Silicon nitride dental implant assembly and preparation process thereof

Abstract

The invention discloses a silicon nitride dental implant assembly and a preparation process thereof, and belongs to the technical field of oral medicine. The silicon nitride dental implant assembly comprises a silicon nitride dental crown and a one-section silicon nitride implant which can be fixed in a bonding manner, the silicon nitride dental crown comprises a silicon nitride crown body and a facing layer, and is obtained by applying facing layer slurry on a silicon nitride crown body prefabricated part and then sintering the silicon nitride crown body prefabricated part, the silicon nitride implant and the silicon nitride crown body are made of the same material and are both prepared by sintering injection-molded prefabricated parts. The dental implant can meet the requirement of long-term service of the dental implant in an oral environment.

Description

Technical Field

[0001] The present invention relates to a silicon nitride dental implant assembly and a preparation process thereof, belonging to the technical field of stomatology. Background Art

[0002] Dental implants, as an important technology in modern stomatology, have become one of the main means to solve tooth loss problems. Its core principle is to accurately implant an artificial tooth root into the upper / lower jawbone of the toothless area. After a period of osseointegration process, the artificial tooth root forms a tight connection with the surrounding bone tissue. Then, a abutment is installed through connectors such as screws to firmly support the crown part above. With the help of complete imaging data and advanced digital processing technology, a highly personalized crown can be obtained, which together with the abutment and the artificial tooth root constitutes a complete dental implant. This technology not only restores the chewing function of teeth, but also greatly improves the aesthetics and vocal function, becoming the preferred treatment option for many patients.

[0003] At present, the materials of artificial tooth roots and abutments on the domestic market are pure titanium or titanium alloy, and the materials of the crowns on the abutments are mostly zirconia ceramics. However, zirconia ceramic artificial tooth roots have also appeared on the international market. However, the existing implants still have the following defects:

[0004] ① Lack of antibacterial performance; The oral cavity is a complex microbial environment. After the implant is implanted, it is easily invaded by bacteria, leading to peri-implantitis, and then causing the absorption of the bone tissue around the implant, resulting in complications such as hindering osseointegration, affecting the surgical effect and the lifespan of the implant. Although titanium alloy has good biocompatibility, titanium alloy itself does not have antibacterial properties, and its surface bioinertia causes bacteria to relatively easily attach and form a plaque biofilm, thus greatly increasing the risk and degree of infection and the difficulty of antibacterial. Although the surface of titanium alloy implants can be modified to enhance their antibacterial effect, the effects of these treatments are not ideal and not lasting;

[0005] ② Poor osseointegration performance; The bonding strength between the implant and the bone tissue directly affects the service life and success rate of the implant. Whether the implant can form stable osseointegration is the key to its success. The existing implants have a long healing time, affecting the recovery speed of patients.

[0006] The latest research shows that non-oxide ceramics - silicon nitride ceramics, in addition to having the advantages of general ceramics, also have the characteristics of biosecurity and chemical stability. For dental implants, silicon nitride ceramics, known as the "all-round champion in the ceramic world", are a potential, excellent, and upgraded raw material selection direction. However, there are still many problems to be solved in the design and manufacture of dental implants made of silicon nitride. The most typical problem is how to achieve the optimal balance among the material formula of silicon nitride ceramics, the processing and forming process, the sintering preparation process, and the comprehensive performance of the product in the field of dental implants. For example, as the final product, the implant needs to be implanted into the jawbone, so the product needs to have a special thread that is self-tapping and does not damage the bone too much. This special thread needs to be processed and customized. Silicon nitride ceramics, as such ceramics, have a much higher hardness than ordinary metal materials and belong to the precision processing of superhard materials. The difficulty and cost of this kind of processing are very high. Therefore, other processing and forming technologies must be considered. At the same time, it is very important that the impact of a certain specific processing and forming method on the performance of the final product must be minimized. As for the ceramics that need to be sintered after processing and forming, it also involves its formula. In order to improve the sintering preparation process, corresponding additives need to be added. Since the final product is a medical device that needs to be implanted into the human body, the additives cannot be arbitrarily selected and need to meet a series of requirements such as safety and effectiveness. Each link is interconnected, and pulling one hair moves the whole body. To sum up, for dental implants, the combination, optimization, and balance of the customized silicon nitride ceramic material formula, the special ceramic preparation process, and the targeted dental implant product design are the target solutions. Summary of the Invention

[0007] In view of the above deficiencies in the prior art, the present invention provides a silicon nitride dental implant assembly and its preparation process, which can meet the requirements of long-term service of dental implants in the oral environment.

[0008] In a first aspect, the present invention relates to a silicon nitride dental implant assembly, comprising a silicon nitride dental crown and a one-piece silicon nitride implant, which can be adhesively fixed.

[0009] The silicon nitride dental crown includes a silicon nitride crown body and a decorative layer, which is obtained by sintering after applying the decorative layer slurry on the silicon nitride crown body preform.

[0010] The silicon nitride implant and the silicon nitride crown body are made of the same material, both of which are obtained by sintering the injection-molded preform. By weight ratio, the preform includes: 80% - 88% silicon nitride powder, 5% - 10% sintering aid, 3% - 6% binder, 2% - 5% dispersant, and 1% - 3% lubricant, totaling 100%.

[0011] The formula of the finishing layer slurry includes, by weight: 30 to 40 parts by weight of kaolin, 20 to 30 parts by weight of palygorskite, 12 to 16 parts by weight of quartz, 10 to 20 parts by weight of potassium feldspar, 5 to 9 parts by weight of calcite, 4 to 6 parts by weight of titanium dioxide, 2 to 5 parts by weight of yttrium oxide, 2 to 5 parts by weight of zirconium oxide and 2 to 5 parts by weight of silicon nitride, totaling 100 parts by weight; in addition, it also includes 170 to 220 parts by weight of water.

[0012] The sintering aid includes at least one of zirconium oxide, ytterbium oxide, magnesium oxide and boron nitride;

[0013] The binder is at least one of polyethylene, polypropylene, polyoxymethylene, polylactic acid, paraffin, beeswax, polycarbonate, modified cellulose, polystyrene, polyhydroxyalkanoate, polyethylene glycol, and phenolic resin;

[0014] The dispersant is at least one of oleic acid, phosphate, ammonium polyacrylate, lecithin, triethyl phosphate, polyacrylic acid, castor oil, polyvinyl pyrrolidone, C12 alkyl polyglycoside quaternary ammonium salt, and tetramethylammonium hydroxide;

[0015] The lubricant is at least one of zinc stearate, polyethylene wax, ethylene bis stearamide, polytetrafluoroethylene, silicone oil, beeswax and lauric acid.

[0016] The second aspect of the present invention relates to a process for preparing a silicon nitride dental implant assembly, comprising the following steps:

[0017] The steps of preparing the feed material are as follows: weighing silicon nitride powder and sintering aid according to the above weight proportion, adding solvent and mixing and ball milling; spray granulation to obtain granulated powder; mixing the granulated powder, binder, dispersant and lubricant according to the above weight proportion to obtain the feed material; preferably, the average particle size of the granulated powder does not exceed 0.9 μm;

[0018] Preparation steps of the finishing layer slurry: weigh kaolin, palygorskite, quartz, potassium feldspar, calcite, titanium dioxide, yttrium oxide, zirconium oxide and silicon nitride according to weight ratio, add solvent, mix and ball mill according to the ratio of raw material: grinding ball: solvent mass ratio = 1: (1.3-1.5): (1.7-2.2) to obtain the finishing layer slurry; preferably, the ball milling speed is 200-400 r / min, and the ball milling time is 24-48h;

[0019] Injection molding step: Inject the prepared feedstock in a mold. The injection pressure is 80 - 90 MPa, the injection temperature is 160 - 170 °C, the injection speed is 10 - 30 mm / s, and the mold temperature is 80 - 100 °C. After injection, a melt is obtained, and then it is pressure-held for 2 - 8 min to ensure the density and shape stability of the green body obtained by the cooling and solidification of the melt. After the pressure-holding ends, the melt is gradually cooled to room temperature to solidify and form a silicon nitride implant green body and a silicon nitride crown green body with a preset shape.

[0020] Laser etching step: Laser-etch the part of the silicon nitride implant green body corresponding to the root of the finished product. Preferably, the scanning pitch of the laser etching is 0.5 - 1.5 mm, which is convenient for etching operations and beneficial to the bone integration of the finished product.

[0021] Thermal debinding step: Place the laser-etched silicon nitride implant green body and silicon nitride crown green body in a flowing inert gas atmosphere for debinding and pre-sintering. During the process, the heating rate is 10 - 25 °C / min, the debinding and sintering temperature is 400 - 800 °C, and the sintering time is 2 - 6 h. The flowing inert gas atmosphere means that after the green body is placed in the debinding furnace, the furnace is evacuated and then an inert gas is introduced. The operation of evacuating first and then introducing the inert gas is repeated 3 - 5 times to ensure that there is no oxygen residue in the furnace, and then the inert gas is continuously introduced at a certain speed.

[0022] Surface pretreatment step: Immerse the silicon nitride crown green body after the thermal debinding step in the surface layer slurry until fully wetted, then take it out and dry it naturally.

[0023] Sintering step: Place the silicon nitride implant green body after the thermal debinding step and the silicon nitride crown green body infiltrated with the surface layer slurry in a flowing inert gas atmosphere for three-stage sintering. The first stage is atmospheric pressure sintering, heating up to the sintering temperature of 1000 - 1200 °C, and the sintering time is 1 - 2 h. The second stage is atmospheric pressure sintering, heating up to the sintering temperature of 1400 - 1600 °C, and the sintering time is 1 - 2 h. The third stage is pressure sintering, the inert gas pressure is increased from atmospheric pressure to 2 - 10 MPa, and continue to heat up to the sintering temperature of 1600 - 1900 °C, and the sintering time is 2 - 6 h to obtain a dental implant assembly composed of a silicon nitride implant and a silicon nitride crown.

[0024] For some specific embodiments, in the feedstock preparation step:

[0025] Preferably, the ball milling time is 12 - 36 h, and the rotation speed is 120 - 360 r / min.

[0026] Preferably, spray granulation is completed using a pressure spray granulator. The inlet temperature of the dryer is set at 40 - 80°C, the outlet temperature is set at 20 - 40°C, the pressure difference of the cyclone separator is set at 200 - 240 Pa, the inner diameter and wall thickness of the central hole of the nozzle are both 0.16 mm, the pressure is set at 2.0 - 2.8 MPa, the spray angle range of the ceramic spiral nozzle is set at 60° - 120°, and the feeding rate is set at 10 - 100 mL / min;

[0027] Preferably, in the feeding preparation step, the feed is prepared by adding granulation powder, binder, dispersant, and lubricant into a vacuum mixer and mixing at a mixing temperature of 80 - 120°C for 2 - 8 hours.

[0028] The structure of the above one-piece silicon nitride implant includes a abutment, a neck, and a root;

[0029] The implant is provided with a first thread, a second thread, and a third thread in sequence from the root to the neck. The first thread and the second thread are provided on the root, and the third thread is provided on the neck;

[0030] The first thread region is provided with 2 - 4 cutting grooves.

[0031] For some specific embodiments, the first thread is a conical external thread, and the second thread and the third thread are cylindrical external threads.

[0032] For some specific embodiments, the root is provided with a pore layer on the surface, and the porosity range of the pore layer is 35% - 75%.

[0033] Preferably, the angle of the cone in the conical external thread region is 10° - 15°; more preferably, the included angle between the cutting groove and the axis of the implant is half of the cone angle, and the width of the cutting groove is 1 - 2 mm, aiming to reduce the implantation pressure, improve the self-tapping property and bone debris accumulation, and improve the implantation efficiency.

[0034] Preferably, the thread profile of the first thread is a serrated thread, the radius of the tooth top arc is 0.1 - 0.2 mm, the radius of the tooth bottom transition arc is 0.4 - 0.5 mm, the pitch is 0.6 - 1.0 mm, the thread depth is 0.6 - 1.0 mm, and the thread length is 0.35L - 0.4L, where L is the total length of the root and the neck;

[0035] Preferably, the thread profile of the second thread is a trapezoidal thread, the width of the tooth top is 0.2 - 0.4 mm, the radius of the tooth bottom transition arc is 0.4 - 0.5 mm, the pitch is 0.6 - 1.0 mm, the thread depth is 0.2 - 1.0 mm, and the thread length is 0.4L - 0.45L, where L is the total length of the root and the neck;

[0036] Preferably, the thread profile of the third thread is a triangular thread, the arc radius of the thread crest is 0.1 - 0.2 mm, the transition arc radius of the thread root is 0.4 - 0.5 mm, the pitch is 0.2 - 0.4 mm, the thread depth is 0.02 - 0.5 mm, and the thread length is 0.15L - 0.25L, where L is the total length of the root and the neck.

[0037] For some specific embodiments, the axial length of the abutment is 3 - 6 mm.

[0038] Compared with the prior art, the present invention has the following technical effects:

[0039] 1) First, the silicon nitride dental implant adopts a combination form of a dental crown and a one-piece implant structure. The two can be bonded together with good integrity. In particular, the implant structure with an integrated abutment and root avoids the problem that the processability and mechanical properties of the material cannot be both satisfied during the processing of silicon nitride implants. Then, a silicon nitride dental crown of the same material is provided corresponding to the silicon nitride implant, with good matching. Finally, a high-strength and wear-resistant silicate veneer layer with a color close to white is formed on the silicon nitride dental crown, which is beautiful in color. It can not only meet the requirements for long-term service of dental implants in the oral environment, but also solve the problem that the existing gray-series silicon nitride orthopedic implant materials cannot be used to manufacture dental implants due to color problems.

[0040] 2) The green body prepared by the injection molding process has strong bonding force between materials, which is beneficial to maintaining a dense structure of the material during the sintering process, and the obtained finished product can better maintain the excellent mechanical properties of the silicon nitride material.

[0041] 3) Holes are preformed at the root on the silicon nitride implant green body by laser etching, and then uniformly porous are formed by ablation during the first and second stage sintering processes, and finally densified by gas pressure sintering to form a silicon nitride implant with a high porosity on the root surface layer gradually densifying to the root core, ensuring that silicon nitride can induce and accelerate osteogenesis and regeneration in the organism, promote the bone integration process, and improve the service life of the implant.

[0042] 4) Part of the high-strength and wear-resistant silicate veneer layer is fully combined with the silicon nitride crown body through pores, and the added silicon nitride further improves the bonding performance between the veneer layer and the silicon nitride crown body. Furthermore, the mechanical properties of the veneer layer are improved by toughening with the added silicon nitride, yttrium oxide and zirconia. Also, the overall color of the veneer layer is adjusted by the good covering power of titanium dioxide to ensure that the color of the dental crown is close to that of natural teeth, so that it can be accepted by the market.

[0043] 5) Compared with materials such as titanium alloy and zirconia, silicon nitride material has excellent antibacterial properties, bone integration ability and mechanical properties; compared with implants made by 3D printing and stereolithography processes, the implant integrally formed by ceramic injection molding process is more dense in structure, ensuring excellent mechanical properties of the final implant; the abutment, neck and root are integrally formed, avoiding secondary processing; in particular, problems such as the inability to form the inner hole connection structure and the connection strength being less than the strength of the silicon nitride material itself caused by the independent manufacturing of the abutment and other parts of the implant. Description of the Drawings

[0044] Figure 1 It is a schematic diagram of the overall structure of the one-piece silicon nitride implant in Examples 1 to 4. Detailed Description of the Invention

[0045] The present invention will be described in detail below in conjunction with the specific embodiments. The experimental methods without specific conditions noted in the examples are carried out according to the conventional methods and conditions.

[0046] The one-piece implants involved in the examples and comparative examples of the present invention need to be subjected to the following performance tests.

[0047] The detection of density is carried out in accordance with "GB / T 25995-2010 Test methods for density and apparent porosity of fine ceramics".

[0048] The detection of hardness is carried out in accordance with "GB / T 16534-2009 Test method for room temperature hardness of fine ceramics".

[0049] The detection of compressive strength is carried out in accordance with "GB / T 8489-2006 Test method for compressive strength of fine ceramics".

[0050] The detection of fracture toughness is carried out in accordance with "ISO 14627:2012 Fine ceramics (advanced ceramics, advanced technical ceramics) - Resistance of silicon nitride materials for rolling bearing balls to fracture at room temperature by the indentation fracture (IF) method".

[0051] Regarding the antibacterial rate, its detection method and operation steps are as follows:

[0052] Inoculate the species of Porphyromonas gingivalis, Staphylococcus aureus and Escherichia coli on the slant of nutrient agar medium. After culturing at 37 ± 1°C for 24 h, store them at 0 - 5°C (not exceeding 1 month) as the slant-preserved bacteria;

[0053] Transfer the slant-preserved bacteria onto the plate of nutrient agar medium and culture at 37 ± 1°C for 24 h, transferring once a day for no more than 2 weeks. Fresh bacterial cultures (transferred within 24 h) after continuous transfer twice should be used during the test;

[0054] Use an inoculation loop to pick up a small amount (scrape 1 - 2 loops) of fresh bacteria from the medium, add it to the culture solution, and successively make 10-fold serial dilution solutions. Count with a hemocytometer, and select the dilution solution with a bacterial concentration of 10.0×10 5 cfu / ml as the bacterial solution for experimental detection;

[0055] Prepare 15 sterilized Petri dishes with a diameter of φ90 mm. Lay 5 - 6 sterile filter papers with a diameter of φ90 mm at the bottom of the Petri dishes, and pour an appropriate amount of sterile purified water to make the filter papers fully absorb water. Press the filter papers with sterile forceps until no large amount of water seeps out;

[0056] Take 15 sterile filter membranes with a size of φ0.24 μm × 50 mm and cover them on the sterile filter papers in each Petri dish, spreading them flat. Take 0.2 ml of the experimental bacterial solution and drop it on the sterile filter membrane with a size of φ0.24 μm × 50 mm;

[0057] Use sterile forceps to pick up the negative control sample (A), blank control sample (B), and test sample (C). Prepare 5 parallels for each sample and cover them on the sterile filter membrane with a size of φ0.24 μm × 50 mm to make the bacterial solution contact the samples evenly, and place them at 37 ± 1°C for 24 h;

[0058] Take out the samples cultured for 24 h, add 20 ml of eluent to each respectively, and wash samples A, B, C and the covering membranes repeatedly, shaking well. Use a sterile pipette tip to aspirate 1 ml of the eluent stock solution and transfer it into a sterile Petri dish, then pour about 15 ml of nutrient agar medium into the Petri dish and rotate the Petri dish to mix evenly. Repeat the plate spreading operation twice to obtain 2 Petri dishes of eluent stock solution. Take another 1 ml of the eluent stock solution and slowly pour it along the tube wall into a test tube containing 9 ml of sterile normal saline. Do not touch the tip of the pipette tip to the dilution solution in the tube, shake the test tube to mix evenly to make a 1:10 eluent dilution;

[0059] Transfer 1 mL of 1:10 elution diluent into a sterile Petri dish. Pour about 15 mL of nutrient agar medium into the Petri dish and rotate the Petri dish to mix evenly. Repeat the plate pouring operation 2 times to obtain 2 Petri dishes of 1:10 elution diluent. Take 1 mL of 1:10 elution diluent and slowly pour it along the tube wall into a test tube containing 9 mL of sterilized normal saline. The tip of the pipette does not touch the diluent in the tube. Shake the test tube to mix evenly to make a 1:100 elution diluent;

[0060] Transfer 1 mL of 1:100 elution diluent into a sterile Petri dish. Pour about 15 mL of nutrient agar medium into the Petri dish and rotate the Petri dish to mix evenly. Repeat the plate pouring operation 2 times to obtain 2 Petri dishes of 1:100 elution diluent. Take 1 mL of 1:100 elution diluent and slowly pour it along the tube wall into a test tube containing 9 mL of sterilized normal saline. The tip of the pipette does not touch the diluent in the tube. Shake the test tube to mix evenly to make a 1:1000 elution diluent;

[0061] Transfer 1 mL of 1:1000 elution diluent into a sterile Petri dish. Pour about 15 mL of nutrient agar medium into the Petri dish and rotate the Petri dish to mix evenly. Repeat the plate pouring operation 2 times to obtain 2 Petri dishes of 1:1000 elution diluent;

[0062] When performing plate colony counting, it can be observed with the naked eye and checked with a magnifying glass if necessary to prevent omission. After recording the colony counts of each plate, calculate the average total colony count of each plate at the same dilution. Select the plates with colony counts between 30 and 300 as the standard for total colony count determination;

[0063] For two plates used at one dilution level, the average of the two plates should be adopted. If there is significant growth of sheet-like colonies on one of the plates, it should not be used, and the plate without sheet-like colony growth should be taken as the colony count for that dilution level. If the sheet-like colonies cover less than half of the plate and the colonies are evenly distributed in the remaining half, the colony count of half of the plate can be calculated and then multiplied by 2 to represent the colony count of the whole plate. When there are chain-like colonies growing in the plate, if there is only one chain, it can be regarded as one colony; if there are several chains from different sources, each chain should be counted as one colony. The dilution level with an average colony count between 30 and 300 should be selected, multiplied by the dilution factor and filled in the report. If there are two dilution levels with colony counts both between 30 and 300, it depends on the ratio between them. If the ratio is less than or equal to 2, the average should be reported; if it is greater than 2, the smaller number should be reported. If the average colony counts of all dilution levels are greater than 300, the average colony count of the highest dilution level should be multiplied by the dilution factor and reported. If the average colony counts of all dilution levels are less than 30, the average colony count of the lowest dilution level should be multiplied by the dilution factor and reported. If there is no colony growth in all dilution levels, it should be reported as less than 1 multiplied by the lowest dilution factor. If the average colony counts of all dilution levels are not between 30 and 300, and some are greater than 300 or less than 30, the average colony count closest to 30 or 300 should be multiplied by the dilution factor and reported;

[0064] When the colony count is within 100, it should be reported as the actual number; when it is greater than 100, two significant figures should be adopted, and the value after the two significant figures should be calculated by rounding. To shorten the number of zeros after the number, it can also be expressed in the exponent of 10;

[0065] Multiply the measured viable bacteria count result by 100 to obtain the actual recovered viable bacteria values of samples A, B, and C after 24 hours of cultivation, and the values are A, B, and C respectively;

[0066] Ensure that the experimental results meet the following requirements, otherwise the test is invalid:

[0067] The 5 parallel viable bacteria values of the same blank control sample B should meet that (the highest logarithm value - the lowest logarithm value) / the logarithm value of the average viable bacteria value is not greater than 0.3;

[0068] The actual recovered viable bacteria value A of sample A should all be not less than 1.0×10 5 cfu / slice, and the actual recovered viable bacteria value B of sample B should all be not less than 1.0×10 4 cfu / slice;

[0069] The antibacterial rate is calculated according to the following formula:

[0070] R = (B - C) / B × 100%;

[0071] In the formula:

[0072] R——Antibacterial rate (%)

[0073] B——Average number of recovered bacteria in the blank control sample, cfu / slice

[0074] C——Average number of recovered bacteria in the antibacterial sample, cfu / slice

[0075] Regarding osseointegration, its detection method and operation steps are as follows:

[0076] Corresponding to Comparative Example 1 and Examples 1 to 4, cylindrical rods with a diameter of 2 mm and a height of 6 mm were prepared from the same material and by the same process. According to the requirements of "GB / T 16886.6-2022 Biological evaluation of medical devices - Part 6: Tests for local effects after implantation", the rods were implanted into the femurs of New Zealand white rabbits through a bone drill. The fascia and skin incisions were sutured with medical sutures, and antibiotics were used for anti-inflammatory treatment for three days after the operation. The animals were euthanized 4 weeks after implantation. The implantation site was observed macroscopically, and the implanted rod and enough surrounding unaffected tissue were excised and fixed in 10% formaldehyde solution for at least 48 h. After fixation, the tissue including the implantation site was dehydrated, decalcified, embedded, and HE-stained for pathological analysis. The stained tissue sections were placed under an optical microscope to observe the tissue reaction around the implantation site. The degree of tissue reaction was determined by measuring the distance from the implant / tissue interface to the unaffected area with normal tissue and vascular characteristics, including the thickness of the fibrous capsule cavity, the number and types of inflammatory cells, and other abnormal conditions at the implant-rod / tissue interface.

[0077] The structures of the one-piece silicon nitride implants in Examples 1 to 4 are as Figure 1 shown. The one-piece silicon nitride implant includes an integrally formed abutment, neck, and root;

[0078] The implant is successively provided with a first thread, a second thread, and a third thread from the root to the neck. The first thread and the second thread are provided on the root, and the third thread is provided on the neck;

[0079] The first thread is a conical external thread, and three cutting grooves are provided in the first thread area;

[0080] The second thread and the third thread are cylindrical external threads;

[0081] The first thread area and the second thread area are provided with a pore layer on the surface, and the porosity of the pore layer is controlled to be 60%.

[0082] The angle α of the cone in the conical external thread area is 10°, the cutting groove angle is half of the cone angle, and the cutting groove width is 2 mm.

[0083] The thread profile of the first thread is a zigzag thread, the radius of the crest arc is 0.1 mm, the radius of the bottom arc transition is 0.4 mm, the pitch is 0.6 mm, the thread depth is 0.6 mm, and the thread length L1 is 0.35L, where L is the total length of the root and the neck;

[0084] The thread profile of the second thread is a trapezoidal thread, the width of the crest is 0.2 mm, the radius of the bottom arc transition is 0.4 mm, the pitch is 1.0 mm, the thread depth is 0.6 mm, and the thread length L2 is 0.45L;

[0085] The thread profile of the third thread is a triangular thread, the radius of the crest arc is 0.1 mm, the radius of the bottom arc transition is 0.4 mm, the pitch is 0.2 - 0.4 mm, the thread depth is 0.1 mm, and the thread length L3 is 0.2L; the neck diameter D is set to 10 mm.

[0086] The axial length L4 of the abutment is 5 mm.

[0087] Example 1

[0088] The process of preparing the silicon nitride dental implant assembly in this example is as follows.

[0089] Feeding preparation step

[0090] S1, Weigh 425 g of silicon nitride powder, 10 g of zirconia, and 30 g of magnesia and add them to the vacuum ball mill jar of a vacuum planetary mixer. Ball mill for 12 h at a speed of 300 r / min to obtain a ball mill slurry; the vacuum ball mill jar uses a nylon inner liner, the grinding medium is 99.95% high-purity silicon nitride microbeads with a diameter of 0.5 mm, and the solvent is anhydrous ethanol; when using anhydrous ethanol as the solvent, the vacuum ball mill jar needs to be evacuated and nitrogen gas needs to be introduced before ball milling, and the operation is repeated until there is no oxygen residue in the vacuum ball mill jar, generally repeating the operation 3 - 5 times is sufficient;

[0091] S2, Use a pressure spray granulator to spray granulate the ball mill slurry to obtain granulated powder; the inlet temperature of the dryer in the pressure spray granulator is 50 °C, the outlet temperature is 30 °C, the pressure difference of the cyclone separator is 200 Pa, the inner diameter and wall thickness of the central hole of the nozzle are both 0.16 mm, the pressure is 2.0 MPa, the spray angle range of the ceramic spiral nozzle is 60°, the feeding rate is 50 mL / min, and then classify the powder after spray drying through a vibrating screen separator to obtain granulated powder with an average diameter of 0.9 microns;

[0092] S3. Add 465 g of granulated powder, 15 g of polypropylene, 10 g of polyvinylpyrrolidone, and 10 g of polytetrafluoroethylene into the mixing chamber of a vacuum mixer. The mixing temperature is 100 °C and the mixing time is 4 h to obtain the feedstock. Before mixing, it is necessary to evacuate the air and introduce nitrogen, and repeat the operation until there is no oxygen residue in the mixing chamber.

[0093] Injection molding step

[0094] Perform injection molding on the prepared feedstock and send it into an injection molding machine for injection. The melt is injected into a mold at a temperature of 100 °C under high pressure. The injection pressure is 80 MPa, the injection temperature is 160 °C, the injection speed is 10 mm / s, and the pressure is maintained for 3 min, and then it is cooled to room temperature to form a silicon nitride crown green body and a one-piece silicon nitride implant green body respectively.

[0095] Laser etching step

[0096] Perform laser etching on the part of the one-piece silicon nitride implant green body corresponding to the root of the finished product. The scanning pitch of the laser etching is 0.5 mm.

[0097] Decorative layer slurry preparation step

[0098] Weigh 32 g of kaolin, 25 g of palygorskite, 15 g of quartz, 10 g of potassium feldspar, 6 g of calcite, 5 g of titanium dioxide, 4 g of yttrium oxide, 2 g of zirconium oxide, and 1 g of silicon nitride. According to the ratio of the above raw materials: zirconia grinding balls: deionized water mass ratio = 1:1.5:2, add them into the vacuum ball mill tank (with a nylon liner) of a vacuum planetary mixer and mix and ball mill at a speed of 300 r / min for 30 h to obtain the surface layer slurry.

[0099] Thermal debinding step

[0100] Place the laser-etched one-piece silicon nitride implant green body and the silicon nitride crown green body in a flowing inert gas atmosphere, heat them to 400 °C at a heating rate of 10 °C / min, and the sintering time is 2 h.

[0101] Decorative pretreatment step

[0102] Immerse the silicon nitride crown green body after the thermal debinding step into the surface layer slurry, take it out after 2 min of sufficient infiltration, and dry it naturally.

[0103] Sintering step

[0104] The silicon nitride implant green body after the thermal debinding step and the silicon nitride crown green body infiltrated with the surface layer slurry are placed in a flowing inert gas atmosphere for three-stage sintering; in the first stage, it is heated to the sintering temperature of 1000 °C at a heating rate of 10 °C / min, and the sintering time is 2 h. In the second stage, it is heated to the sintering temperature of 1400 °C at a heating rate of 8 °C / min, and the sintering time is 2 h; in the third stage, it is pressure-sintered, and the inert gas pressure is increased from normal pressure to 3 MPa, and it is heated to the sintering temperature of 1900 °C at a heating rate of 5 °C / min, and the sintering time is 2 h, obtaining an implant combination composed of a silicon nitride implant and a silicon nitride crown.

[0105] Example 2

[0106] The difference from Example 1 is that the weight of silicon nitride is adjusted to 440 g.

[0107] Example 3

[0108] The difference from Example 1 is that the weight of zirconia is adjusted to 30 g and the weight of magnesium oxide is adjusted to 10 g.

[0109] Example 4

[0110] The difference from Example 1 is that the weight of zirconia is adjusted to 25 g and the weight of magnesium oxide is adjusted to 15 g.

[0111] Comparative Example 1

[0112] Using titanium alloy TC4, an implant with the same dimensional parameters as in Example 1 is machined, and surface sandblasting treatment is performed to form a titanium alloy TC4 implant with a rough surface.

[0113] Through performance testing, the results shown in Table 1 are obtained.

[0114] Table 1 Performance Test Table Category <![CDATA[Density g / cm 3 > Hardness HV Compressive strength MPa <![CDATA[Fracture toughness MPa·m 1 / 2 > Antibacterial rate Osseointegration Comparative example 1 4.4 340 886 55 6% A small amount of proliferated fibroblasts around the implant showed fibrosis to form fibrous callus. Example 1 1.62 1451 2630 8.3 92% There was no abnormal reaction in the tissue around the implantation site. The implant was closely combined with the bone tissue. Osteocytes began to proliferate, trabeculae were visible, and new bone developed well. Example 2 1.52 1449 2650 6.1 89% There was no abnormal reaction in the tissue around the implantation site. The implant was closely combined with the bone tissue. Osteocytes began to proliferate, trabeculae were visible, and new bone developed well. Example 3 1.72 1426 2580 7 93% There was no abnormal reaction in the tissue around the implantation site. The implant was closely combined with the bone tissue. Osteocytes began to proliferate, trabeculae were visible, and new bone developed well. Example 4 1.66 1460 2720 8.3 91% There was no abnormal reaction in the tissue around the implantation site. The implant was closely combined with the bone tissue. Osteocytes began to proliferate, trabeculae were visible, and new bone developed well.

[0115] According to the above table, the dental implants prepared in the embodiments of the present invention not only retain the good antibacterial property of silicon nitride, promote bone integration, but also give full play to the high hardness and high compressive mechanical properties of silicon nitride, and also have the basic fracture toughness required for oral implants.

[0116] It should be emphasized that: the above are only the preferred embodiments of the present invention, and do not constitute any form of limitation to the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A silicon nitride dental implant assembly, characterized in that: It includes a silicon nitride crown and a one-piece silicon nitride implant, both of which can be bonded and fixed; The silicon nitride crown comprises a silicon nitride crown body and a facing layer, which is obtained by applying a facing layer slurry on a silicon nitride crown body preform and then sintering; The silicon nitride implant and the silicon nitride crown are made of the same material, and are both made by sintering an injection-molded preform; by weight, the preform comprises: 80% to 88% silicon nitride powder, 5% to 10% sintering aid, 3% to 6% binder, 2% to 5% dispersant and 1% to 3% lubricant, totaling 100%; The formula of the finishing layer slurry includes, by weight: 30 to 40 parts by weight of kaolin, 20 to 30 parts by weight of palygorskite, 12 to 16 parts by weight of quartz, 10 to 20 parts by weight of potassium feldspar, 5 to 9 parts by weight of calcite, 4 to 6 parts by weight of titanium dioxide, 2 to 5 parts by weight of yttrium oxide, 2 to 5 parts by weight of zirconium oxide and 2 to 5 parts by weight of silicon nitride, totaling 100 parts by weight; in addition, it also includes 170 to 220 parts by weight of water.

2. The silicon nitride dental implant assembly according to claim 1, characterized in that: The sintering aid includes at least one of zirconium oxide, ytterbium oxide, magnesium oxide and boron nitride; The binder is at least one of polyethylene, polypropylene, polyoxymethylene, polylactic acid, paraffin, beeswax, polycarbonate, modified cellulose, polystyrene, polyhydroxyalkanoate, polyethylene glycol, and phenolic resin; The dispersant is at least one of oleic acid, phosphate, ammonium polyacrylate, lecithin, triethyl phosphate, polyacrylic acid, castor oil, polyvinyl pyrrolidone, C12 alkyl polyglycoside quaternary ammonium salt, and tetramethylammonium hydroxide; The lubricant is at least one of zinc stearate, polyethylene wax, ethylene bis stearamide, polytetrafluoroethylene, silicone oil, beeswax and lauric acid.

3. A process for preparing a silicon nitride dental implant assembly, characterized in that: The following steps are involved: The steps of preparing the feed material are as follows: weighing silicon nitride powder and a sintering aid, adding a solvent, mixing and ball milling in an inert gas atmosphere, and then spray granulating to obtain granulated powder; uniformly mixing the granulated powder, a binder, a dispersant and a lubricant to obtain a feed material; in terms of weight ratio, the feed material includes: 80% to 88% silicon nitride powder, 5% to 10% sintering aid, 3% to 6% binder, 2% to 5% dispersant and 1% to 3% lubricant, which is 100% in total; The preparation steps of the finishing layer slurry are as follows: kaolin, palygorskite, quartz, potassium feldspar, calcite, titanium dioxide, yttrium oxide, zirconium oxide and silicon nitride are weighed, a solvent is added, and the mixture is mixed and ball-milled in a ratio of raw material: grinding ball: solvent mass ratio = 1: (1.3-1.5): (1.7-2.2) to obtain a finishing layer slurry; in terms of weight ratio, the finishing layer slurry includes: 30%-40% kaolin, 20%-30% palygorskite, 12%-16% quartz, 10%-20% potassium feldspar, 5%-9% calcite, 4%-6% titanium dioxide, 2%-5% yttrium oxide, 2%-5% zirconium oxide and 2%-5% silicon nitride; Injection molding step: injecting the prepared feed material into a mold to obtain a melt after the injection, then maintaining the pressure for a certain period of time, and then gradually cooling the melt to room temperature to solidify into a silicon nitride implant blank and a silicon nitride crown blank of a preset shape; Laser etching step: laser etching the part of the silicon nitride implant blank corresponding to the root of the finished product; Thermal degreasing step: placing the laser-etched silicon nitride implant blank and the silicon nitride crown blank in a flowing inert gas atmosphere and heating them to 400-800° C. for degreasing and sintering; Finishing pretreatment step: immerse the silicon nitride crown blank after the thermal degreasing step into the finishing layer slurry until it is fully wetted, then take it out and dry it naturally; Sintering step: placing the silicon nitride implant blank that has undergone the thermal degreasing step and the silicon nitride crown blank that has been impregnated with the finishing layer slurry in a flowing inert gas atmosphere for three-stage sintering; the first stage is normal pressure sintering, heating to a sintering temperature of 1000-1200°C, and the sintering time is 1-2h; the second stage is normal pressure sintering, heating to a sintering temperature of 1400-1600°C, and the sintering time is 1-2h; the third stage is gas pressure sintering, the inert gas pressure is increased from normal pressure to 2-10MPa, and the temperature is continued to be raised to a sintering temperature of 1600-1900°C, and the sintering time is 2-6h, to obtain a dental implant assembly consisting of a silicon nitride implant and a silicon nitride crown.

4. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the feeding preparation step, the ball milling time is 12 to 36 hours and the rotation speed is 120 to 360 r / min.

5. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: The spray granulation is completed by a pressure spray granulator; the inlet temperature of the dryer is set to 40-80°C, the outlet temperature is set to 20-40°C, the pressure difference of the cyclone separator is set to 200-240Pa, the inner diameter of the nozzle center hole and its wall thickness are both 0.16mm, the pressure is set to 2.0-2.8MPa, the jet angle range of the ceramic spiral nozzle is set to 60°-120°, and the feed rate is set to 10-100mL / min.

6. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the feed preparation step, the feed is prepared by adding granulating powder, a binder, a dispersant and a lubricant into a vacuum mixer and mixing at a mixing temperature of 80 to 120° C. for 2 to 8 hours.

7. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the injection molding step, the injection pressure is 80-90 MPa, the injection temperature is 160-170° C., the injection speed is 10-30 mm / s, and the mold temperature is 80-100° C.

8. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the injection molding step, the pressure is maintained for 2 to 8 minutes.

9. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the laser etching step, the scanning interval of the laser etching is 0.5 to 1.5 mm.

10. The process for preparing the silicon nitride dental implant assembly according to claim 3, characterized in that: In the thermal debinding step, the heating rate is 10 to 25°C / min and the sintering time is 2 to 6 hours.

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