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At least 1,135 records · Page 63Linked to original sources
PubMed1990

[Comparative material testing of dental impression and articulation plasters according to German Industrial Standard DIN 13911].

The purpose of the present investigation was a comparison of three special articulation plasters and three impression plasters. As DIN 13911 does not refer to articulation plasters, the inspection as well as the testing of pouring time, setting time, setting expansion and compressive strength using standard and manufacturer's consistence as carried out conforming to the guidelines for impression plasters. None of the tested plasters could meet the requirements of inspection in all points. Considering the physical parameters all plasters are up to standard, while Alpa quickstone and Arti-Plaster exhibited very low expansion and high compressive strength values. Although the compressive strength standard needs redefining, the value of a standardized testing technique for dental plasters is evident.

Calcium Sulfate↗
PubMed2005

A clinical evaluation of fixed partial denture impressions.

STATEMENT OF PROBLEM: Providing the dental laboratory with an accurate replication of the hard and soft tissue of a patient is important. Therefore, it is essential to examine whether clinicians critically evaluate impressions routinely before sending them to the laboratory. PURPOSE: This study evaluated the quality of impressions sent to commercial laboratories for the fabrication of fixed partial dentures (FPD) by describing the frequency of clinically detectable errors and by analyzing correlations between the various factors involved. MATERIAL AND METHODS: A total of 193 FPD impressions were evaluated, immediately after arrival at 11 dental laboratories, by 3 calibrated examiners. The impression technique and material used, tray type, and number of prepared units were recorded for each impression. Data relating to errors and faults, including defects in material polymerization, retention to tray, tissue contact by tray, crucial areas beyond tray borders, heavy-bodied material exposure through the wash material (for double-step impressions), inadequate union of materials, retraction cords embedded in impressions, and air bubbles, voids, or tears along the margin were also documented. The data were analyzed with the Pearson chi-square test (alpha = .05). RESULTS: Of the impressions, 89.1% had 1 or more observable errors. Significant correlations were found between material type and voids or tears at the finish line (Rv = 0.17, P < .025) and between material type and polymerization problems (Rv = 0.223, P < .004). CONCLUSIONS: Within the limitations of this study, impressions made with polyethers had the most detectable errors, followed by condensation-type silicones. The high frequency of detectable errors found in impressions sent for FPD fabrication is of concern.

Chi-Square Distribution↗
PubMed1991

Peel bond strengths of five impression material tray adhesives.

The peel bond strengths of five impression materials and their tray adhesives to a perforated and non-perforated test surface were measured and the results were compared using a one-way ANOVA and Student Newman Keuls Multiple Range Test at p less than or equal to .05 level of significance. The auto-mix addition reaction silicone material Extrude produced the greatest peel bond strengths on both the non-perforated test surface (10.88 kg/cm2), and on the perforated test surface (15.88 kg/cm2). These bond strengths were greater than those obtained from the polysulphide and polyether materials used in the study. Using the perforated test surface significantly increased the peel bond strength for all the materials tested. It was concluded that in order to achieve the maximum adhesive bond, impression trays should be perforated. The greatest peel bond strengths were obtained using Extrude medium-body impression material.

Analysis of Variance↗
PubMed1997

Adhesion of elastomeric impression materials to trays.

The tensile and shear adhesive bond strengths of two addition cured silicones (Provil and Express) and a polyether (Impregum) impression material to brass, poly(methylmethacrylate) and visible light-cured (VLC) tray resin were determined. Adhesive application significantly increased the bond strength; Provil and Express adhered most strongly to brass; whilst the Impregum-VLC combination produced the strongest bond. Indeed, VLC resin generated greater adhesion than acrylic resin. Exchanging the adhesives specified for each silicone material generally resulted in higher bond strengths. No correlation was established between speed of separation of the test surfaces and bond strength. For optimum clinical performance, the impression material (adhesive) tray material giving the highest bond strength should be utilized.

Acrylic Resins↗
PubMed1981

Identification of a foreign body using energy dispersive x-ray analysis.

A foreign object, presumably swallowed during a dental appointment, was recovered by using an esophagoscope and thought to be a piece of dental impression material, probably alginate. It was identified as being of nondental origin by means of visible light and scanning electron microscopy (SEM), the latter coupled to an energy dispersive X-ray analyzer. Histologic examination revealed some amorphous crystalline material surrounded by parakeratin and exfoliated squamous cells. The material was essentially radiolucent. A known dental alginate impression material contained diatomaceous earth filler (siliceous shells of diatoms), but no microscopic symmetrical figures were seen in the foreign body. After dehydration, both materials were carbon-coated and observed in an SEM at 20 kV at magnifications up to 2000 X. The spectrum of secondary X-rays produced by the scanning electron beam revealed only magnesium in the foreign body and mostly silicon in the dental alginate. There are no known dental products that contain magnesium as the only inorganic ingredient and so the foreign body is believed to be not of dental origin. The patient may have had an antacid or laxative having magnesium as a major ingredient in the stomach, and this may have been refluxed from the stomach after stimulation of the normal gag reflex during the dental procedure.

Dental Materials↗
PubMed1999

Survey of prosthodontic impression procedures for complete dentures in general dental practice in the United Kingdom.

STATEMENT OF PROBLEM: Anecdotal evidence suggests impression techniques used in general dental practice may vary from those taught at dental schools. There is little published information on this topic. PURPOSE: This study identifies the materials and methods used by general dental practitioners for recording impressions for the provision of replacement of complete dentures. METHODS: A total of 905 questionnaires were sent to general dental practitioners in the Greater Manchester area to identify current clinical practices. RESULTS: The results revealed that 88% of respondents use only irreversible hydrocolloid for primary impressions. If multiple responses are included, 99% of respondents mentioned irreversible hydrocolloids as an option for primary impressions. In response to the same question for secondary impressions, 94% of respondents mentioned irreversible hydrocolloids as an option. Other material mentioned as an option for secondary impressions included zinc oxide-eugenol (29%) and polyvinyl siloxane (13%). With regard to special trays, 75% of respondents routinely used laboratory constructed special trays to take definitive impressions. Questions on the requisite spacing, perforation, handle design of special trays, and on disinfection showed a diversity of opinion among practitioners. CONCLUSIONS: Although this survey reflected a diverse range of clinical preferences, it is clear that irreversible hydrocolloid dominates the impression market for complete dentures. The use of special trays is normal practice for complete dentures in general dental practice in the United Kingdom.

Acrylic Resins↗
PubMed1998

Impression materials.

This paper incorporates a brief review of impression materials currently available for use by the orthodontic profession; subjective assessments of a selection of alginates, silicones and bite registration materials in a clinical setting; and a list of prices and retailers of impression materials.

Alginates↗