Corrosion Of Amalgam Research Articles

Quantum Chemical and Electrochemical Studies of Water and Ethanol Extracts of Salvadora Persica (Miswak) as a New Green Inhibitor for Dental Amalgam in Artificial Saliva

Abstract The corrosion-inhibitive properties of Salvadora Persica water and ethanol extracts as a novel green inhibitor for dental amalgam in artificial saliva were studied by using potentiodynamic polarization measurements and electrochemical impedance spectroscopy measurements (EIS). The electrochemical results revealed that the Salvadora Persica extracts demonstrated strong inhibitory effects at 0.66 g/L and implied that the water extract was more effective than the ethanol extract. The inhibition efficiency (IE%) increases with increasing concentrations of both Salvadora Persica extracts and decreases with increasing temperature. The results of this work indicated that Salvadora Persica extracts act as mixed-type inhibitors, inhibiting the corrosion of dental amalgam by the adsorption process, which followed the Langmuir adsorption isotherm model. The thermodynamic results revealed that the adsorption process is endothermic with electrostatic interaction (physisorption). Various DFT parameters, like HOMO and LUMO energy, gab energy (∆E), electronegativity (χ), softness (

Experimental Study and Mathematical Modeling for Corrosion of Amalgam at Different Periods

This work involves experimental study for corrosion of amalgam as filling material after different period time (0, 7, 14, 21, 35, 42 days) in artificial sa liva by electrochemical method to estimate corrosion parameters such as corrosion potential Ecorr, corrosion current density icorr, and Tafel slopes bc & ba. The results of polarization resistance which calculated according to Stern- Geary equation indicates that the resistance of amalgam was increased during the experimental period due to stable phases which produced between mercury and other powders in amalgam such as Sn–Hg and Ag–Hg, in addition to Ag–Cu and Ag–Sn phases. Cyclic polarization t est shows that the reverse scan curves meet the forward scan curve along the passive range.Numerical modeling was achieved to estimate the corrosion behavior of amalgam in artificial saliva through longer period time, the results of this modeling shows that values of polarization resistance for amalgam at long time of filling decreases with time, but after 2200 days of filling, i.e. after a t least 6 years.

Negative Effect of Laser Treatment with Nd:YAG on the Corrosion of Amalgam in Artificial Saliva

يتضمن هذا العمل دراسة سلوك تآكل الملغم في اللعاب الاصطناعي عند درجة الحموضة = 6 و 37 درجة مئوية بعد استخدام Nd: YAG ، حيث يستخدم هذا الليزر في شفاء السرطان. تشير هذه الدراسة إلى أن المعالجة السطحية بالليزر تؤثر على مقاومة الملغم للتآكل ، وتشير النتائج إلى أن المعالجة بالليزر لا تعطي الغرض المطلوب لأن طبيعة الملغم ووجود الزئبق في هذه السبيكة قد يتبخر ويعطي سمية يجب أن يكون الإنسان وطاقة العلاج منخفضة لتجنب التبخر. في هذا العمل ، أعطت المعالجة بالليزر بنبضتين تحت ظروف تجريبية تحسنًا طفيفًا في مقاومة الملغم للتآكل مقارنة بنبضات واحدة وثلاث نبضات من خلال معاملات التآكل لسلوك الاستقطاب.

Resolución de irregularidades de color con un sistema restaurador bulk-fill bioactivo: Reporte de caso y seguimiento de 24 meses.

Bulk-fill resin composites represent an excellent alternative to the conventional incremental layering technique for the reduction of polymerization stress on the adhesive interface. Marginal seal can be further improved by the incorporation of bioactive fillers, such as those encountered in Giomers. However, the high translucency required for the adequate polymerization of bulk-fill materials can seriously jeopardize the final aesthetic outcome of the restorations, especially in the presence of inhomogeneous or stained dentin substrates. The aim of this case report was to present the combined use of two bulk-fill Giomer materials (Beautifil Bulk Flowable and Beautifil II LS, Shofu) for the restoration of three posterior maxillary teeth displaying a black stained dentin substrate due to amalgam corrosion products. This technique allowed completion of the restorations with a satisfactory aesthetic and biomimetic outcome. The adequate preservation of the anatomy and function of the three restorations after 24-months follow-up, provides evidence of the enhanced marginal sealing capacity of these bioactive materials and the success of bulk-fill techniques over time.

Study the Effect of Cyperus Rotundus Extracted as Mouthwash on the Corrosion of Dental Amalgam

Many extracted material were used as mouthwash to settle different kinds of oral fungi and bacteria. In this study an extractive of Cyperus rotundus plant E.C.R. which is very active as a mouthwash, was used in concentration range (10-25) ppm in artificial saliva at pH=6.4 and temperature range (288-318) K, to study it’s inhibitory effect on the corrosion of dental amalgam. Potentiostatic and cyclic polarization were used to follow this study. The presence of E.C.R. lead to shift the corrosion potential to the active direction and decreased the corrosion rate to about 98.87%, the inhibition action of E.C.R. resulting from the adsorption of C.R.E. layer between amalgam and saliva as FTIR spectrums shows, where the variety of FTIR adsorption of many group were noticed for the free E.C.R. and adsorbed E.C.R. layer. Thermodynamic of adsorption, corrosion kinetic parameters were also investigated.

Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility.

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu2S).

Is amalgam stained dentin a proper substrate for bonding resin composite?

After the removal of amalgam restorations, black staining of dentin is often observed, which is attributed to the penetration of corrosion products from amalgam. A study was carried out to determine whether this amalgam stained dentin is a proper substrate for bonding resin composites. A literature study and an in vitro study showed that Sn and Zn in particular are found in amalgam stained dentin, and this was the case only in demineralised dentin. In vitro, demineralised dentin acted as porte d'entrÈe for amalgam corrosion products. Bond strength tests with 5 adhesive strategies showed no differences between bond strengths to amalgam stained and to sound dentin, but did show different failure types. A clinical study showed good survival of extensive cusp replacing resin composite restorations. No failures were attributed to inadequate adhesion. It is concluded that staining of dentin by amalgam corrosion products has no negative effect upon bond strength ofresin composite. It is suggested that Sn and Zn may have a beneficial effect upon dentin, thus compensating the effects of previous carious attacks, preparation trauma and physico-chemical challenges during clinical lifetime.

Mercury Removal of Fluctuating Ethane Feedstock in a Large Scale Production by Sulphur Impregnated Activated Carbon

Abstract — The removal of mercury from entering process area is the key to safeguard aluminum brazed heat exchanger and other critical equipment in the ethylene production plant from Liquid Metal Embrittlement (LME) and amalgam corrosion. Sulphur Impregnated Activated Carbon (SIAC) is the proven technology for mercury removal. However, currently there is no specific study conducted at fluctuating ethane feedstock to monitor its functionality and performance. This study is conducted at a large scale of aging ethylene plant without Ethylene Buffer Storage Tank (EBST) which results in fluctuating feedstock upstream of mercury removal vessel. Number of experiments and data gathering were done by observing current mercury level at various process stream to determine its performance before and after installation. Analysis performed at mercury removal vessel's outlet indicates consistent decrease in adsorption capacity with an increase of temperature. The fluctuation of ethane feedstock from 35,000kg/hr to 71,000kg/hr also results in less adsorption efficiency of SIAC.

Effect of amalgam corrosion products in non-discolored dentin on the bond strength of replaced composite resin.

Objectives:To evaluate the effect of amalgam corrosion products in non-discolored dentin on the bond strength of replaced composite resin.Materials and Methods:One hundred and sixty-one Class I cavities were prepared on extracted premolars and divided into seven groups. Group 1: Light-cured composite; Groups 2, 3, and 4: Amalgam stored in 37°C normal saline for respectively 1, 3, and 6 months and then replaced with composite leaving the cavity walls intact. Groups 5, 6, and 7: Identical to Groups 2, 3, and 4, except the cavity walls were extended 0.5 mm after amalgam removal. Eighteen specimens from each group were selected for shear bond strength testing, while on remaining five samples, elemental microanalysis was conducted. Data were analyzed using Mann-Whitney and Freidman (α = 0.05).Results:There was a significant difference between Groups 1 and 4 and also between Group 1 and Groups 5, 6, and 7. However, Groups 1, 2, and 3 showed no significant difference regarding bond strength. Bond strengths of Group 4 was significantly less than Groups 2 and 3. However, Groups 5, 6, and 7 showed similar bond strength. There was no difference among all groups in terms of metal elements at any storage times.

Clinical longevity of extensive direct composite restorations in amalgam replacement: Up to 3.5 years follow-up

ObjectivesThis prospective clinical trial evaluated the longevity of direct resin composite (DRC) restorations made on stained dentin that is exposed upon removal of existing amalgam restorations in extensive cavities with severely reduced macro-mechanical retention for amalgam replacement. MethodsBetween January 2007 and September 2013, a total of 88 patients (57 women, 31 men; mean age: 51.6 years old) received extensive cusp replacing DRCs (n=118) in the posterior teeth. DRCs were indicated for replacement of existing amalgam restorations where dentin substrates were stained by amalgam. After employing a three-step total-etch adhesive technique (Quadrant Unibond Primer, Quadrant Unibond Sealer, Cavex), cavities were restored using a hybrid composite (Clearfil Photo Posterior, Kuraray). At baseline and thereafter every 6 months, restorations were checked upon macroscopically visible loss of anatomical contour, marginal discolouration, secondary caries, fractures, debonding and endodontic problems. Restorations were scored as failed if any operative intervention was indicated for repair, partial or total replacement. ResultsRestorations were observed for a minimum of seven, and maximum 96 months (mean: 40.3 months). In total, four failures were observed due to fracture (n=1), endodontic complications (n=2) and inadequate proximal contact (n=1). Failures were related neither to inadequate adhesion nor to secondary caries. Cumulative survival rate was 96.6% (95% CI: 89–95) up to a mean observation time of 40.3 months (Kaplan–Meier) with an annual failure rate of 0.9%. ConclusionIn case of amalgam replacement, dentin that is exposed upon removal of existing amalgam restorations does not impair clinical longevity of extended cusp replacing direct resin composite restorations. Clinical significanceExtensive amalgam restorations can be replaced with a variety of treatment options. This clinical study indicates that in such cases directly applied resin based composites offer a reliable and low-cost treatment option, even if dentin is stained by amalgam corrosion products.

Evaluation of corrosion products in dentin after removal of old amalgams with and without roughing

Background & Objectives: To evaluate of corrosion products in dentin after removal of old Amalgams with and without roughness Materials and Method: Twenty Class II cavities were prepared on extracted premolars then Randomly were divided into four groups according to how they were restored. Group 1 : Light-cured packable composite to establish a microleakage baseline; Group 2: A high copper Amalgam; then stored in 37 ° C normal saline for 6 months to create amalgam corrosion products. Group 3: Identical to Group 2, but later the amalgam was replaced with composite leaving the cavity walls intact. Group 4: Identical to Group 3 except the cavity walls were extended 0.5 mm after amalgam removal prior to insertion of the composite. There are 5 specimens in each four groups for EDX analysis.Evaluation of EDX analysis was descriptive. Results : Corrosion products were detected in Groups 1,2,3 but were not detected in Group 4 . Conclusions : After amalgam removal, roughing dentinal walls could remove the corrosion products penetrating it. Keywords : Corrosion, High copper Amalgam, Dentin, surface roughing

EDS and μ-XRF mapping of amalgam degradation products in ancient mirrors

An amalgam mirror is a mirror type, used from the fifteenth century until the end of the nineteenth century, where the reflective layer is constituted by a tin amalgam layer adhered to a glass sheet. In this work, two amalgam mirrors samples were studied by scanning electron microscopy with an energy dispersive spectrometer and by micro-X-ray fluorescence elemental mapping to go deeply into the understanding of the degradation mechanism of the amalgam layer of ancient mirrors. The investigation has been focused for the first time on the reflective surface of the amalgam layer adherent to the glass sheet to better understand the processes of amalgam corrosion. The two amalgam degradation compounds, romarchite and cassiterite, has been spatially differentiated by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) maps. SEM images and micro-X-ray fluorescence and EDS maps showed that the amalgam degradation products grow up to form hemispherical stratified calottes. This structure is probably due to a mechanism involves cyclic phases and oxygen radial diffusion from a superficial oxidation nucleus.

Galvanic Corrosion of Dental Alloys and Amalgam in Artificial Saliva Containing Citric Acid

Galvanic Corrosion of Dental Alloys and Amalgam in Artificial Saliva Containing Citric Acid

A multidisciplinary approach for the conservation of a building of the seventeenth century

A long-term multidisciplinary conservation study is actually in progress inside the Villa della Regina, a prestigious Savoy residence built in the seventeenth century and recently restored. The walls of some rooms of the Villa are decorated with precious tin–mercury mirrors, that are baked with a reflective coating constituted of a tin–mercury compound surrounded by liquid mercury. The reflective layer is very soft, thus any restoration is difficult to be performed and can lead to a complete destruction of the artifact. Amalgam corrosion is a very slow process and, although there is no way to prevent the oxidation of the reflective layer, the conservation state of the artifacts may be improved by keeping them in a controlled environment. For this reason, a monitoring system has been designed and installed that is based on a wireless network of extremely compact sensors, for temperature and relative humidity measurements. The sensors have been specifically designed to satisfy the requirements for use in cultural heritage field and the system allows one to automatically collect the data that can be analyzed with the final aim to establish a correlation between the environmental conditions and the conservation state of the artifacts. A restoration has been carried out by producing in situ an amalgam inlay on the corroded area to slow down the release of liquid mercury in order to avoid also possible unsafe conditions for staff and visitors. In addition, a sensor has been developed which is based on a prototypical plastic optical fiber for the detection of low concentration Hg vapors to ensure the safe conditions in the Villa rooms. The sensor is being tested in laboratory.

Risk analysis for operation of aluminum heat exchangers contaminated by mercury

AbstractBrazed aluminum plate‐fin heat exchangers are extensively used in gas separation processes including LNG, LPG, NGL, nitrogen rejection and olefins manufacture. In situations where mercury is a trace component of feed gas or liquid feeds to crackers, condensation of liquid or precipitation of solid mercury can occur in heat exchanger passes, even with functional mercury removal systems in place. Mercury in liquid phase causes, under certain well‐defined conditions, liquid metal embrittlement of susceptible metallurgy or amalgam corrosion of core fins, both of which can lead to sudden loss of pressure containment. Mercury‐contaminated aluminum heat exchangers require close scrutiny and quantitative risk assessment to allow safe operation, remediation or to justify replacement. The risk analysis procedure involves computational prediction of mercury deposition, inspection of critical areas, detailed assessment of metallurgy and fabrication, strain analysis of temperature changes during trips and shutdowns and oxide fatigue analysis. Assigning probability of equipment failure requires a complete understanding of the mechanisms of liquid metal embrittlement and amalgam corrosion that operate on aluminum plate‐fin heat exchangers. Statistical correlations to known failures are essential to assignment of probability‐based risk factors. Probabilities of leak and rupture failure modes can be estimated using amounts and locations of mercury deposits determined from focused inspection or calculated thermodynamically. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009

Penetration of amalgam constituents into dentine

Objectives Amalgam restorations are replaced by adhesively placed composite resin restorations at an increasing rate. After the removal of amalgam dentine often shows marked dark discoloration that is attributed to the penetration of corrosion products from overlying amalgams. It is questioned whether penetration of metals into dentine affects the dentine as a substrate for adhesive procedures. This study has been performed to clarify the origin of dark discoloration of dentine by metals from amalgam with special regards to corrosion products. Methods A review of the literature has been performed using Medline database. As keywords dentine and amalgam, subsequently combined with penetration, interface, crevice, interaction, corrosion, were used. This was followed up by extensive hand search using reference lists of relevant articles. Results Data in the literature have been gathered from extracted amalgam filled teeth and from artificially aged amalgam filled teeth. Corrosion studies have been performed in vivo aged teeth as well as in vitro. Sn is the main element, followed by Zn and Cu, that is consistently found in dentine underneath amalgam, as well as in amalgam corrosion products and in marginal seal deposits. Penetration of elements from amalgam has only been observed in discolored and in demineralised dentine. Conclusions Darkly discolored dentine as found underneath amalgam restorations contains amalgam corrosion products and is demineralised. Therefore it must be considered a different substrate for clinical procedures than sound dentine.

Influence of the biological fluid on the corrosion of dental amalgam

An electrochemical study of corrosion of Tytin ® dental amalgam was carried out in electrolytes similar to body fluids: artificial saliva with or without lactic acid, a polymer-containing product of the same composition as Glandosane ® and in Krebs–Ringer solution. The electrochemical techniques of open circuit potential, polarisation curves, cyclic voltammetry and electrochemical impedance were employed as a function of immersion time to characterise the surface processes occurring and bring out the differences between the different solutions. The influence of pH was tested in solutions of artificial saliva with or without lactic acid. The results demonstrated the importance of the organic component on the rate of corrosion and of adsorption phenomena on the amalgam surface.

Oral lichen planus and dental materials: a case-control study.

The purpose of this study was to examine the association of dental materials with oral lichen planus (OLP) and, particularly, the effects of amalgam, amalgam corrosion status, gold and dissimilar metals in continuous contact. A case-control study was performed with 43 OLP cases from the Oral Medicine Clinic at the School of Dentistry, University of Washington and 78 controls from a general dental care-screening clinic, also at the School of Dentistry, University of Washington. Health histories and oral examinations were obtained. Current metal or metal-based restorations were charted, along with corrosion status of amalgams and the presence of dissimilar metals in continuous contact. Adjusted odds ratios (ORs) and 95% confidence intervals for the following potential risk factors were found to be: (1) number of teeth with amalgam, OR = 1.02 (0.92, 1.13); (2) total surfaces of amalgam, OR = 0.96 (0.92, 1.0); (3) number of teeth with gold, OR = 1.12 (0.95, 1.31); (4) mean amalgam corrosion score, OR = 5.74 (2.34, 14.1); (5) presence of dissimilar metals in contact (per quadrant), OR = 1.25 (0.81, 1.92). These findings suggest that although the presence of amalgam or gold themselves is not associated with increased risk of OLP, corrosion of amalgams and the presence of a 'galvanic effect' from dissimilar dental materials in continuous contact (bimetallism) are associated with an increased risk of OLP.

Copper allergy from dental copper amalgam?

A 65-year-old female was investigated due to a gradually increasing greenish colour change of her plastic dental splint, which she used to prevent teeth grinding when sleeping. Furthermore, she had noted a greenish/bluish colour change on the back of her black gloves, which she used to wipe her tears away while walking outdoors. The investigation revealed that the patient had a contact allergy to copper, which is very rare. She had, however, had no occupational exposure to copper. The contact allergy may be caused by long-term exposure of the oral mucosa to copper from copper-rich amalgam fillings, which were frequently used in childhood dentistry up to the 1960s in Sweden. The deposition of a copper-containing coating on the dental splint may be caused by a raised copper intake from drinking water, increasing the copper excretion in saliva, in combination with release of copper due to electrochemical corrosion of dental amalgam. The greenish colour change of the surface of the splint is probably caused by deposition of a mixture of copper compounds, e.g. copper carbonates. Analysis by the X-ray diffraction technique indicates that the dominant component is copper oxide (Cu 2O and CuO). The corresponding greenish/bluish discoloration observed on the back of the patient's gloves may be caused by increased copper excretion in tears.

Corrosion of titanium and amalgam couples: Effect of fluoride, area size, surface preparation and fabrication procedures

Objectives. The aim of this investigation was to study the effect of surface treatments and electrode area size on the corrosion of cast and machined titanium in contact with conventional and high-copper amalgams in saline solutions with and without added fluoride ions. Methods. The potentials and the charges transferred between amalgam and titanium couples were registered using standard electrochemical methods. Results. Conventiional amalgam corroded more than high-copper amalgams in contact with titanium in saline solutions. Adding fluoride to the solution made the titanium potential more active and enhanced the corrosion of titanium in combination with high-copper amalgams. The amalgam corrosion increased with a five-fold enlargement of the titanium area. The increase was significant for one titanium-amalgam combination. Surface preparations affected the electrochemical behavior, and surface alterations were occasionally observed on wet-ground titanium specimens. No significant differences were found in comparisons of cast and lathe-cut titanium. Significance. Surface preparations and fluoride affect the electrochemical activity of titanium.