A method for improving the mechanical and biological activity of lithium disilicate glass-ceramics by composite ion exchange

Abstract

The present invention discloses a method for improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange, which comprises: first, removing crystallization water from Ca(NO3)2·4H2O to obtain Ca(NO3)2; second, placing KNO3 in Ca(NO3)2 and heating and keeping the mixture warm until it is completely melted to obtain a KNO3-Ca(NO3)2 mixed bath salt; third, maintaining the KNO3-Ca(NO3)2 mixed bath salt at a constant temperature, and placing the mixture into lithium disilicate glass ceramics for ion exchange treatment; fourth, taking it out, cooling it to room temperature, and washing the residual molten salt on the surface. The present invention uses Li + / Ca 2+ 、Li + / K + Composite ion exchange regulates the stress state and ion distribution of the surface of lithium disilicate glass ceramics, and constructs a residual compressive stress layer and a gradient Ca-rich layer on its surface. 2+ , K + The bioactive alkali ion layer improves the mechanical properties and bioactivity of lithium disilicate glass ceramics and is suitable for medical implants.

Description

Technical Field

[0001] The invention belongs to the technical field of biomedical materials, and in particular relates to a method for improving the mechanics and biological activity of lithium disilicate glass ceramics through composite ion exchange. Background Art

[0002] Lithium disilicate glass-ceramic is a common clinical restorative material commonly used in dental restorations. Reference 1 (Daguano JKMB, Milesi MTB, Rodas ACD, Weber AF, Sarkis JES, Hortellani MA, Zanotto ED. In vitro biocompatibility of new bioactive lithia-silica glass-ceramics. Materials Science and Engineering: C, 2019, 94: 117-125) and Reference 2 (Huang S, Li Y, Wei S, Huang Z, Gao W, Gao P. A novel high-strength lithium disilicate glass-ceramic featuring a highly intertwined microstructure. Journal of the European Ceramic Society, 2017, 37: 1083-1094) point out that lithium disilicate glass-ceramic has good mechanical properties, chemical stability and biocompatibility, and has great application potential in the field of orthopedic implants. However, reference 3 (Kulkarni A, Rothrock J, Thompson J. Impact of gastric acid induced surface changes on mechanical behavior and optical characteristics of dental ceramics. Journal of Prosthodontics, 2020, 29: 207-218) points out that lithium disilicate glass-ceramics is an intrinsically bioinert inorganic material that cannot achieve osteogenesis and bone integration, hindering its application in bone repair. Therefore, improving the bioactivity of lithium disilicate glass-ceramics without reducing its mechanical properties is crucial for its application in bone repair.

[0003] Ion exchange is a commonly used chemical strengthening method for lithium disilicate glass ceramics. It can induce gradient residual compressive stress on the surface of glass ceramics to prevent premature failure of glass ceramics. In addition, reference 4 (Li XC, Li D, Zhang SF, Jing L, Zhou WH, He L, Yu S, Meng M. Effect of Li + / Na + Exchange on mechanical behavior and biological activity of lithium disilicate glass-ceramic. Journal of the Mechanical Behavior of Biomedical Materials, 2022, 126: 105036) points out that ion exchange can realize the exchange of alkali ions in the matrix with bioactive alkali ions in the salt bath, inducing the formation of a gradient bioactive alkali ion-rich layer. Generally speaking, the dissolution of active alkali ions in body fluids is conducive to the expression of osteogenic genes, promoting new bone formation and bone integration, such as reference 5 (Marin CP, Santana GL, Robinson M, Willerth SM, Crovace MC, Zanotto ED. Effect of bioactive / F18glass scaffolds onosteogenic differentiation of human adipose stem cells. Journal of BiomedicalMaterials Research Part A, 2021,109:1293-1308) and reference 6 (Sasaki JI, Kiba W, AbeGL, Katata C, Hashimoto M, Kitagawa H, Imazato S. Fabrication of strontium-releasable inorganic cement by incorporation of bioactive glass.DentalMaterials,2019,35:780-788) pointed out that Na + , Ca 2+ 、Sr 2+ Plasma dissolution is of great significance in promoting osteogenesis. Using ion exchange methods to achieve a gradient distribution of target active ions on the surface of lithium disilicate glass-ceramics is expected to address its inherent bioinertness. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange in view of the above-mentioned deficiencies of the prior art. + / Ca 2+ 、Li + / K + Composite ion exchange regulates the stress state and ion distribution of the surface of lithium disilicate glass ceramics, and constructs a residual compressive stress layer and a gradient Ca-rich layer on its surface. 2+ , K + The bioactive alkali ion layer improves the mechanical properties and bioactivity of lithium disilicate glass-ceramics, and solves the problem of intrinsic bio-inertness defects of lithium disilicate glass-ceramics.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange, characterized in that the method comprises the following steps:

[0006] Step 1: Place Ca(NO3)2·4H2O in an Al2O3 crucible to remove crystallization water to obtain dry Ca(NO3)2;

[0007] Step 2: Add KNO3 to the Ca(NO3)2 obtained in step 1, then heat and keep warm until completely melted and stir evenly to obtain a KNO3-Ca(NO3)2 mixed bath salt with a molar ratio of KNO3 to Ca(NO3)2 of 7:3;

[0008] Step 3: Keep the KNO3-Ca(NO3)2 mixed bath salt obtained in step 2 at a constant temperature of 400℃, and then put the lithium disilicate glass ceramics into the constant temperature mixed bath salt for ion exchange treatment to complete Li + / Ca 2+ 、Li + / K + Composite ion exchange;

[0009] Step 4: After the composite ion exchange is completed in step 3, the lithium disilicate glass ceramic is taken out and cooled to room temperature, and the residual molten salt on the surface is rinsed with deionized water.

[0010] The above-mentioned composite ion exchange method for improving the mechanical and biological activity of lithium disilicate glass-ceramics is characterized in that the temperature of the de-crystallization water treatment in step 1 is 300°C and the treatment time is 5 hours. By adopting this treatment temperature and time, the water in the Ca(NO3)2·4H2O is effectively removed, thereby preventing the adverse effects of water on the KNO3-Ca(NO3)2 mixed bath salt.

[0011] The above-mentioned method of improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange is characterized in that the heating and heat preservation to complete melting in step 2 is at a temperature of 400° C. and a time of 30 minutes.

[0012] The above-mentioned method for improving the mechanical and biological activity of lithium disilicate glass-ceramics by composite ion exchange is characterized in that, in step 3, the lithium disilicate glass-ceramics are allowed to rest on a constant-temperature mixed bath salt for 20 minutes before being placed in the constant-temperature mixed bath salt. This resting process prevents thermal shock of the constant-temperature mixed bath salt on the lithium disilicate glass-ceramics, ensuring the smooth progress of the composite ion exchange process.

[0013] The above-mentioned method of improving the mechanical and biological activities of lithium disilicate glass-ceramics by composite ion exchange is characterized in that the ion exchange treatment time in step three is 16 hours to 64 hours.

[0014] The above-mentioned method of improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange is characterized in that the Li + / Ca 2+ 、Li + / K + Composite ion exchange Li + / Ca 2+ The exchange layer depth is 8.4 μm, Li + / K + The exchange layer depth is 9.4 μm, and after composite ion exchange, the surface CaO and KO mass fractions reach 2.6% and 17.2%, respectively. This exchange layer depth and the mass fraction of the exchanged ion oxides are directly related to the subsequent ion release and the degree of induced residual compressive stress in the human body environment of the composite ion-exchanged lithium disilicate glass-ceramic, thereby ensuring the mechanical properties and bioactivity of the lithium disilicate glass-ceramic.

[0015] The above-mentioned method for improving the mechanical and biological activities of lithium disilicate glass-ceramics by composite ion exchange is characterized in that the cooling method in step 4 is air cooling.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention uses KNO3-Ca(NO3)2 mixed bath salt to carry out ion exchange treatment on lithium disilicate glass ceramics, through Li + / Ca 2+ 、Li + / K + Composite ion exchange induces the construction of a residual compressive stress layer on the surface of lithium disilicate glass-ceramics, effectively improving the mechanical properties of lithium disilicate glass-ceramics.

[0018] 2. The present invention uses KNO3-Ca(NO3)2 mixed bath salt to carry out ion exchange treatment on lithium disilicate glass ceramics, through Li + / Ca 2+ 、Li + / K + Composite ion exchange induces a surface gradient concentration distribution of Ca-rich materials on the surface of lithium disilicate glass-ceramics 2+ , K + The bioactive alkali ion layer has a tendency to be released in body fluids, which is beneficial to promoting osteogenesis and bone integration, and improving the bioactivity of lithium disilicate glass ceramics.

[0019] 3. The method of the present invention has simple process, low equipment requirements, no pollution to the environment, low processing cost, wide applicability, and can achieve the regulation of the surface composition of lithium disilicate glass ceramics under mixed bath salt ion exchange, and obtain good strengthening and bioactivation effects. It can meet the mechanical and bioactivity performance requirements of orthopedic repair materials for lithium disilicate glass ceramics and has broad application prospects in the field of medical implants.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 For Example 1 of the present invention, + / Ca 2+ 、Li + / K + Fracture toughness and flexural strength of lithium disilicate glass-ceramics before and after composite ion exchange.

[0022] Figure 2 For Example 1 of the present invention, + / Ca 2+ 、Li + / K + Surface Vickers hardness diagram of lithium disilicate glass-ceramics before and after composite ion exchange.

[0023] Figure 3a For Example 1 of the present invention, + / Ca 2+ 、Li + / K + Depth of the ion exchange layer in lithium disilicate glass-ceramics after composite ion exchange treatment.

[0024] Figure 3b For Example 1 of the present invention, + / Ca 2+ 、Li + / K +Mass fraction of CaO and K2O on the surface of lithium disilicate glass-ceramics after composite ion exchange treatment.

[0025] Figure 4a For Example 1 of the present invention, + / Ca 2+ 、Li + / K + Surface SEM image (500×) of lithium disilicate glass ceramics after composite ion exchange treatment after immersion in SBF simulated body fluid for 28 days.

[0026] Figure 4b For Example 1 of the present invention, + / Ca 2+ 、Li + / K + Surface SEM image (10000×) of lithium disilicate glass ceramics after composite ion exchange treatment after immersion in SBF simulated body fluid for 28 days.

[0027] Figure 5 For Example 1 of the present invention, + / Ca 2+ 、Li + / K + XRD pattern of lithium disilicate glass-ceramics after composite ion exchange treatment after immersion in SBF simulated body fluid for 28 days. DETAILED DESCRIPTION

[0028] Example 1

[0029] This embodiment includes the following steps:

[0030] Step 1: Place 12.74 g of Ca(NO3)2·4H2O into an Al2O3 crucible and perform a de-crystallization water treatment at 300°C for 5 h to obtain dry Ca(NO3)2;

[0031] Step 2: Add 17.26 g of KNO3 into the Ca(NO3)2 obtained in step 1, then heat and keep warm at 400°C for 30 minutes to completely melt it and stir it evenly to obtain a KNO3-Ca(NO3)2 mixed bath salt with a molar ratio of KNO3 to Ca(NO3)2 of 7:3;

[0032] Step 3: Keep the KNO3-Ca(NO3)2 mixed bath salt obtained in step 2 at a constant temperature of 400℃, then place the lithium disilicate glass ceramics on the constant temperature mixed bath salt for 20 minutes, and then place it in the constant temperature mixed bath salt for ion exchange treatment for 64 hours to complete Li + / Ca 2+ 、Li + / K + Composite ion exchange;

[0033] Step 4: After the composite ion exchange is completed in step 3, the lithium disilicate glass ceramic is taken out and air-cooled to room temperature, and the residual molten salt on the surface is rinsed with deionized water to obtain surface-strengthened and bioactivated lithium disilicate glass ceramic.

[0034] (1) Mechanical experiments

[0035] Vickers indentation fracture toughness method, three-point bending method and Vickers hardness were used to test the Li + / Ca 2+ 、Li + / K + The fracture toughness, flexural strength and Vickers hardness of lithium disilicate glass ceramics before and after composite ion exchange treatment were tested. The results are as follows Figures 1 and 2 shown.

[0036] from Figure 1 It can be seen that after ion exchange treatment, the fracture toughness of lithium disilicate glass ceramics has little change from the original state, while the flexural strength is increased from the original 175MPa to a maximum of 304.2MPa. Figure 2 It can be seen that the Vickers hardness is from H V 531 is upgraded to H V 591, illustrating the present invention is carried out + / Ca 2+ 、Li + / K + Composite ion exchange treatment can improve the mechanical properties of lithium disilicate glass-ceramics.

[0037] (2) Depth of composite ion exchange and surface CaO and K2O mass ratio detection

[0038] The steps 3 of Example 1 of the present invention are respectively + / Ca 2+ 、Li + / K + The depth of the ion exchange layer and the mass ratio of CaO and K2O on the surface of lithium disilicate glass ceramics after composite ion exchange treatment were tested. The results are as follows Figure 3a 、 3b As shown. Figure 3a It can be seen that the Li in the lithium disilicate glass ceramics after composite ion exchange in Example 1 + / Ca 2+ The exchange layer depth is 8.4 μm, Li + / K + The depth of the exchange layer is 9.4 μm; Figure 3b It can be seen that the surface CaO and K2O mass fractions of the lithium disilicate glass ceramics after composite ion exchange in Example 1 reach 2.6% and 17.2%, respectively.

[0039] (III) SBF simulated body fluid immersion experiment

[0040] The Li + / Ca 2+ 、Li + / K + The lithium disilicate glass ceramics after composite ion exchange treatment were placed in polyethylene bottles containing 120 mL of SBF simulated body fluid and immersed in a 37°C constant temperature box for 28 days. They were then rinsed with deionized water and dried with cold air. The surface morphology was then observed and X-ray diffraction analyzed. The results are as follows: Figure 4a-4b and Figure 5 shown.

[0041] from Figure 4a It can be seen that after the lithium disilicate glass ceramics treated with composite ion exchange in Example 1 were immersed in SBF simulated body fluid for 28 days, an obvious and densely distributed mineralized layer was produced on the surface, which was in a stacked shape; Figure 4b It can be seen that after the lithium disilicate glass ceramics treated with composite ion exchange in Example 1 were immersed in SBF simulated body fluid for 28 days, the mineralized layer was microscopically spherical and porous.

[0042] from Figure 5 It can be seen that after the lithium disilicate glass ceramics treated with composite ion exchange in Example 1 were immersed in SBF simulated body fluid for 28 days, XRD confirmed that the surface mineralized layer was hydroxyapatite (HA), further demonstrating that the composite ion exchange treatment can enhance the biological activity of lithium disilicate glass ceramics.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the constant temperature in step 3, i.e., the temperature of the ion exchange treatment, is 450°C.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for improving the mechanical and biological activity of lithium disilicate glass ceramics by composite ion exchange, characterized in that: The method comprises the following steps: Step 1: Place Ca(NO3)2·4H2O in an Al2O3 crucible to remove crystallization water to obtain dry Ca(NO3)2; Step 2: Add KNO3 to the Ca(NO3)2 obtained in step 1, then heat and keep warm until completely melted and stir evenly to obtain a KNO3-Ca(NO3)2 mixed bath salt with a molar ratio of KNO3 to Ca(NO3)2 of 7:3; Step 3: Keep the KNO3-Ca(NO3)2 mixed bath salt obtained in step 2 at a constant temperature of 400℃, and then put the lithium disilicate glass ceramics into the constant temperature mixed bath salt for ion exchange treatment to complete Li + / Ca 2+ 、Li + / K + Composite ion exchange; Step 4: After the composite ion exchange is completed in step 3, the lithium disilicate glass ceramic is taken out and cooled to room temperature, and the residual molten salt on the surface is rinsed with deionized water.

2. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: The temperature of the de-crystallization water treatment in step 1 is 300° C. and the treatment time is 5 h.

3. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: The heating and heat preservation in step 2 until the complete melting temperature is 400° C., and the time is 30 minutes.

4. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: The lithium disilicate glass ceramics described in step 3 are placed on the constant temperature mixed bath salt for 20 minutes before being placed in the constant temperature mixed bath salt.

5. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: The ion exchange treatment in step 3 is carried out for 16 to 64 hours.

6. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: Li described in step 3 + / Ca 2+ 、Li + / K + Composite ion exchange Li + / Ca 2+ The exchange layer depth is 8.4 μm, Li + / K + The depth of the exchange layer is 9.4 μm. After composite ion exchange, the surface CaO and K2O mass fractions of lithium disilicate glass ceramics reach 2.6% and 17.2%, respectively.

7. The method for improving the mechanical and biological activities of lithium disilicate glass ceramics by composite ion exchange according to claim 1, characterized in that: The cooling method described in step 4 is air cooling.

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