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PubMedDate not supplied

The effect of custom tray material type and adhesive drying time on the tensile bond strength of an impression material/adhesive system.

The purpose of this investigation was to compare the tensile bond strength of one poly(vinyl siloxane) impression material/adhesive system to three different custom tray materials 10 minutes, 48 hours, and 7 days after adhesive application. One autopolymerizing (Fastray) and two light-polymerizing (Triad and Extoral) custom tray resins were examined. The Triad tray resin exhibited the significantly highest mean adhesive tensile bond strengths, and the Fastray resin exhibited the lowest. It was also observed that the 48-hour adhesive drying time group exhibited the highest mean adhesive tensile bond strengths for all the materials tested, and the 10-minute group exhibited the lowest.

Acrylic Resins↗
PubMed1989

[Distortion of working models using different silicone impression techniques].

The influences of differing strains levels of impression materials in compression and impression techniques on the distortion of working models were examined. The working models, which differed in the size of cervical spillway (2mm and 9mm) and the impression techniques applied (the two-phase technique and the wash technique), were produced by using putty-type impression materials with three different strain levels (Reprosil, Express and Exaflex) following the metal master model of mandibular denture in an abutment form. Distortion of the working models was then measured by a three-dimensional measuring system. The results were as follows. 1) The models produced through the impression technique using hard impression materials with low strain levels displayed decreases both in the degree of inclination to the X axis of the abutment tooth variations distance between the left and right abutment teeth. This procedure was found to yield a model which was proximate to the master model. 2) The impression technique incorporating a small cervical spillway resulted in decreases in variations in the distance between the right and left abutment teeth and the diameter of the molar part of the abutment tooth, and the horizontal distortion of the alveolar ridge; the model thus produced was found to be proximate to the master model. 3) Application of the two-phase technique reduced variations in height of the abutment tooth, and the use of the wash technique led to decreased variations in the distance between the right and left abutment teeth and diameter of the molar cervix of the abutment tooth. 4) Differences in strain levels of putty-type impression materials, the size of cervical spillway and the impression technique used did not influence deviation of the model toward the Y axis (vertical direction). 5) The models with least distortion of the abutment tooth were obtained by the two-phase technique using hard impression materials with lower strain levels or by the wash technique using soft materials with higher strain levels.

Dental Impression Materials↗
PubMedDate not supplied

[Profilometric research on silicone impression materials].

The data suggest that none of the materials produced in the USSR or imported, did fully reproduce the microrelief of the surface of metal standard. This is accounted for by the processes taking shape on the surfaces of elastomeric compositions upon their vulcanization.

Chemical Phenomena↗
PubMed2001

[The reliability of class A alginate impressions].

The class A alginates present very good properties of dimensional precision and reproduction of details, comparable to those of the reversible hydrocolloïdes and certain elastomeres used for the realization of secondary prints of precision in fixed prosthesis and in removable prosthesis. Besides, their application is easier and they are costless. The valorization of these print materials could certainly contribute to reduce the cost of comes back of prostheses in countries under developed where the weak power economic populations constitute a brake to the access to cares of health. To exploit qualities of these print biomaterials well, it agrees to manage correctly the parameters of their application. To this effect, the present survey puts in evidence that the maximum delay of stream that guarantees the good dimensional stability of these class A alginates is of 45 minutes in the hot and humid climatic tropical country conditions.

Alginates↗
PubMedDate not supplied

Improved marginal seating of cast restorations using a silicone disclosing medium.

This study was conducted to determine the effectiveness of a silicone disclosing medium, G-C Fit-Checker, as an aid in the improvement of marginal integrity. Standardized preparations were made on 42 freshly extracted premolars. Base metal alloy castings were finished externally and initially adjusted internally. The castings were placed on their respective teeth and the marginal opening was determined. They were then adjusted twice using the silicone material and remeasured. The preadjustment mean marginal opening was 92 microns and the postadjustment measurement 55 microns, yielding a mean reduction of 37 microns (SEM 3 microns) or 39%.

Bicuspid↗
PubMed1999

Procedure to prevent cast breakage during separation from elastomeric impressions.

This article describes a quick and simple procedure for removing dental stone casts from elastomeric impressions. Frequently, dental stone casts break at the time of separation because of the rigidity of the impression material. The materials used in this technique are inexpensive and easy to use. When this method is properly used, it simplifies the removal of the cast from the impression, decreasing the chance of fracture of the cast.

Dental Impression Materials↗
PubMed2002

Effect of mixing method on rheological properties of alginate impression materials.

The apparent viscosity of alginate impression paste prepared by three mixing methods (hand-mixing technique (HM), semiautomatic instrument (SM) and automatic mixing instrument (AM)), and the gel strength and surface depression of the respective set materials were measured. The materials used were eight commercially available products mixed at a temperature of 23 +/- 0.5 degrees C and allowed to set. The AM had a high mixing speed, which reduced the working time 4.4-31.5%, compared with HM. This was the result of an increase in paste temperature during mixing. In the case of impression materials mixed with the AM, the gel strength and the surface depression at the gel fracture increased significantly, in accordance with Fisher's protected least significant difference (PLSD) analysis. This phenomenon is caused by a decrease of air bubbles in the set material.

Air↗
PubMed1978

An emergency hydrocolloid unit.

Except for the inconvenience of liquifying the material in some other place, the described setup is almost as convenient as a regular hydrocolloid unit. The chief disadvantage is that the small tanks will hold only about three regular tubes of material at a time.

Colloids↗
PubMed1977

The impression tray--an important factor in impression precision.

The flow behaviour of impression materials during impression taking was first investigated, and reference made to the pressure which occurs in the compound. Individual trays of plastic and shellac-bases which could be softened by heating, and a cold-curing tray material were then also examined: (1) for their distortion by slight loads upon the tray walls; (2) for their ability to retain their shape when stored, and (3) their distortion when temporarily warmed to body temperature. It was found that no tray materials, although graded according to type and thickness, can be considered rigid under experimental conditions, since distortions which were in some cases considerable could be measured. In laboratory experiments, the behaviour of the tray was then measured while taking impressions of models and the precision of the impression was examined at the same time. This confirmed the suspicion that the precision of an impression is to a considerable extent related to the tray material used. The smallest alterations were found when using cold-curing plastic material of a sufficient thickness (greater than 2 mm).

Dental Impression Materials↗
PubMed1990

Reversible agar agar hydrocolloid.

Reversible agar agar hydrocolloid remains an excellent, cost-effective impression material. A review of the history of the development of the material and a sound technique for its use are presented.

Agar↗