Dental glass and method for producing same

Abstract

Provided is dental glass having sufficient antibacterial properties through the inclusion of zinc. This dental glass contains 41-52 mass% of ZnO, 47-51 mass% of P2O5, 7 mass% or less of MgO, and 9 mass% or less of CaO. The fluorine content in the dental glass is preferably 3 mass% or less. The dental glass can be easily produced through a mixing step for mixing a starting material solution containing a zinc salt solution, a phosphate solution, an optional magnesium salt solution, and an optional calcium salt solution to form aggregates in the starting material solution, and a drying step for drying the aggregates to obtain a powder.

Description

Dental glass and its manufacturing method

[0001] The present application relates to dental glasses with antibacterial properties due to an appropriate amount of zinc, and to a method for producing the same.

[0002] Dental glass is used as a tooth filler. ２ O, P ２ O ５ Patent Document 1 discloses a water-soluble dental glass containing CaO, ZnO, and F. Patent Document 1 suggests that adding zinc to the water-soluble dental glass may provide antibacterial properties. However, the zinc content in the water-soluble dental glass of Patent Document 1 provides almost no antibacterial properties against Escherichia coli and Staphylococcus aureus.

[0003] Japanese Patent Application Laid-Open No. 2022-57915

[0004] The present invention aims to provide a dental glass that has antibacterial properties due to an appropriate amount of zinc.

[0005] The present application discloses a dental glass, a method for manufacturing the dental glass, and a dental material having the following aspects: (1) a glass containing 41% by mass or more and 52% by mass or less of ZnO, and a glass containing 52% by mass or less of P; ２ O ５ (2) Dental glass in (1), containing ZnO in an amount of 48% to 52% by mass and MgO in an amount of 0.8% to 2.6% by mass. (3) Dental glass in (1) or (2), having a fluorine content of 3% by mass or less.

[0006] (4) A method for producing dental glass according to any one of (1) to (3), comprising a mixing step of mixing a raw material liquid containing a zinc salt solution, a phosphate solution, an optional magnesium salt solution, and an optional calcium salt solution to produce an aggregate in the raw material liquid, and a drying step of drying the aggregate to obtain a powder. (5) A method for producing dental glass according to (4), further comprising a washing step of washing the aggregate with a liquid before the drying step. (6) A method for producing dental glass according to (4) or (5), further comprising a crushing step of crushing the powder to obtain a powder.

[0007] (7) A dental material comprising the dental glass according to any one of (1) to (3) and dental cement.

[0008] The dental glass of the present application contains ZnO at a predetermined content. Therefore, the dental glass of the present application has antibacterial properties due to zinc. The dental glass of the present application is manufactured using a liquid phase method. Therefore, dental glass with antibacterial properties can be easily manufactured. The dental material of the present application contains the dental glass of the present application. Therefore, the dental material of the present application has high antibacterial properties against bacteria that cause tooth decay.

[0009] Powder X-ray diffraction charts of dental glasses of Examples 1 to 3. SEM image of dental glass of Example 2. Particle size distribution histograms of dental glasses of Examples 1 to 3 after grinding. Powder X-ray diffraction charts of dental glasses of Examples 4 to 6. Powder X-ray diffraction charts of dental glasses of Examples 7 to 10. Powder X-ray diffraction charts of dental glasses of Examples 11 to 15. Powder X-ray diffraction charts of dental glasses of Examples 16 to 18. SEM image of dental glass of Example 8. Particle size distribution histograms of primary particles of dental glasses of Examples 4 to 18. Graph showing the antibacterial activity of dental glasses of Examples 1 to 3 against E. coli. Graph showing the antibacterial activity of dental glasses of Examples 1 to 9 and commercial dental cements against Staphylococcus aureus. Graph showing the antibacterial activity of dental glasses of Examples 4 to 9 and commercial dental cements against E. coli. Graph showing the antibacterial properties against Staphylococcus aureus of the dental glasses of Comparative Examples 4 to 9 and Examples 4 to 18. Graph showing the antibacterial properties against Escherichia coli of the dental glasses of Comparative Examples 1 to 3 and Examples 1 to 3 and a commercially available dental cement. Graph showing the antibacterial properties against Staphylococcus aureus of the dental glasses of Comparative Examples 1 to 3 and Examples 1 to 3 and a commercially available dental cement. Graph showing the antibacterial properties against Streptococcus mutans of the dental materials of the Examples.

[0010] The dental glass, the method for manufacturing the dental glass, and the dental material of the present application will be described below based on embodiments and examples. Note that duplicated explanations will be omitted as appropriate. The dental glass of the present application is a glass containing ZnO and P ２ O ５ The ZnO content in the dental glass of the embodiment is 41% by mass or more and 52% by mass or less. Since the ZnO content is 41% by mass or more, the dental glass of the embodiment has antibacterial properties against Escherichia coli and Staphylococcus aureus. Note that if the ZnO content exceeds 52% by mass, it becomes difficult to form an amorphous phase.

[0011] P in the dental glass of the embodiment ２ O ５ The content of P is 47% by mass or more and 51% by mass or less. ２ O ５The amorphous structure is formed by the content of MgO and CaO. The dental glass of the embodiment may contain one or more of MgO and CaO. The MgO content in the dental glass of the embodiment is 7% by mass or less, and the CaO content is 9% by mass or less. Fluorine has the effect of weakening the activity of bacteria that cause tooth decay. However, if excessive fluoride is released into the mouth, it may cause symptoms of poisoning.

[0012] Therefore, the fluorine content in the dental glass of the embodiment is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably only unavoidable impurities. Furthermore, although silver has antibacterial properties, it reacts with sulfur present in the oral cavity to form silver sulfide, which turns black. Therefore, the dental glass of the embodiment preferably does not contain silver other than unavoidable impurities. Potassium relieves toothache caused by external stimuli such as hypersensitivity. Therefore, the dental glass of the embodiment does not contain a potassium component, for example, K ２ It may contain O.

[0013] The fact that the dental glass of the embodiment is glass, i.e., amorphous, can be confirmed by powder X-ray diffraction measurement. The dental glass of the embodiment may be a composite of an amorphous phase and a crystalline phase. The dental glass of the present application can be used as a dental material such as a dental filler by blending it with dental cement. That is, the dental material of the embodiment of the present application comprises the dental glass of the embodiment and dental cement. The dental material of the embodiment containing the dental glass of the embodiment has higher antibacterial properties against bacteria that cause tooth decay than dental cement itself.

[0014] The dental glass of the embodiment can be produced by a melting method or a liquid phase method. In the melting method, raw materials including a zinc compound, a phosphorus compound, and optionally one or more magnesium compounds and calcium compounds are mixed, heated to or above the melting point of each raw material to melt, and then cooled and solidified to obtain dental glass as a mass. The mass is then crushed to obtain dental glass as a crushed product. The mass is crushed using, for example, an automatic mortar crusher.

[0015] The average particle size of dental glass, which is a pulverized product obtained by the melting method, is larger than the average particle size of the primary particles of dental glass, which is a powder product obtained by the liquid-phase method described below. The pulverized product obtained by the melting method has a large average particle size because plate-like lumps with a size of approximately 10 mm to 50 mm and a thickness of approximately 1 mm are pulverized using an automatic mortar and mortar grinding device. In contrast, the powder product obtained by the liquid-phase method has a small average particle size of primary particles, and can be easily made fine by simply breaking down the agglomerates of primary particles.

[0016] The average particle size of dental glass obtained as a pulverized product by the melting method is, for example, several μm, while the average particle size of dental glass obtained as a powder by the liquid phase method is, for example, several hundred nm. The average particle size of dental glass is the numerical average value of particle sizes in the particle size distribution of the primary particles of the dental glass. Dental glass with a small average particle size, for example, an average particle size of 30 nm to 300 nm, tends to have improved antibacterial properties against Escherichia coli and Staphylococcus aureus as the MgO content increases.

[0017] The dental glass of the embodiment can be manufactured by a liquid phase method, which is simpler than a melting method. The manufacturing method of the dental glass of the embodiment of the present application includes a mixing step and a drying step. In the mixing step, a raw material liquid containing a zinc salt solution, a phosphate solution, an optional magnesium salt solution, and an optional calcium salt solution is mixed to form aggregates in the raw material liquid. For example, a mixed liquid containing a zinc salt solution, an optional magnesium salt solution, and an optional calcium salt solution may be prepared in advance, and the mixed liquid may be added to a phosphate solution to prepare the raw material liquid and form aggregates in the raw material liquid.

[0018] The term "optional component" means that it may or may not be present. In other words, one or more of the magnesium salt solution and the calcium salt solution may or may not be used as a raw material. The raw material solution may also contain ions other than zinc, phosphate, magnesium, and calcium ions. For example, the raw material solution may contain potassium ions, sodium ions, strontium ions, barium ions, titanium ions, niobium ions, tantalum ions, aluminum ions, gallium ions, borate ions, or silicate ions.

[0019] Zinc salts include zinc chloride, zinc nitrate, zinc acetate, and zinc lactate. Phosphate salts include potassium pyrophosphate and sodium pyrophosphate. Magnesium salts include magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium lactate. Calcium salts include calcium chloride, calcium nitrate, calcium acetate, and calcium lactate. In addition, solutions of various salts are preferably aqueous solutions because they are easy to handle.

[0020] In the drying step, the aggregate is dried to obtain dental glass as a powder. The method for producing dental glass of the embodiment may further include a washing step before the drying step. In the washing step, the aggregate is washed with a liquid. When the raw material is an aqueous solution, it is preferable to wash the aggregate with water. The method for producing dental glass of the embodiment may further include a crushing step after the drying step. In the crushing step, the powder is crushed to obtain dental glass as a powder. The powder is crushed using, for example, an agate mortar.

[0021] (Production of dental glass by melting method) Zinc oxide (ZnO) (Kishida Chemical Co., Ltd., special grade), phosphoric acid (H ３ P.O. ４ ) (Kishida Chemical Co., Ltd., special grade), magnesium oxide (MgO) (Kishida Chemical Co., Ltd., special grade), and calcium carbonate (CaCO ３) (Kishida Chemical Co., Ltd., special grade) were mixed in the amounts shown in Table 1 below, and then dried overnight at 140°C to obtain a raw material powder. This raw material powder was placed in a platinum crucible and melted at 1500°C, poured out of the platinum crucible, and sandwiched between stainless steel plates to rapidly cool, obtaining a plate-like mass.

[0022] The plate-like body was crushed using an automatic mortar crusher (Nito Kagaku Co., Ltd., ALG-200WD) to obtain ZnO, P ２ O ５ The dental glasses of Examples 1 to 3 and Comparative Examples 1 to 3 were obtained as pulverized materials containing ZnO, P, and MgO. The results are shown in Table 1 below. ２ O ５ The mass percentages of MgO and CaO were calculated by X-ray fluorescence analysis (hereinafter the same). Figure 1 shows the powder X-ray diffraction charts of these dental glasses. The powder X-ray diffraction charts of all dental glasses showed a broad halo peak between 20° and 40°, which confirmed the amorphous nature of the glasses.

[0023] Figure 2 is an SEM image of the dental glass of Example 2. As shown in Figure 2, the particle sizes of the dental glass of Example 2 after crushing ranged from 0.04 μm for the smallest particle to 38.5 μm for the largest particle. Furthermore, the particle size distributions of the dental glasses of Examples 1 to 3 after crushing were collectively measured using SEM images. The results are shown in Figure 3. From the particle size distribution measurement results, the minimum particle size of the dental glasses of Examples 1 to 3 after crushing was 40 nm, the maximum particle size was 49 μm, the median particle size was 680 nm, and the average particle size was 4.0 μm.

[0024]

[0025] (Production of dental glass by liquid phase method) Zn ２＋ , Mg ２＋ , and Ca ２＋ Zinc chloride (ZnCl) was added to make the total concentration 1M. ２ ) (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) aqueous solution, magnesium chloride hexahydrate (MgCl ２ ・6H ２ O) (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) aqueous solution, and calcium chloride (CaCl２ ) (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) aqueous solution was mixed to obtain a mixed aqueous solution. ４ P ２ O ７ This mixed aqueous solution was added dropwise to an aqueous solution of 2,4-dichloro-1,4-dichloro- ...

[0026] The aggregate was washed with pure water and then dried at 200°C for 1 day to obtain a powder. The powder was lightly crushed using a mortar and pestle to obtain ZnO, P ２ O ５ , MgO, CaO, and K ２ Dental glasses of Examples 4 to 18 and Comparative Examples 4 to 9 were obtained as powders containing O. The results are shown in Table 2 below. FIGS. 4 to 7 are powder X-ray diffraction charts of the dental glasses of Examples 4 to 18. The powder X-ray diffraction charts of all dental glasses showed broad halo peaks at 20° to 40°, confirming their amorphous nature. In the powder X-ray diffraction charts of the dental glasses of Examples 4 to 18, peaks derived from zinc phosphate crystals were observed above the broad halo peaks. These dental glasses are composites in which an amorphous phase and a crystalline phase are combined.

[0027] Figure 8 is an SEM image of the dental glass of Example 8. The particle size of the primary particles of the dental glass of Example 8 measured based on Figure 8 was approximately 211 nm. The particle size of the dental glass obtained by the liquid phase method was smaller than that of the dental glass obtained by the fusion method. Furthermore, the particle size distribution of the primary particles of the dental glasses of Examples 4 to 18 was measured collectively using the same measurement method as for the dental glass obtained by the fusion method. The results are shown in Figure 9. From the particle size distribution measurement results, the minimum particle size of the primary particles of the dental glasses of Examples 4 to 18 was 30 nm, the maximum particle size was 920 nm, the median particle size was 190 nm, and the average particle size was 200 nm.

[0028]

[0029] (Evaluation of antibacterial properties of dental glass) Approximately 200 μg of the pulverized material obtained by the melting method or the powder obtained by the liquid phase method was uniaxially pressed at a pressure of 20 MPa for 5 minutes to prepare cylindrical specimens with a diameter of 10 mm and a thickness of 0.8 mm. ２ , Al ２ O ３ , SrO, ZnO, Na ２ O, CaO, La ２ O ３ , P ２ O ５ A commercially available dental cement A containing SiO and fluorine was filled into a mold with an inner diameter of 10 mm and a depth of 1.0 mm, and after hardening, the surface was polished with #1000 waterproof abrasive paper to prepare a cylindrical specimen. ２ , Al ２ O ３ , SrO, Na ２ O, P ２ O ５ Cylindrical specimens of the dental cement B containing fluoride and the commercially available dental cement B were prepared.

[0030] The antibacterial properties of the dental glasses of the Examples and Comparative Examples and the commercially available dental cement were evaluated by the following method. ６ After inoculating 100 μL of E. coli bacterial solution at CFU / mL, specimens of dental glass, dental cement A, and dental cement B of Examples 1 to 18 were placed at the center of the agar medium. After culturing at 37° C. for 24 hours, the width W of the formed inhibition zone, i.e., the difference between the radius of the inhibition zone and the radius of the specimen, was measured to evaluate the antibacterial activity against E. coli. In the same manner as in the evaluation of antibacterial activity against E. coli, 5×10 ６ The antibacterial activity against Staphylococcus aureus was also evaluated using 100 μL of a bacterial solution of Staphylococcus aureus at CFU / mL, and the results are shown in Figures 10 and 11.

[0031] As shown in Figures 10 and 11, the inhibition zone widths of the dental glasses of Examples 1 to 18 were 0.75 mm to 6 mm. This indicates that the dental glasses of Examples 1 to 18 have antibacterial properties against Escherichia coli and Staphylococcus aureus. On the other hand, commercially available dental cements A and B did not show an inhibition zone. This indicates that commercially available dental cements A and B did not have antibacterial properties against Escherichia coli and Staphylococcus aureus.

[0032] The antibacterial properties of the dental glasses of Comparative Examples 4 to 9 against Escherichia coli and Staphylococcus aureus were evaluated using the same method as in the antibacterial property evaluation described above. The results are shown in Figures 12 and 13. Figures 12 and 13 also show the antibacterial property evaluation results (same as Figures 10 and 11) for the dental glasses of Examples 4 to 18, which were produced using the same liquid-phase method. As shown in Figures 12 and 13, the dental glasses of Comparative Examples 4 to 9, which contained ZnO in an amount of 38% by mass or less, did not have antibacterial properties against Escherichia coli and Staphylococcus aureus. Furthermore, as can be seen from Figures 11, 13, and Table 2, the dental glasses of Examples 11, 12, 13, 14, and 16, which contained ZnO in an amount of 48% by mass or more and 52% by mass or less and MgO in an amount of 0.8% by mass or more and 2.6% by mass or less, had particularly high antibacterial properties against Staphylococcus aureus.

[0033] The antibacterial properties of the dental glasses of Comparative Examples 1 to 3 against Escherichia coli and Staphylococcus aureus were evaluated using the same method as in the antibacterial evaluation described above. The results are shown in Figures 14 and 15. Figures 14 and 15 also show the antibacterial evaluation results (same as the results shown in Figures 10 and 11) of the dental glasses of Examples 1 to 3, which were prepared using the same melting method, and dental cements A and B for reference. As shown in Figures 14 and 15, the dental glasses of Comparative Examples 1 to 3, which contained ZnO at a content of 31% by mass or less, had almost no antibacterial property against Escherichia coli. Furthermore, the dental glasses of Comparative Examples 1 to 3 had no antibacterial property against Staphylococcus aureus.

[0034] (Evaluation of Antibacterial Properties of Dental Materials) 30 mg of the dental glass of Example 7, Example 8, Example 9, Example 11, Example 12, or Example 13 was mixed with 270 mg of dental cement A to prepare 300 mg of each dental material. 300 mg of each dental material was filled into a silicone mold with an inner diameter of 10.0 mm and a depth of 2.0 mm and cured using a dental polymerization light irradiator (G-Light Prima II, GC). The surfaces of these cured materials were polished with #1000 waterproof abrasive paper to prepare evaluation specimens for Examples 7, 8, 9, 11, 12, and 13. Comparative evaluation specimens consisting of only 300 mg of dental cement A were also prepared using the same procedure.

[0035] As a test bacterium, Streptococcus mutans, a causative bacterium of dental caries, was cultured on a Brain Heart Infusion agar plate medium at 35°C for 24 hours, and the grown colonies were suspended in Brain Heart Infusion medium (manufactured by Eiken Chemical Co., Ltd.) to obtain a concentration of approximately 1 x 10 ７ A mutans streptococcus liquid of CFU / mL was obtained. The following eight types of samples were prepared using the evaluation samples of each example, the comparative evaluation samples, and the mutans streptococcus liquid.

[0036] Sample 1: 1 mL of mutans Streptococcus liquid Sample 2: Comparative evaluation sample with 2 mL of mutans Streptococcus liquid added Sample 3: Evaluation sample of Example 7 with 2 mL of mutans Streptococcus liquid added Sample 4: Evaluation sample of Example 8 with 2 mL of mutans Streptococcus liquid added Sample 5: Evaluation sample of Example 9 with 2 mL of mutans Streptococcus liquid added Sample 6: Evaluation sample of Example 11 with 2 mL of mutans Streptococcus liquid added Sample 7: Evaluation sample of Example 12 with 2 mL of mutans Streptococcus liquid added Sample 8: Evaluation sample of Example 13 with 2 mL of mutans Streptococcus liquid added

[0037] These eight samples were incubated at 37°C for 12 hours. Then, the optical density (O.D.) of each sample was measured when irradiated with visible light at a wavelength of 600 nm using an ultraviolet spectrophotometer (Corona Electric Co., Ltd., SH-1000). The results are shown in Figure 16. As shown in Figure 16, compared to the mutans streptococcus solution containing only dental cement (sample 2), the mutans streptococcus solutions containing dental cement and the dental glass of the example (samples 3 to 8) had lower optical densities, i.e., lower mutans streptococcus concentrations. This result indicates that the dental materials containing dental cement and the dental glass of the example have stronger antibacterial properties against caries-causing bacteria than dental cement itself.

Claims

1. ZnO is 41% by mass or more and 52% by mass or less, P ２ O ５ 47% by mass or more and 51% by mass or less of ZnO, 7% by mass or less of MgO, and 9% by mass or less of CaO.

2. Dental glass according to claim 1, containing ZnO in an amount of 48% by mass to 52% by mass, and MgO in an amount of 0.8% by mass to 2.6% by mass.

3. Dental glass according to claim 1 or 2, having a fluorine content of 3% by mass or less.

4. A method for producing dental glass according to claim 1 or 2, comprising a mixing step of mixing a raw material liquid containing a zinc salt solution, a phosphate solution, an optional magnesium salt solution, and an optional calcium salt solution to produce an aggregate in the raw material liquid, and a drying step of drying the aggregate to obtain a powder.

5. A method for producing dental glass according to claim 4, further comprising a washing step of washing the aggregates with a liquid before the drying step.

6. The method for producing dental glass according to claim 4, further comprising a grinding step of grinding the powder material to obtain a powder material.

7. A dental material comprising the dental glass according to claim 1 or 2 and dental cement.

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