Dental medullary cavity retention crown surface composite coating and preparation method thereof

Abstract

The invention discloses a dental medullary cavity retention crown surface composite coating and a preparation method, and belongs to the technical field of medullary cavity retention crowns. The dental medullary cavity retention crown surface composite coating is characterized by comprising the following components in parts by weight: a moisture curing layer, a middle layer and a mineralized polypeptide layer, the moisture curing layer is prepared from 75 parts of a polyurethane prepolymer, 12 to 24 parts of modified nano hydroxyapatite, 4 parts of p-toluenesulfonyl isocyanate, 0.2 part of stannous octoate and 0.6 part of fumed silica; according to the composite coating, it is guaranteed that the medullary cavity retention crown with the root canal internal extending retention achieves high-strength bonding in the deep portion of the root canal, the stability of the bonding interface of the retention crown in long-term use is avoided through a multiple defense mechanism, the durability of the bonding effect is effectively guaranteed, and effective retention can be maintained 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 prior art 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, 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. The preparation method of the polypeptide MPP3 solution is as follows: taking a mineralization-promoting polypeptide MPP3, dissolving it in deionized water to obtain a polypeptide MPP3 solution for standby use. The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA.

[0012] The intermediate layer is obtained by brush coating the N-(3,4-dihydroxyphenethyl) methacrylamide solution. 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; 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; 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; 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, When the percentage content of -NCO groups is reduced and stable, 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.

[0013] The number average molecular weight Mn of the polycaprolactone diol is 2000 g / mol.

[0014] The percentage value of the -NCO group content measured in the preparation process is reduced and stabilized at 3.58% in the present formulation.

[0015] 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; after the pH value of the mixed solution is adjusted to 4.5-5.5 using glacial acetic acid as a catalyst, 3-methacryloyloxypropyl triethoxysilane is added; and the mixture is stirred magnetically at room temperature for 1 hour. 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 the activated 3-methacryloyloxypropyl triethoxysilane is added dropwise to 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.

[0016] The white loose powder obtained is the 3-methacryloyloxypropyl triethoxysilane modified nano-hydroxyapatite. The finished product needs to be sealed and stored in a desiccator to prevent moisture absorption.

[0017] 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; 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. The moisture-cured layer needs to be strictly stored in anhydrous and nitrogen-filled conditions.

[0018] The preparation method of the intermediate layer is as follows: N-(3,4-dihydroxyphenethyl) methacrylamide is dissolved in a mixed solvent composed of ethanol and water, thereby obtaining an N-(3,4-dihydroxyphenethyl) methacrylamide solution. The preparation method of the mineralized polypeptide layer: taking the mineralization promoting polypeptide MPP3, dissolving in deionized water to obtain a polypeptide MPP3 solution.

[0019] The application method of the dental pulp cavity retention crown surface composite coating: after the root canal treatment is completed, the upper segment of the root canal is prepared to a depth of 1-3 mm for the extension segment of the retention crown, so that the shape is matched with the restoration; then, 37% phosphoric acid gel is used for selective etching of the inner wall of the pulp cavity and the root canal for 15 seconds; the phosphoric acid gel is thoroughly washed with water, and then the excess clear water in the dental cavity is sucked away with a cotton ball or a suction device, but the dentin surface is kept wet; then, a micro-brush is dipped in the polypeptide MPP3 solution, and the polypeptide MPP3 solution is lightly applied to all the dentin surfaces that need to be bonded in the pulp cavity and the root canal, and the wetting effect is maintained for 1-2 minutes; The mineralized ionic liquid is injected into the pulp cavity and the root canal to ensure that all the surfaces coated before 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 dipped in the N-(3,4-dihydroxyphenethyl) methacrylamide solution, and the N-(3,4-dihydroxyphenethyl) methacrylamide solution is uniformly applied to the just-mineralized dentin surface, 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.

[0020] Then, the moisture-cured coating is uniformly applied to the inner surface of the titanium alloy pulp cavity retention crown and the root canal extension segment, and then the pulp cavity retention crown with the coating is slowly and stably positioned on the tooth, so that the root canal extension segment is completely inserted into the root canal; a gentle and continuous pressure is applied to make the restoration completely in place, and the excess moisture-cured coating at the edge is squeezed out; 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, so that the initial curing is completed with the help of the moisture in the dentin surface and saliva.

[0021] 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.

[0022] The application has the beneficial effects that the composite coating of the application creatively selects and combines the mineralized polypeptide layer with mechanical locking effect, the intermediate layer with long-term chemical adhesion and anti-enzymatic effect as an interface pretreatment, and optimizes the best 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-cured layer; The present application selects a moisture-cured polyurethane prepolymer with flexible stress buffering characteristics as the main layer matrix, and matches a surface modified nano-hydroxyapatite with mechanical enhancement as a functional filler, the moisture-cured layer can be completely and uniformly cured in the deep root canal humid environment without illumination, and the flexible layer after curing can effectively absorb and dissipate occlusal stress, protect the fragile dental tissue, and is especially suitable for a pulp cavity retention crown with root canal extension retention; and the physiological moisture continuously exuded by the living dentin tubules ensures that the curing reaction will definitely achieve complete polymerization at the bonding interface; The composite coating of the present application ensures that the pulp cavity retention crown with root canal extension retention realizes high-strength bonding in the deep root canal, avoids the stability of the bonding interface of the retention crown in long-term use through multiple defense mechanisms, effectively guarantees the durability of the bonding effect, and can maintain effective retention for a longer period of time. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a structural diagram of the pulp cavity retention crown with root canal extension retention. DETAILED DESCRIPTION

[0024] To make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with examples, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit 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.

[0025] 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 involved. In the event of any conflict between the content of this specification and any incorporated document, the content of this specification shall prevail.

[0026] Many modifications and variations of the present application specification can be made without departing from the scope or spirit of the present application, which will be apparent to those skilled in the art. Other embodiments resulting from the present application specification will be apparent to those skilled in the art. The present application specification and examples are only exemplary.

[0027] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” and the like are open-ended terms that are intended to be synonymous with each other, and are used to merely indicate the presence of the following described elements or process steps, and are not meant to exclude the presence or addition of one or more other elements or process steps.

[0028] The “parts” indicated in the following examples are all weight parts.

[0029] A dental pulp cavity retention crown surface composite coating, comprising: a moisture curing layer, an intermediate layer, and a mineralized polypeptide layer. 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.

[0030] 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. The moisture curing layer needs to be strictly stored under the conditions of no water and nitrogen filling.

[0031] The intermediate layer comprises 1.0 wt% of N-(3,4-dihydroxyphenethyl) methacrylamide solution. The mineralized polypeptide layer comprises 120-200 mg / 100 mL of polypeptide MPP3 solution. The preparation method of the polypeptide MPP3 solution is as follows: the mineralization-promoting polypeptide MPP3 is dissolved in deionized water to obtain the polypeptide MPP3 solution for standby. The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA.

[0032] 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%.

[0033] The preparation method of 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 slowly added dropwise 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.

[0034] During the reaction, sampling is performed every 30 minutes, and the content percentage of free -NCO groups in the system is accurately determined by using standard di-n-butylamine chemical titration; when the measured 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.

[0035] The preparation method of the modified nanohydroxyapatite is as follows: 100 g of nanohydroxyapatite powder is placed in a clean oven and dried 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; using glacial acetic acid as a catalyst, the pH value of the mixed solution is adjusted to 4.5-5.5, and then 2 g of 3-methacryloyloxypropyl triethoxysilane is added; and the mixture is stirred magnetically at room temperature for 1 hour.

[0036] 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 activated 3-methacryloyloxypropyl triethoxysilane hydrolysate in a good dispersed state under continuous ultrasonic treatment; the hydrolysate is slowly and uniformly added dropwise 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 the reaction is refluxed at this temperature for 4-6 hours.

[0037] 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.

[0038] 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.

[0039] The nano-hydroxyapatite is needle-shaped or rod-shaped, with a length of 50-100 nm and a diameter of 10-20 nm. The fumed silica has a particle size of 12 nm.

[0040] Specifically, the preparation method of the comparative example is the same as that of the examples except that the specific component formula is different.

[0041] Table 1: Component formula of composite coating of Examples 1-9 Test Example Coating bonding strength test: select a single tooth of a cow, enlarge 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 the 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.

[0042] Coating sealing performance test: after preparing a class I cavity of a cow molar, enlarging the root canal file to 1.3 mm, and acid etching, coating the composite coating, and sufficiently 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.

[0043] 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. Calculate the water absorption rate = (m2-m3) / V; and the solubility = (m1-m3) / V.

[0044] Coating cushion performance test: using stainless steel mold to prepare 25x2x2mm beam-shaped coating sample, curing at 37℃, >95%RH; using Instron testing machine, set to span 20mm, speed 0.5-1mm / min, measure the elastic modulus of the coating.

[0045] Test example sample preparation: 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.

[0046] Mineralized ionic liquid is coated onto the dentin surface and left to stand for 10 minutes; the mineralized ionic liquid is 0.5g of calcium chloride and 0.6g of anhydrous disodium hydrogen phosphate dissolved in 100ml of Tris-HCl buffer.

[0047] Gently rinse off the remaining mineralized ionic liquid, then lightly blow it with an oil-free air gun for 2-3 seconds to remove only the clear water, and again keep the dentin moist; Use a new micro-brush to dip the N-(3,4-dihydroxyphenethyl) methacrylamide solution and evenly apply it to the mineralized dentin surface, and let it stand for 30 seconds; 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 disc; 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.

[0048] The structure of the pulp cavity retention crown with intracanal extension retention is shown in Figure 1 .

[0049] Table 2 Performance test results of examples 1-9 As can be seen from the above table: according to the conventional technical ideas in the field, increasing the content of reinforcing filler modified nano-hydroxyapatite can monotonously improve the mechanical properties of the material.

[0050] However, as can be seen from the performance test results in Table 2, the reinforcing filler in Example 1, Example 3 and Example 5 is gradually increased, but the elastic modulus and the bonding strength are not simply positively correlated, When the content of modified nano-hydroxyapatite increases 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 over-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 by those skilled in the art, and must be discovered through the creative labor of the inventor.

[0051] Table 3: Composition of Comparative Example 1-Comparative Example 8; The modified nano-hydroxyapatite in Comparative Example 8 is unmodified nano-hydroxyapatite.

[0052] Table 4: Performance test results of Comparative Example 1-Comparative Example 8; As can be seen from the above table: for the concentration of polypeptide MPP3, the concentration lower than 120 mg / 100 mL or higher than 200 mg / 100 mL will cause the bonding performance to deteriorate sharply; and the concentration deviating from the concentration of 160 mg / 100 mL on both sides will also cause the bonding performance to deteriorate sharply, rather than a gradual performance decline.

[0053] 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.

[0054] 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.

[0055] The interaction between the coatings presented is the result of the creative labor of the inventor, who successfully integrated the three seemingly independent technical points into an efficient synergistic system, rather than simply combining them; and the numerical range is not a conventional choice, but the result of the inventor's deep understanding of the complex antagonistic relationship between mineralization kinetics and resin penetration and creative experiments.

[0056] Example 11 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0057] The mineralized ionic solution of the Example 11 is that 0.25g of calcium chloride and 0.2g of anhydrous disodium hydrogen phosphate are dissolved in 100ml of Tris-HCl buffer solution; The pH of the Tris-HCl buffer solution is 7.4.

[0058] Example 12 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0059] The mineralized ionic solution of the Example 11 is that 0.25g of calcium chloride and 0.2g of anhydrous disodium hydrogen phosphate are dissolved in 100ml of Tris-HCl buffer solution; The pH of the Tris-HCl buffer solution is 7.4.

[0060] Comparative Example 9 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0061] The mineralized ionic solution of the Comparative Example 9 is that no calcium chloride and anhydrous disodium hydrogen phosphate are dissolved in the pure Tris-HCl buffer solution; The pH of the Tris-HCl buffer solution is 7.4.

[0062] Comparative Example 10 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0063] The mineralized ionic solution of the Comparative Example 10 is a traditional SBF simulated body fluid.

[0064] Comparative Example 11 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0065] The mineralized ionic solution 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; calcium acetate is used to replace calcium chloride; The pH of the Tris-HCl buffer solution is 7.4.

[0066] Comparative Example 12 The ratio is according to the ratio of Example 3, except that the mineralized ionic solution in the preparation process of the composite coating is different.

[0067] The mineralized ionic liquid of the comparative example 12 is 0.5 g of calcium chloride and 0.6 g of potassium dihydrogen phosphate dissolved in 100 ml of Tris-HCl buffer; the potassium dihydrogen phosphate is used to replace the anhydrous disodium hydrogen phosphate; The pH of the Tris-HCl buffer is 7.4.

[0068] Comparative example 13 The curing of the comparative example 13 uses light curing according to the performance test in the test example using self-adhesive resin cement, model: 3M ESPE RelyX™ U200 Automix, 3M Deutschland GmbH, Germany.

[0069] Table 5 performance test results of examples 11-12, comparative examples 9-13; As can be seen from the above table: on the basis of determining the optimal coating formula, the inventors further creatively optimize and screen the key steps in the application process, the mineralized 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.

[0070] Through creative labor, the inventors found that the specific coating system of the present 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 mineralized ionic liquid will also obviously cause the performance of the coating to change significantly, indicating that there is an unpredictable synergistic effect between the coating formula and the mineralization process in the present application.

[0071] Comparative examples 11 and 12 respectively use calcium acetate to replace calcium chloride and potassium dihydrogen phosphate to replace anhydrous disodium hydrogen phosphate; it is explained that the mixture of simple calcium salt and phosphate cannot of course realize the mineralization reaction expected by the present application with the coating in the examples.

[0072] Comparative example 13 is the prior art, which exhibits good comprehensive performance, and the bonding strength and elastic modulus both reach a high level of the prior art, so that it can provide reliable immediate retention force in conventional crown and bridge bonding. However, in the face of titanium alloy with extremely high modulus and dentin with relatively high modulus, it cannot play the 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 is easy to cause 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.

[0073] And the prior art of Comparative Example 13; its optimal mechanical properties highly depend on sufficient light initiation, at 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, the bonding layer at the deepest part of the root canal has problems such as insufficient degree of polymerization, low mechanical strength, and shrinkage stress cannot be effectively controlled, and this may also be the reason for the higher penetration depth of Comparative Example 13.

[0074] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. 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. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A dental pulp chamber-retaining crown surface composite coating, characterized by, Comprise: moisture-cured layer, intermediate layer, mineralized polypeptide layer; The moisture-cured 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. The intermediate layer comprises 1.0 wt% of N-(3,4-dihydroxyphenethyl) methacrylamide solution. The mineralized polypeptide layer comprises 120-200 mg / 100 mL of polypeptide MPP3 solution. The amino acid sequence of the polypeptide MPP3 is: PGEKADRAEKADRA. The modified nano-hydroxyapatite is 3-methacryloyloxypropyl triethoxysilane modified nano-hydroxyapatite.

2. A dental pulp cap retention crown surface composite coating according to claim 1, wherein, The moisture-cured 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.

3. The dental pulp lumen retention cap surface composite coating of claim 1, wherein, The mineralized polypeptide layer comprises 160 mg / 100 mL of polypeptide MPP3 solution.

4. The dental pulp lumen retention cap surface composite coating of claim 1 wherein, The fumed silica has a particle size of 12 nm.

5. A dental pulp cap retention crown surface composite coating according to any one of claims 1-4, characterized in that, The polyurethane prepolymer is prepared by the following method: in a reaction vessel, poly-caprolactone diol is added; under the condition of continuous dry nitrogen gas and vacuum, the reactor is heated to 110-120°C, and stirred vigorously for 2-3 hours at this temperature; then the vacuum is stopped, and the reactor temperature is reduced to 70-80°C under the protection of continuous nitrogen gas positive pressure; through a dropping funnel, hexamethylene diisocyanate is slowly added dropwise within 30 minutes under vigorous stirring; the molar ratio of -NCO groups to -OH groups needs to be controlled at 2:1; after the addition is completed, 0.05% 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; 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; when the percentage content of -NCO groups is reduced and stable, 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 gas, thereby obtaining the polyurethane prepolymer.

6. A dental pulp cap retention crown surface composite coating according to any one of claims 1-4, characterized in that, The modified nano-hydroxyapatite is prepared by the following method: nano-hydroxyapatite powder is dried in a clean oven at 120°C for 4 hours; then in a clean beaker, a 95:5 (v / v) ethanol / water mixed solution is prepared; 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 magnetically at room temperature for 1 hour. Take a reaction container, and add the dried nano-hydroxyapatite powder into anhydrous ethanol; ultrasonic treatment for 30 minutes to form a uniform, no obvious precipitate, milky white suspension; under continuous ultrasonic, add the activated 3-methacryloyloxypropyl triethoxysilane hydrolysate into the suspension through a constant pressure dropping funnel; after the dropping is completed, raise the temperature of the reaction system to 60-70 DEG C, and reflux the reaction at this temperature for 4-6 hours; after the reaction is completed, cool the suspension to room temperature; use a high-speed centrifuge to centrifuge the reaction liquid; discard the supernatant, and redisperse the white precipitate obtained by centrifugation with excess anhydrous ethanol, and then centrifuge again to remove impurities; Preferably, the washed product is placed in a vacuum oven, and dried to constant weight, to obtain the modified nano-hydroxyapatite.

7. The dental pulp cap retention crown surface composite coating of claim 5, wherein, The number average molecular weight Mn of the polycaprolactone diol is 2000 g / mol.

8. The dental pulp cap retention crown surface composite coating of claim 5, wherein, The nano-hydroxyapatite is needle-like or rod-like, with a length of 50-100 nm and a diameter of 10-20 nm.

9. A method of preparing a dental pulp chamber-retaining crown surface composite coating, characterized by, The preparation method comprises a preparation method of a moisture-cured layer, a preparation method of an intermediate layer, and a preparation method of a mineralized polypeptide layer. The preparation method of the moisture-cured layer comprises the following steps: adding polyurethane prepolymer, modified nano-hydroxyapatite, p-toluenesulfonyl isocyanate, stannous octoate, and fumed silica into a vacuum planetary mixer, and fully blending to obtain the moisture-cured layer. The preparation method of the intermediate layer comprises the following steps: dissolving N-(3, 4-dihydroxyphenethyl) methacrylamide in a mixed solvent composed of ethanol and water to obtain an N-(3, 4-dihydroxyphenethyl) methacrylamide solution. The preparation method of the mineralized polypeptide layer comprises the following steps: dissolving the mineralization-promoting polypeptide MPP3 in deionized water to obtain a polypeptide MPP3 solution.

10. A method of preparing a dental pulp chamber retainer crown surface composite coating according to claim 9, wherein, In the preparation process of the intermediate layer, the ratio of ethanol to water is 7:3.

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