Interactions Between Dental Amalgams and the Oral Environment

Abstract

Dental amalgam fillings interact in a complex way with the environment in the oral cavity as they are subjected to chemical, biological, mechanical, and thermal forces. These forces change the restoration's appearance and properties, while metal ions, amalgam debris, non-metallic corrosion products, and mercury vapor are released into the oral cavity. The phenomena and conditions that affect the amalgam/environment interaction include the chemistry and biochemistry of the environment, formation of biofilms on the amalgam surfaces, existence of localized corrosion cells, galvanic contacts with other metallic restorations, abrasion during mastication, and synergistic effects of the different forces. Corrosion processes result in a degradation of the functional amalgam properties, while tarnishing reactions cause discoloration. Corrosion degradation of amalgam fillings is due mainly to localized corrosion cells in pores and crevices. Corrosion on occlusal surfaces is accelerated by abrasion during mastication, which removes the protective surface films. The average total amounts of metal species, including mercury, released per day in vivo from a restoration have not been determined. Much of the reported indirect evidence for high mercury release rates is either unreliable or controversial. A more detailed investigation is needed and will require the development of more sophisticated techniques of sampling in vivo, as well as both experimental and theoretical modeling in vitro.

Penetration of amalgam constituents into dentine

“…All these factors act continuously or intermittingly and their effect can be complex. 14 One of the major outcomes of these interactions is release of corrosion products from the amalgam restorations. On one hand, corrosion is regarded as an adverse phenomenon.…”

Blood mercury levels of dental students and dentists at a dental school

“…7,8,9,10,11 Corbin and Kohn 12 state that many researchers have found that mercury vapour released from amalgam restorations varies from 1.24 -27 µg/day. While most of the researchers agree that current evidence does not demonstrate that amalgam restorations are hazardous to the health of the general population, some report that mercury release from amalgam is one of the important sources of inorganic mercury.…”

Galvanic Corrosion of Dental Amalgams in Contact with Titanium in Terms of Released Ions

“…Ogawa et al 15) examined the charging and discharging curves of conventional and highcopper amalgams in 0.9 mass% sodium chloride solution and reported that most of the released tin ions existed as tin oxides on the surface of the amalgams. Marek 1) also revealed that the γ 1 phases on an amalgam surface were covered with tin oxide films in the oral cavity. Generally, the γ 2 phase dissolves following eq.…”

“…1,10,11,13) Marek 1) revealed that the γ and the ε phases are thermodynamically more stable than either the γ 2 or η phase. Onagawa and Abe 13) examined the electrochemical stability of each phase existing in conventional and high-copper amalgams using their anodic polarization curves in 0.9 mass% sodium chloride solution.…”

“…Galvanic corrosion of dental amalgams has been noticed mainly in contact with gold alloys 1) since the coexistence of dissimilar metals with largely different potentials creates the risk of a greatly increased amount of ions released from the metals through galvanic corrosion. Another reason for the increased risk is that galvanic pain derived from a galvanic current sometimes occurs in patients treated with a coexisting amalgam and gold alloy.…”