A dental pulp chamber retention crown surface composite coating and a preparation method thereof

Abstract

The application discloses a dental pulp cavity retention crown surface composite coating and a preparation method, and belongs to the technical field of pulp cavity retention crowns. The dental pulp cavity retention crown surface composite coating is characterized by comprising the following components in parts by weight: a moisture curing layer, an intermediate layer and a mineralized polypeptide layer. The moisture curing layer comprises the following components: 75 parts of polyurethane prepolymer, 12-24 parts of modified nano-hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 parts of stannous octoate and 0.6 parts of fumed silica. The composite coating guarantees that the pulp cavity retention crown with root canal extension retention can realize high-strength bonding in the deep part of the root canal, avoids the stability of the bonding interface of the retention crown in long-term use through a multiple defense mechanism, effectively guarantees the persistence of the bonding effect, and can maintain effective retention for a longer time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pulp cavity retention crown, in particular, relates to a dental pulp cavity retention crown surface composite coating and a preparation method. BACKGROUND

[0002] In recent years, the pulp cavity retention crown has attracted attention due to its small tooth preparation amount and good anti-fracture performance. The pulp cavity retention crown uses the docking type embedding of the restoration and the pulp cavity to obtain macroscopic retention, and uses the dentin bonding of the pulp chamber wall to achieve microscopic retention, thereby reducing the risk of root fracture to a certain extent. However, in the case of extensive tooth defect such as four-wall defect or extremely short residual crown, especially in the molar area which bears a large biting force, the pulp cavity retention crown with root canal extension retention can provide more stability compared to the pulp cavity retention crown which only relies on the pulp chamber retention.

[0003] The common bonding method of the current pulp cavity retention crown is to clean and dry the bonding interface, uniformly coat self-adhesive resin cement on the inner surface of the restoration, accurately position the restoration on the four-wall defect model, apply load, and squeeze out the excess adhesive. After the cement is preliminarily solidified, the excess part is cleaned, and an LED light curing lamp is used for irradiation.

[0004] The above existing technology has the following problems for the pulp cavity retention crown with root canal extension retention: The root canal extension section of the pulp cavity retention crown with root canal extension retention reaches 1-3 mm or even deeper, and has a narrow tubular structure. The light intensity of the conventional LED light curing lamp decreases exponentially with the depth of the root canal, and the light energy reaching the bottom of the root canal is almost zero. The dual-curing cement located in the deep root canal cannot be effectively light cured and can only rely on its slow chemical curing.

[0005] The final degree of polymerization and mechanical strength achieved by chemical curing are much lower than those of the part fully light cured, which directly leads to a serious lack of bonding strength of the root canal retention section of the pulp cavity retention crown with root canal extension retention, thereby violating the original intention of designing root canal extension to increase retention stability on the pulp cavity retention crown. Moreover, the viscous cement is coated on the pulp cavity retention crown and then inserted into the narrow root canal. When the crown is in place and pressure is applied, the hydrodynamic effect of the adhesive will cause it to be excessively squeezed out at the pulp bottom and flat wall surface, while at the narrow end of the post channel, it cannot be completely filled due to viscosity and surface tension, and is prone to stagnation and the formation of microbubbles, resulting in interface gaps which become stress concentration points.

[0006] The combination of the above incomplete polymerization and interface gaps may create conditions for bacterial invasion and proliferation, which can easily cause secondary caries and root canal infection. In addition, it also needs to be able to resist hydrolysis and bacterial erosion in the oral environment for a long time, and provide good buffering between the titanium alloy pulp cavity retention crown and dentin.

[0007] Therefore, in order to solve the above technical problems, the present application provides a dental pulp cavity retention crown surface composite coating and a preparation method to solve the above technical problems. SUMMARY

[0008] In order to solve the defects in the above technical solutions, the present application provides a dental pulp cavity retention crown surface composite coating and a preparation method, and a dental pulp cavity retention crown surface composite coating, which comprises: a moisture curing layer, an intermediate layer, and a mineralized polypeptide layer.

[0009] The moisture curing layer comprises, by weight fraction: 75 parts of polyurethane prepolymer, 12-24 parts of modified nano-hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 parts of stannous octoate, and 0.6 parts of fumed silica.

[0010] The intermediate layer comprises 1.0 wt% of N-(3,4-dihydroxyphenethyl) methacrylamide solution.

[0011] The mineralized polypeptide layer comprises 120-200 mg / 100 mL of polypeptide MPP3 solution.

[0012] The preparation method of the polypeptide MPP3 solution is as follows: taking mineralized polypeptide MPP3, dissolving it in deionized water to obtain a polypeptide MPP3 solution for standby use.

[0013] The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA.

[0014] The intermediate layer is obtained by brush coating the N-(3,4-dihydroxyphenethyl) methacrylamide solution.

[0015] The preparation method of the polyurethane prepolymer is as follows: in a reaction container, 1 mol of polycaprolactone diol is added; under the condition of continuous dry nitrogen gas and vacuum, the reactor is heated to 110-120°C, and stirred vigorously at this temperature for 2-3 hours;

[0016] Then stop the vacuum, and under the protection of continuous nitrogen positive pressure, the temperature of the reactor is reduced to 70-80°C; through a dropping funnel, 2 mol of hexamethylene diisocyanate is slowly added dropwise within 30 minutes under vigorous stirring; the molar ratio of -NCO groups to -OH groups is controlled to be 2:1;

[0017] After the addition is completed, 0.05% of stannous octoate catalyst relative to the total mass of the feed is added; the reaction mixture is incubated at 80-85°C for 3-5 hours;

[0018] During the reaction, samples are taken every 30 minutes, and the percentage content of free -NCO groups in the system is accurately determined by standard di-n-butylamine chemical titration method,

[0019] When the measured percentage value of -NCO group content decreases and stabilizes, it is determined that the polymerization reaction is complete, heating is stopped, and the temperature is lowered to room temperature under continuous nitrogen protection, thereby obtaining the polyurethane prepolymer.

[0020] The number average molecular weight Mn of the polycaprolactone diol is 2000 g / mol.

[0021] The measured percentage value of -NCO group content in the preparation process is 3.58% in the present formulation.

[0022] The preparation method of the modified nano-hydroxyapatite is as follows: the nano-hydroxyapatite powder is dried in a clean oven at 120°C for 4 hours; then a 95:5 (v / v) ethanol / water mixed solution is prepared in a clean beaker; using glacial acetic acid as a catalyst, the pH value of the mixed solution is adjusted to 4.5-5.5, and then 3-methacryloyloxypropyl triethoxysilane is added; the mixture is stirred at room temperature for 1 hour under magnetic stirring;

[0023] The dried nano-hydroxyapatite powder is added to anhydrous ethanol in a reaction container; the mixture is ultrasonically treated for 30 minutes to form a uniform, milky white suspension without obvious precipitation; under continuous ultrasonic treatment, the hydrolysis solution of activated 3-methacryloyloxypropyl triethoxysilane is added dropwise into the suspension through a constant-pressure dropping funnel; after the addition is completed, the temperature of the reaction system is raised to 60-70°C, and the reaction is carried out under reflux at this temperature for 4-6 hours; after the reaction is completed, the suspension is cooled to room temperature; the reaction solution is subjected to centrifugal treatment using a high-speed centrifuge; the supernatant is discarded, and the white precipitate obtained by centrifugation is redispersed with an excess of anhydrous ethanol, and then centrifuged again to remove impurities; preferably, the washed product is placed in a vacuum oven and dried to constant weight, thereby obtaining the modified nano-hydroxyapatite.

[0024] The final white loose powder is the 3-methacryloyloxypropyl triethoxysilane-modified nano-hydroxyapatite. The finished product needs to be sealed and stored in a desiccator to prevent moisture absorption.

[0025] A preparation method of a dental pulp cavity retention crown surface composite coating, the preparation method comprising a preparation method of a moisture-cured layer, a preparation method of an intermediate layer, and a preparation method of a mineralized polypeptide layer;

[0026] The preparation method of the moisture-cured layer is as follows: polyurethane prepolymer, modified nano-hydroxyapatite, p-toluenesulfonyl isocyanate, stannous octoate, and fumed silica are added to a vacuum planetary mixer and fully blended, thereby obtaining the moisture-cured layer.

[0027] The moisture-cured layer needs to be strictly stored in anhydrous and nitrogen-filled conditions.

[0028] The preparation method of the intermediate layer is that N-(3,4-dihydroxyphenethyl) methacrylamide is dissolved in a mixed solvent composed of ethanol and water to obtain an N-(3,4-dihydroxyphenethyl) methacrylamide solution.

[0029] The preparation method of the mineralized polypeptide layer is that the mineralized polypeptide MPP3 is dissolved in deionized water to obtain a polypeptide MPP3 solution.

[0030] The application method of the dental pulp cavity retention crown surface composite coating is as follows: after root canal treatment is completed, the extension section of the retention crown is prepared to have a root canal upper section depth of 1-3 mm, so that the shape is matched with the restoration; then, 37% phosphoric acid gel is used to selectively etch the pulp cavity wall and the root canal inner wall for 15 seconds; the phosphoric acid gel is thoroughly washed with water, and then the excess clear water in the dental cavity is absorbed with a cotton ball or a suction device, but the dentin surface is kept wet; then, a micro-brush is used to dip the polypeptide MPP3 solution, and the polypeptide MPP3 solution is gently applied to all the dentin surfaces that need to be bonded in the pulp cavity and the root canal, and the wetting effect is kept for 1-2 minutes.

[0031] The mineralized ionic liquid is injected into the pulp cavity and the root canal to ensure that all the surfaces previously coated are completely covered; then, the residual mineralized ionic liquid in the cavity is gently washed away with a water gun; the clear water is removed by blowing with an air gun for 2-3 seconds, and the dentin is kept wet; then, a micro-brush is used to dip the N-(3,4-dihydroxyphenethyl) methacrylamide solution, and the N-(3,4-dihydroxyphenethyl) methacrylamide solution is uniformly applied to the dentin surface just treated by mineralization, and after being kept for 30 seconds, the cavity surface is gently blown with a warm and oil-free air flow for about 5-10 seconds.

[0032] Then, the moisture curing coating is uniformly applied to the inner surface of the titanium alloy pulp cavity retention crown and the root canal extension section, and then the pulp cavity retention crown with the coating applied is slowly and stably positioned on the tooth to ensure that the root canal extension section is completely inserted into the root canal; a gentle and continuous pressure is applied to completely position the restoration and squeeze out the excess moisture curing coating at the edge; the excess material overflowing at the edge of the crown is carefully removed with a small cotton ball or a micro-brush, and the pressure or occlusion is continuously applied for 10-15 minutes to complete the preliminary curing with the help of the moisture in the dentin surface and saliva.

[0033] Further, the mineralized ionic liquid is 0.5 g of calcium chloride and 0.6 g of anhydrous disodium hydrogen phosphate dissolved in 100 ml of Tris-HCl buffer.

[0034] The composite coating of the present application creatively screens and combines a mineralized polypeptide layer with mechanical locking effect, an intermediate layer with long-term chemical adhesion and anti-enzymatic effect as an interface pretreatment, and optimizes the optimal process parameters of the synergistic effect of the two, so that the formed biological integration interface can provide a high stability and high affinity substrate for the bonding of the subsequent moisture curing layer.

[0035] The present application screens a moisture curing polyurethane prepolymer with flexible stress buffering characteristics as the main layer matrix, and matches a surface modified nano-hydroxyapatite with mechanical reinforcement effect as a functional filler, so that the moisture curing layer can be completely and uniformly cured in the deep root canal humid environment without light, and the flexible layer after curing can effectively absorb and dissipate occlusal stress to protect fragile dental tissues, and is particularly suitable for pulp cavity retention crown with root canal extension retention; and the physiological moisture continuously micro-leaked from the living dentin tubules ensures that the curing reaction will definitely achieve complete polymerization at the bonding interface;

[0036] The composite coating of the present application ensures that the pulp cavity retention crown with root canal extension retention achieves high-strength bonding in the deep root canal, and avoids the stability of the bonding interface of the retention crown in long-term use through multiple defense mechanisms, effectively ensures the durability of the bonding effect, and can maintain effective retention for a longer period of time. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a structural diagram of the pulp cavity retention crown with root canal extension retention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with examples, and the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and are not as a limitation of the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the range and any other stated value or intermediate value in the range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification will control.

[0040] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0041] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or step.

[0042] The "parts" indicated in the following examples are all weight parts.

[0043] A dental pulp cavity retention crown surface composite coating, comprising: a moisture curing layer, an intermediate layer, and a mineralized polypeptide layer.

[0044] The moisture curing layer comprises, by weight fraction: 75 parts of polyurethane prepolymer, 12-24 parts of modified nano-hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 parts of stannous octoate, and 0.6 parts of fumed silica.

[0045] The preparation method of the moisture curing layer is as follows: the polyurethane prepolymer, the modified nano-hydroxyapatite, the p-toluenesulfonyl isocyanate, the stannous octoate, and the fumed silica are added into a vacuum planetary mixer and fully blended to obtain the moisture curing layer.

[0046] The moisture curing layer needs to be strictly stored under the conditions of no water and nitrogen filling.

[0047] The intermediate layer comprises 1.0 wt% of N-(3,4-dihydroxyphenethyl) methacrylamide solution.

[0048] The mineralized polypeptide layer comprises 120-200 mg / 100 mL of polypeptide MPP3 solution.

[0049] The preparation method of the polypeptide MPP3 solution is as follows: the mineralized polypeptide MPP3 is dissolved in deionized water to obtain the polypeptide MPP3 solution for standby.

[0050] The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA.

[0051] The preparation method of the N-(3,4-dihydroxyphenethyl) methacrylamide solution in the intermediate layer is as follows: 1.0 g of N-(3,4-dihydroxyphenethyl) methacrylamide is dissolved in a mixed solvent composed of 70 g of ethanol and 30 g of water to obtain the N-(3,4-dihydroxyphenethyl) methacrylamide solution with a mass fraction of 1.0 wt%.

[0052] The method for preparing the polyurethane prepolymer is as follows: in a clean and dry four-neck flask reactor equipped with a mechanical stirrer, a thermometer, a dropping funnel and a nitrogen protection device, 1 mol of polycaprolactone diol with a number average molecular weight Mn = 2000 g / mol is added; under the condition of continuously passing dry nitrogen and vacuumizing, the reactor is heated to 110-120°C, and is stirred vigorously at this temperature for 2-3 hours; then the vacuum is stopped, and the temperature of the reactor is reduced to 70-80°C under the protection of continuous nitrogen positive pressure; 2 mol of hexamethylene diisocyanate is slowly and dropwisely added through the dropping funnel under vigorous stirring within 30 minutes; the molar ratio of -NCO groups to -OH groups is controlled to be 2:1; after the dropwise addition is completed, 0.05% of stannous octoate relative to the total mass of the feed is added; and the reaction mixture is incubated at 80-85°C for 3-5 hours.

[0053] During the reaction, sampling is performed once every 30 minutes, and the content percentage of free -NCO groups in the system is accurately determined by using a standard di-n-butylamine chemical titration method; when the content percentage of -NCO groups is reduced and stabilized at 3.58%, it is determined that the polymerization reaction is complete, heating is stopped, and the temperature is reduced to room temperature under the protection of continuous nitrogen, thereby obtaining the polyurethane prepolymer.

[0054] The method for preparing the modified nanohydroxyapatite is as follows: 100 g of nanohydroxyapatite powder is dried in a clean oven at 120°C for 4 hours to remove the adsorbed water on the surface of the particles and activate the hydroxyl sites on the surface; then a 95:5 (v / v) ethanol / water mixed solution is prepared in a clean beaker; after the pH value of the mixed solution is adjusted to 4.5-5.5 using glacial acetic acid as a catalyst, 2 g of 3-methacryloyloxypropyl triethoxysilane is added; and the mixture is stirred magnetically at room temperature for 1 hour.

[0055] In a new reaction container, the dried nanohydroxyapatite powder is added to anhydrous ethanol; ultrasonic treatment is performed for 30 minutes to form a uniform, milky white suspension without obvious precipitation; under the condition of maintaining the nanohydroxyapatite powder in a good dispersed state under continuous ultrasonic treatment; the hydrolyzate of the activated 3-methacryloyloxypropyl triethoxysilane is slowly and uniformly dropwisely added to the suspension through a constant pressure dropping funnel; after the dropwise addition is completed, the temperature of the reaction system is increased to 60-70°C, and reflux reaction is performed at this temperature for 4-6 hours.

[0056] After the reaction is completed, the suspension is cooled to room temperature, and the reaction solution is centrifuged using a high-speed centrifuge; the supernatant is discarded, and the white precipitate obtained by centrifugation is redispersed with an excess of anhydrous ethanol, and then centrifuged again to remove unreacted silane coupling agent and other impurities; finally, the washed product is placed in a vacuum oven and dried at 80°C for 12 hours until the weight is constant, thereby obtaining modified nano-hydroxyapatite.

[0057] The white loose powder obtained is 3-methacryloyloxypropyl triethoxysilane modified nano-hydroxyapatite; the finished product needs to be sealed and stored in a desiccator to prevent moisture absorption.

[0058] The nano-hydroxyapatite is needle-shaped or rod-shaped, with a length of 50-100 nm and a diameter of 10-20 nm.

[0059] The fumed silica has a particle size of 12 nm.

[0060] Specifically, the preparation method of the comparative example is the same as that of the example except that the specific component formula is different from that of the example.

[0061] Table 1: Component formula of the composite coating of Examples 1-9;

[0062]

[0063] Test Example

[0064] Coating bonding strength test: select a single tooth of a cow and cut off the crown, expand the root canal file to 1.3 mm, slice to 2 mm thick, acid etch the dentin for 15 seconds, complete the coating of the composite coating, and insert a titanium alloy post core. After sufficient curing at 37°C and >95% RH, store in distilled water at 37°C for 24 hours, complete the coating bonding strength test, use an Instron testing machine to push out at 0.5-1 mm / min, and calculate the bonding strength.

[0065] Coating sealing performance test: after preparing a class I cavity of a cow molar, expanding the root canal file to 1.3 mm, and acid etching, coating the composite coating, and fully curing, place it in a thermal cycle of 5-55°C for 1000 cycles, then store it in water at 37°C for 48 hours, seal the non-test area with nail polish; immerse in 2% methylene blue at 37°C for 24 hours, then slice longitudinally to 1.0 mm, and measure the penetration depth using a microscope.

[0066] Coating hydrolysis resistance test: use a Teflon mold to prepare a disc-shaped coating sample with a diameter of 15 mm and a thickness of 1 mm, then cure at 37°C and >95% RH; after drying to constant weight, weigh m1, immerse in water for 7 days, weigh m2, and then dry to constant weight, weigh m3.

[0067] The water absorption rate is calculated as (m2-m3) / V; the solubility is calculated as (m1-m3) / V.

[0068] Coating cushion performance test: 25x2x2mm beam-shaped coating samples are prepared using a stainless steel mold, cured at 37℃, >95%RH; using an Instron testing machine, set to a span of 20mm, speed 0.5-1mm / min, measure the elastic modulus of the coating.

[0069] Test example sample preparation:

[0070] The composite coating is coated by using a micro-brush to dip the polypeptide MPP3 solution and gently apply it to all the acid-etched dentin surfaces, ensuring complete coverage, and keeping it moist for 1-2 minutes.

[0071] Mineralized ionic solution is coated onto the dentin surface and left to stand for 10 minutes; the mineralized ionic solution is 0.5g of calcium chloride and 0.6g of anhydrous disodium hydrogen phosphate dissolved in 100ml of Tris-HCl buffer.

[0072] Gently rinse off the remaining mineralized ionic solution, then lightly blow with an oil-free air gun for 2-3 seconds to remove only the water, and again keep the dentin moist;

[0073] Dip a new micro-brush in the N-(3,4-dihydroxyphenethyl) methacrylamide solution and evenly apply it to the mineralized dentin surface, and let it stand for 30 seconds;

[0074] Finally, evenly apply the moisture-cured coating to the surface of the titanium alloy post core, then slowly and steadily insert the post core into the dentin slice;

[0075] During the coating hydrolysis resistance and cushion performance test, the moisture-cured coating is directly injected into the Teflon and stainless steel mold for preparation.

[0076] The structure of the pulp cavity retention crown with intracanal extension retention is shown in Figure 1 .

[0077] Table 2 Performance test results of Examples 1-9

[0078]

[0079] As can be seen from the above table: according to conventional technical ideas in the art, increasing the content of reinforcing fillers modified nano-hydroxyapatite can monotonously improve the mechanical properties of the material.

[0080] However, as can be seen from the performance test results in Table 2, the reinforcing fillers in Example 1, Example 3, and Example 5 are gradually increased, but the elastic modulus and the bonding strength are not simply positively correlated,

[0081] When the content of modified nano-hydroxyapatite is increased from 18 parts to 24 parts, the elastic modulus is expected to rise to 6.2 GPa, but the bonding strength unexpectedly drops from 16.5 MPa to 11.5 MPa, which shows that the too hard coating destroys the stress buffering mechanism designed for high modulus titanium post, leading to interface failure and poor performance. Although the elastic modulus is expected to rise, the bonding strength shows this nonlinear and counterintuitive technical effect, which cannot be predicted by simple motivation combination or conventional knowledge of those skilled in the art, and must be discovered through the creative labor of the inventor.

[0082] Table 3: Composition of Comparative Example 1-Comparative Example 8;

[0083]

[0084] The modified nano-hydroxyapatite in Comparative Example 8 is unmodified nano-hydroxyapatite.

[0085] Table 4: Performance test results of Comparative Example 1-Comparative Example 8;

[0086]

[0087] As can be seen from the above table: for the concentration of polypeptide MPP3, the concentration below 120 mg / 100 mL or above 200 mg / 100 mL will cause the bonding performance to deteriorate sharply; and the concentration deviating from 160 mg / 100 mL on both sides will also cause the bonding performance to deteriorate sharply, rather than a gradual performance decline.

[0088] And based on the fact that Comparative Example 5 lacks the effective components of the intermediate layer, Comparative Example 6 lacks the effective components of the mineralized polypeptide layer, and Comparative Example 7 lacks modified nano-hydroxyapatite in the moisture curing layer; the above performance test results show that it is not a simple linear superposition of performance loss; such as the significant decline in bonding strength in Comparative Example 5, which proves that there is a significant synergistic enhancement effect between the physical anchoring between the mineralized polypeptide layer and the intermediate layer.

[0089] Comparative Example 8 uses unmodified nano-hydroxyapatite, and the performance gap it presents also shows that the modification of nano-hydroxyapatite greatly affects the formation of the cross-linked network structure of the moisture curing layer and affects the overall stress distribution of the coating.

[0090] The presented interaction between the coatings is the result of the inventors' creative efforts to successfully integrate the three seemingly independent technical points into an efficient synergistic system, which cannot be foreseen by simply combining them, and the numerical ranges are not conventional choices but are obtained by the inventors' deep understanding of the complex antagonistic relationship between mineralization kinetics and resin penetration and creative experiments.

[0091] Example 11

[0092] The ratio is according to Example 3, except that the mineralized ionic liquid in the preparation process of the composite coating is different.

[0093] The mineralized ionic liquid in Example 11 is 0.25 g of calcium chloride and 0.2 g of anhydrous disodium hydrogen phosphate dissolved in 100 ml of Tris-HCl buffer solution;

[0094] The pH of the Tris-HCl buffer solution is 7.4.

[0095] Example 12

[0096] The ratio is according to Example 3, except that the mineralized ionic liquid in the preparation process of the composite coating is different.

[0097] The mineralized ionic liquid in Example 11 is 0.25 g of calcium chloride and 0.2 g of anhydrous disodium hydrogen phosphate dissolved in 100 ml of Tris-HCl buffer solution;

[0098] The pH of the Tris-HCl buffer solution is 7.4.

[0099] Comparative Example 9

[0100] The ratio is according to Example 3, except that the mineralized ionic liquid in the preparation process of the composite coating is different.

[0101] The mineralized ionic liquid in Comparative Example 9 is pure Tris-HCl buffer solution without dissolving any calcium chloride and anhydrous disodium hydrogen phosphate;

[0102] The pH of the Tris-HCl buffer solution is 7.4.

[0103] Comparative Example 10

[0104] The ratio is according to Example 3, except that the mineralized ionic liquid in the preparation process of the composite coating is different.

[0105] The mineralized ionic liquid in Comparative Example 10 is a traditional SBF simulated body fluid.

[0106] Comparative Example 11

[0107] The ratio is according to the preparation of Example 3, the difference is that the mineralization ionic liquid in the preparation process of the composite coating is different.

[0108] The mineralization ionic liquid of the comparative example 11 is that 0.5g of calcium acetate and 0.6g of anhydrous disodium hydrogen phosphate are dissolved in 100ml of Tris-HCl buffer solution; the calcium chloride is replaced by calcium acetate;

[0109] The pH of the Tris-HCl buffer solution is 7.4.

[0110] Comparative example 12

[0111] The ratio is according to the preparation of Example 3, the difference is that the mineralization ionic liquid in the preparation process of the composite coating is different.

[0112] The mineralization ionic liquid of the comparative example 12 is that 0.5g of calcium chloride and 0.6g of potassium dihydrogen phosphate are dissolved in 100ml of Tris-HCl buffer solution; the anhydrous disodium hydrogen phosphate is replaced by potassium dihydrogen phosphate;

[0113] The pH of the Tris-HCl buffer solution is 7.4.

[0114] Comparative example 13

[0115] According to the performance test in the test example, the curing of the comparative example 13 is carried out by light curing using self-adhesive resin cement, model: 3M ESPE RelyX™ U200 Automix, 3M Deutschland GmbH, Germany.

[0116] Table 5 performance test results of Examples 11-12 and Comparative Examples 9-13;

[0117]

[0118] From the above table, it can be seen that on the basis of determining the optimal coating formula, the inventors further creatively optimize and screen the key steps in the application process, the mineralization ionic liquid. The existing technology, such as the simulated SBF mineralization used in Comparative Example 10, has the problem of too slow mineralization speed, which cannot meet the operation requirements in clinical application.

[0119] Through creative labor, the inventors found that the specific coating system of the application, especially the surface containing the polypeptide MPP3 and the modified nano-hydroxyapatite, can realize mineralization in a shorter working time when combined with the specific concentration of the binary ionic liquid. The change of the concentration of the mineralization ionic liquid also obviously leads to the change of the performance of the coating, which shows that the coating formula and the mineralization process in the application example produce an unpredictable synergistic effect.

[0120] Comparative Example 11 and Comparative Example 12 respectively use calcium acetate to replace calcium chloride, and potassium dihydrogen phosphate to replace anhydrous disodium hydrogen phosphate; it is shown that the mixture of simple calcium salt and phosphate cannot of course achieve the mineralization reaction desired in the coating layer in the examples.

[0121] Comparative Example 13 is a prior art which, although exhibiting good comprehensive performance, has a bonding strength and elastic modulus reaching a higher level of prior art, enabling it to provide reliable immediate retention force in conventional crown-bridge bonding. However, in the face of titanium alloy with extremely high modulus and dentin with a relatively high amount, it cannot play a stress buffering effect, and the huge impact stress generated during occlusion is almost transmitted to the fragile bonding interface and root structure without attenuation, which can easily lead to fatigue failure and root fracture risk during long-term use, especially in the face of titanium alloy pulp cavity retention crown with root canal extension retention.

[0122] And the prior art of Comparative Example 13; its optimal mechanical properties are highly dependent on sufficient light initiation, and in the narrow root canal bottom where light cannot reach, its curing can only rely on relatively slow and insufficient chemical curing; this will result in problems such as insufficient degree of polymerization, low mechanical strength, and ineffective control of shrinkage stress in the bonding layer at the deepest part of the root canal, and this may also be the reason for the higher penetration depth of Comparative Example 13.

[0123] The above specific embodiments further detail the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A composite coating on the surface of a dental pulp chamber retention crown, characterized in that, include: Moisture-curing layer, intermediate layer, mineralized polypeptide layer; The moisture-curing layer, by weight, comprises: 75 parts of polyurethane prepolymer, 12-24 parts of modified nano-hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 parts of stannous octoate, and 0.6 parts of fumed silica. The intermediate layer comprises: a 1.0 wt% solution of N-(3,4-dihydroxyphenylethyl)methacrylamide; The mineralized polypeptide layer comprises: a polypeptide MPP3 solution of 120-200 mg / 100 mL; The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA; The modified nano-hydroxyapatite is 3-methacryloyloxypropyltriethoxysilane modified nano-hydroxyapatite.

2. The composite coating on the surface of a dental pulp chamber retention crown according to claim 1, characterized in that, The moisture-cured layer, by weight, comprises: 75 parts of polyurethane prepolymer, 18 parts of modified nano-hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 parts of stannous octoate, and 0.6 parts of fumed silica.

3. The composite coating on the surface of a dental pulp chamber retention crown according to claim 1, characterized in that, The mineralized polypeptide layer comprises a 160 mg / 100 mL polypeptide MPP3 solution.

4. The composite coating on the surface of a dental pulp chamber retention crown according to claim 1, characterized in that, The fumed silica has a particle size of 12 nm.

5. A composite coating for the surface of a dental pulp chamber retention crown according to any one of claims 1-4, characterized in that, The polyurethane prepolymer is prepared by the following method: Polycaprolactone diol is added to a reaction vessel; the reactor is heated to 110-120°C under continuous purging of dry nitrogen and vacuum conditions, and vigorously stirred at this temperature for 2-3 hours; subsequently, the vacuum is stopped, and the reactor temperature is lowered to 70-80°C under continuous nitrogen positive pressure protection; hexamethylene diisocyanate is slowly added dropwise over 30 minutes through a dropping funnel under vigorous stirring; the molar ratio of -NCO groups to -OH groups must be controlled to be 2:

1. After the addition is complete, add 0.05% of stannous octoate catalyst relative to the total feed mass; keep the reaction mixture at 80-85℃ for 3-5 hours; during the reaction, take a sample every 30 minutes and use the standard di-n-butylamine chemical titration method to accurately determine the percentage of free -NCO groups in the system. When the measured percentage of -NCO groups decreases and stabilizes, the polymerization reaction is considered complete, heating is stopped, and the temperature is lowered to room temperature under continuous nitrogen protection to obtain the polyurethane prepolymer.

6. A composite coating for the surface of a dental pulp chamber retention crown according to any one of claims 1-4, characterized in that, The modified nano-hydroxyapatite was prepared by the following method: nano-hydroxyapatite powder was placed in a clean oven and dried at 120°C for 4 hours; then, a 95:5 (v / v) ethanol / water mixed solution was prepared in a clean beaker; and using glacial acetic acid as a catalyst, the pH of the mixed solution was adjusted to 4.5-5.5, and 3-methacryloyloxypropyltriethoxysilane was added; the mixture was then magnetically stirred at room temperature for 1 hour. Take a reaction vessel and add the dried nano-hydroxyapatite powder to anhydrous ethanol; sonicate for 30 minutes to form a uniform, milky white suspension without obvious precipitate; under continuous sonication, add the activated 3-methacryloyloxypropyltriethoxysilane hydrolysate dropwise to the suspension through a constant pressure dropping funnel; after the addition is complete, raise the temperature of the reaction system to 60-70℃ and reflux at this temperature for 4-6 hours; after the reaction is complete, cool the suspension to room temperature; centrifuge the reaction solution using a high-speed centrifuge; discard the supernatant, redisperse the white precipitate obtained by centrifugation with excess anhydrous ethanol, and then centrifuge again to remove impurities; finally, place the washed product in a vacuum oven and dry to constant weight to obtain modified nano-hydroxyapatite.

7. The composite coating on the surface of a dental pulp chamber retention crown according to claim 5, characterized in that, The number-average molecular weight of polycaprolactone diol is Mn = 2000 g / mol.

8. The composite coating on the surface of a dental pulp chamber retention crown according to claim 6, characterized in that, Nano-hydroxyapatite is needle-shaped or rod-shaped, with a length of 50-100 nm and a diameter of 10-20 nm.

9. A method for preparing a composite coating on the surface of a dental pulp chamber retention crown, characterized in that, The preparation method includes a method for preparing a moisture-curing layer, a method for preparing an intermediate layer, and a method for preparing a mineralized polypeptide layer; The method for preparing the moisture-curing layer is as follows: polyurethane prepolymer, modified nano-hydroxyapatite, p-toluenesulfonyl isocyanate, stannous octoate, and fumed silica are added to a vacuum planetary mixer and fully mixed to obtain the moisture-curing layer. The intermediate layer is prepared by dissolving N-(3,4-dihydroxyphenylethyl)methacrylamide in a mixed solvent composed of ethanol and water to obtain an N-(3,4-dihydroxyphenylethyl)methacrylamide solution. The method for preparing the mineralized polypeptide layer is as follows: take the mineralized polypeptide MPP3, dissolve it in deionized water to obtain a polypeptide MPP3 solution.

10. The method for preparing a composite coating on the surface of a dental pulp chamber retention crown according to claim 9, characterized in that, In the preparation of the intermediate layer, the ratio of ethanol to water is 7:3.

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