Linear setting expansion of different gypsum products

Resumo

Stone casts are used in dentistry to allow the confection
of indirect restorations. Thus, gypsum dimensional stability is
fundamental in order to achieve a precise fit between dental structure
and restorative material. Objective: The purpose of the present study
was to evaluate the hygroscopic linear expansion of commercially
available gypsum products. Material and methods: Fifteen dental
stones were analyzed (4 type II, 5 type III, 4 type IV and 2 type
V), with n = 5. One hundred grams of each gypsum product were
mixed following the respective manufacturers’ recommendations for
powder/water ratio and poured into a V-shape mold, connected to an
expansion-measuring device. The hygroscopic expansion was evaluated
during 120 min and the collected data was converted into percentage
and compared to initial dimensions of the specimen. Results: All
type II and V dental stones showed expansion values compatible
to the ADA and ISO recommendations. Considering type III stones,
only Rutenium 3 was compatible with the recommendations. For
type IV, only Durone IV showed expansion values higher than that
recommended by ADA, but lower than that of ISO recommendations.
Conclusion: The hygroscopic linear expansion of gypsum products
should be periodically controlled in order to ensure their precision
and reliability to dental practice.