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PubMed1977

Microstructure of dental amalgams containing high and low copper contents.

Microstructure of commercial dental alloys and their amalgams were studied primarily by x-ray diffraction, optical metallography, scanning electron microscopy, and x-ray energy dispersive spectroscopy. X-ray diffraction revealed more phases than normally reported in these materials. Presence of new phase was discussed and their formation mechanism understood. Some phases having interacting 2 theta degrees values with others were properly identified. Both new and conventional dental alloys and their amalgams, namely Tytin, Sybraloy, Dispersalloy, Kerr Spheraloy, Caulk Spherical, Shofu Spherical, and Caulk 20th Century Microcut were used to complete the investigation.

Chemical Phenomena↗
PubMed1999

Adhesion of bonded orthodontic attachments to dental amalgam: In vitro study.

Bonding orthodontic attachments to molars is difficult in the presence of extensive buccal amalgam restorations. The purposes of this study were (1) to examine different amalgam surface preparations, (2) to examine properties of adhesive cements to amalgam, (3) to determine the most shear-resistant bonding technique and (4) to discuss whether these shear bond strengths were of adequate magnitude to be of clinical acceptability. The sample consisted of 108 standardized amalgam cylinders divided into 9 groups of 12 based on surface treatment technique and resin type. SPEED brackets (Strite Industries, Cambridge, Ontario) were bonded to amalgam surfaces that were either polished, sandblasted with 50 microm aluminium oxide, or chemically corroded. Adhesives used were Phase II (Reliance Orthodontic Products Inc, Itasca, Ill), Panavia EX (J Morita USA Inc, Tustin, Calif), or C & B Metabond (Parkell, Farmingdale, NY). After thermocycling from 10 degrees C to 50 degrees C 10,000 times, all samples were tested for shear bond strength with the Universal Testing Machine (Instron Corporation, Canton, Mass). The results show significantly higher bond strengths for all of the resin systems when sandblasting of the amalgam surface is used (P <.0001). Only Panavia EX bonded strongly to polished samples, suggesting the presence of a chemical bond. Laboratory acceptable bond strengths to amalgam are possible. The surface characteristics of the amalgam appear to be more influential in the strength of the bond than does the nature of the resin.

Acid Etching, Dental↗
PubMed1992

Clinical evaluation of high-copper dental amalgams with and without admixed indium.

High-copper amalgam alloys containing 5% and 10% admixed indium, shown in previous studies to have improved properties and acceptable biological behavior, were evaluated in a clinical study designed to examine factors relating to clinical success. One hundred and seventy-five Class I and Class II amalgam restorations were placed in 25 patients. Each patient received all three dispersed-phase amalgams tested: without indium (Dispersalloy), with 5% indium (Indisperse 5), with 10% indium (Indisperse 10). After 30 months, 22 patients were recalled and 146 restorations evaluated. The margins of the indium-containing amalgam restorations incurred slightly less marginal breakdown, an effect that could be attributed to the addition of admixed indium and to the increase in silver-copper eutectic spheres which is found in these alloys. These amalgams also demonstrated a slightly darker appearance, and were slightly rougher than the non-indium-containing amalgam. These differences were minor; at 30 months, all restorations were well within the clinically acceptable range for each parameter evaluated.

Analysis of Variance↗
PubMed1980

The role of zinc in dental amalgams.

Twenty-five AG-Sn alloys containing various additions of Zn were amalgamated and the amalgams tested for physical properties pertinent to dental restoration use. The mercury retained, dimensional change, compressive strength, and creep were all functions of the Zn content.

Corrosion↗
PubMed1997

Mercury exposure from dental amalgam fillings: absorbed dose and the potential for adverse health effects.

This review examines the question of whether adverse health effects are attributable to amalgam-derived mercury. The issue of absorbed dose of mercury from amalgam is addressed first. The use of intra-oral Hg vapor measurements to estimate daily uptake must take into account the differences between the collection volume and flow rate of the measuring instrument and the inspiratory volume and flow rate of air through the mouth during inhalation of a single breath. Failure to account for these differences will result in substantial overestimation of the absorbed dose. Other factors that must be considered when making estimates of Hg uptake from amalgam include the accurate measurement of baseline (unstimulated) mercury release rates and the greater stimulation of Hg release afforded by chewing gum relative to ordinary food. The measured levels of amalgam-derived mercury in brain, blood, and urine are shown to be consistent with low absorbed doses (1-3 micrograms/day). Published relationships between the number of amalgam surfaces and urine levels are used to estimate the number of amalgam surfaces that would be required to produce the 30 micrograms/g creatinine urine mercury level stated by WHO to be associated with the most subtle, pre-clinical effects in the most sensitive individuals. From 450 to 530 amalgam surfaces would be required to produce the 30 micrograms/g creatinine urine mercury level for people without any excessive gum-chewing habits. The potential for adverse health effects and for improvement in health following amalgam removal is also addressed. Finally, the issue of whether any material can ever be completely exonerated of claims of producing adverse health effects is considered.

Absorption↗
PubMed2003

A resin alternative for posterior teeth: questions and answers on dental amalgam.

Amalgam has been used to restore cavities in posterior teeth for over 100 years, but formulations used today are different from those used a century ago. Amalgam restorations have been blamed for a number of problems, such as cusp fracture and higher rates of secondary caries. This article discusses these issues, along with possible toxic effects, in the light of current literature.

Composite Resins↗
PubMed1994

Dental amalgam--what are the alternatives?

Alternatives to amalgam include glass ionomer cements, direct placement composites, composite inlays, and ceramic inlays. Glass ionomer cements are suitable only in minimally stress-bearing areas but have the advantages of reliable adhesion and fluoride release. For the larger cavity, resin inlays offer a viable alternative to direct placement composites because of better control of contour and contact areas, and management of polymerisation shrinkage. However, there are reservations regarding the long-term marginal quality in view of possible wear of the cement lute. Ceramic inlays offer maximum aesthetics, but similar cement lute concerns have been expressed. The cost of the restoration to the patient is in the order direct resin < resin inlay < ceramic inlay. Tooth-coloured resin or ceramic alternatives to amalgam are indicated for aesthetic restoration of moderate lesions, in patients with good oral hygiene. Contraindications include high caries rate, inability to obtain perfect moisture control, heavy occlusal stress, and poor or absent marginal enamel.

Ceramics↗
PubMedDate not supplied

Bond strength of Panavia EX to dental amalgam.

The tensile bond strengths of Comspan (a conventional resin used with composite-bonded prostheses) and Panavia EX (a newer adhesive bonding material) to different types of amalgam were determined. The results were compared with the tensile bond strengths of these resins to etched bovine enamel and properly prepared Rexillium III. The results showed that all of the resin-amalgam bond strengths were statistically less than those of bonding resin to etched bovine enamel or Rexillium III. Coverage of existing amalgam restorations by the metal framework with etched-metal resin-bonded retainers is contraindicated when using either the conventional bonding agent or the new adhesive bonding material, Panavia EX.

Acid Etching, Dental↗
PubMed1984

Early prediction of long-term margin adaptation of dental amalgam restorations.

The present study assessed the predictive value of an indirect metric method for the early detection of margin defects of amalgam restorations, relative to results using a direct clinical method. The material consisted of plaster casts of amalgam restorations taken at 1- and 2-yr examinations of four different amalgam-treatment combinations. The widest margin defect of each restoration was measured in a dissection microscope equipped with a metric scale in the ocular. The ranking order obtained from the metric measurements of the different amalgam-treatment combinations after 1 and 2 yr was compared with that obtained from the direct clinical evaluation after 2 yr. Finally, the rank order of those restorations rated Alfa (no visible evidence, along the margin, of a crevice (ditch) into which an explorer will penetrate) at the 2-yr clinical examination was studied in relation to the 1-yr metric measurements. For the total material, the rank order based on the metric measurements of the margin defects of the four amalgam-treatment combinations agreed with that obtained with the clinical rating. In the 1-yr data, where the metric technique was applied only on the restorations rated Alfa at the 2-yr clinical evaluation, the order of two neighboring combinations was reversed; otherwise the same rank order was obtained. It is recommended that the clinical performance of new brands of amalgam alloy are tested in short-term, small-scale studies using the metric evaluation technique, before more extensive field studies over longer periods are instituted, in order to sort out unsatisfactory materials and treatment techniques at an early stage.

Child↗