A Review on Dental Materials by Hamid Reza Rezaie & Hassan Beigi Rizi & Mojdeh Mahdi Rezaei Khamseh & Andreas Öchsner

Author:Hamid Reza Rezaie & Hassan Beigi Rizi & Mojdeh Mahdi Rezaei Khamseh & Andreas Öchsner
Language: eng
Format: epub
ISBN: 9783030489311
Publisher: Springer International Publishing

3.3.4 Amalgam

Generally, dental amalgams are formed by mixing 45–55% Hg and a powder mixture of Ag, Sn, and Cu (in some cases, smaller amounts of Zn, Pd, In, or Se are added) by applying a mechanical vibration process, which results in a putty-like material that is account for easily filling and manipulation. Dental amalgam is currently widely used as a dental restorative material and has been used over 150 years after firstly introduced by Chinese and in 1528 it was proposed as a dental filling by a European physician in Germany. The spot parts of the amalgam history date back to a silver–mercury amalgam that was made in France. A Silver paste filling material was fabricated by mixing the silver coins with mercury. Between around 1895–1908 years, the amalgam was globally accepted with the development of state-of-the-art alloy with the composition of 68.5% silver, 25.5% tin, 5% gold, and 1% zinc and the first commercially available amalgam rich in silver and gold as an alternative to the copper has happened. By introducing a new atomization process for dental amalgams manufacturing, extreme improvement in the quality has occurred. By addition of copper elements, with high portion, the durability of amalgam has been increased which causes 12 years serving and consequently, the post-processing of the polishing is not required after placement [60].

There is no doubt to say that the oral environment is potential for corrosion attacks due to the wide pH range during the mastication of different foods. So, any restorative materials would be susceptible to corrosion problems. Amalgam has a high corrosion resistance in most of all oral atmospheres. But in some cases when the level of fluoride content increases, the corrosion resistance is negatively affected. Amalgam often becomes tarnished (i.e. an initial sign of corrosion at which a thin black layer grows across the surface of the alloys containing microorganisms and mucin) and surface discoloration happened due to the oxides and sulfides formations. The corrosion of that could trigger by using galvanic couples and as a result, ion releasing is occurred [61]. The ions releasing especially mercury contents face the body with different toxic problems such as neurotoxicity, kidney dysfunction, etc. The techniques for inspection of initial corrosion are limited because of current clinical diagnostic tools and under surface corrosion of restoration materials. Conventional silver amalgam materials involving phases that harshen corrosion attacks to the γ2 phase (Sn7Hg). As a consequence, the formation of the tin oxychloride is account for toxic mercury release and formation of the γ1 and γ2 from unreacted γ phase. In high copper amalgam alloys, the ή (Cu6Sn5) phase is vulnerable to the corrosion which does not release mercury into the body. However, due to the shifts of Ecorr to more positive values, high Hg injection might still happen. Electrochemical testing on pure phases proved that the Ag2Hg3 phases could dramatically shield against corrosion attacks followed by Ag3Sn, Ag3Cu2, Cu3Sn, Cu6Sn5, and Sn7–8Hg. Moreover, the compounds of SnO, SnO2, Sn4(OH)6Cl2, Cu2O, CuCl2.3Cu(OH)2, CuCl, CuSCN, and AgSCN have been observed in patients [62].

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.