High-toughness 3D printing oral denture base resin material and application thereof

Abstract

The invention discloses a high-toughness 3D printing oral denture base resin material and application thereof. The resin composition provided by the invention consists of an acrylic resin group and an epoxy resin group, the acrylic resin group comprises the following components: an acrylate oligomer, a polyfunctional acrylate monomer and a free radical type photoinitiator; the epoxy resin group is of a heat curing type or a light curing type. The resin formula provided by the invention can effectively improve the toughness and polymerization shrinkage performance of a denture base material, and provides a brand new solution for developing an oral denture base repair resin material for 3D printing.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing polymer materials technology, specifically relating to a high-strength and tough 3D printed dental prosthesis base resin material and its application. Background Technology

[0002] As the demand for dental restorations evolves towards personalization and precision, traditional denture base fabrication methods, due to their cumbersome clinical procedures, high technical sensitivity, and lengthy treatment cycles, are no longer sufficient to meet modern medical needs. This is especially true for patients requiring repeat restorations, where the secondary trauma and financial burden of traditional methods are even more pronounced. 3D printing technology, with its advantages of digital modeling and chairside manufacturing, offers a revolutionary approach to the precise molding of denture restorations. Among these technologies, DLP printing, with its high molding precision and strong controllability of surface morphology, has become a research hotspot in personalized denture base manufacturing.

[0003] However, current photopolymerization materials systems face significant technical barriers: most existing acrylic 3D-printed denture base resins rely on free radical polymerization mechanisms induced by a single wavelength light source. Their rapid cross-linking characteristics restrict molecular chain movement, resulting in a highly heterogeneous cross-linked network. This structural defect manifests macroscopically as brittleness and poor toughness in 3D-printed specimens. Microscopically, due to oxygen inhibition and the transformation of intermolecular forces from van der Waals forces to covalent bonds during photopolymerization, the resulting volume shrinkage can reach 7-12%, leading to residual stress accumulation within the base and causing warping and even microcrack propagation. To address these issues, existing technologies often employ methods such as adding inorganic fillers or modifying resin monomers. However, uneven filler dispersion leading to decreased printing accuracy and the risk of monomer toxicity residues limit clinical application.

[0004] The hybrid dual-curing system composed of acrylic / epoxy resin exhibits unique advantages: this system achieves a synergistic effect through sequential photo-thermal or photo-photocuring. Photo-thermal dual-curing uses UV-initiated prepolymerization to form an intermediate material, which is then heat-treated to form a block copolymer structure. Photo-photocuring, on the other hand, uses a dual mechanism of free radicals and cationic polymerization to separately stimulate the polymerization of acrylate and epoxy resin. Both modes can increase crosslinking density while forming a more uniform material network structure. The fully cured resin system increases the crosslinking density of the resin, resulting in a more uniform or isotropic material, which helps improve the mechanical properties of the product.

[0005] The primary functional requirements for 3D-printed dental prosthesis bases are sufficient strength and toughness, and minimal deformation during curing to ensure a precise fit between the prosthesis and oral tissues. According to industry standards, the resin material for the base must meet the following requirements: flexural strength of not less than 65 MPa, and maximum stress intensity factor in fracture toughness of not less than 1.9 MPa. 1 / 2Total fracture energy greater than 900 J / m 2 The polymerization shrinkage should be minimized. Although dual-curing systems show potential in controlling the mechanical properties and polymerization shrinkage of materials, the results are not ideal. For example, CN108948280A discloses a photo-thermal dual-curing 3D printing resin composition, which, by weight, includes the following components: 66-86 parts of free radical photosensitive resin, 9-29 parts of thermocurable epoxy resin, 1-4 parts of free radical photoinitiator, and 1-3 parts of latent thermosetting agent. However, the material obtained by this formulation suffers from poor 3D printing formability, dense cross-linking, brittle texture, uneven distribution of epoxy resin and acrylic resin in the cross-linking network leading to poor overall mechanical properties (flexural strength, modulus, and fracture toughness are all significantly lower than the mechanical properties of denture base resin specified by ISO), brittle fracture, and excessively dark product color. Therefore, there is an urgent need to develop a high-quality, high-strength, and high-toughness dental denture base resin material that balances excellent toughness and strength. Summary of the Invention

[0006] The purpose of this invention is to provide a high-strength and tough 3D-printed dental prosthesis base resin material and its applications. This material combines the advantages of high toughness, low shrinkage, excellent mechanical strength, and a light yellow color, providing a novel solution for developing dental prosthesis base restoration materials for 3D printing.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a dual-curing resin composition comprising an acrylic resin group and an epoxy resin group; The acrylic resin group comprises the following components: acrylate oligomers, multifunctional acrylate monomers, and free radical photoinitiators; The epoxy resin group is either thermosetting or photocurable; The acrylic resin group accounts for 60%-90% of the total mass of the dual-curing resin composition.

[0008] In the acrylic resin group, the acrylate oligomers are selected from polyurethane acrylates and / or urethane methacrylates.

[0009] The multifunctional acrylate monomers are selected from at least one of the following: monofunctional monomers (such as isobornyl acrylate IBOA, acrylmorpholine ACMO, hydroxyethyl acrylate HEA, tetrahydrofuran acrylate THFA, etc.), difunctional monomers (such as triethylene glycol dimethacrylate TEGDMA, tripropylene glycol diacrylate TPGDA, dipropylene glycol diacrylate DPGDA, 1,6-hexanediol diacrylate HDDA, etc.), and trifunctional monomers (such as pentaerythritol triacrylate PETA, trimethylolpropane triacrylate TMPTA, glyceryl propoxylate triacrylate G3POTA, ethoxytrimethylolpropane triacrylate TMP3EOTA, etc.). The monofunctional monomers account for 18-25% of the total monomer content.

[0010] In the acrylic resin group, the mass of the acrylate oligomer accounts for 60-80% of the total mass of the acrylate oligomer and the multifunctional acrylate monomer.

[0011] The amount of the free radical photoinitiator is 0.2%-4% of the total mass of the acrylic resin group.

[0012] The epoxy resin group is thermosetting and includes the following components: epoxy resin, thermosetting agent and accelerator.

[0013] In the thermosetting type, the epoxy resin is selected from one or more of bisphenol A type epoxy resin, aliphatic epoxy resin and epoxy acrylate; for example, DGEBA, E51, E828, EP6110, C-EP, EA, ECC, etc.

[0014] The thermosetting agent is selected from imidazole and / or acid anhydride derivatives; for example, 2-ethyl-4-methylimidazolium (EMI-24), methylhexahydrophthalic anhydride (MHHPA), methyltetrahydrophthalic anhydride (MeTHPA), and maleic anhydride (MA).

[0015] The promoter is an imidazole and / or a tertiary amine, such as DMP-30 or DMP-10.

[0016] The mass ratio of the epoxy resin to the thermosetting agent is 100:(80-90).

[0017] The amount of the accelerator added is 0.2-1 wt% of the total mass of the epoxy resin group.

[0018] The epoxy resin group is photocurable and comprises the following components: epoxy resin and photoinitiator. The mass ratio of the epoxy resin to the photoinitiator is 100:(3-15).

[0019] In the photocuring agent, the photoinitiator is a cationic photoinitiator and / or a free radical photoinitiator; The cationic photoinitiator is a cationic photoinitiator that absorbs in the wavelength range of 300-405 nm. Examples include Omnicat 550, UVI-6992, and 6976.

[0020] The free radical photoinitiator is a free radical photoinitiator that absorbs in the wavelength range of 350-500 nm. Examples include TPO, 1173, 184, and 819.

[0021] In a second aspect, the present invention provides a 3D-printed dental prosthesis base made from the above-mentioned dual-curing resin composition.

[0022] The 3D-printed denture base is either a photothermal 3D-printed denture base or a photo-photothermal 3D-printed denture base.

[0023] This invention breaks through the limitations of traditional single curing paths and innovatively constructs a two-stage curing reaction system of light-heat or light-light: the first stage of ultraviolet light-initiated acrylate molding and the second stage of heat or light-activated epoxy resin polymerization work synergistically to form a two-component crosslinking network of acrylic acid and epoxy resin.

[0024] The dental prosthesis base formed by photothermal 3D printing is obtained by photocuring and then thermal curing using a DLP or SLA printer system; the photocuring conditions are: light wavelength of 350-500 nm and light intensity of 4-10 mW / cm². 2 The single-layer exposure time is 2-6 seconds; the heat curing conditions are: temperature 80-110℃, and heat preservation time 2-4 hours.

[0025] The thermosetting process can be constant temperature curing, two-stage curing, or three-stage curing. In one specific embodiment of the present invention, the thermosetting process is divided into two stages: the first stage is the pre-curing stage, which is held at 80 ℃ for 120 min; the second stage is the curing stage, which is held at 100-120 ℃ for 120 min.

[0026] The dental prosthesis base formed by light-to-light 3D printing is produced by sequentially exposing the prosthesis to light sources of different wavelengths using a dual-wavelength printer; the conditions for light curing are: light intensity of 8-10 mW / cm². 2 The wavelength of the light is 300-500nm.

[0027] In one specific embodiment of the present invention, the exposure time is: 3 seconds of irradiation with a 405 nm light source and 4 seconds of irradiation with a 365 nm light source.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention uses UDMA and high molecular weight acrylate oligomers as the main components, combined with mono / di / trifunctional monomers in an acrylic system, and introduces epoxy resin and anhydride curing agent to form a controllable rate epoxy system. Among them, the mono / di / trifunctional monomers are "gradiently designed", with a higher proportion of monofunctional monomers, which reduces the overall crosslinking density and avoids the formation of a dense and brittle network. The di / trifunctional monomers are present in small amounts to support the modulus and strength of the system, preventing it from being too soft, thus forming a "flexible yet rigid" network: it has sufficient rigidity to support strength, and it also has plasticity to release stress.

[0029] For thermosetting epoxy resin systems, the main chain contains aromatic rings and methylene bridges. The aromatic rings provide stiffness, while the methylene bridges provide flexibility, resulting in higher toughness for the epoxy resin system. Furthermore, the appropriate ratio of anhydride curing agents and tertiary amine accelerators allows for controllable reaction rates during the thermosetting stage. For photocurable epoxy resin systems, curing relies on the protic acid (H⁺) generated by a cationic photoinitiator under light irradiation. This protic acid initiates the cationic ring-opening polymerization of epoxy monomers (such as EP6110 and DGEBA), continuously catalyzing the chain growth process to form a continuous cross-linked network. Epoxy cationic polymerization features the ability to continue the "dark reaction," lack of oxygen inhibition, and significant volume expansion effects. The curing process is gentler, with lower shrinkage, allowing the epoxy network to grow slowly and uniformly within the already formed acrylic backbone. This avoids phase separation and stress concentration caused by the simultaneous rapid cross-linking of the two networks, enabling epoxy segments to more fully interpenetrate and entangle within the acrylic network, forming a stable interpenetrating polymer network. This achieves a synergistic effect of significantly improving mechanical properties while reducing shrinkage. Therefore, the technical effects achieved by this invention are based on the design of the formulation components and the research on the curing mechanism, and are obtained through experiments, rather than simply by component substitution or conventional parameter optimization.

[0030] Specifically, this is reflected in the following ways: 1. High Toughness: The dual-curing resin formulation developed in this invention is suitable for photo-thermal or photo-photo-light dual-curing processes. The fracture toughness of the prepared standard mechanical test specimens is significantly improved, meeting industry standard requirements. Because the acrylic resin and epoxy resin form a cross-linked polymer network, the mechanical properties of the resin are improved to a certain extent. Analysis of the fracture surface morphology shows that, compared to the smooth and brittle fracture surface of the single acrylate component, the fracture surface of the dual-curing resin specimen exhibits large-area wrinkles, indicating that this formulation provides stronger resistance to specimen fracture.

[0031] 2. Oligopolymerization and Shrinkage: The resin material provided by this invention exhibits a low polymerization shrinkage rate. The two-component resin formulation, composed of acrylic resin and epoxy resin, undergoes free radical polymerization under photocuring, where the double bonds of the acrylic resin monomers and oligomers open. The connection between monomers and oligomers changes from van der Waals forces to covalent chain connections, leading to a reduction in the distance between molecules and thus contributing to shrinkage. As the content of epoxy monomers increases, the shrinkage rate of the two-component resin gradually decreases. This is because the photoinitiator or thermosetting agent triggers the ring-opening reaction of the epoxy bonds in the epoxy resin, increasing the distance between reactants and effectively reducing shrinkage. This, to a certain extent, ensures the accuracy of the 3D printed product and helps solve the deformation problem of printed parts existing in traditional materials.

[0032] 3. Simple preparation and broad application prospects: The two-component resin formulation developed in this invention can achieve cross-linking of acrylic resin under a specific light source, and can achieve polymerization of epoxy resin through sequential thermal or photocuring. The high-strength and tough dual-curing resin material and dual-curing method of this invention are suitable for preparing 3D printed dental prosthesis bases, and can also be extended to the research and development and application of other high-precision and personalized biomedical restorative materials. Attached Figure Description

[0033] Figure 1 The image shows the dual-curing performance characterization of the high-strength and tough 3D-printed dental prosthesis base resin provided by this invention.

[0034] Figure 2 The fracture surface morphology of dual-cured resin specimens obtained with different acrylate-epoxy resin mass ratios is shown.

[0035] Figure 3 The fracture surface morphology of the resin material obtained in the comparative example is shown.

[0036] Figure 4 The results show the biocompatibility of dual-cured resin specimens obtained with different acrylate-epoxy resin mass ratios.

[0037] Figure 5 The images show the appearance of the dual-cured resin specimens obtained in Example 1 and Comparative Example 5; in the figures, the left image is Comparative Example 5 and the right image is Example 1. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0040] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.

[0041] The raw materials used in the following examples: UDMA: Full Chinese name is polyurethane dimethacrylate, purchased from ESSTECH.

[0042] 930 oligomer: also known as Exothane 10, is a new type of polyurethane, purchased from ESSTECH.

[0043] Example 1: Preparation of a dual-curing resin composition and a 3D-printed dental prosthesis base This embodiment provides a dual-curing resin composition, which, by mass fraction, consists of the following components: 90 wt% acrylic resin component (photocurable portion) and 10 wt% epoxy resin component (thermocurable portion).

[0044] (1) The acrylic resin component used for the photocuring part consists of the following components: Acrylic ester oligomer 70wt%: UDMA 45wt%, 930 oligomer 25wt%; Multifunctional acrylate monomers 30wt%: HPA 20wt%, difunctional monomer TEGDMA 5wt%, trifunctional monomer TMP(EO)3TA 5wt%; The free radical photoinitiator TPO is added at a rate of 2% of the total mass of the acrylic resin components. (2) The epoxy resin component used for the thermosetting part consists of the following components: Bisphenol A type epoxy resin: E51 50wt%, E828 50wt%; Anhydride thermosetting agents: MHHPA; The mass ratio of bisphenol A epoxy resin to an anhydride thermosetting agent is 100:85. Accelerator: DMP-30, added at a rate of 0.5 wt% of the total mass of the epoxy resin components.

[0045] This embodiment also provides the preparation of 3D-printed dental prosthesis bases using the above-mentioned dual-curing resin composition, with the specific steps as follows: (1) Mix the acrylate oligomer, multifunctional acrylate monomer and free radical photoinitiator, heat to 37°C under light-protected conditions and stir until homogeneous, then vacuum mix in a vacuum homogenizer for 10 min to obtain the photocurable acrylic resin component. (2) Mix bisphenol A type epoxy resin, acid anhydride thermosetting agent and accelerator, and perform vacuum degassing treatment to obtain thermosetting epoxy resin components.

[0046] (3) 3D printing: The photocurable acrylic resin component and the thermocurable epoxy resin component were mixed at a mass ratio of 9:1. The resin mixture was then degassed under vacuum and printed using a DLP printer to obtain the printed part. The printing parameters were: light wavelength 385nm, light intensity 4.5 mW / cm². 2 The single-layer exposure time is 3 seconds, and the layer thickness is 50 μm / layer.

[0047] (4) Heat curing treatment: Place the printed part in a programmable temperature-controlled oven and use a staged heating method: first heat up to 80℃ and keep it at that temperature for 120 minutes; then heat up to 100℃ and keep it at that temperature for 120 minutes to complete the heat curing and obtain the denture base.

[0048] Example 2: Preparation of dual-curing resin composition and 3D printed dental prosthesis base This embodiment provides a dual-curing resin composition, which, by mass fraction, consists of the following components: 80 wt% acrylic resin component (photocurable portion) and 20 wt% epoxy resin component (photocurable portion).

[0049] (1) The acrylic resin component used for the photocuring part consists of the following components: 70wt% acrylate oligomer: 60wt% UDMA, 10wt% 930 oligomer; Multifunctional acrylate monomers 30wt%: IBOA 10wt%, ACMO 10wt%, bifunctional monomer TPGDA 5wt%, trifunctional monomer TMP(EO)9TA 5wt%; Photoinitiator 819 is added at a rate of 2% of the total mass of the acrylic resin components. (2) The epoxy resin component used for the photocuring part consists of the following components: Alicyclic epoxy resin: EP6110; Cationic photoinitiator: Triarylthionium salt (I-160); The mass ratio of alicyclic epoxy resin to cationic photoinitiator is 100:5.

[0050] This embodiment also provides the preparation of 3D-printed dental prosthesis bases using the above-mentioned dual-curing resin composition, with the specific steps as follows: (1) Mix the acrylate oligomer, multifunctional acrylate monomer and free radical photoinitiator, heat to 37°C under light-protected conditions and stir until homogeneous, then vacuum mix in a vacuum homogenizer for 10 min to obtain the photocurable acrylic resin component.

[0051] (2) Mix epoxy resin with cationic photoinitiator and vacuum degassing to obtain photocurable epoxy resin components.

[0052] (3) 3D Printing: The photocurable acrylic resin component and the photocurable epoxy resin component were mixed at a mass ratio of 8:2. The two-component mixture was then degassed under vacuum and set aside. A dual-beam printer was used for printing. The photo-curing conditions were: light intensity of 8-10 mW / cm². 2 Irradiate for 3 seconds under the built-in light source of 405 nm wavelength in the dual-wavelength printer, and for 4 seconds under the light source of 365 nm wavelength.

[0053] (4) Post-curing treatment: Place the printed parts in a post-curing chamber and perform post-curing under nitrogen protection.

[0054] Example 3: Preparation of Dual-Curing Resin Composition and 3D Printed Dental Prosthesis Base This embodiment provides a dual-curing resin composition, which, by mass fraction, consists of the following components: 70 wt% acrylic resin component (photocurable portion) and 30 wt% epoxy resin component (photocurable portion).

[0055] (1) The acrylic resin component used for the photocuring part consists of the following components: 70wt% acrylate oligomer: 50wt% UDMA, 20wt% 930 oligomer; Multifunctional acrylate monomers 30wt%: HPA 10wt%, ACMO 10wt%, bifunctional monomer TPGDA 2.5wt%, TEGDMA 2.5wt%, trifunctional monomer PETA 5wt%.

[0056] Photoinitiator 819 is added at a rate of 2% of the total mass of the acrylic resin components. (2) The epoxy resin component used for the photocuring part consists of the following components: Bisphenol A type epoxy resin: DGEBA; Cationic photoinitiator: UVI-6976; Free radical photoinitiator: Photoinitiator 184; The mass ratio of bisphenol A epoxy resin to cationic photoinitiator and free radical photoinitiator is 100:4:4.

[0057] This embodiment also provides the preparation of 3D-printed dental prosthesis bases using the above-mentioned dual-curing resin composition, with the specific steps as follows: (1) Mix the acrylate oligomer, multifunctional acrylate monomer and free radical photoinitiator, heat to 37°C under light-protected conditions and stir until homogeneous, then vacuum mix in a vacuum homogenizer for 10 min to obtain the photocurable acrylic resin component.

[0058] (2) Mix bisphenol A type epoxy resin and two photoinitiators, and perform vacuum degassing treatment to obtain a photocurable epoxy resin component.

[0059] (3) 3D printing: The photocurable acrylic resin component and the epoxy resin component were mixed at a mass ratio of 7:3, and then the two-component mixture was vacuum degassed before use. The mixture was printed using a dual-beam DLP printer. The photo-curing conditions were: light intensity of 8-10 mW / cm². 2 Irradiate for 3 seconds under the built-in light source of 405 nm wavelength in the dual-wavelength printer, and for 4 seconds under the light source of 365 nm wavelength.

[0060] (4) Post-curing treatment: Place the printed parts in a post-curing chamber and perform post-curing under nitrogen protection.

[0061] Example 4: Preparation of dual-curing resin composition and 3D printed dental prosthesis base This embodiment provides a dual-curing resin composition, which, by mass fraction, consists of the following components: 60 wt% acrylic resin component (photocurable portion) and 40 wt% epoxy resin component (thermocurable portion).

[0062] (1) The acrylic resin component used for the photocuring part consists of the following components: 70 wt% acrylate oligomer: 65 wt% UDMA, 5 wt% 930 oligomer; Multifunctional acrylate monomers 30wt%: IBOA 5wt%, ACMO 15wt%, bifunctional monomer TPGDA 2.5wt%, TEGDMA 2.5wt%, trifunctional monomer PETA 5wt%.

[0063] The photoinitiator TPO is added at a rate of 2% of the total mass of the acrylic resin components. (2) The epoxy resin component used for the thermosetting part consists of the following components: Bisphenol A type epoxy resin: E51; Thermosetting agent: MeTHPA; The mass ratio of bisphenol A epoxy resin to thermosetting agent is 100:84.7; Accelerator: DMP-30, added at a rate of 0.5 wt% of the total mass of the epoxy resin components.

[0064] This embodiment also provides the preparation of 3D-printed dental prosthesis bases using the above-mentioned dual-curing resin composition, with the specific steps as follows: (1) Mix the acrylate oligomer, multifunctional acrylate monomer and free radical photoinitiator, heat to 37°C under light-protected conditions and stir until homogeneous, then vacuum mix in a vacuum homogenizer for 10 minutes to obtain the photocurable acrylic resin component.

[0065] (2) Mix bisphenol A type epoxy resin, thermosetting agent and accelerator, and perform vacuum degassing treatment to obtain thermosetting epoxy resin components.

[0066] (3) 3D Printing: The photocurable acrylic resin component and the thermocurable epoxy resin component were mixed at a mass ratio of 6:4. The two-component mixture was then vacuum degassed before use. The mixture was printed using a DLP printer (Asiga, Max UV385). The printing conditions were: light wavelength of 385nm and light intensity of 4.6mW / cm². 2 The single-layer exposure time is 3 seconds; the layer thickness is 50 μm / layer.

[0067] (4) Heat curing treatment: Place the printed parts in a programmable temperature control oven and use a staged heating method: first heat up to 80℃ and keep it at that temperature for 120 minutes; then heat up to 100℃ and keep it at that temperature for 120 minutes to complete the heat curing.

[0068] Comparative Example 1: Preparation of a UV-curable acrylic resin The preparation steps are as follows: The resin used for the photocurable component consists of oligomers (UDMA 70 wt%) and acrylate monomers of different functionalities (monofunctional IBOA 25 wt%, difunctional DPGDA 5 wt%). Photoinitiator TPO was added to 2% of the total mass of the acrylic resin. The mixture was heated to 37°C and stirred until homogeneous under light-protected conditions, then vacuum-mixed for 10 min in a vacuum homogenizer to obtain the photocurable acrylic resin component. The mixture was printed using a DLP printer with a layer thickness of 50 μm, a wavelength of 385 nm, and a light intensity of 4.6 mW / cm². 2 The single-layer exposure time is 3 seconds.

[0069] Comparative Example 2: Preparation of a UV-curable acrylic resin The preparation steps are as follows: The resin used for photocuring consists of a series of acrylic resin monomers, including oligomers (UDMA, 60 wt%, 930 oligomer, 10 wt%) and acrylate monomers of different functionalities (monofunctional HPA 25 wt%, difunctional TPGDA 5 wt%). Photoinitiator 819 was added to 2% of the total mass of the acrylic resin. The mixture was heated to 37 °C and stirred until homogenized under light-protected conditions, followed by vacuum mixing for 10 min in a vacuum homogenizer to obtain the photocurable acrylic resin component. It was then printed using a dual-beam DLP printer. Curing was performed using only the printer's 405 nm light source at an intensity of 8 mW / cm². 2 The single-layer exposure time is 3 seconds.

[0070] Comparative Example 3: Preparation of a UV-curable acrylic resin The preparation steps are as follows: The resin used for photocuring consists of a series of acrylic resin-based monomers, including oligomers (UDMA, 55 wt%; 930 oligomer, 15 wt%) and acrylate monomers of different functionalities (monofunctional ACMO + IBOA 20 wt%; difunctional TPGDA 4 wt%; trifunctional TMP(EO)3TA 6 wt%). Photoinitiator TPO was added to 2% of the total mass of the acrylic resin. The mixture was heated to 37°C and stirred until homogeneous under light-protected conditions. It was then vacuum-mixed for 10 min in a vacuum homogenizer to obtain the photocurable acrylic resin component. The resin was printed using a DLP printer with a layer thickness of 50 μm, a wavelength of 385 nm, and a light intensity of 4.6 mW / cm². 2 The single-layer exposure time is 3 seconds.

[0071] Comparative Example 4: A photocurable commercially available 3D-printed denture base resin A commercially available 3D printing denture base resin (Asiga Dentbase photocurable denture base resin imported from Germany) was selected for printing. The resin solution was vacuum degassed before use. A DLP printer was used for printing, with a layer thickness of 50 μm, a wavelength of 385 nm, and a light intensity of 4.6 mW / cm². 2 The single-layer exposure time is 3 seconds.

[0072] Post-curing treatment: The printed parts are placed in a post-curing chamber (Otoflash G171, Germany) and photocured under nitrogen protection.

[0073] Comparative Example 5 Example 1 in CN108948280A: A photo-thermal dual-curing 3D printing resin composition comprises: an acrylic resin group and an epoxy resin group, with a mass ratio of 90:10; The acrylate group consists of the following: 43 parts by mass of polyurethane acrylate (U-6282) and 43 parts by mass of pentaerythritol tetraacrylate, and 4 parts by mass of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. The epoxy resin group consists of the following: 9 parts by weight of aliphatic epoxy resin 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, and 1 part by weight of imidazole latent thermosetting agent Kingcure 390.

[0074] The steps for preparing the denture base using the resin composition are the same as in Example 1.

[0075] Effect verification: 1. Curing, polymerization shrinkage, and mechanical property testing of dual-curing resin materials: Characterization of curing performance of dual-curing resin specimens: Taking epoxy resin E51 as an example, the thermosetting temperature was studied by Fourier transform infrared spectroscopy, and the double bond transformation of the samples after printing and after curing was characterized. According to ISO 17304-2013 standard, the volume shrinkage rate and mechanical properties of the obtained samples were tested.

[0076] Mechanical property standards for dual-curing resin specimens: According to ISO 4049, the mechanical properties of the samples are tested, including flexural strength and modulus, fracture toughness, and the surface micromorphology of the specimens after fracture is observed using scanning electron microscopy (SEM).

[0077] The results are as follows: After heat curing at 80℃ for 2 hours and then at 100℃ for 2 hours, the epoxy resin was basically completely cured, and the characteristic absorption peaks of the epoxy resin disappeared. Figure 1 The left-middle figure shows that the unreacted anhydride molecule contains two carbonyl peaks (C=O, 1732 cm⁻). 1 and 1700 cm⁻ 1 As the temperature increases (80℃→120℃), the acid anhydride gradually participates in the reaction, opening the ring to form an ester bond. The carbonyl group in the formed ester bond is at 1730 cm⁻ 1 A single peak was observed at 915 cm⁻¹. After heating at 80℃ for 2 h followed by 100℃ for 1 h, the system transformed from a multi-component mixture into a homogeneous cross-linked network structure. The epoxy groups showed a peak at 915 cm⁻¹. 1 There is a strong characteristic absorption peak on the left and right sides. As curing proceeds, the epoxy group opens the ring, and the absorption peak gradually weakens to a flat state at 80℃ for 2 hours and then at 100℃ for 2 hours.

[0078] Figure 1 The right-middle figure shows the infrared absorption peaks of the photo-thermal curing resin at each curing stage. The unreacted dual-cured resin contains two split carbon-carbon double bond peaks (C=C, 1646 cm⁻). 1 and 1610 cm⁻1 As curing proceeds in a light-to-heat sequence, carbon-carbon double bonds participate in the reaction at 1640 cm⁻. 1 A single peak is observed at 810 cm⁻¹, and the peak intensity gradually decreases; at 810 cm⁻¹... 1 The C=C peak also gradually decreases. This phenomenon is an important indicator of the curing of acrylic resin. After heating, the epoxy groups in the system reach 915 cm⁻¹. 1 The absorption peak gradually weakens and flattens out, indicating that the two-component resin has successfully reacted and cured after photothermal treatment.

[0079] Table 1. Polymerization shrinkage and mechanical properties of Examples 1-4 and Comparative Examples 1-5 Regarding polymerization shrinkage, the volume shrinkage rate of dual-curing resin decreases with increasing epoxy resin content, and the volume shrinkage rate is less than 7%, which is lower than that of commercially available resins currently used for 3D printing denture bases, such as Asiga dentbase (8.23 ± 0.29%) and Formlabs gray resin (11.2 ± 0.35%).

[0080] Regarding mechanical properties, the fracture toughness of dual-curing resins varies with different epoxy resin contents. When the epoxy resin content is between 10-40 wt%, the fracture toughness meets industry standards, as shown in Table 1. The fracture toughness of the dual-curing resin increases with increasing epoxy resin content. The microstructure of the fracture surface is shown in... Figure 2 As shown in the figure, the fracture surface of the dual-cured resin specimen in the embodiment has a rough morphology and deep wrinkles, indicating that its fracture mode has changed to ductile fracture.

[0081] The SEM results of the fracture surfaces of Comparative Examples 1-4 show that the single-photocured acrylate 3D printed specimens exhibit brittle fracture with smooth fracture surfaces. Only the fracture surface of Comparative Example 3 is relatively rough, with deepened grooves. This is reflected in the fracture toughness values; specifically, Comparative Example 3 has the highest maximum strength factor and total fracture work among the four groups. Therefore, the trifunctional monomer TMP(EO)9TA plays a role in improving the fracture toughness of the photocured acrylate 3D printed specimens of the comparative examples.

[0082] Meanwhile, comparing Comparative Example 5 and Example 1, it can be seen that under the same acrylic / epoxy resin mass ratio (90:10), the polypentaerythritol tetraacrylate and alicyclic epoxy resin / imidazolium latent curing system used in Comparative Example 5, due to the high functionality of the acrylate, has an extremely high carbon-carbon double bond density. Combined with the excessively high photoinitiator content, this results in overly dense crosslinking points and an excessively fast crosslinking speed during photoinitiated polymerization, leading to a dense and brittle crosslinking network. For the epoxy resin, the addition of an imidazolium thermosetting agent to the alicyclic epoxy resin, due to the active catalyst, causes rapid local crosslinking during the thermosetting stage, easily forming epoxy resin aggregation points. This makes it difficult for the epoxy resin to be evenly distributed in the crosslinking network, resulting in brittle fracture of the material as a whole. Its flexural strength is only 1413±1.61 MPa, its elastic modulus is approximately 1024±76.49 MPa, and among the fracture toughness indicators, the maximum strength factor Kmax is 0.67±0.15 MPa·m. 1 / 2 The total fracture work Wt is 82.35±31.41 J / m. 2 The volume shrinkage rate was approximately 8.69 ± 0.41%, and all indicators were far inferior to those of Examples 1-4. Furthermore, the material obtained after complete curing of the formulation in Comparative Example 5 was brownish-yellow, which was too dark, while the cured material obtained from the formulation in Example 1 was light yellow, indicating higher quality.

[0083] In summary, the specimens designed according to industry standards using the dual-curing resin provided by this invention exhibit a flexural strength ≥ 65 MPa and a fracture toughness index with a maximum strength factor ≥ 1.9 MPa. 1 / 2 Total work done during fracture ≥900J / m 2 The polymerization shrinkage rate is between 5.4% and 6.5%. Furthermore, the resin formulation is non-cytotoxic. Figure 4 It conforms to the requirements of ISO 10993-5:2009.

[0084] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A dual-curing resin composition comprising an acrylic resin group and an epoxy resin group; The acrylic resin group comprises the following components: acrylate oligomers, multifunctional acrylate monomers, and free radical photoinitiators; The acrylate oligomers are UDMA and 930 oligomer; The multifunctional acrylate monomers are composed of monofunctional monomers, difunctional monomers, and trifunctional monomers; wherein... Monofunctional monomers account for 18-25%; The mass of the acrylate oligomer accounts for 60-80% of the total mass of the acrylate oligomer and the multifunctional acrylate monomer; The epoxy resin group is either thermosetting or photocurable; The acrylic resin group accounts for 60%-90% of the total mass of the dual-curing resin composition.

2. The dual-curing resin composition according to claim 1, characterized in that, The amount of the free radical photoinitiator is 0.2%-4% of the total mass of the acrylic resin group.

3. The dual-curing resin composition according to claim 1, characterized in that, The epoxy resin group is thermosetting and includes the following components: epoxy resin, thermosetting agent and accelerator; The epoxy resin is selected from one or more of bisphenol A type epoxy resin, aliphatic epoxy resin and epoxy acrylate; The thermosetting agent is selected from imidazoles and / or acid anhydrides; The promoter is an imidazole and / or a tertiary amine.

4. The dual-curing resin composition according to claim 3, characterized in that, The mass ratio of the epoxy resin to the thermosetting agent is 100:(80-90). The amount of the accelerator added is 0.2-1 wt% of the total mass of the epoxy resin group.

5. The dual-curing resin composition according to claim 1, characterized in that, The epoxy resin group is photocurable and includes the following components: epoxy resin and photoinitiator; The photoinitiator is a cationic photoinitiator and / or a free radical photoinitiator.

6. The dual-curing resin composition according to claim 5, characterized in that, The cationic photoinitiator is a cationic photoinitiator that absorbs in the wavelength range of 300-405 nm. The free radical photoinitiator is a free radical photoinitiator that absorbs in the wavelength range of 350-500 nm.

7. A 3D-printed dental prosthesis base, made from the dual-curing resin composition according to any one of claims 1-6.

8. The 3D-printed denture base according to claim 7, characterized in that, The 3D-printed denture base is either a photothermal 3D-printed denture base or a photo-photothermal 3D-printed denture base.

9. The 3D-printed denture base according to claim 8, characterized in that, The dental prosthesis base formed by photo-thermal 3D printing is obtained by photo-curing and then thermal curing using a DLP or SLA printer system. The conditions for photopolymerization are: light wavelength of 350-500 nm and light intensity of 4-10 mW / cm². 2 The single-layer exposure time is 2-6 seconds; The thermosetting conditions are: temperature 80-110℃, holding time 2-4 h.

10. The 3D-printed denture base according to claim 8, characterized in that, The dental prosthesis base formed by light-to-light 3D printing is produced by sequentially irradiating different wavelength light sources built into the printer using a dual-wavelength printer. The conditions for photopolymerization are: light intensity of 8-10 mW / cm². 2 The wavelength of the light is 300-500 nm.

Images