Primary Impressions and Primary registration Flashcards
what are the steps to primary impression taking
ppe
tray selection and try in
select an impression material
take the impression
decontamination
laboratory card
why do you need primary casts
denture design, eg saddles, looking at occlusions and undercuts
make primary models in the lab, construction of special trays or primary bite blocks
describe the tray section for primary impressions
variety of shapes, sizes and colours
perforated trays are preferred
plastic disposable dentate and edentulous trays are available
tips for the tray handles
hold the flat side of the handle, hold tray in front of you as you would seat it in a patients mouth
fitting surface facing the teeth
fit of the width of the tray is critical, length and depth can be modified
add ribbon wax or a green stick, remove overextensions with an acrylic bur on straight handpieces
why would you use an impression compound
to capture the free end saddle areas before taking an impression in alginate, stabilises the stray to reduce rocking and support the alginate
what can be used if there are free end saddle areas in an impressoin
record the free end saddle areas using a compound, then apply alginate adhesive to the tray and the compound
what criteria should an impression meet
records tendentious areas
records sulcus of the denture border area
records teeth and has good detail of occlusal surfaces and occlusion
enables the lab to make a good special tray
how to decontaminate the impression
rinse and place in perform for 10 minutes
indicate that impressions have been decontaminated on the lab card
bag with wet cotton wool or a paper towel and take it to the lab as soon as possible
what are index teeth
multiple upper and lower teeth will contact when the patient occludes. the teeth that contact each time are called index teeth
when would you not need a primary registration
if when hand articulating, the casts can be held together and meet the same way each time, and there are enough index teeth present
what is a wax wafer
placing warm wax into the patients mouth and have them bite together to confirm the occlusion, this is an inter occlusal record.
if a cast cannot be hand articulated, what does this indicate
you will need primary record blocks, which are an upper shellac base plate and a lower wire strengthener
the casts are then mounted on articulator after registration is provided to the lab
how to record primary registration
bring blocks to required occlusal level, add bite registration paste and ask the patient to occlude. check the index teeth are still in contact
what can happen if there is too much bite registration paste used, not enough wax removed from the block or bite registration paste set before the patient occludes
there will be increased occlusal vertical dimension
inadequate freeway space
what should be done before taking the master impressions
design the denture and identify any teeth that may require modification, eg rest seats and guide planes
