3D printing interlayer reinforcement forming method for skull defect repair and implant

Abstract

The invention provides a 3D printing interlayer enhancement forming method for skull defect repair, and belongs to the technical field of 3D printing and medical implant manufacturing, and the method comprises the following steps: 1, based on medical imaging data of a skull defect area of a patient, constructing a personalized three-dimensional model matched with an anatomical structure of the skull defect area, and generating path data for 3D printing; 2, for the selected medical-grade polymer material, a 3D printing device is adopted to heat the polymer material in a differentiated temperature control mode by setting different temperature control areas; 3, a 3D printing device is adopted in the preset path direction, materials in different states are synchronously extruded and deposited through the double-spray-head structure, and finally an entity matched with the bone defect area structure is formed; and 4, carrying out surface cleaning and low-temperature drying treatment on the printed piece, and carrying out sterilization and sterile packaging according to medical use requirements. According to the invention, on the premise that the printing efficiency is not influenced, the tightness degree of interlayer bonding can be obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of 3D printing and medical implant manufacturing technology, in particular to a 3D printing interlayer reinforced forming method for skull defect repair and an implant. BACKGROUND

[0002] With the development of personalized medical technology, three-dimensional printing technology (3D printing) is increasingly widely used in the customized manufacturing of medical implants, especially in the field of skull defect repair. Based on medical imaging modeling and three-dimensional printing, the customized repair scheme has become one of the main development directions to improve the postoperative matching degree and structural stability. At present, medical grade thermoplastic polymers are widely used in the manufacturing of bone defect repair printing implants due to their good biocompatibility, biodegradability and forming adaptability.

[0003] In the traditional process of individualized 3D printing skull implant preparation, the polymer material is usually extruded and deposited by a single nozzle layer by layer through a hot melt extrusion (FDM) device to form a layered structure of the solid model. Its printing path depends on the preset three-dimensional path data, and the rapid cooling and solidification of the molten material are used to realize layer-by-layer construction. Some devices can optimize the printing precision and surface quality by setting the temperature of the temperature zone and adjusting the nozzle moving speed and printing rhythm, but most of them are still in the "isothermal" extrusion mode, that is, the material is basically in the same heating state during printing, and the formation of the whole layer structure is completed.

[0004] However, the existing single nozzle isothermal printing mode is prone to insufficient adhesion between different printing layers during layer-by-layer construction, especially in complex curved surfaces or large-span parts. The interface fusion between the thermoplastic material after deposition and cooling and the previous layer is not sufficient, resulting in a decrease in interface bonding strength, and the layer-by-layer connection is prone to peeling, cracking or local fracture, which seriously affects the overall structural integrity and postoperative stability of the finished implant. Especially in clinical scenarios where skull structure requires high adhesion and mechanical uniformity, the interlayer bonding quality becomes an important bottleneck limiting the long-term reliability of the printed implant.

[0005] In summary, how to effectively enhance the bonding quality between each printing layer while ensuring the individualized printing precision, so as to improve the continuity and interface strength of the overall structure of the implant, is a key technical problem that needs to be solved in the current 3D printing manufacturing technology for skull defect repair. SUMMARY

[0006] The present application provides a 3D printing interlayer reinforced forming method for skull defect repair and an implant to solve the problem of insufficient interlayer bonding of the current 3D printed skull defect repair implant.

[0007] In one aspect, the present application provides a 3D printing interlayer reinforced forming method for cranioplasty, comprising the following steps: S101: Based on the medical imaging data of the skull defect area of the patient, a personalized three-dimensional model is constructed to match the anatomical structure of the bone defect area, and path data for 3D printing is generated; S102: Selecting a medical-grade polymer material with thermoplasticity and biocompatibility, using a 3D printing device to heat the polymer material in a differentiated temperature control manner by setting different temperature control areas, so that part of the polymer material reaches a completely molten state, and another part of the polymer material reaches a semi-molten state; S103: Using a 3D printing device, the polymer material in a completely molten state and a semi-molten state is synchronously extruded and deposited along the preset path direction by a double-nozzle structure, controlled based on three-dimensional model data, and the forming construction of each printing layer is completed in turn to form a structure matching the bone defect area; wherein the completely molten state material is extruded at the front end of the printing path to print the main structure of the current printing layer, and the semi-molten state material is extruded and deposited to the interface area between the current printing layer and the previous printing layer at the rear side of the extrusion position of the completely molten state material to penetrate into the surface pores of the previous printing layer; S104: The surface of the printed entity is cleaned and dried at low temperature, and sterilized and aseptically packaged according to the medical use requirements.

[0008] As an optional way of the present application, in step S101, the construction of the personalized three-dimensional model uses medical image processing software to segment, reconstruct and entity model the CT or MRI image data of the patient, and in the model construction process, the three-dimensional model is fitted to the actual anatomical structure by fitting the bone defect area and the surrounding anatomical structure boundary; the medical image processing software used is Mimics, 3-matic or Freeform.

[0009] As an optional way of the present application, the polymer material is selected from one or more mixtures of polycaprolactone, polylactic acid, poly-lactic-glycolic acid copolymer and polyether ether ketone.

[0010] As an optional way of the present application, hydroxyapatite or β-tricalcium phosphate is further compounded and added to the polymer material.

[0011] As an optional way of the present application, the temperature control range of the completely molten state is 5-30°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 the melting point.

[0012] As an optional mode of the present application, in step S104, the sterilization treatment is ethylene oxide sterilization or low-temperature plasma sterilization, and the low-temperature drying treatment is constant-temperature vacuum drying, the drying temperature is 30-50°C, and the drying time is 10-40 min.

[0013] As an optional mode of the present application, the cleaning process in step S104 includes two stages of ultrasonic cleaning and purified water rinsing: The first stage is the ultrasonic cleaning stage, the printed entity after printing is placed in a neutral cleaning liquid with a temperature of 30-45°C, and ultrasonic waves with a frequency of 20-40 kHz are used for action, the cleaning time is 3-10 min, which is used to remove residual substances and small particles in the pores and on the surface of the printed part; The second stage is the purified water rinsing stage, deionized purified water is used to repeatedly rinse the printed part after ultrasonic cleaning at multiple angles, so that there is no chemical residue and visible pollution on the surface.

[0014] As an optional mode of the present application, the 3D printing device used is configured with a double-nozzle structure composed of a first nozzle and a second nozzle, and two temperature bins capable of heating polymer materials in different temperature control modes as different temperature control areas; Among them, the first nozzle and the second nozzle are arranged in parallel and the nozzle outlets of the two are in the same plane, the first nozzle and the second nozzle are sequentially arranged front and back in the printing path direction, the first nozzle is located on the front side of the printing path, used to extrude the polymer material in a completely molten state to print the main structure of the current printing layer, the second nozzle is arranged behind the first nozzle, used to extrude and deposit the polymer material in a semi-molten state in the interface area between the current printing layer and the previous printing layer; the two temperature bins are composed of a first temperature bin and a second temperature bin, the first temperature bin is connected with the first nozzle, used to heat a part of the polymer material to a completely molten state, and the second temperature bin is connected with the second nozzle, used to heat another part of the polymer material to a semi-molten state.

[0015] As an optional mode of the present application, the distance between the center of the nozzle outlet of the first nozzle and the center of the nozzle outlet of the second nozzle is 8-15 mm.

[0016] On the other hand, the present application also provides a 3D printed implant for repairing skull defects, which is made by using the above-mentioned 3D printed interlayer reinforcing forming method for repairing skull defects provided by the present application.

[0017] As an optional mode of the present application, the height of each printing layer of the implant is controlled to be between 0.05 mm and 0.15 mm.

[0018] Compared with the prior art, the present application has the following beneficial effects: 1. The present application provides a 3D printing interlayer reinforcement forming method and implant for skull defect repair. The present application introduces the idea of "co-deposition of different state materials" in the raw material processing stage. Specifically, the polymer material is divided into two parts and heated in different temperature control areas. One part of the material is heated to a completely molten state above the melting point, with good fluidity and spreading ability, mainly used for printing the main structure of the component; the other part of the material is heated to a semi-molten state close to the melting point but not completely molten, retaining some thermal adhesion and forming ability, suitable for structure transition in the interface area. This kind of regulation method based on the differentiation of material physical state helps to improve the problem of insufficient interlayer adhesion, and provides good thermodynamic conditions for subsequent material penetration and interface fusion.

[0019] 2. The present application uses a 3D printing device with a double-nozzle structure to simultaneously extrude and deposit polymer materials in a completely molten state and a semi-molten state, to achieve the simultaneous deposition of different state materials. The completely molten state material is extruded at the front end of the printing path to print the main structure of the current printing layer, and the semi-molten state material is extruded and deposited to the interface area between the current printing layer and the previous printing layer, following the position behind the completely molten state material, to penetrate into the surface pores of the previous printing layer; this "front shaping, rear penetration" printing forming method makes the material deposition realize the coordinated cooperation of functional partition and transition fusion in space, without affecting the printing efficiency, which can significantly improve the tightness of layer bonding and help to reduce the probability of interface peeling and delamination.

[0020] 3. The present application is based on medical imaging data to construct a personalized three-dimensional model, which is throughout the entire printing process, and can realize high consistency between the printing path and the actual bone defect boundary. In the process of layer-by-layer forming, the extruded material strictly follows the model path for deposition, and with the precise addition of each layer of material in geometry and physical properties, the printed part can exhibit good consistency in macroscopic structural continuity and microscopic interface fusion. Moreover, combined with the physical property advantages of the dual-state material, this method can still maintain high forming quality in areas with complex structure, curved surface transition or large span, further improving the structural stability and biological adaptability of the implant in long-term application. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 A flow chart of a 3D printing interlayer reinforced forming method for skull defect repair is provided for an embodiment of the present application; Figure 2 A schematic diagram of a double nozzle structure arrangement is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0024] As shown in Figure 1 The present application provides a 3D printing interlayer reinforced forming method for skull defect repair, which comprises the following steps: S101: Based on the medical imaging data of the skull defect area of a patient, a personalized three-dimensional model that matches the anatomical structure of the bone defect area is constructed, and path data for 3D printing is generated; S102: Select a medical-grade polymer material with thermoplasticity and biocompatibility, and use a 3D printing device to heat the polymer material in a differentiated temperature control manner by setting different temperature control areas, so that part of the polymer material reaches a completely molten state, and the other part of the polymer material reaches a semi-molten state; S103: Use the 3D printing device to synchronously extrude and deposit the polymer material in the completely molten state and the semi-molten state along the preset path direction by the double nozzle structure, control based on the three-dimensional model data, and sequentially complete the forming construction of each printing layer to form a solid body that matches the structure of the bone defect area; wherein the completely molten state material is extruded at the front end of the printing path to print the main structure of the current printing layer, and the semi-molten state material is extruded at the rear side of the position where the completely molten state material is extruded and deposited to 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 treatment on the printed solid body, and sterilize and aseptically package according to the medical use requirements.

[0025] The embodiment introduces the idea of "co-deposition of different state materials" in the raw material processing stage. Specifically, the polymer material is divided into two parts, which are heated in different temperature control areas. One part of the material is heated to a completely molten state above the melting point, with good fluidity and spreadability, mainly used for printing the main structure of the component; the other part of the material is heated to a semi-molten state close to the melting point but not completely molten, which retains some thermal adhesion and forming ability, suitable for structure transition in the interface area. This kind of regulation based on the differentiation of material physical state helps to improve the problem of insufficient adhesion between layers, and provides good thermodynamic conditions for subsequent material penetration and interface fusion.

[0026] Further, the embodiment uses a 3D printing device with a double-nozzle structure to simultaneously extrude and deposit polymer materials in a completely molten state and a semi-molten state, to realize the simultaneous deposition of different state materials. The completely molten state material is extruded at the front end of the printing path to print the main structure of the current printing layer, and the semi-molten state material is extruded and deposited to the interface area between the current printing layer and the previous printing layer, to penetrate into the surface pores of the previous printing layer; this "front-end structure, rear-end penetration" printing forming method makes the material deposition realize the coordinated cooperation of functional partition and transition fusion in space, which can obviously improve the tightness of layer bonding without affecting the printing efficiency, and helps to reduce the probability of interface peeling and delamination.

[0027] In addition, the embodiment is based on medical imaging data to construct a personalized three-dimensional model, which runs through the entire printing process and can achieve high consistency between the printing path and the actual bone defect boundary. In the process of layer-by-layer forming, the extruded material strictly follows the model path for deposition, and with the precise addition of each layer of material in geometry and physical properties, the printed part can exhibit good consistency in macroscopic structural continuity and microscopic interface fusion. Moreover, with the physical property advantages of the dual-state material, this method can still maintain high forming quality in areas with complex structure, curved turning or large span, further improving the structural stability and biological adaptability of the implant in long-term application.

[0028] Further, in step S101, the embodiment constructs a personalized three-dimensional model based on medical imaging data (such as CT or MRI) of the patient's skull defect area, which can achieve high matching between the printing path data and the target defect boundary. This model not only reflects the spatial form of the defect area, but also can more completely reproduce the curvature change and anatomical structure characteristics of the skull. With this model as the basis for printing, the material deposition direction and level can be effectively guided in the subsequent printing process, improving the geometric adaptability of the final implant on the edge structure.

[0029] In step S104, the surface of the printed entity is cleaned and low-temperature dried, and sterilized and aseptically packaged according to the medical use requirements, as a post-process supplement of the printing process, the overall process arrangement has strong pertinence. The low-temperature drying process helps to maintain the stability of the material form and reduce the risk of size shrinkage or deformation of the thermoplastic material due to temperature sensitivity. After sterilization, the packaging is immediately sealed, which helps to reduce the risk of contamination during subsequent transportation and storage, thereby enhancing the safety and structural reliability of the printed part during intraoperative use.

[0030] 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 entity of the patient's CT or MRI image data, and fits the bone defect area and the surrounding anatomical structure boundary during model construction to enable the three-dimensional model to correspond to the actual anatomical structure; the medical image processing software used is Mimics, 3-matic or Freeform.

[0031] The present embodiment further limits the construction method of the three-dimensional model in step S101, that is, the medical image processing software is used to preprocess the CT or MRI image data of the patient, and sequentially complete image segmentation, geometric reconstruction and entity modeling. By embedding a fitting algorithm, a continuous transition can be formed between the defect edge area and the surrounding skull structure, especially when dealing with broken boundaries and irregular curved surfaces, the original anatomical profile can be better restored. The selected medical image processing software such as Mimics, 3-matic or Freeform has good stability and operation accuracy in medical modeling applications, which can effectively improve the completeness of the model construction and the restoration degree of local details.

[0032] The accuracy of this three-dimensional model directly affects the generation of the subsequent printing path and the direction of material deposition. With the help of this personalized three-dimensional model, not only can the printing path be better fitted to the actual bone defect shape, but also the uniformity of the polymer material in the complex edge area can be optimized, thereby reducing the burden of preoperative structure adjustment and intraoperative modification. The implant formed by the final printing performs better in size coordination and structural continuity, which helps to improve the postoperative mechanical support state and enhance the stability of clinical implantation.

[0033] In some embodiments, the polymer material is selected from one or more mixtures of polycaprolactone, polylactic acid, poly(lactic-co-glycolic acid), and poly(ether ether ketone).

[0034] On the basis of the foregoing embodiments, the present embodiment further limits the type of forming material, and the selected polymer material includes one or more combinations of polycaprolactone (PCL), polylactic acid (PLA), poly(lactic-co-glycolic acid) (PLGA), and polyether ether ketone (PEEK). These materials have good performance in terms of thermoplasticity, biocompatibility, and basic mechanical properties, and can adapt to the material delivery and deposition requirements under the conditions of differential temperature control and double-nozzle structure. In the selection of material properties, if degradable polymers such as PCL or PLA are used, they can gradually degrade during the tissue healing process, which helps to reduce the possibility of long-term foreign body retention after implantation; if PEEK is selected, the mechanical support capacity of the overall component can be enhanced, which is particularly suitable for the skull part that bears a large stress. In addition, in actual application, mixing different types of polymer materials as forming materials can also realize the spatial functional gradient structure layout according to the actual needs of the repair site.

[0035] In some embodiments, hydroxyapatite or β-tricalcium phosphate is further compounded and added to the polymer material.

[0036] On the basis of the foregoing embodiments, the present embodiment further introduces hydroxyapatite (HAP) or β-tricalcium phosphate (β-TCP) as an inorganic component in the polymer material, which can enhance the bone integration potential of the printed component from the material composition level. Hydroxyapatite has a high similarity in composition to the inorganic minerals in natural bone tissue, has good bioactivity, and can promote the adhesion, proliferation, and differentiation of bone cells on the material surface; and β-tricalcium phosphate can release calcium and phosphate ions during the gradual degradation process, providing a favorable environment for the generation of new bone tissue.

[0037] The present embodiment uses the above-mentioned inorganic component together with the polymer matrix, so that the printed layer can have strong biological response ability while maintaining basic mechanical properties, which is beneficial to establishing an effective tissue integration interface in the early stage after implantation. In the application scenario of skull defect repair, which requires high bone regeneration, such a method can reduce adverse reactions caused by mismatched interface stress, enhance the compatibility of the material with the surrounding bone tissue, and thus help to improve the bonding stability and long-term use safety between the component and the host bone.

[0038] In some embodiments, the temperature control range of the completely molten state is 5-30°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 to the melting point of the polymer material.

[0039] In the above embodiments, by explicitly limiting the temperature control interval during the heating of the polymer material, the heating temperature of the completely molten state is set to be 5-30℃ higher than the melting point of the material, and the heating temperature of the semi-molten state is controlled to be 10℃ below the melting point to the melting point, so as to realize distinguishable temperature difference in the heat control operation. This segmented temperature control strategy helps to stably form two material states with different rheological properties, and can improve the state controllability of material output and the continuity of the deposition process during printing. The polymer material heated to the completely molten state has strong fluidity and is suitable for high-speed extrusion and continuous deposition to form the main structure part of the printing layer. The polymer material heated to the semi-molten state retains certain viscoelasticity and can penetrate into the micropore area on the surface of the previous printing layer after extrusion, thereby strengthening the physical fusion of the interlayer structure. Moreover, the heating temperature of the semi-molten state is controlled to be 10℃ below the melting point to the melting point, which can avoid the imbalance of material performance. If the temperature of the polymer material in the semi-molten state is too low, the interlayer bonding may be affected due to insufficient adhesion; if the temperature is too high, the material may lose the necessary shape support force. Overall, this heat control design helps to enhance the contact strength between the printing layers while maintaining the stability of the material forming, thereby improving the overall mechanical performance of the printed component from the aspects of structural continuity and product density.

[0040] Optionally, in step S104, the sterilization treatment is ethylene oxide sterilization or low-temperature plasma sterilization, the low-temperature drying treatment is constant-temperature vacuum drying, the drying temperature is 30-50℃, and the drying time is 10-40min. The cleaning process in step S104 includes two stages of ultrasonic cleaning and purified water rinsing: The first stage is the ultrasonic cleaning stage. The printed entity is placed in a neutral cleaning liquid with a temperature of 30-45℃, and ultrasonic waves with a frequency of 20-40kHz are used for action. The cleaning time is 3-10 minutes, which is used to remove residual substances and small particles on the surface and pores of the printed part; The second stage is the purified water rinsing stage. Deionized purified water is used to repeatedly rinse the printed part after ultrasonic cleaning from multiple angles, so as to make the surface free of chemical residues and visible pollution.

[0041] In this embodiment, the cleaning and sterilization process in step S104 is further refined to improve the adaptability and stability of the printed part in medical application scenarios from multiple aspects. Specifically, a two-stage cleaning process combining ultrasonic cleaning and purified water rinsing can more effectively remove dust, free particles, and some possible chemical residues formed during printing. In the first stage, the formed printed part is immersed in a neutral cleaning solution at 30-45°C and subjected to ultrasonic waves with a frequency of 20-40 kHz for 3-10 minutes. The non-contact cleaning of the printed part surface and micro-pores by the micro-bubbles generated by the cavitation effect of sound waves in the liquid can reduce the risk of structural damage. In the second stage, deionized purified water is used for rinsing from multiple angles to further remove residual cleaning solution and potential impurities, improve the cleaning level of the printed part surface, and reduce possible sources of pollution.

[0042] After cleaning, a constant-temperature vacuum drying process is performed. By controlling the temperature to be 30-50°C and the time to be 10-40 minutes, the risk of deformation caused by high temperature can be effectively reduced, and the water retention can be reduced to stabilize the structure of the printed part. The subsequent sterilization step can use ethylene oxide sterilization or low-temperature plasma sterilization, both of which have good effects in killing bacteria, viruses, and fungi, and are suitable for heat-sensitive polymer materials, which helps to maintain the physical properties of the materials.

[0043] The multi-stage cleaning and final sterilization process of this embodiment reduces the risk of postoperative infection caused by residual impurities or improper sterilization from the aspects of material protection, surface treatment, and biological safety control, and provides higher level protection for the printed part entering the sterile surgical environment.

[0044] In some embodiments, the 3D printing device is configured with a double-nozzle structure composed of a first nozzle and a second nozzle, and two temperature bins capable of heating polymer materials in different temperature control modes as different temperature control areas.

[0045] The first nozzle and the second nozzle are arranged in parallel and their nozzle outlets are in the same plane. The first nozzle and the second nozzle are arranged in sequence in the front-rear direction of the printing path. The first nozzle is located on the front side of the printing path and is used to extrude polymer materials in a completely molten state to print the main structure of the current printing layer. The second nozzle is arranged behind the first nozzle and is used to extrude polymer materials in a semi-molten state and deposit them in the interface region between the current printing layer and the previous printing layer. The two temperature bins are composed of a first temperature bin and a second temperature bin. The first temperature bin is connected to the first nozzle and is used to heat a part of the polymer materials to a completely molten state. The second temperature bin is connected to the second nozzle and is used to heat another part of the polymer materials to a semi-molten state.

[0046] In the embodiment, by introducing the double-nozzle structure and the double-temperature bin configuration in the 3D printing device, the heating and deposition process of the polymer material presents a clear division of labor relationship and good cooperation. The first nozzle and the second nozzle are arranged in parallel, and the nozzle outlets are at the same horizontal height, which facilitates the synchronous extrusion along the preset path. Structurally, the two nozzles are arranged in front and back along the printing path direction: the front first nozzle is used to extrude the material heated to a completely molten state to build the main topography of the current layer; the second nozzle following it deposits the material in a semi-molten state between the new layer and the previous layer. With this "front forming and rear assisting" nozzle layout, the material forms a structure with consistent direction and continuous layers during the deposition process, which helps to enhance the bonding strength and overall structural stability of the printed part in the vertical layer direction.

[0047] Further, the addition of two temperature bins introduces more convenient adjustment capability for the temperature control process. The first temperature bin is used with the first nozzle to heat part of the polymer material to a completely molten state above the melting point for rapid spreading and forming; the second temperature bin is connected with the second nozzle to heat another part of the polymer material to a temperature interval close to the melting point but 10°C below the melting point, so that it is in a semi-molten state with certain flowability and controllable bonding performance. This double-bin controlled heating strategy helps to reduce temperature fluctuations in the heat transfer process, reduce the problem of unstable bonding caused by uneven heating, and improve the interface fusion effect of the material during the deposition process.

[0048] As can be seen, the embodiment of the application constructs a "structure construction + interface optimization" collaborative forming logic by the combined application of the double-nozzle structure and the double-temperature bin. On the one hand, it improves the printing efficiency and shortens the processing cycle of the printed part; on the other hand, by effectively filling and fusing the interlayer micropores with semi-molten material, it reduces the interface weakening degree between the printed layers, thereby reducing the structural risks caused by problems such as delamination, warping or delamination, and helps to balance the overall mechanical properties and stable performance during use.

[0049] Figure 2 A usable double-nozzle structure form is shown as Figure 2 As shown, the first nozzle 100 and the second nozzle 200 are arranged in parallel and the nozzle outlets 300 of the two nozzles are in the same plane, the first temperature bin 400 in the two temperature bins is connected with the first nozzle 100, the second temperature bin 500 is connected with the second nozzle 200, and the first temperature bin 400 and the second temperature bin 500 are respectively connected with a feeding bin 600.

[0050] In practical applications, the arrangement of the double-nozzle structure and the double-temperature bin can be adjusted according to specific structural requirements and operation habits. For example, the two temperature bins can be arranged at the top or rear side of the printing device, and the two nozzles can be supplied with materials through independent feeding paths. The feeding bin 600 can adopt a common hot-melt extrusion type wire feeding mechanism, which corresponds to two materials with different temperature control requirements, to ensure that the required heat treatment process is completed before the materials enter the nozzles. In addition, the distance between the first nozzle and the second nozzle can be set according to the printing path and the material deposition requirements to achieve the coordinated laying and interface transition of the materials.

[0051] It should be noted that the above structure is only an exemplary configuration form of the embodiments of the present application. Those skilled in the art can design various equivalent structural configuration forms under the inspiration of the content of the present application, in combination with existing equipment and actual application requirements. For example, the current commercially available double-nozzle FDM printing equipment can be used to realize the technical solutions of the present application under the premise of ensuring different temperature interval control and nozzle cooperation path, which also belongs to the protection scope of the present application.

[0052] For example, the Raise3D Pro2, Ultimaker S5, BCN3D Sigma D25, etc. FDM printing equipment with double-nozzle independent temperature control function can be selected, and the structure configuration and control strategy described in the present embodiment can be combined to realize the printing mode of depositing completely molten materials by one nozzle and synchronously depositing semi-molten materials by the other nozzle, thereby meeting the functional requirements and forming requirements of complex skull implants.

[0053] In some embodiments, the distance between the nozzle outlet centers of the first nozzle and the second nozzle is 8mm-15mm.

[0054] In the present embodiment, by limiting the distance between the nozzle outlet centers of the first nozzle and the second nozzle to 8mm-15mm, the deposition cooperation of the completely molten materials and the semi-molten materials is facilitated. During the printing process, the first nozzle first extrudes the polymer heated to a completely molten state, which is used to form the main structure of the current printing layer. Then, the second nozzle precisely deposits the material in a semi-molten state in the interface region between the current layer and the previous layer to enhance the interlayer adhesion. In order to achieve good results of this “pre-forming and post-fusion” cooperation, the distance between the two nozzles is particularly important.

[0055] If the distance between the two spray heads is too close, the sprayed material is prone to thermal disturbance in the high-temperature area before it cools down, which may affect the stability of the deposition path and the structural clarity. Conversely, if the distance is too large, the temperature of the material sprayed by the second spray head drops significantly before it reaches the target area, reducing the flowability and permeability of the material, which affects the interface fusion effect with the previous layer. Therefore, controlling the distance between the centers of the spray head outlets within a reasonable range of 8mm to 15mm can complete the deposition of the semi-molten material within the time window when the heat has not yet been significantly dissipated, which helps to improve the local thermal fusion and physical occlusion effect between the two layers.

[0056] In this way, the distance setting not only optimizes the material response time during printing, but also has a positive impact on the continuity and density of the overall structure of the final printed part. This way of the embodiment can inhibit the problem of uneven interface cooling and poor bonding, which is conducive to reducing the risk of layer separation and enhancing the anti-layering ability and long-term stability of the formed structure.

[0057] In addition, the present application also provides a 3D printed implant for repairing skull defects, which is made by the 3D printing interlayer enhancement forming method for repairing skull defects provided in the embodiments of the present application.

[0058] In the present embodiment, the 3D printed implant for repairing skull defects is made by the enhancement forming method in the above embodiments, which performs excellently in structural stability and interlayer bonding strength. During the entire forming process, the cooperation of the double spray head structure can simultaneously complete the layered deposition of fully molten material and semi-molten material, and then build a composite interface with good permeability between the printed layers. This interface helps to enhance the physical connection strength between adjacent layers and reduce the structural defects such as layering and cracking caused by weak interlayer bonding in the traditional 3D printing process.

[0059] In terms of shape construction, the contour fitting is performed by the personalized three-dimensional modeling method based on medical image data, so that the printed implant can better fit the skull defect area of the patient in terms of geometric shape, improving the fit between the preoperative preset model and the intraoperative application. At the same time, the polymer material can be selected from poly-lactic acid, poly-caprolactone and other polymer materials, and functional fillers such as hydroxyapatite or beta-tricalcium phosphate can also be introduced to enhance the bone integration ability and promote new bone formation, taking into account the mechanical support and biological activity requirements from the material level. In this way, the implant not only has high printing forming precision and mechanical reliability, but also meets the dual requirements of biocompatibility and tissue induction performance in skull repair, providing a more practical personalized implant material solution for craniomaxillofacial surgery.

[0060] In some embodiments, the height of each printed layer of the implant is controlled to be between 0.05mm and 0.15mm.

[0061] In the present embodiment, the 3D-printed implant for repairing skull defects controls the layer height of each printing layer to be between 0.05mm and 0.15mm, so that the layer-by-layer stacking in the forming process is more fine and stable. The layer height setting can match the dynamic rhythm of the first nozzle and the second nozzle respectively depositing completely melted and semi-melted polymer materials, so that the laying of each layer of material is more uniform, which is conducive to forming a transition natural interface structure. By refining the deposition thickness, the local fusion degree between materials can be enhanced, the interlayer bonding quality is improved, and the delamination risk is reduced.

[0062] The smaller layer height can also improve the detail restoration degree of the printing surface, make the edge transition of the component smoother, and reduce the edge step feeling when the implant is fitted in the defect area, which helps to reduce the stimulation of soft tissue and the pressure burden of the contact area. At the same time, the layer height setting in the above range is conducive to more uniform conduction and release of external force inside the component, which enhances the mechanical continuity of the whole from the structural level. During the long-term stress and tissue healing stage after implantation, such structural characteristics have a positive effect on maintaining the stable and fixed state of the implant.

[0063] It should be noted that different types of 3D-printed medical implants can select different layer height parameters according to functional differences. The present embodiment is aimed at repairing skull hard tissue, which is different from bone replacement materials that are biased towards loose structure and high porosity. The present embodiment controls the layer height of the printing parameters to be between 0.05mm and 0.15mm, which helps to improve the stacking quality of fine structures and the biointerface adaptability.

[0064] It should be noted that in the implementation process of the 3D-printed interlayer enhanced forming method provided in the present embodiment, the ejection rhythm and temperature control accuracy of the double nozzles should be reasonably controlled to ensure the consistency of the completely melted and semi-melted materials during the deposition process. If the extrusion rate or path of the melted material of the first nozzle deviates too much, it may be difficult for the subsequent semi-melted material to be accurately deposited in the interlayer bonding area, affecting the interface fusion effect. In addition, the printing environment temperature and humidity should also be kept stable to avoid fluctuations in material performance due to environmental fluctuations, especially in the formation of detailed structures or curved transition parts. The layer height and printing speed should be adjusted appropriately according to the specific modeling structure to avoid forming errors. For the sterilization and packaging of the implant, medical-grade sterile consumables should be selected to ensure that the end product meets the clinical use requirements and avoids affecting the intraoperative safety and postoperative stability due to non-standard operation.

[0065] In addition, with the continuous progress of personalized medicine and intelligent manufacturing technology, the 3D printing interlayer reinforcement forming method for skull defect repair provided by the embodiments of the present application has good expandability and engineering transformation potential. In the future, in terms of material system, new functional fillers such as controllable release growth factors and biologically active microspheres can be further introduced to improve the tissue induction ability and regeneration promotion effect of the repair structure; in terms of clinical application, the technology is expected to be expanded to complex craniofacial bone defects, pelvic reconstruction and other indications, combined with preoperative navigation and intraoperative positioning means, to provide higher precision technical support for customized reconstruction of bone structure. Overall, the forming method provided by the embodiments of the present application has completed multiple forming verifications in the experimental environment, and has good operability, laying a practical foundation for subsequent industrial application.

[0066] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that; it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A 3D printing interlayer reinforcement molding method for skull defect repair, characterized in that: The following steps are involved: S101: Based on the medical imaging data of the patient's skull defect area, a personalized 3D model adapted to the anatomical structure of the bone defect area is constructed, and path data for 3D printing is generated; S102: selecting a medical-grade polymer material with thermoplasticity and biocompatibility, and using a 3D printing device to heat the polymer material in a differentiated temperature-controlled manner by setting different temperature control zones, so that a portion of the polymer material reaches a completely molten state and another portion of the polymer material reaches a semi-molten state; S103: Using a 3D printing device, a dual nozzle structure is used to synchronously extrude and deposit polymer materials in a fully molten state and a semi-molten state along a preset path. Based on the three-dimensional model data, the device is controlled to sequentially complete the molding and construction of each printing layer to form a solid body that matches the structure of the bone defect area. The fully molten state material is extruded along the front end of the printing path to print and form the main structure of the current printing layer. The semi-molten state material is extruded immediately behind the extrusion position of the fully molten state material and deposited at the interface area between the current printing layer and the previous printing layer, so as to penetrate into the surface pores of the previous printing layer. S104: The printed physical part is surface cleaned and low-temperature dried, and sterilized and aseptically packaged in accordance with 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, a 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 bone defect area and the surrounding anatomical structure boundaries 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.

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 beta-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 of the completely 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 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 treatment method is ethylene oxide sterilization or low-temperature plasma sterilization, and the low-temperature drying treatment is constant temperature vacuum drying, the drying temperature is 30-50°C, and the drying time is 10-40 minutes; The cleaning process in step S104 includes two stages: ultrasonic cleaning and purified water rinsing. The first stage is ultrasonic cleaning, which involves placing the printed part in a neutral cleaning solution at a temperature of 30°C to 45°C. Ultrasonic waves with a frequency of 20kHz to 40kHz are used for cleaning for 3 to 10 minutes to remove residual matter and tiny particles on the surface and in the 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 printed parts after ultrasonic cleaning at multiple angles to ensure that there is no chemical residue and visible contamination 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, and two temperature chambers capable of serving as different temperature control areas to heat the polymer material in a differentiated temperature control manner; Among them, the first nozzle and the second nozzle are arranged in parallel and the nozzle outlets of the two are in the same plane. The first nozzle and the second nozzle are arranged in sequence front and back in the direction of the printing path. The first nozzle is located at the front side of the printing path, and is used to extrude the polymer material in a completely molten state to print and form the main structure of the current printing layer. The second nozzle is arranged after the first nozzle, and is used to extrude the semi-molten polymer material immediately following the first nozzle and deposit it in the interface area between the current printing layer and the previous printing layer; the two temperature chambers are composed 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 part of the polymer material to a completely molten state. The second temperature chamber is connected to the second nozzle, and is used to heat another part 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 centers of the nozzle outlets of the first nozzle and the second nozzle is 8 mm to 15 mm.

9. A 3D printed implant for skull defect repair, characterized in that: It is made by 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 0.05 mm and 0.15 mm.

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