L2-Impression and Impression Materials + Trays and Retention Flashcards
Goal of impression
depends on…
- type of impression depends on..
- purpose of impression depends on…
- type of prostheis
what will tear easier… alginate or PVS?
alginate
Primary cast - purpose?
Support and Surface Area
DIAGNOSTIC
capture the SA and see what support we can get
T/F you can fabricate a denture on a primary cast
FALSE
Secondary cast - purpose?
RETENTION
can see more defined rugae and more accuracy here
make sure to have right type of trey and material
RETENTION is a function of what? (five)
- patient adaption
- polished surface contour
- atmospheric pressure
- adhesion
- cohesion
adhesion and how to increase it
attraction of DIFFERENT molecules to each other - and increases by increasing SURFACE AREA
cohesion and how to increase it
attraction of the IDENTICAL molecules to each other - increase by increasing CONTACT (closeness)
atmospheric pressure
the pressure exerted on the denture by the air around it vs the LACK OF AIR inside the denture
is adhesion enough for denture retention?
NO - need the addition of cohesion
clinical significance of saliva-mucosa and attraction type?
adhesion
saliva-denture attraction is an example of?
adhesion
saliva-saliva attraction is an example of?
Cohesion attraction
what contributes to the suction formed by posterior palatal seal?
atmospheric pressure and by using mucodynamic capture of the folds by the final impression
atmospheric border seal - clinical significance
the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances
wash impression material?
VERY light bodied - barely signals on tissue and barely compresses the tissue so we can see detail of rugae and any other detail on the surface
this is a very low viscocity material
Muco-dynamic where? wht?
at the borders to create SUCTION
Muco-static where? why?
everywhere else
to limit resorption and increase cohesion
why cover as much surface area as possible?
to reduce movement and limit resorption and increase adhesion
muco-dynamic definition
selective displacing certain musculature and tissues of the oral cavity during an impression to force out air, changing the atmospheric pressure and create suction
muco-static definition
an impression taken without displacing any tissue - the mucosal tissues of the jaws as they are in a state of rest..
how do we (steps) for making impressions for edentulous?
- preliminary and final
- border molding and final impressions
- selective impressioning -
impression compound, ZOE paste and plaster are rigid or elastomeric?
rigid — NOT GOOD FOR UNDERCUTS
hydrocolloids, Polysulfide (rubber-base), silicones (PVS) and polyether are rigid or elastomeric?
elastomeric - GOOD FOR UNDERCUTS
impression compound is reversible or irreversible?
reversible
impression compound used when?
for preliminary impressions - also alginate
characteristics of compound impressions?
mucodynamic more stable than alginate better extension into vestibule folds can be removed before set (gagger) can bead and box inelastic cost-low
alginate is mucostatic for?
hard tissues
alginate is muco-dynamic for?
soft tissue - heavy body
can you bead and box alginate?
no- may deform under wight of stone if unsupported
trays for preliminary impressions?
Must use edentulous trays if patient is edentulous because dentate stock trays will hold excessive alginate
“Best” tray fit mindset?
may not be perfect - so adjust when need to with periphary wax
use periphary wax in areas that need more coverage or added material like to cover the RMP area or hamular notches
general characteristics of final impressions
they are BOTH mucostatic and mucodynamic (so mucoselective)
general final (2) impressions objective
Mucostatic detail (closeness= cohesion)
Diagnose denture
Mucodynamic (at the borders - and includes PPS)
two types of material (general) that are required for final impressions
list the examples
Dynamic - at border
using compound and PVS - heavy bodied
Static (recording the interior tissues)
using light body polysulfide (rubber base)
PVS - Light and extra-light viscosity
ZOE (zinc oxide and eugoenol)
Polyvinyl Siloxanes
Excellent surface details
;ight body PVS and XLV
static impression material - recording excellent tissue detail w/o compressing tissues
characteristics of ZOE
most mucostatic
but are very sensative to moisture
are inelastic/rigid
irreversible but relinable
there are patient sensativity issues
also contraindicated if patient has exccess saliva or xerostomatic
rubber base impressions are mucostatic if?
if they are light bodied
tear energy between PVS and Rubber base?
PVS has MUCH HIGHER tear energy
when is PVS contraindicated?
when patient has undercuts and large embrasures
heavy body where?
borders - mucodynamic
medium body where?
interior
light or XL where?
intaglio - interior tissues - mucostatic detail
impressions increase adhesion by?
cohesion by?
Adhesion by increasing surface area
cohesion by increasing closeness
primary imperssion obkectives
patient diagnosis tissue outline preliminary casr tray fabrication adhesion
secondary / final impression objectives
- denture diagnosis
- tissue detail
- final cast
- denture fabrication
cohesion
a well made custom tray?
- Fits closely to allow use of static impression materials
- relieved with wax depending on impression material used
- can be adapted at the borders to produce a dynamic seal (compound, PVS heavy)
- results from a great preliminary impression
need tissue spacer when using PVS?
yes- PVS needs body in order to capture details without breaking apart
custom trey is made from?
preliminary impression
what do you use to make final impression (not material)
custom treys
potential problomatic areas?
Anterior and Posterior undercuts
where should you block out?
in the undercuts - we can increase closeness which will increase cohesion
Effect on anterior blockout for anterior of tray
- maintains tissue contact
- maintains lip position
- maintains border seal
important the tray goes with path of insertion and maintains contact everywhere
what do you do if anterior undercuts exist?
alter the path of insertion
if undercut - will need to position the tray up and back not just in and up
what do you do if there are posterior undercts?
- alter the path
2. block out EVENLY
corrective procedure for undercut in anterior only?
eliminate or decrease with TAIL DOWN TILT
corrective procedure for undercut in posterior only?
eliminate or decrease with NOSE DOWN TILT IF NO ANTERIOR UNDERCUTS–anterior undercuts could increase with this if they exist OR block out evenly in posterior
corrective procedure for undercut in anterior and posterior?
- eliminate or decrease anterior undercut 1st with TAIL DOWN TILT, then block out posterior undercuts evenly
so use the anterior as the new path and block out the posterior undercuts
if patient has anterior and posterior undercuts will blocking out anterior work?
it could increase the posterior undercuts by doing tail down tilt (if dont block out posterior) and just change path of insertion
adapt denture where and block out where?
adapt in anterior - to avoid too much thickness and blockout in the posterior
posterior blockout compromises what?
loss of cohesion but not loss of esthetics
tail down tilt
eliminates the anterior undercut
nose down tilt
eliminates posterior undercut
fabricating trey in SLC vs clinical?
clinical – all the way then cut 3mm from full depth of fold (with width remaining at 3mm) for clinical patient
SLC - went to the full depth and width of fold for SLC dentoform
spacer and tissue stops for PVS? for PSR?
PVS - yes
PSR- no
