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At least 685 records · Page 38Linked to original sources
PubMed1976

Physical properties of dental amalgam containing metal pins.

No type of pin inclusion investigated in this study produced consistent increases or decreases in the strength of amalgam specimens under a variety of loading conditions and specimen ages. However, comparison of relative values for specimens tested under the same conditions showed that the highest fracture loads were found more often for specimens containing threaded gold pins than for any other type of specimen.

Chemical Phenomena↗
PubMedDate not supplied

The release of mercury from dental amalgam and potential neurotoxicological effects.

OBJECTIVES: The aim of this study was to estimate the amount of mercury released into both air and saliva from fresh and aged, abraded amalgam discs and then investigate neurotoxic effects of inorganic mercury upon sensory neuronal cultures. METHODS: An air-tight chamber was constructed to allow the combined estimation of mercury species released from amalgam pellets. The level released into air and saliva from both freshly packed and aged-abraded amalgam pellets was assessed. Dorsal root ganglia cultures from male CBA mice were exposed to 1 and 10 microM mercuric chloride concentrations. The effects of this were assessed by means of morphology, adhesion, size and immunocytochemistry. RESULTS: The mercury released into air from dry fresh amalgam was low and less than the recommended industrial exposure limit for mercury. However, covering the discs with saliva reduced air-mercury levels by 46-56% and there was a statistically significant difference in the air-mercury levels recorded (p=0.013-0.048). The mercury released into air from dry abraded amalgam was shown to be above the recommended industrial limit. Coating the abraded amalgam discs with saliva reduced the mercury by 66-72% with the levels recorded being significantly lower (p<0.001). The level of total mercury within the saliva was found to be highly variable. Little change was noted in the neuronal cultures treated with 1 microM mercuric chloride. However, the cultures exposed to high level (10 microM) mercuric chloride showed cells that became rounded and clumped together indicating pathological change. CONCLUSIONS: Amalgam placement appears to present minimal mercury exposure risk. To reduce the amount of mercury released into air, however, amalgam should be polished in a moist atmosphere with high volume aspiration. The neurotoxic effect of mercury appears to be related to concentration, as only in the cultures treated with 10 microM mercuric chloride showed striking qualitative and quantitative cellular changes.

Air↗
PubMedDate not supplied

[Microhardness of dental amalgam influenced by contact with cavity varnish].

The VICKERS micro-hardness was measured in the central and marginal areas of amalgam restorations. Two periods of observation were done: 24 and 168 hours after packing. A micro-hardness decreasing at the marginal areas were observed when the cavity varnish was used. The increasing of hardness was dependent on the age of the specimens. The central area of the restoration showed higher micro-hardness values than the marginal ones.

Dental Amalgam↗
PubMedDate not supplied

Dental amalgam: success or failure?

A review of recent literature suggests that reasons for amalgam failure can generally be identified and avoided. These include: retentive failure, marginal breakdown, fracture of the tooth or restoration, reasons for sensitivity, poor surface characteristics, and contributions to periodontal disease. Materials themselves are least often the source of problems; rather, most of the failures can be attributed to lack of attention to detail in cavity preparation and handling of the materials.

Dental Amalgam↗
PubMed1987

Adaptation of dental amalgam to the cavosurface margin of Class I cavity preparations.

The adaptation of a range of amalgam alloys to the cavosurface margin of Class I cavity preparations was examined for two condensation techniques. The marginal contour of amalgam condensed into the cavity preparation and packed approximately 1 mm past the cavosurface margin was compared with amalgam margins of restorations which were packed to final contour with minimal carving. The effect of burnishing and/or polishing the cavosurface margin was compared with carving the amalgam to the cavosurface margin. Specimens were sectioned, metallographically polished and examined using a light microscope. The technique of overpacking amalgam produced a greater number of acceptable amalgam margins at the cavosurface margin than the condensation technique of packing to final contour, the best cavosurface margin was produced when specimens were burnished and polished, the carved margin being the least desirable. The cuspal incline also influenced the quality of the marginal finish with the difficulty of marginal finishing increasing with the steepness in cuspal incline.

Dental Alloys↗
PubMed1995

[Effects of new dental amalgam fillings in pregnancy on Hg concentration in mother and child. With consideration for possible interactions between amalgam and precious metals].

Amalgam-tooth fillings are suspected to be cause of many different diseases. With special consideration of the problem of newly made fillings, blood samples were taken from 45 affected pregnant women. After birth, newborns and placenta tissue were tested for Hg-contamination. One hundred and twenty one women with older amalgam-fillings were compared to 19 women without amalgam-fillings. The surfaces of the amalgam-fillings were measured in each case in mm2. In 58 women the tooth fillings contained additional precious metal. While in the placentas a retaining function were found of up to ten times higher Hg-values but low correlations to the amalgam surfaces, the Hg-concentrations in the blood samples of mother and child did not correlate to the amalgam-fillings. Newly made fillings during pregnancy had no influence on the Hg-concentration, neither had the contact to precious metals in the approximal and the antagonistic range. The wide-spreading of Hg-values without correlation to the filling-surfaces speaks for a great influence of other environmental factors.

Adult↗
PubMed1991

[Tarnishing, discoloration and corrosion of dental amalgams in vitro].

The purpose of this paper was to observe changes occurred on the surface of some amalgams commonly found in the national market in order to evaluate tarnishing, darkening and corrosion on polished and non-polished surfaces. The method used was alternate immersion in bidestilled water, and 50% acetic acid, 14.5% lactic acid. A control, for comparative purposes, was not submitted to immersion but left in normal environmental conditions.

Acetates↗
PubMed2002

A history of dental amalgam.

OBJECTIVES: Silver amalgam alloy has been used as a dental restorative material since the beginnings of restorative dentistry. It rose as an easily manipulated and low cost material in comparison to other restorative techniques of the time, but it had poor dimensional stability and clinical behavior. Successive research led to the standardization of both its composition and some aspects of its mechanical properties, which have contributed to its widespread acceptance. Nevertheless, the risk of environmental toxicity generated by mercury and its poor esthetics have given rise to the search for alternative and more promising materials. This article endeavors to give a brief historical description of the main events which have led to development of modern silver amalgam alloys. SIGNIFICANCE: It is concluded that extensive knowledge of the use of silver amalgam alloy has made it the most widely used restorative material for the posterior oral cavity. However, in recent years its preponderance has been brought into question even though some innovative ideas have been suggested which could help improve this material in the future.

Asia↗
PubMed1980

Clinical assessments of dental amalgam restorations.

In assessing the performance of amalgam restorations in most clinical studies, the significant factor to evaluate is marginal fracture. The clinical relevance of marginal fracture is reflected in its relationship to the presence of secondary caries. Furthermore, whereas most other failures can be avoided by proper operator technique, marginal fracture is an inherent deficiency of amalgam restorations. Although the extent of marginal fracture can be influenced by many factors, the nature of the alloy has been found to play a major role. However, for a properly conducted study, other factors which include the operator, patient and tooth type should be acknowledged in the research design. To evaluate marginal fracture in clinical studies, the occlusal photograph--visual assessment technique is a most sensitive method and the scoring of test restorations according to a standard set of photographs has several significant advantages.

Dental Alloys↗
PubMed1976

The rate of development of strength in base forming materials for dental amalgam.

Eleven base forming materials used under amalgam restorations were examined for the rate of development of their compressive and tensile strengths. Materials from three categories were compared. Under in vitro conditions of testing, it was found that, immediately after a state of clinical set had been reached, the quick-setting zinc oxide-eugenol materials possessed strengths significantly greater than the calcium hydroxide cements but significantly weaker than the zinc phosphate cements. Calcium hydroxide cements possessed the lowest compressive strength to tensile strength ratio and modified zinc oxide-eugenol materials the highest.

Calcium Hydroxide↗
PubMed1992

Effect of polishing burs and stones on the micro-hardness of dental amalgam.

Square standard cavities were prepared in human teeth and restored with amalgam obtained from alloys of different trade-marks. Twenty-four hours after condensation, excess amalgam was removed from three of the four margins, each with a different rotatory instrument (number 4 bur, multiblade finishing bur, and fine green stone). No rotatory instrument was used on the fourth margin (control), and this control was polished with pumice and zinc-oxide pastes and Sweeney's brushes. Vickers' tests for micro-hardness of the amalgam were performed on the four margins of the restorations. The restorations were then submitted to metallographic polishing, and a second micro-hardness measurement was made seven days later. The statistical analysis of the data showed that micro-hardness values were higher at the margins on which no rotatory instruments were used. The lowest micro-hardness values were found at the margins where finishing and/or round burs were used. Polishing with fine green stones gave intermediate values.

Analysis of Variance↗
PubMed1983

Polishability of dental amalgam as influenced by condensation pressure and primary mercury content.

The polishability of some amalgam products was studied by determining the roughness (Rs) of metallographically polished specimens. The surface porosity of the specimens was also measured and was found to be closely correlated with the roughness. Two manipulative variables, condensation pressure and primary (precondensation) mercury content, were examined with respect to their effect on porosity and polishability. For the condensation pressures 14 and 20 MPa no differences could be observed in the effect on the surface properties studied. The primary mercury content was varied in three steps--the normal, recommended level and 5% more and less than this. For those products having a recommended precondensation mercury content of 50% or less, the 5% decrease in mercury resulted in a pronounced increase in porosity and Rs. The results indicate that polishability is for some products markedly improved by avoiding a dry mix.

Dental Amalgam↗
PubMedDate not supplied

Microleakage of a dental amalgam alloy bonding agent.

Amalgambond (a 4-META derivative resin bond agent) was evaluated for its effectiveness in reducing microleakage compared to copal varnish and no lining agent in class 5 amalgam preparations restored with either an admix alloy (Dispersalloy) or a spherical alloy (Tytin). Teeth were thermocycled between 5 and 55 degrees C with two 4-META/amalgam groups additionally aged in 37 degrees C water for 30 days prior to thermocycling. Nonaged, 4-META/amalgam restorations showed significantly less microleakage (P < 0.05) at enamel and dentin margins compared to copal varnish or nonlined restorations. Within the 4-META groups, the 4-META/Dispersalloy restorations had significantly less microleakage than the 4-META/Tytin restorations at enamel margins. Microleakage in the aged 4-META/amalgam restorations was significantly greater at both the enamel and dentin margins than in the analogous nonaged groups. SEM evaluation of the 4-META lined restorations found internal cavity surfaces of the preparations to be sealed by the resin liner with separations and apparent microleakage occurring at the 4-META/amalgam interface.

Analysis of Variance↗