Corrosion Of Amalgam Research Articles

Corrosion current and pH rise around titanium coupled to dental alloys.

Corrosion reactions around titanium, usually considered biologically inert, might be provoked by coupling it galvanically with more corrodible dental alloys. Experiments in vitro simulating the conditions of a titanium dental implant or root canal post coupled to an amalgam filling, demonstrated corrosion current densities up to 31 microA/cm2, anodic pH values around the amalgam down to 2, and cathodic pH values around the titanium up to 10. The amounts of tin released by the enhanced corrosion of amalgam might contribute measurably to the daily intake of this element; the corrosion current generated reached values known to cause taste sensations. If the buffer systems of adjacent tissues in vivo are not able to cope with the high pH generated around the titanium, local tissue damage may ensue; this relationship is liable to be overlooked, as it leaves no evidence in the form of corrosion products.

Effect of oxygen on the corrosion of dental amalgam.

The anodic and cathodic polarization of five dental amalgams were determined as a function of oxygen concentration in Ringer's solution and artificial saliva. The results indicate an anodic polarization behaviour dependent on Cl ion concentration and a corrosion potential determined primarily by oxygen concentration. At high oxygen concentrations the corrosion rates of traditional and copper enriched amalgams were equivalent.

The effect of tensile strain on corrosion of dental amalgam.

In vitro corrosion of two low-copper and three high-copper dental amalgams was examined using stressed and unstressed specimens. Stress was applied in tension; anodic polarization curves and polarization resistance were determined. In stressed condition, the passive current density was higher, and polarization resistance was lower. The changes are attributed mainly to the fracture of passive films by creep strain.

Creep and corrosion of amalgam.

Creep and corrosion were determined for an amalgam that demonstrates both the absence or presence of γ2 depending on final Hg content. The results showed that corrosion was directly related to the amount of γ2 present, while creep was either low or high depending on the absence or presence of γ2.

Electrochemical behavior of Sn 8Hg (gamma-2) and dental amalgam in a phosphate buffer solution

The gamma-2 phase (Sn 8Hg) and a dental amalgam in phosphate buffer have been studied by means of potentiostatic and galvanostatic techniques, along with a rotating ring-disc electrode (RRDE). The analysis of results has shown that phosphate ions play an important role in the corrosion of amalgam. The anodic reaction leads to the formation of soluble species and a passivating film, which is probably composed of tin hydroxide and tin phosphate.

A study on galvanic degradation of dental amalgam using activation analysis assessments

The method of neutron activation and gamma-ray spectrometry was used for studying galvanic corrosion of dental amalgam. The behaviour of galvanic couples of zinc containing and zinc free amalgam with dissimilar electrodes from other restorative material was investigated in various electrolytic media, in absence and presence of oxygen. Severe corrosion of amalgam takes place when coupled with gold electrodes.

Mechanism of chloride corrosion of dental amalgam.

Polarization of conventional dental amalgam in Ringer's solution produces a dissolution of the gamma 2 phase at--250 mV (SCE) and formation of Sn-Cl and Sn-O-Cl. This study was undertaken to determine the electrochemical nature of these reactions. Potentiostatic polarization scans were run at 4, 37 and 50 degrees C in several dilutions of aerated Ringer's solution. Manipulation of reactant concentrations and electrolyte temperature produced shifts in the potentiostatic profiles. At 50 degrees C, a gamma 2 dissolution peak shift to -300 mV was observed, and at 4 degrees C the peak shifted to -200 mV. Dilution of Ringer's solution with respect to [Cl-] over three orders of magnitude produced a linear shift in the noble direction of 500 mV. Cathodic polarization appears to be limited by the oxygen half cell reaction. Changes of [Cl] affect the shape of the peak, round out its approach to the current maximum. Shifts in peak potential due to temperature and concentration changes agreed with calculations based on critical pitting potential for gamma2 dissolution due to a chloride reaction. Polarization profiles in pooled saliva agreed with calculated potentials based on known saliva [Cl-].

The development of an artificial saliva for in vitro amalgam corrosion studies

Published data, consideration of chemical and physical properties and the requirements of amalgam corrosion testing were used to formulate an artificial saliva. A previously described method was used to determine the relevance of a number of human saliva constituents. Some results of those tests are described. Practical problems are discussed, and necessary further developments outlined. A number of other applications are suggested.

A study of the corrosion of dental amalgam using the ring-disk electrode.

The rotating ring-disk electrode technique has been applied to the study of anodic dissolution of dental amalgam in a simulated saline solution. The electroactive domains of the silver, tin, and mercury couples (the main constituents of the amalgam) were determined from current-potential curves obtained at a rotating gold-disk electrode in solutions containing salts of the respective metals. Subsequently, anodic currents were applied to a rotating amalgam-disk electrode and the soluble products produced were identified using a concentric gold ring electrode, i.e., using the rotating gold-ring, amalgam-disk electrode. Species generated at the amalgam disk are transferred to the gold ring by convective diffusion. Tin ions were found to be the only soluble species generated at the amalgam disk. No evidence for dissolution of other components was found. The selective dissolution of tin from the amalgam is also consistant with potential shifts observed in reptititve current-potential curves of an amalgam disk. This study provides a direct proof for the selective dissolution of tin during corrosion of dental amalgam in an in vitro environment.

The in vitro measurement of amalgam corrosion rates by the polarization resistance technique

Measurement of the corrosion rates of three distinctive amalgam alloys (lathe-cut, spherical and dispersed-phase) when immersed in three different electrolytes, including saliva, is reported. The results indicate that the dispersed phase alloy amalgam exhibits a lower corrosion rate than a conventional lathe-cut alloy amalgam but is somewhat inferior to a spherical alloy amalgam.

An application of potentiostatic current ‐time transients to study the corrosion of dental amalgams*

Potentiostatic current-time transients obtained during anodic polarization of a conventional dental amalgam and its component phases have been analysed to characterize the possible electrochemical reactions involved in amalgam corrosion. These reactions involve such surface phenomena as adsorption, anodic film formation, film dissolution, etc. which are well reflected in current-time transients. The analysis of these transients from the standpoint of thermodynamics, suggests that the saline corrosion of dental amalgam may occur through the dissolution of the passive anodic films on Sn7Hg(gamma2) and Cu6Sn5 (eta') and the dissolution reaction appears to be related to the formation of tin-oxychloride.

Effects of amalgam corrosion products on human cells.

Using three independent criteria, we have found that 10−4‐10−6M concentrations of ions presumably liberated from the corrosion of dental amalgam produce injurious effects on either human gingival fibroblasts or HeLa cells when the cells are grown in culture. Release of 51Cr and uptake of trypan blue dye were seen with 10−5M Hg++ and Ag+. Inhibition of amino acid incorporation into protein‐like material was seen with eluates of amalgam and with ionic solutions of most metals comprising dental amalgam. Stannous ion showed little if any cytotoxic potential. These results suggest that corrosion products of amalgam are capable of causing cellular injury or destruction.

In vivo and in vitro corrosion products of dental amalgam.

Corrosion products of amalgam produced in Ringer's solution were compared with products formed in vivo using scanning electron microscopy, X-ray microanalysis, and potentiostatic anodic polarization. The corrosion products in an old amalgam were probably a mixture of tin-oxide and tin oxychloride. In vitro corrosion of fresh amalgam resulted in the buildup of similar products.

Effect of dissolved halogens on corrosion of zinc amalgam

Effect of dissolved halogens on corrosion of zinc amalgam

Effect of dissolved halogens on corrosion of zinc amalgam

Effect of dissolved halogens on corrosion of zinc amalgam

The corrosion of silver amalgam-- a photometric method.

A photometric method for following the corrosion of plane polished samples of silver amalgam has been evaluated in a pilot study. The rate, type, and extent of the corrosion process were examined for a wide range of reagents of varying pH values. Several previously undocumented effects were observed which have considerable importance in the context of the discoloration and etching of amalgam in the oral cavity.

Corrosion of amalgam in contact with gold

In order to investigate the effect of the gold/amalgam contact, a spherical alloy amalgam was brought into contact with a Type III gold alloy, pure gold, or acrylic resin in the artificial saliva 8 minutes after the start of mixing, and the change was examined by the use of an optical microscope and an electron probe microanalyser periodically for a year. Findings were as follows: (1) The pure gold/amalgam contact produced an irregular silver-gray prominence containing gold, tin, mercury, and silver at the contact area of the gold and a slightly prominent silver-gray circle containing mercury and gold at the margins of the area after one hour. Outside the margin, a slight, diffuse, circular stain appeared by tin deposition after one week. (2) The type III gold alloy/amalgam contact produced a group of silver-colored prominences of a new gold amalgam phase that were a few microns in height and depth in the contact area. After one hour, there was no further change. Outside the contact area, no prominent circle caused by mercury diffusion appeared. There was only slight silver-colored stain by tin deposition. (3) The amalgam surfaces in the artificial saliva were covered with debris which increased with time. The change was less in the gold/amalgam contact than in the resin/amalgam contact and less on the unpolished amalgam surfaces than on the polished amalgam surfaces when in contact with gold. (4) The resin/amalgam contact produced no particular change on the amalgam surface, but the gold/amalgam contact produced a glossy spot of metallic luster in the contact area which did not change after one week. (5) The contacts produced no appreciable changes in roughness and metallurgical structure of the rest of the surface of amalgam.

Corrosion under stress of materials composing dental amalgam.

AbstractCorrosion potentials of materials composing dental amalgam have been measured in artificial saliva as the specimens were subjected to an increasing tensile load. Further, tensile tests have been carried out on specimens which had been previously subjected to controlled corrosion.The corrosion potentials of Cu, Ag, Zn, Ag2Hg3, Ag3Sn and finished dental amalgam showed only a slight increase in the anodic direction as the load increased. The potentials of Sn and Sn amalgams, on the other hand, showed a considerable increase.Most of the above results were explained as being a consequence of the rupture and repair of protective films as stress was applied or released. For Sn, however, it was necessary to postulate a complex attack by the corrodant to explain the large potential change.Of the phases of dental amalgam whose tensile strengths were measured after subjection to controlled corrosion, only the γ2 or Sn‐Hg phase was affected. Its strength was lowered by corrosion, whether or not stress was applied.It was concluded that stress, as such, probably is not a direct factor in the corrosion of dental amalgam under oral conditions.

Corrosion of dental amalgam and its component phases.

Corrosion of dental amalgam and its component phases.

CORROSION OF GOLD AND AMALGAM PLACED IN CONTACT WITH EACH OTHER.

CORROSION OF GOLD AND AMALGAM PLACED IN CONTACT WITH EACH OTHER.