Silver Diamine Fluoride – A “Silver-fluoride Bullet” for Dental Caries

Introduction

Dental caries is the most prevalent diseases among the paediatric, adult and geriatric population affecting nearly 3.5 billion people worldwide.¹ Despite being a multifactorial, biofilm mediated disease, dental caries is highly influenced by the age, environment, socioeconomic status, education, lifestyle, occupation and ethnicity of an individual. Thus, the Global Burden of Oral Diseases is continuously increasing and the negative social and economic effects associated with it, is a growing worldwide problem.²

Various programs and preventive measures like water fluoridation and wide-spread use of fluoridated products are common measures to decrease the caries burden. But in some parts of the world, lack of these intervention methods continue to pose a risk of oral diseases.²

Hence, newer non-invasive strategies are being developed in order to reduce cavitation in both primary and permanent dentitions, focusing mainly on people with lower income, those having limited treatment facilities, for children with special care needs and requiring behaviour management techniques and/or older population with limited manual dexterity and elderly from the institutional old age homes.² Thus, the need of the hour, is an effective public health tool, which lead to the development of a product called “Silver Diamine Fluoride” which was patented in 1970 and is becoming increasingly popular now.

Silver Diamine Fluoride (SDF)

General characteristics

Silver diamine fluoride (AgF (NH)), is an antibacterial, colourless alkaline liquid (pH – 10). Different concentrations of SDF like 12%, 30% and 38% are available as 8 mL dropper vial or bottle.³ Each bottle contains approximately 160 drops and each drop contains around 25 microliter SDF which accounts for 9.5 mg SDF. One vial can be used to treat around 125 lesions and each drop can be used for 4-6 lesions.⁴ Each vial costs approximately 3000 – 3500 rupees. Hence, it is a proven cost-effective treatment modality.

SDF possesses minimal adverse effects on pulpal tissue. It is safe, effective and biocompatible material. A review concluded that SDF is an effective, efficient, equitable and safe caries-preventive agent.² It was approved by the Food and Drug Administration (FDA) in August 2014 and since then has been widely used in the US and other countries like Argentina, Australia, Brazil and China. Some commercially available products are “Advantage Arrest”, “Dengen Caries Arrest”, “FAgamin”, “Advantaclear”, “Cariestop”, etc.

Evolution of SDF

Silver nitrate was widely used in medicine for its antiseptic properties during the late 20th century and introduced to dentistry for various purposes: as a sterilising agent, carious inhibitor, treatment of pyorrhoea, dentinal hypersensitivity and erosion lesion. Later in 1917, Howe’s solution which was ammoniacal silver nitrate was proposed for similar uses. Then with this background, in the year 1970, Dr. Nishino and Dr. Yamaga from Japan formulated ammoniacal silver fluoride. The first product was named SAFORIDE (Bee Brand Medico Dental Co, Ltd, Osaka, Japan) and has been widely used in dentistry since then. This product has been a useful non-invasive tool for arresting dental caries lesions.²

Composition

SDF is not merely a salt of silver, fluoride, ammonia but a mixed heavy-metal halide coordination complex where silver provides antibacterial property, fluoride helps in remineralization and ammonia keeps the solution at a constant concentration for a certain period of time.⁵

Mechanism of Action

1. Modifies the bacterial actions on the tissue –

• It interferes with the biofilm by destroying the bacteria, which is responsible for an imbalance in the local environment and demineralization of the tooth tissues.

2. Enhancing remineralization –

• Fluoride strengthens the demineralized tooth structure caused by acid by-products of the bacterial metabolism.

3. Effect on dentin collagen –

• Inhibits collagen degradation by inhibiting Matrix Metalloproteinases (MMPs) and Cysteine Cathepsins. Fluoride also has potent inhibitory effect on the proteolytic enzymes like MMP-2, MMP-8, and MMP-9.5

Applications of SDF in Dentistry

1] To arrest carious lesions in deciduous teeth and young permanent teeth.²

2] To arrest root caries and prevent the formation of new lesions in elderly patients.²

3] To prevent pit and fissure caries in young permanent teeth.²

4] To treat dentinal hypersensitivity.²

5] To prevent secondary caries.²

6] To enhance the retention of Glass ionomer restorations by improving the adhesion to the tooth^.4

7] Used as a liner beneath Glass ionomer restorations as it prevents secondary caries.⁴

8] Used as an agent for Atraumatic restorative technique.⁴

9] Used as an intracanal irrigant.⁵

Clinical Application Protocol

1] An informed consent is mandatory from the patient or parents or caregiver explaining the clinical procedure and drawbacks like staining of carious lesion.

2] The armamentarium required is simple and easily available.

It is as follows – SDF vial, cottons roll for isolation, cotton pellets or micro brush for application of SDF, petroleum jelly (vaseline) for protection of soft tissues, tooth brush to apply fluoride varnish and dappen dish to contain SDF.

3] Steps are –

• Protective eyewear is provided for patient safety and a plastic-lined bib is placed on the patient in order to prevent staining of clothes by accidental spillage.

• After isolation with cotton rolls, the soft tissues like lips and gingiva are coated with petroleum jelly such as vaseline or lip balm to protect from discolouration by SDF.

• The carious lesion is cleaned to remove any food debris and dried before SDF application.

• Then using a microbrush or a cotton pellet, SDF is applied on the lesions for a minimum of 1 minute and allowed to air dry.

• Patient is asked to avoid rinsing with water after SDF application.

• The surface of the tooth is protected by applying fluoride varnish or vaseline on SDF coated areas.

• Biannual application is more effective than yearly application.

• The caries management plan encompasses the plaque control regimen, diet counselling of the patient, combination of various fluoride programs for the prevention of caries progression like fluoride varnish, fluoride gel, fluoride mouth rinses or use of fluoridated toothpastes and also use of sealants based on patient’s age.⁶

Case Management and Follow-up Protocol

1] After SDF application, patient is recalled for periodic follow-ups in order to closely monitor the arrest of the carious lesions based on the risk factors. The follow-up is especially important in permanent teeth.

2] The follow-up protocol includes both caries and radiographic examination for any arrest or progression of the carious lesion.

3] For large lesions and lesions in areas difficult to clean, follow-up is combined with restorative treatments, based on the radiographic findings like placement of Glass ionomer restorations or a conventional restorative treatment, depending on the patient’s caries condition. ²

Indications

It is indicated for cavitated lesions on both coronal and root surfaces of the tooth, not showing any suspected pulpal involvement.

Teeth that are asymptomatic and are present in selfcleansable areas.²

Contraindications

It is contraindicated in patients with silver allergy, although no case study has been reported till date on silver allergy incident.

It should also be avoided in patients with open lesions, stomatitis or ulcerative gingivitis.²

Side effects

Minor side effects like acute transient gingival irritation and metallic taste have been reported in some individuals. The gingival tissue affected becomes white, but heals within 1–2 days.²

No acute side effects of SDF are noted in reviews or study reports when used following the application protocol on individual trials for children and adults.²

Drawbacks

It is important to handle SDF vials carefully as it causes staining of skin and gingiva. It causes dark staining of the carious tooth tissues, as a result of precipitation of silver phosphate.

Thus, Knight et al., proposed the application of potassium iodide after the application of SDF to reverse or control the stains, such that remaining free silver ions in the solution will react with potassium iodide to precipitate creamy white silver iodide crystals. And thus, free silver ions are no longer available to react with sulphur and other reagents in the mouth to form black precipitates onto the teeth. Riva Star (SDI, Baywater, Victoria, Australia) one of the commercial products with both SDF and potassium iodide combination is available in the market. However, one of the clinical trials for adults showed that potassium iodide application did not have any effect on reducing the black stains on the root carious lesions.⁷

Recent Advances

Many clinical trials are being carried out to assess the effectiveness of SDF in restorative treatment as an indirect pulp capping (IPC) material apart from the above-mentioned uses. It shows the ability to induce tertiary dentin formation.

Hence is proven to enhance the remineralizing, re-hardening and antimicrobial efficacy and can act as an effective IPC material.⁸

Conclusion

Removal of carious tooth structure is not required to provide caries arrest by SDF.² SDF solution in 38% concentration is effective than lower concentrations of 12% due to the increased fluoride content and higher effectiveness of caries arrest.⁹ Application time is variable for each patient, as caries arrest is not time dependent.² Hence, SDF is an effective caries control tool that can be used by clinicians and public health dentists as a part of caries treatment on individual and community level.

Conflict of Interest

None.