Elastic modulus gradient pile core material, preparation method thereof and elastic modulus gradient pile core

Abstract

The invention discloses an elastic modulus gradient pile core material and a preparation method thereof, and an elastic modulus gradient pile core prepared from the elastic modulus gradient pile core material. The preparation method comprises the following steps: firstly, preparing a stake-core repair system with matched shape and size by clinically scanning the stake channel shape of a patient, and further preparing a stake-core system with bionic function gradient by simulating the elastic modulus gradient distribution of natural teeth and utilizing an additive manufacturing process. The stress distribution condition of the stake, the stake-tooth interface and the tooth part can be improved, and the service life of the stake-core repair diseased tooth can be prolonged.

Description

Technical Field

[0001] The present invention relates to a dental restoration material and a preparation method thereof, in particular to an elastic modulus gradient post-core material, a preparation method thereof, and an elastic modulus gradient post-core. Background Art

[0002] Tooth defects caused by caries, trauma, etc. are common and frequently-occurring diseases in oral clinical practice, with an incidence rate of 24% - 53%. Treatment methods for tooth defects include filling restoration, inlay restoration, crown restoration, etc. Teeth with larger defect areas need to be restored through a post-core crown ( Figure 1 a) to provide basic resistance and retention for the affected teeth.

[0003] As a natural gradient material, the elastic modulus of dentin in teeth gradually decreases from about 20 GPa to 16 GPa ( Figure 1 b). However, the existing post-core systems have a uniform elastic modulus, which does not fully match the characteristics of the elastic modulus gradient distribution of natural teeth, resulting in local stress concentration problems, which may lead to mechanical complications such as final post-core dislocation, post fracture, and even root fracture ( Figure 1 c). Therefore, constructing a post-core system that simulates the elastic modulus gradient change of natural teeth to obtain a uniform stress distribution and improve the restoration effect is an urgent problem for us to solve.

[0004] The existing post-core systems in clinical practice are roughly divided into fiber post-resin core, metal post-core, and ceramic post-core.

[0005] The fiber post-resin core consists of a resin matrix and fiber filaments to form a fiber post, and a core is built by stacking composite resin around the post to form a post-core system. The elastic modulus of the fiber post is about 25 - 57 GPa, which is relatively close to that of teeth (about 18 GPa). However, since the fiber post is prefabricated and does not fully match the root canal morphology of the patient's teeth, there are gaps and non-closure between the post and the root canal wall, making these non-closure parts the weak links of the entire restoration system and prone to mechanical complications such as debonding and post-core dislocation. Commonly used metal post-cores include titanium alloy post-core, gold alloy post-core, cobalt-chromium alloy post-core, nickel-chromium alloy post-core, etc. And the ceramic post-core is mainly zirconia post-core. The characteristics of these two post-core systems are high strength, but their elastic moduli are much higher than that of teeth, about 200 GPa and 150 GPa respectively. The problem of the mismatch between the elastic modulus and the teeth will lead to problems such as local stress concentration and uneven stress distribution after restoration, which are the main reasons for mechanical complications such as post-core dislocation, post fracture, and even root fracture, and are not conducive to the long-term prognosis of post-core restoration. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention provides a method for preparing an elastic modulus gradient post-core material. The filling ratio of the forming material is designed according to the elastic modulus distribution of the tooth to obtain a porosity gradient digital model, and the additive manufacturing process is used to form the porosity gradient digital model to obtain a preform of the post-core restoration system, and then a personalized and biomimetic elastic modulus gradient post-core material is prepared.

[0007] The technical solution of the present invention is as follows:

[0008] The first object of the present invention is to provide a method for preparing an elastic modulus gradient post-core material, comprising the following steps:

[0009] S1 Obtain the root canal morphology of the diseased tooth through digital scanning, and use digital CAD software to design a post-core restoration system with a corresponding shape and size match.

[0010] S2 Select the forming material of the post-core restoration system, design the filling ratio of the forming material according to the elastic modulus distribution of the tooth to obtain a porosity gradient digital model, and use the additive manufacturing process to form the porosity gradient digital model to obtain a preform of the post-core restoration system.

[0011] The preparation method of the present invention first prepares a post-core restoration system with a corresponding shape and size match by clinically scanning the root canal morphology of the patient, which can improve the non-tight fit problem of the fiber post-resin core, reduce the weak links of the restoration system, and improve the restoration effect of the post-core system. Furthermore, by simulating the elastic modulus gradient distribution of natural teeth, a biomimetic functional gradient post-core material is prepared by the additive manufacturing process, which can improve the stress distribution of the post, the post-tooth interface and the tooth part, and is beneficial to extending the service life of the post-core restoration.

[0012] The forming material of the post-core restoration system of the present invention can be metal or ceramic, such as titanium alloy, gold alloy, cobalt-chromium alloy, nickel-chromium alloy, zirconia, alumina, etc. In some embodiments, the forming material of the post-core restoration system is resin-infiltrated zirconia ceramic, and the filling ratio of zirconia ceramic in the porosity gradient digital model is 30-50 v / v%.

[0013] The additive manufacturing process in the preparation method of the present invention can be laser melting forming, stereolithography, fused deposition modeling, etc., and different manufacturing processes can be selected according to different forming materials. In some embodiments, inkjet direct writing 3D printing is used.

[0014] In some embodiments, the zirconia ceramic slurry used for inkjet direct writing 3D printing has a viscosity < 100 Pa·s when the shear rate > 10 s-1, and the yield stress of the slurry > 200 Pa.

[0015] In some of these embodiments, the zirconia ceramic slurry is formed by mixing 3 mol% yttrium-stabilized zirconia powder and Pluronic F127 hydrogel.

[0016] In some of these embodiments, the inkjet direct writing 3D printing parameters are as follows: the nozzle diameter is 340 μm; the pneumatic pressure is 230 KPa; the printing rate is 4.5 mm / s.

[0017] According to the different additive manufacturing processes selected, in some of these embodiments, it further includes a process of sintering the preform of the post and core restoration system.

[0018] In some of these embodiments, it further includes a process of silanization treatment on the preform of the post and core restoration system after sintering, including the following steps:

[0019] 1) Weigh γ-MPS, absolute ethanol, and pure water to prepare a silane coupling agent;

[0020] 2) Semi-infiltrate the preform of the post and core restoration system after sintering into the silane coupling agent and perform ultrasonic cleaning;

[0021] 3) Completely infiltrate the preform of the post and core restoration system after sintering into the silane coupling agent and perform ultrasonic cleaning;

[0022] 4) Take out the preform of the post and core restoration system after sintering and dry it.

[0023] The adhesion strength between the ceramic substrate and the resin can be enhanced through silanization treatment.

[0024] In some of these embodiments, it further includes a process of resin infiltration and thermal polymerization treatment on the preform of the post and core restoration system after silanization treatment, including the following steps:

[0025] 1) Weigh the resin monomers TEGDMA, UDMA, and the thermal initiator BPO in proportion and mix them evenly in the dark at room temperature to obtain a resin monomer mixture;

[0026] 2) Place the preform of the post and core restoration system after silanization treatment in a well plate, add the resin monomer mixture to semi-submerge the preform of the post and core restoration system, and perform ultrasonic treatment;

[0027] 3) Keep the well plate at 40 °C, evacuate and maintain for 30 min, then release the vacuum and maintain for 5 min. One evacuation and release cycle is completed, and 3 evacuation and release cycles are completed;

[0028] 4) Continue to add the resin monomer mixture to the well plate until the preform of the post and core restoration system is completely submerged, and complete the above 3 evacuation and release cycles;

[0029] 5) Take out the preform of the post and core restoration system and thermally polymerize it at 60 °C until the resin monomers are completely polymerized.

[0030] The second object of the present invention is to provide an elastic modulus gradient post-core material prepared by the preparation method of the above elastic modulus gradient post-core material.

[0031] The third object of the present invention is to provide an elastic modulus gradient post-core prepared from the above elastic modulus gradient post-core material.

[0032] By means of the above technical solution, the preparation method of the elastic modulus gradient post-core material of the present invention has the following advantages and beneficial technical effects:

[0033] 1) Personalization: By clinically scanning the root canal morphology of the patient, a post-core restoration system with a matching shape and size is prepared, which improves the non-tight fit problem existing in the fiber post-resin core, reduces the weak links of the restoration system, and improves the restoration effect of the post-core system.

[0034] 2) Digitalization: Advanced additive manufacturing technologies are adopted, such as the popular direct ink writing 3D printing technology. According to the appropriate filling ratio, a porosity gradient digital model is designed, and the precursor of the post-core restoration system is printed, which is the basis for preparing the elastic modulus gradient post-core material.

[0035] 3) Biomimicry: The post-core system constructed by the present invention simulates the elastic modulus gradient distribution of natural teeth. Finally, a biomimetic functional gradient post-core material is obtained, which can improve the stress distribution of the post, the post-tooth interface and the tooth part, and is beneficial to extending the service life of the post-core restoration. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the prior art, in which Figure 1 a is the post-core system of the prior art; Figure 1 b is a schematic diagram of the elastic modulus distribution of the tooth; Figure 1 c is the mechanical complication of the post-core crown restoration of the prior art;

[0037] Figure 2 It is a schematic diagram of the post-core model with a pore gradient;

[0038] Figure 3 It is a schematic flow chart of the preparation method of the elastic modulus gradient post-core material of the present invention;

[0039] Figure 4 It is a test chart of the rheological properties of the zirconia ceramic slurry in Example 1; Figure 4 a Relationship between the viscosity of the printing slurry and the shear rate; Figure 4 b Relationship between the storage modulus (G') and loss modulus (G") of the printing slurry and the shear stress;

[0040] Figure 5 Schematic diagram of the precursor samples of the zirconia ceramic post-core restoration system printed with different filling ratios;

[0041] Figure 6 For Figure 5 Light microscope image (5x) of the sample in

[0042] Figure 7 Schematic diagram of DIW line printing in Example 1 Figure 7 a is the line model; Figure 7 b is the physical image; Figure 7 c is the light microscope image;

[0043] Figure 8 For Figure 5 Schematic diagram of the state of the sample in after sintering

[0044] Figure 9 For Figure 8 Effect diagram of the sample in after resin infiltration and thermal polymerization treatment Specific implementation mode

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Unless otherwise specified, the filling ratio described in the present invention is the volume ratio.

[0047] The present invention provides a preparation method of an elastic modulus gradient post-core material, including the following steps:

[0048] S1 Obtain the root canal morphology of the diseased tooth through digital scanning, and use digital CAD software to design a post-core restoration system with a corresponding shape and size match.

[0049] First, by clinically scanning the root canal morphology of the patient and preparing a post-core restoration system with a corresponding shape and size match, the non-conformity problem existing in the fiber post-resin core can be improved, the weak links of the restoration system can be reduced, and the restoration effect of the post-core system can be improved.

[0050] S2 Select the forming material of the post-core restoration system, design the filling ratio of the forming material according to the elastic modulus distribution of the tooth, obtain a porosity gradient digital model (as Figure 2 shown), and use an additive manufacturing process to form the porosity gradient digital model to obtain a preform of the post-core restoration system.

[0051] Step 2 By combining the selected forming material, referring to Figure 1The elastic modulus distribution shown in b simulates the elastic modulus gradient distribution of natural teeth to obtain a porosity digital model. Then, an additive manufacturing process is used to prepare a bionic functional gradient post and core system, which can improve the stress distribution in the post, the post-tooth interface, and the tooth part, and is beneficial to extending the lifespan of post and core restoration. For example, a resin-infiltrated zirconia ceramic material is selected to make the post and core. According to Figure 1 the elastic modulus at the bottom of the root canal in b is 16.5 G, and combined with the preliminary sintering results of the material, the zirconia filling ratio is speculated to be 30%; the elastic modulus in the middle of the root canal is 18.0 G, and combined with the preliminary sintering results of the material, the zirconia filling ratio is speculated to be 40%. In addition, it can be adjusted according to the actual elastic modulus of the final product obtained after sintering, and the most suitable distribution is finally obtained through multiple adjustments.

[0052] The forming material of the post and core restoration system of the present invention can be metal or ceramic, such as titanium alloy, gold alloy, cobalt-chromium alloy, nickel-chromium alloy, zirconia, alumina, etc. In some embodiments, the forming material of the post and core restoration system is resin-infiltrated zirconia ceramic, and the zirconia ceramic filling ratio in the porosity gradient digital model is 30-50%.

[0053] The additive manufacturing process in the preparation method of the present invention can be selective laser melting, stereolithography, fused deposition modeling, etc. Different manufacturing processes can be selected according to different forming materials. For example, if a metal material is selected, selective laser melting can be used, or stereolithography can also be used, and then sintered after curing. In some embodiments, inkjet direct writing 3D printing is used, which is easier to control the trace output and ensure the structural accuracy.

[0054] The shape of the precursor of the post and core restoration system of the present invention can be close to the porosity gradient digital model, and then a conforming post and core structure can be obtained through simple cutting and grinding; it can also be designed as a square, etc. from the perspective of facilitating additive manufacturing printing, printed layer by layer, and then cut according to the porosity gradient digital model to obtain an elastic modulus gradient post and core.

[0055] The method of the present invention will be described below with specific embodiments. The following raw material components are all commercially available products.

[0056] Example 1

[0057] An elastic modulus gradient post and core material, referring to Figure 3 , is made by the following method, including the following steps:

[0058] S1 Obtain the morphology of the diseased tooth root canal through digital scanning, and use digital CAD software to design a post and core restoration system with a corresponding shape and size match;

[0059] S2 Select the forming material of the post-core restoration system, design the filling ratio of the forming material according to the tooth elastic modulus distribution model, obtain the digital model of the porosity gradient, and use the additive manufacturing process to form the digital model of the porosity gradient to obtain the precursor of the post-core restoration system.

[0060] Specifically, zirconia is used as the forming material, and the digital model of the porosity gradient of the ceramic bracket is designed according to the appropriate filling ratio. The zirconia filling ratio in the model is 30-50%, and the zirconia ceramic bracket precursor is obtained by printing with an inkjet direct writing 3D printing system (DIW). The steps are as follows:

[0061] 2.1 Preparation of zirconia ceramic slurry for DIW printing:

[0062] The zirconia ceramic slurry is formed by grinding and mixing 3mol% yttria-stabilized zirconia powder and Pluronic F127 hydrogel evenly.

[0063] The ratios of 3mol% yttria-stabilized zirconia and the DIW printing slurry are shown in Table 1 and Table 2 respectively as follows:

[0064] Table 1 Ratio of 3mol% yttria-stabilized zirconia (mass fraction)

[0065] Type 100 nm zirconia 20 nm zirconia 20 - 30 nm yttrium oxide Mass fraction 75.76 wt% 18.94 wt% 5.3 wt%

[0066] Table 2 Ratio of DIW printing slurry (mass fraction)

[0067] Type 3 mol% yttria-stabilized zirconia 25% w / v concentration of Pluronic F127 hydrogel Mass fraction 50 wt% 50 wt%

[0068] The preparation method of the zirconia ceramic slurry is as follows:

[0069] Place the nano-zirconia powder and nano-yttrium trioxide powder in an oven and dry at 60°C for 3 days, then sieve with a 200-mesh sieve to reduce powder agglomeration. Prepare supercooled water (4°C pure water), weigh Pluronic F127 hydrogel particles and dissolve them in supercooled water to prepare a 25% w / v concentration of Pluronic F127 hydrogel. Weigh 100nm zirconia, 20nm zirconia, and 20-30nm yttrium trioxide powder in proportion to obtain 3mol% yttria-stabilized zirconia powder (Table 1), and weigh 3mol% yttria-stabilized zirconia powder and hydrogel in a ratio of 50:50 (Table 2). Add the powder to the hydrogel in 6 portions and mix evenly to obtain the 3D printing ceramic slurry.

[0070] After each addition of the powder, mix it evenly using a planetary centrifuge at 2000 rpm for 3 minutes each time. After all the powder is added completely, mix it evenly 5 more times to obtain the final ceramic slurry.

[0071] The rheological properties of the obtained zirconia ceramic slurry were characterized using a shear rate and shear stress rheometer, and the results are shown in ( Figure 4 ). Figure 4 a shows the relationship between the slurry viscosity and the shear rate. The results show that as the shear rate increases, the slurry viscosity gradually decreases, showing shear thinning behavior, and at high shear rates - shear rate > 10 s -1 , the viscosity of the slurry is lower than 100 Pa·s.

[0072] Figure 4 b shows the relationship between the dynamic modulus (storage modulus G’ and loss modulus G”) of the slurry and the shear stress. The plateaus of the storage modulus curve and the loss modulus curve in the figure represent their storage modulus and loss modulus, and the shear stress corresponding to the intersection of the two curves is the yield stress. The yield stress of the slurry is greater than 200 Pa.

[0073] At the same time, the slurry all shows typical viscoelastic behavior, that is, when the shear stress is less than the yield stress, the storage modulus is greater than the loss modulus, and the slurry shows elastic behavior (similar to a solid); when the shear stress is greater than the yield stress, the storage modulus is less than the loss modulus, and the slurry shows viscous behavior (similar to a liquid). In this way, during the DIW printing and extrusion process, the slurry shows a liquid-like state and is easy to extrude. When it is stationary after extrusion, it shows a solid-like state and can maintain the shape and structure integrity of the extruded sample.

[0074] 2.2 DIW printing

[0075] First, the printing parameters were optimized. Printing was carried out using a nozzle with a diameter of 340 μm. The printing layer height, line width, filling ratio, printing speed, nozzle diameter, and bed size were set in the 3D printing software to obtain a line model( Figure 7 a). Grouped printing was carried out at printing pressures of 220 KPa, 230 KPa, and 240 KPa and printing speeds of 3 mm / s, 3.5 mm / s, 4 mm / s, 4.5 mm / s, 5 mm / s, 5.5 mm / s, 6 mm / s, and 6.5 mm / s respectively. The physical diagram is Figure 7 b, and the morphology and width of the printed lines were observed and measured under an optical microscope( Figure 7 c). Finally, the appropriate printing pressure and speed were determined to be 230 KPa and 4.5 mm / s. This pressure and speed were used for printing in subsequent experiments.

[0076] Then, according to the filling degree of the designed digital model, the pneumatic pressure of 230 KPa and the printing speed of 4.5 mm / s were set for printing. Figure 5 shows a schematic diagram of the precursor sample of the post-core restoration system printed with zirconia ceramics with different filling degrees, Figure 6 is Figure 5 the light microscope image of the sample in.

[0077] S3 sintering produced a zirconia ceramic scaffold precursor with a porosity gradient.

[0078] After the ceramic bracket precursor is printed, it is placed in a petri dish and covered to air dry overnight, and then sintered. The sintering process is: room temperature rises to 700°C, maintained for 1 hour, then 700°C rises to 1300°C, maintained for 2 hours, and finally cooled to room temperature with the furnace. The rising and falling rates are 3°C / min. Finally, a porous zirconia bracket is obtained, and the obtained ceramic bracket is immersed in pure water for ultrasonic cleaning for 1 hour. Figure 8 Shows Figure 5 The state of the sample after sintering.

[0079] S4 silanization treatment.

[0080] (1) Place the sintered ceramic bracket in pure water for ultrasonic cleaning for 30 minutes to 1 hour.

[0081] (2) Weigh γ-MPS, anhydrous ethanol, and pure water, and mix them under magnetic stirring for 1 h at room temperature to obtain a silane coupling agent, as shown in Table 3 below.

[0082] Table 3 Ratio of silane coupling agent (mass fraction)

[0083] Type γ-MPS Absolute ethanol Pure water Mass / volume 6g 75ml 25ml

[0084] (3) The ceramic stent was semi-immersed in the silane coupling agent and ultrasonicated for 30 minutes.

[0085] (4) The ceramic stent was completely immersed in the silane coupling agent and ultrasonicated for 3 h.

[0086] (5) Take out the ceramic bracket and dry it at 80°C for 3 h.

[0087] S5, resin impregnation and thermal polymerization.

[0088] Table 4 Ratio of resin impregnation and thermal polymerization process (mass fraction)

[0089] Type TEGDMA UDMA BPO Mass fraction 79.6 wt% 19.9 wt% 0.5 wt%

[0090] (1) According to the proportions in Table 4, weigh the resin monomers TEGDMA, UDMA and thermal initiator BPO, and mix them under magnetic stirring for 3 h at room temperature in the dark to obtain a resin monomer mixed solution.

[0091] (2) The silanized and dried ceramic stent is placed in a well plate, and the resin monomer mixture is added to half-immerse the stent, and ultrasonication is performed for 30 minutes.

[0092] (3) Place the orifice plate in a vacuum drying oven at 40°C, evacuate and hold for 30 minutes, then release the vacuum and hold for 5 minutes. The evacuation and release of the vacuum is one cycle, and a total of three evacuation and release cycles are completed.

[0093] (4) Continue to add the resin monomer mixture into the orifice plate until the ceramic bracket is completely immersed, and then complete the above 3 vacuum pumping cycles.

[0094] (5) Take out the fully infiltrated ceramic bracket, place it on the tin foil, and put it into the oven for thermal polymerization at 60 °C for 3 d until the resin monomer is completely polymerized, thus obtaining the elastic modulus gradient post-core material PIZC. Figure 9 Shows Figure 8 The effect diagram after sample resin infiltration and thermal polymerization treatment in

[0095] After testing, for the bracket obtained in the example, when the porosity is 60 - 50% (i.e., the resin filling rate is 60 - 50%), the elastic modulus is about: 10 GPa; when the porosity is 50 - 40% (i.e., the resin filling rate is 50 - 40%), the elastic modulus can reach: 15 - 10 GPa; when the porosity is 40 - 30% (i.e., the resin filling rate is 40 - 30%), the elastic modulus can reach: 20 - 15 GPa. Therefore, it can be seen that the method of the present invention can simulate the elastic modulus gradient distribution of natural teeth according to the adjustment of the porosity, and finally obtain the elastic modulus gradient post-core material.

[0096] In practical applications, it also includes performing CAD / CAM cutting on the obtained elastic modulus gradient post-core material to obtain an elastic modulus gradient post-core, and then applying it to tooth restoration. The following is described in combination with Examples 2 - 4.

[0097] Example 2

[0098] For premolars with 3 - 4 wall defects, use the elastic modulus gradient post-core material PIZC and all-ceramic crown of Example 1 to perform restoration treatment on them. The steps include:

[0099] 1. Preparation stage: Perform tooth preparation according to the requirements of full crown tooth preparation, remove the original temporary sealing material in the tooth body, remove the gutta-percha and filling paste in the upper part of the root canal by using a slow speed handpiece and a P drill, and further shape the root canal to obtain a nearly conical channel with a taper as the post canal, and retain 4 - 6 mm of apical seal in the lower part of the root canal to prevent bacterial infection in the root canal.

[0100] 2. Refer to the method of Example 1 to obtain the PIZC post-core material with an elastic modulus gradient.

[0101] Use silicone rubber light body and heavy body to make the negative mold of the post channel. Subsequently, use digital intraoral scanning technology to obtain the digital model of the negative mold, and scan the intraoral dentition and occlusion relationship to obtain a digital impression. Design the post-core morphology according to the post-channel negative mold and tooth digital model obtained by intraoral scanning. The bottom plane of the core is at a 90° angle to the post axis and coincides with the plane of the defective tooth body. At the same time, the core edge line coincides with the tooth body edge line. The core morphology has a polymerization degree of less than 10 degrees to ensure sufficient retention force of the full crown.

[0102] Referring to Example 1, after obtaining a porosity-gradient zirconia scaffold by 3D printing, sinter the ceramic scaffold by a two-step method. Subsequently, infiltrate the scaffold with resin monomer and thermally cure the resin to obtain a PIZC post-core material with a gradient of elastic modulus. The material size is 17×14×12 mm, the three-point bending strength of the material is 200 MPa, the elastic modulus is 10 - 14 - 16 GPa, and it has the characteristics of a gradient of elastic modulus.

[0103] 3. Perform CAD / CAM cutting on the PIZC material according to the digital post-core model to obtain a post-core with a gradient of elastic modulus.

[0104] 4. Sandblast the bonding surface of the post-core to improve its bonding performance. Use 3M ESPE RelyXTM Unicem self-adhesive resin cement to cement the PIZC post-core with a gradient of elastic modulus. The post is firmly combined with the pulp cavity wall, and the core is fused with the remaining tooth tissue into a tooth preparation body with a retention form and meeting the requirements of full crown restoration.

[0105] Example 3

[0106] For a molar with a four-wall defect and still having a 1.5-mm dentin shoulder collar, use the PIZC post-core of the elastic modulus gradient pile-core material in Example 1 and a full ceramic crown to perform restoration treatment on it. The steps include:

[0107] 1. Preparation stage: Perform tooth preparation according to the requirements of full crown tooth preparation. Remove the original temporary filling material in the tooth body. Use a slow-speed handpiece and a P-drill to remove the gutta-percha and filling paste in the upper part of the root canal, and further shape the root canal to obtain a nearly conical channel with a taper as the post channel, and retain a 4 - 6-mm apical seal in the lower part of the root canal to prevent bacterial infection in the root canal.

[0108] 2. Refer to the method in Example 1 to obtain a PIZC post-core material with a gradient of elastic modulus.

[0109] Use silicone rubber light body and heavy body to make the negative mold of the post canal. Subsequently, use digital intraoral scanning technology to obtain the digital model of the negative mold, and scan the intraoral dentition and occlusion relationship to obtain a digital impression. Design the post-core morphology according to the post canal negative mold and dental digital model obtained by intraoral scanning. The core bottom plane forms a 90° angle with the post axis and coincides with the plane of the defective tooth body. At the same time, the core edge line coincides with the tooth body edge line. The core morphology has a polymerization degree of less than 10 degrees to ensure sufficient retention force of the full crown.

[0110] Referring to Example 1, after obtaining a porous gradient zirconia scaffold by 3D printing, sinter the ceramic scaffold by a two-step method. Subsequently, infiltrate the scaffold with resin monomer and perform thermal curing of the resin to finally obtain a PIZC post-core material with a gradient elastic modulus. The material size is 17×14×12 mm, the three-point bending strength of the material is 200 MPa, and the elastic modulus is 10 - 14 - 16 GPa, with the characteristics of a gradient elastic modulus.

[0111] 3. Perform CAD / CAM cutting on the PIZC material according to the digital post-core model to obtain a post-core with a gradient elastic modulus.

[0112] 4. Sandblast the bonding surface of the post-core to improve its bonding performance. Use 3M ESPE RelyXTM Unicem self-adhesive resin cement to cement the post-core with a gradient elastic modulus of PIZC. The post firmly combines with the pulp cavity wall, and the core fuses with the remaining tooth tissue into a tooth preparation body with a retention form that meets the requirements of full crown restoration.

[0113] Example 4

[0114] For maxillary central incisors with 4-wall defects and lacking a dentin shoulder collar subgingivally, use the PIZC post-core material with a gradient elastic modulus and a full ceramic crown in Example 1 for restoration treatment.

[0115] 1. Preparation stage: According to the distance between the defect location and the alveolar crest, design a crown lengthening surgical plan and perform the surgery to obtain a 1.5-mm dentin shoulder collar. Observe the gingival recovery after the surgery. After the gingival position and morphology are stable, perform post-core crown restoration. The restoration process first prepares the tooth body according to the requirements of full crown tooth preparation, removes the original temporary filling material in the tooth body, removes the gutta-percha and filling paste in the upper segment of the root canal by using a slow handpiece and P drill, and further shapes the root canal to obtain a nearly conical channel with a taper as the post canal, and retain 4 - 6 mm of apical seal in the lower segment of the root canal to prevent bacterial infection in the root canal.

[0116] 2. Refer to the method in Example 1 to obtain a PIZC post-core material with a gradient elastic modulus.

[0117] The post channel was negatively molded by silicone rubber light and heavy bodies, and then the digital model of the negative mold was obtained by digital mouth scanning technology, and the dentition and occlusal relationship in the mouth were scanned to obtain a digital impression. The post and core morphology was designed according to the post channel negative mold and the digital model of the tooth obtained by mouth scanning. The angle between the core bottom plane and the post axis was 90° and coincided with the plane of the defective tooth, and the core edge line coincided with the tooth edge line. The core morphology had a polymerization degree of less than 10 degrees to ensure that the full crown had sufficient retention. After the porosity gradient zirconia bracket was obtained by 3D printing, the ceramic bracket was sintered by a two-step method, and then the bracket was infiltrated with resin monomer and the resin was thermally cured. Finally, the PIZC post and core material with an elastic modulus gradient was obtained. The material size was 17×14×12mm, the three-point bending strength of the material was 200MPa, and the elastic modulus was 10-14-16GPa, which had an elastic modulus gradient characteristic.

[0118] 3. According to the digital post and core model, CAD / CAM cutting is performed on the PIZC material to obtain the elastic modulus gradient post and core.

[0119] 4. Sandblast the post-core bonding surface to improve its bonding performance. Use 3M ESPE RelyXTM Unicem self-adhesive resin cement to bond the elastic modulus gradient PIZC post-core. The post is firmly bonded to the pulp cavity wall, and the core and the remaining tooth tissue are fused into a tooth preparation with a retention morphology that meets the requirements of full crown restoration.

[0120] In summary, the preparation method of the embodiment of the present invention adopts the popular ink direct writing 3D printing technology, designs a porosity gradient digital model according to an appropriate filling ratio, prints a zirconia ceramic bracket precursor through an ink direct writing printing system, and then sinters to obtain a zirconia ceramic bracket with a porosity gradient, thereby preparing a personalized and bionic elastic modulus gradient post and core material PIZC. Furthermore, the PIZC material is cut by CAD / CAM to obtain an elastic modulus gradient post and core, which can be used for tooth restoration.

[0121] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of an elastic modulus gradient post-core material, characterized in that, It includes the following steps: S1 Obtain the root canal morphology of the diseased tooth through digital scanning, and use digital CAD software to design a post-core restoration system with a corresponding shape and size match. S2 Select the forming material of the post-core restoration system, design the filling ratio of the forming material according to the elastic modulus distribution of the tooth, obtain a porosity gradient digital model, and use additive manufacturing technology to form the porosity gradient digital model to obtain a preform of the post-core restoration system.

2. The preparation method of the elastic modulus gradient post-core material according to claim 1, characterized in that, The forming material of the post-core restoration system is resin-infiltrated zirconia ceramic, and the filling ratio of zirconia ceramic in the porosity gradient digital model is 30-50%.

3. The preparation method of the elastic modulus gradient post-core material according to claim 2, characterized in that, The additive manufacturing technology is inkjet direct writing 3D printing.

4. The preparation method of the elastic modulus gradient post-core material according to claim 3, characterized in that, The zirconia ceramic slurry for direct ink writing 3D printing has a viscosity < 100 Pa·s when the shear rate > 10 s -1 , and the yield stress of the slurry > 200 Pa.

5. The preparation method of the elastic modulus gradient post-core material according to claim 4, characterized in that, The inkjet direct writing 3D printing parameters are: nozzle diameter is 340μm; pneumatic pressure is 230KPa; printing speed is 4.5mm / s.

6. The preparation method of the elastic modulus gradient post-core material according to claim 2, characterized in that, It also includes the process of sintering the preform of the post-core restoration system.

7. The preparation method of the elastic modulus gradient post-core material according to claim 6, characterized in that, It also includes the process of silanization treatment on the preform of the post-core restoration system after sintering, including the following steps: 1) Weigh γ-MPS, anhydrous ethanol, and pure water to prepare a silane coupling agent. 2) Semi-immerse the preform of the post-core restoration system after sintering into the silane coupling agent and perform ultrasonic treatment. 3) Completely immerse the preform of the post-core restoration system after sintering into the silane coupling agent and perform ultrasonic treatment. 4) Take out the preform of the post-core restoration system after sintering and dry it.

8. The preparation method of the elastic modulus gradient post-core material according to claim 7, characterized in that, It also includes the process of resin infiltration and thermal polymerization treatment on the preform of the post-core restoration system after silanization treatment, including the following steps: 1) Weigh the resin monomers TEGDMA, UDMA, and the thermal initiator BPO in proportion, and mix them evenly in the dark at room temperature to obtain a resin monomer mixture. 2) Place the preform of the post-core restoration system after silanization treatment in a well plate, add the resin monomer mixture to semi-submerge the preform of the post-core restoration system, and perform ultrasonic treatment. 3) Keep the well plate at 40°C, evacuate and maintain for 30 minutes, then release the vacuum and maintain for 5 minutes. One evacuation and release cycle is completed, and 3 evacuation and release cycles are completed. 4) Continue to add the resin monomer mixture to the well plate until the preform of the post-core restoration system is completely submerged, and complete the above 3 evacuation and release cycles. 5) Take out the preform of the post-core restoration system and thermally polymerize it at 60°C until the resin monomer is completely polymerized.

9. An elastic modulus gradient post-core material prepared by the preparation method of the elastic modulus gradient post-core material according to any one of claims 1-8.

10. An elastic modulus gradient post-core, characterized in that, It is prepared from the elastic modulus gradient post-core material described in claim 9.

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