Dental cements Flashcards
(24 cards)
what is a cement
-a bonder which sets and hardens independently, binding materials together
Uses of cements
-cavity lining to protect pulp from direct restorations
-luting
-temp restorations
-endo
How do cements act as barrier materials
Thermal insulation: protect pulp from sudden change in temp from overlying filling material
Chemical: protecr from chems
Electrical: diff metal restorations placed adjacent to eachother may develop a galvanic cell causing pain
5 Requirements of cavity lining materials
-barrier (thermal, chem, electrical)
-flow- so can cover and move
-mechanical properties- withstand pressure of pushing down overlying material,
-radiopacity
-compatibility w overlying restorative material
Integrity of the cement depends on
degree of set
-thickness of material when set
-pressure exerted when placing the material eg amalgam
-the amount of surrounding tooth structure (thicker the better)
What are calcium hydroxide cements?
-two pastes (one 50% calcium hydroxide, 10% Zn0 and 40% ethyl toluene sulphonamide + butylene glycol disalicylate) mixed together
how do Caoh2 set, what happens when freshly mixed
-two pastes (one 50% calcium hydroxide, 10% Zn0 and 40% ethyl toluene sulphonamide + butylene glycol disalicylate) mixed together
-freshly mixed they have a high pH v alkaline to enhance formation of secondary dentine
-Setting rxn is chelation beween Zn0 and butylene glycol disalicylate
Uses and properties of CaOH cements
-pulp capping direct
-luting
-low compressive strength (though it increases over time)
MTA cements what is it, how do they set
-calcium silicate based materials
-made up of hydrophilic particles so when interact w water they set so no moisture control
MTA issues
-take long time to undergo setting
-poor handling
-can discolour oral tissues
MTA advantages
-can be grey or white up to u
-bioactive
- pulp capping
-seal well in root canals to reduce bacterial migration
Biodentine what is it
-calcium silicate material
Biodentine uses
pulp capping direct
-dentine replacement
-root performations
Biodentine advantages
-sets faster than mta bc of its larger particle size
-bioactive (ca released when in solution)
-biocompativle
Biodentine setting rxn
powder(of calcium silicates) + liquid phase(calcium chloride and water soluble polymer) -> paste which hardens to a cement
-sets 9-12mins
Ideal properties of luting cement
-ease of manipulation
-low film thickness (thin uniform layer bw teeth and restoration)
-long working time w rapid setting at mout temp
-low solubility in oral fluid
-adhesion to tooth
-biocompatible
-radiopaque
-anticariogenic properties
-good tensile and compressive strengths
e.g.s of luting cements
-zn phosphate
-znO eugenol
-gic
-resins
-zinc polycarboxylate
Zinc phosphate properties
-initial ph V low due to phosphpric acid but reaches neutral ph in 24h,
-exothermic so limits mixing time as it cools (5min), setting 15min,
-moisutre accelerates the rxn, rapid addition of power accelerated reaction
ZnO properties
-zinc oxide + h2o -> zn hydroxide
-zn hydroxide +eugenol <-> zinc eugenate
-the zinc eugenate is hydrolytically unstable so hydrolyses in presence of h2o and form zn hydroxide and eugenol again
-NEUTRALISATION RXN
neutral pH
bactericidal
ZnO uses
-used for liner, temp rest, sedative dressings
-good for temps, not perm bc they degrade over time in moisture
-CANT USE W COMPOSITE
-eugenol can act as free radical sink (if composite is ontop and prevents polymerisation of the composite)
EBA cement what is it, uses
-a modified ZOE cement
-sim setting rxn to ZOE
-lower solubility and higher strength than conventional ZOE
RCT what to use, ideal properties
bulk filler: malleable, dimensionally stable
-sealant:
insol in fluid,
low viscosity,
adequate setting time over hrs, retain seal over long time, bactericidal
biocompatible w bone
appropriate mechanical strength for crown.
Gutta percha advantageas
-plastic so reshape and remould
-biocompatible at root tip
-radiopaque
-can be removed and replaced if needed
gutta percha disadvanages
-lack of rigidity makes placing difficut
-ages rapidly n becomes brittle
-root canal prep is critical, must be confimed to prevent going out thru the apex
