阅读说明：本技术 一种用于治疗龋病的材料的制备方法 (Preparation method of material for treating dental caries ) 是由 洪亮 张蕊 路浩军 邵荣 郭旺明 田力 于 2020-06-29 设计创作，主要内容包括：本发明属于口腔材料领域,具体涉及一种治疗龋病的材料的制备方法,即氟化氨银的制备方法。本发明以硝酸银、氢氧化钠、氟化铵、氨水为原料,为制备氟化氨银溶液提供了新思路,通过梯度加热实现制备过程的精制,将过量的原料去除,避免副产物的生成和析出。该制备工艺经济、环保、稳定,可以制备出杂质少、副产物少且长期放置稳定的氟化氨银溶液。(The invention belongs to the field of oral cavity materials, and particularly relates to a preparation method of a material for treating dental caries, namely a preparation method of silver ammonium fluoride. The method takes silver nitrate, sodium hydroxide, ammonium fluoride and ammonia water as raw materials, provides a new idea for preparing the ammonia silver fluoride solution, realizes refining of the preparation process by gradient heating, removes excessive raw materials, and avoids generation and precipitation of byproducts. The preparation process is economic, environment-friendly and stable, and can prepare the ammonia silver fluoride solution which has less impurities and byproducts and is stable after long-term storage.)

1. A method of preparing a material for treating caries comprising the steps of:

1) preparing silver oxide:

after dissolving the silver nitrate solid by adding ultrapure water, dropwise adding a sodium hydroxide solution, and finishing the reaction when a large amount of precipitate exists in the reaction solution;

filtering, wherein a filter cake is silver oxide precipitate;

the reaction equation is: 2AgNO₃+2NaOH＝Ag₂O↓+H₂O+2NaNO₃

2) Preparation of silver ammonium fluoride (SDF) solution

Adding the silver oxide obtained in the step 1) into ultrapure water, stirring and adding ammonium fluoride solid to obtain a suspension, slowly dropwise adding ammonia water, controlling the reaction temperature to be 5-25 ℃, and filtering after the solution is clarified to obtain a filtrate, wherein the filtrate is an ammonia silver fluoride solution; the reaction equation is: ag₂O+2NH₄F+2NH₃·H₂O→2Ag(NH₃)₂F+3H₂O

3) And (3) refining:

gradient heating: the first stage is as follows: the reaction temperature is 50-60 ℃, the heating time is more than or equal to 1.5h, the ammonia concentration is 7.5-10.55%, and the pH value is less than or equal to 11.8; and a second stage: the reaction temperature is 70-80 ℃, the heating time is more than or equal to 1.0h, the ammonia concentration is 7.5-10.55%, and the pH value is less than or equal to 11.8; and a third stage: the reaction temperature is 96-101 ℃, the heating time is more than or equal to 3.0h, the ammonia concentration is 7.5-9.07 percent, and the pH value is less than or equal to 10; the evaporation capacity of the solution in the whole refining process is not less than 5.6%.

2. The method of claim 1, wherein: in step 3), gradient heating: the internal temperature is 56 ℃, and the heating is carried out for 1.5 hours; heating at an internal temperature of 72 ℃ for 1 hour; the internal temperature is 96-101 ℃, and the heating is carried out for 3 hours.

3. The method of claim 1, wherein: in the step 1), freshly prepared silver oxide is used, and the silver oxide precipitate is washed to be neutral for many times by using ultrapure water, so that nitrate ions are less than one ten-thousandth.

4. The method of claim 1, wherein: step 1) the purity of NaOH is more than 99.15%.

5. The method of claim 1, wherein: in step 2), silver oxide: ammonium fluoride: the mass ratio of the ammonia water is 1: 2-2.2: 2.3-2.5.

6. The method of claim 5, wherein: in step 2), silver oxide: ammonium fluoride: the mass ratio of ammonia water is 1:2: 2.3.

7. The method of claim 1, wherein: further comprises the following steps of 4) filtering and pH adjusting:

filtering the refined silver ammonium fluoride solution in the step 3) by using a 0.22-micron microporous filter membrane, and adjusting the pH of the filtrate to 10.0-10.2 by using ammonia water; the product which meets the technical indexes of 24.0-27.0% (w/v) of silver content, 5.0-6.0% (w/v) of fluorine content, 7.5-11.0% (w/v) of ammonia content, no precipitation generation when the pH value of the solution is adjusted to 6.0 by 1mol/L nitric acid and the like is obtained.

Technical Field

The invention belongs to the field of oral cavity materials, and particularly relates to a preparation method of a material for treating dental caries, namely a preparation method of silver ammonium fluoride.

Background

Caries is a disease in which the hard tissues of the tooth body undergo chronic progressive destruction under the influence of various factors, mainly bacteria.

Caries prevention generally employs the following measures:

(1) strengthening oral health, and controlling dental plaque

(2) Using fluorides

(3) Dietary restrictions

Fluoride is the most effective material for preventing dental caries proved by scientific research and clinical practice. Its -inhibiting effect is achieved primarily by locally strengthening tooth structure, inhibiting demineralization processes and enhancing remineralization. There are three approaches to the use of fluoride to prevent caries:

(1) fluorinated drinking water or organized gargling projects combined with health education are developed through communities, schools and kindergartens.

(2) Fluoride-containing oral care products, such as fluoride-containing toothpastes, fluoride-containing mouthwashes, and the like, are used by families or individuals.

(3) Materials such as fluorine paints, fluorine solutions, fluorine gels, fluorine-containing adhesives and restorations are used by oral professionals in medical settings. This method has a high fluorine concentration and must be used by a professional.

A silver ammonium fluoride (SDF) solution is a topically applied solution containing fluoride ions, silver ions and ammonia, which is applied to the tooth surface and then mixed with hydroxyapatite [ Ca ]₁₀(PO₄)₆(OH)₂]Reaction takes place, mainly calcium fluoride (CaF) is produced₂) And silver phosphate (Ag)₃PO₄). Calcium fluoride is unstable and forms a fluorapatite [ Ca ] which is more acid-resistant than hydroxyapatite₁₀(PO₄)₆F₂]. Silver phosphate exerts an antibacterial function through the action on amino acid and nucleic acid of a bacterial thiol group, and reacts to generate hydroxyl to neutralize hydrogen ions, so that the acidic environment is changed, and related researches are being intensively carried out internationally.

No significant adverse reaction is found in the clinical research of the silver ammonium fluoride. Only one disadvantage is that silver ammonium fluoride darkens teeth when used to treat dental caries. But provides a simple and safe treatment means with other means for treating children decayed teeth, in particular to clinically incompatible means for treating children decayed teeth, such as sedation or general anesthesia, and silver ammonium fluoride. If a child develops a cavity, silver ammonium fluoride can treat the cavity if it is so severe that it causes pain or infects other cavities, while also ensuring that the child has a good experience of dental treatment.

The current reports on the preparation process of material silver ammonium fluoride for treating dental caries are as follows:

the preparation and measurement of a cariostat-silver ammonium fluoride solution were first reported in 1982 Pengmei pharmaceutical bulletin (17 vol. 7 399-400).

The main principle is as follows: the silver oxide reacts with ammonium fluoride and ammonia water to generate the silver ammonium fluoride.

The reaction equation is: ag₂O+2NH₄F+2NH₃·H₂O→2Ag(NH)₃F+3H₂O

The specific method comprises the following steps: putting ammonium fluoride into a 250ml flask, adding a small amount of water to dissolve the ammonium fluoride, gradually adding silver oxide, then dropwise adding ammonia water, continuously shaking until the black silver oxide is basically dissolved, filtering, adding distilled water to a sufficient amount, and uniformly mixing to obtain the black silver oxide.

The process has the following disadvantages:

1) the process has two disadvantages due to the addition of excessive ammonium fluoride during feeding: firstly, the solution system is unstable and can separate out crystals in the storage process. Secondly, the waste of raw materials is caused.

2) The process directly adds silver oxide solids, and raw materials may bring in uncontrollable impurities, so that the impurities in the final product are difficult to control.

3) The process has no refining process and cannot remove excessive ammonium fluoride, excessive ammonia and excessive silver. Can produce explosive by-product Ag after long-term storage₃N。

In the existing preparation process of silver ammonium fluoride, silver oxide or silver carbonate and hydrofluoric acid or ammonium fluoride are adopted, and a closed system carries out reflux reaction for 2.0h, 1.0h and 3.0h at 60 ℃, 80 ℃ and 120 ℃ respectively under the condition of excessive ammonia water until the pH of the solution is adjusted to 6 by hydrofluoric acid and no precipitate is generated.

The process has the following disadvantages:

1) the process adopts a closed system, and excessive ammonia cannot be removed in the reaction process. When the reaction solution is refluxed at 120 ℃, silver ions which are not combined into silver ammine complex ionic state in the reaction solution can be converted into silver oxide under alkaline condition, and further explosive by-product silver nitride can be generated under the condition of excessive ammonia.

2) The process uses hydrofluoric acid or ammonium fluoride (ammonium fluoride is converted into hydrogen fluoride to participate in reaction under a closed heating system), is not beneficial to large-scale process control, and has higher requirements on corrosion resistance and safety protection of equipment.

3) The heating conditions of the process are that a closed system is subjected to reflux reaction for 2.0h, 1.0h and 3.0h at the temperature of 80 ℃ and 120 ℃, the reaction conditions are harsh, the reaction is not easy to reproduce, and qualified products cannot be prepared through multiple verification.

In consideration of the wide clinical application prospect of the silver ammonium fluoride, the preparation process of the silver ammonium fluoride is necessary to be researched, an economic, environment-friendly and stable production method is found, and the key problem in the domestic substitution process of key medical instruments is solved as soon as possible.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides an economical, environment-friendly and stable preparation method of silver ammonium fluoride used as a material for treating dental caries. The preparation method comprises the following steps:

1) preparing silver oxide:

and (3) dissolving a certain amount of silver nitrate solid in ultrapure water, and then dropwise adding a proper amount of sodium hydroxide solution, wherein the reaction is finished when a large amount of precipitate is in the reaction solution. Filtering the precipitate to obtain a filter cake which is silver oxide precipitate, and washing the silver oxide precipitate for multiple times by using ultrapure water until the silver oxide precipitate is neutral, wherein nitrate ions are less than one ten-thousandth.

The reaction equation is: 2AgNO₃+2NaOH＝Ag₂O↓+H₂O+2NaNO₃

The control key points are as follows:

the NaOH has high purity, the purity of more than 99.15 percent contains sodium carbonate impurities as little as possible, and the generation of silver carbonate to generate a silver fulminate byproduct in the next reaction process is avoided: 4Ag₂CO₃+4NH₃→2Ag₂C₂N₂O₂+6H₂O+4Ag+O₂

②Ag₂O is washed and NO NO is not present₃ ^-Because if NH is present in the solution₄NO₃Silver fulminate may be formed when the pH of the solution is adjusted to be acidic.

2) Preparation of silver ammonium fluoride (SDF) solution

Silver oxide: ammonium fluoride: and preparing the silver ammonium fluoride by using ammonia water with the mass ratio of 1:2: 2.3-1: 2.2:2.5, preferably 1:2: 2.3. The excessive ammonia water can ensure the full progress of the reaction, and the excessive ammonia water can be removed in the refining process.

Taking silver oxide, adding a certain amount of ultrapure water, adding a certain amount of ammonium fluoride solid while stirring to obtain a turbid liquid, slowly dropwise adding ammonia water, controlling the reaction temperature to be 5-25 ℃, and filtering after the solution is clarified to obtain a filtrate, namely an ammonia silver fluoride solution.

Ag₂O+2NH₄F+2NH₃·H₂O→2Ag(NH₃)₂F+3H₂O

Further, the method also comprises the following steps:

3) and (3) refining: gradient heating

The reaction temperature is 50-60 ℃, the heating time is more than or equal to 1.5h, the ammonia concentration is 7.5-10.55% (w/v), and the pH is less than or equal to 11.8; the purpose is to remove part of the excess ammonia by evaporation, taking advantage of the reduced solubility of ammonia at the heating temperature.

The reaction temperature is 70-80 ℃, the heating time is more than or equal to 1.0h, the ammonia concentration is 7.5-10.55% (w/v), and the pH is less than or equal to 11.8; the aim is to decompose the excess ammonium fluoride. The equilibrium equation is:

the excess ammonia will be volatilized or complexed with heating, and the hydrogen fluoride formed if decomposed will be substantially neutralized by the base, or will be in the form of associated molecules with the NH₃、H₂O forms an association molecule.

The reaction temperature is 96-101 ℃, the heating time is more than or equal to 3.0h, and the ammonia concentration is 7.5% ~ up to9.07 percent and pH less than or equal to 10.0. The purpose is to remove unreacted silver. Because the boiling point of the silver ammonium fluoride (SDF) solution is 101-103 ℃, excessive ammonia is removed, and when the temperature of the solution is close to 101 ℃, Ag in silver-ammonia complex ions⁺And NH₃The association between the Ag and the Ag in the silver-ammonia complex ion state is weakened, and the reaction solution is not combined into the Ag in the silver-ammonia complex ion state⁺The following reaction equilibrium exists:

2Ag⁺+2OH^-→Ag₂O+H₂o under heating and alkaline conditions

A first part: ag₂O→Ag+O₂Precipitating as simple substance silver;

a second part: ag₂O+2NH₃→2Ag₃N (explosive by-product) +3H₂O

Preferably, the gradient heating: the internal temperature is 56 ℃, and the heating is carried out for 1.5 hours; heating at an internal temperature of 72 ℃ for 1 hour; the internal temperature is 96-101 ℃, and the heating is carried out for 3 hours.

The solubility of ammonia is different at different temperatures, excessive ammonia is continuously removed in the gradient heating process, and the second part of explosive by-product Ag can be avoided₃And (4) generating N.

The evaporation capacity of the solution in the whole refining process is not less than 5.6%.

4) Filtering and adjusting pH

Filtering the refined silver ammonium fluoride solution by using a 0.22 mu m microporous filter membrane, and adjusting the pH of the filtrate to 10.0-10.2 by using ammonia water. The product has 24.0-27.0% (w/v) of silver, 5.0-6.0% (w/v) of fluorine and 7.5-11.0% (w/v) of ammonia, and no precipitate is generated when the pH value of the solution is adjusted to 6.0 by 1mol/L nitric acid, namely the product is a material for treating dental caries.

The method takes silver nitrate, sodium hydroxide, ammonium fluoride and ammonia water as raw materials, provides a new idea for preparing the ammonia silver fluoride solution, realizes refining of the preparation process by gradient heating, removes excessive raw materials, and avoids generation and precipitation of byproducts.

Firstly, silver nitrate reacts with high-purity sodium hydroxide to prepare silver oxide precipitate, then the silver oxide is mixed with ammonium fluoride and ammonia water, and the material which is stable in long-term placement is prepared through a gradient heating refining process.

Compared with the prior art, the patent has the following advantages:

1) this patent adopts half airtight system, and in the gradient heating process, ammonia is evaporating the reduction constantly, and until reaction temperature be 96 ~ 101 ℃ after 3 hours, the concentration of free ammonia is extremely low, so avoided the formation of explosive accessory substance, can reach safety in production.

2) The method adopts ammonium fluoride in a semi-closed system and an alkaline environment, and hydrogen fluoride formed by decomposition is basically neutralized by alkali or is combined with NH in the form of associated molecules₃、H₂O forms association molecules, has low requirements on corrosion resistance and safety protection of equipment, and is safe and environment-friendly.

3) The patent is carried out under a non-closed system, and comprises the following steps: the reaction temperature is 50-60 ℃, and the heating time is more than or equal to 1.5 h; and a second stage: the reaction temperature is 70-80 ℃, and the heating time is more than or equal to 1.0 h; and a third stage: the reaction temperature is 96-101 ℃, the heating time is more than or equal to 3.0h, the evaporation capacity of the solution in the whole refining process is not less than 5.6 percent, qualified products can be prepared, and the method is more economical and stable.

The preparation process is economic, environment-friendly and stable, and can prepare the silver ammonium fluoride solution which has less impurities and byproducts and is stable after long-term storage. Impurities brought into the raw materials can be controlled by self-made silver oxide, and the newly prepared wet silver oxide can increase the reaction rate with ammonium fluoride and ammonia water, so that the reaction is accelerated. NaOH is pure enough, sodium carbonate impurities are controlled as much as possible, and silver carbonate impurities are avoided. The gradient heating realizes the refining of the preparation process, removes excessive raw materials and avoids the generation of by-products

Detailed Description

In order to describe the present invention more specifically, the following detailed description will explain the technical solution of the present invention in conjunction with the specific embodiments. Example 1: