dental luting agents Flashcards
3 luting agent type examples
dental cement
composite resin
GIC
give 5 good properties of a luting agent
low viscosity
radiopacity - to see marginal breakdown
marginal seal - ideal if bonds to tooth
biocompatible - non toxic, no heat on set
easy to use
ideal film thickness
as thin as possible - 25 microns or less
how can a luting agent be cariostatic
antibacterial
fluoride releasing
4 ideal mechanical properties of dental luting agent
high compressive strength
YM similar to tooth
high hardness
high tensile strength
two examples of dental cement
zinc phosphate
zinc polycarboxylate
what reactions take place when mixing the powder and liquid of zinc phosphate
initial acid base reaction
phosphoric acid and zinc oxide
followed by hydration reaction to produce crystallised phosphate matrix (hopiete)
benefits of zinc phosphate
cheap
easy to use
what component of zinc phosphate gives white colour
magnesium dioxide
what acid is used for zinc phosphate cement
50% phosphoric acid
function of aluminium oxide in zinc phosphate cement
prevents crystallisation leading to amorphous glassy matrix of acid salt surrounding unreacted ZnO
3 negatives of zinc phosphate cement
low initial pH - plural irritation
not adhesive to tooth
not cariostatic
what is the difference between zinc phosphate and zinc polycarboxylate
phosphoric acid is replaced by poly acrylic acid
3 advantages of zinc polycarboxylate
bonds to tooth
cheap
low pH but returns neutral more quickly than zinc phosphate
3 disadvantages of zinc polycarboxylate
difficult to mix
soluble in low pH
lower compressive strength than zinc
what is the difference between GI luting cement and GI filling material
particle size of glass - cement is less than 29 micrometers to allow suitable film thickeness
what type of reaction takes place in GI cement
acid base between acid and glass
acid - poly acid mixture of acrylic acid, maleic acid
glass - silicon dioxide and aluminium oxide
how does GI cement bond to tooth
ion exchange with Ca in enamel and dentine
H bonding with collagen in dentine
how does GI bond to the restoration
mechanical - sandblast restoration to allow mechanical adhesion
no chemical bond
3 advantageous properties of GI cement
low shrinkage
self adhesive to tooth substance
fluoride release
what does RMGIC contain that conventional GI does not
hydrophilic monomer HEMA
hydroxyethyl methacrylate
how is HEMA polymerised in RMGIC
light activation
incorporating resin into GIC to make RMGIC improves what properties
setting time is shorter
higher compressive and tensile strength
higher bond strength to tooth
disadvantage of RMGIC
HEMA is cytotoxic - uncured monomer will damage pulp
no bond to indirect restoration
HEMA expands so shouldn’t be used to cement porcelain (crack) or posts (split root)
in dual cured composite, how much are physical properties reduced by in comparison to light cured
25%
benefits of composite luting agent
better physical properties
better aesthetics
lower solubility
between light cure and dual cure, which luting agent is suitable for an inlay
dual - light won’t penetrate through the inlay
how does composite luting agent bond to an indirect composite inlay
micro mechanical to rough internal surface of inlay
C=C bonds on fitting surface of inlay
how do you bond porcelain to composite resin luting agent
hydro fluoric acid
surface wetting agent is required as not hydrophobic - silane coupling agent
give an example of silane coupling agent
gamma-methacryoxypropyltrimethoxysilane
how does silane coupling agent bond porcelain to composite luting agent
strong bond between oxide groups on the porcelain and silane
C=C bond on silane reacts with composite resin luting agent
How are filler particles bonded to the resin matrix in composite resin filling materials
oxide groups on filler particles bond with the silane
carbon to carbon double bond in silane reacts with the resin
How are filler particles bonded to the resin matrix in composite resin filling materials
oxide groups on filler particles bond with the silane
C=C double bond in silane reacts with the resin
for tooth to be bonded to porcelain, what materials are needed in-between
tooth
DBA
composite luting agent
silane
porcelain
for a thin porcelain restoration, what composite luting agent should you use
light cure
how can you roughen a metal to bond to composite
sandblasting
etch - cannot etch precious metals
for tooth to be bonded to non precious metal, what materials are needed in-between
tooth
DBA
composite luting resin
metal bond agent
non precious metal
what bonding agent is used when bonding non-precious metal to the luting agent
MDP
or
4-META
how do MDP and 4-META bond to non metal and to luting agent
they have an acidic end of molecule which reacts with metal oxide
C=C reacts with composite resin luting agent
2 examples of materials with carboxylic and phosphoric acid derived resin monomers
MDP
4-META
what composite luting agent would you use when bonding to metal
dual cure as light will not penetrate metal
what is a self adhesive composite resin
metal coupling agent is incorporated into composite resin
e.g. panavia has MDP
cheat code
if unsure of what luting agent say dual cure composite with DBA as this does everything
how would you bond a precious metal
need to change the alloy composition - incorporate copper and heat to get oxide formation
can tin plate it
what is present in temporary cements that stop it setting fully
carnauba wax - weakens structure
what are the two types of temporary cement
eugenol
non-eugenol
when should eugenol temporary cement material not be used and why
when composite resin luting agent will be used to cement the definitive restoration as remaining eugenol will interfere with set
