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Silver is a broad-spectrum antimicrobial agent that can be used for caries management. Dentists used silver-containing solutions for deep cavity disinfection before restoration. Silver fluoride, silver nitrate, silver diamine nitrate, silver diamine fluoride, and nano-silver fluoride were used in deep cavities for antimicrobial purposes. Indirect silver fluoride application induced pulp inflammation and reparative dentine in most cases, and pulp necrosis in some cases. Direct silver nitrate application caused blood clots and a wide inflammatory band in the pulp, whilst indirect silver nitrate application caused hypoplasia in shallow cavities and partial pulp necrosis in deep cavities. Direct silver diamine fluoride application induced pulp necrosis, while indirect silver diamine fluoride application induced a mild inflammatory response and reparative dentine formation.
The main properties of various silver-containing solutions are summarized in Table 1.
Solution [Ref.] | Wt.% (Concentration According to Manufacturer(s)) | Anticaries Properties |
---|---|---|
Silver fluoride [1][2] | 40% (Ag: 340,000 ppm; F: 60,000 ppm) |
|
Silver nitrate [3] | 25% (Ag: 151,130 ppm) |
|
Silver diamine nitrate [4] | 48% (Ag: 319,914 ppm *) |
|
Silver diamine fluoride [5] | 12% (Ag: 80,170 ppm; F: 14,150 ppm) |
|
30% (Ag: 200,400 ppm; F: 35,400 ppm) | ||
38% (Ag: 253,900 ppm; F: 44,800 ppm) | ||
Nano-silver fluoride [6] | 1.05% * (Ag: 399.33 ppm; F: 10,147 ppm) |
|
The 40% silver fluoride solution was used for deep caries management. The 40% silver fluoride solution contained 34% silver and 6% fluoride. According to this percentage, the fluoride content was supposed to be 59,900 ppm [1]. The chemical analysis of the components of two silver fluoride products found that the fluoride content was higher than expected, ranging from 78,000 to 120,000 ppm [1][7]. As a result of these findings, Gotjamanos & Afonso [7] recommended that the use of silver fluoride in paediatric dentistry be discontinued because these unacceptably high fluoride levels pose a potential risk of toxicity to children and, if it enters the bloodstream, it might result in fluorosis, especially in the case of an undetected pulp exposure [2]. Silver fluoride has antibacterial and remineralising properties. The silver ions present in the silver fluoride act in two different ways: (1) their bactericidal/bacteriostatic effect on the microorganisms present in the carious lesion; (2) mechanical sealing of the carious and sound dentinal tubules [8]. Silver fluoride is used as a cavity conditioner in conjunction with glass ionomer cement as an atraumatic restorative method. After partial caries excavation, silver fluoride is applied, and then the cavity is sealed with a glass ionomer cement restoration. Silver fluoride showed a 100% success rate in 400,000 cases treated at the Dentistry School of Western Australia University [8]. The treatment success was based solely on the absence of symptoms.
Introduced by Dr Nishino and Dr Yamaga in the 1950s, silver diamine fluoride (SDF) has been used for arresting caries, preventing secondary caries, and decreasing hypersensitivity [21]. Commercial SDF products are available in various concentrations (3.8%, 10%, 12%, 30%, and 38%). Solutions in all of these concentrations are suitable for use as anticaries solutions, with the exception of the 3.8% solution, which is intended for root canal therapy. Silver diamine fluoride is an alkaline solution with a high concentration of fluoride and silver ions [22]. Fluoride changes the hydroxyapatite into fluorapatite, which is more resistant to acid dissolution, so it can remineralise the caries-affected dental hard tissues [23]. In addition, it has an antimicrobial effect on the plaque biofilm [24]. Silver, the other main component of silver diamine fluoride, is well known for its strong antimicrobial effect which helps in sterilizing the infected tissues, and it blocks the dentinal tubules to seal them from microorganisms and their by-products [25]. Combing both silver and fluoride in one solution so they can perform their actions synergistically resulted in the superior results achieved by the silver diamine fluoride. Despite its effectiveness, silver diamine fluoride usage for arresting caries is still an off-label usage in many countries, where it is used only as a desensitizing agent. Silver diamine fluoride requires only topical application to achieve its effect. This ease of use has led to its widespread use among practitioners recently, especially during the COVID-19 pandemic [26]. The World Health Organization’s Center for Quality Improvement and Evidence-Based Dentistry introduced safer aerosol-free emergent dentistry as a protocol for caries management [27]. Silver diamine fluoride was the first choice in this protocol for the treatment of caries and toothache related to caries, as its use can prevent cross-infection. The effectiveness of silver diamine fluoride in caries control has been proved in many previous studies [28][29][30].