Glass Polyalkenoates Flashcards
4 properties of Ion Leachable glass
Adhesive
Better appearance
Less solubility
Better mechanical properties
What acid is in polycarboxylate cements?
Polycarboxylic acid
When did the peak of GI development happen?
1970’s
What forms can GI come in?
Powder : Liquid
Powder : Water
Encapsulated
What powder is used in the P:L state?
Sodium aluminosilicate Glass with 20% CaF
What powder is used in the P:W state?
Sodium aluminosilicate Glass with 20% CaF PLUS vacuum dried POLYACID
What liquid is used in the P:L state?
Aqueous solution of acrylic acid copolymer PLUS Tartaric acid
What does Tartaric acid do?
Controls the settting
What mixing technique should be used with a scoop and drop bottle?
Oscillatory
What is the porosity in viscous cements compared to fluid cements?
There is lower porosity with viscous cements
Fluid cement is split into hand mixed and mechanically mixed: Mechanically mixed results in more porosity.
Which has the highest setting time out of Restorative/Luting/Lining
Luting is 2.5-8 compared to 2-6.
Which has the highest compressive strength out of Restorative/Luting/Lining?
Restorative with 130 compared to 70
Why should you not leave the liquid in the fridge?
It is difficult to mix by hand as it initiates the acid crystallisation
How is GI bonded to the tooth?
By Calcium ions
To collagen by H bonding and metallic ion bridging
What acid increases the bond strength?
Polyacrylic
Describe Enhanced bond strength
You can only bond to the limit of the tensile strength of GI cement- if it is any greater then COHESIVE CEMENT FAILURE will occur.
Give 7 properties of GI
Thermal diffusivity close to dentine Brittle (15-20 MPa) Chemical set is exothermic (2-5º) Fluoride release and uptake Poor abrasion resistance Lack in radiopacity It is susceptible to acid erosion
What is a cermet?
Heat resistant material
What properties does a cermet have?
Increase compressive strength
poor appearance
What is the filler replaced by in Modified composite?
Aluminosillicate Glass which encourages fluoride release
How is Modified composite set?
Set by Light cured free radicals polymerisation
When does the acid base reaction occur in Modified composite?
Late on as- Water enters when the resin is set and the acidic groups in the resin are ionised. This is the acid base reaction.
What is the composition of a Giomer?
The same as Modified composite BUT- Aluminosilicate is pre-reacted with polyacid to form a GLASS POLYALKENOATE COMPLEX
What are the 2 types of Giomer reaction?
Surface and Full
