impression Flashcards
what is an impression?
negative imprint of the oral structure to produce positive replica
what is a study model?
a positive life size production of the teeth and adjacent tissues
what are study models used for?
study of oral condition
treatment planning
what impression should be taken first?
mandibular
what materials are required?
trays fix wax alginate disinfectant lab bag lab card
What is alginate material?
irreversible hydrocolloid
carboxylated polysaccharide based on alginic gels
cross linking with calcium ions
what are the components of alginate?
sodium alginate calcium phosphate sodium phosphate zinc barbonate ph indicators
what component is the retarder?
sodium phosphate
what component is the filler?
zinc carbonate
what is ideal gelation time?
3-4 minutes
what is ideal spatulation time?
1 minute
what is working time?
30 seconds
How should tray size be selected?
length to cover retro molar area of mandible and tuberosity of maxilla
clear most protruding incisor
from where should the mandibular impression be taken?
from the front of patient
seat with rotary motion
ask patient to lift tongue
from where should the maxillary impression be taken?
from behind the patient
seat posterior first
