CN-111698996-B - Silver fluoride solutions for dental compositions

Abstract

The invention relates to an aqueous silver fluoride (AgF) containing solution having a pH of 4.0-5.3.

Inventors

• P Perez
• A. Target
• M.LUO

Assignees

• SDI有限公司

Dates

Publication Date

20260512

Application Date

20190207

Priority Date

20180212

Claims (1)

1. 1. An aqueous silver fluoride (AgF) solution having a ph of 4.0-5.3, wherein the solution is formulated as a dental solution and is stabilised by an acid, the acid being nitric acid, the amount of silver fluoride in the aqueous silver fluoride solution being 38-50% w/v.

Description

Silver fluoride solutions for dental compositions Technical Field The present invention relates to a silver fluoride solution for use in dental compositions. Background Silver fluoride containing products have been known for many years to provide as a method of treating dental hard tissue. The solution is typically provided as an aqueous solution of silver fluoride (AgF), silver nitrate (AgNO 3), or Silver Diamine Fluoride (SDF). In particular, these products are known to protect affected teeth by killing caries-related bacteria and then promoting remineralization of demineralized collagen. In addition, these products can also be used to reduce tooth sensitivity by blocking movement of fluid through dentinal tubules. Silver fluoride containing products have the common disadvantage of changing the color of caries affected teeth to a permanently black hue due to oxidation of silver ions. Soft tissues of the oral cavity (gums, cheeks, lips, etc.) also darken if contacted with a solution containing silver fluoride, although this is only temporary and gradually disappears within a few days thereafter. One method of alleviating black staining is to use a silver fluoride containing product with a subsequent iodide salt containing solution that readily reacts with free silver ions to form a water insoluble, creamy silver iodide salt when applied immediately after the silver fluoride containing solution. Following this treatment method, the caries lesions will now appear pale brown (rather than black) and other dentinal tissue (non-caries, gums, etc.) will not change when excess silver iodide salt is rinsed away. Silver fluoride-containing solutions generally exhibit poor stability upon storage for the following reasons. (1) AgF solutions tend to precipitate out of solution upon storage. The sediment tends to form a layer on the inner surface and/or settle to the bottom of a storage container (e.g., bottle). Thus, a decrease in the concentration of soluble ions results in a decrease in the effectiveness of dental treatment. (2) The AgF solution may be stabilized by adding ammonia to form Silver Diammine Fluoride (SDF). Ammonia combines with silver ions to produce what is known as silver diammine ions Ag (complex ions of NH 3)2]+. This is a reversible reaction but the complex is very stable however, ammonia-containing compositions are difficult to store due to the high volatility of ammonia, bottles and containers tend to lose ammonia on storage, especially at high temperatures, resulting in the remaining AgF solution becoming unstable (resulting in precipitation). Ammonia used to prepare stable silver complexes causes pH to rise to dangerous levels (pH > 10) in many commercial products. Moreover (due to the volatility of ammonia) it is difficult to store for long periods of time, unfortunately, more stable SDF solutions are very irritating to the oral soft tissues and can lead to chemical burns if left in contact for prolonged periods of time. Disclosure of Invention It would be advantageous to develop a storage-stable silver fluoride-containing solution that exhibits caries inhibition and tooth desensitization while being gentle to the soft tissues of the oral cavity. Suitable systems are based on essentially aqueous silver fluoride solutions which are stable in the pH range 4-5.3. The stabilized silver fluoride solutions of the present invention are also suitable for use with solutions containing iodide salts to reduce staining as described above. Detailed Description To reduce the pH of the SDF solution, ammonia was not used, resulting in an aqueous silver fluoride solution. Freshly prepared aqueous 38% w/v silver fluoride solutions typically have a pH of 6.2 to 6.4, which is unstable on storage and silver begins to precipitate out of solution. Stability of the solution is achieved by adjusting the pH of the solution with an acid to a pH of 4.0-5.3. A pH below 4.0 is considered unsuitable because it may cause chemical burns and irritation due to the corrosiveness of the acidic solution. pH values above 5.3 are unstable for long term storage and silver precipitates from solution. Nitric acid is the preferred compound for use as the acidic pH adjustor, however other organic or inorganic acids that form soluble silver salts may also be used. This avoids precipitation of insoluble silver salts as reaction products. Examples Three aqueous 38% (w/v) silver fluoride products were prepared, each solution exhibiting a different pH. The performance attributes of the products were tested and are detailed in table 1. TABLE 1 * Hydraulic conduction (Lp%) was used to determine the reduction in fluid movement through dentinal tubules (0% -no occlusion, 100% -complete occlusion, no fluid movement). Fluid movement through dentinal tubules may be responsible for dental hypersensitivity and therefore Lp% represents desensitization. The second application (potassium iodide solution) was used for all example products to test whether