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Perceptual and motor training for the acquisition and retention of psychomotor skills in dental amalgam restorations: class I in the mandibular first molar.

From a study of 72 dental students during amalgam restoration using four training methods (psychomotor, mental, psychomotor and mental, and conventional)--one method for each 18 students--the following conclusions are drawn: (1) It is economically feasible to develop and utilize self-paced instructions without the aid of instructors for the acquisition of psychomotor skills. (2) Training through self-paced analytical programs results in higher retention of the acquired skills than training through conventional training methods.

Dental Amalgam↗

Dynamic mechanical properties of dental amalgams.

The dynamic mechanical properties of two high-copper amalgams (Tytin and Dispersalloy) and two traditional amalgams (Aristalloy and Aristalloy with Zn) were measured over a temperature range of 0-70 degrees C and at frequencies of 0.1, 1, and 10 Hz by means of a DuPont DMA. Values of storage modulus (E') for the amalgams were equivalent to the Young's modulus (E) measured from static mechanical test methods, with Dispersalloy demonstrating the highest moduli. Values of E' decreased with increased temperature. E' of traditional amalgams decreased more rapidly than did those of the Cu-rich amalgams. Values of loss modulus (E") for Tytin were smaller than those of Dispersalloy and the two types of Aristalloy. High values of E" for the traditional amalgams correspond to a greater viscous behavior. Marked differences between the magnitude of tan delta and its temperature coefficients for traditional and high-copper amalgams were observed, which is indicative of differences in visco-elastic behavior between these two amalgam systems.

Copper↗

Creep as a mechanism for sealing amalgams.

Dental amalgam seals itself over time. The reduction of microleakage in amalgam restorations has been explained by corrosion products filling in the interface gap between amalgam and tooth structure in order to seal the restoration interface. This concept has been widely accepted; yet, curiously, there is little research supporting this theory. The creep mechanism may be a plausible alternative to explaining why microleakage is reduced over time in amalgam restorations. Amalgam restorations are confined to the fixed space of the cavity preparation; expansion of the amalgam through internal phase changes in this confined area must be relieved. The resultant creep-expansion of the amalgam restoration fills in the tooth/amalgam interface gap. Once the interfacial gap is filled and amalgam has made intimate contact with the cavity wall, the dental amalgam slides along the tooth preparation plane as predicted by classic metallurgical studies. The results of the creep of amalgam have been observed clinically as the extrusion of amalgam from the cavity preparation. This explanation for amalgam sealing the tooth/amalgam gap fits many clinical observations and certain research data.

Corrosion↗

Ions released from dental amalgams in contact with titanium.

The ions released from conventional and high-copper amalgams in contact with titanium were quantitatively analyzed in a 0.9% NaCl solution at 37 degrees C when the surface area ratio of titanium/amalgam was set up as 1/10, 1/1, or 10/1. The corrosion potentials of the amalgams and titanium were measured under the same conditions. Surface analyses on the amalgams were also employed using SEM with WDS. Though the potential of the conventional amalgam was always lower than that of titanium, that of the high-copper amalgam was reversed during the early stage of immersion and remained lower. When the surface area ratio of titanium grew at 10/1, tin and copper ions released from the conventional and high-copper amalgam, respectively, increased significantly compared with those of each amalgam that was not in contact with titanium. The galvanic corrosion in such a large surface area of titanium possibly led to the heavy corrosion of the amalgams.

Copper↗

The distribution of mercury in various tissues of guinea-pigs after application of dental amalgam fillings (a pilot study).

Mercury accumulation in brain, kidney, liver and heart following insertion of amalgam in the teeth of guinea-pigs has been studied. During the accelerated wear of the amalgam in these gnawing animals, a significant mercury accumulation in the above tissues was demonstrated. Finely diffused and abraded amalgam must not be ignored as a source of absorbable mercury.

Animals↗

Rapid communication: acute exposure to mercury from dental amalgam does not affect the levels of C-reactive protein or interleukin-6 in peripheral blood.

In a previous study, a significant increase in serum interleukin-6 (IL-6) was apparent after an acute low-level mercury (Hg) exposure, achieved by removal of amalgam fillings (Loftenius et al., 1998). In the present study, 11 healthy volunteers were exposed to an oral dose of 1 g of pulverized amalgam powder. Hg, IL-6, and C-reactive protein (CRP) levels in plasma were followed before and up to 72 h after exposure. The Hg levels were low and stable prior to exposure and increased rapidly after exposure. The median Hg increase was 12.9 nmol/L, which is considerably higher than in the previous study. No significant change over time was observed for IL-6 and CRP levels. Therefore, it cannot be ruled out that our previous finding of increasing IL-6 levels detected after acute low-level Hg exposure through removal of amalgam fillings was due to the dental treatment per se.

Administration, Oral↗