Calcium fluoride nanoparticle composite and use thereof

Abstract

This invention discloses a calcium fluoride nanoparticle composite material and its application, comprising a resin matrix, calcium fluoride nanoparticles, and barium silane glass particles. The calcium fluoride nanoparticles constitute 15-40% of the composite material by mass, and the barium silane glass particles constitute 15-30% by mass. The calcium fluoride nanoparticles are prepared through the following steps: Step 1, calcium chloride and ammonium fluoride are dissolved in a methanol aqueous solution at a predetermined ratio and stirred until the solution becomes an opaque white suspension. The suspension is then centrifuged and washed to remove residual chloride and ammonium ions, yielding calcium fluoride nanoparticles. Step 2, the calcium fluoride nanoparticles are added to distilled water to form a suspension. The suspension is pumped into a spray drying system for atomization, and the spray-dried calcium fluoride nanoparticles are collected. The calcium fluoride nanoparticles obtained by spray drying in this invention exhibit better dispersibility and smaller particle size, improving the compressive strength and microhardness of the composite material.

Description

Technical Field

[0001] This invention relates to the field of oral medicine technology, and in particular to a calcium fluoride nanoparticle composite material and its application. Background Technology

[0002] Attachments are raised structures temporarily bonded to the tooth surface using composite resin. During invisible orthodontic treatment, they increase the contact area between the aligners and teeth, guiding force vectors in specific directions. They serve as the "mechanical hub" of invisible orthodontics and are widely used in the field. However, existing composite resins often lack sufficient hardness and stability. The consistently moist oral environment can lead to hydrolysis of the resin matrix and leaching of inorganic filler ions, inducing microcracks. Typically, severe wear and partial loss occur 6-12 months after bonding, resulting in ineffective force transmission from the aligners, causing orthodontic restart and prolonging treatment time. Furthermore, the presence of attachments on the tooth surface makes oral hygiene maintenance more difficult. Plaque easily accumulates around the brackets, causing enamel demineralization and chalky white spots, harming the patient's aesthetics and health.

[0003] Fluoride ion release technology is considered an effective means of preventing tooth decay. However, traditional fluoride ion release restorative materials present a trade-off between high fluoride ion release and good mechanical properties. The poor mechanical properties and hydrolysis issues of traditional materials result in a decrease in hardness the longer they are soaked in water.

[0004] As can be seen, dental materials developed in recent years have achieved good results in improving mechanical properties, but they still have obvious shortcomings. According to the toughening mechanism of inorganic nanoparticles, the smaller the particle size, the larger the contact area with the matrix. If the nanoparticles are evenly distributed, the toughening and strengthening effect is better. However, some researchers believe that smaller particle size is not always better, because smaller particle size makes it easier for particles to agglomerate, making it difficult to disperse evenly, and its addition may actually worsen the material properties. Therefore, surface treatment of inorganic particles is necessary during the manufacturing process. The total potential energy of the interaction between nanoparticles is the sum of repulsive and attractive potential energies. Surface treatment of nanoparticles is itself a process of reducing attractive potential energy, increasing repulsive potential energy, or both. How to improve the overall performance of orthodontic materials during the correction process remains a key focus for researchers and dentists. Summary of the Invention

[0005] The purpose of this invention is to address the technical deficiencies in the prior art by providing a calcium fluoride nanoparticle composite material.

[0006] Another object of the present invention is to provide an application of calcium fluoride nanoparticle composite material in the preparation of invisible orthodontic accessories.

[0007] The technical solution adopted to achieve the purpose of this invention is: A calcium fluoride nanoparticle composite material includes a resin matrix, calcium fluoride nanoparticles, and barium silane glass particles, wherein the mass fraction of the calcium fluoride nanoparticles in the composite material is 15-40%, and the mass fraction of the barium silane glass particles in the composite material is 15-30%. The calcium fluoride nanoparticles are prepared by the following steps: Step 1: Dissolve calcium chloride and ammonium fluoride in a methanol aqueous solution according to a predetermined ratio, stir until the solution becomes an opaque white suspension, then centrifuge, wash and dry to obtain calcium fluoride nanoparticles; Step 2: Add the calcium fluoride nanoparticles prepared in Step 1 to distilled water to form a calcium fluoride nanoparticle suspension. Pump the calcium fluoride nanoparticle suspension into a spray drying system for atomization and collect the spray-dried calcium fluoride nanoparticles.

[0008] In the above technical solution, the median particle size of the barium silanide glass particles is 0.9~1.2μm.

[0009] In the above technical solution, the average diameter of the calcium fluoride nanoparticles is 18~50nm.

[0010] In the above technical solution, the resin base is prepared by mixing bisphenol A glycidyl dimethacrylate, triethylene glycol dimethacrylate, ethyl p-dimethylaminobenzoate and camphorquinone in a mass ratio of 200:200:4:1 to 250:250:4:1.

[0011] In the above technical solution, in step 1, the molar ratio of calcium chloride and ammonium fluoride is 100:1 to 150:1.

[0012] In the above technical solution, in step 1, the molar ratio of methanol to water in the methanol-water solution is 1:1 to 1:5, the centrifugal washing speed is 6000 to 6500 r / min, and the drying temperature is 330 to 350 K.

[0013] In the above technical solution, in step 2, the atomization temperature of the calcium fluoride nanoparticle suspension is 330~350K, and the atomization feed rate is 15~20 / min.

[0014] In another aspect of the present invention, the application of the aforementioned calcium fluoride nanoparticle composite material in the preparation of invisible orthodontic accessories is disclosed.

[0015] Compared with the prior art, the beneficial effects of the present invention are: Traditional nanoparticle synthesis in solution environments requires washing with distilled water or other solvents to remove impurities. The interaction between the particle surface and the washing solution reduces the surface properties and reactivity of the nanoparticles. This invention utilizes spray drying technology, a highly efficient strategy—drying the obtained nanoparticles using specialized equipment avoids contact with any solvent, effectively preserving their highly active surface properties. Spray drying of calcium fluoride nanoparticles results in better dispersibility and smaller particle size, improving the release cycle and stability of fluoride ions, and further enhancing the compressive strength and microhardness of the calcium fluoride nanoparticle composite material. Attached Figure Description

[0016] Figure 1 The image shows the X-ray diffraction patterns of different calcium fluoride nanoparticles after co-precipitation according to the present invention.

[0017] Figure 2 The image shows the morphological characteristics of the coprecipitated products under different conditions as demonstrated by this invention.

[0018] Figure 3 The image shown is a transmission electron microscope image of Comparative Example 1, SNPs2.

[0019] Figure 4 The image shown is a transmission electron microscope image of SNPs4 of the present invention.

[0020] Figure 5 The image shown is a high-resolution transmission electron microscope image of SNPs4 of the present invention.

[0021] Figure 6 The figure shows a comparison of the compressive strength of the composite materials of the present invention filled with 20% NPs1, NPs2, NPs3, and NPs4.

[0022] Figure 7 The figure shows a comparison of the microhardness of the composite material filled with 20% NPs1, NPs2, NPs3, and NPs4 according to the present invention.

[0023] Figure 8 The figure shows a comparison of the compressive strength of the composite materials of the present invention filled with 20% SNPs1, SNPs2, SNPs3 and SNPs4.

[0024] Figure 9 The figure shows a hardness comparison of the composite materials filled with 20% SNPs1, SNPs2, SNPs3 and SNPs4 by spray drying according to the present invention.

[0025] Figure 10 The figure shows a comparison of the compressive strength of composite materials filled with different proportions of calcium fluoride using the spray drying method of the present invention.

[0026] Figure 11The figure shows a comparison of the hardness of composite materials filled with different proportions of calcium fluoride using the spray drying method of the present invention.

[0027] Figure 12 The figure shows a comparison of the cumulative fluoride ion release of composite materials filled with 20% SNPs2, SNPs3, and SNPs4 and composite materials filled with 10%, 20%, and 30% SNPs4. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Example 1 A method for preparing calcium fluoride nanoparticles includes the following steps: Step 1: Dissolve 2 mol of calcium chloride and 0.02 mol of ammonium fluoride in 100 mL of methanol aqueous solution and stir for 30 minutes until the solution becomes an opaque white suspension. Transfer the resulting suspension to a centrifuge tube. The molar ratio of methanol to water in the methanol aqueous solution is 5:1. Wash the suspension with anhydrous ethanol at 6000 rpm for 10 minutes. After washing three times to remove residual chloride and ammonium ions, dry in an electric vacuum drying oven at 343 K for 12 hours to obtain calcium fluoride nanoparticles, denoted as NPs4.

[0030] Step 2: Take 0.2g of NPs4 prepared in Step 1 and add it to 1000mL of distilled water to form a suspension. Pump the suspension into a spray drying system and atomize it through a nozzle at an inlet temperature of 373K with a feed rate of 15mL / min. Collect the product to obtain spray-dried calcium fluoride nanoparticles, denoted as SNPs4.

[0031] Example 2 A calcium fluoride nanocomposite resin is prepared by the following steps: The SNPs4 prepared in Example 1 were added to the resin matrix at a mass fraction of 20%. At the same time, barium silane glass particles with a median particle size of 1.0 μm and a mass fraction of 20% were used as co-fillers to obtain calcium fluoride nanocomposite materials. The resin matrix was prepared by bisphenol A glycidyl dimethacrylate, triethylene glycol dimethacrylate, ethyl p-dimethylaminobenzoate and camphorquinone in a mass ratio of 49.5:49.5:0.8:0.2.

[0032] Example 3 The only difference from Example 2 is that the amount of SNPs4 added is 10% by mass.

[0033] Example 4 The only difference from Example 2 is that the amount of SNPs4 added is 30% by mass.

[0034] Comparative Example 1 Using methanol-water solutions of different concentrations with methanol-to-water molar ratios of 1:3, 1:1, and 3:1, calcium fluoride nanoparticles named NPs1, NPs2, and NPs3 were obtained, respectively. Subsequently, 0.2 g of each of the calcium fluoride nanoparticles (NPs1, NPs2, and NPs3) was added to 1000 mL of distilled water to form suspensions, which were then pumped into a spray drying system and atomized through nozzles at a feed rate of 15 mL / min and an inlet temperature of 373 K. The final products were collected and named calcium fluoride SNPs1, SNPs2, SNPs3, and SNPs4.

[0035] Reference Figure 1 The X-ray diffraction patterns of NPs1, NPs2, NPs3, and NPs4 show that all synthesized powders exhibited typical diffraction peaks conforming to the JCPDS 35-0816 standard PDF card, with no other significant diffraction peaks detected. Notably, compared to other samples, calcium fluoride NPs1 exhibited a broader diffraction peak, indicating slightly lower crystallinity. As the methanol content in the solution increased, the diffraction peaks gradually became sharper, indicating a significant increase in crystallinity.

[0036] Reference Figure 2 SEM images of NPs1, NPs2, NPs3, and NPs4 show that when the methanol content is low (1:3 molar ratio), the synthesized calcium fluoride NPs1 tends to aggregate and the particle structure is not obvious, which is consistent with the XRD analysis results. When methanol and water are mixed at a 1:1 molar ratio, the obtained calcium fluoride NPs2 mainly consists of typical nanoparticles with an average diameter of about 198 nm. Except for the decrease in nanoparticle size with increasing methanol content, there are no significant differences in other coprecipitated products. For calcium fluoride NPs4 with a molar ratio of 5:1, nanoparticles with an average diameter of 88 nm were successfully synthesized. However, aggregates with diameters between 300-400 nm were present in these samples, indicating that the particle size distribution of the coprecipitated nanoparticles is relatively wide, which may have a potential impact on the mechanical properties of the CaF2-containing composite resin.

[0037] Reference Figure 2 Calcium fluoride nanoparticles prepared by co-precipitation exhibit high specific surface area and surface energy. Therefore, these particles are prone to agglomeration, leading to a reduction in effective surface area. Furthermore, during conventional washing and drying processes, capillary adsorption enhances the mutual attraction between calcium fluoride powders, bringing them closer together. Considering the bridging effect between hydroxyl groups on the powder surface, calcium fluoride nanoparticles easily aggregate. However, referring to… Figure 3 , Figure 4After spray drying, the rapid atomization and evaporation during the process significantly reduced the agglomeration of calcium fluoride nanoparticles. Therefore, the average diameter of the spray-dried calcium fluoride SNPs4 nanoparticles was approximately 18 nanometers, significantly smaller than that of the untreated sample. (Reference) Figure 5 High-resolution transmission electron microscopy (HRTEM) images show that the calcium fluoride nanoparticles exhibit clear lattice stripes with interplanar spacings of 0.276 nm and 0.316 nm, respectively, which are highly consistent with the (200) and (111) crystal planes of the calcium fluoride crystal.

[0038] Comparative Example 2 The only difference from Example 2 is that the spray-dried SNPs4 is replaced with SNPs1, SNPs2, or SNPs3.

[0039] Comparative Example 3 The only difference from Example 2 is that the NPs4 prepared by spray drying is replaced with NPs1, NPs2 or NPs3 that have not been spray dried.

[0040] Test Example 1 1. Mechanical performance testing: The composite material was injected into a silicone rubber cylindrical mold with a diameter of 4 mm and a height of 8 mm and then photocured to obtain a composite material sample.

[0041] Composite material compressive strength test: The composite material sample was subjected to compression test at room temperature using a universal testing machine at a rate of 0.75 mm / min.

[0042] Microhardness test of composite materials: The HMV-2T Vickers microhardness tester was used to complete the microhardness test by applying a 50-gram indenter load for 10 seconds.

[0043] Figure 6 and Figure 7 The figures show the compressive strength and microhardness comparison of the NPs1, NPs2, NPs3 and NPs4 composite materials prepared in Comparative Example 2. As can be seen from the figures, the compressive strength and hardness of the NPs1, NPs2, NPs3 and NPs4 composite materials all increased as the diameter of the crystalline calcium fluoride powder decreased.

[0044] Figure 8 and Figure 9 The figures show the compressive strength and microhardness comparison of the SNPs4 composite material in Example 2 and the SNPs1, SNPs2, and SNPs3 composite materials in Comparative Example 3, respectively.

[0045] Reference Figures 6-9 The compressive strength and hardness of composites with different calcium fluoride nanoparticles are shown. The composites filled with NPs1 and SNPs1 have the worst mechanical properties. Figure 8 , Figure 9 The results show that the composites filled with calcium fluoride SNPs exhibit a consistent pattern: the SNPs4-filled sample has the highest compressive strength (386.8 MPa) and microhardness (56.2 HV). The mechanical properties of the SNPs-filled composites surpass those of the NPs-filled materials. Experimental results indicate that compared to samples filled with NPs1, NPs2, NPs3, and NPs4, the average compressive strength of the composites filled with SNPs1, SNPs2, SNPs3, and SNPs4 is increased by 17.4%, 9.0%, 10.9%, and 12.2%, respectively. Based on the above microstructure analysis, the calcium fluoride nanoparticles have a large particle size and wide particle size distribution, which may lead to lower mechanical properties. However, the large particle size of calcium fluoride may reduce the contact area between the glass fiber particles and the resin matrix, thereby reducing the strength of the composite. On the other hand, the spray-dried calcium fluoride nanoparticles have a smaller particle size and a more uniform particle size distribution, which not only enhances the dispersion of particles in the resin matrix but also effectively improves the mechanical properties of the composite.

[0046] Reference Figure 10 The compressive strength graphs are shown for spray-dried SNPs4 composites with filler ratios of 10%, 20%, and 30%, with an unfilled SNPs4 composite as a control group, and SNPs2 composites with filler ratios of 10%, 20%, and 30%, with an unfilled SNPs4 composite as a control group. The graphs show that as the filler content increases from 10% to 30%, the compressive strength of both SNPs2 and SNPs4 composites initially increases and then decreases. Furthermore, when the filler content reaches 20%, the SNPs2 composite reaches 362.3 ± 16.4 MPa, and the SNPs4 composite reaches 386.8 ± 19.1 MPa. The SNPs4 composite outperforms the SNPs2 composite at all filler contents. When the filler content is 10%, 20% and 30%, the compressive strength of SNPs4 composite material is 349.9±25.6 MPa, 386.8±19.1 MPa and 370.1±17.1 MPa, respectively, which are 5.8%, 6.7% and 9.1% higher than that of SNPs2 composite material.

[0047] Figure 10 , Figure 11The results show that the compressive strength and hardness of all samples containing calcium fluoride fillers were significantly higher than those of the control group. The filler content had a significant impact on mechanical properties: when the filler content increased from 10% to 30%, the compressive strength of the SNPs2 and SNPs4 filled samples first increased and then decreased. When the filler content reached 20%, SNPs2 reached 362.3±16.4 MPa and SNPs4 reached 386.8±19.1 MPa; these two peak values ​​indicate that the filler content had reached the ideal state. This fluctuation may be due to the fact that excessive filler can hinder the movement of nanoparticles and affect the photocuring process, thereby reducing the strength of the composite material. It is noteworthy that the SNPs4 filled composite material was superior to SNPs2 at all filler contents. When the filler content was 10%, 20%, and 30%, the compressive strength of the former was 349.9±25.6 MPa, 386.8±19.1 MPa, and 370.1±17.1 MPa, respectively, representing increases of 5.8%, 6.7%, and 9.1% compared to the latter. On the other hand, the hardness of SNPs2 showed a similar trend with the change of filler content, while SNPs4 showed a slight increase, reaching a maximum of 58.8±5.2HV when the filler content increased from 20% to 30%. The superior mechanical properties can be attributed to the smaller particle size of SNPs4 compared to SNPs2. This not only enhances the formation of a stronger interlocking structure between the filler and the resin matrix, but also improves the interfacial adhesion.

[0048] 2. Fluoride ion release experiment: Reference Figure 12 Composite material samples with a diameter of 4 mm and a length of 8 mm were placed in 50 mL of solution at 310 K. The solution consisted of sodium chloride, acetic acid, and citric acid dihydrate dissolved in deionized water at a mass ratio of 5:5:1, and the pH was adjusted to 7.0 with sodium hydroxide. Fluoride ion concentrations were measured at days 1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70. 10 mL of sample was collected at each time point, and an equal volume of fresh solution was added. Fluoride ion concentrations were measured using a fluoride ion selective electrode (PXSJ-216F). After 70 days, the cumulative fluoride release reached 109.8 ± 7.6 μg / cm².

[0049] After 70 days of immersion, the cumulative fluoride release of the 20% SNPs4 composite material reached nearly 110±7.6 μg / cm², demonstrating the material's ability to release fluoride ions over a long period. After 70 days of immersion, the cumulative fluoride ion release of samples filled with 10%, 20%, and 30% SNPs4 were 42.5±4.2, 109.8±7.6, and 146.4±8.2 μg / cm², respectively. Based on the cumulative release data and the total calcium fluoride content in the composite material, it can be deduced that only about 0.39% of the fluoride ions stored in the 30% SNPs4-filled sample were released during the 70-day immersion period. This indicates that the sample still contains a large amount of unreleased fluoride ions, thus effectively improving the long-term fluoride ion release rate of the CaF₂-containing composite material.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A calcium fluoride nanoparticle composite material, characterized in that, The composite material comprises a resin matrix, calcium fluoride nanoparticles, and barium silane glass particles, wherein the calcium fluoride nanoparticles constitute 15-40% of the composite material by mass, and the barium silane glass particles constitute 15-30% of the composite material by mass. The calcium fluoride nanoparticles are prepared by the following steps: Step 1: Dissolve calcium chloride and ammonium fluoride in a methanol aqueous solution in a predetermined ratio, stir until the solution becomes an opaque white suspension, then centrifuge, wash and dry to obtain calcium fluoride nanoparticles. Step 2: Add the calcium fluoride nanoparticles prepared in Step 1 to distilled water to form a calcium fluoride nanoparticle suspension. Pump the calcium fluoride nanoparticle suspension into a spray drying system for atomization and collect the spray-dried calcium fluoride nanoparticles.

2. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, The median particle size of the barium silanide glass particles is 0.9~1.2μm.

3. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, The average diameter of the calcium fluoride nanoparticles is 18~50 nm.

4. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, The resin base is prepared by mixing bisphenol A glycidyl dimethacrylate, triethylene glycol dimethacrylate, ethyl p-dimethylaminobenzoate and camphorquinone in a mass ratio of 200:200:4:1 to 250:250:4:

1.

5. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, In step 1, the molar ratio of calcium chloride to ammonium fluoride is 100:1 to 150:

1.

6. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, In step 1, the molar ratio of methanol to water in the methanol-water solution is 1:1 to 1:5, the centrifugal washing speed is 6000 to 6500 r / min, and the drying temperature is 330 to 350 K.

7. The calcium fluoride nanoparticle composite material as described in claim 1, characterized in that, In step 2, the atomization temperature of the calcium fluoride nanoparticle suspension is 330~350K, and the atomization feed rate is 15~20 / min.

8. The application of the calcium fluoride nanoparticle composite material according to claim 1 in the preparation of invisible orthodontic accessories.

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