Luting Agents Flashcards
what does the viscosity of a luting agent depend of
the size of the powder or filler particle in the material
what should the viscosity of a luting agent be
low to allow seating of the restoration without interference
why is it important for luting agents to be radiopaque
ceramic crowns are radiolucent which makes it easier to see marginal breakdown
what mechanical properties should a luting agent have
high compressive strength
high tensile strength
high hardness value
what are the two types of dental cement used for luting agents
zinc phosphate
zinc polycarboxylate
what are the two glass ionomer cements used for luting agents
conventional
resin modified
what reaction takes place in the zinc phosphate luting agents
acid-base reaction initially
then a hydration reaction
what is the powder aspect of zinc phosphate
zinc oxide
magnesium dioxide
alumina and silica
what is the liquid aspect of zinc phosphate
aqueous solution of phosphoric acid
what are some problems with zinc phosphate
low initial pH - pulpal irritation
exothermic setting reaction
not adhesive to tooth or restoration
what is the difference between zinc phosphate and zinc polycarboxylate cement
the phosphoric acid is replaced with polyacrylic acid
what is an advantage of zinc polycarboxylate cement
bonds to tooth surface in a similar way to glass ionomer cements
what are some problems with zinc polycarboxylate
difficult to mix
difficult to manipulate
soluble in oral environment at low pH
opaque
what is the reaction of glass ionomer cement
silica glass, aluminium oxide and calcium fluoride
what stages of reaction does glass ionomer go through
dissolution
gelation
hardening
how does glass ionomer bond to tooth surface
ion exchange with calcium in enamel and dentine
hydrogen bonding with the collagen in the dentine
what are some advantages of glass ionomer cements
low shrinkage
long term stability
aesthetically better than zinc phosphate
fluoride release
cheap
what is the reaction of resin modified glass ionomer
light activation causes polymerisation of the HEMA and copolymers in the material leading to initial rapid set
what does the secondary cure of RMGIC occur due to
a redox reaction
what does the secondary cure redox reaction allow for
dark curing - where the material is not exposed to light but will still cure
what does the incorporation of resin improve
shorter setting time
longer working time
higher compressive strength and tensile strength
higher bond strength to tooth
decreased solubility
what are disadvantages of RMGIC
HEMA is cytotoxic
HEMA swells - cannot be used with porcelain
no bond to indirect restoration
what must composite luting agents be used in conjunction with
suitable DBA
what is the trouble that occurs when trying to bond to porcelain
porcelain is brittle and its surface is smooth and unretentive so it needs a surface wetting agent
what surface wetting agent is used with porcelain
silane coupling agent
gamma-methacryoxypropyltrimothoxysilane
what end of the silane coupling agent reacts with the composite luting resin
C-C double bond end
what end of the silane coupling agent reacts with the composite luting resin
C-C double bond end
what end of the silane coupling agent reacts with the porcelain
the oxide group side
how can we bond luting agents to metal
the metal surface needs to be roughened by etching or sandblasting
how does etching a metal’s surface occur
electrolytes etching removes the different phases of the alloy at different rates
how would you bond to non-precious metal
4-META and MDP
acidic end of the molecule reacts with the metal oxide
when bonding to metal why must you use a dual curing material
light will not penetrate the metal
how do you bond to precious metal
the metal coupling agent is incorporated into the composite resin
what is Panavia
a composite resin with metal coupling agent which is an anaerobic self cured material
what indirect restoration can GIC be used to bond
MCC
metal posts
zirconia crowns
gold restorations
what indirect restorations can light cure composite and DBA used to bond
veneers
what indirect restorations can dual cure composite and DBA be used to bond
fibre post
composite inlay
porcelain inlays
what indirect restoration can anaerobic cure composite be used to bond
adhesive bridge
what are temporary cements
made to cement temporary restorations into place while permanent restoration is fabricated
how are the temporary cements supplied
2 pastes
what does the base of a temporary cement of
XnO, starch and mineral oil
what are the two main types of temporary luting agents
with eugenol
withou
when should eugenol containing cements not be used to cement the provisional restoration
when the permanent restoration will be cemented with a resin cement
why should you not cement a temp with a eugenol containing material when the permanent will be cemented with a resin cement
any residual eugenol may interfere with the setting of the luting agent
