Impression pastes

The ZOE impression paste is used in taking impressions of the mouth prior to constructing a denture. It is used as a corrective impression material after a preliminary impression has been taken (Phillips, 1982a). A preliminary impression lacks detail so it is necessary to take a secondary or corrective impression which is placed on a tray that has the contours of the preliminary impression. 

The ZOE impression paste is essentially a two-paste ZOE cement. One paste is formed by plasticizing the zinc oxide powder with 13 % of mineral or vegetable oil. The other paste consists of 12% eugenol or oil of cloves, 50% polymerized rosin, 20% silica filler, 10% resinous balsam (to improve flow) and 5 % calcium chloride (accelerator). 

Surprisingly, although the material has been in use for over 100 years, the cement structure has yet to be fully elucidated. 

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The compositions of zinc oxide—eugenol impression pastes are similar to those of the zinc oxide—eugenol cements (86). Variations in specific characteristics are achieved by the proportions of the ingredients (87). Properties vary in commercial products (88). The modifications of the zinc oxide—eugenol system intended for bite-registration pastes may include agents to increase the body or thixotropic character of the unset mix to improve... 

Zinc oxide—eugenol impression pastes are used primarily as corrective washes over compound impressions, as veneer impressions, as temporary liners or stabilizers in base-plates and dentures, and as bite-registration pastes for recording occlusal relationships in inlay, crown, and bridge techniques. 

The test methods for zinc oxide impression pastes are outlined in ADA specification no. 16 and Federal specification U-1-500. 

It was through the translation and diffusion of this recent, but already impressive, past that Russian literature acquired its international... 

Paffenbarger (12) indicates that dental cements are used as filling materials, luting media, obtundent dressings, impression pastes, and as bases for other restorative materials. He lists six classes of cements. Today, a seventh class, the glass-ionomer cements, may have to be added to his classification, since these products straddle his classes C-4 and C-5 compositionally. 

At the moment, most scientists and students, both in companies and at universities, use similar tools for the encoding processes described. But this was not the case in the past, when research was much more differentiated and fascinating with regard to the chemist-computer interaction. Some of these old-fashioned results are still impressive or some are still used, even now, as the following examples illustrate. 

Disclosing waxes or pressure indicating pastes, are used in fitting a dental appHance to estabhsh the location and extent of high spots or pressure areas, as on impressions and complete dentures. They are very soft, salve-like compositions that are painted onto the tissue side of an impression or denture. When the wax-coated denture is seated in the mouth, the soft paste is forced out of the areas showing hard contact between the denture and the mucous membrane. These areas on the denture can be easily marked and material removed from the denture to reheve the premature or hard contact. 

The past two decades have seen remarkable advances in chiral chromatography, as only 20 years ago, the direct resolution of enantiomers by chromatography was still considered to be an impressive technical achievement. 

Supercritical fluid chromatography (SFC) provides a means of minimizing the limitations of CSPs developed for FC while retaining the impressive chiral selectivity that has been achieved through the evolution of CSPs during the past two decades [6, 7]. The use of supercritical fluids as eluents for chromatographic separations was... 

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