Silver Diamine Fluoride for Caries preventive dentistry in primary teeth

Early childhood caries (ECC) affects one in two children below the age of 6 years in India.1 This is an alarming ratio and should call for immediate concern.

Preventive dentistry - the need of the hour

A disease with a 40% prevalence in children, who have a long life ahead of them, is considered a serious public health problem and requires focused attention. Caries management strategies primarily consist of:

• preventive treatment methods and
• non preventive treatment methods.

Preventive strategies aim to prevent the onset of caries and protect teeth from undesirable effects of caries. These include diet counseling, good oral hygiene, use of fluoridated tooth paste, application of pit and fissure sealants and sodium fluoride varnish. Non preventive treatment methods involve arresting or slowing caries progression by mechanical caries removal and restoration of lost tooth structure.2 In 2014, 38% silver diamine fluoride (SDF) was approved by the FDA for use in children with ECC.3 SDF combines the antibacterial effects of silver and the remineralizing effects of fluoride and, is therefore a promising agent in both caries prevention as well as treatment.

What is Silver Diamine Fluoride (SDF)?

SDF (38% Ag (NH3)2F) is a clear liquid composed of 24-29% silver and 5-6% fluoride. It is alkaline at a pH of 10. Silver contributes to the antimicrobial effect and fluoride is responsible for the observed remineralization effect.2 First introduced in Japan in the 1960’s, it has been in use for more than 50 years to arrest dental caries in children.

An undesirable effect is its distinctive permanent black staining of teeth. Despite this drawback, American Academy of Pediatric Dentistry (AAPD) has concluded that 38% SDF is currently the best evidence-based material to arrest caries for children, adults, and patients with special needs.

Mechanism of action

SDF derives its effectiveness from silver nitrate and fluoride. The three significant mechanisms in arresting or preventing caries are 4-

1. Antibacterial action on cariogenic bacteria (by silver)
2. Remineralization and inhibition of demineralization of enamel and dentin (by fluoride) and
3. Inhibition of dentin collagen type I degradation (by fluoride)

1. Antibacterial action on cariogenic bacteria- Silver ions penetrate the lesion and exert their influence to about 25–30 microns into enamel, 200–300 microns into the dentin, and up to 2 mm into a deep carious lesion. Silver, due to its positively charged ions, adheres to the negatively charged bacterial cell wall and prevents bacterial aggregation. It has been hypothesized that silver interacts with bacterial enzymes, blocking the electron transport system, causing enzyme deactivation, membrane rupture and subsequently, cell death.
2. Remineralization and inhibition of demineralization- SDF reacts with tooth hydroxyapatite and forms silver phosphate and calcium fluoride which promotes remineralization. Additionally, silver ions obturate dentinal tubules contributing to an increase in dentin hardness, which in turn makes the lesion cariostatic.
3. Inhibition of dentin collagen type I degradation- The fluoride in SDF is proposed to have a potent inhibitory effect on the proteolytic enzymes, MMP-2, MMP-8, and MMP-9, reducing dentin collagen degradation in carious lesions.

Mechanism of discoloration

Silver compounds such as silver oxide and silver phosphate are responsible for the permanent black staining of the carious lesions.4 (Figure 1) If soft tissues come into contact during application, the oral mucosa may be stained temporarily with henna-like discoloration. Since the dermis cannot absorb silver, the stains will disappear over about 14 days as the keratocytes are shed.3

Indications

• SDF is indicated in active carious lesions within dentin, without any clinical signs of pulp involvement.5 When possible, radiographs must be taken to assess depth of lesions.
• SDF can also be used prior to placement of restoration, as a part of caries control therapy.

Patients who benefit with application of SDF are those with

1. High caries risk with active, cavitated carious lesions in anterior or posterior teeth
2. Behavioral challenges and/or children with special healthcare needs when local or general anaesthesia is not possible
3. Multiple cavitated caries lesions which would otherwise require multiple visits
4. Cavitated dental caries lesions that are difficult to treat
5. Difficult access to dental care

Contraindications

• Patients who are allergic to silver and
• those with spontaneous or nocturnal pain

are contraindicated from receiving SDF.

Clinical steps in the application of SDF

Obtain an informed consent from parents regarding permanent staining of teeth. Use of pictures, before and after SDF applications are recommended for better understanding.

Complete caries excavation is not necessary prior to application of SDF. It may be applied without or with minimal excavation, especially in children with limited co-operation. However, there are factors to consider- Dentinal staining will be more without excavation and with the presence of greater residual bacterial load and, caries arrest may take longer and more frequent applications may be required. 2 (Figure 2)

Follow up

Recall the patient after two to four weeks of initial treatment to check the arrest of the lesions treated. Additional SDF can be applied at recall appointments as needed, based on the color and hardness of the lesion or evidence of lesion progression. Post SDF, tooth can be restored with adhesive materials. When lesions are not restored after SDF therapy, bi- annual reapplication shows increased caries arrest rate versus a single application.

Safety and Adverse effects

Safety trials that have used it in more than 3800 individuals reported no serious adverse effects.6 Minor effects like:

• permanent black staining of teeth,
• metallic taste,
• pulpal and soft tissue irritation and
• development of small white reversible lesions in the oral mucosa