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PubMed1988

Corrosion behavior and microhardness of three amalgams.

The marginal microhardness of three different types of amalgam was tested after 2 months' immersion in an aqueous solution of NaCl (85 mM) and phosphates (Na2HPO4 100 mM and NaH2PO4 100 mM). Amalgams immersed in distilled water were used as controls. The microhardness tests were conducted at a distance of 50 micron from the margins and at the bulk of each specimen. The solutions were analyzed for Sn, Cu, Zn, Ag, and Hg by means of atomic absorption spectrophotometry (AAS). A statistically significant reduction in the marginal microhardness after immersion in the test solution was found for the conventional and the high-Cu single composition amalgam but not for the high-Cu blended amalgam. SEM-examination of cross-sections of the amalgams revealed small areas of subsurface grain boundary corrosion, no deeper than 10 micron for all the amalgams. The SEM-examination of the specimens and AAS analysis of the solutions indicated that the reduction in marginal microhardness was attributed mainly to corrosion of the Cu-rich phases for the high-Cu single composition amalgam and to corrosion of the gamma 2 phase for the conventional amalgam. The phosphates reduced the corrosion of the amalgams in the presence of NaCl. It is concluded that the marginal strength of dental amalgams in a corrosive environment is largely dependent upon their corrosion resistance.

Copper↗
PubMedDate not supplied

Microleakage of a consolidated silver direct filling material.

Microleakage of an experimental direct filling material comprised of a chemically precipitated silver powder that had been surface treated with a dilute acid to promote cold welding upon consolidation was evaluated. Microleakage was compared to both dispersed-phase and spherical amalgam by use of an in vitro gas-diffusion method and in class 5 restorations placed in extracted human teeth. The effect of two cavity varnishes and two dentin adhesives as cavity liners on microleakage was also evaluated using extracted teeth. Microleakage of silver powder consolidated with dental instruments was less than that found with dental amalgam. The use of copal or polyamide cavity varnish resulted in the lowest combination of microleakage on dentin and enamel margins.

Analysis of Variance↗
PubMed1995

Copper band matrix for large Class V amalgam restorations.

Class V cavities present special problems in restoration and maintenance. The subsequent health of the gingival tissue and the relative immunity toward recurrent caries depends not only on the age of the patient and patient's oral hygiene but to a great extent on the excellence of the restoration. This excellence is achieved by the operator's detailed design of the preparation, moisture control, and restoration and material finishing. Dental amalgam continues to be the material of choice in many clinical situations. The restoration of a large class V lesion that results from replacement of a defective restoration or extensive caries benefits greatly when a copper band matrix is used because of its ability to be shaped and contoured and its rigidity. In large class V cavities, the copper band creates a "false" wall that is required for confinement of the amalgam as it must be packed under pressure. This confinement of the cavity is necessary because it restricts the amount of excess material which ultimately is important in the restoration of the tooth and its long-term success.

Copper↗
PubMed1978

[Studies of the edge-strength of some silver-zinc amalgams Part I: Creep value (author's transl)].

From a compilation of all investigative results it is apparent that there are only minor differences in edge-strength between the AP preparations and VH 67 grade. Showing the best values within this particular group is the AP 3 grade. Its use as a filling material may be expected to yield the best results as regards durability. In contrast, the results obtainded for the VH 50 grade material cannot be regarded as satisfying the requirements of a dental amalgam. A marked tendency toward creeping and high rates of corrosion result in the edge-strength of this material being reduced to an unacceptable level.

Corrosion↗
PubMed1999

Expansion of contaminated amalgams assessed by photoelastic resin.

OBJECTIVE: Eight amalgam alloys, 6 high-copper and 2 low-copper, were assessed for expansion via photoelastic resin. METHOD AND MATERIALS: The photoelastic resin sheet was sectioned into 20 x 25-mm blocks, and two 4 x 8-mm holes were drilled into the resin. The amalgam alloys were hand condensed into the prepared holes. Test conditions for each alloy were (1) uncontaminated, (2) contaminated with 5 microL of Ringer's solution, and (3) contaminated with 5 microL of cell culture medium. RESULTS: Contaminated high-copper amalgam alloys may exhibit expansion to varying degrees but do not show the classic delayed expansion. One spherical, nonzinc high-copper alloy showed no expansion, whether it was uncontaminated or contaminated, and 3 high-copper alloys with different amounts of zinc (0% to 1%) showed slight expansion when contaminated. One low-copper alloy displayed delayed expansion; within 17 days after initial expansion in the photoelastic resin, it had exceeded the greatest stress observed in any contaminated, high-copper zinc-containing alloy at 3 months. CONCLUSION: Contamination of dental amalgam is to be avoided, but a zinc-containing high-copper amalgam will not exhibit classic delayed expansion even if contaminated.

Birefringence↗
PubMed1993

Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The annual review of selected dental literature this year cites 384 published papers and reports. This year's review contains more editorial comment than reviews of years passed. New data on the biological responses to materials is emphasized in several sections. Observations on new compounds able to prevent plaque formation are presented. Clinically relevant advances in knowledge concerning the etching of different tooth structures are reported along with the effect of etching procedures on the dental pulp. Evaluation of periodontal diseases in all age groups is a topic. Limitations of current diagnostic techniques in periodontal disease, temporomandibular disorders, and implant therapy are included. There are new views on the use of dental amalgam. The future use of dental mercury is predicted. Interest in new ceramic systems is indicated as the demand for esthetics continues. Clinical information is emphasized over scientific information throughout this year's review.

Dental Implants↗
PubMed2001

Thomas B. Welch, MD, DDS: journalist, innovator and grape juice king.

Dr. Thomas B. ("T.B.") Welch was not an ordinary man. An inventive, creative and deeply religious individual, he intermittently practiced three professions--the ministry, medicine and dentistry. In his role as a minister, he developed a pasteurized, unfermented grape juice to be used during the communion service. He believed that he was truly serving God by enabling parishioners to partake a non-alcoholic "fruit of the vine." At that time, wine (the alcohol-containing "cup of devils") was traditionally used. Although T.B.'s efforts were in vain, those of his son, Charles ("C.E.") Welch were far more successful. C.E. had greater entrepreneurial talents than his father. By the time Charles died in 1926, he had made Welch's Grape Juice a familiar household product. As a distinguished New Jersey dentist. Dr. Tom made many contributions to his profession. He greatly improved the quality of dental amalgam and cement, and his dental products were so successful commercially, that he quit the practice of dentistry sooner than anticipated. Additionally, he created, edited and wrote Dental Items of Interest, a professional journal with the second largest circulation in the country. Later, he edited several other dental journals. Of his seven children, three sons and one daughter followed him into the dental profession. T.B. was also a gifted poet. Possessing a keen interest in the English language, he attempted to simplify spelling by using phonetics. However, this endeavor failed.

Beverages↗
PubMed1993

Compositions of surface layers formed on amalgams in air, water, and saline.

The surface layers formed on both a zinc-free and a zinc-containing dental amalgam after polishing and aging in air, water, or saline, were characterized using x-ray photoelectron spectroscopy (XPS) to determine the compositions of the surface layers which might govern the release of mercury from amalgam. The XPS data revealed that the formation of the surface layer on the zinc-containing amalgam was affected by the environment in which the amalgam was polished and aged, whereas that on the zinc-free amalgam was not affected. In addition, among the elements contained in amalgam, zinc was the most reactive with the environment, and was preferentially dissolved from amalgam into water or saline. Mercury atoms existed in the metallic state in the surface layer.

Air↗
PubMed1992

Amalgam--fact and fiction.

A brief history of amalgam is given, stressing the role of G. V. Black. The background and the progress of the two Amalgam Wars are sketched. Aspects are presented of the drawbacks of amalgam with respect to toxic effects of, especially, mercury vapor and corrosion products. An account is given of some frequent fallacies concerning the health hazards of dental amalgam fillings and the role of psychosocial factors in the development of illness attributed to amalgam is emphasized.

Dental Amalgam↗
PubMed2001

The amalgam controversy. An evidence-based analysis.

BACKGROUND: There are a number of patients and health care professionals who believe dental amalgam restorations are a factor in a host of diseases and conditions. They have been influenced by anecdotal case reports in the medical and dental literature, research published in the refereed literature and media stories concerning the alleged dangers of amalgam restorations. METHODS: The author uses an evidence-based approach in analyzing the data both supporting and condemning the continued use of amalgam restorations. He reviewed the articles from both peer-reviewed and non-peer-reviewed sources and evaluated their relevance, research design and statistical analysis, as well as whether the conclusions follow from the data. CONCLUSIONS: There are numerous logical and methodological errors in the anti-amalgam literature. The author concludes that the evidence supporting the safety of amalgam restorations is compelling. CLINICAL IMPLICATIONS: Amalgam restorations remain safe and effective. Dentists should educate patients and other health care professionals who may be mistakenly concerned about amalgam safety.

Corrosion↗
PubMed2001

Microleakage in primary teeth restored by conventional or bonded amalgam technique.

The aim of this in vitro study was to evaluate marginal leakage in class V restorations in primary teeth restored with amalgam, using three different techniques. Thirty maxillary anterior primary teeth, clinically sound and naturally exfoliated, were used. In group 1 (n = 10), two thin layers of a copal varnish (Cavitine) were applied. In group 2 (n = 10), Scotchbond Multi-Purpose Plus, a dual adhesive system, was used according to manufacturer instructions. In group 3 (n = 10), One-Step adhesive system in combination with a low-viscosity resin (Resinomer) were used according to manufacturer instructions. All samples were restored with a high-copper dental amalgam alloy (GS 80, SDI). After restoration, the samples were stored in normal saline at 37 degrees C for 72 h. The specimens were polished, thermocycled (500 cycles, 5 degrees and 55 degrees C, 30-s dwell time) and impermeabilized with fingernail polish to within 1.0 mm of the restoration margins. The teeth were then placed in 0.5% methylene blue for 4 h. Finally, the samples were sectioned and evaluated for marginal leakage. The Kruskal-Wallis test showed that the filled adhesive resin (group 3) had the least microleakage. There was no significant difference between groups 1 and 2.

Composite Resins↗
PubMed1990

[Apicoectomy and reverse filling procedure in posterior teeth].

In this paper, we present the apicoectomy with reverse filling procedure in posterior teeth, as an alternative surgical method, in those cases where conservative endodontic treatment is unable or fails to bring successful results (prosthetic restorations, broken instruments, calcified and tortuous root canals, dens in dente, unfinished root apex). We choose to restrict our presentation in posterior teeth where the surgical procedure is more difficult due to anatomical conditions (maxillary sinus, mandibular canal, number of root canals, inaccessible posterior oral cavity, etc). We analyse the indications of such an operation and the elements we examine to evaluate the cases. We are showing the different stages of the operation as well as the usage of original instruments for the retrograde amalgam procedure. There is a further discussion on problems from the usage of the filling material, the dental amalgam, and, the problems throughout the procedure (level and degree of the apical bevel, cavity preparation, etc).

Apicoectomy↗
PubMed2005

Artefacts in magnetic resonance imaging caused by dental material.

A common problem in computer tomography (CT) based imaging of the oral cavity is artefacts caused by dental restorations. The aim of this study was to investigate whether magnetic resonance imaging (MRI) of the oral cavity would be less affected than CT by artefacts caused by typical dental restorative alloys. In order to assess the extent of artefact generation, corresponding MRI scans of the same anatomic region with and without dental metal restorations were matched using a stereotactic frame. MRI imaging of the oral and maxillofacial region could be performed without reduction of the image quality by metallic dental restorations made from titanium, gold or amalgam. Dental restorations made from titanium, gold or amalgam did not reduce the image quality of the MRI sequence used in imaging of the oral and maxillofacial region for dental implant planning. In this respect MRI is superior to CT in implant planning.

Animals↗
PubMed2003

Effect of amalgam fillings on the mercury concentration in human amniotic fluid.

BACKGROUND: Methyl mercury (MeHg) and metallic Hg are well known as neurotoxic agents. Dental amalgam contributes significantly to elemental Hg vapour exposure in the general population. There is little information about Hg concentration in human amniotic fluid (AF) of pregnant women and its potential toxic effect on the fetuses. OBJECTIVE: Primary to assess the relationship between the presence of detectable mercury (Hg) concentration in human AF, number and surface areas of amalgam fillings of pregnant women; secondary to analyse their obstetric history and perinatal complications. METHODS: Seventy-two pregnant women took part in this prospective study. One dentist recorded the dental status, presence, number and surface areas of amalgam fillings. Total Hg concentration in AF was determined in digested samples using automatic cold vapour atomic absorption equipment. The detection limit of Hg in AF, determined from blank readings, was 0.08 ng/ml. To estimate the dependence of the explanatory variables (such as number and surface areas of amalgam fillings, fish consumption, presence of liver or neurological diseases and smoking habits) on mercury concentration several linear regression models were built up. Stepwise logistic regression procedures were running on total sample and on patients with at least one amalgam filling (Positive Filling group = PF). Principal component analysis (PCA) provided two factors, which explained for more the 60% of the variance among the variables. RESULTS: The overall mean Hg concentration in AF among all patients was 0.37+/-0.49 ng/ml. Nineteen (26.4%) women had a Hg concentration <0.08 ng/ml (Hg negative group). In 53 (73.6%) patients, with a concentration > or = 0.08 ng/ml (Hg positive group), the mean value of Hg was 0.49+/-0.52 ng/ml. The average number of amalgam fillings was 2.26 +/- 3.19 in the Hg negative group and 5.32+/-3.03 in the Hg positive group (ANOVA one-way p=0.04). A dependence of mercury concentration on number of amalgam fillings (p=0.03), surface area of the amalgam fillings (p=0.04) and fish consumption (p=0.04) was observed but not at a significant level. In stepwise logistic procedure the number of amalgam fillings gave a contribution to the model (p=0.04), although null value was included in the confidence intervals. We observed no statistically significant differences (chi2 test) among the patients with a Hg concentration <0.08 ng/ml (n=19) and those with a concentration > or = 0.08 (n=53) with regard to obstetric history and perinatal complications. CONCLUSIONS: Number and surface areas of amalgam fillings influenced positively Hg concentration in AF but not at a significant level. Moreover Hg levels detected in AF were low and no adverse outcomes were observed through pregnancies and in the newborns.

Adult↗
PubMed2006

Marginal adaptation and micro-porosity of class II restorations of a high copper amalgam and a palladium-free gallium-based alloy.

The aim of the current investigation was to compare the marginal adaptation and internal porosity of a gallium (Ga)-based alloy (Galloy) with a high copper amalgam (Permite C DP) when used in moderately sized conventional class II cavities. Ten dentists placed two restorations of each material in standardized class II cavities in typodont teeth set in a phantom head. The proximal surfaces of the restored teeth were subsequently examined using an optical microscope and colour photographs were taken. The teeth were then serially sectioned before being re-examined microscopically and re-photographed. Three dentists rated the photographs of the restorations on two occasions, 2 weeks apart, for marginal adaptation and internal porosity using a six and five point scoring criteria, respectively. Inter- and intra-examiner agreements were assessed with weighted kappa statistics. The Ga-based alloy exhibited inferior marginal adaptation and a significantly higher level of porosity and internal defects compared with the dental amalgam. Marginal defects were mainly concentrated at the gingival third of the proximal boxes for both alloys. The poor marginal adaptation and extensive internal porosity detected for the Ga-based alloy was attributed to the difficulty in the alloy condensation related mainly to the 'stickiness' of the alloy to the condensers and to the rapid change in the plasticity of the alloy during condensation. This could possibly be a factor in the post-operative complications reported with the clinical use of this alloy.

Copper↗