Silver diamine fluoride (SDF): its role in caries management Yasmi O Crystal Dental Update 2025 46:11, 1016-1022.
Authors
Yasmi OCrystal
DMD, MSc, FAAPD, Clinical Professor of Paediatric Dentistry Department of Paediatric Dentistry, New York University College of Dentistry, New York, USA.
Silver diamine fluoride (SDF) combines the antibacterial properties of silver and the remineralizing actions of fluoride in an alkaline solution that creates an unfavourable environment for collagen degradation. Clinical trials have proven the efficacy of SDF as a caries-arresting agent in primary teeth and root caries in the elderly. It is minimally invasive, inexpensive, safe and easy to apply, but a sign of arrest is the dark discoloration of the lesions where it is applied. SDF provides clinicians with a valuable additional tool in their armamentarium for caries management that aims to stop the disease process at the tooth surface, when traditional restorative therapy is not the best option, and when aesthetic results are not a concern.
CPD/Clinical Relevance: Silver diamine fluoride (SDF) provides clinicians with an additional valuable option for arresting dental caries as part of a comprehensive caries management plan when traditional restorative therapy is not the best option.
Article
Yasmi O Crystal
Despite advances in caries prevention and the reduction in caries prevalence as a result of the widespread use of fluoride in toothpastes and other delivery forms, dental caries continues to be a significant health problem for vulnerable populations worldwide. Increased consumption of sugar and processed carbohydrates are partly to blame for the persistent caries prevalence,1 and large numbers of individuals of all ages go untreated as they face barriers of cost and access to dental services. In addition, young children may also be unable to cope with undergoing conventional dental restorative treatment and are often treated with more risky procedures like sedation or general anaesthesia for the delivery of care. Special needs populations and the elderly may have additional co-morbidities that prevent them from receiving conventional dental treatment, which has a negative impact on their quality of life.2 Such circumstances highlight the need to find alternatives for caries control that are safe, effective, affordable and are easy to implement.
Silver compounds have been used as an alternative for restorative treatment for the management of caries for over 100 years.3 In the early 1970s, Drs Nishino and Yamaga in Japan developed a formulation combining silver with fluoride using ammonia to stabilize the solution.4 This product was 38% w/v of Ag(NH3)2F and it was recommended for the prevention and arrest of dental caries in children, prevention of secondary caries, and dentine desensitization. They stressed the downside of black dentinal staining and therefore recommended to confine its use to posterior teeth. Since then, other products have been developed in different countries and are available with concentrations of 12%, 30%, 38% and 40% SDF.
In the last 20 years, the rise in caries rates in young children have brought back interest in SDF as a viable alternative for caries control in groups with limited access to conventional dental care. Clinical trials encompassing over 4000 school children have proven SDF's efficacy, ease and safety for caries arrest on primary teeth.5 In 2014, the US Food and Drug Administration (FDA) approved SDF for use in the United States as a device for dentine desensitization in adults over 21 years of age and a 38% SDF product was introduced in the market (Advantage Arrest, Elevate Oral Care LLC, Florida, USA). Recognizing the need for innovative approaches to address oral health problems in vulnerable populations, the World Health Organization (WHO) published a report on Public Health Interventions against Early Childhood Caries in 2016 and concluded that silver diamine fluoride can arrest dentine caries in primary teeth and prevent recurrence after treatment (based on very low evidence). Subsequently, the American Academy of Pediatric Dentistry (AAPD) published guidelines for the use of SDF in 2017, which support the use of SDF 38% for the arrest of cavitated caries lesions in primary teeth as part of a comprehensive caries management programme (conditional recommendation based on low quality evidence).6 It is important to note that the use of SDF as a caries arrest medicament is strictly off-license (off-label) in the US, similar to the use of fluoride varnish (FV), which is also only licensed as a device for dentine desensitization but used widely as the standard of care for caries prevention. Guidelines from recognized organizations are important to legitimize and encourage the use of products like SDF, when used to benefit the patients in their individual circumstances, after a careful consideration of risks and benefits, and when compared to other more complicated procedures or no treatment.
Silver diamine fluoride 38%, as marketed in the USA, is a clear-blue tinted, light sensitive liquid with a slight ammonia odour that contains 24–27% silver, 7.5–11% ammonia, 5–6% fluoride (approximately 44,800 parts per million), <1% blue colouring and ≤62.5% deionized water. It is sold in 8 ml vials with approximately 250 drops of liquid, enough to treat 125 sites, with a site defined as up to 5 teeth. It is also marketed as a unit-dose ampoule with 0.1 ml per ampoule.7 A recent study cites that a drop of SDF, with an average of 32.5 microliters, would contain approximately 1.64 to 1.76 mg of fluoride, and 8.08 to 8.71 mg of silver.8 The use of SDF is contra-indicated in individuals with a silver allergy, and in teeth with suspected pulpal involvement.
The exact mechanisms of action of SDF continue to be under study. So far, we know that in dentine, silver acts as an antibacterial, interacting with bacterial metabolism which can inhibit bacterial growth. It also inhibits cathepsin action, therefore interfering with dentine collagen degradation. The principal silver precipitate is silver chloride (not silver phosphate), which could not contribute to significant hardening of dentine. Fluoride, however, enhances remineralization of enamel and dentine, and it also interferes with matrix metalloproteinases activity, inhibiting dentine collagen degradation. In addition, the synergistic combination of silver and fluoride in an alkaline solution (pH 9–10) results in an environment that is unfavourable for collagen enzyme activation, therefore preventing further collagen degradation.9
SDF is an effective dentine desensitizer and, as its application does not require caries removal, it does not require the use of local anaesthesia. It is easy to apply, inexpensive, minimally invasive and safe. It presents as a valuable tool for caries management in specific situations, as supported by the following evidence.
Current evidence to support SDF's potential for caries arrest and prevention
Systematic reviews of clinical studies of SDF uniformly support its efficacy for caries arrest on cavitated caries lesions in primary teeth over periods up to 36 months, and for arrest of root caries in elderly populations over periods up to 30 months. These systematic reviews combine studies that have different outcome measures, different times of follow-up, different application protocols, different SDF concentrations, and heterogeneous quality of each of the studies combined. Quality refers to adequate performance/reporting of randomization process, blinding, control groups, etc. When the studies are too heterogeneous to combine, the comparison has to be assessed as low quality evidence, as is the case in the strength of the recommendations of WHO and AAPD. There are just not enough similar, well conducted studies at the time of writing, where the combination of data would result in a strong recommendation for either caries arrest or prevention.
Caries arrest in primary teeth in children
One well conducted systematic review reports the overall percentage of active caries that became arrested over a period of 24 months to be 81% (CI 68–89%).10 These results are consistent with other studies which also report a wide range of confidence intervals. The following results from two recently published clinical trials that have not been included in previous systematic reviews are important to illustrate the potential clinical implications of the wide range of caries arrest. Fung et al studied arrest of caries on 788 3–4 year-old children followed for 30 months in 4 groups comparing 12% to 38% SDF applied annually and semi-annually:11 38% SDF was better than 12% SDF, and semi-annual applications worked better than annual applications. Of great interest to clinicians is that they report their results broken down into type of teeth (Table 1), where one can see the much greater rates of arrest in anterior teeth than in posterior teeth. Additional important results are that children with a higher visible plaque index score (VPI) had a lower chance to have their caries arrested with annual applications.
SDF 38% at 30 months
% Arrest
Annually
Semi-annually
All surfaces
70
76
Lower anteriors
93
92
Upper anteriors
77
86
Lower posteriors
53
62
Upper posteriors
42
57
Duangthip et al studied caries arrest on 309 3–4 year-old children followed for 30 months in three groups: SDF 30% applied annually, SDF 30% applied 3 times weekly at baseline, and 5% fluoride varnish (FV) applied 3 times weekly at baseline.12 Arrest rates seen in Table 2 report results in cavitated dentine caries and on small lesions (ICDAS 3–4). From these results they conclude that annual applications of 30% SDF are better than 3 times weekly at baseline for cavitated dentine caries lesions; but for moderate lesions, SDF 30% performs equally as well as 5% FV, and annual application works equally as well as 3 times weekly at baseline. They also report that lesions with visible plaque, posterior teeth and occlusal surfaces (as opposed to buccal or lingual surfaces) required a longer time to achieve caries arrest.
ICDAS 3–4. International caries detection and assessment system. Stages 3–4 refers to lesions in enamel only without distinct cavitation.
When looking at the overall arrest rates in both studies, SDF 38% arrested 70% of lesions when applied annually, compared to SDF 30% which arrested only 48%. These results suggest that the difference between these two SDF concentrations is important. Results of these two studies also suggest that SDF does not work all the time, and that plaque control is a crucial part of achieving caries arrest.
It is important to note that 5% FVs can achieve significant rates of arrest, especially when lesions are made cleansable,13 but SDF achieves effects of desensitization and arrest faster, often with only one application.12
In an early study included in most of the systematic reviews, Chu et al applied SDF with and without caries removal and concluded that caries removal is not necessary to achieve similar rates of caries arrest in young children, which adds to its ease of application.14
Caries arrest in permanent teeth in children
Only one study15 reports similar arrest rates on young permanent first molars to those reported on primary molars (70%), while another study reported arrest results to be equal to glass ionomer sealants and toothbrushing after 30 months.16 With such limited studies, no solid recommendations can be reached for the use of SDF for caries arrest in permanent teeth in children.
Caries prevention in primary teeth
Two studies have reported new lesion formation as a measure of caries prevention on primary teeth. One of them15 studied cuspids and molars comparing 38% SDF treatment to water placebo on first grade school children where both groups were participating in a bi-weekly fluoride rinse programme; children were followed for 36 months. The other study14 included maxillary anterior teeth only and compared SDF to FV; posterior teeth with caries present/restored were not included in the study; children were followed for 30 months. Both studies indicate that SDF prevented new lesion formation during the time followed, but it is unclear whether this happened only on teeth where SDF was applied, or if it was also on adjacent teeth included in the study. With such limited data, it is not possible to make strong recommendations for caries prevention with SDF.
Caries prevention in permanent teeth in children
Two studies have reported new lesion formation as a measure of caries prevention on permanent teeth in children. The first study found a significant reduction in new caries when SDF was applied compared to water control15 after 36 months. The second study compared SDF to glass ionomer cement sealants and no treatment in schools with and without toothbrushing programmes.17 After 18 months, there was little difference between the three groups, and the determining factor in caries prevention was the fluoride toothbrushing programme. With such limited evidence, it is too early to make recommendations for the use of SDF to prevent caries in permanent teeth in children.
Caries arrest and prevention of root caries in the elderly
Several systematic reviews have compiled results from the only three clinical trials18–20 conducted to study caries arrest and prevention of root caries in the elderly. They all concluded that SDF is effective in arresting and preventing root caries in the elderly, but its effectiveness improves when combined with structured oral health education. Results from individual trials can be seen in Table 3.
Caries arrest: at 12/24/30 monthsOHI+Placebo 32%/28%/45%OHI+SDF 61%/83%/90% OHI+SDF+KI 76%/85%/93%Colour of arrested lesions: No difference between groups after 30 months
Abbreviations: OHI = Oral hygiene instructions; CHX = Chlorhexidine rinse; NaF = Fluoride varnish; OHE = Oral hygiene education programme; KI = Potassium iodide application to decrease staining.
Toxicity, contra-indications and staining
None of the clinical trials mentioned, encompassing over 4000 children, has reported any major side-effects or signs of toxicity. Minor side-effects include transient gingival irritation, metallic taste and staining of surfaces that come in contact with the product, including skin. Skin staining is temporary.21 Necessary precautions like applying vaseline on lips, cotton roll isolation and avoiding gingival areas during application are important to avoid accidental staining on the patient.
Protecting work areas during use is important to avoid permanent stains.
Pharmacokinetics studies have only been done on adults and conclude that using 1–2 drops, as indicated on an occasional basis, should pose no dangers of toxicity. Because studies have not been carried out on children, it is important to limit its use to the minimum amount necessary when using on young children, and to consider the risks and benefits of this treatment carefully versus other options with the parents.
As already mentioned, this treatment is contra-indicated on patients who report silver or other heavy metal allergies, or those who present with oral ulcerations, stomatitis or ulcerative gingivitis. Its use is also contra-indicated on teeth that are suspected to have pulpal involvement, as they will continue to develop pulpal symptoms, sometimes acute, after the use of SDF. Careful diagnosis, and ideally radiographic evaluation, is recommended before considering its use.
Dark, sometimes black, staining (Figures 1, 2 and 3) on carious enamel and dentine are an indication of arrest. This can be very visible on anterior teeth, depending on the size and the location of the cavities. Studies indicate that, although the staining may be undesirable to some parents, they will accept this therapy to avoid more involved and risky procedures like sedation or general anaesthesia.22 To identify parents who will be dissatisfied with the results, it is important to have a thorough informed consent form, ideally with photographs that show clearly the potential staining.
Figure 1. SDF staining in anterior teeth.Figure 2. SDF staining in anterior and posterior teeth.Figure 3. SDF staining in posterior teeth.
Some studies have suggested the use of potassium iodide (KI) applied after the SDF to minimize the staining. Results with this protocol are inconclusive, as one of the clinical trials studying root caries in elderly populations found that, after 30 months, there was no difference in the colour of arrested lesions in the group that had KI compared to the other groups who didn’t have it.
SDF does not seem to reduce adhesion of resin or glass ionomer restorative material.23 This is important because its use to reduce sensitivity and/or caries control can be eventually followed by more aesthetic restorations.
Important gaps in knowledge and future research
It is important to mention that most of the studies that investigate the antibacterial effects of SDF have been conducted in in vitro biofilm models with single or selected species combinations, whereas the oral microbiota involves at least 500 species with complex interactions between them. Much work is still required in situ and in vivo to determine whether the bacterial suppression is single species specific or specific to a consortium of species; whether this happens only at the tissue level (where SDF is directly applied) or at the tooth level (surfaces adjacent to application area); or whether there is a whole biofilm shift of the oral microbiome (as surface application may spread in saliva). It will also be important to find out if single or repeated applications have any effect on the whole gastrointestinal microbiome. Answers to these questions, supported by clinical studies of new caries development, are required to determine the actual role of SDF in caries prevention.
It is also important to point out that all the studies mentioned here had a maximum follow-up of 30–36 months, and none had either FV or any kind of restorative treatment following the SDF application. We do not have any evidence of whether the caries arrest can be sustained for longer periods, or the effect of combination with other treatments. Future studies should clarify the true potential of SDF and its role for caries management.
Clinical implications
From presented evidence, we can conclude that regarding SDF:
It has shown efficacy to arrest cavitated caries lesions in primary teeth, with rates varying from 40% to 90% depending on tooth location, tooth surface, application frequency and presence of plaque;
38% SDF gives better caries arrest results than lower concentrations, and twice a year applications are more effective to sustain caries arrest than annual applications;
Caries removal is not necessary, but clean, dry, plaque-free dentine surfaces will maximize contact of the solution with the carious tissue. As there is no need to remove carious tissue, there is no need for local anaesthetics;
Because presence of plaque is crucial, and SDF application is not guaranteed to work in all cases, it is best used as part of a comprehensive caries management programme where one can monitor its effectiveness;
Its effectiveness in incipient lesions, especially occlusal lesions, is uncertain; so it is best to combine it with other proven treatments like sealants and fluoride therapy;
It has proven to arrest and prevent root caries in elderly populations when combined with an oral health education programme, ideally as part of a comprehensive caries management programme;
It is contra-indicated in individuals with silver allergies or gingival ulcerations and in teeth that are suspected to have pulpal involvement;
Patient selection should include those who are not good candidates for traditional restorative treatment, but who have an established dental home to follow-up the use of SDF as part of a comprehensive caries management plan that ideally includes components of chronic disease management models to address the behavioural risk factors;
SDF therapy can be followed up with restorative treatment when patient's circumstances or needs change.
Application
Once proper diagnosis has been completed to identify the right patient/teeth/lesions who will benefit from SDF therapy, application is simple and requires minimal armamentarium. Patient's lips should be protected with Vaseline. Tooth/cavity areas are cleaned of visible plaque, isolated with cotton rolls and dried gently to avoid sensitivity. A drop of SDF is placed on a glass dappen-dish or dispenser provided, and immediately applied with a micro-brush onto the cavitated lesions. It should be allowed to air-dry for at least a minute, if possible.
Follow-up
It is evident that as dental caries is a multifactorial disease with strong behavioural risk factors (diet and plaque control), not unlike other chronic diseases like diabetes and heart disease, its treatment can’t be successful with a single agent, whether fluoride, SDF or other antibacterials. A comprehensive plan that includes chronic disease management model strategies and where the behavioural issues are identified and addressed (eg through Motivational Interviewing or other behavioural management techniques) is desirable if one aims to achieve long-term optimal oral health. A caries risk assessment form at baseline and follow-ups will help in identifying the individual's specific risk factors to address them appropriately.24
Lesions treated should be followed-up 2–4 weeks after application to check for signs of caries arrest (dark and hard surface). Large cavities may require re-application at this time. SDF should be re-applied every 6 months to sustain the arrest when teeth are not restored after SDF therapy. Treated lesions should be closely monitored for continued arrest.25 Plaque removal should be stressed to optimize the chances of sustained caries arrest and, as all candidates of this therapy would fall within the ‘high risk for caries' category, they should be re-evaluated at 3-monthly intervals. As the SDF therapy is intended only to arrest the selected cavitated lesions, preventive FV applications would still be indicated to prevent new lesions and arrest incipient ones in the rest of the dentition. This could be done at the alternating 3 month visits.
Silver diamine fluoride is an additional form of non-surgical management for dental caries that achieves fast caries arrest with a minimally invasive technique. It is invaluable when traditional treatment has to be delayed for medical, behavioural or other reasons, and it may help delay or defer the need for more complicated and invasive procedures. As with all other treatments, it has risks and benefits that should be carefully considered and discussed with parents when choosing the right therapy for individual cases.
