A dental appliance having a surface-modified antimicrobial composite coating and a method of making the same

Abstract

The application discloses a tooth appliance with a surface-modified antibacterial composite coating and a preparation method thereof. The tooth appliance with the surface-modified antibacterial composite coating is prepared by the following steps: preheating a Tris·HCl solution, adding minocycline hydrochloride into the solution, adjusting the pH of the solution, adding dopamine hydrochloride into the solution to obtain a mixed solution, immersing a pretreated tooth appliance in the mixed solution under stirring, taking out the tooth appliance, washing and drying the tooth appliance, and obtaining the tooth appliance with a polydopamine coating loaded with minocycline. The tooth appliance is placed in 1.5 times of a simulated body fluid with fluorine ions, immersed in a constant-temperature shaking table, washed with deionized water, and dried to obtain the tooth appliance with a composite coating composed of polydopamine and fluorapatite and loaded with minocycline. The tooth appliance with the modified coating has excellent antibacterial performance in a simulated oral environment, and can reduce the adhesion amount of bacterial biofilm and inhibit the proliferation of bacterial biofilm.

Description

Technical Field

[0001] This invention belongs to the field of orthodontic technology, and particularly relates to an orthodontic appliance with a surface-modified antibacterial composite coating and its preparation method. Background Technology

[0002] Fixed orthodontic appliances provide a large surface area for plaque adhesion, and their irregular shape makes it difficult for patients to perform thorough oral hygiene. They also hinder the self-cleaning function of saliva, tongue, cheeks, and lips, resulting in a significant increase in the number of pathogenic bacteria in the oral cavity, which in turn leads to bacterial complications such as enamel demineralization and periodontal inflammation.

[0003] Common methods for controlling plaque during orthodontic treatment include brushing teeth, periodontal cleaning, chlorhexidine mouthwash, and using fluoride toothpaste. However, these methods are limited by factors such as the patient's cooperation and the maintenance of drug concentration, making it difficult to achieve lasting plaque control.

[0004] In recent years, much research has focused on adding nano-silver, nano-titanium dioxide, and chlorhexidine as releaseable antibacterial components to orthodontic adhesives. However, maintaining the long-term stability of the bond strength after adding these antibacterial agents to the adhesive is a major problem that needs to be solved. In addition, the adhesive is only present at the interface between the bracket base and the enamel surface, which limits its antibacterial effect.

[0005] Currently, using antibacterial coatings to modify the surface of orthodontic brackets is one of the effective strategies for addressing plaque adhesion. Commonly used materials for antibacterial coatings on orthodontic appliance surfaces include metal ions, titanium dioxide, and chitosan. Although these coatings have shown excellent effects in improving the antibacterial properties of fixed orthodontic appliances, antibiotics remain the primary antibacterial agents. Topical application of antibiotics in the oral cavity is a very routine treatment method, which can reduce adverse reactions and the incidence of drug resistance. In dentistry, numerous studies have demonstrated that antibiotic-loaded coatings can be used to modify implants, indicating that antibiotic-loaded coatings can be applied to address the problem of bacterial growth in the oral cavity. Therefore, they can be used to modify the surface of fixed orthodontic appliances to impart certain antibacterial properties.

[0006] Polydopamine can be polymerized to form polydopamine films on various substrates. Studies have shown that trypsin containing amino groups, bone morphogenetic proteins, bovine serum albumin, and various antibiotic bioactive substances can be incorporated into the surface of the formed polydopamine film, thereby functionalizing and modifying the surface. Therefore, polydopamine coatings are widely used in the surface modification of biomedical materials, but their application to the surface of fixed orthodontic appliances requires further investigation. Polydopamine can combine with the amino groups in the minocycline structure to form minocycline-loaded polydopamine films, which, when applied to the surface of fixed orthodontic appliances, impart antibacterial properties.

[0007] Enamel demineralization is a common complication during orthodontic treatment, affecting tooth health and the final treatment outcome. Hydroxyapatite, similar in composition to human bone tissue, exhibits good bioactivity and can induce bone growth, making it widely used clinically. Fluoroapatite combines the advantages of hydroxyapatite and fluorine; its fluorine content promotes cell regeneration and proliferation, accelerates hard tissue mineralization, and shows great promise in preventing enamel demineralization. Previous studies have used fluoride to modify adhesives to prevent enamel demineralization; however, as the fluoride is continuously released, the strength of the adhesive is affected, potentially leading to bracket detachment and impacting treatment effectiveness. Summary of the Invention

[0008] To overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a dental appliance with a surface-modified antibacterial composite coating and its preparation method.

[0009] This invention is achieved by a method for preparing a dental orthodontic appliance with a surface-modified antibacterial composite coating, the method comprising the following steps:

[0010] (1) Preheat the Tris·HCl solution to 60±2℃, add minocycline hydrochloride to the solution, adjust the pH of the solution to 8.5, add dopamine hydrochloride to the solution to obtain a mixed solution; place the pretreated orthodontic appliance in the mixed solution, soak and react for 90±5 min under stirring, take it out, wash and dry it to obtain an orthodontic appliance with a surface modified with minocycline loaded with polydopamine coating;

[0011] (2) The modified orthodontic appliance in step (1) is placed in 1.5 times the amount of simulated body fluid with introduced fluoride ions and soaked in a constant temperature shaker at 37°C for 2 days. The simulated body fluid is replaced every 24±1 hours. The appliance is rinsed and dried with deionized water to obtain an orthodontic appliance with a composite coating of minocycline loaded on the surface. The composite coating is composed of polydopamine and fluorapatite.

[0012] Preferably, in step (1), the pretreatment of the orthodontic appliance is as follows: the surface of the orthodontic appliance is polished in sequence with silicon carbide sandpaper through 80 grit, 240 grit, 400 grit, 600 grit, 800 grit, 1000 grit, 1500 grit and 2000 grit, and then ultrasonically rinsed in acetone, anhydrous ethanol and deionized water for 20 minutes respectively, and then dried.

[0013] Preferably, in step (1), the volume-to-mass ratio of the Tris·HCl solution, minocycline hydrochloride, and dopamine hydrochloride is 1L:5g:2g, wherein the concentration of the Tris·HCl solution is 0.1mM.

[0014] The present invention further discloses a dental appliance with a surface-modified antibacterial composite coating prepared by the above method.

[0015] Fixed orthodontic appliances provide a large surface area for plaque adhesion, and their irregular shape makes thorough oral hygiene difficult for patients. They also hinder the self-cleaning function of saliva, tongue, cheeks, and lips, leading to a significant increase in pathogenic bacteria in the oral cavity and consequently causing bacteria-related complications such as enamel demineralization and periodontal inflammation. However, traditional interventions such as brushing and fluoride use largely depend on good patient compliance, making it difficult to guarantee lasting results. To overcome the shortcomings of existing technologies, this invention provides an orthodontic appliance with a surface-modified antibacterial composite coating and its preparation method. This invention obtains an orthodontic appliance with a surface-modified polydopamine coating loaded with minocycline through a heated water bath rotation method, and then obtains an orthodontic appliance with a surface-modified composite coating loaded with minocycline through a biomimetic mineralization method. This composite coating is composed of polydopamine and fluorapatite.

[0016] In this invention, by loading antibiotics into a composite coating, the dosage can be significantly reduced, greatly lowering the incidence of bacterial resistance. Minocycline, when applied topically in the oral cavity, exhibits highly effective and long-lasting antibacterial and anti-inflammatory effects, rarely leading to resistance, and is a commonly used antibiotic in clinical dentistry. The amino groups in the minocycline structure can covalently bind to polydopamine, leveraging polydopamine's excellent adhesion to form an antibacterial coating on the substrate surface. Simultaneously, polydopamine provides a mineral deposition platform, allowing for the further synthesis of hydroxyapatite in simulated body fluids via a biomimetic mineralization method. Hydroxyapatite has good biocompatibility, and the addition of fluorine can accelerate the mineralization of hard tissues, preventing tooth decay and thus endowing the coating with a remineralization-promoting effect. Therefore, this invention, by directly modifying the surface of the orthodontic appliance with a coating possessing antibacterial and remineralizing properties, reduces bacterial adhesion and proliferation on the appliance surface. This not only prevents plaque adhesion problems but also provides a certain therapeutic effect on existing enamel demineralization; while the bond strength between the bracket base and the tooth surface remains unaffected.

[0017] Furthermore, in this invention, the heated water bath rotation method and the biomimetic mineralization method are both relatively simple and economical methods. A uniform coating is prepared on the surface of the orthodontic appliance, and the friction performance of the orthodontic appliance is improved by modifying the coating, so as to improve the orthodontic efficiency.

[0018] In this invention, the key technology lies in determining the optimal coating synthesis reaction time. Since the coating synthesis reaction time is related to the effective components (minocycline and fluorohydroxyapatite) contained in the coating, their content is a crucial factor in the antibacterial and remineralization effects of the orthodontic appliance. Furthermore, the physicochemical properties of the orthodontic appliance surface are also affected by the coating synthesis reaction time, and these properties determine the appliance's mechanical properties, thus affecting the transmission and expression of corrective force, and consequently, the final orthodontic effect. Therefore, this technology, by preparing minocycline-polydopamine-loaded coatings with different reaction times, ultimately determined a synthesis reaction time of 90 minutes.

[0019] Compared with the shortcomings and deficiencies of existing technologies, the present invention has the following beneficial effects:

[0020] (1) The present invention prepares a coating with antibacterial and remineralization effects by heating water bath rotation and biomimetic mineralization method, which is simple and economical;

[0021] (2) The orthodontic appliance modified with the coating of the present invention has excellent antibacterial properties in a simulated oral environment, which can reduce the amount of bacterial biofilm adhesion and inhibit the proliferation of bacterial biofilm.

[0022] (3) In a simulated oral environment, the sliding friction between the modified bracket groove and the archwire is significantly reduced, the resistance to tooth movement is reduced, and the orthodontic efficiency can be improved.

[0023] (4) The orthodontic appliance with the modified coating of the present invention has no cytotoxicity or hemolytic effect, has good in vitro biological safety, and promotes the remineralization of demineralized enamel in a simulated oral environment. Attached Figure Description

[0024] Figure 1 These are scanning electron microscope (SEM) images of the surface morphology of SS-PDA / MNO-FHA formed at different reaction times. A represents the control group without modification; B represents the group modified with PDA / MNO coating for 90 min (scale bar: 100 μm); C represents the group modified with PDA / MNO-FHA coating for 90 min (scale bar: 5 μm), showing polydopamine spherical particles; D represents the group modified with PDA / MNO-FHA coating for 90 min (scale bar: 100 μm); and E represents the group modified with PDA / MNO-FHA coating for 90 min (scale bar: 5 μm), showing fluorapatite particles in a cubic shape.

[0025] Figure 2 These are XPS full spectra of SS-PDA / MNO-FHA surfaces at different reaction times;

[0026] Figure 3The frictional force between the PDA / MNO-FHA modified tray and the stainless steel bow wire at different reaction times; where A is the maximum static frictional force in the dry state; B is the sliding frictional force in the dry state; C is the maximum static frictional force in the wet state; and D is the sliding frictional force in the wet state (* indicates P < 0.05 compared with the control group, ** indicates P < 0.01 compared with the control group).

[0027] Figure 4 The antibacterial properties of trays modified with PDA / MNO-FHA coatings at different reaction times after 14 days of soaking in artificial saliva are shown. A represents the WST-8 absorbance value of trays modified with PDA / MNO-FHA coatings at different reaction times after 14 days of soaking in artificial saliva and co-culturing with *Streptococcus mutans*; B represents the antibacterial rate against *Streptococcus mutans*; C represents the WST-8 absorbance value of trays modified with PDA / MNO-FHA coatings at different reaction times after 14 days of soaking in artificial saliva and co-culturing with *Escherichia coli*; D represents the antibacterial rate against *Escherichia coli*. (* indicates P < 0.05 compared to the control group, ** indicates P < 0.01 compared to the control group).

[0028] Figure 5 The results are obtained by diluting and coating the tray with PDA / MNO-FHA coating modified with rinsing solution at different reaction times on a plate.

[0029] Figure 6 These are the results of live and dead staining of Streptococcus mutans biofilms on the surface of SS-PDA / MNO-FHA at different reaction times; where A is the control group without coating modification; B to F are the PDA / MNO-FHA coated modification groups at 10 min, 30 min, 90 min, 4 h, and 12 h, respectively.

[0030] Figure 7 These are the results of live and dead staining of Escherichia coli biofilm on the surface of SS-PDA / MNO-FHA at different reaction times; where A is the control group without coating modification; B to F are the PDA / MNO-FHA coated modification groups at 10 min, 30 min, 90 min, 4 h, and 12 h, respectively.

[0031] Figure 8 The microhardness of enamel sections before and after artificial demineralization is: A represents the surface hardness before artificial demineralization; B represents the surface hardness after artificial demineralization; (* indicates P < 0.05 compared to the control group, ** indicates P < 0.01 compared to the control group) C represents the change before and after demineralization (* indicates P < 0.05 compared to the original demineralization, ** indicates P < 0.01 compared to the original demineralization);

[0032] Figure 9The microhardness of the enamel section after remineralization is: A represents the microhardness after remineralization (* indicates P < 0.05 compared to the control group, ** indicates P < 0.01 compared to the control group); B represents the change before and after remineralization (* indicates P < 0.05 compared to before remineralization, ** indicates P < 0.01 compared to before remineralization). Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] I. Fabrication of Orthodontic Appliances with Surface-Modified Composite Coatings Loaded with Minocycline (MNO)

[0035] (1) The surface of the orthodontic appliance (bracket or archwire) is polished in sequence with silicon carbide sandpaper through 80 grit, 240 grit, 400 grit, 600 grit, 800 grit, 1000 grit, 1500 grit and 2000 grit. Then, it is ultrasonically rinsed in acetone, anhydrous ethanol and deionized water for 20 minutes respectively. After drying, the pretreated orthodontic appliance SS is obtained.

[0036] Preheat 1L of Tris·HCl solution to 60±2℃, add 5g of minocycline hydrochloride to the solution, adjust the pH of the solution to 8.5, add 2g of dopamine hydrochloride to the solution to obtain a mixed solution; place the pretreated orthodontic appliance in the mixed solution and soak it for 90±5min under magnetic stirring at 300r / min, remove it, wash it with phosphate buffer solution (PBS solution), and dry it at room temperature to obtain a orthodontic appliance with a surface modified polydopamine-coated PDA loaded with minocycline MNO.

[0037] (2) Prepare the following components as shown in Table 1 according to 1L of “1.5 times simulated body fluid with fluoride ions introduced”.

[0038] Table 1. 1.5x simulated body fluid preparations with the introduction of fluoride ions

[0039]

[0040]

[0041] The solution was prepared in a 37°C water bath environment. The components were added in the order from top to bottom in Table 1. After adding MgCl2·6H2O, the pH of the solution was adjusted to 6.5-7 with HCl. After all the components were dissolved, the pH of the solution was finally adjusted to about 7.4 with Tris to obtain a 1.5 times simulated body fluid with introduced fluoride ions.

[0042] The orthodontic appliance with a polydopamine-coated PDA surface modified with minocycline (MNO) in step (1) was placed in the above-mentioned simulated body fluid and soaked in a constant temperature shaker at 37°C for 2 days. The simulated body fluid was replaced every 24±1 hours. The appliance was rinsed with deionized water and dried to obtain an orthodontic appliance with a composite coating surface modified with minocycline (MNO). The composite coating is composed of polydopamine PDA and fluorapatite (FHA).

[0043] II. Performance Testing

[0044] 1. Scanning electron microscopy

[0045] The surface morphology of the coated stainless steel sheets was observed using SEM. Each sample was sputter-coated with gold for 20 seconds before observation. The results are shown in the figure. Figure 1 As shown, Figure A is the control group without modified coating (i.e., the orthodontic appliance SS in step (1) of Example 1); Figure B is the 90min PDA / MNO coating modified group (the orthodontic appliance with a surface-modified polydopamine-coated PDA loaded with minocycline MNO obtained by the method described in step (1) of Example 1), with a scale bar of 100 μm; Figure C is the 90min PDA / MNO coating modified group (i.e., the orthodontic appliance with a surface-modified polydopamine-coated PDA loaded with minocycline MNO prepared in step (1) of Example 1), with a scale bar of 5 μm, where polydopamine spherical particles are visible; Figure D is the 90min PDA / MNO-FHA coating modified group (i.e., the orthodontic appliance with a surface-modified composite coating loaded with minocycline MNO prepared in step (2) of Example 1), with a scale bar of 100 μm; Figure E is the 90min PDA / MNO-FHA coating modified group, with a scale bar of 5 μm, where fluorapatite particles are cubic.

[0046] 2. XPS Analysis Test

[0047] The XPS analysis and testing operation voltage was 15kV, and the emission current was 15mA. Three measurements were taken for each coated stainless steel surface. The results are as follows: Figure 2 As shown, the uncoated stainless steel surface exhibits C1s, O 1s, Fe 2p, Cr 2p, and Ni 2p peaks. The surface modified with a minocycline-loaded polydopamine-fluoroapatite coating shows N1s, F 1s, and Ca 2p peaks. Further semi-quantitative analysis yields the results shown in Table 1. The uncoated stainless steel surface mainly contains C, O, Fe elements, and small amounts of Cr and Ni elements. After modification with a minocycline-loaded polydopamine coating, N element can be detected. After biomimetic mineralization using simulated body fluids with the introduction of fluoride ions, F and Ca elements originating from the fluorapatite coating are detected on the sample surface.

[0048] Table 1. Percentage of major elements on the surface of SS-PDA / MNO-FHA after 90 min

[0049]

[0050] 3. Friction properties

[0051] Experimental method: The frictional force between the brackets and the 0.019×0.025 inch stainless steel archwire of the experimental group (10min PDA / MNO-FHA, 30min PDA / MNO-FHA, 90min PDA / MNO-FHA, 4h PDA / MNO-FHA, 12h PDA / MNO-FHA) and the control group SS (uncoated) under dry and wet conditions was measured on an EZ-Test series single-column electronic universal testing machine.

[0052] Measurement under dry conditions: Clean the archwire and bracket with 95% alcohol, and dry with an air gun for 30 seconds before use. Fix the archwire and force measuring device on the upper and lower clamps of the EZ-Test series single-column electronic universal testing machine. Adjust the archwire to be parallel to the center line of the groove and in light contact with the bottom surface of the groove. The same clinician uses a standardized ligation rubber band to ligate the archwire and bracket. Start the universal testing machine and move it at a speed of 5 mm / min for 2 minutes. The first peak value is taken as the maximum static friction force. After the archwire moves at a constant speed, the friction force is slightly less than the wavy shape of the first peak value. Read the friction force value every 2 mm for a total of 5 times, and take the average value of the 5 readings as the sliding friction force. Set up 3 parallel groups for repeated measurements for each group.

[0053] Measurement under moist conditions: Add 1 drop of artificial saliva to the groove of the bracket and repeat the above steps. Set up 3 parallel groups for repeated measurements for each group.

[0054] The results are as follows Figure 3 As shown. In the dry state, compared with the unmodified tray, there were no statistically significant differences in maximum static friction and sliding friction between the tray and the archwire in each reaction time group. After adding artificial saliva into the groove, there were no statistically significant differences in maximum static friction between the tray and the archwire in each group, but the sliding friction between the SS-PDA / MNO-FHA modified tray and the stainless steel archwire was significantly lower than that between the unmodified tray and the stainless steel archwire, and the difference was statistically significant.

[0055] 4. Antibacterial properties

[0056] (1) Using unmodified trays as controls, after UV sterilization of both sides of each group of modified trays for 2 hours, they were placed into 24-well plates with sterile forceps and coated with artificial saliva filtered through a 0.22 μm filter at 37°C for 14 days. After the artificial saliva was removed, the trays were rinsed 3 times with PBS. The trays were then removed and placed in new 24-well plates. 10 μL of bacterial suspension and 1 mL of corresponding liquid culture medium were added to each well. The plates were incubated in a 37°C bacterial incubator for 24 hours. After the bacterial suspension was removed, the plates were rinsed 3 times with PBS. 100 μL of the rinse solution from each group was collected into a 96-well plate. WST-8 reagent was added at a ratio of 1:10 to WST-8 reagent and bacterial suspension. The plates were incubated in a 37°C incubator for 1 hour. With PBS as the background, the absorbance of each group at 450 nm was measured using a full-wavelength microplate reader. Each experimental group had three parallel samples, and each sample was measured three times. The antibacterial rates of the coated grooves at each reaction time against Streptococcus mutans and Escherichia coli were calculated using the following formula, and the results are as follows: Figure 4 As shown.

[0057] Depend on Figure 4 It can be seen that after soaking in artificial saliva for 14 days, the coated trays have good antibacterial properties against Streptococcus mutans and Escherichia coli, and the trays coated with PDA / MNO-FHA showed the best antibacterial performance after 90 minutes.

[0058] Collect 100 μL of each group of rinsing fluid and dilute 10. 3 After doubling, take 100 μL and add it dropwise to the surface of the corresponding solid culture medium, spread it evenly, and incubate it in a constant temperature incubator for 24 hours. Then, take a picture and count the colonies. The results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the number of bacterial colonies in the rinsing solution of the brackets after coating modification is significantly reduced, proving that the coated brackets can exert good antibacterial properties and have a certain degree of stability in the simulated oral environment.

[0059] (2) After coating each group of samples with artificial saliva for 24 hours, rinsed three times with PBS, and incubated with 1 mL of bacterial suspension at 37°C and 5% CO2 for 24 hours, the culture medium was replaced with sterile medium and cultured for another 7 days. The medium was changed every 48 hours. After culturing for a total of 7 days, the samples were rinsed twice with PBS, stained with LIVE / DEAD reagent for fluorescence, and the biofilm was observed using a focused laser scanning microscope. The results are as follows: Figure 6 , Figure 7 As shown.

[0060] Depend on Figure 6 , Figure 7 It can be seen that the total amount of bacterial biofilm on the surface of each group of samples after modification was reduced compared with the control group without modification.

[0061] 2. Remineralization

[0062] Freshly extracted bovine incisors were collected. Using a low-speed precision cutting machine, the central enamel of the labial surface was selected and cut into thin slices of 7mm × 7mm × 2mm. These slices were then polished sequentially with silicon carbide sandpaper and polished with a slow-speed handpiece using polishing compound. The enamel slices were then placed in an artificial demineralization solution and immersed at 37℃ for 3 days, changing the solution daily. After removal, the slices were ultrasonically cleaned with deionized water for 20 minutes and dried at room temperature. The demineralized enamel slices were then immersed in artificial saliva along with pure stainless steel (SS) slices, and in solutions of 10 min SS-PDA / MNO-FHA, 30 min SS-PDA / MNO-FHA, 90 min SS-PDA / MNO-FHA, 4 h SS-PDA / MNO-FHA, and 12 h SS-PDA / MNO-FHA. These solutions were placed in a 37℃ incubator for 14 days. After 14 days, the slices were removed, ultrasonically cleaned with deionized water for 20 minutes, and dried at room temperature. The microhardness of enamel sections from the experimental and control groups was measured using a microhardness tester before and after demineralization and after remineralization. The sample was placed on the testing stage, and three points were selected. A vertical load of 200g was applied for 10 seconds, and the average value of the three measurements was taken as the hardness value of the enamel section. Figure 8 , Figure 9 As shown.

[0063] Depend on Figure 8 It can be seen that, before demineralization, there was no statistically significant difference in the surface microhardness of the enamel sections among the different groups. Figure 8 A) After soaking in artificial demineralization solution for 3 days, there was no statistically significant difference in the surface microhardness of enamel sections among the different groups. Figure 8 B), but compared with before demineralization, the microhardness of the glaze surface decreased significantly ( Figure 8 C) indicates that an artificial enamel demineralization model has been successfully established.

[0064] Depend on Figure 9 It was found that after immersing orthodontic appliances modified with PDA / MNO-FHA coatings at different reaction times for 14 days at a constant temperature, the surface microhardness values ​​of the enamel sections in the 90min, 4h, and 12h groups were significantly higher than those in the blank control group, the 10min group, and the 30min group. Figure 9 A), and compared to after demineralization, the surface microhardness increased, with a statistically significant difference. Figure 9 B). The microhardness value can reflect the degree of mineralization of tooth tissue.

[0065] The above results indicate that the PDA / MNO-FHA coating promotes the remineralization of demineralized glazes.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a dental appliance with a surface-modified antibacterial composite coating, characterized in that, The method includes the following steps: (1) Preheat the Tris·HCl solution to 60±2℃, add minocycline hydrochloride to the solution, adjust the pH of the solution to 8.5, add dopamine hydrochloride to the solution to obtain a mixed solution; place the pretreated orthodontic appliance in the mixed solution, soak and react for 90±5 min under stirring, take it out, wash and dry it to obtain an orthodontic appliance with a surface modified with minocycline loaded with polydopamine coating; (2) The modified orthodontic appliance in step (1) is placed in 1.5 times the amount of simulated body fluid with introduced fluoride ions and soaked in a constant temperature shaker at 37°C for 2 days. The simulated body fluid is replaced every 24±1 hours. The appliance is rinsed and dried with deionized water to obtain an orthodontic appliance with a composite coating of minocycline loaded on the surface. The composite coating is composed of polydopamine and fluorapatite.

2. The method as described in claim 1, characterized in that, In step (1), the pretreatment of the orthodontic appliance is as follows: the surface of the orthodontic appliance is polished in sequence with silicon carbide sandpaper through 80 grit, 240 grit, 400 grit, 600 grit, 800 grit, 1000 grit, 1500 grit and 2000 grit, and then ultrasonically rinsed in acetone, anhydrous ethanol and deionized water for 20 minutes respectively, and then dried.

3. The method as described in claim 1, characterized in that, In step (1), the volume-to-mass ratio of the Tris·HCl solution, minocycline hydrochloride, and dopamine hydrochloride is 1L:5g:2g, wherein the concentration of the Tris·HCl solution is 0.1mM.

4. A dental appliance with a surface-modified antibacterial composite coating prepared by the method according to any one of claims 1 to 3.

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