Porous silicon nitride ceramic integrated dental implant capable of resisting bacteria, preventing breakage and promoting osseointegration and preparation method of porous silicon nitride ceramic integrated dental implant

Abstract

The invention provides a porous silicon nitride ceramic integrated dental implant capable of resisting bacteria, preventing breakage and promoting osseointegration and a preparation method of the porous silicon nitride ceramic integrated dental implant, and belongs to the field of novel dental materials and application products thereof. The integrated dental implant comprises a first area, a second area, a third area and an abutment part, the first area, the second area and the third area jointly form an implant part, and the implant part and the abutment part are integrally prepared without assembly connection to form the integrated dental implant. The dental implant is made of silicon nitride ceramic with an irregular rough porous surface in gradient distribution. Based on a customized silicon nitride ceramic material formula, by means of a special silicon nitride ceramic injection molding preparation process and in combination with a targeted dental implant product design, the porous silicon nitride ceramic integrated dental implant which is antibacterial, anti-breaking and capable of promoting osseointegration is provided.

Description

Technical Field

[0001] The present invention relates to the field of new dental materials and their application products, and in particular to an antibacterial, fracture-proof and bone-integration-promoting porous silicon nitride ceramic integrated dental implant and a preparation method thereof. Background Art

[0002] As an important technology in modern stomatology, dental implants have become one of the main ways to solve the problem of missing teeth. The core principle is to accurately implant artificial tooth roots (implants) into the upper / lower jaws of the missing teeth area. After a period of bone integration, the implants form a tight connection with the surrounding bone tissue, and then the base is assembled on the implants through screws and other connectors, and then the crown part above is firmly supported on the base. This technology not only restores the chewing function of teeth, but also greatly improves the aesthetics and voice function, becoming the preferred treatment for many patients.

[0003] As a biomedical implant, the first thing that needs to be satisfied is safety, that is, the biocompatibility of materials and products, and then the effectiveness, that is, the mechanical properties of materials and products can effectively meet their intended use. At present, the materials of implants and abutments in the domestic market are mainly pure titanium and titanium alloys, while implants based on zirconia ceramics have appeared in the international market. As for the material of the crown on the abutment, zirconia ceramics are the main material in the world. With the help of complete imaging data and advanced digital processing technology, highly personalized crowns can be obtained, which together with the above-mentioned abutments and implants constitute a complete set of implant teeth.

[0004] Titanium alloys are widely used due to their good biocompatibility and mechanical properties. However, the incidence of metal hypersensitivity and allergic reactions is increasing in industrialized countries around the world. The possibility of metal hypersensitivity in patients cannot be completely ruled out before surgery. Postoperative examination and diagnosis of metal allergy adds an additional burden to patients and health insurers. Therefore, it is more important to use ceramic implant materials with better biocompatibility in the body.

[0005] Zirconia ceramics are similar in color to natural teeth, have advantages in aesthetic restoration, and their mechanical properties can basically meet the needs of oral chewing function. Although the current dental implants have made significant progress in materials and product design, there are still some obvious defects and deficiencies, which constitute the following three clinical pain points that need to be solved urgently.

[0006] (1) Lack of antibacterial properties

[0007] The oral cavity is a complex microbial environment. Implants are easily invaded by bacteria after implantation, leading to peri-implantitis, which in turn leads to the absorption of bone tissue around the implant, hindering the occurrence of complications such as bone integration, thus affecting the effect of the surgery and the life of the implant. Although titanium alloys have good biocompatibility, titanium alloys themselves do not have antibacterial properties, and the biological inertness of their surfaces makes it easy for bacteria to attach and form plaque biofilms, which greatly increases the risk and degree of infection and the difficulty of antibacterial treatment. Although the surface of titanium alloy implants can be modified to enhance their antibacterial effect, the effects of these additional surface treatments are not ideal, not long-lasting, and increase manufacturing costs.

[0008] (2) Insufficient mechanical properties

[0009] Although titanium alloy and zirconia ceramics have high strength, they still have a certain risk of fatigue fracture or loosening under some complex chewing forces, especially when subjected to long-term uneven loads or large lateral forces, which affects the long-term stability of the implant and even leads to restoration failure. After the implant is broken, repair becomes very difficult and often requires re-implantation, which brings additional financial burden and physical pain to the patient.

[0010] (3) Poor bone integration

[0011] The strength of the combination between the implant and the bone tissue directly affects the service life and success rate of the implant. Whether the implant can form stable bone integration is the key to its success. The existing implant design fails to fully consider the process of accelerating bone integration, resulting in a longer healing time and affecting the patient's recovery speed.

[0012] In summary, in order to overcome the above three clinical problems and further improve the performance of dental implants, thereby improving patients' oral health and quality of life, it is necessary to work together from two dimensions: the raw materials and product design of dental implants, to achieve the above goals.

[0013] In the field of biomedical ceramic implants, alumina ceramics (commonly known as "yellow pottery") first appeared, followed by zirconia ceramics (commonly known as "white pottery"), and then zirconia-toughened alumina ceramics (commonly known as "pink pottery"). The main problem with yellow pottery is that it has low toughness and is therefore easy to break. White pottery has better toughness than yellow pottery, but zirconia ceramics are a metastable phase material, and aging of their performance is a significant defect. Aging of zirconia ceramics refers to its spontaneous transformation from tetragonal phase to monoclinic phase. During the transformation, the volume expands, resulting in surface roughness, which increases wear. In addition, microcracks and even macrocracks will occur, which significantly reduces the mechanical properties of the material. Pink pottery is an upgraded product of yellow pottery. Its toughening mechanism is to add 10%-30% yttria-stabilized tetragonal zirconia particles (Y-TZP) dispersed in a stable alumina matrix. This type of Y-TZP crystal is dispersed and distributed, and it utilizes the phase change of metastable zirconia to achieve structural changes and prevent potential crack expansion. This type of phase change toughening has aging problems because zirconia itself has aging problems. Aging generally starts from the stressed surface and gradually develops inward. Aging is more serious in a humid environment. How its performance will change under the complex physiological environment of the human body is still not fully determined.

[0014] From the development trend of high-performance structural ceramics, along the development ladder of advanced technical ceramics, compared with the above-mentioned three oxide ceramics, non-oxide ceramics - silicon nitride ceramics, in addition to the advantages of general ceramics, as a biosafe and chemically stable ceramic material, for dental implants, silicon nitride ceramics, known as the "all-around champion in the ceramic world", is a potential, excellent, and upgraded raw material choice. Summary of the invention

[0015] The purpose of the present invention is to propose an antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic one-piece dental implant and a preparation method thereof, based on a customized silicon nitride ceramic material formula, with the help of a special silicon nitride ceramic injection molding preparation process, combined with targeted dental implant product design, to provide a safe, effective and efficient silicon nitride ceramic one-piece dental implant.

[0016] The technical solution of the present invention is achieved in this way:

[0017] The present invention provides an antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic one-piece dental implant, the one-piece dental implant comprising a first region, a second region, a third region and a base portion, the first region, the second region, and the third region together constituting an implant portion, the implant portion and the base portion being integrally prepared without assembly connection to constitute the one-piece dental implant, the material used for the dental implant being a silicon nitride ceramic having an irregular rough porous surface designed with a gradient distribution.

[0018] As a further improvement of the present invention, the porous silicon nitride ceramic is prepared from the following raw materials by weight: 60-90 parts of silicon nitride and 10-40 parts of additives, wherein the additives include a binder, a dispersant, a lubricant, a sintering aid and other performance aids.

[0019] As a further improvement of the present invention, the binder is selected from at least one of high-density polyethylene, ethylene-vinyl acetate copolymer, polystyrene, random polypropylene, polyethylene glycol, and phenolic resin; the dispersant is selected from at least one of calcium stearate, triethyl phosphate, polyacrylic acid, castor oil, polyvinyl pyrrolidone, C12 alkyl polysaccharide quaternary ammonium salt, tetramethylammonium hydroxide, and sodium hexametaphosphate; the lubricant is selected from at least one of microcrystalline wax, stearic acid, and dibutyl phthalate ; The sintering aid is selected from at least two of aluminum oxide, zirconium oxide, yttrium oxide, ytterbium oxide, magnesium oxide, lanthanum oxide, neodymium oxide, strontium oxide, cerium oxide, erbium oxide, thulium oxide, and lutetium oxide; the other performance aids are selected from at least four of zinc oxide, copper oxide, chromium oxide, titanium oxide, titanium carbide, silicon carbide, titanium nitride, boron nitride, ytterbium fluoride, magnesium fluoride, ytterbium dihydride, ammonium carbonate, ammonium chloride, charcoal, sawdust, starch, chitosan, bioglass, fluoroapatite, and hydroxyapatite.

[0020] As a further improvement of the present invention, the dental implant is an integrated conical cylinder with three sections of external thread design with different styles, the outer diameter of the cylindrical part is D, the overall length of the implant is L, the lengths of the first area, the second area and the third area of ​​the integrated dental implant are L1, L2 and L3 respectively, L4 is the height of the base part, the cone angle of the lower end conical part of the dental implant is α, the range of D is 3.0-7.0mm, the range of L is 6.0-20mm, the range of L1 is 35-40%L, the range of L2 is 40-45%L, the range of L3 is 15-25%L, the range of L4 is 3-6mm, the range of α is 10-15°, and the variable range of the axis of the base part is within a cone with a cone angle of 60 degrees with the center of the gingival horizontal plane of the dental implant as the vertex.

[0021] As a further improvement of the present invention, the lower end of the dental implant (towards the jawbone) has a first region with a conical external thread, a sawtooth thread, a crest arc radius of 0.1-0.2 mm, a bottom transition arc radius of 0.4-0.5 mm, a pitch of 0.6-1.0 mm, and a thread depth of 0.6-1.0 mm; the middle section of the dental implant, the second region, has a cylindrical external thread, a trapezoidal thread, a crest width of 0.2-0 .4mm, the radius of the tooth bottom transition arc is 0.4-0.5mm, the pitch is 0.6-1.0mm, and the thread depth is 0.2-1.0mm; the upper end of the dental implant (towards the crown), the third area, is a cylindrical external thread, the thread profile is a triangular thread, the top arc radius is 0.1-0.2mm, the bottom transition arc radius is 0.4-0.5mm, the pitch is 0.2-0.4mm, and the thread depth is 0.02-0.5mm.

[0022] As a further improvement of the present invention, the lower end of the dental implant (towards the jawbone) has 2-4 grooves on the conical external threaded portion in the first area, the angle formed between the groove and the implant axis is half of the cone angle α, the inclination direction is the same as the thread direction, and the groove width is 1-3 mm.

[0023] As a further improvement of the present invention, the surface of the dental implant, the part implanted in the jawbone, i.e., the first area, the second area, and the third area (L1+L2+L3), are irregularly rough and porous, and the porosity is distributed in a gradient from less to more from the inner core to the outer surface of the implant. The thickness of the porous layer is 600-900 μm, the pore size range is 60-600 μm, the average pore size is controlled at 250-300 μm, and the porosity is 35-75%.

[0024] The present invention further protects a method for preparing the above-mentioned antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant, comprising the following steps:

[0025] S1. Weighing ratio: According to the above material formula, accurately weigh the appropriate amount of silicon nitride and sintering aid;

[0026] S2. Mixed ball milling: The raw materials weighed and proportioned above are mixed and placed in a vacuum ball mill with a nylon lining in a vacuum planetary mixer. The grinding medium is 99.95% high-purity silicon nitride microbeads with a diameter of 0.5 mm. The ball milling time in the ethanol solvent is 12-36 hours, and the speed is 120-360r / min. Before ball milling, the vacuum ball mill needs to be evacuated and nitrogen is introduced, and the cycle is repeated 3-5 times to ensure that there is no oxygen residue in the vacuum ball mill.

[0027] S3. Spray granulation: The slurry after ball milling is introduced into 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 0.16 mm, the pressure is set to 2.0-2.8MPa, the jet angle range of the ceramic spiral nozzle is set to 60-120 degrees, the feed rate is set to 10-100mL / min, and the spray-dried powder is classified by a vibrating screen separator to obtain granulated powder with an average diameter of less than 0.9 microns.

[0028] S4. Feed preparation: According to the above material formula, accurately weigh the above-obtained granulation powder and appropriate amount of binder, dispersant and lubricant, put them into a vacuum mixer, set the mixer temperature to 160°C, the mixer speed to 30-40r / min, and the mixing time to 2-8h, and obtain feed A for standby use. On the basis of feed A, mix in appropriate amount of other performance additives, and obtain feed B for standby use according to the above preparation process. Before mixing, vacuum and nitrogen should be introduced, and the cycle should be repeated 3-5 times to ensure that there is no oxygen residue in the mixing chamber.

[0029] S5. Injection molding: Heat the prepared feed A to convert it into a viscous melt, inject the melt into the preheated mold, inject feed A at the first speed, and then inject feed B at the second speed, and inject and fill it into the mold cavity designed according to the requirements of the final product in stages, so that the core inside the cavity is mainly feed A, and the surface is mainly feed B. The melt gradually cools and solidifies to form a blank of the desired shape. The injection temperature is set to 150-180℃, the injection pressure is set to 70-100MPa, and the melt is injected into the mold with a high pressure injection temperature set to 80-100℃, and the injection speed is set to 10-30mm / s. In the mold, the holding time is set to 2-8min to ensure the density and shape stability of the blank. The melt gradually cools and solidifies to form a blank of the desired shape.

[0030] S6. Laser etching: The front end of the blank prepared above is implanted on the surface of the jawbone (i.e., the first area, the second area, and the third area, with a length of L=L1+L2+L3), and the surface roughness is significantly increased by laser etching, and the scanning interval of the laser etching is set to 0.5-1.5 mm. The rear end surface of the blank, i.e., the appropriate area of ​​the integrated abutment, is laser etched with information such as the specifications, model, and batch number of the product to meet the traceability requirements of regulatory laws and regulations for implants.

[0031] S7. Degreasing biscuit: The above-mentioned laser-etched biscuit is placed in a degreasing furnace. The furnace needs to be evacuated and nitrogen is introduced. The cycle is repeated 3-5 times to ensure that there is no oxygen residue in the furnace. Then, the staged degreasing biscuit is carried out under the protection of flowing nitrogen: In the first stage, the heating rate is set to 30℃ / h, from room temperature to 160℃, and then kept warm for 2h. In the second stage, the heating rate is set to 5℃ / h, from 160℃ to 300℃, and then kept warm for 2h, and then raised to 360℃ at the same heating rate, and then kept warm for 2h. In the third stage, the heating rate is set to 8℃ / h, from 360℃ to 400℃, and then kept warm for 2h. In the fourth stage, the heating rate is set to 6℃ / h, from 400℃ to 500℃, and then kept warm for 2h. Then cool to room temperature at a cooling rate of 50℃ / h. Such a process arrangement is intended, on the one hand, to completely remove the binder and its decomposition products, and on the other hand, to avoid defects such as bubbling and cracking caused by increased internal pressure.

[0032] S8. Preliminary sintering: The above-mentioned degreased biscuit is placed in a sintering furnace. The furnace needs to be evacuated and nitrogen is introduced. This cycle is repeated 3-5 times to ensure that there is no oxygen residue in the furnace. Then, two-stage preliminary sintering is performed under the protection of flowing nitrogen. The sintering temperature of the first stage is set to 1000-1100℃, and the sintering time is set to 1-2h. The sintering temperature of the second stage is set to 1100-1200℃, and the sintering time is set to 1-2h, so as to obtain a blank. Such a process arrangement is intended to obtain the expected excellent comprehensive performance;

[0033] S9. Formal sintering: For the blanks treated as above, formal sintering is carried out under nitrogen pressure protection, the nitrogen pressure is set to 2-9MPa, and the step-by-step heating method is adopted. The first stage sintering temperature is set to 1200-1500℃, the sintering time is set to 1-2h, and the second stage sintering temperature is set to 1500-1900℃, the sintering time is set to 2-6h. For example, after keeping the temperature at 1650℃ for 2h, the temperature is raised to 1850℃ and kept for 2h, so as to obtain the semi-finished product. Such a process arrangement is intended to obtain the expected excellent comprehensive performance.

[0034] S10. Subsequent treatment: The semi-finished product with an irregular porous surface with gradient distribution (i.e., dense inner core and gradually porous outer surface) after the above treatment is placed in hydrofluoric acid, hydrogen peroxide aqueous solution or a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide (mixing ratio of 1:1-2) to react, so that the roughness of the irregular porous surface of the fired semi-finished product is further improved, and then placed and ultrasonically cleaned to obtain the finished product. The standing time is set to 24-48h. Then put it in an ultrasonic cleaning machine and clean it with distilled water for 5-15min, and the cleaning temperature is set to 70-90℃. Then continue cleaning after changing to new distilled water, and repeat the cleaning cycle 5 times to obtain the finished product.

[0035] The present invention aims to provide a safe, effective and highly effective porous silicon nitride ceramic integrated dental implant that is antibacterial, anti-fracture and promotes bone integration based on a customized silicon nitride ceramic material formula, with the help of a special silicon nitride ceramic injection molding preparation process, combined with targeted dental implant product design.

[0036] It is specifically reflected in the following three aspects: antibacterial properties, mechanical properties and bone integration properties:

[0037] First, based on its excellent biocompatibility, this product has an inhibitory effect on the colony formation of Porphyromonas gingivalis, Staphylococcus aureus and Escherichia coli, thereby reducing the probability of peri-implantitis and implant failure. Because in the water-containing condition of the physiological environment, silicon nitride can dissociate hydrogen atoms from the siloxy functional groups, making its surface negatively charged, and hindering bacteria from attaching to the silicon nitride surface through electrostatic action. At the same time, the reaction of the amino functional groups on the silicon nitride surface will release ammonia to form peroxynitrite, thereby increasing the pH value of the medium, thereby establishing a weak alkaline environment that is not conducive to bacterial adhesion, affecting the normal metabolism of bacteria, and ultimately leading to the death of bacteria, so that this product has antibacterial and antibacterial properties.

[0038] Secondly, compared with current dental implants, this product has high hardness, high compressive strength and excellent fracture toughness in terms of mechanical properties, which further reduces the risk of implant fracture and solves the clinical pain point in this area.

[0039] Third, this product can induce osteogenic regeneration in vivo, promote the bone integration process, speed up the patient's recovery, and thus improve the service life and success rate of the implant. The reason for this is that, on the one hand, with the help of a special silicon nitride ceramic injection molding preparation process, combined with targeted dental implant product design, a gradient-distributed irregular rough porous hydrophilic surface is formed, which can increase osteoblast adhesion, which is the basis for later osteogenic differentiation, matrix mineralization and bone regeneration. On the other hand, the release of silicic acid and nitrogen-containing compounds on the silicon nitride surface enhances cell metabolism, proliferation and osteogenic differentiation activity. Silicic acid and nitrogen-containing compounds can affect the morphogenic activity of osteoblasts by upregulating the expression of osteoprotegerin and bone morphogenetic protein. While strongly stimulating osteoblast differentiation, they also inhibit the formation of osteoclasts. In addition, the precipitation of silicate also creates a weakly alkaline environment, which has a positive effect on osteoblast proliferation and subsequent osteoblast differentiation. The combined effects of these factors and surrounding tissues and cells in the body contribute to the integration of this silicon nitride ceramic dental implant with the surrounding bone tissue.

[0040] In addition to solving the above three clinical pain points, this silicon nitride ceramic dental implant is also partially radio-blocking. Through imaging examinations, the integration of the implant and the surrounding bone tissue can be clearly seen, and there will be no radiographic artifacts in dental CT scans like the current titanium alloy implants. In addition, the radiation density of silicon nitride ceramic implants is equivalent to that of tooth enamel, so the tightness of the silicon nitride implant and the surrounding tissue, especially the bone tissue, can be accurately evaluated.

[0041] The present invention has the following beneficial effects:

[0042] (1) Antibacterial

[0043] On the basis of excellent biocompatibility, it has an inhibitory effect on the colony formation of Porphyromonas gingivalis, Staphylococcus aureus and Escherichia coli, thereby reducing the probability of peri-implantitis and implant failure.

[0044] (2) Anti-break

[0045] In terms of mechanical properties, it has high hardness, high compressive strength and excellent fracture toughness, which further reduces the risk of implant fracture.

[0046] (3) Promote bone integration

[0047] It can induce bone regeneration in the body, promote the bone integration process, speed up the patient's recovery, and thus increase the service life and success rate of the implant. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 Product structure diagram of porous silicon nitride ceramic integrated dental implant for antibacterial, anti-fracture and bone integration;

[0050] Among them, 1 is the first area, 2 is the second area, 3 is the third area, and 4 is the base part. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Comparative Example

[0053] Its materials meet the requirements of "ISO 5832-3 Metal Materials for Surgical Implants Part 3 Ti-6Al-4V Forged Alloy" in the "YY 0315-2023 Titanium and Titanium Alloy Dental Implants" standard. Machining is used as the molding method in the preparation process, and sandblasting is used as the post-processing method. In terms of product design, it adopts a conical cylindrical design with a triangular thread with a pitch of 0.8mm, a non-grooved design, and a rough surface.

[0054] Example 1

[0055] The material formula of this embodiment 1 is as follows:

[0056] 62% silicon nitride and 38% additives, wherein the additives are 8% high-density polyethylene as a binder, 1% calcium stearate as a dispersant, 8% microcrystalline wax as a lubricant, 4% aluminum oxide as a sintering aid, 2% zirconium oxide, 4% yttrium oxide as a sintering aid, and 2% zinc oxide, 2% titanium carbide, 3% starch and 4% hydroxyapatite as other performance aids.

[0057] Regarding the preparation process of Example 1, the detailed steps are as follows:

[0058] 1) Weighing ratio

[0059] According to the above material formula, accurately weigh appropriate amounts of silicon nitride and sintering aid.

[0060] 2) Mixed ball milling

[0061] The weighed raw materials were mixed and placed in a vacuum ball mill with a nylon lining in a vacuum planetary mixer. The grinding medium was 99.95% high-purity silicon nitride microbeads with a diameter of 0.5 mm. The ball mill was performed in an ethanol solvent for 24 hours at a speed of 240 r / min. Before ball milling, the vacuum ball mill needed to be evacuated and nitrogen gas was introduced. The cycle was repeated 5 times to ensure that there was no oxygen residue in the vacuum ball mill.

[0062] 3) Spray granulation

[0063] The slurry after ball milling is introduced into a pressure spray granulator. The inlet temperature of the dryer is set to 60°C, the outlet temperature is set to 30°C, the pressure difference of the cyclone separator is set to 220Pa, the inner diameter of the nozzle center hole and its wall thickness are both 0.16 mm, the pressure is set to 2.6MPa, the jet angle range of the ceramic spiral nozzle is set to 90 degrees, the feed rate is set to 60mL / min, and the spray-dried powder is then classified through a vibrating screen separator to obtain granulated powder with an average diameter of less than 0.9 microns.

[0064] 4) Feed preparation

[0065] According to the above material formula, the granulated powder obtained above and the appropriate amount of binder, dispersant and lubricant are accurately weighed and put into a vacuum mixer. The mixing temperature is set to 160°C, the mixing speed is 35r / min, and the mixing time is set to 6h to obtain feed A for standby use. On the basis of feed A, other performance additives are mixed in appropriate amounts, and feed B is obtained according to the above preparation process for standby use. Before mixing, it is necessary to evacuate and introduce nitrogen, and repeat this cycle 5 times to ensure that there is no oxygen residue in the mixing chamber.

[0066] 5) Injection molding

[0067] The prepared feed material A is fed into the injection molding machine, and the injection temperature is set to 165°C to transform it into a viscous melt. Then, the injection pressure is set to 85MPa, and the melt is injected into the mold with a temperature set to 90°C through high pressure. The injection speed is set to 30mm / s to inject feed material A, and then the injection speed is set to 10mm / s to inject feed material B. The mold cavity is injected and filled in stages, so that the core inside the cavity is mainly feed material A, and the surface layer is mainly feed material B. In the mold, the holding time is set to 6 minutes to ensure the density and shape stability of the blank. The melt gradually cools and solidifies to form a blank of the desired shape.

[0068] 6) Laser Etching

[0069] The front end of the blank prepared as above is implanted on the surface of the jawbone, i.e., the first area 1, the second area 2, and the third area 3, and the surface roughness is significantly increased by laser etching, and the scanning interval of the laser etching is set to 0.75 mm. The rear end surface of the blank, i.e., the appropriate area of ​​the integrated abutment, is laser etched with information such as the specification model and batch number of the product to meet the traceability requirements of regulatory laws and regulations for implants.

[0070] 7) Defatted biscuit

[0071] The above-mentioned laser-etched biscuit is placed in a degreasing furnace. The furnace needs to be evacuated and nitrogen is introduced. The cycle is repeated 5 times to ensure that there is no oxygen residue in the furnace. Then, the degreasing biscuit is carried out in stages under the protection of flowing nitrogen: In the first stage, the heating rate is set to 30℃ / h, from room temperature to 160℃, and then kept warm for 2h. In the second stage, the heating rate is set to 5℃ / h, from 160℃ to 300℃, then kept warm for 2h, and then raised to 360℃ at the same heating rate, and then kept warm for 2h. In the third stage, the heating rate is set to 8℃ / h, from 360℃ to 400℃, and then kept warm for 2h. In the fourth stage, the heating rate is set to 6℃ / h, from 400℃ to 500℃, and then kept warm for 2h. Then cool to room temperature at a cooling rate of 50℃ / h.

[0072] 8) Preparatory sintering

[0073] The above-mentioned degreased bisque-fired blank is placed in a sintering furnace. The furnace needs to be vacuumed and nitrogen is introduced. The cycle is repeated 5 times to ensure that there is no residual oxygen in the furnace. Subsequently, two-stage preliminary sintering is carried out under the protection of flowing nitrogen. The sintering temperature of the first stage is set to 1000°C and the sintering time is set to 1h. The sintering temperature of the second stage is set to 1200°C and the sintering time is set to 2h, thereby obtaining a blank.

[0074] 9) Formal sintering

[0075] The blank after the above treatment is formally sintered under nitrogen pressure protection. The nitrogen pressure is set to 5MPa. The step-by-step heating method is adopted. The sintering temperature of the first stage is set to 1400℃, the sintering time is set to 2h, and the sintering temperature of the second stage is set to 1800℃, the sintering time is set to 4h, so as to obtain a semi-finished product.

[0076] 10) Subsequent processing

[0077] The semi-finished product with an irregular porous surface having a gradient distribution (i.e., a dense inner core and a gradually porous outer surface) after the above treatment is placed in a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide (mixing ratio of 1:1.5) to react, so that the roughness of the irregular porous surface of the fired semi-finished product is further improved, thereby obtaining a better ability to promote bone integration. The standing time is set to 36h. Then it is placed in an ultrasonic cleaning machine and cleaned with distilled water for 10 minutes, and the cleaning temperature is set to 80℃. Then, the cleaning is continued after changing to new distilled water, and the finished product is obtained after repeating the cleaning cycle 5 times.

[0078] Regarding the product design part of Example 1, Figure 1 ,

[0079] The integrated dental implant includes a first region 1, a second region 2, a third region 3 and a base part 4. The first region 1, the second region 2, and the third region 3 together constitute an implant part. The above-mentioned implant part and the base part are integrally prepared without assembly connection to constitute the integrated dental implant. The material used for the dental implant is silicon nitride ceramic with an irregular rough porous surface designed with a gradient distribution.

[0080] The parameter details are as follows:

[0081] 1) Overall design

[0082] This antibacterial, anti-fracture, and bone-integration-promoting silicon nitride ceramic dental implant is a conical cylinder with an integrated base and three different styles of external thread designs.

[0083] The outer diameter of the cylindrical part is D = 4mm, the overall length of the implant is L = 10mm, the lengths of the three different thread sections are L1 = 4mm, L2 = 4mm and L3 = 2mm, L4 is the base height = 5mm. The cone angle of the conical part at the lower end of the implant is α = 12 degrees.

[0084] 2) Threaded part

[0085] At the lower end of the implant (towards the jawbone), the length of the first region 1 is L1, with a conical external thread, a sawtooth thread, a top arc radius of 0.2mm, a bottom transition arc radius of 0.4mm, a pitch of 0.8mm, and a thread depth of 1mm.

[0086] In the middle section of the implant, the length of the second region 2 is L2, with a cylindrical external thread, a trapezoidal thread profile, a crest width of 0.4 mm, a bottom transition arc radius of 0.5 mm, a pitch of 0.8 mm, and a thread depth of 0.8 mm.

[0087] At the upper end of the implant (towards the crown), the length of the third region 3 is L3, with a cylindrical external thread, a triangular thread, a top arc radius of 0.1mm, a bottom transition arc radius of 0.4mm, a pitch of 0.2mm, and a thread depth of 0.1mm.

[0088] 3) Grooving part

[0089] At the lower end of the implant, two grooves are opened on the conical external thread section (L1) of the first region 1, the angle between which and the axis of the implant is 6 degrees, the inclination direction is the same as the thread direction (right direction), and the groove width is 2mm.

[0090] 4) Porous part

[0091] The surface of this integrated implant, which is implanted in the jawbone (L1+L2+L3), is a gradient irregular porous rough structure, that is, the core of the implant is dense, and the surface of the implant is irregular, rough and porous. From the core to the surface, the porosity is distributed in a gradient from less to more. The thickness of the porous layer is 600um, the pore size range is 60 to 600um, the average pore size is controlled at 250um, and the porosity is 38%.

[0092] Example 2

[0093] The material formula part, the detailed configuration is as follows:

[0094] 72% silicon nitride and 28% additives, wherein the additives are 5% binder phenolic resin, 1% dispersant polyacrylic acid, 6% lubricant stearic acid, sintering aids are 2% zirconium oxide, 2% magnesium oxide, and other performance aids are 2% copper oxide, 3% titanium nitride, 3% charcoal and 4% bioglass.

[0095] The preparation process and product design are the same as those in Example 1.

[0096] Example 3

[0097] The material formula is the same as that in Example 1.

[0098] The details of the preparation process that are different from Example 1 are as follows:

[0099] Degreasing biscuit calcining: the heating rate is set to 40℃ / h, the degreasing temperature is set to 480℃, and the holding time is set to 24h;

[0100] Pre-sintering: the sintering temperature is set to 1200°C and the sintering time is 3h;

[0101] Formal sintering: the sintering temperature is set to 1850℃ and the sintering time is 6h;

[0102] Subsequent treatment: Place in hydrofluoric acid for 24 hours.

[0103] The product design part is the same as Example 1.

[0104] Example 4

[0105] The material formula and preparation process are the same as those in Example 1.

[0106] In the product design part, the parameter details different from Example 1 are as follows:

[0107] The one-piece implant has only one thread pattern for the entire length (10mm), a triangular thread with a pitch of 0.8mm. At the lower end of the implant (towards the jawbone), there are three grooves with a length of 4mm, which form an angle of 6 degrees with the axis of the implant. The inclination direction is the same as the thread direction (right direction), and the groove width is 2mm.

[0108] The above corresponding differences are summarized in Table 1.

[0109] Table 1

[0110]

[0111]

[0112]

[0113] Test Example 1

[0114] The comparative example and embodiments 1, 2, 3 and 4 were tested for performance.

[0115] The density test shall be carried out in accordance with GB / T 25995-2010 Test method for density and apparent porosity of fine ceramics.

[0116] The hardness test is carried out in accordance with GB / T 16534-2009 Fine Ceramics Room Temperature Hardness Test Method.

[0117] The compressive strength test is carried out in accordance with "GB / T 8489-2006 Fine Ceramics Compression Strength Test Method".

[0118] The fracture toughness test 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.

[0119] The performance test results are shown in Table 2.

[0120] Table 2

[0121]

[0122]

[0123] It can be seen from the above table that the silicon nitride ceramic integrated dental implants prepared in Examples 1-4 of the present invention have better comprehensive performance.

[0124] Test Example 2

[0125] The comparative example and embodiments 1, 2, 3 and 4 were tested for antibacterial properties.

[0126] Porphyromonas gingivalis (ATCC 33277), Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922) were inoculated on a nutrient agar medium slant at a ratio of 1:1:1, cultured at 37±1°C for 24 hours, and then stored at 0-5°C (not more than 1 month) as slant-preserved bacteria.

[0127] Transfer the slant-preserved bacteria to a plate of nutrient agar medium and culture at 37±1℃ for 24 hours, once a day for no more than 2 weeks. The test should use fresh bacterial cultures after two consecutive transfers (transferred within 24 hours).

[0128] Use an inoculation loop to take a small amount (scrape 1-2 loops) of fresh bacteria from the culture medium, add it to the culture medium, and make 10-fold incremental dilutions in sequence. Count the cells using a cell counting plate and select a bacterial solution with a concentration of 10.0×10 5 The dilution with cfu / ml was used as the bacterial solution for experimental detection.

[0129] Prepare 15 Φ90mm sterile plates, place 5-6 Φ90mm sterile filter papers on the bottom of the plates, and pour in an appropriate amount of sterile purified water to allow the filter papers to fully absorb water. It is best if no large amount of water precipitates when pressing the filter paper with sterile tweezers.

[0130] Take 15 sterile filter membranes with a size of Φ0.24μm×50mm, cover them on the sterile filter paper of each plate, and spread them flat. Take 0.2ml of the experimental bacterial solution and drop it on the sterile filter membrane with a size of Φ0.24μm×50mm.

[0131] Use sterile tweezers to pick up the negative control sample (A), blank control sample (B), and test sample (C). Prepare 5 parallel samples for each sample, cover them on a Φ0.24μm×50mm sterile filter membrane to make the bacterial solution evenly contact the sample, and culture them at 37±1℃ for 24h.

[0132] Take out the samples that have been cultured for 24 hours, add 20 ml of eluent respectively, wash sample A, sample B, sample C and the covering film repeatedly, and shake well. Use a sterile pipette tip to absorb 1 ml of the original eluent solution and transfer it to a sterile culture dish. Inject about 15 ml of nutrient agar medium into the culture dish and rotate the culture dish to mix evenly. Repeat the plate-laying operation twice to obtain 2 culture dishes with the original elution solution. Take another 1 ml of the original eluent solution and slowly inject it into a test tube containing 9 ml of sterile saline along the wall of the tube. The tip of the pipette tip does not touch the diluent in the tube. Shake the test tube to mix evenly to make a 1:10 elution dilution solution.

[0133] Take 1 ml of 1:10 elution diluent and transfer it to a sterile culture dish. Inject about 15 ml of nutrient agar medium into the culture dish and rotate the culture dish to mix evenly. Repeat the plate-laying operation twice to obtain two 1:10 elution diluent culture dishes. Take 1 ml of 1:10 elution diluent and slowly inject it into a test tube containing 9 ml of sterile physiological saline along the tube wall. The tip of the gun does not touch the diluent in the tube. Shake the test tube to mix evenly to make a 1:100 elution diluent.

[0134] Take 1 ml of 1:100 elution diluent and transfer it to a sterile culture dish. Inject about 15 ml of nutrient agar medium into the culture dish and rotate the culture dish to mix evenly. Repeat the plate-laying operation twice to obtain two 1:100 elution diluent culture dishes. Take 1 ml of 1:100 elution diluent and slowly inject it into a test tube containing 9 ml of sterile physiological saline along the tube wall. The tip of the gun does not touch the diluent in the tube. Shake the test tube to mix evenly to make a 1:1000 elution diluent.

[0135] Take 1 ml of 1:1000 elution dilution and transfer it to a sterile culture dish. Pour about 15 ml of nutrient agar medium into the culture dish and rotate the culture dish to mix evenly. Repeat the plating operation twice to obtain 2 1:1000 elution dilution culture dishes.

[0136] When counting the colonies on the plates, you can observe with your naked eyes, and use a magnifying glass if necessary to prevent omissions. After recording the number of colonies on each plate, calculate the average total number of colonies on each plate with the same dilution. Select plates with a colony count between 30 and 300 as the standard for determining the total number of colonies.

[0137] If two plates are used for one dilution, the average of the two plates should be used. If one of the plates has large flake colonies growing, it should not be used. Instead, the plate without flake colonies should be used as the colony count for that dilution. If the flake colonies are less than half of the plate, and the colonies in the remaining half are evenly distributed, half of the plate can be counted and multiplied by 2 to represent the colony count of the whole plate. If there are chain 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 a colony. A dilution with an average colony count between 30-300 should be selected and reported by multiplying it by the dilution multiple. If there are two dilutions, and the number of colonies grown is between 30-300, the decision will be based on the ratio between the two. 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 count of all dilutions is greater than 300, the average colony count of the highest dilution multiplied by the dilution multiple should be reported. If the average colony count of all dilutions is less than 30, the average colony count of the lowest dilution multiplied by the dilution factor should be reported. If no colonies grow at all dilutions, report as less than 1 multiplied by the lowest dilution factor. If the average colony count of all dilutions is not between 30 and 300, and some of them are greater than 300 or less than 30, report as the average colony count closest to 30 or 300 multiplied by the dilution factor.

[0138] When the colony count is less than 100, it shall be reported as the actual number. When it is greater than 100, two significant figures shall be used, and the value after the two significant figures shall be calculated by rounding off. The measured viable count result shall be multiplied by 100 to obtain the actual recovered viable count of sample A, sample B, and sample C after 24 hours of incubation, and the values ​​are A, B, and C respectively.

[0139] Ensure that the experimental results meet the following requirements, otherwise the test is invalid:

[0140] The five parallel viable bacteria values ​​of the same blank control sample B must meet the requirement of (highest logarithm value - lowest logarithm value) / average viable bacteria value logarithm value not greater than 0.3;

[0141] The actual recovered viable bacteria value A of sample A should not be less than 1.0×10 5 cfu / piece, and the actual recovered viable bacteria value B of sample B should not be less than 1.0×10 4 cfu / piece.

[0142] The antibacterial rate is calculated according to the following formula:

[0143] R(%)=(BC) / B×100

[0144] Where:

[0145] R——antibacterial rate, %;

[0146] B——Average number of recovered bacteria in blank control samples, cfu / piece;

[0147] C——Average number of recovered bacteria in antibacterial samples, cfu / tablet.

[0148] The antibacterial performance test results are shown in Table 3.

[0149] Table 3

[0150]

[0151]

[0152] It can be seen from the above table that the silicon nitride ceramic integrated dental implants prepared in Examples 1-4 of the present invention have excellent antibacterial properties.

[0153] Test Example 3

[0154] The comparative example and embodiments 1, 2, 3 and 4 were tested for bone integration performance.

[0155] Prepare cylindrical sample rods of the comparative example and the embodiment with a diameter of 2 mm and a height of 6 mm. According to the requirements of "GB / T16886.6-2022 Biological Evaluation of Medical Devices Part 6: Local Reaction Test after Implantation", the sample rods were implanted into the femur of New Zealand white rabbits through a bone drill, and the fascia and skin incisions were sutured with medical sutures. Antibiotics were used for anti-inflammatory treatment for three days after surgery. The animals were euthanized 4 weeks after implantation, the implantation site was observed with the naked eye, and sufficient unaffected tissue including the implanted sample rod and the surrounding area was cut and fixed in a 10% formaldehyde solution for not less than 48 hours. After fixation, the tissue including the implantation point was dehydrated, decalcified, embedded, and HE stained for pathological analysis. The stained tissue slices were placed under an optical microscope to observe the tissue reaction around the implantation site. The degree of tissue reaction was determined based on the measurement of the distance from the implant / tissue interface to the unaffected area with normal tissue and vascular characteristics, including the thickness of the fibrous cystic cavity, the number and type of inflammatory cells, and other abnormalities at the implanted sample rod-tissue interface.

[0156] In the comparative example, a small amount of proliferating fibroblasts were observed around the implants to undergo fibrosis and form fibrous callus. In Examples 1-4, there was no abnormal tissue reaction around the implants, the implants were tightly combined with the bone tissue, the bone cells began to proliferate, trabeculae were visible, and the new bone developed well. It can be seen that the silicon nitride ceramic integrated dental implants prepared in Examples 1-4 of the present invention have excellent performance in promoting bone integration.

[0157] Test Example 4

[0158] The comparative example and embodiments 1, 2, 3 and 4 were tested for radiological artifacts.

[0159] The radiologist determined the difference based on the CT scan taken before the animal was euthanized in the above-mentioned bone implantation test. The comparative example had radiological artifacts, while Examples 1-4 had no radiological artifacts. It can be seen that the silicon nitride ceramic integrated dental implants prepared in Examples 1-4 of the present invention have excellent imaging performance and will not produce radiological artifacts.

[0160] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant, characterized in that: The one-piece dental implant includes a first region, a second region, a third region and a base part. The first region, the second region and the third region together constitute the implant part. The above-mentioned implant part and the base part are prepared as a whole in one piece without assembly connection, forming the one-piece dental implant. The material used for the dental implant is silicon nitride ceramic with an irregular rough porous surface designed with a gradient distribution.

2. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 1, characterized in that: The porous silicon nitride ceramic is prepared from the following raw materials in parts by weight: 60-90 parts of silicon nitride and 10-40 parts of additives, wherein the additives include a binder, a dispersant, a lubricant, a sintering aid and other performance aids.

3. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 2, characterized in that: The binder is selected from at least one of high-density polyethylene, ethylene-vinyl acetate copolymer, polystyrene, random polypropylene, polyethylene glycol, and phenolic resin; the dispersant is selected from at least one of calcium stearate, triethyl phosphate, polyacrylic acid, castor oil, polyvinyl pyrrolidone, C12 alkyl polysaccharide quaternary ammonium salt, tetramethyl ammonium hydroxide, and sodium hexametaphosphate; the lubricant is selected from at least one of microcrystalline wax, stearic acid, and dibutyl phthalate; the sintering aid is selected from at least one of The agent is selected from at least two of aluminum oxide, zirconium oxide, yttrium oxide, ytterbium oxide, magnesium oxide, lanthanum oxide, neodymium oxide, strontium oxide, cerium oxide, erbium oxide, thulium oxide, and lutetium oxide; the other performance additives are selected from at least four of zinc oxide, copper oxide, chromium oxide, titanium oxide, titanium carbide, silicon carbide, titanium nitride, boron nitride, ytterbium fluoride, magnesium fluoride, ytterbium dihydride, ammonium carbonate, ammonium chloride, charcoal, sawdust, starch, chitosan, bioglass, fluoroapatite, and hydroxyapatite.

4. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 1, characterized in that: The dental implant is a conical cylinder with an integrated base and three sections of external threads of different styles. The outer diameter of the cylindrical part is D, and the overall length of the implant is L. The lengths of the first area, the second area, and the third area in the integrated dental implant are L1, L2, and L3, respectively. L4 is the height of the base part. The cone angle of the lower cone part of the dental implant is α, the range of D is 3.0-7.0 mm, the range of L is 6.0-20 mm, the range of L1 is 35-40% L, the range of L2 is 40-45% L, the range of L3 is 15-25% L, the range of L4 is 3-6 mm, the range of α is 10-15°, and the variable range of the axis of the base part is within a cone with a cone angle of 60 degrees and the center of the gingival horizontal plane of the dental implant as the vertex.

5. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 4, characterized in that: The lower end of the dental implant, the first area, is a conical external thread, the thread profile is a sawtooth thread, the top arc radius is 0.1-0.2mm, the bottom transition arc radius is 0.4-0.5mm, the pitch is 0.6-1.0mm, and the thread depth is 0.6-1.0mm; the middle section of the dental implant, the second area, is a cylindrical external thread, the thread profile is a trapezoidal thread, the top width is 0.2-0.4mm, the bottom transition arc radius is 0.4-0.5mm, the pitch is 0.6-1.0mm, and the thread depth is 0.2-1.0mm; the upper end of the dental implant, the third area, is a cylindrical external thread, the thread profile is a triangular thread, the top arc radius is 0.1-0.2mm, the bottom transition arc radius is 0.4-0.5mm, the pitch is 0.2-0.4mm, and the thread depth is 0.02-0.5mm.

6. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 4, characterized in that: At the lower end of the dental implant, the conical external thread part in the first area is provided with 2-4 grooves, the angle formed between the groove and the implant axis is half of the cone angle α, the inclination direction is the same as the thread direction, and the groove width is 1-3 mm.

7. The antibacterial, anti-fracture, and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to claim 4, characterized in that: The surface of the dental implant implanted in the jawbone is irregularly rough and porous, and the porosity is distributed in a gradient from less to more from the inner core to the outer surface of the implant. The thickness of the porous layer is 600-900 μm, the pore size range is 60-600 μm, the average pore size is controlled at 250-300 μm, and the porosity is 35-75%.

8. A method for preparing the antibacterial, anti-fracture and bone-integration-promoting porous silicon nitride ceramic integrated dental implant according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Weighing ratio: According to the formula ratio of claim 2 or 3, accurately weigh silicon nitride and sintering aid; S2. Mixed ball milling: Mix the above-mentioned raw materials after weighing and proportioning, and vacuum ball mill them in ethanol solvent; S3. Spray granulation: The ball-milled slurry is introduced into a pressure spray granulator, and the spray-dried powder is classified by a vibrating screen separator to obtain a granulated powder having an average diameter of less than 0.9 microns; S4. Feed preparation: According to the formula ratio of claim 2 or 3, accurately weigh the granulated powder and binder, dispersant and lubricant obtained above, vacuum mix and knead, obtain feed A for standby, on the basis of feed A, mix with other performance additives in appropriate amounts, according to the above preparation process, obtain feed B for standby; S5. Injection molding: Feed A is heated to be converted into a viscous melt, and the melt is injected into a preheated mold. Feed A is injected at a first speed, and then feed B is injected at a second speed. The mold cavity designed according to the requirements of the final product is injected in stages, so that the core inside the cavity is mainly feed A, and the surface layer is mainly feed B. The melt is gradually cooled and solidified to form a green blank of the shape required by the final product; S6. Laser etching: implant the front end of the blank into the surface of the jawbone, namely the first area, the second area, and the third area, and significantly increase the surface roughness by laser etching; S7. Degreasing and biscuit firing: The laser-etched biscuit is placed in a degreasing furnace and degreased and biscuit fired in stages under the protection of an inert gas; S8. Preparatory sintering: The degreased biscuit is placed in a sintering furnace and preparatory sintering is performed in stages under the protection of an inert gas to obtain a blank; S9. Formal sintering: The obtained blank is formally sintered in stages under nitrogen pressure protection to obtain a semi-finished product; S10. Subsequent treatment: The semi-finished product is placed in a hydrofluoric acid, hydrogen peroxide aqueous solution or a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide to react, so that the roughness of the irregular porous surface with a gradient distribution of the fired semi-finished product is further improved, and then the semi-finished product is placed and ultrasonically cleaned to obtain a finished product.

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