Dental Materials: Miscellaneous pros materails Flashcards
What are the 2 presentations of an impression compound you can get?
5mm sheet
Green stick
What are the functions of the sheet and green stick in impressions?
sheet- edentulous ridges in stock tray
free end saddles for p/p before alginate impression
green stick- border extensions of impression trays
how do you condition green stick?
heat in flame
apply to trat
temper in water before use
what is the components in impression compounds?
thermoplastic material- resins/waxes
filler- talc
lubricant- stearic acid
How do you condition an impression compound?
55-65 degrees in napkin/ cloth lined water bath
can knead to incorporate water + plasticiser to improve flow
Why do you avoid prolonged immersion of an impression compound?
stearic acid will leach out
What are the 2 paste presentations of zinc oxide eugenol?
paste1: ZnO, Olive oil (inert, forms paste), Zn Acetate
paste 2: eugenol, kaolin/talc (inert filler)
What type of reaction does zinc oxide eugenol undergo?
setting
forms salt of zinc eugenolate + water
how do you use zinc oxide eugenol in an impression?
-close fitting tray w/ 1mm spacer
-usually added before using muscle trimmed border moulding with green stick
How is expansion in dental impression plaster reduced?
add potassium sulphate and borax
What does a pt complain of when dental impression material is removed?
dry mouth as it absorbs moisture
what are the ideal chemical properties of acrylic?
insoluble in oral fluids
no uptake of saliva/water
What are the ideal physical properties of acrylic?
radiopaque
high thermal conductivity
High Tg (32-70 degrees)
low specific gravity
dimensional stability
What are the ideal mechanical properties of acrylic?
high flexural strength, fatigue limit, impact strength and abrasion resistance
rigid
what are the ideal biological properties of acrylic?
non toxic, non irritant, no sustenance of bacterial/fungi growth
