Restorative and Laboratory Materials (Laboratory Materials and Techniques) Flashcards
What is the most commonly used impression material?
irreversible hydrocolloid, commonly called alginate.
What is the use of alginate impressions?
when less accuracy is needed, especially diagnostic tasks or models
What is the primary ingredient of alginate?
potassium alginate
What do you add to use alginate?
water which dissolves to form a viscous sol
and calcium sulfate forms a gel
What does a retarder do in alginate?
slows the setting
When alginate loses water due to heat, dryness, or air, it causes shrinkage, this is known as?
syneresis
When alginate gains water and swells, this is known as?
imbibition
What is gelatin time?
the time from which the alginate is mixed with water till the time it is set
What are the 2 types of alginate?
fast-set (1-2 mins) and regular-set (2 - 4 1/2 mins)
How can water be used in alginate impression?
high water temp, sets faster
How many scoops of alginate do you use for mandibular and/or maxillary impressions?
2 scoops: 2 water for mandibular
3 scoops: 3 water for maxillary
What is the main substitute for alginate?
silicone-based impression materials
The process of placing wax around the border of the impression tray is called?
beading
What is used to take an impression of the occlusal surface of a tooth?
wax bites or polysiloxane
What is agar-agar?
a reversible hydrocolloid
oldest impression material
good details
used for final impressions
What is a reversible hydrocolloid?
changes from a del to a sol and back again due to a thermal reaction
What are elastomeric impression materials?
rubber-like qualities for precise duplication
What is polymerization?
when the catalyst and accelerator begin to cure
What is a polysulfide impression?
mercaptan or rubber-base materials
comes in two pastes: base, catalyst
How can you identify the two pastes in a polysulfide impression?
larger and whiter is base
What impression material is used for crowns and bridges?
polyether
What is calcination?
when gypsum is heated, until a specific amount of water has driven ut
What is a Type I gypsum impression?
impression plaster
60ml to 100g
breaks easily
What is a Type II gypsum impression?
laboratory or model plaster
50ml to 100g
