Glass Ionomer Cement 2 Flashcards
What are the 2 mechanisms which GIC bind to the tooth tissue?
- polyacrylic acid displaces surface phosphate and calcium an enters the hydroxyapatite structure and forming a calcium polyacrylate salt
- Intermediate layer of calcium and aluminium phosphates and polyacrylates are formed at the tooth/restoration interface
What is the bond strength like?
low, but good enough
Can the bond reform if broken?
YES, there is evidence
it is considered dynamic
Why can the material and tooth tissue rebond?
due to the polyacrylate and calcium ions being in close proximity to each other
What can improve the reliability of the bond?
preconditioning surface of the tooth by an acid conditioner
What is an example of an acid conditioner?
citric and polyacrylic acids
What does the acid conditioner do to the tooth?
primarily removes the smear layer and debris form the surface of the tooth
Between polyacrylic acid and citric acid, what one is favoured for acid conditioning?
polyacrylic acid
it is not so highly mineralised
Is the ability of GIC to seal good or bad?
pretty good - get little leakage
Does GIC dimensionally change?
little or no change
Is the bond between restoration and tooth stressed or unstressed?
unstressed
When are fluoride ion released form the glass?
during setting reaction
Where do the fluoride ions sit in the material?
within the matrix and free to migrate
What does the rate of release of fluoride ions depend on?
When are the most fluoride ions relased?
during maturation phase and slows and follow a normal diffusion pattern
How long are fluoride ions released from GIC?
YEARS
When can GIC take up fluoride ions?
if the eternal concentration is higher than that in the surface
How can you ‘recharge’ the GIC?
FLUORIDE TOOTHPASTE OR GEL
When does the GIC release the fluoride ions?
When the external fluoride conc drops aka fluoride sink
What can fluoride ion release prevent?
inhibit bacterial growth and plaque build up
When does rapid wear occur of GIC?
first 10 days then slows
What can happen to the GIC before maturation?
washout by saliva
Why does wear occur of GIC?
due to loss of glass particles from the matrix particularly in load-bearing areas
Can low ph erode GIC?
YES, if maintained for long periods of time
What are the advantages of GIC?
What are the disadvantages of GIC?
When would you use GIC?
Atraumatic restorative technique (ART)
deciduous teeth
Tunnel preparations
class III
class V (especially non-carious tooth loss)
inter-visit endodontic access cavity restorations (especially with respect to resin composite)
long-term intermediate restoration
as a base layer or liner
dressings
fissure sealants
luting of crown and bridge retainers / orthodontic cements
What cavities would you use GIC?
Class III and class V (especially non-carious tooth decay)
What is luting?
a technique used to secure indirect dental restorations e.gf. crowns, bridges etc
What should have a higher viscosity GIC, luting or restoration?
direct restoration - increased mechanical properties
What is the downside to having a higher viscous GIC?
less liquid, so less acid, not going to get as good a bond
When would you not use GIC?
Where high load is anticipated - class I or II)
large posterior cavities
cores where little or no tooth is remaining to support the material
where aesthetics are a primary concern
Do you want a round or sharp cavity prep?
round - no sharp edges
Do you need extensive retentive features in the cavity?
no need
How does GIC appear after thoroughly drying?
whiter than tooth tissue
What is the aim of conditioning the tooth?
clearing out the smear layer and cleaning the surface as well
What do you use to condition the tooth?
a 25% solution of polyacrylic acid
How long do you condition the tooth for?
15-30 seconds
Do you cure of rinse off the conditioning solution?
wash off and gently dry
What are the 2 methods to mix the GIC materials together?
- by hand
- encapsulation
When would you mix GIC by hand?
to vary the materials consistency to suit application e.g. non-ideal crown
What decreases when you increase the powder ratio of GIC?
The ability to form chemical bonds decreases (the cement must adequality wet the tooth surface)
rapid decline in mechanical properties also result because solid particles of glass are not wetted sufficiently by the acid to start setting reaction
setting time
What increases when you increase the powder ratio?
compressive strength
What is the scoop to drop ratio?
2:2
What type of spatula is used?
agate
What is the most common glass ionomer lute cement on the market?
aquaCem
What has a higher powder to liquid ratio; hand or encapsulated?
in general the powder: liquid ratio of encapsulated materials is less than the recommended powder to liquid ratio for their hand mixed counterparts
What is used when placing GIC for a class V?
cervical matrices
For a class V restoration using GIC, when do you remove the tweezers from the surface of the cement?
until material has fully set
How long do you wait before finishing?
at least 3 minutes
some up to 6 minutes
How do you cause the least damage during finishing?
under fine water spray
don’t use petroleum jelly
How long is water protection essential for?
at least an hour
How do you protect the outer surface of the restoration from water?
- petroleum jelly
- copalite varnish
- fuji varnish (GC)
- RESINS
