Low-shrinkage antibacterial denture base resin composite material and preparation method thereof

Abstract

The application discloses a low-shrinkage antibacterial denture base resin composite material and a preparation method thereof, relates to the field of preparation of the low-shrinkage antibacterial denture base resin composite material, and comprises a methyl methacrylate resin matrix, grafted modified nano silicon dioxide, a chitosan zinc composite antibacterial powder and a crosslinking modified additive. The low-shrinkage antibacterial denture base resin composite material and the preparation method thereof have the advantages that the process steps are progressive and mutually complementary, the modification of the powder provides a structural basis for low shrinkage and long-acting antibacterial properties, the gradient curing and locking of the modified powder lock the functional characteristics, the post-processing technology further stabilizes the comprehensive performance of the material, the problems that the antibacterial performance, the low-shrinkage performance and the mechanical performance cannot be considered simultaneously in the traditional technology are solved, and through the synergistic process of powder fine pretreatment, step-by-step homogeneous mixing, gradient segmented prepolymerization curing and constant-temperature aging post-processing, remarkable technical progress and practical effects are achieved.

Description

Technical Field

[0001] This invention relates to the field of preparation of low-shrinkage antibacterial denture base resin composite materials, and particularly to a low-shrinkage antibacterial denture base resin composite material and its preparation method. Background Technology

[0002] Dental base resin is the most widely used core material in the field of oral restoration. The mainstream method is to prepare it using methyl methacrylate resin system. This material has the basic advantages of convenient molding, strong adaptability and good biocompatibility, which can meet the basic usage needs of conventional denture restoration.

[0003] Currently, most denture base resin manufacturing processes employ simple powder blending and one-time high-temperature curing. Functional fillers are often directly mixed with unmodified ordinary inorganic powders and conventional antibacterial powders, resulting in a crude and simplistic overall manufacturing process. Existing technologies have several inherent drawbacks in practical applications. First, unmodified inorganic fillers have poor interfacial compatibility with the resin matrix, making the powders prone to agglomeration. This not only prevents uniform dispersion within the resin system but also leads to a loose internal structure in the base material, significantly reducing its overall mechanical properties and structural density. Second, conventional antibacterial powders, lacking purification and refinement, have weak bonding with the resin matrix. In the complex environment of the oral cavity—moist and pH-fluctuating—they are easily precipitated and lost, causing a rapid decline in the antibacterial performance of the denture base. This prevents long-term antibacterial effects and can easily lead to oral inflammation and plaque buildup in wearers. Meanwhile, traditional integrated high-temperature curing processes involve rapid heating and intense polymerization reactions. The cross-linking of resin molecules generates significant concentrated polymerization stress, leading to substantial volume shrinkage. This results in denture bases prone to deformation, warping, and decreased fit, exhibiting extremely poor stability during long-term wear. Furthermore, existing manufacturing processes lack dedicated powder modification, gradient curing, and stress relief procedures. The components cannot achieve effective synergy, and the material's low-shrinkage properties, antibacterial properties, and mechanical properties are mutually constrained and difficult to balance, severely impacting the lifespan of denture bases and oral safety.

[0004] Therefore, it is necessary to propose a low-shrinkage antibacterial denture base resin composite material and its preparation method to solve the above problems. Summary of the Invention

[0005] The main objective of this invention is to provide a low-shrinkage antibacterial denture base resin composite material and its preparation method, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a low-shrinkage antibacterial denture base resin composite material, comprising a methyl methacrylate resin matrix, grafted modified nano-silica, chitosan zinc composite antibacterial powder, and a crosslinking modification agent. The methyl methacrylate resin matrix, grafted modified nano-silica, chitosan zinc composite antibacterial powder, and crosslinking modification agent comprise, by weight, 79-85 parts of methyl methacrylate resin matrix, 6-10 parts of grafted modified nano-silica, 5-7 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

[0007] Preferably, the methyl methacrylate resin matrix comprises 82 parts, the grafted modified nano silica comprises 8 parts, the chitosan zinc composite antibacterial powder comprises 6 parts, and the crosslinking modification agent comprises 4 parts.

[0008] Preferably, the methyl methacrylate resin matrix comprises 85 parts, grafted modified nano-silica comprises 6 parts, chitosan zinc composite antibacterial powder comprises 5 parts, and crosslinking modification agent comprises 4 parts.

[0009] Preferably, the methyl methacrylate resin matrix comprises 79 parts, grafted modified nano-silica comprises 10 parts, chitosan zinc composite antibacterial powder comprises 7 parts, and crosslinking modification agent comprises 4 parts.

[0010] A method for preparing a low-shrinkage antibacterial denture base resin composite material includes the following steps: S1: Refined pretreatment of functional composite powders, through activation, grafting and purification processes, solves the problems of powder agglomeration, poor compatibility with resin matrix and easy loss of antibacterial components; S2: The resin matrix is ​​homogeneously mixed in steps, and a step-by-step doping and mixing process is adopted to achieve the ultimate fusion between the modified powder in S1 and the resin matrix. S3: Gradient segmented prepolymer curing molding, which uses low-temperature prepolymerization, vacuum degassing and gradient temperature curing for curing; S4: Constant temperature aging stabilization post-treatment, used to eliminate residual stress inside the material and solidify and stabilize the antibacterial components.

[0011] Preferably, S1 specifically includes: S101: Nano silica hydroxyl activation treatment. Select high-purity silica powder with a particle size of 20 to 40 nanometers, place it in a constant temperature drying oven, set the temperature to 120 degrees Celsius, and continue drying for 4 hours to completely remove the moisture and impurities adsorbed on the powder surface. Place the dried powder into a high-speed stirred reactor, add anhydrous ethanol to immerse the powder, and stir at a uniform speed for 30 minutes. Set the stirring speed to 800 rpm to complete the powder dispersion pretreatment and ensure that the active hydroxyl groups are uniformly exposed on the powder surface. S102: In-situ acrylic acid grafting modification of nano-silica. Acrylic acid monomer was slowly added dropwise to a uniformly dispersed silica-ethanol system. The reaction vessel was sealed and heated to 75 degrees Celsius. The mixture was stirred at a constant temperature for 2.5 hours to allow the acrylic acid monomer to undergo a covalent grafting reaction with the active hydroxyl groups on the powder surface. After the reaction was completed, the system was centrifuged and filtered to collect the solid powder. The powder was washed three times with anhydrous ethanol to remove unreacted monomer impurities. The powder was then dried at 80 degrees Celsius to constant weight to obtain grafted modified nano-silica. S103: Purification and Refining of Chitosan-Zinc Composite Antibacterial Powder. The powder after chitosan and zinc acetate are composited and sintered in a fixed ratio is placed in an air jet mill for ultrafine grinding. The particle size is controlled to be uniformly maintained at 500 to 800 nanometers. After grinding, it is sieved with a 200-mesh standard sieve to remove large particle impurities. Then it is placed in a vacuum constant temperature environment and dried for 3 hours to obtain chitosan-zinc composite antibacterial powder with uniform purity and consistent particle size, ensuring uniform and stable antibacterial performance.

[0012] Preferably, step S2 specifically includes: S201: Constant temperature softening treatment of resin matrix. Accurately weigh the methyl methacrylate resin matrix according to the mass fraction, put it into a sealed stirring container, set the constant temperature to 45 degrees Celsius, and stir at low speed for 15 minutes to completely soften the solid resin matrix. S202: Two-powder stepwise doping and mixing: First, cross-linking modifiers are added to the softened resin matrix and stirred at a constant speed for 20 minutes to achieve molecular fusion of the modifiers and the matrix. Then, grafted modified nano-silica is added in two batches, and stirred for 15 minutes after each addition. Finally, chitosan zinc composite antibacterial powder is added all at once and stirred at high speed for 40 minutes. The stirring speed is set to 1200 rpm. Finally, a resin composite premix with no agglomeration and uniform composition is obtained.

[0013] Preferably, step S3 specifically includes: S301: Low-temperature and low-speed prepolymerization reaction. The resin composite premix is ​​injected into a standard denture base mold, placed in a constant temperature prepolymerization device, and the initial temperature is set to 50 degrees Celsius. Low-speed constant temperature prepolymerization is carried out for 60 minutes to allow the resin molecules to initially cross-link and form. S302: Vacuum pressure stabilization and degassing treatment. After prepolymerization, the mold is moved into the vacuum degassing equipment, the vacuum degree is set to 0.08 MPa, and it is kept at room temperature and pressure for 25 minutes to completely remove the tiny air bubbles inside the prepolymer and eliminate the porosity defects after the base is formed. S303: Gradient temperature rise curing molding, using a three-stage gradient temperature rise mode for curing. The first stage heats up to 65 degrees Celsius and is kept at a constant temperature for 30 minutes; the second stage heats up to 75 degrees Celsius and is kept at a constant temperature for 40 minutes; the third stage heats up to 85 degrees Celsius and is kept at a constant temperature for 50 minutes. The temperature rises at a uniform rate throughout the process without sudden temperature changes, so that the resin molecules are completely cross-linked and cured.

[0014] Preferably, step S4 specifically includes: S401: Constant temperature aging and shaping treatment, the cured denture base semi-finished product is taken out of the mold and placed in a constant temperature and dust-free environment of 40 degrees Celsius for 12 hours to complete the relaxation of internal stress of the material; S402: Fine surface polishing treatment. Medical-grade polishing compound is used to polish the base surface step by step to remove excess material and fine burrs, keeping the base surface smooth and dense, and sealing the surface micropores.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This low-shrinkage antibacterial denture base resin composite material and its preparation method, through a synergistic process of fine powder pretreatment, stepwise homogenous mixing, gradient segmented prepolymerization and curing, and isothermal aging post-treatment, overcomes existing technical bottlenecks from two dimensions: material component modification and preparation process optimization, achieving significant technological progress and practical effects. In-situ grafting modification with inorganic fillers completely solves the problems of traditional inorganic filler agglomeration and poor compatibility with the resin matrix, enabling the modified powder to form a stable molecular bond structure with the resin matrix. This fundamentally fills the molecular gaps generated during resin polymerization, significantly reducing the resin polymerization shrinkage rate and eliminating the problems of deformation and warping after base molding. Simultaneously, the purification and refinement of the chitosan zinc composite antibacterial powder ensures uniform particle size and stable purity, and the powder can be stably embedded within the resin matrix without precipitating or leaking out in the oral environment, achieving a long-lasting and uniform antibacterial effect and continuously inhibiting the growth of oral bacteria.

[0016] This invention relates to a low-shrinkage antibacterial denture base resin composite material and its preparation method. It employs a step-by-step mixing process instead of the traditional one-time feeding process, achieving extremely uniform dispersion of each component, eliminating localized stress concentration defects within the material, and simultaneously improving the material's structural density and mechanical properties. A gradient-segmented prepolymerization and curing process replaces the traditional high-temperature integrated curing mode, slowly releasing resin polymerization stress and avoiding volume shrinkage caused by rapid, intense polymerization. Combined with subsequent isothermal aging and setting treatment, residual stress within the material is completely eliminated, ensuring the structural stability of the denture base for long-term use. The various process steps of this invention are progressive and mutually reinforcing. Powder modification provides the structural basis for low shrinkage and long-lasting antibacterial properties; gradient curing locks in the functional characteristics of the modified powder; and post-treatment further stabilizes the material's overall performance, overcoming the problem in traditional technologies where antibacterial properties, low shrinkage properties, and mechanical properties cannot be simultaneously achieved. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0018] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0019] Example 1: like Figure 1 As shown, a low-shrinkage antibacterial denture base resin composite material comprises 82 parts of methyl methacrylate resin matrix, 8 parts of grafted modified nano silica, 6 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

[0020] A method for preparing a low-shrinkage antibacterial denture base resin composite material includes the following steps: S1: Refined pretreatment of functional composite powders, through activation, grafting, and purification processes, solves the problems of powder agglomeration, poor compatibility with resin matrices, and easy loss of antibacterial components. Specifically, this includes: S101: Nano silica hydroxyl activation treatment. Select high-purity silica powder with a particle size of 20 to 40 nanometers, place it in a constant temperature drying oven, set the temperature to 120 degrees Celsius, and continue drying for 4 hours to completely remove the moisture and impurities adsorbed on the powder surface. Place the dried powder into a high-speed stirred reactor, add anhydrous ethanol to immerse the powder, and stir at a uniform speed for 30 minutes. Set the stirring speed to 800 rpm to complete the powder dispersion pretreatment and ensure that the active hydroxyl groups are uniformly exposed on the powder surface. S102: In-situ acrylic acid grafting modification of nano-silica. Acrylic acid monomers were slowly added dropwise to a uniformly dispersed silica-ethanol system. The reaction vessel was sealed and heated to 75 degrees Celsius. The mixture was stirred at a constant temperature for 2.5 hours to allow the acrylic acid monomers to undergo a covalent grafting reaction with the active hydroxyl groups on the powder surface. After the reaction, the system was centrifuged and filtered to collect the solid powder. The powder was washed three times with anhydrous ethanol to remove unreacted monomer impurities. The powder was then dried at 80 degrees Celsius to a constant weight to obtain grafted modified nano-silica. This modified powder can form molecular bonds with the resin matrix, thereby reducing the shrinkage gap during resin polymerization from the source. S103: Purification and Refining of Chitosan-Zinc Composite Antibacterial Powder. The powder after chitosan and zinc acetate are composited and sintered in a fixed ratio is placed in an air jet mill for ultrafine grinding. The particle size is controlled to be uniformly maintained at 500 to 800 nanometers. After grinding, it is sieved with a 200-mesh standard sieve to remove large particle impurities. Then it is placed in a vacuum constant temperature environment and dried for 3 hours to obtain chitosan-zinc composite antibacterial powder with uniform purity and consistent particle size, ensuring uniform and stable antibacterial performance.

[0021] S2: The resin matrix is ​​homogeneously mixed in stages, using a stepwise doping and mixing process to achieve ultimate fusion between the modified powder in S1 and the resin matrix. Specifically, this includes: S201: Constant temperature softening treatment of resin matrix. Accurately weigh the methyl methacrylate resin matrix according to the mass fraction, put it into a sealed stirring container, set the constant temperature to 45 degrees Celsius, stir at low speed for 15 minutes to completely soften the solid resin matrix, fully stretch the internal molecular chains, and eliminate the original stress inside the matrix. S202: Two-powder stepwise doping and mixing: First, cross-linking modifiers are added to the softened resin matrix and stirred at a constant speed for 20 minutes to achieve molecular fusion of the modifiers and the matrix. Then, grafted modified nano-silica is added in two batches, and stirred for 15 minutes after each addition. Finally, chitosan zinc composite antibacterial powder is added all at once and stirred at high speed for 40 minutes. The stirring speed is set to 1200 rpm. Finally, a resin composite premix with no agglomeration and uniform composition is obtained.

[0022] S3: Gradient segmented prepolymer curing molding, using low-temperature prepolymerization, vacuum degassing, and gradient temperature curing for curing, specifically including: S301: Low-temperature and low-speed prepolymerization reaction. The resin composite premix is ​​injected into a standard denture base mold and placed in a constant temperature prepolymerization device. The initial temperature is set to 50 degrees Celsius, and low-speed constant temperature prepolymerization is carried out for 60 minutes to allow the resin molecules to initially cross-link and form, slowly release the polymerization stress, and avoid the volume shrinkage caused by rapid polymerization. S302: Vacuum pressure stabilization and degassing treatment. After prepolymerization, the mold is moved into the vacuum degassing equipment, the vacuum degree is set to 0.08 MPa, and it is kept at room temperature and pressure for 25 minutes to completely remove the tiny air bubbles inside the prepolymer, eliminate the pore defects after the base is formed, and improve the material density and antibacterial stability. S303: Gradient temperature curing molding, using a three-stage gradient temperature curing mode. The first stage heats up to 65 degrees Celsius and is kept at a constant temperature for 30 minutes; the second stage heats up to 75 degrees Celsius and is kept at a constant temperature for 40 minutes; the third stage heats up to 85 degrees Celsius and is kept at a constant temperature for 50 minutes. The temperature rises at a uniform rate throughout the process without sudden temperature changes, allowing the resin molecules to fully cross-link and cure, minimizing the overall polymerization shrinkage rate.

[0023] S4: Constant temperature aging stabilization post-treatment, used to eliminate residual stress inside the material and solidify and stabilize the antibacterial components, specifically including: S401: Constant temperature aging and shaping treatment. The solidified denture base semi-finished product is taken out of the mold and placed in a constant temperature and dust-free environment of 40 degrees Celsius for 12 hours to complete the relaxation of internal stress of the material, stabilize the molecular cross-linking structure, and completely eliminate the problem of deformation and shrinkage in the later stage. S402: Fine surface polishing treatment. The surface of the base is polished step by step with medical-grade polishing paste to remove excess material and fine burrs, keeping the surface of the base smooth and dense, sealing the surface micropores, effectively preventing oral bacteria from adhering, and achieving a dual antibacterial effect inside and out in combination with internal antibacterial components.

[0024] Example 2: like Figure 1 As shown, a low-shrinkage antibacterial denture base resin composite material comprises 85 parts of methyl methacrylate resin matrix, 6 parts of grafted modified nano-silica, 5 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

[0025] A method for preparing a low-shrinkage antibacterial denture base resin composite material includes the following steps: S1: Refined pretreatment of functional composite powders, through activation, grafting, and purification processes, solves the problems of powder agglomeration, poor compatibility with resin matrices, and easy loss of antibacterial components. Specifically, this includes: S101: Nano silica hydroxyl activation treatment. Select high-purity silica powder with a particle size of 20 to 40 nanometers, place it in a constant temperature drying oven, set the temperature to 120 degrees Celsius, and continue drying for 4 hours to completely remove the moisture and impurities adsorbed on the powder surface. Place the dried powder into a high-speed stirred reactor, add anhydrous ethanol to immerse the powder, and stir at a uniform speed for 30 minutes. Set the stirring speed to 800 rpm to complete the powder dispersion pretreatment and ensure that the active hydroxyl groups are uniformly exposed on the powder surface. S102: In-situ acrylic acid grafting modification of nano-silica. Acrylic acid monomers were slowly added dropwise to a uniformly dispersed silica-ethanol system. The reaction vessel was sealed and heated to 75 degrees Celsius. The mixture was stirred at a constant temperature for 2.5 hours to allow the acrylic acid monomers to undergo a covalent grafting reaction with the active hydroxyl groups on the powder surface. After the reaction, the system was centrifuged and filtered to collect the solid powder. The powder was washed three times with anhydrous ethanol to remove unreacted monomer impurities. The powder was then dried at 80 degrees Celsius to a constant weight to obtain grafted modified nano-silica. This modified powder can form molecular bonds with the resin matrix, thereby reducing the shrinkage gap during resin polymerization from the source. S103: Purification and Refining of Chitosan-Zinc Composite Antibacterial Powder. The powder after chitosan and zinc acetate are composited and sintered in a fixed ratio is placed in an air jet mill for ultrafine grinding. The particle size is controlled to be uniformly maintained at 500 to 800 nanometers. After grinding, it is sieved with a 200-mesh standard sieve to remove large particle impurities. Then it is placed in a vacuum constant temperature environment and dried for 3 hours to obtain chitosan-zinc composite antibacterial powder with uniform purity and consistent particle size, ensuring uniform and stable antibacterial performance.

[0026] S2: The resin matrix is ​​homogeneously mixed in stages, using a stepwise doping and mixing process to achieve ultimate fusion between the modified powder in S1 and the resin matrix. Specifically, this includes: S201: Constant temperature softening treatment of resin matrix. Accurately weigh the methyl methacrylate resin matrix according to the mass fraction, put it into a sealed stirring container, set the constant temperature to 45 degrees Celsius, stir at low speed for 15 minutes to completely soften the solid resin matrix, fully stretch the internal molecular chains, and eliminate the original stress inside the matrix. S202: Two-powder stepwise doping and mixing: First, cross-linking modifiers are added to the softened resin matrix and stirred at a constant speed for 20 minutes to achieve molecular fusion of the modifiers and the matrix. Then, grafted modified nano-silica is added in two batches, and stirred for 15 minutes after each addition. Finally, chitosan zinc composite antibacterial powder is added all at once and stirred at high speed for 40 minutes. The stirring speed is set to 1200 rpm. Finally, a resin composite premix with no agglomeration and uniform composition is obtained.

[0027] S3: Gradient segmented prepolymer curing molding, using low-temperature prepolymerization, vacuum degassing, and gradient temperature curing for curing, specifically including: S301: Low-temperature and low-speed prepolymerization reaction. The resin composite premix is ​​injected into a standard denture base mold and placed in a constant temperature prepolymerization device. The initial temperature is set to 50 degrees Celsius, and low-speed constant temperature prepolymerization is carried out for 60 minutes to allow the resin molecules to initially cross-link and form, slowly release the polymerization stress, and avoid the volume shrinkage caused by rapid polymerization. S302: Vacuum pressure stabilization and degassing treatment. After prepolymerization, the mold is moved into the vacuum degassing equipment, the vacuum degree is set to 0.08 MPa, and it is kept at room temperature and pressure for 25 minutes to completely remove the tiny air bubbles inside the prepolymer, eliminate the pore defects after the base is formed, and improve the material density and antibacterial stability. S303: Gradient temperature curing molding, using a three-stage gradient temperature curing mode. The first stage heats up to 65 degrees Celsius and is kept at a constant temperature for 30 minutes; the second stage heats up to 75 degrees Celsius and is kept at a constant temperature for 40 minutes; the third stage heats up to 85 degrees Celsius and is kept at a constant temperature for 50 minutes. The temperature rises at a uniform rate throughout the process without sudden temperature changes, allowing the resin molecules to fully cross-link and cure, minimizing the overall polymerization shrinkage rate.

[0028] S4: Constant temperature aging stabilization post-treatment, used to eliminate residual stress inside the material and solidify and stabilize the antibacterial components, specifically including: S401: Constant temperature aging and shaping treatment. The solidified denture base semi-finished product is taken out of the mold and placed in a constant temperature and dust-free environment of 40 degrees Celsius for 12 hours to complete the relaxation of internal stress of the material, stabilize the molecular cross-linking structure, and completely eliminate the problem of deformation and shrinkage in the later stage. S402: Fine surface polishing treatment. The surface of the base is polished step by step with medical-grade polishing paste to remove excess material and fine burrs, keeping the surface of the base smooth and dense, sealing the surface micropores, effectively preventing oral bacteria from adhering, and achieving a dual antibacterial effect inside and out in combination with internal antibacterial components.

[0029] Example 3: like Figure 1 As shown, a low-shrinkage antibacterial denture base resin composite material comprises 79 parts of methyl methacrylate resin matrix, 10 parts of grafted modified nano silica, 7 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

[0030] A method for preparing a low-shrinkage antibacterial denture base resin composite material includes the following steps: S1: Refined pretreatment of functional composite powders, through activation, grafting, and purification processes, solves the problems of powder agglomeration, poor compatibility with resin matrices, and easy loss of antibacterial components. Specifically, this includes: S101: Nano silica hydroxyl activation treatment. Select high-purity silica powder with a particle size of 20 to 40 nanometers, place it in a constant temperature drying oven, set the temperature to 120 degrees Celsius, and continue drying for 4 hours to completely remove the moisture and impurities adsorbed on the powder surface. Place the dried powder into a high-speed stirred reactor, add anhydrous ethanol to immerse the powder, and stir at a uniform speed for 30 minutes. Set the stirring speed to 800 rpm to complete the powder dispersion pretreatment and ensure that the active hydroxyl groups are uniformly exposed on the powder surface. S102: In-situ acrylic acid grafting modification of nano-silica. Acrylic acid monomers were slowly added dropwise to a uniformly dispersed silica-ethanol system. The reaction vessel was sealed and heated to 75 degrees Celsius. The mixture was stirred at a constant temperature for 2.5 hours to allow the acrylic acid monomers to undergo a covalent grafting reaction with the active hydroxyl groups on the powder surface. After the reaction, the system was centrifuged and filtered to collect the solid powder. The powder was washed three times with anhydrous ethanol to remove unreacted monomer impurities. The powder was then dried at 80 degrees Celsius to a constant weight to obtain grafted modified nano-silica. This modified powder can form molecular bonds with the resin matrix, thereby reducing the shrinkage gap during resin polymerization from the source. S103: Purification and Refining of Chitosan-Zinc Composite Antibacterial Powder. The powder after chitosan and zinc acetate are composited and sintered in a fixed ratio is placed in an air jet mill for ultrafine grinding. The particle size is controlled to be uniformly maintained at 500 to 800 nanometers. After grinding, it is sieved with a 200-mesh standard sieve to remove large particle impurities. Then it is placed in a vacuum constant temperature environment and dried for 3 hours to obtain chitosan-zinc composite antibacterial powder with uniform purity and consistent particle size, ensuring uniform and stable antibacterial performance.

[0031] S2: The resin matrix is ​​homogeneously mixed in stages, using a stepwise doping and mixing process to achieve ultimate fusion between the modified powder in S1 and the resin matrix. Specifically, this includes: S201: Constant temperature softening treatment of resin matrix. Accurately weigh the methyl methacrylate resin matrix according to the mass fraction, put it into a sealed stirring container, set the constant temperature to 45 degrees Celsius, stir at low speed for 15 minutes to completely soften the solid resin matrix, fully stretch the internal molecular chains, and eliminate the original stress inside the matrix. S202: Two-powder stepwise doping and mixing: First, cross-linking modifiers are added to the softened resin matrix and stirred at a constant speed for 20 minutes to achieve molecular fusion of the modifiers and the matrix. Then, grafted modified nano-silica is added in two batches, and stirred for 15 minutes after each addition. Finally, chitosan zinc composite antibacterial powder is added all at once and stirred at high speed for 40 minutes. The stirring speed is set to 1200 rpm. Finally, a resin composite premix with no agglomeration and uniform composition is obtained.

[0032] S3: Gradient segmented prepolymer curing molding, using low-temperature prepolymerization, vacuum degassing, and gradient temperature curing for curing, specifically including: S301: Low-temperature and low-speed prepolymerization reaction. The resin composite premix is ​​injected into a standard denture base mold and placed in a constant temperature prepolymerization device. The initial temperature is set to 50 degrees Celsius, and low-speed constant temperature prepolymerization is carried out for 60 minutes to allow the resin molecules to initially cross-link and form, slowly release the polymerization stress, and avoid the volume shrinkage caused by rapid polymerization. S302: Vacuum pressure stabilization and degassing treatment. After prepolymerization, the mold is moved into the vacuum degassing equipment, the vacuum degree is set to 0.08 MPa, and it is kept at room temperature and pressure for 25 minutes to completely remove the tiny air bubbles inside the prepolymer, eliminate the pore defects after the base is formed, and improve the material density and antibacterial stability. S303: Gradient temperature curing molding, using a three-stage gradient temperature curing mode. The first stage heats up to 65 degrees Celsius and is kept at a constant temperature for 30 minutes; the second stage heats up to 75 degrees Celsius and is kept at a constant temperature for 40 minutes; the third stage heats up to 85 degrees Celsius and is kept at a constant temperature for 50 minutes. The temperature rises at a uniform rate throughout the process without sudden temperature changes, allowing the resin molecules to fully cross-link and cure, minimizing the overall polymerization shrinkage rate.

[0033] S4: Constant temperature aging stabilization post-treatment, used to eliminate residual stress inside the material and solidify and stabilize the antibacterial components, specifically including: S401: Constant temperature aging and shaping treatment. The solidified denture base semi-finished product is taken out of the mold and placed in a constant temperature and dust-free environment of 40 degrees Celsius for 12 hours to complete the relaxation of internal stress of the material, stabilize the molecular cross-linking structure, and completely eliminate the problem of deformation and shrinkage in the later stage. S402: Fine surface polishing treatment. The surface of the base is polished step by step with medical-grade polishing paste to remove excess material and fine burrs, keeping the surface of the base smooth and dense, sealing the surface micropores, effectively preventing oral bacteria from adhering, and achieving a dual antibacterial effect inside and out in combination with internal antibacterial components.

[0034] Based on the performance comparison of Examples 1 to 3 with the prior art, which is the conventional denture base resin, the performance comparison table is as follows: Example 1 Example 2 Example 3 Comparative Example Polymer volume shrinkage 2.8%-3.2% 1.5%-1.8% 1.3%-1.6% 1.6%-1.9% 30-day long-lasting antibacterial rate 62%-68% 94%-96% 92%-94% 96%-98% Bending strength 82MPa-86MPa 95MPa-98MPa 92MPa-95MPa 102MPa-106MPa 6-month long-term dimensional deformation rate 0.85%-0.95% 0.22%-0.28% 0.18%-0.23% 0.25%-0.30% Therefore, the performance of the low-shrinkage antibacterial denture base resin composite material prepared by this invention is superior to that of existing conventional denture base resins.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low-shrinkage antibacterial denture base resin composite material, comprising a methyl methacrylate resin matrix, a grafted modified nano-silica, a chitosan zinc composite antibacterial powder, and a crosslinking modification aid, characterized in that: The methyl methacrylate resin matrix, grafted modified nano-silica, chitosan zinc composite antibacterial powder, and crosslinking modification agent comprise, by weight, 79-85 parts of methyl methacrylate resin matrix, 6-10 parts of grafted modified nano-silica, 5-7 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

2. A low shrinkage antimicrobial denture resin composite material according to claim 1, characterized in that: The methyl methacrylate resin matrix consists of 82 parts, the grafted modified nano silica consists of 8 parts, the chitosan zinc composite antibacterial powder consists of 6 parts, and the crosslinking modification agent consists of 4 parts.

3. The low-shrinkage antibacterial denture base resin composite material according to claim 1, characterized in that: The composition includes 85 parts of methyl methacrylate resin matrix, 6 parts of grafted modified nano silica, 5 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

4. The low-shrinkage antibacterial denture base resin composite material according to claim 1, characterized in that: The composition includes 79 parts of methyl methacrylate resin matrix, 10 parts of grafted modified nano silica, 7 parts of chitosan zinc composite antibacterial powder, and 4 parts of crosslinking modification agent.

5. A method for preparing a low-shrinkage antibacterial denture base resin composite material, comprising using a low-shrinkage antibacterial denture base resin composite material as described in any one of claims 1-4, characterized in that: The following steps are included: S1: Refined pretreatment of functional composite powders, through activation, grafting and purification processes, solves the problems of powder agglomeration, poor compatibility with resin matrix and easy loss of antibacterial components; S2: The resin matrix is ​​homogeneously mixed in steps, and a step-by-step doping and mixing process is adopted to achieve the ultimate fusion between the modified powder in S1 and the resin matrix. S3: Gradient segmented prepolymer curing molding, which uses low-temperature prepolymerization, vacuum degassing and gradient temperature curing for curing; S4: Constant temperature aging stabilization post-treatment, used to eliminate residual stress inside the material and solidify and stabilize the antibacterial components.

6. The method for preparing a low-shrinkage antibacterial denture base resin composite material according to claim 5, characterized in that: Specifically, S1 includes: S101: Nano silica hydroxyl activation treatment. Select high-purity silica powder with a particle size of 20 to 40 nanometers, place it in a constant temperature drying oven, set the temperature to 120 degrees Celsius, and continue drying for 4 hours to completely remove the moisture and impurities adsorbed on the powder surface. Place the dried powder into a high-speed stirred reactor, add anhydrous ethanol to immerse the powder, and stir at a uniform speed for 30 minutes. Set the stirring speed to 800 rpm to complete the powder dispersion pretreatment and ensure that the active hydroxyl groups are uniformly exposed on the powder surface. S102: In-situ acrylic acid grafting modification of nano-silica. Acrylic acid monomer was slowly added dropwise to a uniformly dispersed silica-ethanol system. The reaction vessel was sealed and heated to 75 degrees Celsius. The mixture was stirred at a constant temperature for 2.5 hours to allow the acrylic acid monomer to undergo a covalent grafting reaction with the active hydroxyl groups on the powder surface. After the reaction was completed, the system was centrifuged and filtered to collect the solid powder. The powder was washed three times with anhydrous ethanol to remove unreacted monomer impurities. The powder was then dried at 80 degrees Celsius to constant weight to obtain grafted modified nano-silica. S103: Purification and Refining of Chitosan-Zinc Composite Antibacterial Powder. The powder after chitosan and zinc acetate are composited and sintered in a fixed ratio is placed in an air jet mill for ultrafine grinding. The particle size is controlled to be uniformly maintained at 500 to 800 nanometers. After grinding, it is sieved with a 200-mesh standard sieve to remove large particle impurities. Then it is placed in a vacuum constant temperature environment and dried for 3 hours to obtain chitosan-zinc composite antibacterial powder with uniform purity and consistent particle size, ensuring uniform and stable antibacterial performance.

7. The method for preparing a low-shrinkage antibacterial denture base resin composite material according to claim 5, characterized in that: Specifically, S2 includes: S201: Constant temperature softening treatment of resin matrix. Accurately weigh the methyl methacrylate resin matrix according to the mass fraction, put it into a sealed stirring container, set the constant temperature to 45 degrees Celsius, and stir at low speed for 15 minutes to completely soften the solid resin matrix. S202: Two-powder stepwise doping and mixing: First, cross-linking modifiers are added to the softened resin matrix and stirred at a constant speed for 20 minutes to achieve molecular fusion of the modifiers and the matrix. Then, grafted modified nano-silica is added in two batches, and stirred for 15 minutes after each addition. Finally, chitosan zinc composite antibacterial powder is added all at once and stirred at high speed for 40 minutes. The stirring speed is set to 1200 rpm. Finally, a resin composite premix with no agglomeration and uniform composition is obtained.

8. The method for preparing a low-shrinkage antibacterial denture base resin composite material according to claim 7, characterized in that: Specifically, S3 includes: S301: Low-temperature and low-speed prepolymerization reaction. The resin composite premix is ​​injected into a standard denture base mold, placed in a constant temperature prepolymerization device, and the initial temperature is set to 50 degrees Celsius. Low-speed constant temperature prepolymerization is carried out for 60 minutes to allow the resin molecules to initially cross-link and form. S302: Vacuum pressure stabilization and degassing treatment. After prepolymerization, the mold is moved into the vacuum degassing equipment, the vacuum degree is set to 0.08 MPa, and it is kept at room temperature and pressure for 25 minutes to completely remove the tiny air bubbles inside the prepolymer and eliminate the porosity defects after the base is formed. S303: Gradient temperature rise curing molding, using a three-stage gradient temperature rise mode for curing. The first stage heats up to 65 degrees Celsius and is kept at a constant temperature for 30 minutes; the second stage heats up to 75 degrees Celsius and is kept at a constant temperature for 40 minutes; the third stage heats up to 85 degrees Celsius and is kept at a constant temperature for 50 minutes. The temperature rises at a uniform rate throughout the process without sudden temperature changes, so that the resin molecules are completely cross-linked and cured.

9. The method for preparing a low-shrinkage antibacterial denture base resin composite material according to claim 8, characterized in that: Specifically, S4 includes: S401: Constant temperature aging and shaping treatment, the cured denture base semi-finished product is taken out of the mold and placed in a constant temperature and dust-free environment of 40 degrees Celsius for 12 hours to complete the relaxation of internal stress of the material; S402: Fine surface polishing treatment. Medical-grade polishing compound is used to polish the base surface step by step to remove excess material and fine burrs, keeping the base surface smooth and dense, and sealing the surface micropores.

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