3d printing interlayer reinforcement molding method and implant for cranioplasty

Abstract

The application provides a 3D printing interlayer reinforcing forming method for cranium defect repair, and belongs to the technical field of 3D printing and medical implant manufacturing. The steps are as follows: 1. Based on the medical imaging data of the cranium defect area of a patient, a personalized three-dimensional model that is adapted to the anatomical structure of the bone defect area is constructed, and path data for 3D printing is generated; 2. The selected medical-grade polymer material is heated in a differentiated temperature control manner by setting different temperature control areas through a 3D printing device; 3. The 3D printing device synchronously extrudes and deposits materials in different states along the preset path direction through a double-nozzle structure, and finally forms an entity that is matched with the structure of the bone defect area; 4. The surface of the printed part is cleaned and dried at low temperature, and sterilization and sterile packaging are performed according to the medical use requirements. The application can significantly improve the tightness of interlayer bonding without affecting the printing efficiency.

Description

Technical Field

[0001] This application relates to the field of 3D printing and medical implant manufacturing technology, and in particular to a 3D printing interlayer reinforcement molding method and implant for the repair of skull defects. Background Technology

[0002] With the development of personalized medicine technology, 3D printing technology is increasingly widely used in the customized manufacturing of medical implants, especially in the field of skull defect repair. Customized repair solutions based on the combination of medical image modeling and 3D printing have become one of the main development directions for improving postoperative fit and structural stability. Currently, medical-grade thermoplastic polymers are widely used in the manufacture of printed implants for bone defect repair due to their good biocompatibility, biodegradability, and molding adaptability.

[0003] In the traditional process of fabricating personalized 3D printed skull implants, polymer material is typically deposited layer by layer using a hot melt extrusion (FDM) device, forming a solid model with a stacked structure. The printing path largely relies on pre-set 3D path data, combined with the rapid cooling and solidification of the molten material, to achieve layer-by-layer construction. Some devices can optimize printing accuracy and surface quality by setting temperature zones and adjusting nozzle movement speed and printing rhythm, but most still operate on an "isothermal" extrusion mode, meaning the material remains under essentially the same heating state during printing to complete the formation of the entire layer structure.

[0004] However, existing single-nozzle isothermal printing methods are prone to insufficient adhesion between different printed layers during the layer-by-layer construction process, especially on complex curved surfaces or areas with large spans. In these cases, the thermoplastic material does not fully fuse with the previous layer after deposition and cooling, leading to decreased interfacial bonding strength. This results in easy peeling, cracking, or localized fracture of the interlayer connections, severely impacting the overall structural integrity and postoperative stability of the final implant. Particularly in clinical settings where the skull structure demands high fit and mechanical uniformity, the quality of interlayer bonding becomes a significant bottleneck limiting the long-term reliability of printed implants.

[0005] In summary, how to effectively enhance the bonding quality between printing layers while ensuring personalized printing accuracy, thereby improving the continuity and interface strength of the overall implant structure, is a key technical problem that current 3D printing manufacturing technology for skull defect repair urgently needs to solve. Summary of the Invention

[0006] This application provides a 3D printing interlayer reinforcement molding method and implant for skull defect repair, in order to solve the problem of insufficient interlayer bonding in current 3D printed skull defect repair implants.

[0007] On the one hand, this application provides a 3D printing interlayer reinforcement molding method for skull defect repair, including the following steps:

[0008] S101: Based on medical imaging data of the patient's skull defect area, construct a personalized 3D model that matches the anatomical structure of the bone defect area and generate path data for 3D printing.

[0009] S102: Select medical-grade polymer materials with thermoplasticity and biocompatibility, and use a 3D printing device to heat the polymer materials in a differentiated temperature control manner by setting different temperature control areas, so that a part of the polymer material reaches a completely melted state and another part of the polymer material reaches a semi-melted state.

[0010] S103: A 3D printing device is used to simultaneously extrude and deposit fully molten and semi-molten polymer materials along a preset path using a dual-nozzle structure. Based on three-dimensional model data, the device controls the process to sequentially complete the molding and construction of each printing layer, forming a solid that matches the structure of the bone defect area. The fully molten material is extruded along the front end of the printing path to form the main structure of the current printing layer, while the semi-molten material is extruded immediately behind the fully molten material and deposited into the interface area between the current printing layer and the previous printing layer to penetrate into the surface pores of the previous printing layer.

[0011] S104: Perform surface cleaning and low-temperature drying on the printed solid parts, and sterilize and aseptically package them according to medical use requirements.

[0012] As an optional approach in this application, in step S101, the personalized three-dimensional model is constructed by segmenting, reconstructing and solid modeling the patient's CT or MRI image data using medical image processing software. During the model construction process, the boundaries between the bone defect area and the surrounding anatomical structure are fitted so that the three-dimensional model can correspond to the actual anatomical structure. The medical image processing software used is Mimics, 3-matic or Freeform.

[0013] As an alternative to this application, the polymer material is selected from one or more mixtures of polycaprolactone, polylactic acid, polylactic acid-glycolic acid copolymer and polyetheretherketone.

[0014] As an optional embodiment of this application, the polymer material may be further compounded with hydroxyapatite or β-tricalcium phosphate.

[0015] As an optional aspect of this application, the temperature control range of the fully molten state is 5°C to 30°C above the melting point of the polymer material, and the temperature control range of the semi-molten state is 10°C below the melting point of the polymer material to between the melting point and the melting point.

[0016] As an optional method of this application, in step S104, the sterilization process is ethylene oxide sterilization or low-temperature plasma sterilization, and the low-temperature drying process is constant temperature vacuum drying, with a drying temperature of 30-50℃ and a drying time of 10-40 min.

[0017] As an optional approach in this application, the cleaning process described in step S104 includes two stages: ultrasonic cleaning and purified water rinsing.

[0018] The first stage is the ultrasonic cleaning stage, in which the printed solid part is placed in a neutral cleaning solution at a temperature of 30℃~45℃, and ultrasonic waves with a frequency of 20kHz~40kHz are used to clean it for 3~10 minutes to remove residual substances and tiny particles from the surface and pores of the printed part.

[0019] The second stage is the purified water rinsing stage, in which deionized purified water is used to repeatedly rinse the ultrasonically cleaned printed parts from multiple angles to ensure that there are no chemical residues or visible contaminants on the surface.

[0020] As an alternative to this application, the 3D printing device is equipped with a dual-nozzle structure consisting of a first nozzle and a second nozzle, and two temperature chambers that can heat the polymer material in a differentiated temperature control manner as different temperature control zones.

[0021] The first and second nozzles are arranged in parallel with their nozzle outlets on the same plane. The first and second nozzles are arranged sequentially in the printing path direction. The first nozzle is located at the front of the printing path and is used to extrude fully molten polymer material to print the main structure of the current printed layer. The second nozzle is located after the first nozzle and is used to extrude and deposit semi-molten polymer material in the interface area between the current printed layer and the previous printed layer. The two temperature chambers consist of a first temperature chamber and a second temperature chamber. The first temperature chamber is connected to the first nozzle and is used to heat a portion of the polymer material to a fully molten state. The second temperature chamber is connected to the second nozzle and is used to heat another portion of the polymer material to a semi-molten state.

[0022] As an optional embodiment of this application, the distance between the nozzle outlet centers of the first nozzle and the second nozzle is 8mm to 15mm.

[0023] On the other hand, this application also provides a 3D-printed implant for skull defect repair, which is manufactured using the 3D printing interlayer reinforcement molding method for skull defect repair described in this application.

[0024] As an optional aspect of this application, the height of each printed layer of the implant is controlled between 0.05 mm and 0.15 mm.

[0025] Compared with the prior art, this application has the following beneficial effects:

[0026] 1. This application provides a 3D printing method for interlayer reinforcement molding and an implant for skull defect repair. The application introduces the concept of "co-deposition of materials in different states" in the raw material processing stage. Specifically, the polymer material is divided into two parts and heated in different temperature-controlled regions. One part of the material is heated to a fully molten state above its melting point, possessing good fluidity and spreadability, and is mainly used for the main structure of the printed component. The other part of the material is heated to a semi-molten state close to its melting point but not fully molten, retaining a certain degree of thermal viscosity and forming ability, suitable for structural transition at the interface. This control method based on the difference in the physical state of the materials helps to improve the problem of insufficient interlayer adhesion, providing good thermodynamic conditions for subsequent material penetration and interface fusion.

[0027] 2. This application employs a 3D printing device with a dual-nozzle structure to simultaneously extrude and deposit polymer materials in both fully molten and semi-molten states, achieving simultaneous deposition of materials in different states. The fully molten material is extruded along the front end of the printing path to form the main structure of the current printed layer. The semi-molten material is extruded immediately behind the fully molten material and deposited into the interface region between the current and previous printed layers, penetrating into the surface pores of the previous printed layer. This "front-end configuration, rear-end penetration" printing method allows for a synergistic effect of functional zoning and transitional fusion in material deposition, significantly improving the tightness of interlayer bonding without affecting printing efficiency, and helping to reduce the probability of interface peeling and delamination.

[0028] 3. This application utilizes medical imaging data to construct a personalized 3D model throughout the entire printing process, achieving a high degree of consistency between the printing path and the actual bone defect boundary. During the layer-by-layer molding process, the extruded material is deposited strictly following the model path. With the precise superposition of each layer of material in terms of geometric and physical properties, the printed part exhibits excellent consistency in both macroscopic structural continuity and microscopic interface fusion. Furthermore, leveraging the physical properties of dual-state materials, this method maintains high molding quality even in areas with complex structures, curved surfaces, or large cross-regional spans, further enhancing the structural stability and biocompatibility of the implant in long-term application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A flowchart illustrating a 3D printing interlayer reinforcement molding method for skull defect repair provided in an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of a dual-nozzle structure arrangement provided in an embodiment of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0033] like Figure 1 As shown in the figure, this application provides a 3D printing interlayer reinforcement molding method for skull defect repair, including the following steps:

[0034] S101: Based on medical imaging data of the patient's skull defect area, construct a personalized 3D model that matches the anatomical structure of the bone defect area and generate path data for 3D printing.

[0035] S102: Select medical-grade polymer materials with thermoplasticity and biocompatibility. Use a 3D printing device to heat the polymer materials in a differentiated temperature control manner by setting different temperature control zones, so that part of the polymer material reaches a completely melted state and another part of the polymer material reaches a semi-melted state.

[0036] S103: A 3D printing device is used to simultaneously extrude and deposit fully molten and semi-molten polymer materials along a preset path using a dual-nozzle structure. Based on three-dimensional model data, the device controls the process to sequentially complete the molding and construction of each printing layer, forming a solid that matches the structure of the bone defect area. The fully molten material is extruded along the front end of the printing path to form the main structure of the current printing layer, while the semi-molten material is extruded immediately behind the fully molten material and deposited into the interface area between the current printing layer and the previous printing layer to penetrate into the surface pores of the previous printing layer.

[0037] S104: Perform surface cleaning and low-temperature drying on the printed solid parts, and sterilize and aseptically package them according to medical use requirements.

[0038] This embodiment introduces the concept of "co-deposition of materials in different states" in the raw material processing stage. Specifically, the polymer material is divided into two parts and heated in different temperature-controlled zones. One part of the material is heated to a fully molten state above its melting point, exhibiting good fluidity and spreadability, and is mainly used for the main structure of the printed component; the other part of the material is heated to a semi-molten state close to its melting point but not yet fully molten, retaining a certain degree of thermal viscosity and formability, suitable for structural transition in the interface region. This control method based on the difference in the physical state of the materials helps to improve the problem of insufficient interlayer adhesion, providing good thermodynamic conditions for subsequent material penetration and interface fusion.

[0039] Furthermore, this embodiment employs a 3D printing device with a dual-nozzle structure to simultaneously extrude and deposit fully molten and semi-molten polymer materials, achieving simultaneous deposition of materials in different states. The fully molten material is extruded along the front end of the printing path to form the main structure of the current printed layer. The semi-molten material is extruded immediately behind the fully molten material and deposited into the interface region between the current and previous printed layers, penetrating into the surface pores of the previous printed layer. This "front-end configuration, rear-end penetration" printing method allows for a synergistic effect of functional zoning and transitional fusion in material deposition, significantly improving the tightness of interlayer bonding without affecting printing efficiency, and helping to reduce the probability of interface peeling and delamination.

[0040] Furthermore, this embodiment utilizes medical imaging data to construct a personalized 3D model throughout the entire printing process, achieving a high degree of consistency between the printing path and the actual bone defect boundary. During the layer-by-layer molding process, the extruded material is deposited strictly following the model path. With the precise superposition of each layer of material in terms of geometric and physical properties, the printed part exhibits excellent consistency in both macroscopic structural continuity and microscopic interface fusion. Moreover, leveraging the physical properties of dual-state materials, this method maintains high molding quality even in areas with complex structures, curved surfaces, or large cross-regional spans, further enhancing the structural stability and biocompatibility of the implant in long-term application.

[0041] Furthermore, in step S101, this embodiment constructs a personalized 3D model that conforms to the actual anatomical structure based on medical imaging data (such as CT or MRI) of the patient's skull defect area, enabling a high degree of matching between the printing path data and the target defect boundary. This model not only reflects the spatial morphology of the defect area but also relatively completely reproduces the curvature changes and anatomical structural features of the skull. Using this model as a printing basis, the direction and layers of material deposition can be effectively guided during subsequent printing, improving the geometric fit of the final implant on the edge structure.

[0042] In step S104, the printed part undergoes surface cleaning and low-temperature drying, followed by sterilization and aseptic packaging according to medical requirements. This is a supplementary step in the printing process, and the overall workflow is highly targeted. Low-temperature drying helps maintain the material's morphological stability and reduces the risk of dimensional shrinkage or deformation caused by temperature sensitivity in thermoplastic materials. Immediate packaging after sterilization helps reduce the possibility of contamination during subsequent transportation and storage, thereby enhancing the safety and structural reliability of the printed part during surgical use.

[0043] In some embodiments, in step S101, the construction of the personalized three-dimensional model uses medical image processing software to segment, reconstruct, and model the patient's CT or MRI image data. During the model construction process, the boundary between the bone defect area and the surrounding anatomical structure is fitted so that the three-dimensional model can correspond to the actual anatomical structure. The medical image processing software used is Mimics, 3-matic, or Freeform.

[0044] This embodiment further defines the construction method of the 3D model in step S101, namely, using medical image processing software to preprocess the patient's CT or MRI image data, and sequentially completing image segmentation, geometric reconstruction, and solid modeling. Through embedding fitting algorithms, a continuous transition can be formed between the defect edge region and the surrounding skull structure, especially when dealing with fracture boundaries and irregular curved surfaces, effectively restoring the original anatomical contour. The selected medical image processing software, such as Mimics, 3-matic, or Freeform, possesses good stability and operational accuracy in medical modeling applications, effectively improving the completeness of the model construction and the restoration of local details.

[0045] The accuracy of this 3D model directly affects the generation of the subsequent printing path and the direction of material deposition. Using this personalized 3D model not only improves the fit of the printing path to the actual bone defect morphology but also helps optimize the uniformity of polymer material distribution in complex edge areas, thereby reducing the burden of preoperative structural adjustments and intraoperative trimming. The resulting implant exhibits superior dimensional coordination and structural continuity, contributing to improved postoperative biomechanical support and enhanced clinical implant stability.

[0046] In some embodiments, the polymer material is selected from one or more mixtures of polycaprolactone, polylactic acid, polylactic acid-glycolic acid copolymer, and polyetheretherketone.

[0047] Building upon the aforementioned embodiments, this embodiment further specifies the types of molding materials used. The selected polymer materials include one or more combinations of polycaprolactone (PCL), polylactic acid (PLA), polylactic-glycolic acid copolymer (PLGA), and polyetheretherketone (PEEK). These materials exhibit good performance in terms of thermoplasticity, biocompatibility, and basic mechanical properties, and can adapt to the material delivery and deposition requirements under differentiated temperature control and dual-nozzle structures. Regarding material performance selection, using biodegradable polymers such as PCL or PLA allows for gradual degradation during tissue healing, helping to reduce the possibility of long-term foreign body retention after implantation. Using PEEK enhances the overall mechanical support capacity of the component, making it particularly suitable for cranial areas subjected to significant stress. Furthermore, in practical applications, mixing different types of polymer materials as molding materials allows for the spatial implementation of functionally graded structural layouts based on the actual needs of the repair site.

[0048] In some embodiments, hydroxyapatite or β-tricalcium phosphate is further added to the polymer material.

[0049] Building upon the aforementioned embodiments, this embodiment further introduces hydroxyapatite (HAP) or β-tricalcium phosphate (β-TCP) as inorganic components into the polymer material, thereby enhancing the osseointegration potential of the printed components at the material composition level. Hydroxyapatite, due to its composition being highly similar to the inorganic minerals in natural bone tissue, possesses excellent bioactivity and can promote the adhesion, proliferation, and differentiation of osteocytes on the material surface; while β-tricalcium phosphate releases calcium and phosphorus ions during its gradual degradation, providing a favorable environment for the formation of new bone tissue.

[0050] This embodiment utilizes the aforementioned inorganic components in conjunction with the polymer matrix, enabling the printed layer to maintain basic mechanical properties while possessing strong bioresponsiveness. This facilitates the establishment of an effective tissue integration interface in the early post-implantation stage. In applications such as skull defect repair, which demand high levels of bone regeneration, this approach reduces adverse reactions caused by interfacial stress mismatch, enhances the compatibility of the material with surrounding bone tissue, and thus helps improve the bonding stability and long-term safety between the component and the host bone.

[0051] In some embodiments, the temperature control range for the fully molten state is 5°C to 30°C above the melting point of the polymer material, and the temperature control range for the semi-molten state is 10°C below the melting point of the polymer material to between the melting point and the melting point.

[0052] In the above embodiments, by clearly defining the temperature control range during the heating process of the polymer material, the heating temperature of the fully molten state is set between 5°C and 30°C above the melting point, and the heating temperature of the semi-molten state is controlled between 10°C below the melting point and the melting point. This segmented temperature control strategy helps to stably form two material states with different rheological properties, improving the controllability of the material output state and the continuity of the deposition process during printing. The polymer material heated to the fully molten state has strong fluidity, suitable for high-speed extrusion and continuous deposition to form the main structure of the printed layer. The polymer material heated to the semi-molten state retains a certain degree of viscoelasticity, allowing it to penetrate into the microporous areas of the previous printed layer after extrusion, thereby strengthening the physical fusion of the interlayer structure. Furthermore, controlling the heating temperature of the semi-molten state between 10°C below the melting point and the melting point avoids material performance imbalance. If the temperature of the polymer material in the semi-molten state is too low, insufficient adhesion may affect the interlayer bonding; if the temperature is too high, the material may lose its necessary shape support. Overall, this thermal control design maintains the stability of material forming while helping to enhance the contact strength between printed layers, thus improving the overall mechanical performance of the printed components from both structural continuity and finished product density dimensions.

[0053] Optionally, in step S104, the sterilization process is ethylene oxide sterilization or low-temperature plasma sterilization, and the low-temperature drying process is constant temperature vacuum drying, with a drying temperature of 30-50℃ and a drying time of 10-40 min.

[0054] The cleaning process in step S104 includes two stages: ultrasonic cleaning and purified water rinsing.

[0055] The first stage is the ultrasonic cleaning stage, in which the printed solid part is placed in a neutral cleaning solution at a temperature of 30℃~45℃, and ultrasonic waves with a frequency of 20kHz~40kHz are used to clean it for 3~10 minutes to remove residual substances and tiny particles from the surface and pores of the printed part.

[0056] The second stage is the purified water rinsing stage, in which deionized purified water is used to repeatedly rinse the ultrasonically cleaned printed parts from multiple angles to ensure that there are no chemical residues or visible contaminants on the surface.

[0057] In this embodiment, by further refining the cleaning and sterilization process in step S104, the adaptability and stability of the printed parts in medical applications are improved from multiple aspects. Specifically, a two-stage cleaning process consisting of ultrasonic cleaning and purified water rinsing can effectively remove dust, free particles, and some potentially adsorbed chemical residues formed during the printing process. In the first stage, the printed parts are immersed in a neutral cleaning solution at 30℃~45℃ and subjected to ultrasonic waves at a frequency of 20kHz~40kHz for 3~10 minutes. The microbubbles generated by the cavitation effect of the sound waves in the liquid perform non-contact cleaning of the surface and micropores of the printed parts, which can reduce the risk of structural damage. In the second stage, deionized purified water is used to rinse from multiple angles, which helps to further remove residual cleaning solution and its potential impurities, improve the cleanliness of the printed parts surface, and reduce possible sources of contamination.

[0058] After cleaning, a constant-temperature vacuum drying process is performed. By controlling the temperature within the range of 30℃ to 50℃ and the time within the range of 10 to 40 minutes, the risk of deformation caused by high temperature can be effectively reduced, while also minimizing moisture retention and stabilizing the structure of the printed parts. The subsequent sterilization step can use ethylene oxide sterilization or low-temperature plasma sterilization. Both methods are effective in killing bacteria, viruses, fungi, and other microorganisms, and are suitable for heat-sensitive polymer materials, helping to maintain their physical properties.

[0059] This embodiment employs a multi-stage cleaning and final sterilization process, addressing material protection, surface treatment, and biosafety control. This reduces the risk of postoperative infection caused by residual impurities or improper sterilization, providing a higher level of protection for printed parts entering a sterile surgical environment.

[0060] In some embodiments, the 3D printing apparatus is configured with a dual-nozzle structure consisting of a first nozzle and a second nozzle, and two temperature chambers capable of heating the polymer material in a differentiated temperature control manner as different temperature control zones.

[0061] The first and second nozzles are arranged in parallel with their nozzle outlets on the same plane. The first and second nozzles are arranged sequentially in the printing path direction. The first nozzle is located at the front of the printing path and is used to extrude fully molten polymer material to print the main structure of the current printed layer. The second nozzle is located after the first nozzle and is used to extrude and deposit semi-molten polymer material in the interface area between the current printed layer and the previous printed layer. The two temperature chambers consist of a first temperature chamber and a second temperature chamber. The first temperature chamber is connected to the first nozzle and is used to heat a portion of the polymer material to a fully molten state. The second temperature chamber is connected to the second nozzle and is used to heat another portion of the polymer material to a semi-molten state.

[0062] In this embodiment, by introducing a dual-nozzle structure and a dual-temperature chamber configuration into the 3D printing device, the heating and deposition processes of the polymer material exhibit a clear division of labor and good synergy. The first and second nozzles are arranged in parallel, with their outlets at the same horizontal height, facilitating synchronous extrusion along a preset path. Structurally, the two nozzles are arranged one after the other along the printing path: the first nozzle in front extrudes the material heated to a fully molten state to construct the main morphology of the current layer; the second nozzle following behind deposits the material in a semi-molten state at the interface between the new layer and the previous layer. With this "front-end forming, rear-end assisting" nozzle layout, the material forms a consistent, continuous interlayer structure during deposition, which helps to enhance the adhesion and overall structural stability of the printed part in the vertical layer direction.

[0063] Furthermore, the addition of two temperature chambers introduces more convenient adjustment capabilities to the temperature control process. The first temperature chamber, used in conjunction with the first nozzle, heats a portion of the polymer material to a fully molten state above its melting point for rapid spreading and molding. The second temperature chamber, connected to the second nozzle, heats another portion of the polymer material to a temperature range close to but 10°C below its melting point, placing it in a semi-molten state, thus maintaining both fluidity and controllable adhesion. This dual-chamber, separately controlled heating strategy helps reduce temperature fluctuations during heat transfer, minimizing adhesion instability caused by uneven heating, while simultaneously improving interfacial fusion during deposition.

[0064] As can be seen, the embodiments of this application construct a collaborative molding logic of "structure construction + interface optimization" through the combined application of a dual-nozzle structure and a dual-temperature chamber. On the one hand, it improves printing efficiency and shortens the processing cycle of printed parts; on the other hand, through the effective filling and fusion of interlayer micropores by semi-molten materials, it reduces the degree of interface weakening between printed layers, thereby reducing structural hazards caused by delamination, warping, or peeling, and contributing to the balanced development of overall mechanical properties and stable performance during use.

[0065] Figure 2 One available dual-nozzle structure is shown, such as Figure 2 As shown, the first nozzle 100 and the second nozzle 200 are arranged in parallel and their nozzle outlets 300 are on the same plane. The first temperature chamber 400 is connected to the first nozzle 100, and the second temperature chamber 500 is connected to the second nozzle 200. Moreover, the first temperature chamber 400 and the second temperature chamber 500 are each connected to a feeding chamber 600.

[0066] In practical applications, the arrangement of the dual-nozzle structure and dual-temperature chambers can be adjusted according to specific structural requirements and operating habits. For example, the two temperature chambers can be placed at the top or rear of the printing device, and the two nozzles can be fed through independent feeding paths. The feeding chamber 600 can adopt a common hot-melt extrusion type filament feeding mechanism to correspond to two materials with different temperature control requirements, ensuring that they complete the required heat treatment process before entering the nozzles. In addition, the distance between the first and second nozzles can be set according to the printing path and material deposition requirements to achieve coordinated material laying and interface transition.

[0067] It should be noted that the above structure is only an exemplary configuration of the embodiments of this application. Those skilled in the art can design a variety of equivalent structural configurations based on the description of this application and in combination with existing equipment and actual application requirements. For example, by using commercially available dual-nozzle FDM printing equipment, the technical solution of this application can be realized under the premise of ensuring control of different temperature ranges and the printhead matching path, which also falls within the protection scope of this application.

[0068] For example, FDM printing equipment with independent temperature control for dual nozzles, such as Raise3D Pro2, Ultimaker S5, and BCN3D Sigma D25, can be used. Combined with the structural configuration and control strategy described in this embodiment, a printing method can be achieved where one nozzle deposits fully molten material while the other nozzle simultaneously deposits semi-molten material, thereby meeting the functional requirements and molding requirements of complex skull implants.

[0069] In some embodiments, the distance between the nozzle outlet centers of the first nozzle and the second nozzle is 8mm to 15mm.

[0070] In this embodiment, limiting the center-to-center distance between the nozzle exits of the first and second nozzles to 8mm to 15mm helps to coordinate the deposition of fully molten and semi-molten materials. During the printing process, the first nozzle first extrudes polymer heated to a fully molten state to form the main structure of the current printed layer. Immediately afterwards, the second nozzle precisely deposits the semi-molten material into the interface region between the current and previous layers to enhance interlayer adhesion. The spacing between the two nozzles is crucial for achieving optimal results in this "pre-forming, post-fusion" process.

[0071] If the distance between the two nozzles is too close, the ejected material is prone to thermal disturbance in the high-temperature region before it cools down, which may affect the stability of the deposition path and the clarity of the structure. Conversely, if the distance is too large, the temperature of the material ejected by the second nozzle will drop significantly before reaching the target area, reducing the material's fluidity and penetration ability, thus affecting its interfacial fusion with the previous layer. Therefore, controlling the center distance between the nozzle exits within a reasonable range of 8mm to 15mm allows for the deposition of semi-molten material within the time window before significant heat dissipation, which helps improve the local thermal fusion and physical bonding effect between the two layers.

[0072] Therefore, this spacing setting not only optimizes the material response time during the printing process but also has a positive impact on the continuity and density of the final printed structure. This method in this embodiment can suppress uneven interface cooling and poor adhesion, which helps reduce the risk of interlayer delamination and enhances the anti-delamination ability and long-term stability of the molded structure.

[0073] In addition, this application embodiment also provides a 3D printed implant for skull defect repair, which is manufactured using the 3D printing interlayer reinforcement molding method for skull defect repair given in the above-described embodiment of this application.

[0074] In this embodiment, the 3D-printed implant for skull defect repair is fabricated using the enhanced molding method described in the above embodiments, exhibiting excellent performance in terms of structural stability and interlayer bonding strength. Throughout the molding process, the coordinated operation of the dual-nozzle structure allows for the simultaneous deposition of fully molten and semi-molten materials, thereby constructing a composite interface with good permeability between the printed layers. This interface helps enhance the physical connection strength between adjacent layers, reducing structural defects such as delamination and cracking caused by weak interlayer bonding in traditional 3D printing processes.

[0075] In terms of morphological construction, contour fitting is achieved through personalized 3D modeling based on medical image data, ensuring that the printed implant geometrically fits the patient's skull defect area well, thus improving the fit between the pre-designed model and the intraoperative application. Simultaneously, the polymer materials used can include polylactic acid, polycaprolactone, and other polymers, or functional fillers such as hydroxyapatite or β-tricalcium phosphate can be introduced to enhance bone integration and promote new bone formation, thus addressing both mechanical support and bioactivity requirements at the material level. In this way, the implant not only possesses high printing precision and mechanical reliability but also meets the dual requirements of biocompatibility and tissue induction properties in cranioplasty, providing a more practical and personalized implant material solution for craniocervical surgery.

[0076] In some embodiments, the height of each printed layer of the implant is controlled between 0.05 mm and 0.15 mm.

[0077] In this embodiment, the 3D-printed implant for skull defect repair achieves more precise and stable layer stacking during the molding process by controlling the layer height of each printed layer between 0.05mm and 0.15mm. This layer height setting matches the dynamic rhythm of the first and second nozzles depositing fully molten and semi-molten polymer materials respectively, resulting in more uniform material layering and facilitating the formation of a naturally transitional interface structure. By refining the deposition thickness, the local fusion between materials can be enhanced, improving the interlayer bonding quality and reducing the risk of delamination.

[0078] A smaller layer height also improves the detail reproduction of the printed surface, resulting in smoother transitions at the edges of the component. When the implant is placed over a defect area, it reduces the feeling of stepping at the edges, helping to alleviate soft tissue irritation and pressure on the contact area. Simultaneously, a layer height set within the aforementioned range facilitates more even transmission and release of external forces within the component, enhancing overall mechanical continuity at the structural level. During the long-term stress and tissue healing phase after implantation, these structural characteristics play a positive role in maintaining the stable fixation of the implant.

[0079] It should be noted that different types of 3D-printed medical implants can select different layer height parameters according to their functional differences. This embodiment is aimed at the repair of hard tissues of the skull. Unlike bone substitute materials that tend to have loose structures and high porosity, this embodiment controls the layer height of the printing parameters between 0.05mm and 0.15mm, which helps to improve the stacking quality of fine structures and the bio-interface compatibility.

[0080] It should be noted that during the implementation of the 3D printing interlayer reinforcement molding method provided in this application embodiment, the ejection rhythm and temperature control accuracy of the dual nozzles should be reasonably controlled to ensure the synergistic consistency of the fully molten and semi-molten materials during the deposition process. If the extrusion rate or path deviation of the molten material in the first nozzle is too large, it may cause the subsequent semi-molten material to be difficult to accurately deposit in the interlayer bonding area, affecting the interface fusion effect. In addition, the temperature and humidity of the printing environment should also be kept stable to avoid fluctuations in material properties due to environmental fluctuations, especially in the molding of detailed structures or curved transition areas. The layer height and printing speed should be appropriately adjusted according to the specific modeling structure to avoid molding errors. For the sterilization and encapsulation of the implant, medical-grade sterile consumables should be selected to ensure that the end product meets the requirements for clinical use and to avoid affecting intraoperative safety and postoperative stability due to non-standard operation.

[0081] Furthermore, with the continuous advancement of personalized medicine and intelligent manufacturing technologies, the 3D printing interlayer reinforcement molding method for skull defect repair proposed in this application has good scalability and engineering transformation potential. In the future, regarding the material system, novel functional fillers such as controllable release growth factors and bioactive microspheres can be further introduced to enhance the tissue induction capacity and regeneration promotion effect of the repaired structure. In terms of clinical applications, this technology is expected to be expanded to various indications such as complex craniocervical defects and pelvic reconstruction. Combined with preoperative navigation and intraoperative positioning methods, it can provide higher-precision technical support for customized bone structure reconstruction. Overall, the molding method provided in this application has undergone multiple molding verifications in an experimental environment, demonstrating good operability and laying a practical foundation for subsequent industrial applications.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A 3D printing interlayer reinforcement molding method for skull defect repair, characterized in that, Includes the following steps: S101: Based on medical imaging data of the patient's skull defect area, construct a personalized 3D model that matches the anatomical structure of the bone defect area and generate path data for 3D printing. S102: Select medical-grade polymer materials with thermoplasticity and biocompatibility, and use a 3D printing device to heat the polymer materials in a differentiated temperature control manner by setting different temperature control areas, so that a part of the polymer material reaches a completely melted state and another part of the polymer material reaches a semi-melted state. S103: A 3D printing device is used to simultaneously extrude and deposit fully molten and semi-molten polymer materials along a preset path using a dual-nozzle structure. Based on three-dimensional model data, the device controls the process to sequentially complete the molding and construction of each printing layer, forming a solid that matches the structure of the bone defect area. The fully molten material is extruded along the front end of the printing path to form the main structure of the current printing layer, while the semi-molten material is extruded immediately behind the fully molten material and deposited into the interface area between the current printing layer and the previous printing layer to penetrate into the surface pores of the previous printing layer. S104: Perform surface cleaning and low-temperature drying on the printed solid parts, and sterilize and aseptically package them according to medical use requirements.

2. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 1, characterized in that, In step S101, the personalized three-dimensional model is constructed by using medical image processing software to segment, reconstruct, and model the patient's CT or MRI image data. During the model construction process, the boundaries between the bone defect area and the surrounding anatomical structure are fitted to ensure that the three-dimensional model corresponds to the actual anatomical structure. The medical image processing software used is Mimics, 3-matic, or Freeform.

3. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 1, characterized in that, The polymer material is selected from one or more mixtures of polycaprolactone, polylactic acid, polylactic acid-glycolic acid copolymer and polyetheretherketone.

4. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 3, characterized in that, The polymer material is further compounded with hydroxyapatite or β-tricalcium phosphate.

5. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 1, characterized in that, The temperature control range for the fully molten state is 5°C to 30°C above the melting point of the polymer material, and the temperature control range for the semi-molten state is 10°C below the melting point of the polymer material to between the melting point and the melting point.

6. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 1, characterized in that, In step S104, the sterilization process is ethylene oxide sterilization or low-temperature plasma sterilization, and the low-temperature drying process is constant temperature vacuum drying, with a drying temperature of 30-50℃ and a drying time of 10-40 min. The cleaning process described in step S104 includes two stages: ultrasonic cleaning and purified water rinsing. The first stage is the ultrasonic cleaning stage, in which the printed solid part is placed in a neutral cleaning solution at a temperature of 30℃~45℃, and ultrasonic waves with a frequency of 20kHz~40kHz are used to clean it for 3~10 minutes to remove residual substances and tiny particles from the surface and pores of the printed part. The second stage is the purified water rinsing stage, in which deionized purified water is used to repeatedly rinse the ultrasonically cleaned printed parts from multiple angles to ensure that there are no chemical residues or visible contaminants on the surface.

7. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 1, characterized in that, The 3D printing device used is equipped with a dual-nozzle structure consisting of a first nozzle and a second nozzle, as well as two temperature chambers that can heat the polymer material in a differentiated temperature control manner as different temperature control zones. The first and second nozzles are arranged in parallel with their nozzle outlets on the same plane. The first and second nozzles are arranged sequentially in the printing path direction. The first nozzle is located at the front of the printing path and is used to extrude fully molten polymer material to print the main structure of the current printed layer. The second nozzle is located after the first nozzle and is used to extrude and deposit semi-molten polymer material in the interface area between the current printed layer and the previous printed layer. The two temperature chambers consist of a first temperature chamber and a second temperature chamber. The first temperature chamber is connected to the first nozzle and is used to heat a portion of the polymer material to a fully molten state. The second temperature chamber is connected to the second nozzle and is used to heat another portion of the polymer material to a semi-molten state.

8. The 3D printing interlayer reinforcement molding method for skull defect repair according to claim 7, characterized in that, The distance between the nozzle outlet centers of the first nozzle and the second nozzle is 8mm to 15mm.

9. A 3D-printed implant for repairing skull defects, characterized in that, It is manufactured using the 3D printing interlayer reinforcement molding method for skull defect repair as described in any one of claims 1 to 8.

10. The 3D-printed implant for skull defect repair according to claim 9, characterized in that, The height of each printed layer of the implant is controlled between 0.05mm and 0.15mm.

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