negative
impressions are a ____ reproduction of dental structures
preliminary impressions
used for making: diagnostic models, custom trays, provisional coverage, orthodontic appliances, for pretreatment and post treatment records
bite registrations
show the patient's centric relationship between the maxillary and mandibular arches
rigid
impression trays must be sufficiently ____ to carry the impression material into the oral cavity, hold the material in close proximity to the teeth, avoid breaking during removal, prevent warping of the completed impression
quadrant tray
covers one half of the arch
section tray
covers the anterior portion of the arch
full arch tray
covers the entire arch
perforated tray
has holes in the tray to create a mechanical lock to hold the material in place
smooth tray
interior of the tray is painted or sprayed with an adhesive to hold the impression material
VPS adhesives (blue)
for polyvinvyl siloxane and polyether impression materials
rubber base adhesive (brown)
used with rubber base impression materials
silicone adhesive (orange-pink)
used with silicone impression materials
blue
VPS adhesives
brown
rubber base adhesive
orange-pink
silicone adhesive
hydrocolloid impression mateirals
used to obtain preliminary and final impressions
hydro
water
colloid
gelatin substance
irreversible hydrocolloid
material CANNOT return to a solid state after it becomes a gel (alginate)
makeup of alginate
potassium alginate, calcium sulfate, trisodium phosphate, diatomaceous earth, zinc oxide, potassium titanium fluoride
potassium alginate
comes from seaweed
calcium sulfate
reacts with the potassium alginate to form the gel
trisodium phosphate
added to slow down the reaction time for mixing
diatomaceous earth
a filler that adds bulk to the material
zinc oxide
adds bulk to the material
potassium titanium fluoride
added so as not to interfere with the setting and surface strength
physical phases of alginate
1. sol
2. gel
first phase-sol
the material is in a liquid or semiliquid form
second phase-gel
the material is semisolid, similar to a gelatin dessert
how long is shelf life for alginate
approx 1 year
imbibition
alginate impression stored in water or very wet paper towel--will absorb the additional water and expand
syneresis
alginate impression remains in the open air, moisture will evaporate causing it to shrink and distort
alginate settings
normal, fast set, working time, setting time
normal set alignate
working time of 2 mins and a setting time of 4.5 mins after mixing
fast set alginate
working time of 1.25 mins and setting time of 1-2 mins
working time
the time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient's mouth
setting time
the time required for the chemical action to be completed
cooler water
increase the setting time
warmer water
reduce or shorten the setting time
mandibular impression ratio
2 scoops of powder, 2 measures of water
maxillary impression ratio
3 scoops of powder, 3 measures of water
acceptable alginate impression
impression tray centered, complete peripheral roll (including all of the vestibular areas), tray is not overseated, impression is free from tears or voids, sharp anatomic detail of all teeth and soft tissues, hard palate and tuberosities are recorded in t
reversible hydrocolloid
impression material that changes its physical state from a sol to a gel and then back to a sol
reversible hydrocolloid ratio
85% water 13% agar
conditioning bath for reversible hydrocolloid
1. conditioner bath
2. storage bath
3. tempering bath--keeps material at 110F in syringe and tray
types of reversible hydrocolloid
1. tray material
2. syringe material
tray material
each tube has enough material to fill a full arch
syringe material
fit in a syringe or preloaded syringe or preformed sticks
application of reversible hydrocolloid impression material
1. a stock water-cooled tray
2. plastic stops are placed in the tray
3. tubing is connected to the tray and to the water outlet for drainage
4. the material is liquefied and moved to the storage bath
5. light-bodied material is placed in the syringe, and
elastomeric impression materials
extreme accurate impression
characteristics of elastomeric impression materials
1. base
2. catalyst
catalyst
accelerator
elastomeric materials
light-bodied (syringe type/wash type), regular/heavy-bodied (tray type)
light-bodied
syringe type/wash type
regular/heavy-bodied
tray type
basic impression technique
1. The material selected depends upon the dentist's preference and the type of impression required for the procedure.
2. The dentist prepares the tooth or teeth for the impression.
3. The light-bodied material is prepared and loaded into the syringe and t
curing stages of elastomeric materials
1. initial set
2. final set
3. final cure (1-24 hrs)
types of elastomeric materials
polysulfide
polyether
silicone
polyvinyl siloxane
polyvinyl siloxane impression material
base: silicone polymers
catalyst: chloroplatinic acid
filler: silica
polyvinyl siloxane
best impression material, pouring of the model can be delayed 7-10 days
wax bite
useful when the diagnostic casts are trimmed
dental models
3D reproductions of the teeth and the surrounding soft tissue
study models
gypsum
mineral that is mined from the earth
model plaster/plaster of Paris (white)
used primarily for pouring preliminary impressions and the making of diagnostic models
dental stone (yellow)
use as a working model when a more durable diagnostic cast is required (custom trays, ortho appliances)
high-strength stone/densite (green/pink)
strength and hardness, create dies used in the production of crowns, bridges, and indirect restorations
model plaster ratio
100g to 45-50ml water
dental stone ratio
100g to 30-32ml water
high-strength stone ratio
100g to 19-24ml water
anatomic portion
created from the alginate impression
art portion
forms the base of the model
double-pour method
anatomical portion is poured first, second mix of plaster or stone is used to prepare the art portion
box-and-pour method
impression is surrounded with a "box" made of wax and poured as one unit
inverted-pour method
consists of mixing one large mixture of plaster or stone and pouring both portions of the model in a single step
preparing model for trimming
soak in water for 5 mins
finishing the model
mix the slurry of gypsum, and fill in any voids
finishing a plaster model
soak the model in a soapy solution for 24 hours, dry, and then polish with a soft cloth
custom tray
self-curing acrylic resin
vacuum-formed thermoplastic resin
impression tray, making of provisional, vital bleaching tray, mouth guard
boxing wax
used to form a wall or box around a preliminary impression when pouring it up
utility wax
1. extends the borders of an impression tray
2. cover brackets in ortho treatment
sticky wax
repairing a denture--used on lingual side
ASA I
healthy patient w/o systemic disease
ASA II
client with mild systemic disease or extreme anxiety
ASA III
client with severe systemic disease that limits activity but is not incapacitating
ASA IV
client with incapacitating systemic disease that is a constant threat to life