A tooth enamel repair material and preparation method thereof

Abstract

The present invention relates to a tooth enamel repair material and a preparation method thereof, belonging to the technical field of medical filling materials for tooth defects. The materials include F-HAp, APTES-ZrO2, an MPC-modified composite resin, 10-MDP, γ-MPS, a composite initiator, MPC and a dispersant; F-HAp is fluorine-doped enamel hydroxyapatite nanorods; APTES-ZrO2 is aminopropyltriethoxysilane-modified nano-zirconium oxide; and the MPC-modified composite resin is a 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer composite resin. The present invention adopts a special method to prepare the F-HAp, APTES-ZrO2 and MPC-modified composite resin, and compound them with other components in a certain proportion to obtain the tooth enamel repair material. The tooth enamel repair material has good adhesion, strength and biocompatibility, excellent anti-leakage performance, and improved safety and durability in use.

Description

Technical Field

[0001] The invention belongs to the technical field of medical filling materials for tooth defects, and particularly relates to a tooth enamel repair material and a preparation method thereof. Background Art

[0002] Tooth enamel, the hardest tissue in the human body, is primarily composed of nanorod-shaped hydroxyapatite crystals. These crystals are highly ordered, giving it excellent mechanical properties, allowing it to withstand the pressure of daily chewing and act as a buffer to protect the sensitive tissues within the teeth. However, tooth enamel faces the problem of defects caused by caries and trauma. Mature tooth enamel is a non-living tissue and, once damaged, is almost impossible to repair itself. This not only affects the aesthetic appearance of teeth but can also lead to more severe dental caries, tooth sensitivity, pulpitis, and other oral health issues, reducing patients' quality of life.

[0003] At present, metals, dental composite resins, ceramic materials, etc. are mainly used to fill and repair enamel defects in clinical practice. Composite resin is one of the commonly used restorative materials. It can be cured by light and bonded to the tooth surface. It has good aesthetic effects, its color can match that of natural teeth, and it has certain wear resistance. It is often used to fill the dental cavities of the front teeth where aesthetics are concerned. Glass ionomer cement is composed of glass ionomers and polyacrylic acid. It can release fluoride ions, which helps prevent caries, has little irritation to the dental pulp, and has good sealing properties. It is widely used in clinical practice for cavity fillings. Ceramic materials, such as zirconia ceramics and glass ceramics, have excellent aesthetic effects and wear resistance and can bond to the tooth surface.

[0004] However, these existing restorative materials have many limitations. On the one hand, their mechanical strength is relatively weak, their adhesion to teeth is poor, and they are easy to fall off during daily oral activities such as chewing, which affects the durability of the repair effect. On the other hand, the physical properties and chemical composition of these materials are different from those of natural human enamel, and there is a large gap in microbiological and mechanical properties. During use, secondary problems are prone to occur, such as microleakage leading to bacterial invasion and secondary caries; the thermal expansion coefficient of the restorative material is inconsistent with that of the enamel, which may cause the restoration to loosen or the surrounding tooth tissue to be damaged when the temperature changes. For a long time, the problem of microleakage at the bonding interface has been difficult to be effectively solved, which seriously restricts the quality and effect of enamel restoration. Therefore, the development of a restorative filling material that can highly simulate the structure and properties of natural enamel and has good adhesion, biocompatibility and long-term stability has become a key issue that needs to be urgently addressed in the field of oral medicine. Summary of the Invention

[0005] In order to improve the adhesion, biocompatibility, and long-term stability of enamel defect repair filling materials, the present invention provides a tooth enamel repair material and its preparation method, which prepares fluorine-doped enamel hydroxyapatite nanorods, aminopropyltriethoxysilane-modified nanozirconia, 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer composite resin, and compounded with 10-(2-methacryloyloxy) monodecyl phosphate, silane coupling agent KH-570, composite initiator and other ingredients to obtain the tooth enamel repair material, which has excellent adhesion, strength and biocompatibility, excellent anti-leakage, and improved safety and durability. The specific technical solution is as follows:

[0006] A tooth enamel restoration material comprises the following raw materials in parts by weight: 50 to 55 parts of F-HAp, 5 to 8 parts of APTES-ZrO2, 30 to 35 parts of MPC-modified composite resin, 3 to 5 parts of 10-MDP, 1 to 2 parts of γ-MPS, 0.5 to 1 part of composite initiator, 0.1 to 0.3 parts of MPC and 1 to 1.5 parts of dispersant; wherein, F-HAp is a fluorine-doped enamel hydroxyapatite nanorod with a diameter of 20 nm to 30 nm and a length of 100 nm to 200 nm; APTES-ZrO2 is a fluorine-doped enamel hydroxyapatite nanorod with a diameter of 20 nm to 30 nm and a length of 100 nm to 200 nm; rO2 is aminopropyltriethoxysilane modified nano-zirconia; MPC-modified composite resin is 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer composite resin; 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate; γ-MPS is silane coupling agent KH-570; the composite initiator is camphorquinone and 4-EDMAB in a mass ratio of 1:(1.8~2); MPC is 2-methacryloyloxyethyl phosphorylcholine; and the dispersant is ammonium polyacrylate.

[0007] Among the above raw materials, the preparation of F-HAp includes: dissolving 0.3M~0.35M Ca(NO3)2, 0.18M~0.20M (NH4)2HPO4, and 0.02M~0.03M NH4F in deionized water, and adjusting the pH to 8.8~9.2 with ammonia water; stirring and reacting at 175℃~185℃ for 48h~50h; centrifuging, washing the precipitate with deionized water, adding the precipitate to deionized water containing 2wt%~2.5wt% of silane coupling agent KH-570 with a mass 10 times~15 times of the precipitate, ultrasonically dispersing, centrifuging, and vacuum drying the solid to obtain F-HAp.

[0008] In the preparation of the above-mentioned F-HAp, centrifugation is performed at 8000 rpm to 10000 rpm for 10 to 15 minutes; the number of deionized water washings is 3 to 5 times; ultrasonic dispersion is performed at 300W to 350W and 35kHz to 40kHz for 30 to 40 minutes; and vacuum drying is performed at 60°C to 70°C to constant weight.

[0009] Among the above raw materials, the preparation of APTES-ZrO2 includes: heating nano-zirconia to 650℃~680℃ and sintering for 2h~2.5h; under nitrogen protection, vapor deposition of APTES vapor volume concentration of 10%~12% at 80℃~85℃ for 4h~4.5h, and coating APTES on the surface of the sintered nano-zirconia to obtain APTES-ZrO2.

[0010] In the preparation of the above-mentioned APTES-ZrO2, the heating rate is 2°C / min to 4°C / min; APTES is aminopropyltriethoxysilane.

[0011] Among the above raw materials, the preparation of the MPC-modified composite resin includes: preparing a base liquid according to the mass ratio of dimethacrylate urethane: methacrylate glycidyl elastomer: castor oil phosphate: MEHQ inhibitor: THF solvent = (22-25): (5-8): (1.3-1.5): (0.05-0.1): (70-80), then adding 0.8%-1.2% of 2-methacryloyloxyethyl phosphorylcholine monomer and 0.5%-0.8% of Perkadox 16 initiator by mass of the base liquid, stirring and reacting at 49°C-52°C for 6h-8h under nitrogen protection; after cooling, adding 0.8 times to 1 times the total volume of n-hexane containing 10%-15% volume of acetone, stirring, and precipitating the product, collecting the precipitate by filtration, washing with n-hexane, and vacuum drying to obtain the MPC-modified composite resin.

[0012] In the preparation of the above-mentioned MPC-modified composite resin, the filtration mesh size is 325 mesh; the number of n-hexane washings is 3 to 5 times; the vacuum drying is performed at 50° C. to 55° C. to constant weight; the mass concentration of the Perkadox 16 initiator is 50 wt %, and the solvent is THF solvent.

[0013] The method for preparing the above-mentioned tooth enamel repair material comprises the following steps:

[0014] S1: F-HAp, MPC-modified composite resin, MPC and composite initiator were mixed uniformly according to parts by mass to obtain a mixture A, and anhydrous ethanol was added to the mixture A and mixed uniformly to obtain a mixture B;

[0015] S2: Add APTES-ZrO2 to anhydrous ethanol with a mass of 4 to 5 times that of APTES-ZrO2, ultrasonically disperse for 15 to 20 minutes, add γ-MPS and ultrasonically disperse for 10 to 15 minutes, add dispersant and ultrasonically disperse for 5 to 8 minutes, add mixture B and 10-MDP in sequence, stir and mix evenly, adjust the viscosity, and vacuum treat to obtain the enamel restoration material.

[0016] In S1 of the above preparation method, the amount of anhydrous ethanol added is 10% to 15% by mass of the mixture A.

[0017] In S2 of the above preparation method, the power of ultrasonic dispersion is 200W to 250W; the speed of stirring and mixing is 200rpm to 300rpm; the viscosity is adjusted to 3000cP to 4000cP; and the time of vacuum treatment is 5min to 8min.

[0018] The enamel restoration material obtained by the above preparation method is used to fill the tooth defect or inject into the customized mold, and the enamel restoration material ... 2 ~400mW / cm 2 The material is cured by irradiating with blue light; the irradiation is divided into two times with an interval of 10s to 15s, and each irradiation is 20s to 30s.

[0019] The present invention provides a tooth enamel repair material and a preparation method thereof, which have the following beneficial effects:

[0020] 1. The present invention designs F-HAp by doping it with F and modifying it with silane. Fluoride ions replace some of the hydroxyl groups in hydroxyapatite to form a fluorapatite structure, which significantly improves the material's acid solubility resistance and inhibits the erosion of restorations and surrounding tooth tissues by acids produced by oral bacterial metabolism. At the same time, fluoride ions interfere with the activity of bacterial metabolic enzymes, inhibiting bacterial growth and biofilm formation. Fluorine doping makes the hydroxyapatite crystal structure denser and changes the lattice parameters, thereby improving the material's hardness, compressive strength, and wear resistance, making it closer to the mechanical properties of natural enamel. The released fluoride ions combine with calcium ions in the enamel to promote enamel remineralization, repair early demineralization, and enhance the overall caries resistance of teeth. The silane coupling agent forms an organic coating on the surface of F-HAp, establishing a strong chemical bond, significantly enhancing the interfacial bonding between the inorganic filler and the resin, and reducing interfacial voids and microleakage. Silane modification improves the surface properties of F-HAp, making it easier to disperse in the resin matrix, avoiding local mechanical defects caused by nanoparticle agglomeration, and ensuring uniform overall material performance. Silane coating can optimize the hydrophilicity of F-HAp, promote the wetting and adhesion of the material to tooth tissue, and further enhance the bonding effect.

[0021] Second, this invention employs APTES-modified ZrO2. After APTES modification, a silane coupling agent forms an organic-inorganic transition layer on the ZrO2 surface. This chemical bond (silicon-oxygen bonds and amino-resin crosslinking) connects the ZrO2 to the resin, significantly enhancing interfacial adhesion and reducing restoration shedding and microleakage caused by interfacial stress concentration. APTES modification modifies the hydrophilicity and charge properties of the ZrO2 surface, facilitating its dispersion within the resin matrix and preventing agglomeration, thereby improving the overall mechanical properties (such as strength and toughness) and stability of the material. By enhancing interfacial bonding, APTES-ZrO2 more effectively transfers stress to the resin matrix, leveraging the high strength of zirconia while mitigating interfacial fatigue damage caused by differences in rigidity, thereby extending the life of the restoration.

[0022] 3. During the preparation of MPC-modified composite resin, glycidyl methacrylate elastomer is added. The elastomer is flexible and can absorb impact energy during chewing, relieve stress concentration, reduce crack initiation and propagation caused by repeated stress on the restoration, and improve the material's fatigue resistance and service life. Conventional resins shrink during curing, which can easily lead to micro-leakage at the edges. The addition of elastomers can reduce the overall curing shrinkage rate, allowing the restorative material to better fit the tooth tissue, reducing gap formation, and lowering the risk of bacterial invasion and secondary caries. Elastomers can adjust the elastic modulus of the restorative material, reducing interfacial stress and wear caused by large differences in elastic modulus.

[0023] 4. Castor oil phosphate is added to the preparation of MPC-modified composite resin. Castor oil phosphate contains phosphate groups, which react chemically with the hydroxyl groups on the surface of tooth enamel to form chemical bonds, and cooperate with 10-MDP to further enhance the bonding strength between the restorative material and the tooth tissue, and reduce marginal microleakage. Castor oil phosphate can also improve the compatibility of dimethacrylate urethane and glycidyl methacrylate elastomers, promote grafting reactions and network interpenetration. As a plasticizer, castor oil phosphate can reduce the viscosity of the resin matrix and increase the fluidity of the material, making it easier to fill complex tooth cavities, ensuring that the restoration fits tightly with the tooth tissue, and improving the accuracy and tightness of the restoration. The phosphate structure has a certain antibacterial effect, inhibiting the attachment of bacteria to the surface of the restoration.

[0024] 5. MEHQ is added to the preparation of MPC-modified composite resins to inhibit polymerization. During composite resin preparation, MEHQ effectively inhibits monomer self-polymerization during storage and preparation, ensuring controllable reactions and stable material performance during clinical use. Failure to add MEHQ can lead to premature partial polymerization of monomers, disrupting the proper reaction. This can cause uncontrolled reaction of the initiator (Perkadox 16) during curing, resulting in internal defects and an uneven composite resin structure, uneven curing shrinkage, weakened bonding, and reduced material performance.

[0025] 6. The phosphorylcholine group in MPC has a similar structure to cell membrane phospholipids, which can reduce the immunogenicity of the material, reduce the inflammatory response of macrophages and lymphocytes, promote cell adhesion and growth, and improve the compatibility of the material with human tissue. The phosphorylcholine group has hydrophilic and charged properties, which interfere with the charge balance and physiological function of bacterial cell membranes, inhibit bacterial adhesion, colonization, and biofilm formation on the material surface, and significantly reduce the risk of infection after repair.

[0026] 7. In resin modification, MPC participates in the resin polymerization reaction after grafting, increases the cross-linking density, and improves the strength and toughness of the material; at the same time, its phosphate group forms a chemical bond with the tooth tissue, further enhancing the bonding performance.

[0027] 8. In the component mixing method of the present invention, F-HAp is first mixed with the MPC-modified composite resin, MPC, and a composite initiator to preferentially and evenly disperse the nanorod-shaped F-HAp in the resin matrix, preventing agglomeration caused by the subsequent addition of other components due to the complex system. APTES-ZrO2 is separately ultrasonically dispersed, and γ-MPS and a dispersant are added sequentially to ensure thorough dispersion and surface functionalization of the zirconium oxide particles, enhancing their bonding to the resin matrix. 10-MDP is added and viscosity is adjusted stepwise, introducing bonding functional groups late in the mixing process to prevent premature reaction that increases viscosity and affects material flowability and handling. Furthermore, a vacuum treatment is used to remove bubbles introduced during mixing, preventing the risk of air bubbles leading to decreased mechanical properties and microleakage. This step-by-step mixing allows each component to fully function (the silane coupling agent first reacts with the inorganic filler before cross-linking with the resin), ensuring stable chemical bonds between the inorganic filler and the resin, and between the restorative material and the tooth tissue, maximizing the material's adhesion, mechanical properties, and long-term stability. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0029] Example 1: A tooth enamel restoration material, comprising the following raw materials in parts by mass: 50 parts of F-HAp, 5 parts of APTES-ZrO2, 30 parts of MPC-modified composite resin, 3 parts of 10-MDP, 1 part of γ-MPS, 0.5 parts of composite initiator, 0.1 parts of MPC, and 1 part of dispersant; wherein, F-HAp is a fluorine-doped enamel-like hydroxyapatite nanorod with a diameter range of 20nm to 30nm and a length range of 100nm to 200nm; APTES-ZrO2 is an aminopropyl tris(III)-1,2-dimethylaminopropane-1,4-dihydro ... Ethoxysilane modified nanozirconia; MPC modified composite resin is a composite resin of 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer; 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate; γ-MPS is the silane coupling agent KH-570; the composite initiator is a mixture of camphorquinone and 4-EDMAB in a mass ratio of 1:1.8; MPC is 2-methacryloyloxyethyl phosphorylcholine; and the dispersant is ammonium polyacrylate.

[0030] The preparation of F-HAp includes: dissolving 0.3M Ca(NO3)2, 0.18M (NH4)2HPO4, and 0.02M NH4F in deionized water, and adjusting the pH to 8.8 with ammonia water; stirring and reacting at 175°C for 50 hours; centrifuging at 8000rpm for 15 minutes, washing the precipitate three times with deionized water, adding the precipitate to deionized water containing 2wt% of the silane coupling agent KH-570 with a mass 10 times that of the precipitate, ultrasonically dispersing at 300W and 35kHz for 40 minutes, centrifuging at 8000rpm for 15 minutes, and vacuum drying the solid at 60°C to constant weight, breaking it up, to obtain F-HAp.

[0031] The preparation of APTES-ZrO2 includes: heating nano-zirconia to 650℃ at a rate of 2℃ / min and sintering for 2.5h; under nitrogen protection, vapor deposition of APTES vapor at a volume concentration of 10% and 80℃ for 4.5h, with the ratio of APTES vapor volume to nano-zirconia mass being 5mL / g; coating the surface of the sintered nano-zirconia with APTES (3-aminopropyltriethoxysilane) and crushing it to obtain APTES-ZrO2.

[0032] The preparation of an MPC-modified composite resin involves preparing a base solution with a mass ratio of urethane dimethacrylate: glycidyl methacrylate elastomer: castor oil phosphate: MEHQ inhibitor: THF solvent of 22:5:1.3:0.05:70. 2-methacryloyloxyethyl phosphorylcholine monomer (0.8% by weight of the base solution) and Perkadox 16 initiator (0.5%) are then added. The mixture is stirred at 50°C under nitrogen for 8 hours. After cooling, 0.8 times the total volume of n-hexane containing 10% by volume acetone is added. The product is stirred and precipitated, which is then collected by filtration through a 325-mesh sieve, washed three times with n-hexane, and dried under vacuum at 50°C to constant weight to obtain the MPC-modified composite resin. The Perkadox 16 initiator concentration is 50 wt%, and the solvent is THF.

[0033] The method for preparing the above-mentioned tooth enamel repair material comprises the following steps:

[0034] S1: F-HAp, MPC-modified composite resin, MPC and composite initiator were mixed uniformly according to parts by mass to obtain mixture A, and anhydrous ethanol (10% by mass of mixture A) was added to mixture A and mixed uniformly to obtain mixture B;

[0035] S2: Add APTES-ZrO2 to anhydrous ethanol with a mass 4 times that of APTES-ZrO2, ultrasonically disperse at 200W and 30kHz for 20 minutes, add γ-MPS and ultrasonically disperse at 200W and 30kHz for 15 minutes, add dispersant and ultrasonically disperse at 200W and 30kHz for 8 minutes, add mixture B and 10-MDP in turn and stir at 200rpm to mix evenly, adjust the viscosity to 3000cP, and vacuum treat for 5 minutes to obtain enamel restoration material.

[0036] Example 2: A tooth enamel restoration material, comprising the following raw materials in parts by weight: 52 parts of F-HAp, 6.5 parts of APTES-ZrO2, 33 parts of MPC-modified composite resin, 4 parts of 10-MDP, 1.5 parts of γ-MPS, 0.8 parts of composite initiator, 0.2 parts of MPC, and 1.2 parts of dispersant; wherein F-HAp is a fluorine-doped enamel-like hydroxyapatite nanorod with a diameter range of 20nm to 30nm and a length range of 100nm to 200nm; APTES-ZrO2 is an ammonia Nano-zirconia modified with propyltriethoxysilane; the MPC-modified composite resin is a composite resin of 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer; 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate; γ-MPS is the silane coupling agent KH-570; the composite initiator is a mixture of camphorquinone and 4-EDMAB in a mass ratio of 1:1.9; MPC is 2-methacryloyloxyethyl phosphorylcholine; and the dispersant is ammonium polyacrylate.

[0037] The preparation of F-HAp includes: dissolving 0.32M Ca(NO3)2, 0.19M (NH4)2HPO4, and 0.025M NH4F in deionized water, and adjusting the pH to 9 with ammonia water; stirring and reacting at 180°C for 49 hours; centrifuging at 9000rpm for 12 minutes, washing the precipitate four times with deionized water, adding the precipitate to deionized water containing 2.3wt% of the silane coupling agent KH-570 (12 times the mass of the precipitate), ultrasonically dispersing at 300W and 35kHz for 30 minutes, centrifuging at 9000rpm for 12 minutes, and vacuum drying the solid at 65°C to constant weight, breaking it up, to obtain F-HAp.

[0038] The preparation of APTES-ZrO2 includes: heating nano-zirconia to 670℃ at a rate of 3℃ / min and sintering for 2h; under nitrogen protection, vapor deposition of APTES vapor at a volume concentration of 11% and 82℃ for 4h, with the ratio of APTES vapor volume to nano-zirconia mass being 8mL / g; coating the surface of the sintered nano-zirconia with APTES (3-aminopropyltriethoxysilane) and crushing it to obtain APTES-ZrO2.

[0039] The preparation of an MPC-modified composite resin involves preparing a base solution with a mass ratio of urethane dimethacrylate: glycidyl methacrylate elastomer: castor oil phosphate: MEHQ inhibitor: THF solvent of 23:6.5:1.4:0.08:75. 2-methacryloyloxyethyl phosphorylcholine monomer (1% by weight of the base solution) and Perkadox 16 initiator (0.6%) are then added. The mixture is stirred at 49°C under nitrogen for 7 hours. After cooling, 0.9 times the total volume of n-hexane containing 12% by volume acetone is added. The product is stirred and precipitated, which is then collected by filtration through a 325-mesh sieve, washed four times with n-hexane, and dried under vacuum at 52°C to constant weight to obtain the MPC-modified composite resin. The Perkadox 16 initiator concentration is 50 wt%, and the solvent is THF.

[0040] The method for preparing the above-mentioned tooth enamel repair material comprises the following steps:

[0041] S1: F-HAp, MPC-modified composite resin, MPC and composite initiator were mixed uniformly according to parts by mass to obtain mixture A, and anhydrous ethanol (12% by mass of mixture A) was added to mixture A and mixed uniformly to obtain mixture B;

[0042] S2: Add APTES-ZrO2 to anhydrous ethanol with a mass 4.5 times that of APTES-ZrO2, ultrasonically disperse at 200W and 35kHz for 18 minutes, add γ-MPS and ultrasonically disperse at 200W and 35kHz for 12 minutes, add dispersant and ultrasonically disperse at 200W and 35kHz for 6 minutes, add mixture B and 10-MDP in turn, stir and mix evenly at 250rpm, adjust the viscosity to 3600cP, and vacuum treat for 7 minutes to obtain enamel restoration material.

[0043] Example 3: A tooth enamel restoration material, comprising the following raw materials in parts by weight: 55 parts of F-HAp, 8 parts of APTES-ZrO2, 35 parts of MPC-modified composite resin, 5 parts of 10-MDP, 2 parts of γ-MPS, 1 part of composite initiator, 0.3 parts of MPC, and 1.5 parts of dispersant; wherein, F-HAp is a fluorine-doped enamel-like hydroxyapatite nanorod with a diameter range of 20nm to 30nm and a length range of 100nm to 200nm; APTES-ZrO2 is an aminopropyl Triethoxysilane modified nano-zirconia; MPC modified composite resin is a composite resin of 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer; 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate; γ-MPS is the silane coupling agent KH-570; the composite initiator is a mixture of camphorquinone and 4-EDMAB in a mass ratio of 1:2; MPC is 2-methacryloyloxyethyl phosphorylcholine; and the dispersant is ammonium polyacrylate.

[0044] The preparation of F-HAp includes: dissolving 0.35M Ca(NO3)2, 0.20M (NH4)2HPO4, and 0.03M NH4F in deionized water, and adjusting the pH to 9.2 with ammonia water; stirring and reacting at 185°C for 48 hours; centrifuging at 10,000 rpm for 10 minutes, washing the precipitate with deionized water five times, adding the precipitate to deionized water containing 2.5wt% of the silane coupling agent KH-570 (15 times the mass of the precipitate), ultrasonically dispersing at 350W and 40kHz for 30 minutes, centrifuging at 10,000 rpm for 10 minutes, and vacuum drying the solid at 70°C to constant weight, breaking it up, to obtain F-HAp.

[0045] The preparation of APTES-ZrO2 includes: heating nano-zirconia to 680°C at a rate of 4°C / min and sintering for 2 hours; under nitrogen protection, vapor deposition of APTES vapor at a volume concentration of 12% at 85°C for 4 hours, and a ratio of APTES vapor volume to nano-zirconia mass of 10 mL / g; coating the surface of the sintered nano-zirconia with APTES (3-aminopropyltriethoxysilane) and crushing it to obtain APTES-ZrO2.

[0046] The preparation of an MPC-modified composite resin involves preparing a base solution with a mass ratio of urethane dimethacrylate: glycidyl methacrylate elastomer: castor oil phosphate: MEHQ inhibitor: THF solvent of 25:8:1.5:0.1:80. Then, 1.2% of the base solution's mass of 2-methacryloyloxyethyl phosphorylcholine monomer and 0.8% of Perkadox 16 initiator are added. The mixture is stirred at 52°C under nitrogen for 6 hours. After cooling, 1 volume of n-hexane containing 15% acetone is added to the mixture, stirring to precipitate the product. The precipitate is collected by filtration through a 325-mesh sieve, washed five times with n-hexane, and dried under vacuum at 55°C to constant weight to obtain the MPC-modified composite resin. The Perkadox 16 initiator concentration is 50% by weight, and the solvent is THF.

[0047] The method for preparing the above-mentioned tooth enamel repair material comprises the following steps:

[0048] S1: F-HAp, MPC-modified composite resin, MPC and composite initiator were mixed uniformly according to parts by mass to obtain mixture A, and anhydrous ethanol (15% by mass of mixture A) was added to mixture A and mixed uniformly to obtain mixture B;

[0049] S2: Add APTES-ZrO2 to anhydrous ethanol with a mass 5 times that of APTES-ZrO2, ultrasonically disperse at 250W and 35kHz for 15 minutes, add γ-MPS and ultrasonically disperse at 250W and 35kHz for 10 minutes, add dispersant and ultrasonically disperse at 250W and 30kHz for 8 minutes, add mixture B and 10-MDP in turn, stir and mix evenly at 300rpm, adjust the viscosity to 4000cP, and vacuum treat for 8 minutes to obtain enamel restoration material.

[0050] The tooth enamel restoration materials prepared in the above embodiments were used to fill tooth defects or to inject into custom molds, and the enamel restoration materials ... 2 ~400mW / cm 2 The material is cured by irradiating with blue light; the irradiation is divided into two times with an interval of 10s to 15s, and each irradiation is 20s to 30s.

[0051] Sources of raw materials in the above examples: 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate, sourced from Jiangxi Boye Pharmaceutical Technology Co., Ltd. γ-MPS is silane coupling agent KH-570, sourced from Wuhan Kemik Biopharmaceutical Technology Co., Ltd., a premium grade product. MPC is 2-methacryloyloxyethyl phosphorylcholine, sourced from Hubei Langbowan Biopharmaceutical Co., Ltd. The dispersant is ammonium polyacrylate, sourced from Wuhan Kemik Biopharmaceutical Technology Co., Ltd., a premium grade product. Camphorquinone is sourced from Hubei Langbowan Biopharmaceutical Co., Ltd. 4-EDMAB is ethyl 4-dimethylaminobenzoate, sourced from Guangdong Qianjin Chemical Reagent Co., Ltd. PVP is povidone K30, sourced from Huizhou Yuanle Biopharmaceutical Technology Co., Ltd. APTES is 3-aminopropyltriethoxysilane, sourced from Guangdong Runhe Biopharmaceutical Technology Co., Ltd. Urethane dimethacrylate (UDMA) is sourced from Shanghai Youying Chemical Technology Co., Ltd. Glycidyl methacrylate elastomer (TPU-GMA) is sourced from Dongguan Shengli New Materials Co., Ltd. Castor oil phosphate was sourced from Hubei Xinmingtai Chemical Co., Ltd. MEHQ polymerization inhibitor was sourced from Shandong Jinshengtai Chemical Co., Ltd. THF solvent was tetrahydrofuran from BASF. Perkadox 16 initiator was sourced from Jiangsu Zhipai Chemical Co., Ltd.

[0052] Comparative Example 1

[0053] In the preparation of F-HAp, no NH4F was added and no silane coupling agent KH-570 was added, that is, F-HAp was replaced by HAp; other parameters and methods were the same as in Example 1.

[0054] Comparative Example 2

[0055] In the preparation of APTES-ZrO2, nano-zirconium oxide was not subjected to sintering pretreatment; other parameters and methods were the same as those in Example 1.

[0056] Comparative Example 3

[0057] In the preparation of APTES-ZrO2, APTES-ZrO2 is directly replaced by nano-zirconium oxide; other parameters and methods are the same as in Example 1.

[0058] Comparative Example 4

[0059] In the preparation of the MPC modified composite resin, no glycidyl methacrylate elastomer was added; other parameters and methods were the same as in Example 1.

[0060] Comparative Example 5

[0061] In the preparation of the MPC modified composite resin, the amount of glycidyl methacrylate elastomer added was changed to 15 parts; other parameters and methods were the same as in Example 1.

[0062] Comparative Example 6

[0063] In the preparation of the MPC modified composite resin, castor oil phosphate was not added; other parameters and methods were the same as in Example 1.

[0064] Comparative Example 7

[0065] In the preparation of the MPC modified composite resin, no MEHQ polymerization inhibitor was added; other parameters and methods were the same as in Example 1.

[0066] Comparative Example 8

[0067] The MPC-modified composite resin was directly replaced by dimethacrylate urethane and glycidyl methacrylate elastomers (without MPC modification); other parameters and methods were the same as in Example 1.

[0068] Comparative Example 9

[0069] In the preparation method of the tooth enamel repair material, all raw materials are blended together, stirred at 300 rpm for 40 minutes, the viscosity is adjusted to 4000 cP with anhydrous ethanol, and vacuum treated for 8 minutes to obtain the tooth enamel repair material; other parameters and methods are the same as in Example 1.

[0070] For the sake of experimental consistency, the curing parameters of enamel restoration materials in the following test items are unified as follows: wavelength 405nm, power density 300mW / cm 2 The material is cured by irradiating with blue light; the irradiation is divided into two times with an interval of 10 seconds, and each irradiation is 20 seconds.

[0071] 1. Bond strength test

[0072] Select discarded human ex vivo teeth, polish the enamel surface and cut them into blocks with a size of 5mm×5mm×2mm. Fill the enamel repair material (the enamel repair material prepared in each embodiment and each comparative example, the same below) between the two enamel blocks and solidify to form a bonding sample. Five parallel samples are prepared in each group. The bonding sample is placed in the equipment fixture and a tensile test is performed at a loading rate of 1mm / min. The maximum load when the sample is destroyed is recorded, and the bonding strength is calculated according to the formula: Bonding strength (MPa) = Destruction load (N) / Bonding area (mm 2 ).

[0073] 2. Cytotoxicity Assay

[0074] The enamel restoration material was injected into a mold to form a 10 mm diameter and 1 mm thick disc. After sterilization at high temperature and high pressure, it was placed in a cell culture plate. Five parallel samples were prepared for each group. Cytotoxicity experiments were performed using the MTT method. Cultured oral fibroblasts were cultured at a rate of 1×10 4Cells were seeded at a density of 100 cells / well in a 96-well cell culture plate. After 24 hours of incubation, sterilized repair material samples were placed into the wells. A blank control group (culture medium only) and a negative control group (cells and culture medium) were also set up. After 72 hours of incubation, 20 μL of MTT solution (5 mg / mL) was added to each well and incubated for another 4 hours. The culture medium was discarded, and 150 μL of dimethyl sulfoxide (DMSO) was added to each well. The plates were shaken for 10 minutes to fully dissolve the formazan. The absorbance of each well was measured at 570 nm using a microplate reader. Cell viability was calculated according to the formula: Cell viability (%) = (absorbance of experimental group - absorbance of blank control group) / (absorbance of negative control group - absorbance of blank control group) × 100%.

[0075] 3. Anti-leakage performance test

[0076] A discarded human excised tooth was selected, and a 3mm diameter and 2mm deep cavity was prepared in the crown. Enamel restorative material was filled into the cavity and cured to prepare a leak-proof specimen. Five parallel specimens were prepared for each group. The leak-proof specimens were immersed in a 2wt% methylene blue solution at 37°C for 48 hours. The specimens were removed, and the residual dye on the surface was rinsed with clean water. The cavity was then cut open longitudinally, and the dye penetration depth was observed using a stereomicroscope. The dye penetration depth for each specimen was recorded and averaged.

[0077] 4. Mechanical properties-compressive strength test

[0078] The enamel restoration material was injected into a mold to form a block specimen measuring 10 mm × 10 mm × 5 mm. Five parallel specimens were prepared for each group. The mechanical properties specimens were placed in the equipment fixture and subjected to compression testing at a loading rate of 2 mm / min. The maximum load at specimen failure was recorded, and the compressive strength was calculated according to the formula: Compressive Strength (MPa) = Failure Load (N) / Compressed Area of ​​Specimen (mm²).

[0079] 5. Mechanical properties-elastic modulus test

[0080] The sample preparation was the same as above, with 10 mm × 10 mm × 5 mm block specimens and 5 parallel specimens. The mechanical properties specimens were subjected to axial compression loading at a loading rate of 1 mm / min, and the load-displacement curve was recorded. The displacement was obtained from the linear elastic region of the load-displacement curve (within the strain range of 0.1%-0.4%). The elastic modulus of the material was calculated as follows: elastic modulus (GPa) = [failure load (N) × original height (mm)] / [displacement (mm) × compressed area (mm)] 2 )]×10 -3 .

[0081] Table 1 Test results (typical values)

[0082]

[0083] The above results demonstrate that Examples 1 to 3 exhibit superior nanostructure integration and interfacial bonding. This is due to their core design: F-HAp mimics the nanostructure of natural tooth enamel, providing bioactivity and mechanical support; APTES-ZrO2 enhances interfacial bonding and reduces microleakage; MPC-modified composite resin imparts flexibility and biocompatibility; and a step-by-step preparation ensures uniform dispersion.

[0084] In the preparation of F-HAp in Comparative Example 1, NH4F and silane coupling agent KH-570 were not added, and HAp was used instead. The addition of NH4F causes the generated hydroxyapatite to be doped with fluorine. Fluorine doping distorts the lattice of hydroxyapatite, increasing the density and stability of the crystal. The fluorine element can improve the chemical stability and anti-caries performance of the material, while changing the crystal structure and surface properties of the material and enhancing the binding force with other components. The silane coupling agent KH-570 can improve the dispersibility of nanoparticles in the matrix, improve the interfacial compatibility and bonding properties of the material, and make the HAp crystal arrangement disordered, not as dense as F-HAp. The lack of these components leads to a decrease in the bonding strength, compressive strength and elastic modulus of the material, poor biocompatibility, and reduced anti-leakage performance.

[0085] In the preparation of APTES-ZrO2 in Comparative Example 2, nano-zirconia was not subjected to sintering pretreatment. Sintering pretreatment removes impurities and adsorbed moisture on the surface of nano-zirconia, improves its crystal structure, increases the density and hardness of the material, and increases surface active sites, which is beneficial to the subsequent modification of APTES. Failure to perform sintering pretreatment results in poor surface properties of nano-zirconia, reduced surface hydroxyl groups, low APTES vapor deposition efficiency, poor APTES modification effect, uneven zirconium oxide dispersion, decreased bonding properties, mechanical properties, and biocompatibility of the material, insufficient APTES coating, weakened chemical bonding between ZrO2 and the resin, and increased interface microleakage.

[0086] In the preparation of APTES-ZrO2 in Comparative Example 3, APTES-ZrO2 was directly replaced by nano-zirconia without being modified by APTES. APTES-modified nano-zirconia introduces active groups such as amino groups on its surface. These active groups can react chemically with active groups in other components to form chemical bonds, thereby enhancing the interfacial bonding and compatibility of the material. Direct use of nano-zirconia lacks the connecting effect of such chemical bonds, resulting in a mismatch in interfacial chemistry. Zirconia as a rigid phase is not integrated into the resin network, increasing the overall brittleness of the material, resulting in a decrease in the material's bonding strength, compressive strength, elastic modulus, and anti-leakage performance, and also affecting its biocompatibility to a certain extent.

[0087] In the preparation of the MPC-modified composite resin of Comparative Example 4, no glycidyl methacrylate elastomer was added. Glycidyl methacrylate elastomer provides flexibility and stress buffering, improving the toughness and fatigue resistance of the composite resin. Without this elastomer, the resin becomes brittle, shrinking more during curing, resulting in reduced toughness. The elastomer also enhances the mechanical interlock between the resin and F-HAp; its absence slightly reduces bond strength and elastic modulus, and also compromises bonding and anti-leakage properties.

[0088] In the preparation of the MPC-modified composite resin of Comparative Example 5, the glycidyl methacrylate elastomer was added in an amount of 15 parts. Excessive glycidyl methacrylate elastomer disrupts the crosslinked network structure of the composite resin, destroying the rigid network (dominated by urethane dimethacrylate), reducing the crosslink density, and ultimately lowering the material's strength and hardness. High elastomer content reduces resin stiffness, making it susceptible to deformation under tensile loads and reducing bond strength. Curing shrinkage is uneven, interfacial bonding is weak, and penetration depth is increased.

[0089] In the preparation of the MPC-modified composite resin of Comparative Example 6, castor oil phosphate was not added. Castor oil phosphate acts as a plasticizer and coupling agent in the composite resin, improving the material's toughness and processing properties while enhancing the interfacial bonding between the material and the filler. Castor oil phosphate also improves the compatibility of the dimethacrylate urethane and glycidyl methacrylate elastomers, promoting grafting reactions and network interpenetration. Without the addition of castor oil phosphate, the material's fluidity deteriorates, the bonding between the filler and the matrix weakens, and the material becomes slightly brittle, resulting in reduced bond strength, compressive strength, elastic modulus, and anti-leakage properties.

[0090] In the preparation of the MPC-modified composite resin of Comparative Example 7, no MEHQ polymerization inhibitor was added. During the composite resin preparation process, the MEHQ polymerization inhibitor effectively inhibits monomer autopolymerization during storage and preparation, ensuring the controllability of the reaction. Without the addition of the MEHQ polymerization inhibitor, the monomers would partially polymerize prematurely, affecting the normal progress of the reaction. During curing, the initiator (Perkadox 16) would react uncontrollably, resulting in internal defects. This would cause the composite resin to have an uneven structure, uneven curing shrinkage, and weakened bonding, thereby reducing the material's bond strength, compressive strength, elastic modulus, and biocompatibility, and also affecting its anti-leakage properties.

[0091] The MPC-modified composite resin in Comparative Example 8 is directly replaced with dimethacrylate urethane and glycidyl methacrylate elastomers. The unmodified components exhibit poor bonding during mixing and curing, resulting in high material brittleness and minimal compressive strength and modulus. This lacks the advantages of MPC modification and its synergistic effects with other components. MPC modification introduces phosphorylcholine groups, improving the material's biocompatibility and bonding properties. It also synergizes with other components (such as glycidyl methacrylate elastomer and castor oil phosphate) to optimize the material's mechanical properties and anti-leakage performance. Direct substitution results in a decrease in all material properties.

[0092] In the preparation method of the tooth enamel restoration material of Comparative Example 9, all raw materials were blended together, rather than following the step-by-step mixing method described in the previous examples. This step-by-step mixing method allows each raw material to fully disperse and react at different stages, ensuring the uniformity and performance stability of the material. Blending together results in uneven dispersion of the raw materials, preventing some components from fully functioning, and preventing γ-MPS and 10-MDP from preferentially treating the filler, resulting in weak interfacial chemical bonding and affecting the material's bonding, mechanical properties, biocompatibility, and anti-leakage performance.

Claims

1. A tooth enamel repair material, characterized in that: The method comprises the following raw materials in parts by weight: 50 to 55 parts of F-HAp, 5 to 8 parts of APTES-ZrO2, 30 to 35 parts of MPC-modified composite resin, 3 to 5 parts of 10-MDP, 1 to 2 parts of γ-MPS, 0.5 to 1 part of composite initiator, 0.1 to 0.3 parts of MPC and 1 to 1.5 parts of dispersant; The F-HAp is a fluorine-doped enamel-like hydroxyapatite nanorod with a diameter of 20 nm to 30 nm and a length of 100 nm to 200 nm; the APTES-ZrO2 is aminopropyltriethoxysilane-modified nano-zirconium oxide; the MPC-modified composite resin is a 2-methacryloyloxyethyl phosphorylcholine grafted modified dimethacrylate urethane and glycidyl methacrylate elastomer composite resin; the 10-MDP is 10-(2-methacryloyloxy) monodecyl phosphate; the γ-MPS is a silane coupling agent KH-570; the composite initiator is a mixture of camphorquinone and 4-EDMAB in a mass ratio of 1:(1.8-2); the MPC is 2-methacryloyloxyethyl phosphorylcholine; and the dispersant is ammonium polyacrylate. The preparation of the MPC-modified composite resin includes: preparing a base liquid according to a mass ratio of dimethacrylate urethane: methacrylate glycidyl elastomer: castor oil phosphate: MEHQ inhibitor: THF solvent = (22-25): (5-8): (1.3-1.5): (0.05-0.1): (70-80), then adding 0.8%-1.2% of 2-methacryloyloxyethyl phosphorylcholine monomer and 0.5%-0.8% of Perkadox 16 initiator by mass of the base liquid, stirring and reacting at 49°C-52°C for 6-8 hours under nitrogen protection; after cooling, adding 0.8 times to 1 times the total volume of n-hexane containing 10%-15% by volume of acetone, stirring, and precipitating a product, filtering and collecting the precipitate, washing with n-hexane, and vacuum drying to obtain the MPC-modified composite resin.

2. The tooth enamel repair material according to claim 1, characterized in that: The preparation of the F-HAp includes: dissolving 0.3M to 0.35M Ca(NO3)2, 0.18M to 0.20M (NH4)2HPO4, and 0.02M to 0.03M NH4F in deionized water, and adjusting the pH to 8.8 to 9.2 with ammonia water; stirring and reacting at 175°C to 185°C for 48h to 50h; centrifuging, washing the precipitate with deionized water, adding the precipitate to deionized water containing 2wt% to 2.5wt% of a silane coupling agent KH-570 in an amount 10 times to 15 times the mass of the precipitate, ultrasonically dispersing, centrifuging, and vacuum drying the solid to obtain F-HAp.

3. The tooth enamel repair material according to claim 2, characterized in that: The centrifugation is performed at 8000 rpm to 10000 rpm for 10 to 15 minutes; the deionized water washing is performed 3 to 5 times; the ultrasonic dispersion is performed at 300W to 350W and 35kHz to 40kHz for 30 to 40 minutes; and the vacuum drying is performed at 60°C to 70°C to a constant weight.

4. The tooth enamel repair material according to claim 1, characterized in that: The preparation of APTES-ZrO2 includes: heating nano-zirconia to 650°C to 680°C and sintering for 2h to 2.5h; under nitrogen protection, vapor-depositing APTES vapor at a volume concentration of 10% to 12% and 80°C to 85°C for 4h to 4.5h, and coating APTES on the surface of the sintered nano-zirconia to obtain APTES-ZrO2.

5. The tooth enamel repair material according to claim 4, characterized in that: The heating rate is 2°C / min to 4°C / min; and the APTES is aminopropyltriethoxysilane.

6. The tooth enamel repair material according to claim 1, characterized in that: In the preparation of the MPC-modified composite resin, the filtration mesh size is 325 meshes; the number of n-hexane washings is 3 to 5 times; the vacuum drying is performed at 50° C. to 55° C. to a constant weight; the mass concentration of the Perkadox 16 initiator is 50 wt %, and the solvent is THF solvent.

7. The method for preparing a tooth enamel repair material according to claim 1, characterized in that: The steps include: S1: F-HAp, MPC-modified composite resin, MPC and composite initiator were mixed uniformly according to parts by mass to obtain a mixture A, and anhydrous ethanol was added to the mixture A and mixed uniformly to obtain a mixture B; S2: Add APTES-ZrO2 to anhydrous ethanol with a mass of 4 to 5 times that of APTES-ZrO2, ultrasonically disperse for 15 to 20 minutes, add γ-MPS and ultrasonically disperse for 10 to 15 minutes, add dispersant and ultrasonically disperse for 5 to 8 minutes, add mixture B and 10-MDP in sequence, stir and mix evenly, adjust the viscosity, and vacuum treat to obtain the enamel restoration material.

8. The method for preparing a tooth enamel repair material according to claim 7, characterized in that: In S1, the amount of anhydrous ethanol added is 10% to 15% of the mass of mixture A; in S2, the power of the ultrasonic dispersion is 200W to 250W; the speed of the stirring and mixing is 200rpm to 300rpm; the viscosity is adjusted to 3000cP to 4000cP; and the time of the vacuum treatment is 5min to 8min.

9. The method for preparing a tooth enamel repair material according to claim 7, characterized in that: The tooth enamel restoration material is used to fill the tooth defect or inject into the customized mold, with a wavelength of 405nm and a power density of 300mW / cm 2 ~400mW / cm 2 The material is cured by irradiating with blue light; the irradiation is divided into two times with an interval of 10s to 15s, and each irradiation is 20s to 30s.

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