Impressions & Impression Materials For Complete and Partial Dentures plus Occlusal Rim Lab Video Flashcards
which property is more important for preliminary impressions?
ADHESION -Increases surface area, increase adhesion
adhesion
attraction of DIFFERENT molecules to each other.
how do you increase adhesion?
by increasing surface area
increase surface area = increase adhesion
cohesion
attraction of the IDENTICAL molecules to each other.
how do you increase cohesion?
increase by increasing the CONTACT (closeness)
atmospheric pressure
the pressure exerted on the denture by the air around it VS the LACK of air inside the denture
pressure differential between the inside and the outside of the denture
the amount of SUCTION present as formed by the POSTERIOR PALATAL SEAL (POST DAM) and the peripheral borders
physical properties of Denture Retention
adhesion, cohesion, atmospheric pressure
what is the best preliminary impression material for a patient who gags easily? why?
impression compound - due to its flow properties and its quick set time
- compound has a 10-15 second set time and can be removed before it is completely set
why is it important to use a mucostatic impression material to record soft tissues accurately and passively?
- helps limit movement
2. reduced denture caused bone loss
saliva - mucosa attraction?
adhesion
saliva-denture attraction?
adhesion
saliva-saliva attraction
cohesion
clinical significance of atmospheric pressure border seal
the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances
- by using muco-dynamic border molding material
- creates the suction you need
great complete denture impressions are…
- muco-dynamic –> at the borders to create SUCTION
- muco-static–> everywhere else to LIMIT RESOPRTION AND INCREASE COHESION
- Covers as much surface area as possible to reduce movement and limite resorption and increase adhesion
muco-static will…
limit resorption and increase cohesion
muco-dynamic will…
definition?
create suction at the borders
selective displacing certain musculature and tissues of the oral cavity during an impression to force air out, changing the atmospheric pressure and creating suction
covering as much surface area as possible will…
reduce movement and limit resorption and increase adhesion
which impression material is too dynamic to accurately record soft tissues in edentulous impressions?
Alginate
what property (properties) does saliva contribute to and for denture retention?
- irrigation and lubrication of the mucous membrane
2. saliva enhances cohesion with enhances retention
retention is a function of?
- patient adaption
- polished surface contour
- atmospheric pressure
- adhesion
- cohesion
imbibition definition
a property of IRREVERSIBLE hydrocolloid (allginate) that refers to its tendency to absorb moisture from its surroundings and EXPAND
synersis definition
is the expulsion of a liquid from a gel - causing the alginate to dessicate - dry out
wraping alginate impressions prior to pouring?
paper towel - and it must be well rung out and damp -only
recommended impression material for a patient who has large embrasures / excessive undercuts?
Polysulfide Rubber – PSR
PVS has a much higher tear energy than PSR
adhesion and cohesion in denture
adhesion - >denture - Mucosa
Cohesion –> Denture - Saliva —Saliva - Mucosa
is the green stick compound used to make corrections to the preliminary impression (red cake compund) higher, lower, or same fusing temperature?
lower
what is the relationship between the mandibular wax rim to the anterior and posterior ridge crest lines?
CENTERED - the entire mandibular wax rim is centered to the mandibular ridge crest
facial surfaces of the maxillary central incisors are located?
6mm forward (in front of) the incisve papilla
when ask a patient to open their mandible wide and then close halfway and slide their mandible from side to side, what is the location of the denture being trimmed?
disto-buccal flange upper denture
the coronoid process of the mandible trimes for the width of the DB flange of the maxillary impression/denture border
what do you do in the DB area?
extend the post dam by continuing and tapering the scoring into the DB folds bilaterally to ensure a complete seal of the borders
where do you terminate the maxillary rim?
from tuberosity to tuberosity - on the anterior aspect of it
measurement on the occlusal surface anteriorly and posteriorly
anterior - 22mm measured from labial frenum to occlusal plan
posterior - parallel to the base of the casr
width of occlusal rim for maxillary
8mm - posterior in molar are
6mm wide in premolar area
4 mm wide in incisor area
width of maxillary rim is tapered how?
occlusally and incisally from the lingual aspext to better approximate the width of the teeth
posterior extension of the mandibular occlussal rim?
Just anterior to the retromolar pad
height of the mandibular occlusal rim?
anterior and posterior
Anterior= 18 mm high - from labial frenum to occlusal plane
posterior = 2/3 height of retromolar pad
what part of the mandible trims the width of the border of this denture impression being made?
coronoid process
what will tear easier, alginate or PVS?
alginate will tear easier than PVS
what material is most commonly used with a custom tray to form a mucodynamic impression of the folds and posterior palatal seal?
IMPRESSION COMPOUND (green stick)
alternative accepted answers: heavy bodied-PE, PVS. Silicone Putty
what material is too dynamic to accurately record soft tissue in endentulous impressions?
alginate
purpose of secondary cast
retention
space at palate is referred to as what?
space of dondore
where do we use muco-dynamic material?
BORDER MOLDING MATERIAL
at the borders - to create suction
compound or heavy bodied material
wash impression material
aka final coat? MUCO-STATIC thin coat of very light bodied impression material to get increasing detail - barely compresses the tissues - supported by the border molding
surface area covering in maxillary and mandible
maxillary - incisal papilla to hamular notches
mandible - all the way up retromolar pads
rigid materials and are they good for use with teeth?
Impression compound
ZOE Paste
Plaster of Paris
Not good for teeth and not good for undercuts
elastomeric materials
hydrocolloids
Polysulfide (rubber-base)
Silicones (PVS)
Polyether
Can work on teeth and good for undercuts
final impression material
PVS
time alginate should be poured up in?
8 minutes and decast in 20 minutes
impression material used for preliminary impression of edentulous arches?
compound
Zoe material?
Great static impression
- but hard when sets and pt intolerance
