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1. Introduction
The use of silver in dentistry dates back to China in 659 A.D. It was used not only for its material properties, but also for the long-known antimicrobial effects. Silver has been adopted as an antimicrobial material for thousands of years. People in ancient Mexico used silver to make containers for storing water and food. A Roman pharmacopoeia written in 69 B.C. mentioned the use of silver as a disinfectant [1]. Silver nitrate is one of the most common silver salts and has antibacterial properties which have been widely used in medicine. Silver nitrate solution is a colourless and odourless solution. It has been used as a cauterizing agent in medicine for treating wounds, especially burned wounds [2]. Physicians used silver nitrate to chemically cauterize umbilical granulomas and warts. In the late 19th century, silver nitrate was used to treat venereal disease. A solution of 1% silver nitrate was used as eye drops for newborn babies to protect their eyes from the transmission of gonorrhoea from mothers during birth [3]. It has long been a common antimicrobial agent for medical use because of its broad spectrum of antibacterial activity, lack of bacterial resistance, and low toxicity [4]. However, the use of silver nitrate became subsidiary when penicillin and other antibiotics were introduced in the 1950s.
2. Antimicrobial Action of Silver Nitrate in Dentistry
Dentists often used silver nitrate as a disinfectant agent because of its escharotic, dehydrating, and sclerosing properties. Silver nitrate sticks were used to manage oral ulcers [5] and to reduce pain due to aphthous stomatitis [6]. Ammoniacal silver nitrate, or Howe’s solution, has been used as a sterilisation agent for disinfecting root canals [7]. Silver nitrate was used to sterilise disintegrated and infected dentine during restorative treatment [8]. It was also used for treating deep caries lesions and indirect pulp capping because the solution could permeate the affected dentine and fill the demineralised dentine with silver particles [9].
Silver nitrate’s antibacterial action could be related to silver’s extracellular and intracellular binding properties. Positive silver ions can electrostatically bind to the bacterial membrane and cell wall, which contain negative-charged peptidoglycans [10]. Additionally, a bacterial cell’s transport system may actively uptake silver ions. After silver ions are taken up, they can bind...