Please explain the setting reaction of gypsum products. what is setting time?!
Question: Please explain the setting reaction of gypsum products!. what is setting time!?
is there any website with dental animations for 1st year students like me!?Www@Answer-Health@Com
Answers:
Urgh, dental materials science!. I don't know of any good websites sorry, I'm just here to offer my sympathies!.
I used Applied Dental Material (McCabe and Walls) to study from, it has all the info you need!. I picked it up quite cheaply from a charity bookshop near the university, you might be able to do the same :)
The setting times of gypsum products vary between types - for type 1 (dental impression plaster) there is no initial set, and the setting time is 4 mins!. For type 2 (model plaster) the initial setting time is 5-10 mins and the setting time is 20 mins!. For types 3-5 (all types of dental stone foe die casts) the initial setting time is 5-20 min, and the setting time is 20 mins!.
Initial setting time refers to "the time at which the material develops the properties of a weak solid and will not flow readily!.!.!. it is possible to carve away excess material with a knife"!. Setting time refers to the period of time before "the stage where the models or dies are strong or hard enough to be worked upon" - although the ultimate strength of the material may not be reached til a few hours later!.
The reaction is:
Calcium Sulphate Hemihydrate + Water ---> Calcium Sulphate Dihydrate
Specifically:
(CaSO4)2!.H2O + 3H2O -----> 2CaSO4!.2H2OWww@Answer-Health@Com
I used Applied Dental Material (McCabe and Walls) to study from, it has all the info you need!. I picked it up quite cheaply from a charity bookshop near the university, you might be able to do the same :)
The setting times of gypsum products vary between types - for type 1 (dental impression plaster) there is no initial set, and the setting time is 4 mins!. For type 2 (model plaster) the initial setting time is 5-10 mins and the setting time is 20 mins!. For types 3-5 (all types of dental stone foe die casts) the initial setting time is 5-20 min, and the setting time is 20 mins!.
Initial setting time refers to "the time at which the material develops the properties of a weak solid and will not flow readily!.!.!. it is possible to carve away excess material with a knife"!. Setting time refers to the period of time before "the stage where the models or dies are strong or hard enough to be worked upon" - although the ultimate strength of the material may not be reached til a few hours later!.
The reaction is:
Calcium Sulphate Hemihydrate + Water ---> Calcium Sulphate Dihydrate
Specifically:
(CaSO4)2!.H2O + 3H2O -----> 2CaSO4!.2H2OWww@Answer-Health@Com