A method for the bioactive and biocompatible surface treatment of dentures and implants

Abstract

The present application relates to the technical field of biomedical materials, and discloses a biological activity and biocompatibility surface treatment method for dentures and implants, which comprises the following steps: a) performing surface pretreatment on the base body of the denture or implant; b) applying a composite coating containing hydroxyapatite particles and biocompatible resin adhesive on the surface of the pretreated base body; c) performing low-temperature thermal curing on the composite coating to form a composite coating layer; and d) performing precision polishing on the surface of the cured composite coating layer to selectively remove part of the resin adhesive on the surface. Through mechanical locking of the base body surface and chemical combination of the interface inside the coating, a composite coating layer which is firmly combined with the base body and chemically stable is obtained; meanwhile, through low-temperature curing and surface activation treatment, the hydroxyapatite is exposed on the surface of the coating layer while the biological activity of the hydroxyapatite is retained, so that the coating layer is endowed with effective biological functions.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, specifically to a method for surface treatment of dentures and implants that enhances bioactivity and biocompatibility. Background Technology

[0002] In the field of medical implants, titanium and its alloys are widely used due to their mechanical properties and bioinertness. However, their bioinert surfaces cannot form a direct biological bond with bone tissue, potentially leading to instability at the interface between the implant and the surrounding bone. To address this issue, existing technologies typically apply a bioactive coating to the surface of titanium alloys. Among these, hydroxyapatite, due to its chemical composition being similar to the inorganic components of human bone, is one of the most widely used coating materials.

[0003] Currently, the technologies for preparing hydroxyapatite coatings are mainly divided into two categories: high-temperature and low-temperature. High-temperature technology is represented by plasma spraying, which melts hydroxyapatite powder at a high temperature and sprays it onto the substrate surface. However, the high-temperature environment of plasma can cause thermal decomposition of hydroxyapatite, generating other phases such as calcium phosphate or amorphous phases, thereby altering its original chemical structure and reducing or eliminating its bone-inducing bioactivity. In addition, the significant difference in the coefficients of thermal expansion between the ceramic coating and the metal substrate can generate large residual stress during cooling, easily leading to coating cracking or peeling, affecting the long-term bonding stability of the coating.

[0004] To avoid the degradation of hydroxyapatite's activity by high temperatures, low-temperature preparation techniques have been developed. A typical method involves dispersing hydroxyapatite particles as fillers in a polymer binder to form a composite coating, which is then applied to the substrate surface and cured at low temperatures. However, this technology also presents inherent technical challenges. First, titanium alloy surfaces typically have a dense oxide film with inert chemical properties, resulting in limited physical adhesion between the polymer coating and the substrate. Second, hydroxyapatite, as an inorganic ceramic material, has vastly different physicochemical properties from organic polymer binders, leading to poor interfacial compatibility. This can cause hydroxyapatite particles to agglomerate in the resin, weakening the interfacial bond between the filler and the binder and affecting the coating's cohesive strength. The most critical technical obstacle lies in the fact that after the composite coating cures, the polymer binder inevitably completely encapsulates the hydroxyapatite particles, forming a continuous, non-biologically active polymer film on the outermost layer. This film hinders direct contact between hydroxyapatite and the external physiological environment, preventing it from effectively exerting its biological activity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for surface treatment of dentures and implants that improves bioactivity and biocompatibility. This method solves the problems of insufficient bonding strength between the coating and the metal substrate, and loss of bioactivity of the coating surface due to complete encapsulation of the active filler by the polymer adhesive, when preparing hydroxyapatite composite coatings at low temperatures.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for surface treatment of dentures and implants to enhance bioactivity and biocompatibility, comprising the following steps:

[0007] a) Perform surface pretreatment on the base material of the denture or implant;

[0008] b) Apply a composite coating comprising hydroxyapatite microparticles and a biocompatible resin binder to the pretreated substrate surface;

[0009] c) The composite coating is subjected to low-temperature thermosetting to form a composite coating layer;

[0010] d) The surface of the cured composite coating is precision polished to selectively remove some of the resin adhesive on the surface, exposing the hydroxyapatite particles encapsulated inside to the outermost surface of the coating.

[0011] Preferably, the hydroxyapatite particles in the composite coating are hydroxyapatite surface-modified with a silane coupling agent, and the biocompatible resin binder is an organosilicon-modified epoxy resin.

[0012] Preferably, when the substrate is a titanium alloy implant, the surface pretreatment in step a) is to perform anodic electrolysis on the substrate in an electrolyte to form a micro-depression structure on its surface caused by intergranular corrosion.

[0013] Preferably, when the substrate is a zirconia denture, the surface pretreatment in step a) is to apply a layer of silane coupling agent to the surface of the substrate.

[0014] Preferably, the low-temperature thermosetting temperature range of c) is 100-150℃.

[0015] Preferably, the precision polishing of d) is performed using a magnetorheological polishing process.

[0016] A bioactive denture or implant, comprising:

[0017] Matrix;

[0018] A composite coating disposed on the surface of the substrate;

[0019] The composite coating is composed of the following components by mass percentage:

[0020] Hydroxyapatite microparticles: 70%–80%;

[0021] Biocompatible silicone-modified epoxy resin adhesive: 20%–30%; and the hydroxyapatite microparticles on the outermost exposed portion of the composite coating.

[0022] Preferably, the substrate is a titanium alloy, and the surface of the substrate has a micro-recessed structure between the substrate and the composite coating.

[0023] Preferably, the substrate is zirconium dioxide, and a silane coupling agent layer is provided between the substrate and the composite coating.

[0024] Preferably, the hydroxyapatite microparticles are microparticles with surface modification by organic functional groups and a particle size D50 of 5-15 μm.

[0025] This invention provides a method for surface treatment of dentures and implants that enhances bioactivity and biocompatibility.

[0026] It has the following beneficial effects:

[0027] 1. This invention pre-treats the substrate surface electrochemically, forming a microscopic mechanical locking structure that provides a physical anchoring basis for subsequent coatings. Simultaneously, the surface-modified hydroxyapatite and organosilicon-modified epoxy resin in the composite coating form an effective interfacial bond, enhancing the coating's cohesive strength. The synergistic effect of these two mechanisms results in a coating with peel resistance, ensuring its long-term adhesion to the substrate.

[0028] 2. The low-temperature curing step in the process flow of this invention completely preserves the chemical structure and functional properties of hydroxyapatite as a bioactive component. More importantly, by adding a surface activation treatment step after coating curing, this invention selectively removes the resin layer covering the surface of the hydroxyapatite particles, exposing the bioactive particles to the outermost layer of the coating. This creates a functional interface that can directly interact with the external environment, solving the technical problem that the active filler is completely encapsulated by the inert adhesive and cannot function.

[0029] 3. The biocompatible adhesive used in this invention is a special silicone-modified epoxy resin. After curing, the polymer network formed by this resin has high crosslinking density and hydrolysis resistance. This stable chemical structure can effectively fix all components in the coating, significantly reducing the possibility of organic matter leaching from the coating, thereby ensuring the overall biocompatibility of the coating. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a method for surface treatment of dentures and implants to improve bioactivity and biocompatibility, comprising the following steps:

[0032] a) Perform surface pretreatment on the base material of the denture or implant;

[0033] b) Apply a composite coating containing hydroxyapatite microparticles and a biocompatible resin binder to the pretreated substrate surface;

[0034] c) Low-temperature thermosetting of the composite coating to form a composite coating layer;

[0035] d) The surface of the cured composite coating is precision polished to selectively remove some of the resin adhesive on the surface, exposing the hydroxyapatite particles encapsulated inside to the outermost surface of the coating.

[0036] The first step is substrate surface pretreatment. This step establishes a stable bonding interface between the substrate material and the subsequently applied composite coating. Different pretreatment techniques are used for different substrate materials. When the substrate is a titanium alloy, anodic electrolysis is used. This treatment places the titanium alloy implant in a specific electrolyte as the anode and applies direct current. Due to the differences in the anodic dissolution potentials of the various components in the titanium alloy, some elements preferentially dissolve during electrolysis, forming micron-sized, irregular depressions and pore structures on the substrate surface. These three-dimensional structures increase the surface area of ​​the substrate and provide numerous physical locking points for the coating material during subsequent coating curing, forming a mechanical embedded connection and establishing physical bonding between the substrate and the coating. When the substrate is a zirconia ceramic material, a silane coupling agent is used. This treatment involves applying a silane coupling agent containing specific organic functional groups to the zirconia surface. One end of the silane coupling agent molecule can chemically react with the inorganic zirconium dioxide surface to form a stable chemical bond, while the organic functional group at the other end can covalently bond with the resin binder in the subsequent coating during the curing process. Through this chemical connection, a molecular-level connection is formed between the inorganic matrix and the organic coating.

[0037] The second step is the application of the composite coating. In this step, a composite coating consisting of hydroxyapatite microparticles as a bioactive filler and silicone-modified epoxy resin as a biocompatible binder is uniformly applied to the pretreated substrate surface. The hydroxyapatite microparticles have undergone surface modification treatment. This modification treatment uses a silane coupling agent to graft organic functional groups onto the surface of the inorganic hydroxyapatite particles. This improves the interfacial compatibility between the inorganic filler and the organic resin binder, inhibits phase separation during mixing and curing, and ensures that the hydroxyapatite microparticles can be uniformly and stably dispersed throughout the resin matrix, forming a homogeneous composite coating.

[0038] The third step is low-temperature thermosetting. In this step, the workpiece coated with the composite coating is placed within a specific temperature range for heat treatment. This temperature must be sufficient to initiate the cross-linking reaction of the silicone-modified epoxy resin, transforming it from a liquid slurry into a solid film with defined mechanical strength, thereby firmly coating and fixing the hydroxyapatite particles to the substrate surface. Simultaneously, this curing temperature must be below the critical temperature at which hydroxyapatite undergoes thermal decomposition and loses its inherent biological activity. Through this low-temperature curing, the physical structure of the coating is maintained while preserving the chemical structure and functional integrity of its core bioactive components.

[0039] The fourth step is the surface activation treatment of the coating. This step is crucial for achieving the final technical effect of this invention. After low-temperature curing, the outermost surface of the composite coating is a smooth resin adhesive layer, completely encapsulating the hydroxyapatite particles inside, preventing direct contact with the external environment and thus hindering the expression of its biological activity. This step uses magnetorheological polishing to treat the surface of the cured coating. Magnetorheological polishing technology utilizes the significant differences in mechanical hardness and wear resistance between organic resin adhesives and inorganic hydroxyapatite particles. By precisely controlling the shear stress generated by the magnetorheological fluid under the action of a magnetic field, the softer resin adhesive can be removed more efficiently, while the wear on the harder hydroxyapatite particles is minimal. This differentiated material removal rate allows for selective stripping of the surface resin at the microscopic level during the macroscopically uniform and smooth polishing process, ultimately exposing the tips of the previously encapsulated hydroxyapatite particles to the outermost layer of the coating, thereby creating a functionalized surface with biological activity that can directly contact human tissue.

[0040] Example 1

[0041] This embodiment provides a specific preparation process for a bioactive and biocompatible surface treatment method.

[0042] Step 1: Preparation of Bioactive Composite Coatings

[0043] 1.1 Preparation of hydroxyapatite powder: Calcium hydrogen phosphate dihydrate and deionized water were mixed at a mass-to-volume ratio of 1:2.4 and placed in a reaction vessel. The mixture was heated to 200℃ and reacted for 3 hours. After the reaction, the product was washed with deionized water until the pH value reached 6.5, and then dehydrated and dried. The dried material was then ground in an alumina ball mill for 5 hours to obtain micro-powder with a D50 particle size of 10 μm. Finally, the micro-powder was surface-treated using a silane coupling agent.

[0044] 1.2 Preparation of organosilicon-modified epoxy resin: Methyltriethoxysilane, deionized water, epoxy resin and aminosilane were placed in a reaction vessel and reacted at 50℃ and 0.8MPa for 5 hours to obtain organosilicon-modified epoxy resin.

[0045] 1.3 Composite Coating Preparation: The hydroxyapatite micro powder obtained in step 1.1 and the organosilicon modified epoxy resin obtained in step 1.2 are mixed at a mass ratio of 75:25, diluted with anhydrous ethanol and stirred evenly to form a slurry.

[0046] Step 2: Substrate Surface Pretreatment

[0047] The titanium alloy substrate was placed in the electrolyte as the anode, and a 5V DC voltage was applied for electrolysis at room temperature for 2 minutes.

[0048] Step 3: Application and curing of the composite coating

[0049] The slurry prepared in step 1.3 was applied to the pretreated substrate surface using a spraying process, and excess slurry was removed by centrifugation. Subsequently, the workpiece was placed in an oven at 125°C and heated for 5 hours, and then left to stand for at least 48 hours.

[0050] Step 4: Surface activation treatment of the coating

[0051] The surface of the cured composite coating is treated with magnetorheological polishing technology to expose hydroxyapatite particles on the outermost surface of the coating.

[0052] Example 2

[0053] This embodiment provides a specific preparation process for a bioactive and biocompatible surface treatment method.

[0054] Step 1: Preparation of Bioactive Composite Coatings

[0055] 1.1 Preparation of hydroxyapatite powder: A mixture of dicalcium phosphate dihydrate and deionized water was placed in a reactor, heated to 180℃, and reacted for 2 hours. After the reaction, the product was washed with deionized water until the pH value reached 6.0, and then dehydrated and dried. The dried material was then ground in an alumina ball mill for 4 hours to obtain micro-powder with a D50 particle size of 15 μm. Finally, the micro-powder was surface-treated using a silane coupling agent.

[0056] 1.2 Preparation of organosilicon-modified epoxy resin: Methyltriethoxysilane, deionized water, epoxy resin and aminosilane were placed in a reaction vessel and reacted at 40℃ and 0.5MPa for 4 hours to obtain organosilicon-modified epoxy resin.

[0057] 1.3 Composite Coating Preparation: The hydroxyapatite micro powder obtained in step 1.1 and the organosilicon modified epoxy resin obtained in step 1.2 are mixed at a mass ratio of 70:30, diluted with anhydrous ethanol and stirred evenly to form a slurry.

[0058] Step 2: Substrate Surface Pretreatment

[0059] The titanium alloy substrate was placed in the electrolyte as the anode, and a DC voltage of 2V was applied for electrolysis at room temperature for 1 minute.

[0060] Step 3: Application and curing of the composite coating

[0061] The slurry prepared in step 1.3 was applied to the pretreated substrate surface using a dip-coating process, and excess slurry was removed by centrifugation. Subsequently, the workpiece was placed in an oven at 100°C and heated for 4 hours, and then left to stand for at least 48 hours.

[0062] Step 4: Surface activation treatment of the coating

[0063] The surface of the cured composite coating is treated with magnetorheological polishing technology to expose hydroxyapatite particles on the outermost surface of the coating.

[0064] Example 3

[0065] This embodiment provides a specific preparation process for a bioactive and biocompatible surface treatment method.

[0066] Step 1: Preparation of Bioactive Composite Coatings

[0067] 1.1 Preparation of hydroxyapatite powder: A mixture of dicalcium phosphate dihydrate and deionized water was placed in a reactor, heated to 220℃, and reacted for 4 hours. After the reaction, the product was washed with deionized water until the pH value reached 7.0, and then dehydrated and dried. The dried material was then ground in an alumina ball mill for 6 hours to obtain micro-powder with a D50 particle size of 5 μm. Finally, the micro-powder was surface-treated using a silane coupling agent.

[0068] 1.2 Preparation of organosilicon-modified epoxy resin: Methyltriethoxysilane, deionized water, epoxy resin and aminosilane were placed in a reaction vessel and reacted at 60℃ and 1.0MPa for 6 hours to obtain organosilicon-modified epoxy resin.

[0069] 1.3 Composite Coating Preparation: The hydroxyapatite micro powder obtained in step 1.1 and the organosilicon modified epoxy resin obtained in step 1.2 are mixed at a mass ratio of 80:20, diluted with anhydrous ethanol and stirred evenly to form a slurry.

[0070] Step 2: Substrate Surface Pretreatment

[0071] The titanium alloy substrate was placed in the electrolyte as the anode, and an 8V DC voltage was applied for electrolysis at room temperature for 3 minutes.

[0072] Step 3: Application and curing of the composite coating

[0073] The slurry prepared in step 1.3 was applied to the pretreated substrate surface using a brush coating process, and excess slurry was removed by centrifugation. Subsequently, the workpiece was placed in an oven at 150°C and heated for 6 hours, and then left to stand for at least 48 hours.

[0074] Step 4: Surface activation treatment of the coating

[0075] The surface of the cured composite coating is treated with magnetorheological polishing technology to expose hydroxyapatite particles on the outermost surface of the coating.

[0076] Comparative Example 1

[0077] Compared with Example 1, the difference is that in the preparation of the composite coating in step 1.3, the mass ratio of hydroxyapatite micro powder to organosilicon modified epoxy resin is 50:50, and all other aspects are the same.

[0078] Comparative Example 2

[0079] Compared with Example 1, the difference is that in step 1.1, after obtaining the hydroxyapatite micro powder, no silane coupling agent is used to perform surface treatment on it; otherwise, they are the same.

[0080] Comparative Example 3

[0081] Compared with Example 1, the difference is that the substrate surface pretreatment in step 2 is omitted, and the slurry prepared in step 1.3 is directly applied to the untreated titanium alloy substrate surface; all other aspects are the same.

[0082] Comparative Example 4

[0083] Compared with Example 1, the difference is that the surface activation treatment of the coating in step 4 is omitted, and the final product is obtained after the composite coating in step 3 is cured. All other aspects are the same.

[0084] Comparative Example 5

[0085] Compared with Example 1, the difference is that in step 3, during the curing of the composite coating, the workpiece is placed in an oven at 450°C for heat treatment, while the rest are the same.

[0086] Comparative Example 6

[0087] Compared with Example 1, the difference is that in step 1.2, methyltriethoxysilane is not used for modification, and unmodified conventional epoxy resin is used as the binder; all other aspects are the same.

[0088] Test Example 1: Coating-Substrate Bond Strength Test

[0089] This test aims to quantitatively evaluate the bonding strength between the coatings prepared in Example 1 and Comparative Examples 1, 2, and 3. The test method employed is the pull-out test, and the specific experimental steps are as follows:

[0090] Test sample preparation: Take the coated and cured samples prepared in Example 1 and Comparative Examples 1-3.

[0091] Test the zipper pull adhesion: Select a cylindrical steel zipper pull with a diameter of 14mm. Sand the surfaces of the zipper pull to be bonded with sandpaper, and then ultrasonically clean with acetone and dry. Apply a two-component epoxy resin adhesive evenly to the end face of the zipper pull, and then vertically bond the zipper pull to the surface of the coating to be tested. Apply constant pressure and maintain at room temperature for 24 hours to allow the adhesive to fully cure.

[0092] Test area delineation: Using a dedicated ring-shaped cutting tool, cut the coating along the edge of the bonded zipper pull, centering on the zipper pull. The cut depth must reach the surface of the titanium alloy substrate to ensure that only the circular area directly below the zipper pull is subjected to stress during testing.

[0093] Tensile load application: Secure the test sample with the pull head to the base of the portable tensile tester. Connect the tester's pull claws to the pull head. Start the tester and apply a tensile load perpendicular to the coating surface to the pull head at a constant loading rate of 0.2 MPa / s.

[0094] Data Recording and Calculation: The instrument automatically records the maximum load (N) at which the coating delamination occurs. This load value is then divided by the cross-sectional area of ​​the pull head (153.9 mm²). 2 The bonding strength (MPa) between the coating and the substrate was calculated. Five measurements were performed on each sample group, and all data were recorded.

[0095] Table 1: Coating bond strength test data for different samples

[0096]

[0097]

[0098] The influence of substrate surface morphology on coating adhesion was clarified by combining strength test data. By electrochemically treating the titanium alloy substrate surface to create a micro-recessed structure, the subsequently coated composite material can form a physical-mechanical interlock with the substrate after curing. Compared with coatings applied directly to smooth substrate surfaces, this mechanical anchoring structure provides significantly higher tensile peel strength, solving the technical problem of weak coating-substrate adhesion.

[0099] The cohesive strength of the coating itself is another key factor determining the overall bonding performance. By surface-modifying the hydroxyapatite filler, effective chemical bonds were established between the inorganic filler and the silicone-modified epoxy resin adhesive. This improved the interfacial compatibility between the filler and the resin matrix, allowing stress to be effectively transferred within the composite material rather than prematurely causing failure at weak interfaces. This enhanced the overall cohesive strength of the coating material, ensuring its structural integrity.

[0100] The mass ratio of each component in a composite coating is also a decisive factor affecting the final mechanical properties of the coating. Experimental results show that, in the material system used, there is a specific mass ratio between the hydroxyapatite filler and the resin binder. The composite coating cured under this ratio can withstand a higher destructive load than those with other ratios. This confirms that the macroscopic mechanical strength of the final coating can be effectively controlled by precisely controlling the composition ratio of each component.

[0101] Test Example 2: In vitro bioactivity test of coating

[0102] This test case aims to quantitatively evaluate the ability of the coating samples prepared in Examples 1, 4, and 5 to induce apatite deposition by immersion in simulated body fluid (SBF), which is used to characterize the in vitro bioactivity of the coatings.

[0103] Experimental steps:

[0104] SBF solution preparation: Dissolve the reagents in a 37.0℃ water bath according to the following formula: add 8.035g NaCl, 0.355g NaHCO3, 0.225g KCl, 0.231g K2HPO4·3H2O, 0.311g MgCl2·6H2O, 0.292g CaCl2, and 0.072g Na2SO4 per liter of deionized water. Precisely adjust the pH of the SBF solution to 7.40 using tris(hydroxymethyl)aminomethane (Tris) and 1M HCl solution.

[0105] Initial sample weighing: Coated samples measuring 10mm × 10mm × 2mm were ultrasonically cleaned in acetone for 5 minutes, rinsed with deionized water, and dried in a 60℃ oven until constant weight. The initial mass (m0) of each sample was weighed using an analytical balance with an accuracy of 0.01mg and recorded.

[0106] Immersion test: Each weighed sample was placed independently in a clean, sealed polyethylene container. The ratio of the sample coating surface area to SBF volume was 10 mm². 2 Add 24 mL of SBF solution (total sample surface area 240 mm²) to each container at a ratio of 1 mL. 2 Place all sealed containers in a constant temperature shaker at 37.0℃ and shake slowly at 50 rpm for 14 days.

[0107] Second weighing of samples: After the soaking period, remove the samples from the SBF solution and gently rinse the surface with deionized water to remove residual salts. Dry the rinsed samples in a 60°C oven to constant weight. Weigh the final mass (m1) of each sample using the same analytical balance and record it.

[0108] Data Calculation: The increase in mass per unit area of ​​the sample (Δm / A) is calculated using the following formula: Δm / A=(m1-m0) / A, where A is the total surface area of ​​the coating on the sample (2.4cm²). 2 Repeat the test 3 times for each sample group and record all data.

[0109] Experimental data:

[0110] Table 2: Increase in mass per unit area of ​​different samples after immersion in simulated body fluid for 14 days

[0111]

[0112] By comparing the mass changes of samples before and after immersion in simulated body fluids, it can be determined that the final coating surface treatment step is necessary to obtain bioactivity. Samples without surface activation treatment showed no significant mass change after immersion. The mechanism is that the cured silicone-modified epoxy resin forms a continuous physical barrier on the outermost layer of the coating, completely encapsulating the internal hydroxyapatite particles. This resin layer isolates the hydroxyapatite from contact with the simulated body fluids, preventing it from serving as a nucleation site for inducing mineral deposition; therefore, the coating does not exhibit bioactivity.

[0113] The magnetorheological polishing step in this method utilizes the difference in mechanical hardness between the resin binder and hydroxyapatite to selectively remove the surface resin. This process exposes the previously coated hydroxyapatite particles to the outermost surface of the coating. These exposed hydroxyapatite particles can directly interact with calcium and phosphorus ions in simulated body fluids, acting as nucleation sites to induce the formation of new apatite deposits on their surface. Macroscopically, this process manifests as an increase in the mass per unit area of ​​the sample, thus confirming that surface activation treatment is a key step in acquiring biofunctionality for the composite coating.

[0114] The curing temperature of the coating is another prerequisite for preserving the bioactivity of hydroxyapatite. Samples cured at high temperatures showed a significantly lower mass increase after immersion compared to samples cured at low temperatures. This is because the bioactivity of hydroxyapatite depends on its specific chemical composition and crystal structure. At high temperatures, hydroxyapatite undergoes thermal decomposition reactions such as dehydroxylation, destroying its chemical structure and thus causing it to lose its biological function as a nucleation substrate for apatite. Low-temperature curing, however, operates within the stable temperature range of hydroxyapatite, thus fully preserving its chemical structure and bioactivity.

[0115] Test Example 3: Coating Chemical Stability Test

[0116] This test case aims to quantitatively evaluate the chemical stability of the coatings prepared in Example 1 and Comparative Example 6 in a simulated physiological environment by measuring the total organic carbon (TOC) content in the leachate after immersion in physiological saline.

[0117] Experimental steps:

[0118] Preparation of soaking medium: Prepare a 0.9% sodium chloride (NaCl) aqueous solution as the physiological saline soaking medium.

[0119] Sample preparation and placement: Take coating samples of Example 1 and Comparative Example 6 with dimensions of 10mm × 10mm × 2mm. After rinsing each sample with deionized water, place them in separate, clean polypropylene (PP) sealed tubes.

[0120] Immersion process: Add 20 mL of physiological saline to each sealed tube, ensuring the sample is completely submerged. Place all sealed tubes in a 37.0°C incubator and allow to soak for 28 days.

[0121] Leachate collection: After the soaking period is over, open the sealed tube and use a pipette to draw the supernatant from each tube as the leachate sample to be tested, and place it in a clean sample bottle.

[0122] TOC Concentration Determination: The total organic carbon analyzer (model: ShimadzuTOC-L) was started and calibrated using potassium hydrogen phthalate standard solution. Each leachate sample was sequentially injected into the analyzer. The instrument converted the organic matter in the sample into carbon dioxide using a high-temperature catalytic oxidation method, and the carbon dioxide concentration was measured using a non-dispersive infrared detector (NDIR) to calculate the total organic carbon concentration in the original sample.

[0123] Data recording: Record the TOC concentration (unit: mg / L) of the leachate for each sample. Perform three independent immersion and testing experiments on each group of coating samples, and record all measurement data.

[0124] Experimental data:

[0125] Table 3: Total Organic Carbon (TOC) Concentration of Leachate from Different Samples

[0126] sample group Sample number TOC concentration in leachate (mg / L) Example 1 E3-1 1.1 E3-2 0.8 E3-3 1.3 Comparative Example 6 C6-1 13.7 C6-2 15.2 C6-3 12.9

[0127] The effect of coating adhesive type on coating chemical stability can be evaluated by measuring the total organic carbon (TOC) concentration in the leachate of different samples after immersion in physiological saline. Samples using silicone-modified epoxy resin as the adhesive showed significantly lower TOC concentrations in their leachate compared to samples using unmodified conventional epoxy resin. The only variable in the preparation of these two samples was the chemical composition of the adhesive.

[0128] The high concentration of TOC detected in samples using conventional epoxy resins indicates that organic matter leaching occurred in the coating in a simulated saline environment. The mechanism is that the polymer network formed after the conventional epoxy resin cures has insufficient chemical stability in an aqueous electrolyte environment. Unreacted oligomers or small molecule components within the resin dissolve from the coating matrix over time and enter the solution.

[0129] The low TOC concentration exhibited by samples using silicone-modified epoxy resin is attributed to the specific chemical structure of its binder. By introducing methyltriethoxysilane into the epoxy resin system, more chemically stable silicon-oxygen bonds are formed in the cured polymer network. The presence of these high-energy bonds increases the crosslinking density and hydrolysis resistance of the entire resin matrix, effectively inhibiting the migration of organic components from the coating to the external environment. This data confirms that using silicone-modified epoxy resin as a binder is a necessary technical means to ensure the chemical stability of the coating in physiological environments.

[0130] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for the bioactive and biocompatible surface treatment of dentures and implants, characterized in that, Includes the following steps: a) Perform surface pretreatment on the base material of the denture or implant; b) Apply a composite coating comprising hydroxyapatite microparticles and a biocompatible resin binder to the pretreated substrate surface; c) The composite coating is subjected to low-temperature thermosetting to form a composite coating layer; d) The surface of the cured composite coating is precision polished to selectively remove some of the resin adhesive on the surface, so that the hydroxyapatite particles encapsulated inside are exposed on the outermost surface of the coating. The hydroxyapatite particles in the composite coating are hydroxyapatite surface-modified with a silane coupling agent, and the biocompatible resin adhesive is an organosilicon-modified epoxy resin. The precision polishing described in d) employs a magnetorheological polishing process; The low-temperature thermosetting temperature range of c) is 100-150℃.

2. The method of claim 1, wherein the method is characterized by: When the substrate is a titanium alloy implant, the surface pretreatment in step a) is to perform anodic electrolysis on the substrate in an electrolyte to form a micro-depression structure on its surface caused by intergranular corrosion.

3. The method of claim 1, wherein the method is characterized by: When the substrate is a zirconia denture, the surface pretreatment in step a) is to apply a layer of silane coupling agent to the surface of the substrate.

4. A biological active denture or implant, prepared according to the method of claim 1-3 for biological active and biocompatible surface treatment of a denture and implant, characterized in that, include: Matrix; A composite coating disposed on the surface of the substrate; The composite coating is composed of the following components by mass percentage: Hydroxyapatite microparticles: 70%–80%; Biocompatible silicone-modified epoxy resin adhesive: 20%–30%; and the hydroxyapatite microparticles on the outermost exposed portion of the composite coating.

5. The biologically active denture or implant of claim 4, wherein, The substrate is a titanium alloy, and the surface of the substrate has a micro-recessed structure between the substrate and the composite coating.

6. The biologically active denture or implant of claim 4, wherein, The substrate is zirconium dioxide, and a silane coupling agent layer is provided between the substrate and the composite coating.

7. The biologically active denture or implant of claim 4, wherein, The hydroxyapatite microparticles are surface-modified with a silane coupling agent and have a particle size D50 of 5-15 μm.

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