engleski

Optical identification of inaccuracies caused by improper handling on type IV gypsum casts

Type IV gypsum (stone gypsum) is an essential material in prosthetic treatment. Improper handling can change hardness, expansion and compressive strength and it is the most common reason for inaccurate casts. In that case even the most perfect impressions will result in inadequate prosthetic treatment. Using optical instruments - digital camera (2, 5 million pixels) and digital microscope we tried to identify visual appearance of inadequate casts and relate it to specific causes. All casts were purred in highly controlled conditions, only one factor whose influence we tried to determine was changed during procedure. Most common mistakes are: outdated gypsum, wrong powder to water ratio, mixing without vacuum-mixer, purring without vibrator and etching by alginate acid. All that mistakes were visualised, easily recognized and categorized by using digital optical equipment. Visual key for identification of mistakes caused by improper handling is presented.

gypsum casts; mixing mistakes

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