cavity bases and liners Flashcards
what are intermediate restorative materisals
materials applied to dentine to protect the pulp prior to placing the main restorative material
types of itermediate restorative materials
varnish
cavity liner
cavity base
varnihs
thin polymer seal to the dentine surface
cavity liner
layer of protective dentine sealer less than 0.5mm thick
cavity bas
dentine replacement intend to eliminate undercuts or minimise bulk of main restorative materail
thicker than 0.5mm
clinical need of IRMs
dental pulp chamber sensitive
may need additional protection for the pulp when placing direct restorative material
prevents heat or chemical diffusion to pilp
what might adversely affect the pulp
physical stimuli e.g. temp or mechanical forces
chemical stimuli e.g. acids
which may relate to
caries, microbial ingress or contamination
n
n
an ideal cavity base or liner properties
1) safe and biocompatible
2) form effective dentine seal against chemicals, bacteria and other stimuli
3) may encourage dentine generation in pulp chamber (reparative dentine, 2 or 3)
4) chemically and mechanically compatible with other restorative materials
5) tooth coloured, radiopaque and easy to place
dental materials used as IRMs
1) Varnishes (polymer solution in solvent)
2) calcium hydroxide cemenets (dycal)*
3) MTA (biotentine)*
4) Zinc oxide cements commonly zinc oxide-eugenol or ZOE
5) Glass ionomer cements
6) Resin modified glass ionomer cements
7) visible light cured resins
* used where pulp exposed
cavity varnishes material and how it works
natural or synthetic polymer resins dissolved in solvent and applied to cavity floor with brush of cotton
solvent evaporates to leave a thin layer of resin
acts as a barrier against chemical penetration of tooth tissue and may protect against micro leakage and secondary caries
calcium hydroxide cements
rigid self setting material
presented as two pastes for mixing
two paste material used in calcium hydroxide cements
1) calcium hydroxide, zinc oxide
2) salicylate ester, titanium oxide, calcium sulphate
chemical reaction forms zinc and calcium dislylate and other compounds
properties of calcium hydroxide
- Alkaline nature due to free Ca(OH)2 may promote tertiary dentine formation (due to slight irritation) and provide antibacterial properties (may help heal cavity)
- low compressive strength but sufficient to withstand condensation of amalgam
- initial pH greater than 11, alkalinity associated with local tissue irritation that later mineralise (reparative dentine once dentine like in appearance)
- may be used as a protective base or liner under primary restorative, acts primarily as a pulp camp
- slowly soluble in water
what is the leading brand of CaOH cement in Uk
dycal
radiopaque and ivory colour
how is zinc oxide eugenol formed
acid base reaction between a metal oxide and eugenol (forms metal eugenolate chelate)
what zinc oxide eugenol used for most commonly
tempoarary restoration
can be used for base/liner
why is zinc oxide eugenol unpopular
due to risk of pulpal necrosis and inhibition of composite rein polymerisation( stops setting reaction)
why should zinc oxide eugenol not be used with compostie
due to inhibition of composite resin polymerisation
what is IRM
zinc oxide eugenol material
what is IRM designed fro
to remain in place for 12 montths
uses underneath a non resin restoraion
glass ionomer cements properties
- Relatively robust (compressive strength >50 Mpa)
- adhesive
- insoluble
- insulating
- fluoride releasing
- aesthetic (can be used as a direct restorative material)
what is glass ionomer cements composed of
basic fluoaluminsilicate glass
polymermic acid
water
tartaric acid
how is GIC formed
mixing via acid base reaction
- metal cations form salt bridges with ionised carboxylate acid groups on high molecular weight polyacids
Why is GIC popular
predictable adhesive bond
good marginal seal
Resin modified glass ionomer cement vs GIC
similar but addition of
HEMA- water miscible monomer
photoinitiator
how does resin modified GIC set
acid base reaction and photo polymerisation (HEMA polymerises)
shares GIC chemical bond to untreated dentine
future trend materiasl
mineral trioxide aggreagate
diodentine
mineral trioxide aggregate
can be used for pulp capping, base or liner
sets slowly
good at stimulating reparative dentien
diodentine
calcium silicate
sets in one hour
sealing dentine leads to
reduced microleakage
less post op sensitivity with reduced risk of plural inflammation
thermal insulation
less sensitivity to hot or cold
mechanical protection
resistant to packing or elimination of undercuts
better supported restoration and further pupla protection
what is a key driver of the use of dycal i.e. CaOH
stimuli of reparative dentine
what is the best protection for pulp tissues
healthy dentine
