RPD LAB - CREATING SPECIAL TRAYS Flashcards
What does the tray need to do?
encapsulate all the anatomical features required for the construction of the prostheses on the definitive model
where is the tray outline positioned for impressions using alginate
2/3mm short of the vestibular sulcus depth
what does the wax spacer thickness relate to
the optimal thickness of the impression material you plan to use when taking the secondary impressions.
what is the procedure for the special trays
- draw outline with graphite pencil
- soak cast in cold water for 5 minutes
- split wax spacer so you have two 1.5mm bits
- heat modeling wax
- adapt wax to cast
- remove any folds with the knife
- cut modeling wax to outline
- apply second sheet of wax
- do same for lower
why do we leave the tray 2/3mm short of the vestibular sulcus
to allow the impression material to record the vestibular sulcus width and depth during the impression process
why does the tray extend to the soft palate
to ensure the junction between the hard and soft palate (vibrating line) is recorded in the definitive impression
why do we soak the cast in water
prevent wax adhering to it during the adaption phase
where do you start adapting first
palatal vault
then over tooth structures
then over vestibular sulcus depth
why should care be taken with second sheet of wax to ensure you do not trap any air between layers
place the second layer on top
why do we cut the lower wax in the lingual area
to avoid overthinking the wax during the adaption process
what are the dimensions of the tray handle
20mm long, 15mm wide, 8mm thick
what is the importance of the handle
extraoral guide to correct positioning
how should the handle be positioned
it should come at the mouth at 90 degrees and the handle should be horizontal and at the midline of the patient’s mouth. The underside of the handle should correspond with the incisial edge of the central incisors.
