Oral cavity fixing nail and coating preparation method thereof

Abstract

The invention relates to the technical field of medical apparatus and instruments, and discloses an oral cavity fixing nail and a coating preparation method thereof, the method comprises the following steps: a base body is prepared, a magnesium alloy material is selected, the base body of the oral cavity fixing nail is formed through numerical control processing, and the fixing nail comprises a disc-shaped nail cap with the diameter of 2.5-4 mm and a nail body with the diameter of 1-1.5 mm; sand blasting treatment is conducted, specifically, the magnesium alloy base body is placed in sand blasting equipment, an abrasive material with the particle size being 0.5-2.5 mm is adopted, and surface treatment is conducted under the air pressure being 0.5-0.7 MPa; the polyorthoester coating shows hydrophobic characteristics in an oral cavity weak alkaline environment, a layer of compact physical barrier is formed, direct contact between body fluid and a magnesium alloy matrix is isolated, the degradation rate of a matrix material is slowed down, and it is guaranteed that the stable mechanical strength and the stable fixing effect of the fixing nail are maintained in the bone regeneration period. And a continuous and uniform film layer structure is formed, and micro defects on the surface of the magnesium alloy are filled, so that the service life of the fixing nail is prolonged, and a reliable time window is provided for bone tissue regeneration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, in particular to an oral fixation nail and a coating preparation method thereof. BACKGROUND

[0002] With the continuous progress of biomaterial research and the development of implantation repair surgery technology, guided bone regeneration technology has been widely used in implantation surgery area bone defect repair and immediate implantation. The basic principle of guided bone regeneration technology is to use guided tissue regeneration membrane as a physical barrier to protect the blood clot in the bone defect area, and allow osteogenic cells to migrate and grow preferentially, prevent the invasion of surrounding non-osteogenic connective tissue cells and epithelial cells into the defect area, avoid the generation of competitive inhibition, form a regeneration space conducive to the growth of osteogenic cells, promote the reconstruction of bone defect tissue, and increase the bone mass.

[0003] At present, due to the use of magnesium alloy matrix material in the manufacturing process of oral fixation nails, the fixation nail after implantation needs to maintain structural stability in the complex oral environment during bone regeneration repair surgery. When the degradation rate control of magnesium alloy fails, the mechanical properties of the fixation nail will decay prematurely, which cannot guarantee the fixation of the bone regeneration period.

[0004] Therefore, the present application provides an oral fixation nail and a coating preparation method thereof to solve the above problems. SUMMARY

[0005] The main purpose of the present application is to provide an oral fixation nail and a coating preparation method thereof to solve the problems raised in the above background.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: an oral fixation nail and a coating preparation method thereof, comprising the following steps: Step 1: matrix preparation, selecting magnesium alloy material, and forming an oral fixation nail matrix through numerical control machining, the fixation nail comprising a disc-shaped nail cap with a diameter of 2.5-4mm and a nail body with a diameter of 1-1.5mm; Step 2: sandblasting treatment, placing the magnesium alloy matrix in a sandblasting equipment, and using abrasive with a particle size of 0.5-2.5mm to perform surface treatment under an air pressure of 0.5-0.7MPa; Step 3: polyorthoester synthesis, under nitrogen protection environment, 1,1,4-cyclohexane trimethyl alcohol and triethyl orthoacetate are added to the reaction kettle in a molar ratio of 2-4:1 and anhydrous acidic catalyst, and stirred at 70-80℃ for 18-20 hours, and then subjected to neutralization with alkaline solution, dissolution with chloroform, water washing and purification, and methanol precipitation to obtain polyorthoester with a molecular weight of 50-200 thousand; Step four: coating spraying, polyol dissolves in chloroform to form 0.5-1g / 100ml solution, 30-70 cycles of spraying are carried out on the surface of magnesium alloy substrate by spraying equipment to form a uniform coating with a thickness of 5-20μm.

[0007] Preferably, in step two, In the sand blasting process, the abrasive is selected from alumina or silicon carbide, the abrasive particle size is selected in the range of 0.5-2.5mm, and the air pressure is controlled in the range of 0.5-0.7MPa. The surface roughness of the magnesium alloy substrate after sand blasting is controlled in the range of 1.2-3.6μm. The synergistic control of abrasive particle size and air pressure needs to meet one of the following technical solutions: I. When fine abrasive is used, abrasive particles with a particle size of 0.5-1.5mm are selected, and the corresponding air pressure is adjusted to 0.5-0.6MPa, at which time a micro-rough structure with a surface roughness of 1.8-2.1μm is formed. II. When coarse abrasive is used, abrasive particles with a particle size of 1.5-2.5mm are selected, and the corresponding air pressure is adjusted to 0.6-0.7MPa, at which time a macro-rough structure with a surface roughness of 2.1-2.5μm is formed. The roughness control accuracy needs to be ensured within an error range of ±0.2μm.

[0008] Preferably, the surface roughness technical solution is 1.5-3.0μm. The cleaning process after sand blasting specifically includes: completely immersing the substrate in anhydrous ethanol solution of analytical purity, and treating it with an ultrasonic cleaning instrument with a frequency of 40kHz for 9.5-10.5 minutes. The drying process is carried out in a blast drying oven, with a set temperature of 48-52℃ and a continuous drying time of 58-62 minutes. After drying, the substrate needs to be cooled to room temperature in a drying dish before subsequent processing.

[0009] Preferably, in step three, In the polyol synthesis reaction, the molar ratio technical solution of 1,1,4-cyclohexane tri-methanol to triethyl orthoacetate is 3-4:1. The catalyst uses phosphotungstic acid solid powder, and the addition amount is 0.5-1.0% of the weight of the monomer. The reaction system needs to be continuously purged with high-purity nitrogen with a purity of ≥99.999%; The neutralization process after the reaction is terminated is specifically: adding ammonia solution with a concentration of 10% drop by drop until the pH value of the reaction solution reaches 6.5-7.5; the molecular weight of the polyol is 10-20 million, and the molecular weight is tested by gel permeation chromatography GPC.

[0010] Preferably, the polyoxymethylene molecular weight control has a direct correspondence with the monomer molar ratio: When the molar ratio is controlled in the range of 2-3:1, the molecular weight of the resulting polymer ranges from 5-15 million; When the molar ratio is controlled in the range of 3-4:1, the molecular weight of the resulting polymer ranges from 15-20 million; The dispersion coefficient of the molecular weight distribution needs to be controlled below 1.5; During the polymer precipitation process, the volume ratio of methanol to chloroform solution is 5:1; The resulting solid is filtered and dried in a blast drying oven at 40°C for 12 hours.

[0011] Preferably, in step four: In the coating spraying process, the solution concentration is controlled between 0.5-1.0 g / 100 ml, the spraying equipment uses a high-pressure airless sprayer, the nozzle diameter is 0.3-0.5 mm, and the spraying process parameters need to meet one of the following technical solutions: Ⅰ, when the solution concentration is 0.5-0.75 g / 100 ml, the spraying cycle number is controlled in the range of 50-70 times; Ⅱ, when the solution concentration is 0.75-1.0 g / 100 ml, the spraying cycle number is controlled in the range of 30-50 times; The single spraying thickness increment is controlled in the range of 0.15-0.3 μm / time, and the interval time between each layer spraying is ≥3 minutes.

[0012] Preferably, the accurate control of the coating thickness needs to meet the following mapping relationship: Thickness 12-15 μm corresponds to the technical solution: solution concentration 0.75-1.0 g / 100 ml and spraying number 30-40 times; Thickness 15-20 μm corresponds to the technical solution: solution concentration 0.5-0.75 g / 100 ml and spraying number 50-70 times; Coating uniformity requirement: thickness difference of any three points ≤±1.5 μm; Spraying environment requirement: temperature 25±5°C, relative humidity ≤40% RH.

[0013] Preferably, the magnesium alloy base material is selected from degradable magnesium alloys, wherein the content of magnesium element is ≥90 wt%; The alloying elements include but are not limited to at least one of Fe, Ca, Ni, Mn, Sr, Cu, Zn, and Zr; The technical solution uses Mg-Zn alloy, and the content of zinc element is controlled in the range of 0.5-2.0 wt%; The base mechanical property requirement: tensile strength ≥200 MPa, elongation ≥10%.

[0014] Preferably, the oral fixation nail comprises a magnesium alloy base and a polyoxymethylene coating covering the surface of the base: The surface roughness of the base is controlled in the range of 1.5-3.0 μm; The thickness of the coating is 10-20 μm, and the molecular weight is 100-200 thousand; The interfacial bonding strength of the coating and the base is ≥60 N; The microstructure of the coating is a continuous and dense film layer without visible cracks and hole defects; The overall degradation period of the fixation nail is 6-12 months.

[0015] Preferably, the coating exhibits hydrophobic properties in the alkaline implant environment with pH 7.4-8.0, and the static water contact angle is ≥90°; The degradation rate control index: when immersed in simulated body fluid SBF at 37℃, the degradation rate is ≤0.05 mm / year; The magnesium ion release control index: the release rate is ≤0.2 mg / cm 2 ·day; Flame retardant performance requirement: oxygen index ≥30%; Mechanical performance requirement: bending strength ≥120 MPa, shear strength ≥40 MPa; Biocompatibility requirement: cytotoxicity grade 0, and bone bonding rate ≥80%.

[0016] The present application has the following beneficial effects: 1. In the present application, the polyoxymethylene coating exhibits hydrophobic properties in the weak alkaline environment of the oral cavity, forming a dense physical barrier to isolate the body fluid from direct contact with the magnesium alloy base, slowing down the degradation rate of the base material, and ensuring that the fixation nail maintains stable mechanical strength and fixation effect during the bone regeneration period; through careful design of the molecular chain, the coating forms a continuous and uniform film layer structure, filling the micro defects on the surface of the magnesium alloy, avoiding premature failure caused by local stress concentration during degradation, thereby prolonging the service life of the fixation nail and providing a reliable time window for bone tissue regeneration.

[0017] 2. In the present application, the sandblasting process creates a micro-rough structure on the surface of the magnesium alloy base, enhancing the interfacial bonding force of the coating and the base; by controlling the synergistic effect of abrasive particle size and air pressure, the surface roughness is optimized, so that the polyoxymethylene coating can penetrate into the base micropores and form mechanical interlocking, preventing the coating from peeling or falling off during implantation operation or body fluid erosion; in addition, this treatment also improves the active site density on the surface of the base, promotes the chemical bonding of the coating material at the interface, and builds a firm and durable composite system, ensuring that the fixation nail always maintains integrity and functionality in the dynamic oral environment.

[0018] 3. In the present application, the degradation regulation mechanism of the polyolide coating cooperates with the magnesium alloy substrate to comprehensively optimize the biocompatibility; the slow degradation process of the coating releases a controllable magnesium ion concentration, avoiding the cytotoxicity reaction caused by excessive ion levels, and at the same time regulating the proliferation and differentiation of bone cells through ion gradient, promoting bone tissue regeneration and healing; in addition, the synergistic degradation characteristics of the coating and the substrate also form a time-matched release curve, ensuring the stable ion supply and mechanical support in the key stage of bone regeneration, thereby comprehensively improving the clinical safety and treatment effect of the fixation nail. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the scanning electron microscope image of the polyolide coating in Example 1. Figure 2 It is the scanning electron microscope image of the polyolide coating in Example 2. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0021] Please refer to Figures 1-2 , the oral fixation nail and the coating preparation method thereof; Embodiment I: an oral fixation nail and a coating preparation method thereof, comprising the following steps: Step one: substrate preparation, selecting a magnesium alloy material, and processing it into an oral fixation nail substrate through numerical control machining; the fixation nail comprises a disc-shaped nail cap with a diameter of 2.5 mm and a nail body with a diameter of 1 mm; Step two: sandblasting treatment, placing the magnesium alloy substrate in a sandblasting device, and performing surface treatment under 0.5 MPa air pressure by using abrasive particles with a particle size of 0.5 mm; Step three: polyolide synthesis, under a nitrogen protection environment, adding 1,1,4-cyclohexane trimethyl alcohol, triethyl orthoacetate and anhydrous acidic catalyst into a reaction kettle according to a molar ratio of 2:1, stirring and reacting at 70°C for 18 hours, and then obtaining polyolide with a molecular weight of 50,000 through neutralization with an alkaline solution, chloroform dissolution, water washing purification and methanol precipitation; Step four: coating spraying, dissolving the polyolide in chloroform to form a 0.5 g / 100 ml solution, and performing 30 cycles of spraying on the surface of the magnesium alloy substrate through a spraying device to form a uniform coating with a thickness of 5 μm.

[0022] In step two: In the sand blasting process, the abrasive is selected from alumina or silicon carbide, the abrasive particle size is 0.5 mm, and the air pressure is 0.5 MPa; the surface roughness of the magnesium alloy substrate after sand blasting treatment is controlled to be 1.2 μm; The synergistic control of the abrasive particle size and the air pressure needs to meet one of the following technical solutions: I. When fine-grained abrasive is used, abrasive particles with a particle size of 0.5 mm are selected, and the corresponding air pressure is adjusted to 0.5 MPa, at which time a micro-rough structure of 1.8 μm is formed on the surface; II. When coarse-grained abrasive is used, abrasive particles with a particle size of 1.5 mm are selected, and the corresponding air pressure is adjusted to 0.6 MPa, at which time a macro-rough structure of 2.1 μm is formed on the surface; The roughness control precision needs to be ensured within an error range of ±0.2 μm.

[0023] The technical solution for the surface roughness is 1.5 μm; The cleaning process after sand blasting treatment specifically includes: completely immersing the substrate in an analytical pure anhydrous ethanol solution, and treating it with an ultrasonic cleaning instrument with a frequency of 40 kHz for 9.5 minutes; The drying process is carried out in a blast drying oven, with a set temperature of 48℃ and a continuous drying time of 58 minutes; After drying, the substrate needs to be cooled to room temperature in a drying dish before subsequent processing.

[0024] In step three, In the polyorthoester synthesis reaction, the molar ratio technical solution of 1,1,4-cyclohexane tri-methanol to triethyl orthoacetate is 3:1; The catalyst uses phosphotungstic acid solid powder, and the addition amount is 0.5% of the weight of the monomer; The reaction system needs to be continuously purged with high-purity nitrogen with a purity of ≥99.999%; The neutralization process after the reaction is terminated is specifically: adding ammonia solution with a concentration of 10% drop by drop until the pH value of the reaction solution reaches 6.5; The technical solution of the polyorthoester molecular weight is 100,000, and the molecular weight is tested by gel permeation chromatography GPC.

[0025] The regulation of the polyorthoester molecular weight has a direct corresponding relationship with the molar ratio of the monomer: When the molar ratio is controlled at 2:1, the molecular weight of the obtained polymer is 50,000; When the molar ratio is controlled at 3:1, the molecular weight of the obtained polymer is 150,000; The dispersion coefficient of the molecular weight distribution needs to be controlled to be less than 1.5; During the polymer precipitation process, the volume ratio of methanol to chloroform solution is 5:1; The obtained solid was filtered and dried in a blast drying oven at 40℃ for 12 hours.

[0026] In step four: In the coating spraying process, the solution concentration is controlled at 0.5g / 100ml, the spraying equipment adopts a high-pressure airless sprayer, the nozzle diameter is 0.3mm, and the spraying process parameters need to meet one of the following technical solutions: I. When the solution concentration is 0.5g / 100ml, the spraying cycle number is controlled at 50 times; II. When the solution concentration is 0.75g / 100ml, the spraying cycle number is controlled at 30 times; The single spraying thickness increment is controlled at 0.15μm / time, and the interval time between each layer of spraying is ≥3 minutes.

[0027] The accurate control of the coating thickness needs to meet the following mapping relationship: The thickness of 12μm corresponds to the technical solution of solution concentration 0.75g / 100ml and spraying number 30 times; The thickness of 15μm corresponds to the technical solution of solution concentration 0.5g / 100ml and spraying number 50 times; The coating uniformity requirement is that the thickness difference of any three points is ≤±1.5μm; The spraying environment requirement is that the temperature is 25±5℃, and the relative humidity is ≤40%RH.

[0028] The magnesium alloy base material is selected from degradable magnesium alloys, wherein the content of magnesium element is ≥90wt%; The alloy elements include but are not limited to at least one of Fe, Ca, Ni, Mn, Sr, Cu, Zn, and Zr; The technical solution adopts Mg-Zn alloy, and the content of zinc element is controlled at 0.5wt%; The base mechanical performance requirement is that the tensile strength is ≥200MPa, and the elongation is ≥10%.

[0029] The oral fixation pin includes a magnesium alloy base and a polyorthoester coating covering the surface of the base: The surface roughness of the base is controlled at 1.5μm; The coating thickness is 10μm, and the molecular weight is 100,000; The interface bonding strength between the coating and the base is ≥60N; The microstructure of the coating is a continuous and dense film layer without visible cracks and hole defects; The overall degradation period of the fixation pin is 6 months.

[0030] The coating presents hydrophobic characteristics in the alkaline implantation environment with pH 7.4, and the static water contact angle is ≥90°; Degradation rate control index: degradation rate ≤ 0.05 mm / year when immersed in simulated body fluid SBF at 37℃; Magnesium ion release control index: release rate ≤ 0.2 mg / cm 2 ·day; Flame retardant performance requirement: oxygen index ≥ 30%; Mechanical performance requirement: bending strength ≥ 120 MPa, shear strength ≥ 40 MPa; Biocompatibility requirement: cytotoxicity grade 0, bone bonding rate ≥ 80%.

[0031] Implementation II: An oral fixation pin and a coating preparation method thereof, comprising the following steps: Step 1: Preparation of the substrate, select magnesium alloy material, and process it into an oral fixation pin substrate by numerical control machining. The fixation pin includes a disc-shaped pin cap with a diameter of 3 mm and a pin body with a diameter of 1.8 mm. Step 2: Sandblasting treatment, place the magnesium alloy substrate in a sandblasting equipment, and use abrasive with a particle size of 1.5 mm to perform surface treatment under an air pressure of 0.6 MPa. Step 3: Polyorthoester synthesis, under nitrogen protection, add 1,1,4-cyclohexane tri-methanol, triethyl orthoacetate, and anhydrous acidic catalyst into a reaction kettle in a molar ratio of 3:1, stir at 75℃ for 19 hours, and then perform neutralization with an alkaline solution, dissolution in chloroform, water washing and purification, and methanol precipitation to obtain polyorthoester with a molecular weight of 100,000. Step 4: Coating spraying, dissolve the polyorthoester in chloroform to form a 0.8 g / 100 ml solution, and perform 50 cycles of spraying on the surface of the magnesium alloy substrate through a spraying equipment to form a uniform coating with a thickness of 15 μm.

[0032] In step 2: During the sandblasting process, the abrasive is made of alumina or silicon carbide, the abrasive particle size is 1.5 mm, and the air pressure is 0.6 MPa. The surface roughness of the magnesium alloy substrate after sandblasting treatment is 2.4 μm. The cooperative control of abrasive particle size and air pressure needs to meet one of the following technical solutions: I. When fine-grained abrasive is used, abrasive particles with a particle size of 1.0 mm are selected, and the corresponding air pressure is adjusted to 0.55 MPa. At this time, a micro-rough structure with a surface roughness of 2.0 μm is formed. II. When coarse-grained abrasive is used, abrasive particles with a particle size of 2.0 mm are selected, and the corresponding air pressure is adjusted to 0.65 MPa. At this time, a macro-rough structure with a surface roughness of 2.3 μm is formed. The roughness control accuracy needs to be ensured within an error range of ± 0.2 μm.

[0033] The technical solution of the surface roughness is 2.0 μm. The cleaning process after sand blasting treatment specifically includes: completely immersing the substrate in an analytical pure grade anhydrous ethanol solution, and treating for 10 minutes using an ultrasonic cleaning instrument with a frequency of 40 kHz; The drying process is performed in a blast drying oven, with a set temperature of 50℃, and a continuous drying time of 60 minutes; After drying, the substrate needs to be cooled to room temperature in a drying dish before subsequent processing.

[0034] In step three, In the polyurethane synthesis reaction, the technical solution of the molar ratio of 1,1,4-cyclohexane tri-methanol to triethyl orthoacetate is 3.5:1; The catalyst uses phosphotungstic acid solid powder, and the addition amount is 0.8% of the weight of the monomer; The reaction system needs to be continuously purged with high-purity nitrogen with a purity of ≥99.999%; The neutralization process after the reaction is terminated is specifically: adding 10% ammonia solution drop by drop until the pH value of the reaction solution reaches 7.0; The technical solution of the molecular weight of polyurethane is 150,000, and the molecular weight is tested by gel permeation chromatography GPC.

[0035] The control of the molecular weight of polyurethane has a direct correspondence with the molar ratio of the monomer: When the molar ratio is controlled at 2.5:1, the molecular weight of the obtained polymer is 100,000; When the molar ratio is controlled at 3.5:1, the molecular weight of the obtained polymer is 170,000; The dispersion coefficient of the molecular weight distribution needs to be controlled below 1.5; During the polymer precipitation process, the volume ratio of methanol to chloroform solution is 5:1; The obtained solid is dried in a blast drying oven at 40℃ for 12 hours.

[0036] In step four, In the coating spraying process, the solution concentration is controlled at 0.8g / 100ml, the spraying equipment uses a high-pressure airless sprayer, the nozzle diameter is 0.4mm, and the spraying process parameters need to meet one of the following technical solutions: Ⅰ, when the solution concentration is 0.6g / 100ml, the spraying cycle number is controlled at 60 times; Ⅱ, when the solution concentration is 0.9g / 100ml, the spraying cycle number is controlled at 40 times; The single spraying thickness increment is controlled at 0.20μm / time, and the interval time between each layer of spraying is ≥3 minutes.

[0037] The accurate control of the coating thickness needs to meet the following mapping relationship: Thickness 13 μm corresponding technical solution: solution concentration 0.8 g / 100 ml and spraying number 35 times; Thickness 17 μm corresponding technical solution: solution concentration 0.6 g / 100 ml and spraying number 60 times; Coating uniformity requirement: thickness difference of any three points ≤±1.5 μm; Spraying environment requirement: temperature 25±5℃, relative humidity ≤40% RH.

[0038] Magnesium alloy base material is selected to be degradable magnesium alloy, wherein the content of magnesium element is ≥90 wt%; Alloy elements include, but are not limited to, at least one of Fe, Ca, Ni, Mn, Sr, Cu, Zn, and Zr; The technical solution adopts Mg-Zn alloy, and the content of zinc element is controlled to be 1.0 wt%; Base mechanical property requirement: tensile strength ≥200 MPa, elongation ≥10%.

[0039] The oral fixation pin includes a magnesium alloy base and a polyorthoester coating covering the surface of the base: The surface roughness of the base is controlled to be 2.5 μm; The coating thickness is 15 μm, and the molecular weight is 150,000; The interface bonding strength of the coating and the base is ≥60 N; The microstructure of the coating is a continuous dense film layer without visible crack and hole defects; The overall degradation period of the fixation pin is 10 months.

[0040] The coating presents hydrophobic characteristics in an alkaline implantation environment with pH 7.8, and the static water contact angle is ≥90°; Degradation rate control index: when immersed in simulated body fluid SBF at 37℃, the degradation rate is ≤0.05 mm / year; Magnesium ion release control index: the release rate is ≤0.2 mg / cm 2 ·day after 12 weeks of immersion; Flame retardant performance requirement: oxygen index ≥30%; Mechanical property requirement: bending strength ≥120 MPa, shear strength ≥40 MPa; Biocompatibility requirement: cytotoxicity grade 0, and bone bonding rate ≥80%.

[0041] Implementation three: an oral fixation pin and a coating preparation method thereof, including the following steps: Step one: base preparation, selecting magnesium alloy material, and forming into an oral fixation pin base through numerical control machining, the fixation pin including a disc-shaped pin cap with a diameter of 4 mm and a pin body with a diameter of 1.5 mm; Step two: sand blasting treatment, the magnesium alloy substrate is placed in the sand blasting equipment, the abrasive with a particle size of 2.5 mm is used, and the surface treatment is carried out under the air pressure of 0.7 MPa; Step three: polyol synthesis, under the protection of nitrogen, 1,1,4-cyclohexane tri-methanol, triethyl orthoacetate and anhydrous acidic catalyst are added to the reaction kettle according to the molar ratio of 4:1, and stirred at 80℃ for 20 hours, then neutralized by alkaline solution, dissolved in chloroform, washed with water, purified and precipitated by methanol to obtain polyol with a molecular weight of 200,000; Step four: coating spraying, the polyol is dissolved in chloroform to form a 1g / 100ml solution, and the magnesium alloy substrate is sprayed on the surface of the magnesium alloy substrate by 70 times of circular spraying through the spraying equipment to form a uniform coating with a thickness of 20μm.

[0042] In step two: In the sand blasting process, the abrasive is made of alumina or silicon carbide, the abrasive particle size is 2.5mm, and the air pressure is 0.7MPa; the surface roughness of the magnesium alloy substrate after sand blasting treatment is controlled at 3.6μm; The cooperative control of abrasive particle size and air pressure needs to meet one of the following technical solutions: I. When fine abrasive is used, abrasive particles with a particle size of 1.5mm are selected, and the corresponding air pressure is adjusted to 0.6MPa, at which time a micro-rough structure with a roughness of 2.1μm is formed on the surface; II. When coarse abrasive is used, abrasive particles with a particle size of 2.5mm are selected, and the corresponding air pressure is adjusted to 0.7MPa, at which time a macro-rough structure with a roughness of 2.5μm is formed on the surface; The roughness control accuracy needs to be ensured within an error range of ±0.2μm.

[0043] The technical solution of surface roughness is 3.0μm; The cleaning process after sand blasting treatment specifically includes: the substrate is completely immersed in anhydrous ethanol solution of analytical purity, and an ultrasonic cleaning instrument with a frequency of 40kHz is used for treatment for 10.5 minutes; The drying process is carried out in a blast drying oven, and the temperature is set to 52℃, and the continuous drying time is 62 minutes; After drying, the substrate needs to be cooled to room temperature in a drying dish before subsequent treatment.

[0044] In step three: In the polyol synthesis reaction, the molar ratio of 1,1,4-cyclohexane tri-methanol to triethyl orthoacetate is 4:1; The catalyst is phosphotungstic acid solid powder, and the addition amount is 1.0% of the weight of the monomer; The reaction system needs to be continuously supplied with high-purity nitrogen with a purity of ≥99.999%; The neutralization process after the reaction is terminated is specifically: adding 10% ammonia solution drop by drop until the pH value of the reaction solution reaches 7.5. The polyurethane molecular weight is 200,000, and the molecular weight is tested by gel permeation chromatography GPC.

[0045] The polyurethane molecular weight is directly related to the monomer molar ratio: When the molar ratio is controlled at 3:1, the molecular weight of the obtained polymer is 150,000; When the molar ratio is controlled at 4:1, the molecular weight of the obtained polymer is 200,000; The dispersion coefficient of the molecular weight distribution needs to be controlled below 1.5; During the polymer precipitation process, the volume ratio of methanol to chloroform solution is 5:1; The obtained solid is dried in a blast drying oven at 40°C for 12 hours.

[0046] In the coating spraying process, the solution concentration is controlled at 1.0g / 100ml, the spraying equipment uses a high-pressure airless sprayer, the nozzle diameter is 0.5mm, and the spraying process parameters need to meet one of the following technical solutions: I. When the solution concentration is 0.75g / 100ml, the spraying cycle number is controlled at 70 times; II. When the solution concentration is 1.0g / 100ml, the spraying cycle number is controlled at 50 times; The single spraying thickness increment is controlled at 0.3μm / time, and the interval time between each layer spraying is ≥3 minutes.

[0047] The accurate control of the coating thickness needs to meet the following mapping relationship: The thickness of 15μm corresponds to the technical solution: solution concentration 1.0g / 100ml and spraying number 40 times; The thickness of 20μm corresponds to the technical solution: solution concentration 0.75g / 100ml and spraying number 70 times; The coating uniformity requirement: the thickness difference of any three points is ≤±1.5μm; Spraying environment requirement: temperature 25±5℃, relative humidity ≤40%RH.

[0048] The magnesium alloy base material is selected from degradable magnesium alloy, wherein the content of magnesium element is ≥90wt%; The alloy elements include but are not limited to at least one of Fe, Ca, Ni, Mn, Sr, Cu, Zn, and Zr; The technical solution adopts Mg-Zn alloy, and the content of zinc element is controlled at 2.0wt%; The base mechanical performance requirement: tensile strength ≥200MPa, elongation ≥10%.

[0049] The oral fixation pin comprises a magnesium alloy base and a polyolactone coating layer covering the surface of the base. The surface roughness of the base is controlled at 3.0 μm. The coating layer has a thickness of 20 μm and a molecular weight of 200,000. The interface bonding strength between the coating layer and the base is ≥60 N. The microstructure of the coating layer is a continuous dense film layer without visible cracks and hole defects. The overall degradation period of the fixation pin is 12 months.

[0050] The coating layer exhibits hydrophobic properties in an alkaline implant environment with a pH of 8.0, and the static water contact angle is ≥90°. The degradation rate control index: when immersed in the simulated body fluid SBF at 37°C, the degradation rate is ≤0.05 mm / year. The magnesium ion release control index: the release rate is ≤0.2 mg / cm 2 ·day. Flame retardant performance requirement: oxygen index ≥30%. Mechanical performance requirement: bending strength ≥120 MPa, shear strength ≥40 MPa. Biocompatibility requirement: cytotoxicity grade 0, bone bonding rate ≥80%.

[0051] Comparative Example 1, the difference between this comparative example and Example 1 is that this comparative example does not control the abrasive particle size and air pressure in coordination, and the surface roughness control step is omitted.

[0052] Comparative Example 2, the difference between this comparative example and Example 1 is that this comparative example does not control the corresponding relationship between the monomer molar ratio and the molecular weight, and the molecular weight determination step is omitted.

[0053] Comparative Example 3, the difference between this comparative example and Example 1 is that this comparative example does not specify the spraying environment parameters and layer spacing operation, and the coating uniformity control requirement is omitted.

[0054] Comparative Example 4, the difference between this comparative example and Example 1 is that in the polyolactone synthesis process of step three, an equal amount of pentaerythritol is used to replace 1,1,4-cyclohexane trimethyl alcohol in the polyolactone synthesis reaction.

[0055] Comparative Example 5, the difference between this comparative example and Example 1 is that in the polyolactone synthesis process of step three, an equal amount of ethyl orthoacetate is used to replace ethyl orthoacetate in the polyolactone synthesis reaction.

[0056] The oral fixation pins prepared in Examples 1-3 and Comparative Examples 1-5 are subjected to performance testing, and the test items and test methods are as follows: Bonding strength test, under the condition of tensile rate 1 mm / min, ambient temperature 25℃, using universal material testing machine, vertical tensile load was applied to the coating and substrate to peel off, the maximum load value was recorded, and the interfacial bonding strength was calculated; Degradation rate test, under the condition of simulated body fluid SBF immersion environment, temperature 37±1℃, continuous immersion for 30 days, using precision 0.1 mg analytical balance to measure the average mass loss per week, and the linear degradation rate was calculated; Biocompatibility test, in the cell culture environment, L-929 fibroblast cells were inoculated on the surface of the sample at a density of 1×10 4 cells / cm 2 After 24 hours of culture, the relative proliferation rate of cells was determined by CCK-8 method, and the cytotoxicity grade was evaluated; Mechanical property test, using universal material testing machine, three-point bending test was carried out at a loading rate of 0.5 mm / min, the load value at the moment of fracture was measured, and the bending strength was calculated.

[0057] The test data of the oral fixation pins prepared in examples 1-3 and comparative examples 1-5 were recorded in the following table: Test item Bond strength (N) Degradation rate (mm / year) Oxygen index (%) Flexural strength (MPa) Example 1 72±3 0.040±0.005 32±1 135 Example 2 68±2 0.045±0.005 31±1 132 Example 3 75±3 0.035±0.005 33±1 140 Comparative Example 1 40±5 0.12±0.02 28±1 100 Comparative Example 2 45±3 0.20±0.03 26±1 95 Comparative Example 3 38±4 0.15±0.02 27±1 90 Comparative Example 4 50±3 0.10±0.01 29±1 105 Comparative Example 5 30±4 0.24±0.04 25±1 85 By comparing and analyzing the data in the table, it can be seen that the oral fixation nail prepared by the process in Examples 1-3 has more excellent performance than Comparative Examples 1-5, which shows that the polyorthoester coating exhibits hydrophobic characteristics in the weak alkaline environment of the oral cavity, forming a dense physical barrier to isolate the direct contact between the body fluid and the magnesium alloy substrate, slowing down the degradation rate of the substrate material, and ensuring that the fixation nail maintains stable mechanical strength and fixation effect during the bone regeneration period; at the same time, through careful design of the molecular chain, a continuous and uniform film layer structure is formed, filling the micro defects on the surface of the magnesium alloy, avoiding premature failure caused by local stress concentration during the degradation process, thereby prolonging the service life of the fixation nail and providing a reliable time window for bone tissue regeneration. The sandblasting process creates a micro-rough structure on the surface of the magnesium alloy substrate, enhancing the interfacial bonding force of the coating and the substrate; by controlling the synergistic effect of the abrasive particle size and air pressure, the surface roughness is optimized, so that the polyorthoester coating can penetrate into the substrate micropores and form mechanical interlocking, preventing the coating from peeling or falling off during implantation or body fluid erosion; in addition, this treatment also enhances the active site density on the surface of the substrate, promoting the chemical bonding of the coating material at the interface, and building a firm and durable composite system to ensure that the fixation nail always maintains integrity and functionality in the dynamic oral environment. The degradation regulation mechanism of the polyorthoester coating cooperates with the magnesium alloy substrate to achieve overall optimization of biocompatibility; the slow degradation process of the coating releases a controllable concentration of magnesium ions, avoiding the cytotoxicity reaction caused by excessive ion levels, and at the same time, regulating the proliferation and differentiation of bone cells through ion gradient, promoting bone tissue regeneration and healing; in addition, the synergistic degradation characteristics of the coating and the substrate also form a time-matched release curve, ensuring stable ion supply and mechanical support during the key stage of bone regeneration, thereby comprehensively improving the clinical safety and treatment effect of the fixation nail.

[0058] By comparing and analyzing the relevant data in the table, it can be seen that the oral fixation nail prepared by the preparation process of the application has not only high bonding strength and bending strength, but also excellent degradation control performance, flame retardancy and biocompatibility. Therefore, the oral fixation nail and its coating preparation process provided by the application have a broader market prospect and are more suitable for promotion.

[0059] Although embodiments of the application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a coating of an oral fixture pin, characterized by It comprises the following steps: Step one: base preparation, select magnesium alloy material, through numerical control processing into oral fixed pin base, the fixed pin includes diameter 2.5-4mm disc-shaped pin cap and diameter 1-1.5mm pin body; Step two: sand blasting treatment, magnesium alloy base is placed in sand blasting equipment, the particle size of 0.5-2.5mm abrasive is used, the surface treatment is carried out under 0.5-0.7MPa air pressure; Step three: poly (alkenoate) synthesis, under nitrogen protection environment, 1,1,4-cyclohexane trimethyl alcohol, triethyl orthoacetate are added into the reaction kettle according to the molar ratio of 2-4:1 and anhydrous acidic catalyst, stirring reaction at 70-80℃ for 18-20 hours, after neutralization by alkaline solution, chloroform dissolution, water washing purification and methanol precipitation, poly (alkenoate) with molecular weight of 5-20 million is obtained; Step four: coating spraying, poly (alkenoate) is dissolved in chloroform to form 0.5-1g / 100ml solution, 30-70 times of cycle spraying is carried out on the surface of magnesium alloy base through spraying equipment, forming uniform coating with thickness of 5-20μm.

2. The method for preparing a coating for an oral fixation screw according to claim 1, characterized in that, In step two: In the sand blasting process, the abrasive is selected from alumina or silicon carbide, the abrasive particle size is selected in the range of 0.5-2.5mm, and the air pressure is controlled in the range of 0.5-0.7MPa; The surface roughness of the magnesium alloy base after sand blasting treatment is controlled in the range of 1.2-3.6μm; The cooperative control of abrasive particle size and air pressure needs to meet one of the following technical solutions: Ⅰ, when fine abrasive is used, the abrasive particle with particle size of 0.5-1.5mm is selected, and the air pressure is adjusted to 0.5-0.6MPa, at this time, the micro-rough structure with 1.8-2.1μm is formed on the surface; Ⅱ, when coarse abrasive is used, the abrasive particle with particle size of 1.5-2.5mm is selected, and the air pressure is adjusted to 0.6-0.7MPa, at this time, the macro-rough structure with 2.1-2.5μm is formed on the surface; The roughness control accuracy needs to ensure the error range of ±0.2μm.

3. The method for preparing a coating for an oral fixation screw according to claim 2, characterized in that, The surface roughness is 1.5-3.0μm; The cleaning process after sand blasting treatment specifically includes: the base is completely immersed in anhydrous ethanol solution of analytical purity, and treated by ultrasonic cleaning instrument with frequency of 40kHz for 9.5-10.5 minutes; The drying process is carried out in a blast drying oven, the temperature is set to 48-52℃, and the continuous drying time is 58-62 minutes; After drying, the base needs to be cooled to room temperature in a drying dish before subsequent treatment.

4. The oral fixation screw and its coating preparation method according to claim 1, characterized in that, In step three; In the poly (alkenoate) synthesis reaction, the molar ratio of 1,1,4-cyclohexane trimethyl alcohol to triethyl orthoacetate is 3-4:1; The catalyst uses phosphotungstic acid solid powder, and the addition amount is 0.5-1.0% of the weight of monomer; The reaction system needs to be continuously supplied with high-purity nitrogen with purity≥99.999%; The neutralization process after reaction termination is as follows: ammonia solution with concentration of 10% is added dropwise until the pH value of the reaction solution reaches 6.5-7.5; The polyorthoester molecular weight is 10-20 million, and the molecular weight is tested by gel permeation chromatography GPC.

5. The method of claim 4, wherein the coating is applied by a method selected from the group consisting of: spray coating, dip coating, spin coating, and combinations thereof. The control of the polyorthoester molecular weight has a direct correspondence with the monomer molar ratio: When the molar ratio is controlled in the range of 2-3:1, the molecular weight of the obtained polymer is in the range of 5-15 million; When the molar ratio is controlled in the range of 3-4:1, the molecular weight of the obtained polymer is in the range of 15-20 million; The dispersion coefficient of the molecular weight distribution needs to be controlled below 1.5; During the polymer precipitation process, the volume ratio of methanol to chloroform solution is 5:1; The obtained solid is dried in a blast drying oven at 40°C for 12 hours.

6. The method for preparing a coating for an oral fixation screw according to claim 1, characterized in that, In step four: In the coating spraying process, the solution concentration is controlled between 0.5-1.0 g / 100 ml, the spraying equipment uses a high-pressure airless sprayer, the nozzle diameter is 0.3-0.5 mm, and the spraying process parameters need to meet one of the following technical solutions: Ⅰ. When the solution concentration is 0.5-0.75 g / 100 ml, the spraying cycle number is controlled in 50-70 times; Ⅱ. When the solution concentration is 0.75-1.0 g / 100 ml, the spraying cycle number is controlled in 30-50 times; The single spraying thickness increment is controlled in 0.15-0.3 μm / time, and the interval time between each layer spraying is ≥3 minutes.

7. The method of claim 6, wherein the coating is applied by a process selected from the group consisting of: spray coating, dip coating, spin coating, and combinations thereof. The accurate control of the coating thickness needs to meet the following mapping relationship: Thickness 12-15 μm corresponds to the technical solution: solution concentration 0.75-1.0 g / 100 ml and spraying number 30-40 times; Thickness 15-20 μm corresponds to the technical solution: solution concentration 0.5-0.75 g / 100 ml and spraying number 50-70 times; Coating uniformity requirement: thickness difference of any three points ≤±1.5 μm; Spraying environment requirement: temperature 25±5°C, relative humidity ≤40% RH.

8. The method for preparing a coating for an oral fixation screw according to claim 1, characterized in that, The magnesium alloy base material is selected from degradable magnesium alloys, wherein the content of magnesium element is ≥90 wt%; The alloy elements include but are not limited to at least one of Fe, Ca, Ni, Mn, Sr, Cu, Zn, and Zr; The technical solution adopts Mg-Zn alloy, and the content of zinc element is controlled in 0.5-2.0 wt%; The base mechanical performance requirement: tensile strength ≥200 MPa, elongation ≥10%.

9. An orthodontic anchor prepared by the method of any one of claims 1 to 8, characterized by: The oral fixation pin includes a magnesium alloy base and a polyorthoester coating covering the surface of the base: The base surface roughness is controlled in the range of 1.5-3.0 μm; The coating thickness is 10-20 μm, and the molecular weight is 10-20 million; The interface bonding strength between the coating and the base is ≥60 N; The microstructure of the coating is a continuous and dense film layer without visible cracks and hole defects; The overall degradation period of the fixation pin is 6-12 months.

10. The oral fixation pin according to claim 9, characterized in that: The coating exhibits hydrophobic properties in an alkaline implantation environment with pH 7.4-8.0, and the static water contact angle is ≥90°; Degradation rate control index: when immersed in simulated body fluid SBF at 37°C, the degradation rate is ≤0.05 mm / year; Magnesium ion release control index: the release rate is ≤0.2 mg / cm²·day after 12 weeks of immersion; Flame retardant performance requirements: oxygen index ≥ 30%; Mechanical performance requirements: bending strength ≥ 120 MPa, shear strength ≥ 40 MPa; Biocompatibility requirements: cytotoxicity grade 0, bone bonding rate ≥ 80%.

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