Linings & Bases Flashcards
give some of the uses of dental cements
- temporary restorations
- cavity linings to protect pulp
- sedation/insulation of pulp
- cementing fixed prosthetics
give 1 ideal property of dental cements
non-irritant
explain the acid-base reaction of dental cements
many cements are acidic based and so an irritant to the pulp but on setting there is a rapid increase of pH –> not irritant anymore :)
describe the reaction with phosphoric acid based cements
vigorous reaction
between certain basic oxides and phosphoric acid
form phosphate salts of low solubility
exothermic
give 3 of the main phosphoric acid based cements
zinc phosphate, copper phosphate, silicophosphate
how are phosphoric acid based cements usually presented?
P:L
how is the setting time delayed and work time increased when using phosphoric acid based cements?
powder is introduced incrementally into liquid
initial set time for phosphoric acid based cements?
4-7 mins
give 2 examples of cements based on organometallic chelate compounds
zinc oxide eugenol cements
calcium hydroxide cements
how are zinc oxide eugenol cements typically presented?
P:L or as 2 pastes
how do zinc oxide eugenol cements set?
by chelation
how are calcium hydroxide cements typically presented?
suspension of CaOH in water
how do calcium hydroxide cements set?
VLC activation
once applied to the cavity base, what happens in the calcium hyrdoxide cement?
dries to give a layer CaOH
what are the 2 pastes of Calcium Hydroxide cements?
glycol sulphate and zinc oxide in CaOH
what are the 2 main groups of lining and luting cements?
polycarboxylate cements
glass polyalkanoate cements
how are polycarboxylate cements typically presented?
P:L
why are polycarboxylate cements not widely used for restorative linings?
difficult to handle as very rubbery
what are polycarboxylate cements widely used for?
as luting cements
Give a commercial name for a RMGIC used for restorative linings
vitrebond
what is the difference in composition between glass ionomer(polyalkanoate) for lining and luting compared to that for restorations?
the glass particles are smaller for lining and luting
why are the glass particles in GI smaller for lining and luting?
to allow the formation of a thinner film thickness for luting
how is GI for lining and luting typically presented?
P:L
is GI for lining and luting stronger than that of polycarboxylates?
yes
what must be done after lining and luting with GI and where does this become difficult?
varnish must be applied, difficult if the GI is subgingival
