Silver Diamine Fluoride

Dental caries is one of the most prevalent chronic diseases in the United States and worldwide. 1-3 In the United States, decreasing levels of caries prevalence and untreated tooth decay have been reported among children and adolescents, but caries prevalence has remained relatively unchanged among adults and older adults, according to national oral health surveillance data. 4

Long-term improvements in caries prevalence and reduced caries severity have been associated with water fluoridation 5 and the use of fluoride-containing oral care products. 6 Nevertheless, caries prevalence levels in the United States remain persistently high among vulnerable patient populations and patients with high caries risk factors, 4 and worldwide an estimated 3 billion children and adults are affected by untreated caries. 7 To address this common yet preventable disease, researchers are continuing to investigate the effectiveness of fluoride-containing materials in arresting carious lesions and preventing future development of caries lesions, including an increasing focus on silver diamine fluoride (SDF).

Silver diamine fluoride is a colorless or blue-tinted liquid with a pH between 10 and 13, which is comprised of approximately 24.4% to 28.8% (weight/volume) silver, 5.0% to 5.9% fluoride and 8.0% ammonia. 8-12 The U.S. Food and Drug Administration (FDA) has classified SDF as a Class II medical device, and it is cleared for use in the treatment of tooth sensitivity, which is the same type of clearance as fluoride varnish, and must be professionally applied.

Although some additional products are commercially available in other countries, as of September 2023, Advantage Arrest™ (Elevate Oral Care, L.L.C.) and Riva Star™ (SDI, Inc.) are the only commercially available SDF products for dental use in the U.S. 13 In 2016, Advantage Arrest™ was designated by the FDA as a breakthrough therapy for the arrest of caries in children and adults; this designation indicates that a therapy has the potential to address a currently unmet medical need. 14 Although use of SDF has been reported in caries control and management, it is not specifically FDA-labeled for use for this indication (i.e., “off-label use”). When applied to a carious lesion, SDF has also been shown to decrease caries risk of adjacent tooth surfaces. 15 SDF has also shown efficacy in management of root caries in the elderly. 16-20 It has additional applicability as an interim approach for managing caries in individuals currently unable to tolerate more involved dental treatment, including special needs populations. 21-23

SDF offers the possibility of arresting or slowing progression of caries lesions in primary and permanent teeth without removal of sound tooth tissue. 24, 25 In addition, SDF appears to promote remineralization of demineralized dentin. 24, 26 The effectiveness of treating carious lesions with SDF is demonstrated by the increase in mineral density of the previously carious tissue. 27 The main benefits of SDF are: control of pain and infection, ease of application, low cost, minimal application time and training required, and as a noninvasive method of caries arrest. 28 Single application of SDF has been reported to be insufficient for sustained benefit and requires reapplication. 29 Its potential downsides include a reportedly unpleasant metallic taste, potential to irritate gingival and mucosal surfaces, and the characteristic black staining of the tooth surfaces to which it is applied. 30 Occasional diarrhea and stomach ache were also reported in a clinical trial of pediatric patients, but the events were mild in severity and resolved within two days of reporting. 31

SDF may be a preferred option to arrest caries in deciduous teeth, older individuals, when physical limitations do not allow more extensive treatment or when access to conventional restorative techniques, such as resin composite or amalgam restorations, are not available. Because conventional caries treatment in young children and/or individuals with special care needs may require advanced sedation techniques, SDF may be a viable treatment option when sedation is either not desirable or available.

SDF may have utility in the situation of multiple caries lesions that cannot be treated by conventional means in one single visit. It allows for stabilization of the disease prior to proceeding with conventional restorative treatment. SDF treatment has also been shown to be as effective in stopping caries progression as atraumatic restorative treatment (ART), while being up to twenty times less costly. 29

SDF is an alkaline solution with 38% weight/volume Ag(NH₃)₂F. The silver functions as an antimicrobial, while fluoride is present in sufficient concentration to promote remineralization; 32-34 the ammonia (NH₃) present stabilizes the solution. 29 When in contact with the tooth, the diamine-silver ion complexes react with hydroxyapatite forming silver phosphate (Ag₃PO₄) and silver oxide (Ag₂O). 28 While SDF inhibits the collagenolytic enzymes that break down exposed dentin organic matrix, ionic silver acts as an antibacterial by disrupting membranes, denaturing proteins, and inhibiting DNA replication. 29 Antibacterial mechanisms of SDF can also be attributed to the formation of organometallic complexes inside the bacterial cell. Organometallic complexes can: (a) deactivate enzymes by blocking the electron transport system in bacteria, resulting in bacterial cell death; (b) induce rupture of the bacterial cell; and (c) interact with the DNA of bacterial cells resulting in mutation and death. 33

The formation of silver compounds results in striking tooth structure color change, 32 which is the main adverse effect following SDF treatment. With respect to patient concerns about fluoride, there is less fluoride content in the amount of SDF used to treat a tooth with caries than in fluoride varnish. 35 The AAPD reports no known systemic or serious adverse effects reported for SDF when used according to manufacturer directions. 23

SDF has been cleared by the FDA as a dentin desensitizing agent, 29 and various studies support the effectiveness of SDF in treating tooth sensitivity. 36, 37 When applied to areas with sensitive dentin surfaces, a layer of silver and dentin organic matrix protein conjugates forms. 29 This squamous layer formed on the exposed dentin surface partially closes the exposed dentin tubules. 29

The caries process commonly occurs through exposure to dietary sugars and complex bacterial interactions in the oral cavity, including biofilm formation, bacterial metabolism, frequent acid production, tooth mineral demineralization, and organic matrix degradation. 38-42 The cariogenic process is initiated by an imbalance in the demineralization and remineralization equilibrium, induced by the presence of acid-producing and acid-tolerant bacteria, shifting to a lower pH, resulting in loss of tooth minerals. 42 Therefore, it is important to enhance the protective and minimize the pathologic factors associated with tooth decay. Current strategies for caries management focus on the individual’s risk assessment and establishment of preventive and/or restorative treatments. 43

Caries progression occurs by simultaneous demineralization of enamel and dentin and degradation of the organic matrix. 41 Once the caries lesion is developed, treatment options include restorative and non-restorative measures. 43 Nonrestorative approaches may be invasive, such as preventive resin restorations; or noninvasive, such as SDF, fluoride therapy, or sealants.

Although most studies reported caries arrest in deciduous teeth, the proposed mechanisms by which SDF may help arrest caries would likely apply for permanent teeth. 42

In 2018, the ADA Center for Evidence-Based Dentistry conducted a systematic review and network meta-analysis 44 informing a clinical practice guideline 42 on nonrestorative treatments for carious lesions. The expert panel formulated 11 clinical recommendations, each specific to lesion type (i.e., cavitated, noncavitated), tooth surface (i.e., coronal, root surface [in adults]) and dentition (i.e., primary or permanent). The panel provided recommendations for the use of the most effective treatment options, which included 38% SDF, along with other topical fluoride products. The expert panel recommended that clinicians prioritize the use of 38% SDF solution biannually to arrest advanced cavitated carious lesions on coronal surfaces of primary teeth. 42 The expert panel extrapolated these results to recommend that clinicians could also use biannual application of 38% SDF solution to arrest advanced cavitated lesions on coronal surfaces of permanent teeth. Biannual application of 38% SDF for advanced cavitated lesions may be relevant if access to care is limited, for uncooperative patients, or for patients when general anesthetic is not considered safe. 42

A 2017 guideline 45 from the American Academy of Pediatric Dentistry (AAPD) made a conditional recommendation (based on low-quality evidence) for the use of SDF in the management of caries in children and adolescents, including those with special health care needs. Panel members were confident that, given its low cost and the disease burden of caries, the benefits of SDF application in the target populations outweighed the undesirable dark discoloration of carious dentin treated with SDF.

According to an umbrella review, application of 38% SDF prevented root caries in adults with success rates 72% higher than a placebo treatment. 46 The same review reported a prevented fraction for successful root caries arrest, between 100% and 725% higher as compared to a placebo treatment. 46 Another study indicated that application of 38% SDF in combination with oral health education was the most effective method for preventing root caries in adults. 47

The disadvantages of SDF include potential pulpal and oral soft tissue irritation and dental staining. Attention is needed during the application to avoid contact of the solution with the gingiva, since it may cause irritation. 27 Mature and sound enamel is not stained, unless there is any superficial defect, such as hypomineralization or carious/demineralized or immature enamel, where the porosities allow silver ions to penetrate. 48

Further restoration of the arrested caries lesion may be needed to recover form and function of a cavitated tooth, which will also diminish tooth discoloration. 49 There is limited evidence on the adhesive performance of traditional restorative options, such as resin composite and glass ionomer cement (GIC), following caries arrest with SDF. 49 SDF treatment does not seem to impair GIC bonding. 50, 51

A 2019 systematic review found that once-yearly SDF application was more effective in preventing caries than more frequent application (i.e., 2 to 4 times yearly) of fluoride varnish. 48 Whereas when compared to occlusal sealants, SDF was only more effective in preventing caries if continuously applied. 48