Dental filling resin and method for preparing the same

Abstract

This invention discloses a dental filling resin and its preparation method, comprising: mixing cage-like oligomers with an antibacterial precursor under an anhydrous and inert gas environment, and carrying out partial reaction, retaining some ring-opening polymerizable groups, purifying, and obtaining functionalized cage-like prepolymer monomers; mixing cage-like prepolymer monomers with a resin matrix, stirring and shearing to form a homogeneous composite resin liquid; adding a cationic photoinitiator system to the composite resin liquid, performing vacuum degassing treatment, photoinitiation, releasing protic acid, and copolymerizing the resin matrix with the ring-opening polymerizable groups on the cage-like prepolymer monomers to form a cross-network resin with antibacterial as the cage-like core; thereby fixing the antibacterial functional groups on the polymer skeleton through the dual effects of chemical bonding and steric hindrance, avoiding the defect of leaving pores inside the material due to the dissolution and loss of traditional physical doped antibacterial agents.

Description

Technical Field

[0001] This invention relates to a dental filling resin, and more particularly to a dental filling resin and its preparation method. Background Technology

[0002] Dental filling resin is a commonly used material in oral restoration, used to fill caries defects to restore tooth shape and function. However, existing dental filling resins often face the problem of low mechanical strength in practical applications, especially during long-term use, their performance deteriorates significantly, affecting the durability and success rate of restorations. This problem is particularly prominent in resins containing antibacterial agents, because the introduction of antibacterial components often comes at the cost of sacrificing the mechanical integrity of the material.

[0003] Traditional dental resins typically contain various antibacterial agents to impart antibacterial properties, inhibiting microbial growth and preventing secondary caries. However, with prolonged use, these antibacterial agents are gradually released from the resin matrix, leading to the formation of micropores or voids within the material. This loss of antibacterial agents not only reduces the sustained antibacterial effect but also leaves structural defects in the resin. These pores become channels for the permeation of moisture and oral fluids, triggering a water absorption and degradation process in the resin matrix, causing the polymer network to soften or hydrolyze, further weakening the overall integrity of the material.

[0004] Under the influence of water absorption and degradation, the mechanical properties of resins decline sharply, becoming brittle, prone to fracture, and experiencing a dramatic drop in strength. This vicious cycle limits the clinical application of resins containing antibacterial agents, especially in the restoration of high-load-bearing areas such as posterior teeth. Therefore, developing a novel dental filling resin that can maintain effective antibacterial release without significantly compromising mechanical strength has become a critical challenge that urgently needs to be addressed in the field of dental materials. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a dental filling resin and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing dental filling resin, comprising the following steps:

[0007] S1: Under an anhydrous and inert gas environment, the cage-like oligomer is mixed with the antibacterial precursor and partially reacted, retaining some ring-opening polymerizable groups, and purified to obtain the functionalized cage-like prepolymer monomer.

[0008] S2: Mix the cage-like prepolymer monomer with the resin matrix, stir and shear to form a homogeneous composite resin liquid;

[0009] S3: A cationic photoinitiator system is added to the composite resin liquid, vacuum degassing is performed, and photoinitiation is carried out to release protic acid. The resin matrix and the ring-opening polymerizable groups on the cage-like prepolymer monomer undergo a copolymerization reaction to form a cross-network resin with antibacterial as the cage-like core.

[0010] In a preferred embodiment of the present invention, in S1, the cage-like oligomer is an octacyclooxygen or octaoxetane polyhedral oligomeric silsesquioxane; the antibacterial precursor is a long-chain quaternary ammonium salt compound with primary or secondary amine end groups; and the ring-opening polymerization group is an epoxy group or an oxetane group.

[0011] In a preferred embodiment of the present invention, the molar ratio of quaternary ammonium salt to cage-like oligomer is 1:1 to 2:1; part of the reaction is a nucleophilic ring-opening addition reaction carried out at 40-50°C in an anhydrous solvent;

[0012] The retained ring-opening polymerizable groups are:

[0013] The conversion rate of epoxy groups was monitored in real time by in-situ spectroscopy. When 6-7 unreacted, intact, active epoxy groups remained on each cage-like oligomer molecule, the reaction was quenched by cooling.

[0014] The reaction solution was precipitated and centrifuged or dialyzed to remove ungrafted free small molecule quaternary ammonium salts, and then freeze-dried under vacuum.

[0015] In a preferred embodiment of the present invention, in S2, the resin matrix contains a low-shrinkage cyclic resin monomer, and the cyclic resin monomer is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer.

[0016] The stirring and shearing process involves preparing a matrix liquid by stirring under heating conditions, then adding functionalized cage-like prepolymer monomers and dispersing them by ultrasonic oscillation for 1-2 hours.

[0017] In a preferred embodiment of the present invention, the amount of cage-like prepolymer monomer added to the composite resin liquid is 1-15 wt%;

[0018] The stirring and shearing heating temperature is 40-60℃, the stirring speed is 1000-3000r / min, the ultrasonic oscillation frequency is 20-40kHz, and the power is 100-500W.

[0019] In a preferred embodiment of the present invention, in step S3, the amount of the cationic photoinitiator system added to the composite resin solution is 0.1-3 wt%.

[0020] The cationic photoinitiation system is a multi-component system comprising a photosensitizer and a cationic initiator, wherein the mass ratio of the photosensitizer to the cationic initiator is 1:1-5;

[0021] The photosensitizer is selected from at least one of camphorquinone, 1-phenyl-1,2-propanedione, isopropylthioxanthrone, or acylphosphine oxides.

[0022] The cationic initiator is selected from at least one of diaryliodomonium salt, triarylthiomonium salt, or ferroceneium salt;

[0023] Vacuum degassing is performed under a negative pressure of -0.08 to -0.1 MPa, with each pressure holding lasting 10-20 minutes, and repeated 3-5 times to completely eliminate microbubbles.

[0024] A dental filling resin, comprising:

[0025] The resin has a three-dimensional interlocking network structure of polymer formed by cationic ring-opening copolymerization; the three-dimensional interlocking network structure uses cage-like oligomers as cross-linking nodes and ring-opening polymer segments as the network skeleton to covalently connect the cross-linking nodes.

[0026] Among them, the core of the cage-like oligomer has antimicrobial side chains covalently around it, and the cage-like oligomer utilizes the rigid cage-like geometric center to form a spatial steric confinement domain for the antimicrobial side chains.

[0027] In a preferred embodiment of the present invention, the cage-like oligomer is a polyhedral oligomeric silsesquioxane; the antibacterial side chain is a quaternary ammonium salt group with a long carbon chain; the polyhedral oligomeric silsesquioxane and the antibacterial side chain are linked by chemical bonds formed by a nucleophilic ring-opening addition reaction, forming a composite core with antibacterial source and force conduction function.

[0028] In a preferred embodiment of the present invention, the ring-opening polymer segment is a polyether or polyester segment formed by cationic ring-opening of a low-shrinkage cyclic resin monomer; the cyclic resin monomer is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer; the polyether or polyester segment can encapsulate multifunctional cage-like oligomers and antibacterial branches to form a polymer impermeable layer that blocks water penetration and prevents the sudden release of active substances.

[0029] In a preferred embodiment of the present invention, in the polymer three-dimensional interlocking network structure, each cage-like oligomer serves as a multi-branch crosslinking center, and its surface is radially connected to the open-ring polymer chain segment by covalent bonds; the polar crosslinking sites of the multifunctional cage-like oligomers and the non-polar antibacterial branches form an amphiphilic topology at the microscopic level, so that the crosslinking nodes are in a non-agglomerated dispersed state in the network skeleton and there is no phase separation interface.

[0030] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0031] (1) This invention provides a method for preparing dental filling resin. A polyhedral oligomeric silsesquioxane (POSS) cage-like core is covalently bonded to a long-chain quaternary ammonium salt antibacterial group, while retaining multiple epoxy groups on its surface as active sites. This core is then copolymerized with a low-shrinkage cyclic resin matrix via cationic ring-opening copolymerization to form a three-dimensional interlocking network. The antibacterial quaternary ammonium salt branches are firmly anchored to the rigid POSS cage-like core through chemical bonds. Simultaneously, the POSS itself deeply participates in the cross-linking of the polymerization network through the retained multiple ring-opening groups. Thus, through the dual effects of chemical bonding and steric hindrance, the resin is... The antibacterial functional groups are fixed on the polymer backbone, avoiding the defects of traditional physical doping antibacterial agents leaving pores inside the material due to dissolution and loss. This achieves a contact sterilization mechanism that does not rely on the release of active ingredients, and the antibacterial agent will not be lost, thus maintaining the long-term density of the resin matrix. Compared with the existing technology where the release of antibacterial agents leads to material porosity, water absorption and degradation, and a sharp decline in mechanical strength, the curing antibacterial mechanism of this invention cuts off the vicious chain reaction of loss-pore-degradation-brittleness at the source. The further effect is reflected in the excellent long-term mechanical properties.

[0032] (2) This invention provides a method for preparing dental filling resin. By selecting low-shrinkage cyclic resin monomers such as spirocyclic orthocarbonates as the matrix, and utilizing the epoxy groups retained on functionalized POSS to participate in the reaction simultaneously, the polymerization mechanism is changed from the traditional double bond addition to cationic ring-opening polymerization. During light curing, the cyclic monomers in the resin matrix and the epoxy groups on the POSS side chains undergo a ring-opening reaction under the catalysis of protic acid. The chemical bonds break from the closed cyclic structure and extend into a linear chain structure. This process is accompanied by a net increase in the molar volume of the monomer. This ring-opening expansion effect directly and actively offsets the physical volume shrinkage caused by the shortening of the intermolecular distance when the monomer is converted into a polymer. Compared with the inherently high volume shrinkage rate of free radical polymerization based on methacrylate monomers in the prior art, the ring-opening polymerization mechanism of this invention significantly reduces the polymerization shrinkage of the material from the essence of the chemical reaction, and further achieves extremely low volume shrinkage rate and excellent edge sealing. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The influence of the number of active epoxy groups retained by the functionalized POSS in the preferred embodiment of the present invention on the flexural strength of dental filling resin;

[0035] Figure 2 The effect of the number of active epoxy groups retained by the functionalized POSS in the preferred embodiment of the present invention on the polymerization shrinkage rate of dental filling resin;

[0036] Figure 3 This invention relates to the effect of the proportion of different cyclic monomer components in the resin matrix on the polymerization shrinkage rate of dental filling resin in a preferred embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0039] As shown in the figure, a method for preparing dental filling resin includes the following steps:

[0040] S1: Under an anhydrous and inert gas environment, the cage-like oligomer is mixed with the antibacterial precursor and partially reacted, retaining some ring-opening polymerizable groups, and purified to obtain the functionalized cage-like prepolymer monomer.

[0041] S2: Mix the cage-like prepolymer monomer with the resin matrix, stir and shear to form a homogeneous composite resin liquid;

[0042] S3: A cationic photoinitiator system is added to the composite resin liquid, vacuum degassing is performed, and photoinitiation is carried out to release protic acid. The resin matrix and the ring-opening polymerizable groups on the cage-like prepolymer monomer undergo a copolymerization reaction to form a cross-network resin with antibacterial as the cage-like core.

[0043] It should be noted that this invention proposes a preparation scheme for a molecular cage-like resin based on cationic ring-opening polymerization. By performing controlled partial modification on the multifunctional cage-like oligomer of polyhedral oligomeric silsesquioxane (POSS), some ring-opening polymerizable groups are retained, and functionalized cage-like prepolymers are purified and prepared. The cage-like prepolymers are introduced into a novel resin matrix containing low-shrinkage cyclic monomers of spirocyclic ortho-carbonates (SOCs). The van der Waals forces are broken by the synergistic effect of high shear force stirring and ultrasonic oscillation at a specific temperature, so that the functionalized cage-like prepolymers are compatible and non-agglomerated in the resin matrix. This avoids the phase separation interface defects that are easily generated by traditional inorganic fillers, and lays a flawless structural foundation for imparting extremely high mechanical strength to the material.

[0044] After adding a cationic photoinitiating system to the composite resin liquid and completing deep vacuum degassing, proton acids released by clinical light stimulation simultaneously trigger the ring-opening polymerizable groups retained on the novel resin matrix monomer and the cage-like prepolymer monomer, resulting in an indiscriminate cationic ring-opening copolymerization reaction. This ultimately constructs a three-dimensional interlocking polymer network with polyhedral cage-like cores as crosslinking nodes in situ. During this dynamic copolymerization process, the rigid polyhedral cage-like cores, acting as multi-branched crosslinking centers, are firmly covalently anchored in the three-dimensional network, forming a dense and deeply crosslinked interlocking network. This completely fills the microscopic pores left by traditional physical doping and prevents hydrolysis and plasticization degradation caused by moisture penetration. It also improves the resin system's toughness, compressive strength, and macroscopic flexural strength under chewing pressure, effectively preventing brittle fracture in the later stages of use.

[0045] Simultaneously, as the ring structure on the monomer opens synchronously, the chemical bonds change from closed rings to extended chains. This micro-expansion in volume offsets the physical shrinkage that occurs when the monomer is converted into a polymer, reducing the overall volume shrinkage rate of the resin to an extremely low level. This fundamentally eliminates the polymerization shrinkage stress that damages the bonding interface, completely blocks any potential leakage paths, and solves the long-standing problem of edge microleakage in clinical practice.

[0046] S1: Under an anhydrous and inert gas environment, the cage-like oligomer is mixed with the antibacterial precursor and partially reacted, retaining some ring-opening polymerizable groups, and purified to obtain the functionalized cage-like prepolymer monomer.

[0047] In a preferred embodiment of the present invention, in S1, the cage-like oligomer is an octacyclooxygen or octaoxetane polyhedral oligomeric silsesquioxane; the antibacterial precursor is a long-chain quaternary ammonium salt compound with primary or secondary amine end groups; and the ring-opening polymerization group is an epoxy group or an oxetane group.

[0048] In a preferred embodiment of the present invention, the molar ratio of quaternary ammonium salt to cage-like oligomer is 1:1 to 2:1; part of the reaction is a nucleophilic ring-opening addition reaction carried out at 40-50°C in an anhydrous solvent;

[0049] The retained ring-opening polymerizable groups are:

[0050] The conversion rate of epoxy groups was monitored in real time by in-situ spectroscopy. When 6-7 unreacted, intact, active epoxy groups remained on each cage-like oligomer molecule, the reaction was quenched by cooling.

[0051] The reaction solution was precipitated and centrifuged or dialyzed to remove ungrafted free small molecule quaternary ammonium salts, and then freeze-dried under vacuum.

[0052] It should be noted that in step S1, the core substrate cage-like oligomer in this embodiment is selected as octaepoxy or octaoxetane polyhedral oligomeric silsesquioxane (POSS). POSS is a nanoscale molecule with an organic-inorganic hybrid structure. POSS is derived from octaepoxy POSS such as EP0409 produced by Hybrid Plastics. Its interior is an extremely rigid inorganic core composed of Si-O-Si crosslinking of silicon-oxygen bonds, which is not easily deformed under stress and can provide extremely high mechanical support. Its exterior is connected to 8 highly reactive organic groups, such as epoxy groups or oxetane groups. These 8 ring-opening polymerizable groups provide abundant grafting sites for the subsequent crosslinking network.

[0053] The antibacterial precursor is a long-chain quaternary ammonium salt compound with primary or secondary amine end groups. Quaternary ammonium salts have bactericidal ability because their positive charge can pierce the negatively charged cell membrane of bacteria. However, in traditional processes, free quaternary ammonium salts are easily dissolved. This invention specifically selects quaternary ammonium salts with primary or secondary amine end groups because the nitrogen atom in the amine group has a lone pair of electrons, which is a nucleophile. It can undergo a specific nucleophilic ring-opening addition reaction with the epoxy group on the POSS side chain, thereby establishing an unbreakable covalent bond.

[0054] In this step, the reaction is carried out in an anhydrous and inert gas environment using an anhydrous solvent. This is because trace amounts of moisture can not only trigger side reactions of the active groups but also quench the cationic photoinitiation process in subsequent steps. Under medium-temperature conditions of 40-50°C, the quaternary ammonium salt and POSS are mixed in a molar ratio of 1:1 to 2:1. The conversion rate of the epoxy groups is monitored in real time using in-situ spectroscopy, i.e., Fourier transform infrared spectroscopy (FT-IR) or nuclear magnetic resonance (NMR). The reaction process is manually intervened and controlled. When 1 to 2 of the original 8 epoxy groups on each POSS molecule are grafted with the quaternary ammonium salt, thus ensuring the retention of 6-7 unreacted, intact, active epoxy groups, the reaction is immediately quenched by cooling.

[0055] The grafted quaternary ammonium salt is confined by the rigid inorganic cage structure of POSS, forming a huge steric hindrance. The 6-7 epoxy groups that are deliberately retained serve as chemical interfaces, fully preserving the polymerization activity of the molecule in subsequent large-scale network crosslinking. After the reaction is quenched, the molecule is purified by precipitation with ice-cold ether and centrifugation or dialysis bag dialysis to completely remove the ungrafted free small molecule quaternary ammonium salt. Finally, it is freeze-dried under vacuum to obtain a high-purity functionalized cage prepolymer monomer.

[0056] This process, through the purification and removal of free precursors combined with covalent bond confinement, fundamentally eliminates the disordered and rapid release effect of active substances in the early stages of use. As a result, without the loss of free molecules, the resin will not leave a large number of micropores as in traditional physical doping, thus maintaining the extreme density of the restoration matrix and blocking the vicious chain reaction of pore formation, water absorption, and degradation, thereby eliminating the hidden dangers for maintaining long-term high-strength mechanical properties.

[0057] Meanwhile, step S1 retains 6-7 ring-opening polymerizable groups. These 6-7 retained active epoxy groups are similar to 6-7 micro springs pre-embedded at the molecular scale. In the subsequent photocuring copolymerization stage, these cyclic groups are forced to open and extend into chains. The resulting micro-expansion in volume offsets the overall physical shrinkage of the resin, thereby ultimately achieving low shrinkage of the material, eliminating edge micro-leakage, and establishing a force transmission network.

[0058] In existing technologies, the antibacterial mechanism of polymer materials mostly relies on the release of active ingredients, such as metal ions or antibiotics. This release process leads to the loss of substances inside the material and the generation of a large number of micropores in the matrix. The antibacterial mechanism of the present invention is immobilized contact sterilization, that is, the antibacterial groups are anchored in the polymer network through chemical bonding, which inhibits or kills bacteria without releasing free molecules. This immobilized antibacterial mechanism is mainly achieved through the synergistic effect of electrostatic adsorption and physical penetration.

[0059] During the contact sterilization process, the material first adsorbs cariogenic bacteria through electrostatic interaction. The long-chain quaternary ammonium salt molecules grafted in the preparation step contain positively charged nitrogen atoms at their center. Cariogenic bacteria in the oral environment, such as Streptococcus mutans, have negatively charged surfaces due to their cell walls and cell membranes being rich in teichoic acid and phospholipid molecules. The positively charged quaternary ammonium salt groups on the resin surface adsorb the negatively charged cariogenic bacteria to the material surface through electrostatic attraction. Subsequently, the physical destruction stage begins. The hydrophobic long carbon chains contained in the quaternary ammonium salt structure interact with the lipophilic phospholipid bilayer of the bacterial cell membrane based on the principle of like dissolves like. When bacteria attach to the resin surface, the hydrophobic long carbon chains insert into and penetrate the bacterial phospholipid bilayer.

[0060] In this process, the inorganic rigid cage-like core of polyhedral oligomeric silsesquioxane (POSS) serves as the underlying physical support node. It confines and anchors the long carbon chain through covalent bonds, ensuring that the long carbon chain maintains conformational stability when penetrating the bacterial cell membrane, without deformation or shedding.

[0061] The continuous insertion of hydrophobic long carbon chains disrupts the structural integrity and osmotic pressure balance of bacterial cell membranes. This irreversible physical and mechanical damage leads to the leakage of vital substances such as cytoplasm, proteins, and nucleic acids from inside the bacteria, thereby causing bacterial cell lysis and inactivation.

[0062] Throughout the cell lysis process, quaternary ammonium salt molecules act only as contact-based disruptive media. They do not participate in the consumable chemical reaction, nor do they undergo chemical bond breakage or detachment. After the inactivated bacterial debris is detached due to the rinsing action of saliva or the friction of chewing, the long carbon chain structure covalently anchored to the polymer cross-linking network remains intact and continues to exert the same puncture and lysis effect on bacteria on the surface of the subsequently contacting material. This contact-based bactericidal mechanism enables the resin material to have long-lasting antibacterial ability without losing its internal components, while maintaining the density and mechanical continuity of the polymer's three-dimensional cross-linking network. This solves the technical contradiction that the release of traditional antibacterial components leads to a decrease in the mechanical strength of the material.

[0063] S2: Mix the cage-like prepolymer monomer with the resin matrix, stir and shear to form a homogeneous composite resin liquid;

[0064] In a preferred embodiment of the present invention, in S2, the resin matrix contains a low-shrinkage cyclic resin monomer, and the cyclic resin monomer is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer.

[0065] The stirring and shearing process involves preparing a matrix liquid by stirring under heating conditions, then adding functionalized cage-like prepolymer monomers and dispersing them by ultrasonic oscillation for 1-2 hours.

[0066] In a preferred embodiment of the present invention, the amount of cage-like prepolymer monomer added to the composite resin liquid is 1-15 wt%;

[0067] The stirring and shearing heating temperature is 40-60℃, the stirring speed is 1000-3000r / min, the ultrasonic oscillation frequency is 20-40kHz, and the power is 100-500W.

[0068] In the preparation process of the composite resin, step S2 replaces the bisphenol A derivative system used in traditional dental resins with a novel resin matrix containing low-shrinkage cyclic resin monomers. The cyclic resin monomers are selected from at least one of spirocyclic oxocarbonates (SOCs), lactone resin monomers, or alicyclic epoxy resin monomers. The spirocyclic oxocarbonates or alicyclic epoxy resin monomers are derived from commercially available ERL-4221 alicyclic epoxy monomers, whose molecular structures contain cyclic skeletons in a state of tension.

[0069] During the polymerization stage, these monomers undergo a ring-opening reaction, where the covalent bonds break from closed ring structures and extend into linear chains. The increase in molar volume caused by this chemical bond extension process physically offsets the volume contraction caused by the shortening of intermolecular van der Waals distance to covalent bond distance when the monomer is converted into a polymer.

[0070] After preparing the matrix liquid by stirring under heating conditions, functionalized cage-like prepolymer monomers are added to the composite resin liquid at a mass fraction of 1 wt% to 15 wt%. This mass fraction range sets the distribution density of inorganic crosslinking nodes in the organic matrix. If the mass fraction is lower than this range, it is difficult to form a continuous force transmission network after curing. If the mass fraction is higher than this range, it will increase the fluid viscosity of the system, exceeding the range of rheological parameters required for dental clinical filling operations.

[0071] Functionalized cage-like prepolymer monomers can achieve homogeneous distribution without the need for additional coupling agents. The distribution mechanism originates from the surface chemical structure of the prepolymer monomer. The prepolymer monomer surface contains coexisting polar ring-opening polymerizable groups and grafted nonpolar hydrophobic long carbon chains, forming an amphiphilic topology. This amphiphilic characteristic modulates the surface energy of the inorganic cage-like core, enabling it to achieve thermodynamic compatibility with the cyclic resin monomer matrix with similar polarity, thus possessing the physicochemical premise of atomic-level dispersion.

[0072] To overcome the tendency of agglomeration between particles, a physical synergistic treatment process of heating, mechanical shearing and ultrasonic oscillation is adopted in this step. By heating the composite system to 40-60℃, the kinematic viscosity of the cyclic resin monomer is reduced, the fluidity of the liquid phase is improved, and the temperature is below the threshold range for initiating monomer thermal polymerization.

[0073] Under reduced viscosity conditions, high-shear mechanical stirring is performed at a speed of 1000-3000 r / min to induce macroscopic convection in the liquid system and complete the initial mixing of the two phases. Subsequently, ultrasonic oscillation treatment with a frequency of 20-40 kHz and a power of 100-500 W is applied for 1 to 2 hours. When the ultrasonic waves propagate in the liquid resin matrix, they induce cavitation. The high-speed microjet and local shear force generated when the cavitation microbubbles close and collapse directly act between the prepolymer monomer molecules, overcoming the van der Waals forces between particles and forcibly depolymerizing them to achieve homogeneous dispersion in the liquid resin matrix.

[0074] Step S2 utilizes an amphiphilic compatibility mechanism and a physical shear synergistic process to achieve a highly dispersed state of functionalized cage-like prepolymer monomers within a low-shrinkage resin matrix. This eliminates the phase separation interface defects and internal structural pores caused by inorganic filler agglomeration in traditional composite resins. After photocuring, this interface-free homogeneous mixed system avoids the formation of stress concentration sites within the material, maintaining the stability of the macroscopic compressive and flexural strength of the polymer system. Simultaneously, the resin matrix monomers containing cyclic structures and the prepolymer monomers with similar ring-opening groups achieve a molecular-level mixed state within the system, ensuring that the subsequent cationic ring-opening copolymerization reaction can proceed in a homogeneous environment without phase interfaces. This ensures the uniform occurrence of three-dimensional network crosslinking and polymerization volume expansion compensation effects throughout the resin material.

[0075] S3: A cationic photoinitiator system is added to the composite resin liquid, vacuum degassing is performed, and photoinitiation is carried out to release protic acid. The resin matrix and the ring-opening polymerizable groups on the cage-like prepolymer monomer undergo a copolymerization reaction to form a cross-network resin with antibacterial as the cage-like core.

[0076] In a preferred embodiment of the present invention, in step S3, the amount of the cationic photoinitiator system added to the composite resin solution is 0.1-3 wt%.

[0077] The cationic photoinitiation system is a multi-component system comprising a photosensitizer and a cationic initiator, wherein the mass ratio of the photosensitizer to the cationic initiator is 1:1-5;

[0078] The photosensitizer is selected from at least one of camphorquinone, 1-phenyl-1,2-propanedione, isopropylthioxanthrone, or acylphosphine oxides.

[0079] The cationic initiator is selected from at least one of diaryliodomonium salt, triarylthiomonium salt, or ferroceneium salt;

[0080] Vacuum degassing is performed under a negative pressure of -0.08 to -0.1 MPa, with each pressure holding lasting 10-20 minutes, and repeated 3-5 times to completely eliminate microbubbles.

[0081] In the preparation process of the composite resin liquid, step S3, which is a vacuum degassing treatment performed before or simultaneously with the introduction of the photoinitiation system, aims to eliminate the microbubbles that are entrained into the liquid matrix due to mechanical stirring and high-frequency ultrasonic cavitation in step S2. The operating parameters of this degassing process are set to a negative pressure environment of -0.08 to -0.1 MPa, with a single pressure holding time of 10 to 20 minutes, and 3 to 5 repeated vacuum cycles. The above negative pressure parameters exceed the saturated vapor pressure threshold of the dissolved gas inside the system, causing the microbubbles to expand in volume, float, and rupture and be discharged. This degassing process eliminates physical pore defects inside the cured resin and avoids stress concentration and fatigue crack initiation caused by internal microbubbles under macroscopic stress.

[0082] In step S3, a cationic photoinitiator system with a mass fraction of 0.1 wt% to 3 wt% is added to the homogeneous composite resin solution. This addition range is set; too low a mass fraction will result in insufficient initiation proton concentration, leading to incomplete curing of the resin substrate; too high a mass fraction will trigger a violent chain termination reaction, resulting in a decrease in the molecular weight of the crosslinked network and potentially causing a yellowish tint to the resin. This cationic photoinitiator system is a multi-component composite system containing a photosensitizer and a cationic initiator, with their mass ratio controlled between 1:1 and 1:5. The photosensitizer is selected from camphorquinone (CQ), whose light absorption peak matches the 470 nm blue light commonly used in dentistry, 1-phenyl-1,2-propanedione (PPD), isopropylthioxanthone (ITX), or at least one of acylphosphine oxide compounds such as TPO and BAPO. Its physicochemical function is to undergo electronic transitions into an excited state under irradiation with a specific wavelength of light source.

[0083] The cationic initiator is selected from at least one of diaryliodonium salt, triarylthionium salt, or ferroceneium salt. The photosensitizer in the excited state undergoes an intermolecular electron transfer reaction with the cationic initiator, which promotes homolytic or heterolytic cleavage of the iodonium salt or thionium salt structure, thereby releasing Brønsted acid, i.e. protic acid, which has strong catalytic activity.

[0084] The protic acid generated in situ within the system acts as the initiating active center for cationic polymerization, directly triggering the ring-opening copolymerization reaction within the composite system. This protic acid not only attacks the low-shrinkage cyclic resin monomers in the resin matrix, such as the ether or ester bonds in spirocyclic ortho-carbonates or lactone monomers, causing them to open their rings, but also attacks the ring-opening polymerizable groups, such as epoxy groups or oxocyclic butyl groups, retained on the side chains of the polyhedral cage oligomer (POSS) in step S1.

[0085] Since both the matrix monomer and the cage-like prepolymer monomer contain cyclic polymerizable groups sensitive to protic acids, they undergo cationic ring-opening copolymerization under the catalysis of protic acids. During the copolymerization process, the cyclic structure of the monomer is continuously broken and linear polyether or polyester polymer segments are formed. These segments are covalently bonded to the cage-like prepolymer monomers uniformly distributed in the matrix. Through the extension and interweaving of chemical bonds, the liquid phase system is transformed in situ into a three-dimensional interlocking network of polymers with a polyhedral cage-like core with antibacterial branches as multi-branch crosslinking nodes.

[0086] The photo-initiated cationic ring-opening copolymerization mechanism in step S3 involves the ring-opening polymerization of matrix monomers with cyclic structures and cage-like prepolymers. During this process, the tensile-bound closed-ring covalent bonds break and transform into linear chain structures. The increase in monomer molar volume resulting from this conformational change macroscopically offsets the volume shrinkage caused by the shortening of intermolecular van der Waals distance to covalent bond distance when monomers are converted into polymeric segments. The ring-opening expansion effect significantly reduces the polymerization shrinkage rate of the final molded resin, eliminating residual tensile stress at the tooth bonding interface caused by material shrinkage and blocking physical factors that could lead to marginal microleakage and postoperative sensitivity.

[0087] In terms of improving mechanical strength, the highly rigid POSS cage-like core fully participates in network construction through its retained ring-opening groups, forming high-density covalent cross-linked nodes. This three-dimensional interlocking network realizes the uniform transmission of stress between the polymer matrix and inorganic nodes. At the same time, the polyether or polyester network generated by cationic ring-opening polymerization has the characteristics of high cross-linking density and low water absorption, which restricts the penetration of oral environment moisture into the resin interior, inhibits the hydrolytic degradation and plasticization effect of polymer chain segments, and maintains the macroscopic compressive strength and flexural strength of composite resin under long-term service conditions.

[0088] A dental filling resin, comprising:

[0089] The resin has a three-dimensional interlocking network structure of polymer formed by cationic ring-opening copolymerization; the three-dimensional interlocking network structure uses cage-like oligomers as cross-linking nodes and ring-opening polymer segments as the network skeleton to covalently connect the cross-linking nodes.

[0090] Among them, the core of the cage-like oligomer has antimicrobial side chains covalently around it, and the cage-like oligomer utilizes the rigid cage-like geometric center to form a spatial steric confinement domain for the antimicrobial side chains.

[0091] In a preferred embodiment of the present invention, the cage-like oligomer is a polyhedral oligomeric silsesquioxane; the antibacterial side chain is a quaternary ammonium salt group with a long carbon chain; the polyhedral oligomeric silsesquioxane and the antibacterial side chain are linked by chemical bonds formed by a nucleophilic ring-opening addition reaction, forming a composite core with antibacterial source and force conduction function.

[0092] In a preferred embodiment of the present invention, the ring-opening polymer segment is a polyether or polyester segment formed by cationic ring-opening of a low-shrinkage cyclic resin monomer; the cyclic resin monomer is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer; the polyether or polyester segment can encapsulate multifunctional cage-like oligomers and antibacterial branches to form a polymer impermeable layer that blocks water penetration and prevents the sudden release of active substances.

[0093] In a preferred embodiment of the present invention, in the polymer three-dimensional interlocking network structure, each cage-like oligomer serves as a multi-branch crosslinking center, and its surface is radially connected to the open-ring polymer chain segment by covalent bonds; the polar crosslinking sites of the multifunctional cage-like oligomers and the non-polar antibacterial branches form an amphiphilic topology at the microscopic level, so that the crosslinking nodes are in a non-agglomerated dispersed state in the network skeleton and there is no phase separation interface.

[0094] The dental filling resin of this invention is characterized by having a three-dimensional interlocking polymer network formed by cationic ring-opening copolymerization. The basic topology of this network consists of cage-like oligomers as crosslinking nodes and open-ring polymer segments as the network skeleton, with the nodes and skeleton connected by covalent bonds. The antibacterial function of the resin is provided by antibacterial side chains covalently grafted onto the periphery of the cage-like oligomer core. The rigid geometric center of the cage-like oligomer forms a physical spatial steric hindrance confinement on the range of motion of the antibacterial side chains. This confinement structure solidifies the antibacterial groups in the polymer network, preventing their release and thus avoiding the formation of micropores in the resin matrix due to material loss, maintaining the density and structural integrity of the polymer network.

[0095] In a preferred embodiment, the cage-like oligomer is a polyhedral oligomeric silsesquioxane (POSS), which has an organic-inorganic hybrid nanostructure with a highly rigid silicon-oxygen (Si-O-Si) inorganic core and a reactive organic functional group shell, and the antibacterial side chain is a quaternary ammonium salt (QAS) group with a long carbon chain.

[0096] POSS and antibacterial side chains are linked by covalent bonds formed through nucleophilic ring-opening addition reactions to form a composite nanocore. The quaternary ammonium salt groups in the composite core serve as an immobilized antibacterial source, inhibiting bacteria through a contact sterilization mechanism. Furthermore, the highly rigid POSS inorganic core acts as a stress transmission node, dispersing stress when the material is under stress and improving the overall mechanical strength.

[0097] The backbone of the network, namely the ring-opening polymer segments, is a polyether or polyester segment formed by the cationic ring-opening reaction of low-shrinkage cyclic resin monomers. The cyclic resin monomers are selected from at least one of spirocyclic ortho-carbonates (SOCs), lactone resin monomers, or alicyclic epoxy resin monomers. The volume expansion effect accompanying the ring-opening polymerization process offsets the polymerization shrinkage of the material. The polyether or polyester network formed by these monomers has the physical properties of high crosslinking density and low water absorption rate, which can tightly wrap the cage-like oligomers and their grafted antibacterial branches. This wrapping structure forms a polymer impermeable layer at the microscopic level. Its physical function is to block the penetration of moisture from the oral environment into the resin interior, inhibit the hydrolytic degradation and plasticization effect of the polymer segments, thereby maintaining the long-term mechanical stability of the resin material.

[0098] In the fine structure of the polymer three-dimensional interlocking network, each cage-like oligomer serves as a multi-branch crosslinking center. Its surface is radially connected to open-ring polymer segments through multiple covalent bonds, forming a highly crosslinked topology. The polar crosslinking sites on the surface of the cage-like oligomers, the functional groups participating in network construction, and the non-polar antibacterial branches constitute an amphiphilic topology at the microscopic level. This amphiphilic structure enables the crosslinking nodes to achieve thermodynamic compatibility in the network skeleton, exhibiting a non-agglomerated molecular-level dispersion state, and there is no phase separation interface inside the material. This homogeneous structure without interface defects eliminates stress concentration sources inside the material, which is the structural basis for the high compressive strength, high flexural strength, and fatigue fracture resistance of this dental filling resin.

[0099] Example 1:

[0100] In an inert nitrogen atmosphere and an anhydrous reaction environment, octacyclic polyhedral oligomeric silsesquioxane (POSS) as a cage-like oligomer was dissolved in anhydrous tetrahydrofuran solvent. Hexadecyl dimethyl ammonium chloride with primary amine end groups was slowly added dropwise to the POSS solution at a molar ratio of 1.5:1 to POSS.

[0101] Nucleophilic ring-opening addition reaction was carried out at a temperature of 40℃ to 50℃, and the changes in the characteristic peaks of epoxy groups were monitored in real time using in-situ Fourier transform infrared spectroscopy. When an average of 7 unreacted, intact, active epoxy groups were detected on each POSS molecule, the reaction was immediately quenched by cooling. The reaction product was subjected to multiple precipitation and centrifugation in ice-cold ether to completely remove unreacted free quaternary ammonium salt molecules. After vacuum freeze-drying, pure functionalized cage-like prepolymer monomers with quaternary ammonium salt grafted on the surface and retaining multiple active epoxy groups were obtained.

[0102] Spirocyclic o-carbonates (SOCs) and alicyclic epoxy monomers were mixed at a mass ratio of 7:3 to form a low-shrinkage resin matrix free of bisphenol A derivatives. The functionalized cage-like prepolymer powder obtained in the previous step was added to the resin matrix at a mass fraction of 10 wt% in the final composite resin solution. Preliminary mixing was achieved by high-shear mechanical stirring at 2000 rpm under heating conditions of 50°C. The mixture was then transferred to an ultrasonic treatment device and subjected to ultrasonic oscillation treatment at a frequency of 30 kHz and a power of 300 W for 1.5 hours. Through cavitation, the functionalized cage-like prepolymers were atomically homogeneously dispersed in the resin matrix, forming a clear and transparent composite resin solution.

[0103] In a light-protected environment, a multi-component photoinitiation system consisting of camphorquinone (CQ) as a photosensitizer and diphenyliodonium hexafluorophosphate as a cationic initiator was added to the composite resin solution. The total addition amount of the system in the composite resin solution was 1.5 wt%, and the mass ratio of photosensitizer to cationic initiator was 1:3. The resin solution with the initiation system was placed in a vacuum degassing machine and subjected to four repeated vacuum treatments under a negative pressure of -0.09 MPa to completely eliminate microbubbles in the system. The resin was then photoinitiated using a dental blue light curing lamp with a center wavelength of 470 nm. The light energy caused the photosensitizer and cationic initiator to undergo an electron transfer reaction, releasing protic acid in situ. This protic acid simultaneously catalyzed a cationic ring-opening copolymerization reaction between the spirocyclic ortho-carbonate in the resin matrix and the epoxy groups retained on the functionalized cage-like prepolymer monomers, ultimately forming a solid three-dimensional interlocking network structure.

[0104] The dental filling resin prepared in this way exhibits a three-dimensional interlocked network of polyether / polyester formed by cationic ring-opening copolymerization in its microstructure. This network uses POSS as a highly rigid multi-branched crosslinking node and polymer segments formed after ring-opening as the network skeleton. The nodes and skeleton are connected radially by covalent bonds. Quaternary ammonium salt groups covalently grafted to the periphery of the POSS core are confined by a rigid cage-like geometric center, serving as an immobilized antibacterial source. At the same time, the polar epoxy groups and non-polar long carbon chain quaternary ammonium salt groups present on the POSS surface constitute an amphiphilic topology, which makes these crosslinking nodes in a non-agglomerated molecular-level dispersion state in the network skeleton. There is no phase separation interface inside the material. The polyether / polyester segments formed by ring-opening of monomers such as SOCs are dense and have low water absorption, tightly wrapping the POSS composite core and forming a polymer waterproof layer that blocks water penetration, ensuring the long-term mechanical stability of the material.

[0105] Example 2:

[0106] The method of introducing antibacterial groups was changed, and all components and proportions, such as resin matrix and photoinitiation system, were kept consistent with those in Example 1. The difference was that functionalized cage-like prepolymer monomers were not used. Instead, 10 wt% of filler was replaced with a physical mixture of unfunctionalized octa-epoxy POSS powder and an equivalent dose of free hexadecyl dimethyl ammonium chloride powder. The preparation process also adopted ultrasonic synergistic shearing treatment.

[0107] Example 3:

[0108] By removing the POSS crosslinking nodes, all components and proportions, including the resin matrix and photoinitiation system, are kept consistent with those in Example 1. The difference is that no POSS or quaternary ammonium salt is added, and a low-shrinkage resin matrix cured body is prepared.

[0109] Example 4:

[0110] The polymerization mechanism of the resin matrix was changed. All components and proportions, such as functionalized cage-like prepolymer monomers and photoinitiator systems, were kept consistent with those in the experimental group. The difference was that the low-shrinkage SOCs / epoxy resin matrix was replaced with a traditional, high-shrinkage free radical polymerized resin matrix, namely Bis-GMA / TEGDMA, at a mass ratio of 7:3. Correspondingly, the cationic photoinitiator system was replaced with an equivalent concentration of the free radical photoinitiator system, namely camphorquinone / amine.

[0111] Example 5:

[0112] By altering the polymerization participation of POSS, all components and proportions, including the low-shrinkage SOCs / epoxy resin matrix and photoinitiation system, were kept consistent with the experimental group. The difference was that instead of using functionalized cage-like prepolymer monomers, they were replaced with an equal mass fraction (10wt%) of nano-silica particles with silanized inert surface treatment.

[0113] Experiment 1:

[0114] Three sets of material test strips were prepared according to ISO 4049 standard. Each set of test strips was divided into two batches. One batch was directly subjected to mechanical property testing, while the other batch was aged in artificial saliva at 37°C for 30 days, followed by the same mechanical property testing to simulate the long-term oral service environment. The material's resistance to bending deformation and fracture was then tested using the three-point bending method to verify its bending strength. Details are shown in Table 1 and [Table data would be inserted here]. Figure 1 .

[0115] Table 1

[0116] Number of groups / Amount added / wt% Initial bending strength / MPa Bending strength after 30 days / MPa Strength retention rate / % Example 1 7 10 165 160 97.0 Example 2 - 10wt%POSS + Free QAS 115 75 65.2 Example 3 - 0 98 90 94.7 Example 6 7 5 145 138 95.2 Example 7 7 15 170 162 95.3 Example 8 4 5 135 125 92.6 Example 9 4 10 150 141 94.0 Example 10 4 15 155 145 93.5 Example 11 1 5 120 108 90.0 Example 12 1 10 130 118 90.8 Example 13 1 15 135 123 91.1

[0117] Analysis of the experimental data shows that, under the condition of fixed addition of functionalized cage prepolymer monomer, the surface grafting density, i.e. the number of active ring-opening polymerizable groups retained on polyhedral oligomeric silsesquioxane (POSS), is the key variable that determines the crosslinking density of the polymer three-dimensional network. As the number of active epoxy groups retained on each POSS molecule increases, the initial flexural strength and the flexural strength after aging of the finally cured resin both show a significant increasing trend.

[0118] The mechanism is that the more active ring-opening polymerizable groups are retained, the more functional crosslinking centers each POSS molecule can serve as in the cationic ring-opening copolymerization reaction, forming more covalent bonds with the surrounding resin matrix segments. This leads to an increase in the crosslinking density of the final three-dimensional interlocking network, resulting in a more compact network structure. At the macroscopic mechanical level, the higher crosslinking density enhances the polymer network's resistance to deformation and improves the efficiency of stress transfer between the inorganic rigid core and the organic polymer segments, thus manifesting as an increase in the initial mechanical strength of the material. At the same time, a denser network structure can more effectively hinder the penetration and diffusion of water molecules and inhibit the hydrolytic degradation and plasticization effect of the polymer matrix. Therefore, the material can still maintain high mechanical strength after long-term artificial saliva aging.

[0119] Secondly, under the premise of fixed grafting density on the surface of functionalized cage prepolymer monomer, its added mass fraction in the resin matrix affects the volume fraction of inorganic reinforcing phase in the composite material. When the amount of functionalized POSS added increases within an appropriate range, the initial and aging mechanical strength of the material are significantly improved.

[0120] The mechanism lies in the fact that increasing the amount of POSS is equivalent to increasing the distribution density of high-rigidity cross-linked nodes in the three-dimensional network, thereby increasing the modulus and strength of the entire polymer system. However, this reinforcing effect does not increase linearly indefinitely. When the amount of POSS exceeds a certain threshold, the increase in mechanical strength tends to plateau significantly, and its long-term stability may even decrease slightly. This is mainly because excessively high nanoparticle concentrations drastically increase the viscosity of the composite resin solution, which not only affects clinical operability but also increases the probability of local self-aggregation during dispersion, introducing microscopic defects into the material. Furthermore, excessive introduction of rigid nodes into the limited organic matrix leads to increased brittleness and decreased toughness of the entire network system, which is detrimental to the long-term service stability of the material under complex stress environments.

[0121] Experiment 2:

[0122] Resins were prepared according to Examples 1, 4, and 5, respectively. Density bottle experiments were conducted by varying the SOCs:Epoxy mass ratio and the number of retained active epoxy groups in POSS in Example 1. Polymerization shrinkage was tested, and edge microleakage was also performed. Specifically:

[0123] Healthy, caries-free, and crack-free extracted human molars were selected and preserved in a 0.1% thymosin solution. Standardized Class V cavities were prepared on the buccal side of the teeth, with the occlusal margin located in the enamel and the gingival margin located at the cementum-dentin junction or dentin.

[0124] Using a standardized universal adhesive system, all cavities were acid-etched, primed, and then bonded. The various resin materials were then layered into the cavities, with each layer light-cured. After filling, the restorations were trimmed and polished. Each set of materials was used to fill at least 15 teeth.

[0125] The filled tooth sample was completely immersed in distilled water and placed in a thermal cycler for 5000 high and low temperature cycles. The cycle temperature was set at 5℃ and 55℃, with each temperature point held for 30 seconds and a transfer time of 5 seconds, to simulate drastic changes in oral temperature.

[0126] After the thermal cycling is completed, the apical foramen of the tooth is sealed with paraffin or resin, two layers of acid-resistant nail polish are applied to the tooth surface, leaving a 1 mm wide circumferential margin around the restoration uncovered, and the tooth sample is immersed in a 2% methylene blue dye solution for 24 hours at a temperature maintained at 37°C.

[0127] After dye penetration, the tooth sample was thoroughly rinsed to remove excess dye from the surface. The tooth sample was then embedded in transparent acrylic resin. After the resin cured, buccal and lingual longitudinal sections were cut along the center of the restoration using a low-speed diamond cutter. The sections were observed under a stereomicroscope, and the maximum penetration depth of the dye along the restoration-tooth tissue interface was measured. See Table 2 for details. Figure 2 and Figure 3 .

[0128] Table 2

[0129] SOCs: Epoxy mass ratio POSS retains the number of active epoxy groups / Volumetric polymerization shrinkage rate / % Edge microleakage depth / μm Example 1 7:3 7 0.5 0 Example 4 - - 4.00 132 Example 5 7:3 - 1.5 51 Example 14 8:2 7 0.85 10 Example 15 8:2 4 1.10 25 Example 16 8:2 1 1.35 40 Example 17 7:3 4 0.80 15 Example 18 7:3 1 1.15 30 Example 19 6:4 7 0.75 5 Example 20 6:4 4 1.00 20 Example 21 6:4 1 1.25 35

[0130] Analysis of the experimental data shows that, under the condition of a fixed number of active epoxy groups in the functionalized cage-like prepolymer monomers, the proportion of different cyclic monomer components in the resin matrix directly affects the inherent volume expansion during polymerization. As the content of spirocyclic orthocarbonates (SOCs) with higher expansion contribution increases in the matrix, the volume polymerization shrinkage rate of the composite resin generally shows a trend of first decreasing and then slightly increasing, reaching a minimum value at a specific ratio, and the corresponding edge microleakage depth also reaches the optimal level.

[0131] The mechanism lies in the fact that SOCs monomers have a double ring-opening characteristic, and the molar volume increase generated during cationic ring-opening polymerization is significantly higher than that of alicyclic epoxy monomers. Therefore, moderately increasing the proportion of SOCs can enhance the volume expansion effect of the matrix itself, thereby more effectively offsetting the physical shrinkage caused by the shortening of the intermolecular distance. However, when the proportion of SOCs exceeds the optimized range, it may lead to excessively high overall viscosity of the system, affecting the molecular diffusion and reaction conversion rate of the polymerizable monomers, thus limiting the full play of the expansion compensation effect and causing a slight rebound in the polymerization shrinkage rate. This indicates that the optimal ratio of cyclic monomers in the resin matrix needs to comprehensively consider their inherent expansion contribution and polymerization kinetics factors.

[0132] Secondly, under the condition of fixed resin matrix ratio, the number of active epoxy groups retained on the surface of functionalized cage prepolymer monomers also determines its overall volume expansion compensation effect. As the number of active epoxy groups retained on polyhedral oligomeric silsesquioxane (POSS) increases from less to more, the volume polymerization shrinkage rate of composite resin shows a significant downward trend, and the corresponding edge microleakage depth also decreases significantly.

[0133] The mechanism lies in the fact that the more active epoxy groups retained on the POSS molecule, the more ring-opening expansion sites each POSS molecule can provide during cationic ring-opening copolymerization. This multi-point ring-opening expansion effect from the nanoscale acts on the entire polymer network in a dispersed and uniform manner, which can more precisely and effectively offset the polymerization volume shrinkage of the resin matrix. This synergistic volume compensation mechanism enables the material to achieve extremely low polymerization shrinkage rates, even reaching a near-zero shrinkage state. When the polymerization shrinkage rate drops to an extremely low level, the shrinkage stress generated by the polymer on the bonding interface during the curing process is greatly eliminated, thereby fundamentally avoiding bonding failure caused by shrinkage stress and completely eliminating the occurrence of edge microleakage.

[0134] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a dental filling resin, characterized by, Includes the following steps: S1: Under an anhydrous and inert gas environment, the cage-like oligomer is mixed with the antibacterial precursor and partially reacted, retaining some ring-opening polymerizable groups, and purified to obtain the functionalized cage-like prepolymer monomer. S2: Mix the cage-like prepolymer monomer with the resin matrix, stir and shear to form a homogeneous composite resin liquid; S3: A cationic photoinitiator system is added to the composite resin liquid, vacuum degassing is performed, and photoinitiation is carried out to release protic acid. The resin matrix and the ring-opening polymerizable groups on the cage-like prepolymer monomer undergo a copolymerization reaction to form a cross-network resin with antibacterial as the cage-like core.

2. The method for preparing a dental filling resin according to claim 1, characterized in that: In S1, the cage-like oligomer is an octacyclooxygen or octaoxetane polyhedral oligomeric silsesquioxane; the antibacterial precursor is a long-chain quaternary ammonium salt compound with primary or secondary amine end groups; and the ring-opening polymerization group is an epoxy group or an oxetane group.

3. The method for preparing a dental filling resin according to claim 2, characterized in that: The molar ratio of quaternary ammonium salt to cage-like oligomer is 1:1 to 2:1; part of the reaction is a nucleophilic ring-opening addition reaction carried out at 40-50℃ in an anhydrous solvent; The retained ring-opening polymerizable groups are: The conversion rate of epoxy groups was monitored in real time by in-situ spectroscopy. When 6-7 unreacted, intact, active epoxy groups remained on each cage-like oligomer molecule, the reaction was quenched by cooling. The reaction solution was precipitated and centrifuged or dialyzed to remove ungrafted free small molecule quaternary ammonium salts, and then freeze-dried under vacuum.

4. The method for preparing a dental filling resin according to claim 1, characterized in that: In S2, the resin matrix contains a low-shrinkage cyclic resin monomer, which is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer. The stirring and shearing process involves preparing a matrix liquid by stirring under heating conditions, then adding functionalized cage-like prepolymer monomers and dispersing them by ultrasonic oscillation for 1-2 hours.

5. The method for preparing a dental filling resin according to claim 4, characterized in that: The amount of the cage-like prepolymer monomer added to the composite resin solution is 1-15 wt%. The stirring and shearing heating temperature is 40-60℃, the stirring speed is 1000-3000r / min, the ultrasonic oscillation frequency is 20-40kHz, and the power is 100-500W.

6. The method for preparing a dental filling resin according to claim 1, characterized in that: In step S3, the amount of the cationic photoinitiator system added to the composite resin solution is 0.1-3 wt%. The cationic photoinitiation system is a multi-component system comprising a photosensitizer and a cationic initiator, wherein the mass ratio of the photosensitizer to the cationic initiator is 1:1-5; The photosensitizer is selected from at least one of camphorquinone, 1-phenyl-1,2-propanedione, isopropylthioxanthrone, or acylphosphine oxides. The cationic initiator is selected from at least one of diaryliodomonium salt, triarylthiomonium salt, or ferroceneium salt; Vacuum degassing is performed under a negative pressure of -0.08 to -0.1 MPa, with each pressure holding lasting 10-20 minutes, and repeated 3-5 times to completely eliminate microbubbles.

7. A dental filling resin, prepared according to any one of claims 1-6, characterized in that, include: The resin has a polymer three-dimensional interlocking network structure formed by cationic ring-opening copolymerization; The three-dimensional interlocking network structure uses cage-like oligomers as cross-linking nodes and open-ring polymer chain segments as the network skeleton to covalently connect the cross-linking nodes. The core of the cage-like oligomer is covalently surrounded by antibacterial side chains, and the cage-like oligomer utilizes a rigid cage-like geometric center to form a spatial steric confinement domain for the antibacterial side chains.

8. The dental filling resin and its preparation method according to claim 7, characterized in that: The cage-like oligomer is a polyhedral oligomeric silsesquioxane; the antibacterial side chain is a quaternary ammonium salt group with a long carbon chain; the polyhedral oligomeric silsesquioxane and the antibacterial side chain are linked by chemical bonds formed by nucleophilic ring-opening addition reaction, forming a composite core with antibacterial source and force conduction function.

9. A dental filling resin according to claim 8, characterized in that: The ring-opening polymer segment is a polyether or polyester segment formed by cationic ring-opening of a low-shrinkage cyclic resin monomer; the cyclic resin monomer is selected from at least one of spirocyclic ortho-carbonate, lactone resin monomer or alicyclic epoxy resin monomer; the polyether or polyester segment can encapsulate the multifunctional cage-like oligomer and antibacterial side chain to form a polymer waterproof layer that blocks water penetration and prevents the sudden release of active substances.

10. A dental filling resin according to claim 7, characterized in that: In the polymer three-dimensional interlocking network structure, each cage-like oligomer serves as a multi-branch crosslinking center, and its surface is radially connected to the open-ring polymer chain segment via covalent bonds. The polar crosslinking sites of the multifunctional cage-like oligomers and the non-polar antibacterial branches form an amphiphilic topology at the microscopic level, so that the crosslinking nodes are in a non-agglomerated dispersed state in the network skeleton and there is no phase separation interface.

Images