Managing Caries With Silver Diamine Fluoride

It should be noted that although this solution is commonly called "silver diamine fluoride," that is a misnomer. The compound does not contain an amine group (-NH₂) but rather an ammine group (NH₃); therefore, it would more accurately be referred to as "silver diammine fluoride."³ However, "silver diamine fluoride" is the term that is conventionally accepted throughout the dental literature.

After the first US Food and Drug Administration (FDA)-approved SDF solution (Advantage Arrest^®, Elevate Oral Care) was made commercially available in the United States for the treatment of sensitivity, other manufacturers released their own solutions. SDF has been made available in 10%, 30%, and 38% concentrations; however, 38% solutions have been demonstrated to be the most effective.⁴ The specific percentage of fluoride ions in the solution varies based on the manufacturer.

SDF differs from other fluoride-containing products because it penetrates the enamel and dentin, and 2 to 3 times more fluoride is stored in the tooth. This phenomenon enables the tooth to become a fluoride reservoir.⁵ Moreover, SDF is an alkaline solution, so its neutralizing action may also contribute to its overall antimicrobial effect.⁶ SDF contains both silver and fluoride ions. The high concentration of fluoride ions in SDF promotes remineralization and acts as an antimicrobial; however, the silver ions also act as a potent antimicrobial.⁷ The use of silver as an antimicrobial agent is not a new concept. In fact, silver was used in medicine long before the advent of antibiotics. Silver's mechanism of action is that it blocks the respiratory enzymes of microorganisms.⁸ In addition to these caries-arresting properties, SDF can also reduce dental sensitivity by occluding the dentinal tubules.

SDF demonstrates a particularly useful property that has been referred to in the literature as the "zombie effect." In this phenomenon, bacteria first consume the SDF and then die, but because silver still remains in the dead bacteria, when living bacteria come to eat the dead, the silver-laden dead bacteria cause the deaths of the living bacteria.⁹

A systematic review of the literature regarding the application of SDF determined that biannual application is more effective than annual application.¹⁰ In some instances, a single application of SDF may be inadequate, and a second application is required. It is also typically more effective when used on anterior teeth rather than posterior ones.¹⁰ In addition, if pulpal involvement is suspected, SDF should not be used.¹⁰ SDF's efficacy is independent of the extent of the carious lesion; therefore, it is as effective in an initial carious lesion as it is in a cavitated lesion.¹¹

At the time of application, patients and/or parents should be forewarned of SDF's bitter taste, which is a result of the ammonia in the formulation. Ammonia adds necessary stability to the formulation and increases its pH. One technique that can be used to circumvent the unpleasant taste and promote compliance with the treatment is to soak a piece of gauze in mouthwash and place it over the patient's tongue prior to placement of the SDF. This can help to conceal or at least mitigate the unpleasant taste of the formulation.

Because SDF has the potential to stain surfaces, such as skin, nail beds, countertops, and clothing, clinicians should be meticulous in preventing untoward staining by placing a bib over the patient, placing petroleum jelly on the patients' lips, and wearing gloves the entire time that SDF is being handled. An ideal time to place SDF is perhaps at the end of a restorative dental appointment but before the rubber dam or isolation device is removed; isolation can help to prevent improper placement of SDF.

The amount of  SDF needed to treat a lesion is minimal. As little as one to two drops can be used to treat up to five lesions.⁹ However, it should be noted that one drop contains approximately 2.24 mg of fluoride, which is less than the approximately 11.3 mg of fluoride that is contained in a usual dose of 5% NaF varnish.¹² When SDF is applied, CDT code D1354, "interim arresting medication application," should be used. This code should be used for each tooth that is treated.

Although SDF is capable of arresting carious lesions, if a lesion has resulted in a loss of tooth structure extensive enough to structurally compromise the tooth, the tooth may still require a final restoration. Special care should be taken if  SDF is being placed close to the pulp. In situations in which there is little remaining dentin to protect the pulp, SDF may be cytotoxic to fibroblasts¹³; however, more research is needed on this topic.

Clinicians should inform the patient and/or caregiver that SDF will turn the lesion a brownish-black color and may also stain the surfaces of demineralized, hypomineralized, and possibly, immature enamel but will not stain intact noncarious enamel. Furthermore, the treated area does not immediately demonstrate the full extent of the staining but rather the treated caries darkens over the course of 2 to 3 weeks.⁴ When SDF-treated surfaces are exposed to light, the area turns dark. Using a curing light while restoring an SDF-treated tooth will darken the dentin immediately.

Fortunately, many carious lesions already have a yellow, brown, or even slightly black discoloration. Once that observation is presented to patients, they may be more amenable to the application of SDF. In fact, in some instances, the application of SDF does not result in a color that is substantially worse than that of the existing lesion. Engaging in a written informed consent process prior to SDF application may be a useful tool to help facilitate communication with patients.

The application of potassium iodide following SDF treatment (eg, Riva Star^®, SDI Limited) absorbs excess silver and reduces discoloration. In a review of the literature, multiple studies examined the stain reduction effect of potassium iodide following SDF treatment.¹⁴ Most concluded that potassium iodide application after SDF treatment significantly reduced tooth staining; however, Zhao and colleagues reported reduced marginal staining following glass ionomer restoration of the SDF-treated dentin. When silver nanoparticles were used, decreased staining was reported. The decreased staining associated with silver nanoparticles is due to the size of the nanoparticles. Unfortunately, nanoparticles are unstable, and they agglomerate and increase in size. Potassium iodide should be used with caution in pregnant women due to the risk it may pose to fetal thyroid development.⁹

Interestingly, when SDF is used for caries management, it is being used off-label. SDF was approved by the FDA in 2014 as a desensitizing agent—not as a drug for caries treatment. It is not uncommon, however, for drugs or devices to be used off-label in appropriate ways. For example, benzodiazepines and tricyclic antidepressants are often used off-label to treat burning mouth syndrome.

When used to treat sensitivity, SDF may present a challenge to the subsequent bonding of an adhesive restoration, such as a direct resin composite restoration or ceramic onlay. SDF occludes the dentinal tubules, which is beneficial in reducing sensitivity but may prevent an adhesive bonding agent from penetrating into the tubules.⁴ Penetration of the adhesive into the tubules is necessary to achieve micromechanical retention to dentin. To determine if placing a bonded restoration over a surface treated with SDF results in adverse clinical outcomes, more clinical studies are needed. The results of laboratory studies that have investigated SDF's effect on bond strength are somewhat equivocal. Although some studies demonstrate that SDF decreases shear bond strength,^15,16 others have shown that it has no adverse effect on bond strength.^17,18

Regardless of SDF's need for caution and further study, it has well-established indications and is a valuable resource for clinicians to have at their disposal. SDF can be utilized for the treatment of multiple carious lesions, to slow caries progression, to treat emergencies, to provide treatment to patients who cannot tolerate lengthy restorative procedures, and more. For the patient in the following case report, SDF was used to slow the progression of caries along the palatal margin of a recently placed crown.

A 59-year-old male patient who was at high risk for the development of caries presented for routine restorative dentistry. During the examination, a cavitated carious lesion was detected on the palatal root surface of tooth No. 5 (Figure 1). A zirconia crown had been placed on the tooth within the past 12 months, and at that time, there was no remaining root caries. The patient was presented with several treatment options, which included restoring the carious lesion with a resin-modified glass ionomer or composite resin or arresting it with a biannual topical application of SDF. After the risks and benefits of each treatment were thoroughly discussed with the patient, he elected biannual topical application of SDF.

The first application of SDF was performed during the same appointment. After an isolation device (Isolite^®, Zyris) was placed, the lesion was dried, and a drop of the SDF solution (Advantage Arrest^®, Elevate Oral Care) was applied with a microbrush. The solution was allowed to sit for at least 1 minute. Six months later, the patient returned, and a second application of SDF was performed. This time, the SDF was applied after a restoration had been placed on an adjacent tooth under rubber dam isolation (Figure 2 and Figure 3). Rubber dam isolation offers the advantage of greater control over placement during SDF application.

Long-term clinical data have demonstrated that SDF is an effective tool for arresting caries. To determine the most optimum application intervals of SDF, more research is needed; however, the current data seem to suggest that biannual application may be ideal. The manufacturer's instructions should always be followed to guide the application of SDF. Although SDF may cause the staining of carious lesions, these lesions are typically already discolored, and the patient may not mind if the lesion isn't visible during smiling. More clinical studies are needed to determine if SDF affects the success and survival rates of adhesively bonded restorations.

Melissa Seibert, DMD, MS
Creator and Host
Dental Digest Podcast
US Air Force Dentist
Lackland Air Force Base
San Antonio, Texas

John O. Burgess, DDS, MS
Diplomate
Federal Services Board of General Dentistry
Director of Clinical Research
Clinical Research Professor
School of Dentistry
Louisiana State University
New Orleans, Louisiana