Silver fluoride solution for dental compositions

Abstract

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

Description

Technical Field

[0001] This invention relates to a silver fluoride solution for use in dental compositions. Background Technology

[0002] Silver fluoride products have been known for many years as a method of treating the hard tissues of teeth. Solutions are generally provided as aqueous solutions of silver fluoride (AgF), silver nitrate (AgNO3), or diamine silver fluoride (SDF). Specifically, these products are known to protect affected teeth by killing caries-associated bacteria and then promoting the remineralization of demineralized collagen. Furthermore, these products can also be used to reduce tooth sensitivity by obstructing the movement of fluids through dentinal tubules.

[0003] Products containing silver fluoride share the common drawback of permanently discoloring teeth affected by cavities due to the oxidation of silver ions. Contact with solutions containing silver fluoride can also cause the soft tissues of the mouth (gingiva, cheeks, lips, etc.) to darken, although this is only temporary and gradually disappears over the next few days.

[0004] One method to alleviate black staining is to use a silver fluoride product followed by a solution of iodide salts. When applied immediately after the silver fluoride solution, the iodide solution readily reacts with free silver ions to form water-insoluble, cream-colored silver iodide salts. After this treatment, the carious lesions will now appear light brown (instead of black), and other dentin tissues (non-carious, gingival, etc.) will remain unchanged as the excess silver iodide salt is rinsed away.

[0005] Solutions containing silver fluoride typically exhibit poor stability during storage for the following reasons.

[0006] (1) AgF solutions tend to precipitate out of the solution during storage. The precipitate tends to form a layer on the inner surface and / or settle to the bottom of the storage container (e.g., bottle). Therefore, the decrease in the concentration of soluble ions leads to a reduction in the effectiveness of dental treatment.

[0007] (2) AgF solutions can be stabilized by adding ammonia to form diamminesilver fluoride (SDF). Ammonia combines with silver ions to form diamminesilver ions [Ag(NH3)2]. + The complex ion. This is a reversible reaction, but the complex is very stable. However, due to the high volatility of ammonia, ammonia-containing compositions are difficult to store. Bottles and containers are prone to ammonia loss during storage, especially at high temperatures, causing the remaining AgF solution to become unstable (leading to precipitation).

[0008] The ammonia used to prepare stable silver complexes causes the pH in many commercial products to rise to dangerous levels (pH > 10). Furthermore, (due to the volatility of ammonia) it is difficult to store for long periods. Unfortunately, the more stable SDF solution is highly irritating to oral soft tissues and can cause chemical burns if left in contact for extended periods. Summary of the Invention

[0009] It is advantageous to develop a storage-stable silver fluoride solution that exhibits caries inhibition and tooth desensitization while being gentle on oral soft tissues. A suitable system is based on a substantially aqueous silver fluoride solution that is stable in the pH range of 4–5.3.

[0010] The stable silver fluoride solution of the present invention is also suitable for use with solutions containing iodide salts to reduce staining as described above. Detailed Implementation

[0011] To lower the pH of the SDF solution, ammonia is not used, resulting in an aqueous solution of silver fluoride. Freshly prepared 38% w / v aqueous solutions of silver fluoride typically have a pH of 6.2–6.4, which is unstable during storage and silver begins to precipitate from the solution. Solution stability is achieved by adjusting the pH to 4.0–5.3 with an acid. pH values ​​below 4.0 are considered unsuitable because this can 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 will precipitate from the solution. Nitric acid is the preferred compound for use as an acidic pH adjuster; however, other organic or inorganic acids that form soluble silver salts can also be used. This avoids the precipitation of insoluble silver salts as reaction products.

[0012] Example

[0013] Three aqueous 38% (w / v) silver fluoride products were prepared, each solution exhibiting a different pH. The performance properties of the tested products are detailed in Table 1.

[0014] Table 1

[0015]

[0016] *Hydraulic conductance (Lp%) is 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 a cause of tooth sensitivity, therefore Lp% represents desensitization. The second step application (potassium iodide solution) was used on all example products to test whether different silver fluoride solutions would form silver iodide precipitates to block the dentinal tubules.

[0017] in conclusion

[0018] Example 1: Good storage stability, good dentinal tubule sealing, and biocompatible pH (no soft tissue irritation).

[0019] Comparative Example 1: Poor storage stability, good dentinal tubule sealing, and biocompatible pH (no soft tissue irritation).

[0020] Comparative Example 2: Good storage stability, good dentinal tubule sealing, and bioincompatible pH (soft tissue irritation).

[0021] Modifications and variations that are obvious to those skilled in the art are considered to be within the scope of this invention.

Claims

1. An aqueous solution containing silver fluoride (AgF) with a pH of 4.0-5.3, wherein, The solution was prepared as a dental solution and stabilized by an acid, namely nitric acid, in which the amount of silver fluoride in the aqueous solution was 38-50% w / v.

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