Does Silver Diamine Fluoride permanently stain teeth?

October 06, 2022

Dental caries is the most prevalent oral condition globally. It occurs when the microbes release their acidic secretions facilitated by sugar consumption that leads to weakening of the tooth structure and subsequently rendering it prone to decay. Presence of systemic conditions can make the teeth even more vulnerable to caries. Owing to the multifactorial cause of caries and its global prevalence, dental researchers and practitioners have come up with a plethora of treatment modalities for tooth decay.

Ways to treat dental caries

Treatment options can focus on either elimination of the decayed structure and restoring it with biocompatible dental cements, remineralization of the tooth structure or stopping the spread of the dental decay. Advancing technologies has led to treatment options focus on minimal invasiveness with maximal efficacy. One such treatment modality the focuses on the cessation of the progression of dental caries is done with the help of Silver Diamine Fluoride (SDF).

What is SDF (Silver Diamine Fluoride)?

Back in the 19th century, silver nitrate was used to halt the caries progress. However, its efficacy and safety concerns led to its decline and was eventually discontinued in the 1950s. Later, in the late 1960s, silver came back as a therapeutic agent for the cessation of caries in the form of SDF in Japan. It took a lot of experimental studies to deem SDF fit for caries progression. Its use is now particularly focused in primary or deciduous teeth.

SDF is a colourless, odourless solution containing enormous fluoride concentration (38% ; 44,800 ppm). As the name suggests, the solution contains silver and fluoride bonded with ammonia chains. Silver works by breaking the cell wall of the pathogenic microbes and thereby disrupting their activity. These killed bacteria further contribute by killing those living bacteria that come in contact with it (zombie effect).

The inhibition of the carious process occurs when SDF works on a tissue called collagen present in the dentin. During the carious process, the collagen's degradation by certain enzymes and proteins leads to further degradation of tooth structure. SDF works by inhibiting the effect of these enzymes and proteins.

Silver ions also help in decreasing tooth sensitivity. The weakened tooth structure can be strengthened again with fluoride present in SDF.

SDF has been immensely successful in arresting the spread of caries. The chairside time for the procedure does not exceed 15 minutes and patients also get a painless treatment. Only a drop of the solution contains 2.24 mg of fluoride that helps in achieving the treatment goals. However, precautions are to be taken when the dentist carries this one drop on to the tooth surface. This is because a drop of SDF can permanently leave a discolored spot on the cloth, can cause irritation if it is dropped on the gingiva and may lead to minor burns on the skin for 48 hours.

One of the most discomforting outcomes of SDF application is when it leads to a blackish discoloration of the tooth. Parents and mature adult patients are warned beforehand about this. The discoloration occurs because silver ions react with phosphate groups of the carious tooth structure, thereby forming silver phosphate. This compound turns black when exposed to sunlight. The darkest shade is visible after 6 hours of application.

How to reduce discoloration caused by SDF (Silver Diamine Fluoride)?

One of the methods that can reduce the extent of discoloration is application of potassium iodide salt. It has been used from concentrations of 0.7% to 20% in order to reduce the black staining of the tooth. Even though this technique is effective in preventing discoloration caused by SDF, researchers are still divided on some important aspects regarding potassium iodide. Some believe that potassium iodide may inhibit the caries inhibiting effect of SDF. Some others believe that KI does not have a long-term effect.

Following SDF application, the application of tooth-colored cements like resin-modified glass ionomer cement (RMGIC) and composite resin can help in masking the tooth's discoloration. Questions have risen that suggest that KI may interfere the bond between the SDF treated tooth and the applied cement. It is postulated the application of KI may lead to the formation of silver iodide, which may reduce the effectiveness of silver ions that were originally meant to kill microbes.

Even though SDF has a promising mechanism of action with impressive results, the fact that it discolours the tooth might not be acceptable to all patients. Potassium iodide does have potential to reduce this blackish discoloration but the lack of an established clinical protocol for its use leaves dental surgeons perplexed.

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