Graphene oxide composite nanocoating, its application and modified dental metal material

Abstract

The application belongs to the technical field of nanomaterials, and particularly relates to a graphene oxide composite nanocoating, application thereof and modified dental metal material. The obtained graphene oxide composite nanocoating overcomes the problem of easy agglomeration of GO alone, has the advantages of long-term antibacterial property, strong corrosion resistance, low toxicity, good remineralization effect on dental enamel, reduced occurrence of dental demineralization and dental caries, effectively reduced friction between dental metal materials, especially between metal materials for orthodontic treatment, is conducive to the sliding between arch wires and bracket grooves in the orthodontic process, and further conducive to improving the efficiency of aligning and flattening the dental arch in orthodontic treatment and shortening the treatment course. In addition, the application has the characteristics of simple operation, low cost and strong controllability, and provides a simple and universal strategy for preparing dental metal materials with long-term antibacterial property, corrosion resistance, low toxicity, good remineralization effect and low friction.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology. More specifically, it relates to a graphene oxide composite nanocoating, its applications, and its modification of dental metal materials. Background Technology

[0002] The oral cavity is a complex microecological and electrochemical environment inhabited by a variety of microorganisms. Dental metal materials have complex structures; taking orthodontic fixed appliances as an example, during an average orthodontic treatment period of more than two years, bacteria easily attach and colonize, easily causing iatrogenic enamel demineralization, caries, and even a high incidence of periodontal disease. Furthermore, dental materials can react chemically with components in the oral environment, leading to corrosion and damage of the dental metal materials, metal ion release, and even systemic toxicity.

[0003] To address iatrogenic issues arising from dental metal materials during treatment, modification methods such as metal surface treatment can be employed to improve their clinical applications. As a novel carbon nanomaterial, graphene and its derivative, graphene oxide (GO), possess excellent antibacterial, biocompatibility, and corrosion resistance properties. However, due to the hydrogen bonding and π-π bond interactions of GO, it exhibits a close-packed structure, leading to agglomeration and uneven distribution in pure GO coatings, thus affecting their anti-corrosion and long-term antibacterial properties. To solve the GO agglomeration problem and achieve better dispersibility and homogeneity in surface coating preparation, modifying GO with inorganic nanomaterials is a simple and effective method. For example, Chinese patent application CN113663131A discloses a layer-by-layer assembly structure design that uses nano-zinc oxide and graphene oxide as a combined antibacterial agent to prepare a GO-ZnO composite nano-coating on the implant surface. First, a ZnO coating is prepared on the implant surface, and then a GO coating is superimposed on it to obtain a composite nanomaterial with both antibacterial and corrosion-resistant properties. However, since ZnO and GO are prepared separately, they cannot exert a highly efficient physical barrier effect, which ultimately affects the anti-corrosion performance and long-term antibacterial performance of the composite coating. Furthermore, since the composite nano-coating is designed to improve the performance of implants such as artificial bone substitutes, it is impossible to confirm how it improves the performance of dental metal materials. For example, Chinese patent application CN103734188A discloses a method for preparing zinc oxide-graphene oxide composite nanomaterials using soluble zinc ions as the zinc source, along with graphene oxide and alkaline solution as reactants. The resulting zinc oxide-graphene oxide composite nanomaterials exhibit highly efficient antibacterial capabilities at concentrations of 2.5–10 μg / mL. However, when the concentration of this composite nanomaterial reaches 50 μg / mL, it significantly impairs the viability of normal cells (reducing it to below 40%). When applied to biomaterials, there are strict concentration limitations. At lower concentrations, a dense coating cannot be formed on the metal surface, affecting its performance. Furthermore, the effects of applying the aforementioned zinc oxide-graphene oxide composite nanomaterials to dental metal materials on the remineralization of tooth enamel and its impact on the friction of the material are currently unknown.

[0004] Therefore, in response to the above problems, there is an urgent need to find a dental metal material coating that is durable, antibacterial, corrosion-resistant, low in toxicity, has good remineralization effect, and low friction. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and deficiencies of existing dental metal materials, which mainly focus on improving short-term antibacterial and corrosion resistance, while neglecting their long-term antibacterial properties, remineralization effect on enamel, and influence on the friction of the material. This invention provides the application of graphene oxide composite nanocoatings in dental metal materials.

[0006] Another objective of this invention is to provide the application of graphene oxide composite nanocoatings in improving the performance of dental metal materials.

[0007] Another objective of this invention is to provide a graphene oxide composite nanocoating for dental metal materials that is durable, antibacterial, corrosion-resistant, low in toxicity, has good remineralization effect, and low friction.

[0008] Another object of the present invention is to provide a modified dental metal material.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] This invention protects the application of graphene oxide composite nanocoatings in dental metal materials, wherein the graphene oxide composite nanocoating comprises graphene oxide (GO) and zinc oxide (ZnO).

[0011] This graphene oxide composite nanocoating has low toxicity, can achieve antibacterial properties at the source, and enables dental metal materials to withstand the corrosive environment of the oral cavity while maintaining excellent physicochemical properties. It has a good remineralization effect on tooth enamel, which can reduce tooth surface demineralization and tooth decay, and reduce the friction between dental metal materials.

[0012] Therefore, this invention also protects the application of the above-mentioned graphene oxide composite nanocoating in improving the performance of dental metal materials, the dental metal materials performance including antibacterial properties, resistance to corrosion in the oral environment, remineralization effect, and reduced friction.

[0013] Preferably, the dental metal material includes orthodontic metal materials.

[0014] Furthermore, the antibacterial properties refer to anti-caries bacteria, including Streptococcus mutans.

[0015] Furthermore, the orthodontic metal material includes orthodontic archwires and brackets.

[0016] Preferably, the dental metal material is selected from any one or more combinations of titanium, titanium-based alloys, stainless steel, cobalt-based alloys, magnesium alloys, gold, silver, platinum, gold alloys, silver alloys, and platinum alloys.

[0017] More preferably, the dental metal material is selected from titanium or titanium-based alloys.

[0018] Specifically, the graphene oxide composite nano-coating is formed by mixing graphene oxide solution and zinc oxide solution, obtaining composite nano-solution by hydrothermal method, and then dripping composite nano-solution onto the surface of dental metal material after adhesive pretreatment by drop casting method.

[0019] Preferably, the concentration of the composite nanosolution is 1.5–11 mg / mL. The concentration of the composite nanosolution is expressed as the total mass of GO and ZnO contained in 1 mL of the composite nanosolution being 1.5–11 mg.

[0020] Preferably, the mass ratio of graphene oxide to zinc oxide is (0.1-10):1.

[0021] More preferably, the mass ratio of graphene oxide to zinc oxide is (0.5-5):1.

[0022] Preferably, the adhesive is polydopamine (PDA), silane coupling agent APTES, or polydimethylsiloxane PMDS.

[0023] More preferably, the adhesive is PDA. Compared with existing adhesives, PDA adhesives have the following advantages: ① simple to manufacture, requiring no inducing agent; ② stable properties; ③ good biocompatibility, low cytotoxicity, and no pollution.

[0024] This invention also protects a graphene oxide composite nanocoating for dental metal materials. The graphene oxide composite coating is formed by mixing a graphene oxide solution and a zinc oxide solution, obtaining a composite nanosolution using a hydrothermal method, and then dripping the composite nanosolution onto the surface of the dental metal material after adhesive pretreatment using a drop casting method.

[0025] Through extensive experimentation, the applicant creatively discovered a method for preparing graphene oxide / zinc oxide composite nanosolution using a hydrothermal method. This nanosolution is then applied to the surface of dental metal materials pretreated with adhesive using a drop casting method to form a graphene oxide composite nanocoating. This graphene oxide composite nanocoating overcomes the problem of easy aggregation of individual graphene oxide (GO). It not only possesses advantages such as long-term antibacterial properties, strong corrosion resistance, and low toxicity, but also exhibits a good remineralization effect on tooth enamel, reducing tooth surface demineralization and caries. Furthermore, it reduces friction between dental metal materials, especially those used in orthodontics, facilitating the sliding between the archwire and bracket grooves during orthodontic treatment. This, in turn, improves the efficiency of orthodontic alignment and shortens the treatment duration.

[0026] Preferably, the concentration of the composite nanosolution is 1.5–11 mg / mL.

[0027] Preferably, the mass ratio of the graphene oxide solution to zinc oxide is (0.1-10):1.

[0028] Preferably, the mass ratio of the graphene oxide solution to zinc oxide is (0.5-5):1.

[0029] Preferably, the concentration of the adhesive solution used for pretreating dental metal materials is 0.5–4 mg / mL.

[0030] Specifically, the preparation method of the composite nano solution by hydrothermal method includes the following steps: graphene oxide powder and zinc oxide powder are added to water and dispersed fully to obtain graphene oxide dispersion and zinc oxide dispersion, respectively. The obtained graphene oxide dispersion and zinc oxide dispersion are mixed thoroughly and reacted fully at 50-60℃ to obtain the final product.

[0031] Preferably, the GO powder has a particle size of 0.5–5 μm and a thickness of 0.8–1.2 nm.

[0032] Preferably, the particle size of the ZnO powder is 100–2000 nm.

[0033] Specifically, the method for achieving sufficient dispersion is ultrasonic treatment, which lasts for 1–6 hours. The goal is to ensure complete ultrasonic dissolution of GO or ZnO, minimizing unnecessary ultrasonic treatment cycles. The ultrasonic treatment time is also related to the concentration of the mother liquor; a higher concentration requires a longer ultrasonic treatment time.

[0034] Furthermore, the thorough mixing takes 60–90 minutes, so that ZnO is evenly distributed on the surface of GO.

[0035] Preferably, the ultrasonic treatment time for preparing the GO dispersion is 3 hours.

[0036] Preferably, the ultrasonic treatment time for preparing the ZnO dispersion is 1 hour.

[0037] Specifically, the adhesive pretreatment of dental metal materials includes the following steps: dissolving the adhesive fully in water to prepare an adhesive solution, immersing the dental metal material fully in the obtained adhesive solution, washing, and drying.

[0038] Furthermore, the washing is performed using water.

[0039] Furthermore, the drying process involves drying at 50–80°C for 0.5–2 hours.

[0040] The present invention also protects a modified dental metal material, which is obtained by preparing the graphene oxide composite nanocoating on the surface of the dental metal material as a substrate.

[0041] As an feasible approach, the modified dental metal material is prepared by the following steps:

[0042] S1. Pre-treatment of dental metal materials;

[0043] S2. Treat the dental metal material obtained in step S1 with an adhesive;

[0044] S3. Prepare a graphene oxide composite nano-coating on the surface of the dental metal material obtained in step S2;

[0045] Specifically, in step S1, the pretreatment involves sanding the dental metal material with sandpaper, then slowly polishing it to a mirror finish using a polishing slurry with 0.3 μm particle size on a polishing machine. After polishing, the sample is ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 8–10 minutes. Then, the surface is treated with Kroll's liquid (8 μL nitric acid + 16 μL hydrofluoric acid + 10 mL water) for 1–10 minutes to remove the surface oxide film. Finally, the surface of the dental metal material is rinsed thoroughly with deionized water and dried with nitrogen gas for later use.

[0046] Furthermore, the content of nitric acid and hydrofluoric acid in Kroll's liquid can vary depending on the type of dental metal material and can be adjusted individually.

[0047] Preferably, the surface treatment time using Kroll's is 3 minutes. Different treatment times are used for different metal materials, with the goal of removing the surface oxide film, ensuring the integrity of the substrate surface as much as possible, and preventing surface unevenness caused by excessive treatment time.

[0048] Furthermore, the polishing is performed by sequentially polishing with 600# (i.e., 600 grit), 800#, 1000#, 1200# and 2000# sandpaper.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] This invention prepares a graphene oxide / zinc oxide (GO / ZnO) composite nanosolution via a hydrothermal method, and then uses a drop casting method to drop the composite nanosolution onto the surface of dental metal materials pretreated with adhesive to form a graphene oxide composite nanocoating (denoted as GO / ZnO coating). The resulting graphene oxide composite nanocoating overcomes the problem of easy aggregation of GO alone. It not only has the advantages of long-term antibacterial properties, strong corrosion resistance, and low toxicity, but also has a good remineralization effect on tooth enamel, which can reduce tooth surface demineralization and the occurrence of caries. It effectively reduces the friction between dental metal materials, especially the friction between orthodontic metal materials, which is beneficial to the sliding between the archwire and bracket groove during orthodontic treatment, thereby improving the efficiency of orthodontic treatment in aligning and leveling teeth and shortening the treatment course. In addition, this invention has the characteristics of simple operation, low cost, and strong controllability, providing a simple and universal strategy for preparing dental metal materials with long-lasting antibacterial activity, strong corrosion resistance, low toxicity, good remineralization effect, and low friction. Attached Figure Description

[0051] Figure 1This is a schematic diagram illustrating the effect of the orthodontic metal appliance PDA-0.5GO / ZnO-NT prepared in Example 1. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0053] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0054] ZnO: Zinc oxide nanorods, CAS number 1314-13-2.

[0055] Human gingival fibroblasts: CM-H240 Wuhan Pronosai Life Science Technology Co., Ltd.

[0056] Streptococcus mutans: BNCC336931 Beijing Beina Innovation Biotechnology Research Institute (Beina Biotechnology, BNCC)

[0057] Etching agent: 35% enamel-type enamel etching gel, sourced from Heraeus Gusa Dental Ltd.

[0058] Dopamine hydrochloride, CAS number 62-31-7, purity 98%. When dopamine hydrochloride dissolves in water, hydrogen chloride is converted into chloride ions and hydrogen ions. In a slightly alkaline environment, dopamine hydrochloride will self-polymerize to form polydopamine.

[0059] Graphene oxide (GO) was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd. in China. It is a powdered nanomaterial with a diameter of 0.5 μm produced by the modified Hummer process using potassium permanganate and concentrated sulfuric acid as raw materials.

[0060] Graphene oxide (GO) was added to deionized water in a certain proportion and ultrasonically treated for 3 hours to prepare a 10 mg / ml GO dispersion mother liquor. The obtained mother liquor was diluted to obtain 0.2 mg / ml, 1 mg / ml GO, 4 mg / ml and 10 mg / ml GO dispersions for later use.

[0061] ZnO was added to deionized water in a certain proportion and ultrasonically treated for 1 hour to prepare a 2 mg / ml ZnO dispersion mother liquor.

[0062] Example 1: Preparation of PDA-0.5GO / ZnO-NT orthodontic metal appliance with long-term antibacterial, corrosion-resistant, and low toxicity

[0063] (1) Pretreatment of orthodontic metal appliances: The nickel-titanium metal sheet (i.e., NiTi metal sheet (15mm×10mm×3mm), abbreviated as NT, used to simulate the nickel-titanium material in dental orthodontics) is polished with 600#, 800#, 1000#, 1200# and 2000# sandpaper in sequence. Then, the polished NT is slowly polished to a mirror effect on a polishing machine with polishing liquid with a particle size of 0.3μm. After polishing, the NT is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence for 8-10 minutes. Then, the surface is treated with Kroll's liquid (8μL nitric acid + 16μL hydrofluoric acid + 10mL water) for 3 minutes to remove the surface oxide film. Finally, the NT surface is rinsed with a large amount of deionized water and dried with nitrogen gas to make the NT surface clean and dry for use.

[0064] (2) PDA treatment: The NTs pretreated in step (1) were immersed in a mixed solution of 10mM Tris-HCl (0.25mL reagent + 24.75mL water) buffer and 2mg / mL dopamine hydrochloride (40mg PDA + 20mL water). The pH of the solution was slightly alkaline. After stirring magnetically at 25℃ for 1h, the solution was rinsed with deionized water and dried continuously at 60℃ for 1h to obtain NTs treated with polydopamine (PDA).

[0065] (3) Preparation of GO / ZnO composite nanocoating: 0.25 ml of 1 mg / ml GO dispersion and 0.25 ml of 2 mg / ml ZnO dispersion were mixed and magnetically stirred at 60℃ for 40 min using a hydrothermal method to obtain a composite nano solution; 0.25 mL of the GO / ZnO composite nano solution was drop-cast onto the NT surface coated with PDA and vacuum dried at 60℃ for 8 h to obtain a GO / ZnO composite nanocoating on the PDA-treated NT surface. The entire device was named PDA-0.5GO / ZnO-NT, and the effect diagram is shown in the figure. Figure 1 As shown.

[0066] Example 2: Preparation of PDA-2GO / ZnO-NT orthodontic metal appliance with long-term antibacterial, corrosion-resistant, and low toxicity

[0067] The difference from Example 1 is that in step (3), GO / ZnO composite nanosolution is prepared using 4 mg / ml GO dispersion and 2 mg / ml ZnO dispersion.

[0068] Other parameters and steps are the same as in Example 1.

[0069] The entire device is named PDA-2GO / ZnO-NT.

[0070] Example 3: Preparation of PDA-5GO / ZnO-NT orthodontic metal appliance with long-term antibacterial, corrosion-resistant, and low toxicity

[0071] The difference from Example 1 is that in step (3), GO / ZnO composite nanosolution is prepared using 10 mg / ml GO dispersion and 2 mg / ml ZnO dispersion.

[0072] Other parameters and steps are the same as in Example 1.

[0073] The entire device is named PDA-5GO / ZnO-NT.

[0074] Example 4: Preparation of PDA-10GO / ZnO-NT orthodontic metal appliance with long-term antibacterial, corrosion-resistant, and low toxicity

[0075] The difference from Example 1 is that in step (3), GO / ZnO composite nanosolution is prepared using 20 mg / ml GO dispersion and 2 mg / ml ZnO dispersion.

[0076] Other parameters and steps are the same as in Example 1.

[0077] The entire device is named PDA-10GO / ZnO-NT.

[0078] Comparative Example 1: Fabrication of the orthodontic metal appliance (NT)

[0079] (1) Pretreatment of metal orthodontic appliances: The NT was polished sequentially with 600#, 800#, 1000#, 1200# and 2000# sandpaper, and then polished slowly on a polishing machine with polishing liquid with a particle size of 0.3μm until a mirror effect was achieved. After polishing, the NT was ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water for 8-10 minutes. Then, the surface was treated with Kroll's liquid (8μL nitric acid + 16μL hydrofluoric acid + 10mL water) for 3 minutes to remove the surface oxide film. Finally, the NT surface was rinsed with a large amount of deionized water and dried with nitrogen gas to make the NT surface clean and dry. This was used as a blank group, and the resulting metal orthodontic appliances were named NT.

[0080] Comparative Example 2: Fabrication of the PDA-2GO-NT orthodontic metal appliance

[0081] The difference from Example 1 is that in step (3), only 2 mg / ml GO dispersion droplets were used to prepare the GO nano-coating on the PDA-treated NT surface.

[0082] Other parameters and steps are the same as in Example 1.

[0083] The entire device was named PDA-2GO-NT.

[0084] Comparative Example 3: Preparation of the orthodontic metal appliance PDA-ZnO-2GO-NT

[0085] The difference from Example 1 is that in step (3), a 2 mg / ml ZnO dispersion is drop-cast onto the NT surface after PDA treatment, and after drying, a ZnO coating is formed. Then, a 2 mg / ml GO dispersion is drop-cast onto the ZnO coating surface, and after drying, a GO coating is formed.

[0086] Other parameters and steps are the same as in Example 1.

[0087] The entire device is named PDA-ZnO-2GO-NT.

[0088] Comparative Example 4: Preparation of PDA-ZnO-0.1GO-NT orthodontic metal appliance

[0089] The difference from Example 1 is that in step (3), GO / ZnO composite nanosolution is prepared using 0.2 mg / ml GO dispersion and 2 mg / ml ZnO dispersion.

[0090] Other parameters and steps are the same as in Example 1.

[0091] The entire device is named PDA-ZnO-0.1GO-NT.

[0092] Long-term antibacterial performance test of the orthodontic metal appliances obtained in Example 1 and Comparative examples

[0093] The UV-sterilized orthodontic metal appliance specimens were placed in a 12-well plate with an inoculum concentration of 10. 8 One mL of a CFU / mL Streptococcus mutans suspension was added to a well plate and incubated at 37°C and 5% CO2 for 4 days. The biofilm sample after 4 days of incubation was transferred to a sterile vial containing 1 mL of cysteine ​​peptone water (CPW), and the biofilm on the titanium plate surface was collected using a vortex mixer. The obtained bacterial suspension was then sequentially irrigated with bacterial culture medium 10... -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 Dilute the bacterial suspension by taking 10 μL from each diluted group and dropping it onto blood agar plates. Repeat the process three times for each dilution. Incubate anaerobically at 37°C for 24–72 h. Then, use a colony counter to count the colonies and perform statistical analysis.

[0094] To investigate the long-term antibacterial stability of modified orthodontic metal appliances, the mechanical friction of brushing teeth was simulated when the appliance is worn in the mouth. The surface of the modified appliance was brushed with a small brush for 4 minutes using a force of 150g, 14 times and 28 times respectively, to simulate brushing teeth twice a day for 2 minutes each time. The antibacterial performance of the appliance was assessed after 14 and 28 days of wear, with day 0 simulating the antibacterial performance of the first use. Colony counts were measured again following the above antibacterial procedure to evaluate the long-term antibacterial stability of the appliance. The survival rate was used as the test index; a higher survival rate indicated poorer antibacterial performance. Survival rate = (Number of colonies measured / Number of colonies in Comparative Example 1) × 100%. The test results are shown in Table 1.

[0095] Table 1. Results of long-term antibacterial performance of orthodontic metal appliances

[0096]

[0097] As shown in Table 1, compared with the blank control group (Comparative Example 1), the metal orthodontic appliances prepared in Examples 1 to 4 all have good antibacterial properties. With the extension of wearing time, the antibacterial properties are further improved. The long-term antibacterial performance (28 days) is <60%, and there is a certain concentration dependence with the concentration of GO. That is, the higher the concentration of GO, the better the antibacterial performance. Among them, the composite coating prepared with high concentration of GO in Example 4 has good initial antibacterial properties. However, the composite nano-coating obtained by the high concentration of the composite liquid is too thick, and there will be a small amount of peeling in the later stage (28 days). The antibacterial effect will gradually deteriorate. The long-term antibacterial effect (28 days) is not as good as the mid-term antibacterial effect (14 days). The composite coating prepared with too low a concentration of GO in Comparative Example 4 showed poorer antibacterial performance than the coating obtained in the Example. The concentrations of ZnO and GO in the coating formed in the metal orthodontic appliance obtained in Comparative Example 3 were the same as those in Example 2, but the two formed coatings separately. Compared with Example 2, the initial antibacterial performance decreased, and the long-term antibacterial performance (28 days) decreased further, only 4.2% higher than the mid-term antibacterial performance (14 days). Compared with Example 2, the effective antibacterial component in Comparative Example 2 was only GO, and the simple GO was easy to peel off due to aggregation, resulting in poor long-term antibacterial effect.

[0098] Experimental Example 2: Biosafety Testing of Orthodontic Metal Appliances

[0099] The modified orthodontic metal appliance was placed in a 12-well plate. Human gingival fibroblasts (1.5 x 10⁻⁶) were then used. 5Cells were seeded onto the surface of the metal orthotics prepared in the examples and comparative examples. The culture medium was DMEM containing 10% fetal bovine serum and 1% penicillin-streptomycin. The blank culture medium without the orthotics was named the DMEM group. All cells were cultured at 37°C, 5% CO2 and 100% humidity for 24 h. Cell viability was detected using the CCK-8 assay kit according to the instructions. The closer the cell proliferation activity was to 100% (with the cell viability measured in the DMEM group as 100%), the closer the toxicity of the obtained material was to non-toxicity. The results are shown in Table 2.

[0100] Table 2 Biosafety Test Results

[0101]

[0102] As shown in the table, the CCK proliferation toxicity test indicates that the orthodontic metal appliances obtained in Examples 1 to 4 have good biocompatibility. Among them, the cell proliferation activity of the orthodontic metal appliances obtained in Examples 1 to 3 is >95%, and the cell proliferation activity of Example 4 is enhanced due to the increased GO concentration, but the cell proliferation activity is still >65%.

[0103] Test Example 3: Corrosion Resistance Test of Orthodontic Metal Appliances

[0104] The non-test surfaces of the modified orthodontic metal appliance were sealed with epoxy resin. A copper wire was connected to the back of the appliance. Using the test sample as the working electrode, a platinum sheet (Pt) as the auxiliary electrode, and a saturated calomel electrode (SCE) as the reference electrode, the appliance was connected to an electrochemical workstation. Before testing, the appliance was degassed for 1 hour and then immersed in artificial saliva for 60 minutes to allow the surface to stabilize. The potentiodynamic polarization curve test was then performed, starting from -1000 mV at a scanning speed of 5 mV / s, with a scanning range of -1000 mV to +1000 mV. The electrochemical experiment was repeated 6 times or more under the same corrosion conditions, using a new corrosion solution and test sample each time, until the polarization curves essentially overlapped. The corrosion current was calculated, and the corrosion status was assessed based on the magnitude of the corrosion current. A smaller corrosion current (icorr) indicates better corrosion resistance. The measurement results are shown in Table 3.

[0105] Table 3. Determination of corrosion resistance effect

[0106] Orthodontic metal braces <![CDATA[Corrosion current (i corr) (l A / cm 2 )]]> Example 1: PDA-0.5GO / ZnO-NT 3.12±0.08 Example 2: PDA-2GO / ZnO-NT 2.55±0.11 Example 3: PDA-5GO / ZnO-NT 2.08±0.14 Example 4: PDA-10GO / ZnO-NT 2.78±0.12 Comparative Example 1NT 5.12±0.19 Comparative Example 2PDA-2GO-NT 4.47±0.21 Comparative Example 3PDA-ZnO-2GO-NT 3.62±0.09 Comparative Example 4PDA-0.1GO / ZnO-NT 4.38±0.13

[0107] As shown in Table 3, compared with Comparative Example 1, the corrosion resistance of the modified orthodontic appliances in Examples 1-4 increased with increasing GO concentration. At a GO concentration of 10 mg / ml, the concentration was relatively high, resulting in excessive coating thickness and insufficient adhesion. After a small amount of coating peeled off, the corrosion resistance did not further increase with increasing GO concentration but instead began to weaken, although it still exhibited good corrosion resistance. In Comparative Example 4, due to the low effective GO concentration, the corrosion resistance was not significantly different from the control group. In Comparative Example 2, because the GO coating was only applied to the PDA, GO agglomeration was inevitable, resulting in poor surface integrity and hindering corrosion resistance. Compared with Example 3, Comparative Example 3 showed weaker corrosion resistance, possibly due to uneven GO agglomeration in its surface coating.

[0108] Experimental Example 4: Analysis of the Effects of Orthodontic Metal Appliances on Enamel Demineralization

[0109] Extracted enamel blocks were collected, and an acid etching agent was applied to the labial enamel surface for 30 seconds. After rinsing with copious amounts of deionized water, the enamel was dried until the surface turned chalky white. The resulting demineralized enamel blocks were used for enamel remineralization experiments. The demineralized enamel blocks were then immersed in artificial saliva at 37°C for 6 hours along with modified orthodontic metal appliances. The immersed enamel blocks were collected and dried. The enamel blocks were fixed to the sample stage using double-sided carbon conductive adhesive for SEM, and then vacuum-sputtered with gold in an ion sputtering system. After coating, the surface morphology of all samples was observed under SEM (×1000). After SEM imaging, the calcium and phosphorus content on the enamel surface of each group of samples was measured using energy dispersive X-ray spectroscopy (regional scanning) to obtain energy dispersive spectral images. The calcium-to-phosphorus ratio was calculated based on the molar percentage of calcium and phosphorus. The results are shown in Table 4.

[0110] Table 4. Results of the determination of the effect of orthodontic metal appliances on enamel demineralization.

[0111] Orthodontic metal braces Calcium-to-phosphorus ratio (n=3) Example 1: PDA-0.5GO / ZnO-NT 1.840±0.045 Example 2: PDA-2GO / ZnO-NT 1.934±0.064 Example 3: PDA-5GO / ZnO-NT 2.163±0.036 Example 4: PDA-10GO / ZnO-NT 2.475±0.027 Comparative Example 1NT 1.556±0.040 Comparative Example 2PDA-2GO-NT 1.742±0.045 Comparative Example 3PDA-ZnO-2GO-NT 1.794±0.042 Comparative Example 4PDA-0.1GO / ZnO-NT 1.804±0.033

[0112] The calcium-to-phosphorus ratio values ​​obtained by SEM and EDS analysis showed that a higher calcium-to-phosphorus ratio indicates a better remineralization effect after demineralization. The results showed that, compared with Comparative Example 1, the orthodontic metal appliances obtained in Examples 1-4 had a better remineralization ability for tooth enamel, and the remineralization ability was significantly enhanced with the increase of GO concentration, with calcium-to-phosphorus ratios ≥1.84.

[0113] Test Example 5: Friction Resistance Test of Orthodontic Metal Appliances

[0114] The friction and wear performance of the prepared metal orthodontic appliances was tested using a UMT-2 micro-friction and wear testing machine to obtain their coefficient of friction (COF) and friction life values. The metal orthodontic appliances prepared in the examples and comparative examples were fixed on a sample stage. The sample stage reciprocated linearly, while the probe remained stationary, sliding in contact with the metal orthodontic appliance under a certain load condition. The reciprocating sliding speed and load parameters were adjusted according to experimental requirements. The friction value of the orthodontic metal orthodontic appliance was measured as a percentage of the measured coefficient of friction of each appliance to that of Comparative Example 1. A lower percentage value indicates a lower friction value. The measurement results are shown in Table 5.

[0115] Table 5. Friction Value Results of Orthodontic Metal Appliances

[0116]

[0117]

[0118] As can be seen from the results in Table 5, compared with the untreated orthodontic metal appliance (Comparative Example 1), the orthodontic metal appliances obtained in Examples 1-4 of this invention have lower friction values, which is beneficial for the sliding between the archwire and the bracket groove during orthodontic treatment, thereby improving the efficiency of orthodontic alignment and shortening the treatment time. In Comparative Example 4, due to the low GO concentration and uneven coating, the surface roughness and friction reduction were not significant.

[0119] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The application of graphene oxide composite nanocoatings in dental metal materials, characterized in that, The graphene oxide composite nanocoating comprises graphene oxide and zinc oxide; the graphene oxide composite nanocoating is formed by mixing graphene oxide dispersion and zinc oxide dispersion, obtaining composite nano solution by hydrothermal method, and then dropping composite nano solution onto the surface of dental metal material after adhesive pretreatment by drop casting method. The mass ratio of graphene oxide to zinc oxide is (0.5~5):1; The concentration of the composite nano solution is 1.5~6 mg / mL; The dental metal material is a metal material used in orthodontics. The metal materials used in orthodontics include orthodontic archwires and brackets; The method for preparing the composite nanosolution by hydrothermal method includes the following steps: graphene oxide powder and zinc oxide powder are added to water and dispersed thoroughly to obtain graphene oxide dispersion and zinc oxide dispersion, respectively. The obtained graphene oxide dispersion and zinc oxide dispersion are mixed thoroughly and reacted at 50~60 °C to obtain the final product.

2. The application of graphene oxide composite nanocoating in improving the performance of dental metal materials, characterized in that, The graphene oxide composite nanocoating comprises graphene oxide and zinc oxide; the graphene oxide composite nanocoating is formed by mixing graphene oxide dispersion and zinc oxide dispersion, obtaining composite nano solution by hydrothermal method, and then dropping composite nano solution onto the surface of dental metal material after adhesive pretreatment by drop casting method. The properties of the dental metal materials include antibacterial properties, resistance to corrosion in the oral environment, remineralization effect, and reduced friction. The mass ratio of graphene oxide to zinc oxide is (0.5~5):1; The concentration of the composite nano solution is 1.5~6 mg / mL; The dental metal material is a metal material used in orthodontics. The metal materials used in orthodontics include orthodontic archwires and brackets; The method for preparing the composite nanosolution by hydrothermal method includes the following steps: graphene oxide powder and zinc oxide powder are added to water and dispersed thoroughly to obtain graphene oxide dispersion and zinc oxide dispersion, respectively. The obtained graphene oxide dispersion and zinc oxide dispersion are mixed thoroughly and reacted at 50~60 °C to obtain the final product.

3. The application according to claim 1 or 2, characterized in that, The adhesive is polydopamine or silane coupling agent APTES.

4. A composite nanocoating for the surface of graphene oxide used in dental metal materials, characterized in that, The graphene oxide composite nanocoating is formed by mixing graphene oxide dispersion and zinc oxide dispersion, obtaining composite nano solution by hydrothermal method, and then dripping composite nano solution onto the surface of dental metal material after adhesive pretreatment by drop casting method. The mass ratio of graphene oxide to zinc oxide is (0.5~5):1; The concentration of the composite nano solution is 1.5~6 mg / mL; The dental metal material is a metal material used in orthodontics. The metal materials used in orthodontics include orthodontic archwires and brackets; The method for preparing the composite nanosolution by hydrothermal method includes the following steps: graphene oxide powder and zinc oxide powder are added to water and dispersed thoroughly to obtain graphene oxide dispersion and zinc oxide dispersion, respectively. The obtained graphene oxide dispersion and zinc oxide dispersion are mixed thoroughly and reacted at 50~60 °C to obtain the final product.

5. A modified dental metal material, characterized in that, The coating is obtained by preparing the graphene oxide composite nanocoating of claim 4 on the surface of a dental metal material as a substrate.

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