Creating Gypsum Products
Case A: You need to make a custom try for an appointment in progress and have just taken the alginate impressions. How would you accelerate the setting time of the gypsum product you selected?
To accelerate the setting time of the gypsum product I selected, first I will try to use a “fast set” gypsum if it is available at the office, since it has accelerators placed into the gypsum and lower the setting time. If this is not an option at the office because there is only “regular set”, I would use a longer and more rapid spatulation of gypsum, increase the temperature of the mixing water, and will add the particles of set gypsum by scraping the surface of an old study model (I prefer this rather than using the slurry water recommended in the
text book). I will not decrease the amount of water because the mixture might be too thick and might end up with voids.
Case C: Several air voids are present on the surfaces of the teeth. What factors may have caused this?
Several air voids present on the surfaces of the teeth might be as a result of decreasing the amount of water (w/p ratio), which make the mixture more difficult to work, since is very thick and will be harder to make sure the mixture runs through the cusp spaces. Also, the operator took a long time to finish pouring the impression and the mixture could have being setting already, or used warm water and the setting time was accelerate and did not have enough time to properly pour the impression.
To accelerate the setting time of the gypsum product I selected, first I will try to use a “fast set” gypsum if it is available at the office, since it has accelerators placed into the gypsum and lower the setting time. If this is not an option at the office because there is only “regular set”, I would use a longer and more rapid spatulation of gypsum, increase the temperature of the mixing water, and will add the particles of set gypsum by scraping the surface of an old study model (I prefer this rather than using the slurry water recommended in the
text book). I will not decrease the amount of water because the mixture might be too thick and might end up with voids.
Case C: Several air voids are present on the surfaces of the teeth. What factors may have caused this?
Several air voids present on the surfaces of the teeth might be as a result of decreasing the amount of water (w/p ratio), which make the mixture more difficult to work, since is very thick and will be harder to make sure the mixture runs through the cusp spaces. Also, the operator took a long time to finish pouring the impression and the mixture could have being setting already, or used warm water and the setting time was accelerate and did not have enough time to properly pour the impression.