ABSTRACT Objective: To evaluate the dimensional change of edentulous models made high density laboratory silicones at different storagetimes. Methods: A metallic master model simulating an maxilla was used. The had projections 1.8 cm located in regions canines (A and B) molars (C D) allowing linear measurement distances AB, BC, CD, DA, AC BD. silicone mold for duplication following materials (n...

The accurate duplicate cast obtained from a single impression reduces the profession clinical time, patient inconvenience, and extra material cost. The stainless steel working cast model assembly consisting of two abutments and one pontic area was fabricated. Two sets of six each custom aluminum trays were fabricated, with five mm spacer and two mm spacer. The impression methods evaluated durin...

Background Gypsum, or calcium sulfate dihydrate, (CaSO4 l 2H2O) is the major component of drywall, or gypsum board, core. It is a naturally occurring mineral, deposited largely as a result of the evaporation of water in ancient inland seas, which contained large amounts of dissolved gypsum. For example, the evaporation of a typical 20,000 gallon residential swimming pool filled with seawater wi...

The rate of hydration influences many important physical properties of gypsum. Previous research examined the rate of gypsum hydration and related this to compressive strength and microstructure development using BET specific surface area analysis. The analysis of gypsum porosity in combination with BET surface area and rate of hydration remains to be done. In the present study, mesoporosity is...

Background and Aim: Bacterial colonization occurs following contamination of impression materials with blood and saliva. However, not all disinfecting agents are compatible with the impression materials and may cause changes in the resultant casts. The purpose of this study was to assess the impact of various immersion time of addi-tion silicon impressions in different disinfecting solutions on...

This paper reviews the main methodologies and techniques that have been used to characterize gypsum in soils, especially in gypsiferous soils of semiarid and arid regions and range from the identification of gypsum in soil surveys in the field to the study of gypsum in the laboratory. Many methods of gypsum identification and determination have been developed, each one with its own limitations....

Gypsum is hydrated calcium sulfate (CaSO 4 • 2H 2 O), and is often marketed as a soil " conditioner " for improving soil " tilth. " Compared to most other calcium-rich soil amendments, such as limestone, gypsum is relatively soluble in water, dissolving up to 2 g per liter. The solu-bility of gypsum, when either incorporated or surface applied, permits a quick release of calcium (Ca 2+) and sul...

BACKGROUND The study aimed to evaluating the effect of disinfecting impression materials on the dimensional accuracy and surface quality of the resulting casts. METHODS Impressions of a steel die constructed according to ANSI/ADA specification No.18 were made with each of alginate, addition cured silicone, condensation cured silicone and zinc oxide eugenol paste, and disinfected consequently ...

In order to determine the feasibility of manufacturing wood-gypsum and wood-gypsum-cement particleboards, the hydration reactions of four Eastern Canadian wood species with gypsum and Portland cement were studied. The compatibility of hot water extracted and raw wood particles with both gypsum and a gypsum-Portland cement mixture were determined for jack pine, balsam fi r, aspen and white birch...