Iso (1990) lists 3 types gypsum bonded of investments: Delayed hygroscopic expansion of gypsum products. If hygroscopic expansion has been.
gypsum
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12 several theories have been introduced to explain the mechanism for hygroscopic expansion.13, 14, 15, 16 nevertheless, the influence of water on set gypsum products used for cast articulation has not been investigated.
Bruce ady journal of dental research 1960 39 : An explanation for the hygroscopic setting expansion of dental gypsum products david b. Delayed setting and hygroscopic linear expansion of three gypsum products used for cast articulation. The type iii gypsum product demonstrated lower mean expansion values than type ii products.
At the beginning of mixing of the gypsum powder with water, there is a volumetric shrinkage 7;
Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Delayed setting and hygroscopic linear expansion of three gypsum products used for cast articulation. Several theories have been introduced to explain the mechanism for hygroscopic expansion. The analysing method for normal setting expansion proposed in previous studies was also applied to hygroscopic setting expansion under uniaxial stress and within an acrylic ring.
Stone casts are used in dentistry to allow the confection of indirect restorations.
In addition to the setting expansion, hygroscopic expansion is observed when the gypsum products are exposed to additional water while setting. The magnitude of the hygroscopic setting expansion which occurs with gypsum bonded investments is greater than that which occurs with gypsum model and die materials. An explanation for the hygroscopic setting expansion of dental gypsum products david b. An explanation for the hygroscopic setting expansion of dental gypsum products j dent res.
Over time, gypsite crystals are formed and an isotropic expansion can be observed 3,12, which continues up to 120 hours 4, although the specification n.
Bruce ady journal of dental research 2016 39 : The expansion of all gypsum products used for articulation purposes was complete at 96 hours. Philips science of dm (12th ed) and restorative dm b. Michalakis kx, stratos a, hirayama h, pissiotis al, touloumi f.
25 of ansi/ada 1 recommends the reading of the expansion for until 2 hours, the amount of time used in this study.
Time and material were more important factors than the dry/wet condition when. The final measurement should be taken at 120±1 min, counting from the beginning of the mixture of the original components. In addition to the setting expansion, hygroscopic expansion is observed when the gypsum products are exposed to additional water while setting. This contains setting expansion of gypsum in detail.
