Trays, Materials and Techniques Flashcards
(47 cards)
What are impression trays?
A device used to
carry, confine, and control
impression material
while making an impression
What are the various types of impression trays
stock (denate and endentulous)
water cooled
custom
tripple
Describe custom trays?
Maintains optimal thickness of impression materials, 2.0 to 4.0 mm for elastomers
Require less impression material
Provide proper flange extensions
How should trays extend distally?
Trays should extend distally to cover the maxillary tuberosity and cover the mandibular retromolar pad for maximum anatomical reproduction
What height should trays be?
Tray height should fully cover the length of anterior and posterior teeth
How should trays extend regarding the facial aspect?
Tray should extend beyond the facial aspect of the teeth with ¼ inch of space between the tray and soft tissue
Utility wax beading
Wax may be added to the borders of the tray to extend its length or height
Wax can be placed in the palatal area of patients with high palates to eliminate voids in the palatal area
Wax may be placed around the tray periphery to protect and cushion the soft tissues in the oral cavity
The placement of utility wax on the posterior region of the maxillary tray prevents excessive alginate from flowing down the throat
What are the different types of impression materials?
Alginate Hydrocolloids
Agar Hydrocolloids
Elastomeric Impression Materials
Imbibition
to take in water
Syneresis
to give up water (dry out)
Tensile strength
ability to withstand tearing
Working time(WT)
time before the material begins to set; starts from the time you began mixing & includes the time you have to load material into a tray or syringe
Setting time(ST)
time it takes for the material to be completely set (from start to finish)
Mixing time
time you have to mix the material
Alginate is classified as an?
irreversible hydrocolloid
Why is alginate classified as a hydrocolloid?
Hydrocolloid because it is particles of a gelatinous (colloid) state in water (hydro).
What is alginate particles composed of?
Salts of alginic acid, a product of marine kelp (a type of seaweed)
An activator, usually calcium sulfate
A retarder like sodium phosphate
An inert filler to reduce stickiness, produce a smooth texture, and add strength
Flavoring
What are disadvantages of alginate?
Poor tear strength when thin
Poor dimensional stability
Distorts if shifted during setting
What are advantages of alginate?
Easy to mix and manipulate
No expensive equipment needed
Elastic and removes from undercuts easily
Cost effective
Pleasant taste and odor
What is type 1 Fast set alginate?
WT 1 minute
ST 1-2 minutes
What is type 2 normal set alginate?
WT 1-2 minutes
ST 2-4 minutes
What temperature should water be for aliginate?
73
How should impressions be removed?
with a snap-out motion
Describe agar in agar hydrocolloids
13-17% for tray material and 6-8% for syringe materi
