspension with a white precipitate; S3. reacting the colloidal suspension at 160 to 190° C. to obtain nanohydroxyapatite; S4. dissolving an amino-terminated polyamide-amine dendrimer in water, and then gradually adding nanohydroxyapatite to the amino-terminated polyamide-amine dendrimer solution to obtain dendrimer surface functionalized nanohydroxyapatite. The dendrimer surface functionalized nanohydroxyapatite prepared by the present invention can be stabilized on the surface of collagen fibers exposed inside the dentinal tubules, thereby sealing the exposed dentinal tubules.

Description

Technical Field

[0001] The present invention relates to the technical field of oral medical materials, in particular to a preparation method and application of dendrimer surface functionalized nano-hydroxyapatite. Background Art

[0002] Dentin hypersensitivity is defined as a brief, sharp pain caused by exposure to cold, heat, mechanical, or chemical stimulation of the exposed dentin. Dentin hypersensitivity cannot be simply attributed to tooth defects or pathological conditions. Many factors can cause dentin hypersensitivity, including erosion, wear or abrasion, and gum recession and periodontal treatment. Although many hypotheses have been proposed regarding the mechanisms of dentin hypersensitivity in the last century, the fluid dynamics theory, proposed in 1960, remains the most widely accepted theory. and Astrom were the first to propose the fluid dynamics theory. They believed that the presence of a watery organic matrix within the dentinal tubules makes it more susceptible to stimulation when the dentin is exposed, causing a violent flow of fluid within the dentinal tubules. This stimulation is then slowly transferred to the dentinal cells within the dentinal tubules. The deep layers of the dentinal tubules are intertwined with nerves, and under the stimulation of pressure, they are converted into a sense of pain. Literature reports that teeth with dentine hypersensitivity have approximately eight times the number of exposed dentinal tubules as normal teeth, and have a larger diameter. Therefore, the ideal dentin desensitizing material should have the following characteristics: rapid onset, long duration of action, no damage to the dental pulp, no pain, simple application, and, for aesthetic reasons, should not cause tooth discoloration.

[0003] In recent years, polymer / hydroxyapatite nanocomposite biomaterials have become a hot topic in biomimetic restorative materials, as they combine the advantages of both organic and inorganic materials. In oral applications, many anti-sensitivity toothpastes currently incorporate nanohydroxyapatite (approximately 20-100 nanometers in diameter) and carboxyl-rich polymers, demonstrating promising short-term and long-term desensitization effects. Therefore, it is crucial to identify an organic material that can mimic the functions of non-collagenous proteins and combine it with an inorganic material, thereby achieving both occlusion of the dentinal tubules through the inorganic material and specific binding to the dentinal tubules for optimal long-term desensitization. Summary of the Invention

[0004] The present invention provides a preparation method and application of dendritic polymer surface-functionalized nanohydroxyapatite, which achieves surface functionalization by combining polyamide-amine with amino groups at the end with nanohydroxyapatite. Experimental verification shows that the surface-functionalized nanohydroxyapatite can be stabilized on the surface of collagen fibers exposed inside dentinal tubules, thereby sealing the exposed dentinal tubules.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A method for preparing dendrimer surface-functionalized nano-hydroxyapatite, characterized by comprising the following steps:

[0007] S1. The diamine phosphate solution was mixed with hexadecyltrimethylammonium bromide powder, the molar ratio of diamine phosphate to hexadecyltrimethylammonium bromide being 1 to 2:1, and stirred for 2 to 4 hours to obtain a modified diamine phosphate solution;

[0008] S2. The modified diamine hydrogen phosphate solution was added dropwise to the calcium nitrate solution; and aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate;

[0009] S3. The colloidal suspension with a white precipitate is transferred to a hydrothermal reactor and reacted at 160-190°C for 13-17 hours. After the reaction is complete, the precipitate is separated and washed with water and ethanol, followed by drying and grinding to remove hexadecyltrimethylammonium bromide to obtain nanohydroxyapatite.

[0010] S4. Completely dissolving the amino-terminated polyamide-amine dendrimer in water, gradually adding the nanohydroxyapatite to the stirred amino-terminated polyamide-amine dendrimer solution, wherein the mass ratio of the amino-terminated polyamide-amine dendrimer to the nanohydroxyapatite is 1:5-10, stirring for 8-16 hours, ultrasonically oscillating for 20-50 minutes, and finally filtering and separating the precipitate, washing, and drying to obtain dendrimer surface-functionalized nanohydroxyapatite.

[0011] Preferably, the molar ratio of the diammonium hydrogen phosphate solution to the calcium nitrate solution is 1:1 to 1.5, and the molar concentration ratio is 1:1 to 1.5.

[0012] Preferably, the molar ratio of diammonium hydrogen phosphate to hexadecyltrimethylammonium bromide is 1:1.

[0013] Preferably, in step S3, the specific step of drying the precipitate is: drying the precipitate in an oven at 80-95°C.

[0014] Preferably, in step S3, the specific step of removing cetyltrimethylammonium bromide is: calcining the ground precipitate at 500-620° C. for 5-8 hours.

[0015] Preferably, in step S4, the mass ratio of the amino-terminated polyamidoamine dendrimer to the nano-hydroxyapatite is 1:6.

[0016] Preferably, in step S4, the amino-terminated polyamidoamine dendrimer is dissolved in triple-distilled water at a concentration of 0.06 to 0.1 g / L.

[0017] Preferably, in step S4, the specific step of washing the precipitate is: washing with double-distilled water at least three times to remove free amino-terminated polyamidoamine dendrimers.

[0018] Preferably, in step S4, the specific step of drying the precipitate is: drying the precipitate in a vacuum drying oven at 45-55°C.

[0019] The present invention also provides the use of the dendritic polymer surface functionalized nano-hydroxyapatite prepared by the above preparation method in the preparation of dentinal tubule sealing materials.

[0020] The invention adds hexadecyltrimethylammonium bromide as a template when synthesizing hydroxyapatite, and makes a synthetic reaction between diammonium hydrogen phosphate and calcium nitrate to finally obtain mesoporous hydroxyapatite with a high specific surface area and a large pore volume.

[0021] The present invention further uses "water chemical reaction" to graft amino-terminated polyamide-amine dendrimers onto the surface of nanohydroxyapatite to form a dendrimer surface functionalized nanohydroxyapatite (G5-NH2 / n-HAP) nanocomposite biomaterial. The principle is: the surface of HAP has regularly distributed charge-rich areas - relatively wide positive charge areas (Ca 2+ enriched area) and a narrower negatively charged area (PO4 3- ), PAMAM-NH2, with amino groups as surface functional groups, can regularly bind to the surface of n-HAP via its positively charged amino chains, thereby synthesizing the G5-NH2 / n-HAP nanocomposite biomaterial. The high surface area and large pore volume of n-HAP facilitate its binding to a wider range of polyamidoamine dendrimer materials. The functional medium (G5-NH2) with a PAMAM / n-HAP surface can stabilize and adhere to collagen fibrils within demineralized dentinal tubules via size exclusion. In summary, G5-NH2 / n-HAP can regularly bind and adhere to the exposed collagen fibrils within dentinal tubules via its surface amino groups, thereby sealing the exposed dentinal tubules. This property of sealing exposed dentinal tubules can be used for the prevention and treatment of caries, biomimetic remineralization of dentine hard tissue, and clinical treatment of dentine hypersensitivity, making it a novel bioactive nanomaterial.

[0022] The present invention further validates the ability of G5-NH2 / n-HAP to seal demineralized dentinal tubules. Human dentin slices were partially demineralized to simulate a clinical dentin hypersensitivity model, and a biomimetic restoration experiment using G5-NH2 / n-HAP was conducted on dentinal tubules. Under a transmission electron microscope, the surface of the G5-NH2 / n-HAP nanocomposite biomaterial was observed to be uniformly encapsulated with a low-contrast organic molecule layer (G5-NH2), surrounding the nanohydroxyapatite. This demonstrates the successful functionalization of the n-HAP surface with G5-NH2. Scanning electron microscopy results show that after treatment with the G5-NH2 / n-HAP nanocomposite biomaterial and 7 days of remineralization, the demineralized dentinal tubules showed significant narrowing, and mineralized deposits were visible filling the tubules. Furthermore, due to the deposition of mineralized deposits within the tubules, the boundaries of the dentinal tubules were blurred. This demonstrates that the addition of amino-terminated polyamidoamine dendrimers to the surface of nanohydroxyapatite significantly enhances its bioactivity, thereby stably sealing open dentinal tubules. In summary, the dendrimer-surface-functionalized nanohydroxyapatite prepared by this invention exhibits excellent dentinal tubule sealing properties, providing more options for the clinical application of desensitizing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A This is a transmission electron microscopy image of nanohydroxyapatite before it is functionalized with PAMAM.

[0024] Figure 1B This is a transmission electron microscope image of nanohydroxyapatite after being functionalized with PAMAM.

[0025] Figure 2 A is an electron microscope scanning image of the dentinal tubules before being treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 (scale 50.0 μm). Figure 2 B is an electron microscope scanning image of dentinal tubules treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 and remineralized for 7 days (scale 50.0 μm). Figure 2 C is an electron microscope scanning image of the dentinal tubules before being treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 (scale 2.00 μm), Figure 2 D is an electron microscopy image of dentinal tubules treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 and remineralized for 7 days (scale bar 2.00 μm).

[0026] Figure 3 A1 is a scanning electron micrograph (500x magnification) of the surface morphology of dentinal tubules after the dentinal tubules were sealed and remineralized by G5-NH2 / n-HAP in Example 1 and then subjected to an acid etching test. Figure 3 A2 is a scanning electron micrograph of the surface morphology of dentinal tubules after the dentinal tubules were sealed and remineralized by G5-NH2 / n-HAP in Example 1 and then subjected to an acid etching test (magnification 1000 times). Figure 3 A3 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-NH2 / n-HAP and then subjected to acid etching test (magnification 2000 times). Figure 3 B1 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-COOH / n-HAP and then subjected to acid etching test (magnification 500 times). Figure 3 B2 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-COOH / n-HAP and then subjected to acid etching test (magnification 1000 times). Figure 3 B3 is a scanning electron micrograph (2000x magnification) of the surface morphology of dentinal tubules after they were blocked and remineralized by G5-COOH / n-HAP and then subjected to an acid etching test. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific examples, but the protection scope of the present invention is not limited to the following examples.

[0028] Example 1

[0029] S1. A 0.5M solution of diamine hydrogen phosphate was mixed with hexadecyltrimethylammonium bromide powder in a molar ratio of diamine hydrogen phosphate to hexadecyltrimethylammonium bromide of 1:1 and stirred for 2h to obtain a modified diamine hydrogen phosphate solution;

[0030] S2. The modified diamine phosphate solution was added dropwise to a 0.5 M calcium nitrate solution, the molar ratio of diamine phosphate to calcium nitrate being 1:1; and aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate;

[0031] S3. The colloidal suspension with a white precipitate was transferred to a hydrothermal reactor and reacted at 180°C for 15 hours. After completion of the reaction, the precipitate was separated by filtration, washed with water and then with ethanol, dried in an oven at 90°C for 10 hours, ground, and calcined at 600°C for 6 hours to remove hexadecyltrimethylammonium bromide, thereby obtaining nanohydroxyapatite.

[0032] S4. Completely dissolve 1 g of amino-terminated polyamide-amine dendrimer in 0.1 L of triple-distilled water, then gradually add 6 g of nanohydroxyapatite to the stirring amino-terminated polyamide-amine dendrimer solution, stir with a magnetic stirrer for 12 hours, then ultrasonically oscillate for 30 minutes, and finally filter and separate the precipitate. Wash with double-distilled water for at least three times to remove free amino-terminated polyamide-amine dendrimer, and dry in a vacuum drying oven at 50°C for 12 hours to obtain nanohydroxyapatite functionalized on the dendrimer surface.

[0033] Example 2

[0034] S1. A 0.4M solution of diamine hydrogen phosphate was mixed with hexadecyltrimethylammonium bromide powder in a molar ratio of diamine hydrogen phosphate to hexadecyltrimethylammonium bromide of 1.5:1, and stirred for 3h to obtain a modified diamine hydrogen phosphate solution;

[0035] S2. The modified diamine phosphate solution was added dropwise to a 0.4 M calcium nitrate solution, the molar ratio of diamine phosphate to calcium nitrate being 1:1.2; and aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate;

[0036] S3. The colloidal suspension with a white precipitate was transferred to a hydrothermal reactor and reacted at 190°C for 14 hours. After completion of the reaction, the precipitate was separated by filtration, washed with water and then ethanol, dried in an oven at 85°C for 12 hours, ground, and calcined at 580°C for 7 hours to remove hexadecyltrimethylammonium bromide, thereby obtaining nanohydroxyapatite.

[0037] S4. Completely dissolve 0.8 g of amino-terminated polyamide-amine dendrimer in 0.1 L of triple-distilled water, then gradually add 6 g of nanohydroxyapatite to the stirring amino-terminated polyamide-amine dendrimer solution, stir using a magnetic stirrer for 12 hours, then ultrasonically oscillate for 40 minutes, and finally filter and separate the precipitate. Wash with double-distilled water for at least three times to remove free amino-terminated polyamide-amine dendrimer, and dry in a vacuum drying oven at 50°C for 13 hours to obtain dendrimer surface-functionalized nanohydroxyapatite.

[0038] Example 3

[0039] S1. A 0.5M solution of diamine hydrogen phosphate was mixed with hexadecyltrimethylammonium bromide powder in a molar ratio of diamine hydrogen phosphate to hexadecyltrimethylammonium bromide of 2:1, and stirred for 3h to obtain a modified diamine hydrogen phosphate solution;

[0040] S2. The modified diamine phosphate solution was added dropwise to a 0.5 M calcium nitrate solution, the molar ratio of diamine phosphate to calcium nitrate being 1:1.5; and aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate;

[0041] S3. The colloidal suspension with a white precipitate was transferred to a hydrothermal reactor and reacted at 170°C for 17 hours. After completion of the reaction, the precipitate was separated by filtration, washed with water and then ethanol, dried in an oven at 95°C for 10 hours, ground, and calcined at 580°C for 6 hours to remove hexadecyltrimethylammonium bromide, thereby obtaining nanohydroxyapatite.

[0042] S4. Completely dissolve 0.6 g of amino-terminated polyamide-amine dendrimer in 0.1 L of triple-distilled water, then gradually add 6 g of nanohydroxyapatite to the stirring amino-terminated polyamide-amine dendrimer solution, stir with a magnetic stirrer for 13 hours, then ultrasonically oscillate for 20 minutes, and finally filter and separate the precipitate. Wash with double-distilled water for at least three times to remove free amino-terminated polyamide-amine dendrimer, and dry in a vacuum drying oven at 50°C for 13 hours to obtain dendrimer surface-functionalized nanohydroxyapatite.

[0043] Comparative Example 1

[0044] S1. A 0.5 M diammonium hydrogen phosphate solution was added dropwise to a 0.5 M calcium nitrate solution; aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate;

[0045] S2. The colloidal suspension with a white precipitate was transferred to a hydrothermal reactor and reacted at 180°C for 15 h. After completion of the reaction, the precipitate was separated by filtration, washed with water and then ethanol, dried in an oven at 90°C for 10 h, and ground to obtain nanohydroxyapatite.

[0046] S3. Completely dissolve 1 g of polyamide-amine dendrimer with carboxyl as surface functional groups in 0.1 L of triple-distilled water, then gradually add 6 g of nano-hydroxyapatite to the stirring polyamide-amine dendrimer solution with carboxyl as surface functional groups, stir with a magnetic stirrer for 12 hours, then ultrasonically oscillate for 30 minutes, and finally filter and separate the precipitate. Wash with double-distilled water for at least three times to remove free polyamide-amine dendrimer with carboxyl as surface functional groups, and place in a vacuum drying oven at 50°C for 12 hours to obtain dendrimer surface functionalized nano-hydroxyapatite.

[0047] Verification Example 1

[0048] This example further validates the ability of PAMAM / n-HAP to seal demineralized dentinal tubules. A partial demineralized human dentin slice was used to simulate a clinical dentin hypersensitivity model, and PAMAM / n-HAP was used to perform a biomimetic restoration experiment on dentinal tubules. The biomimetic restoration experiment was described in the paper "Synthesis, Characterization, and Sealing Effect of Polyamidoamine / Nanohydroxyapatite on Dentin Tubules," by Lin Xuandong et al., Journal of the Chinese Academy of Medical Sciences, 2017, 39(2), 163-168.

[0049] Figure 1A This is a transmission electron microscope image of nanohydroxyapatite before it is functionalized with PAMAM. Figure 1B This is a transmission electron microscope image of nanohydroxyapatite after being functionalized with PAMAM (dendrimer surface functionalized nanohydroxyapatite prepared in Example 1). Figure 1A and Figure 1B It can be seen from the comparison that under the transmission electron microscope, the surface of the PAMAM / n-HAP nanocomposite biomaterial can be observed to be uniformly wrapped with a low-contrast organic molecular layer (G5-NH2) of nanohydroxyapatite in the shape of a capsule, proving the successful functionalization of the surface G5-NH2 on the n-HAP surface. Figure 2 A is an electron microscope scanning image of the dentinal tubules before being treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 (scale 50.0 μm). Figure 2 B is an electron microscope scanning image of dentinal tubules treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 and remineralized for 7 days (scale 50.0 μm). Figure 2 C is an electron microscope scanning image of the dentinal tubules before being treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 (scale 2.00 μm), Figure 2 D is an electron microscope scanning image of the dentinal tubules treated with the G5-NH2 / n-HAP nanocomposite biomaterial of Example 1 and after 7 days of remineralization (scale 2.00 μm); Figure 2 Comparison of AD images shows that after treatment with the G5-NH2 / n-HAP nanocomposite biomaterial and 7 days of remineralization, the demineralized dentinal tubules were significantly narrowed, and the tubules were filled with mineralized deposits. The deposition of mineralized deposits within the tubules also blurred the boundaries of the dentinal tubules. This demonstrates that the addition of amino-terminated polyamidoamine dendrimers to the surface of nanohydroxyapatite significantly enhances its bioactivity, thereby stably sealing open dentinal tubules.

[0050] This example further validates the anti-etching effect of PAMAM / n-HAP on demineralized dentinal tubules. Human dentin slices were partially demineralized to simulate a clinical dentin hypersensitivity model. Dentin tubules were then sealed and remineralized using G5-NH2 / n-HAP (prepared in Example 1) and G5-COOH / n-HAP (prepared in Comparative Example 1) (referring to the method of Verification Example 1). The mineralized dentin slices were then subjected to an acid etching experiment using a carbonate solution: 25 μL of carbonate solution was dripped onto the surface of the dentin slices. The slices were then smeared with a disposable dental brush for 5 minutes each, once daily, for 2 consecutive weeks. Postoperatively, the surface morphology of the dentinal tubules was observed using a scanning electron microscope at magnifications of 500, 1000, and 5000. Figure 3 A1 is a scanning electron micrograph (500x magnification) of the surface morphology of dentinal tubules after the dentinal tubules were sealed and remineralized by G5-NH2 / n-HAP in Example 1 and then subjected to an acid etching test. Figure 3 A2 is a scanning electron micrograph of the surface morphology of dentinal tubules after the dentinal tubules were sealed and remineralized by G5-NH2 / n-HAP in Example 1 and then subjected to an acid etching test (magnification 1000 times). Figure 3 A3 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-NH2 / n-HAP and then subjected to acid etching test (magnification 2000 times). Figure 3 B1 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-COOH / n-HAP and then subjected to acid etching test (magnification 500 times). Figure 3 B2 is a scanning electron micrograph of the surface morphology of dentinal tubules after they were sealed and remineralized by G5-COOH / n-HAP and then subjected to acid etching test (magnification 1000 times). Figure 3 B3 is a scanning electron micrograph (SEM) of the surface morphology of dentinal tubules after dentinal tubules were sealed and remineralized with G5-COOH / n-HAP and then subjected to acid etching (2000x magnification). Comparison shows that, after two weeks of acid etching, although some dentinal tubules were exposed in the dentin sections repaired with the G5-NH2 / n-HAP nanocomposite biomaterial, the mineralized deposits within the tubules were still largely enclosed (A1-A3). After two weeks of acid etching, nearly all dentinal tubules in the dentin sections repaired with the G5-COOH / n-HAP nanocomposite biomaterial were completely open, with enlarged tubule openings, smooth and rounded borders, and a clean and smooth surface (B1-B3). These results demonstrate that the addition of polyamidoamine dendrimers (G5-NH2) to the surface of nanohydroxyapatite not only enables biomimetic repair and sealing of dentinal tubules but also exhibits superior acid-etch resistance compared to G5-COOH, thus promising promising clinical applications.

Claims

1. A method for preparing dendrimer surface functionalized nano-hydroxyapatite, characterized in that The following steps are involved: S1. The diamine phosphate solution was mixed with hexadecyltrimethylammonium bromide powder, the molar ratio of diamine phosphate to hexadecyltrimethylammonium bromide was 1:1, and stirred for 2 to 4 hours to obtain a modified diamine phosphate solution; S2. The modified diamine phosphate solution was added dropwise to the calcium nitrate solution, the molar ratio of diamine phosphate to calcium nitrate was 1:1, and the molar concentration ratio was 1:1; and aqueous ammonia was added to maintain the pH of the reaction mixture between 11 and 12 to obtain a colloidal suspension with a white precipitate; S3. The colloidal suspension containing a white precipitate is transferred to a hydrothermal reactor and reacted at 160-190°C for 13-17 hours. After completion of the reaction, the precipitate is separated and washed with water and then ethanol, followed by drying and grinding to remove the hexadecyltrimethylammonium bromide to obtain nanohydroxyapatite. S4. Completely dissolving the amino-terminated polyamide-amine dendrimer in water, gradually adding the nanohydroxyapatite to the stirred amino-terminated polyamide-amine dendrimer solution, wherein the mass ratio of the amino-terminated polyamide-amine dendrimer to the nanohydroxyapatite is 1:5-10, stirring for 8-16 hours, ultrasonically oscillating for 20-50 minutes, and finally filtering and separating the precipitate, washing, and drying to obtain dendrimer surface-functionalized nanohydroxyapatite; In step S3, the specific step of removing cetyltrimethylammonium bromide is: calcining the ground precipitate at 500-620° C. for 5-8 hours.

2. The method for preparing dendrimer surface-functionalized nano-hydroxyapatite according to claim 1, characterized in that: In step S3, the specific steps of drying the precipitate are: drying the precipitate in an oven at 80-95°C.

3. The method for preparing dendrimer surface-functionalized nano-hydroxyapatite according to claim 1, characterized in that: In step S4, the mass ratio of the amino-terminated polyamidoamine dendrimer to the nano-hydroxyapatite is 1:

6.

4. The method for preparing dendrimer surface-functionalized nano-hydroxyapatite according to claim 1, wherein: In step S4, amino-terminated polyamidoamine dendrimer is dissolved in triple-distilled water at a concentration of 0.06-0.1 g / L.

5. The method for preparing dendrimer surface-functionalized nano-hydroxyapatite according to claim 1, characterized in that: In step S4, the specific steps of washing the precipitate are: washing with double-distilled water for at least three times to remove free amino-terminated polyamidoamine dendrimers.

6. The method for preparing dendrimer surface-functionalized nano-hydroxyapatite according to claim 1, characterized in that: In step S4, the specific steps of drying the precipitate are: drying the precipitate in a vacuum drying oven at 45-55°C.

7. Use of dendrimer surface-functionalized nanohydroxyapatite prepared by the preparation method according to any one of claims 1 to 6 in the preparation of dentinal tubule sealing materials.

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