Bases, Linings And Temporary Materials Flashcards
What is a base in a cavity preparation
A material which is placed on the floor of the cavity preparation in a thick layer
Thermal insulation
Absorbing occlusal forces
What is a liner
A material placed in a thin layer over exposed dentine
Dentinal sealing
Stimulation to formation of irregular secondary (tertiary) dentine
What is a varnish
They seal dentinal tubules to reduce microleakage which may cause sensitivity, discolouration and bacterial invasion
What is calcium hydroxide Ca(OH)2
A dental liner which stimulates the formation of tertiary dentine
For direct or indirect pulp capping
What are 2 advantages of calcium hydroxide Ca(OH)2
Easily manipulated
Stimulates the formation of tertiary dentine
What are 2 disadvantages of calcium hydroxide Ca(OH)2
Moisture sensitive
Low strength
What is zinc oxide eugenol used for
When the decay is very deep or very close to the pulp chamber
What are 4 advantages of zinc oxide eugenol
Good dimensional stability
Good surface detail reproduction
Inexpensive
Adheres week to dental compound
What is a disadvantage of zinc oxide eugenol
Soft tissue irritant
What are 3 advantages of zinc oxyphosphate
Easy to manipulate
Economic
The excess material is removed easily
What are 3 disadvantages of zinc oxyphosphate
Not aesthetic
They account for the largest cases of micro filtration
Speed with the preparation of the mixture
What is an advantage of zinc polycarboxylate
Presents chemical adhesion to the dental structure
What are 3 disadvantages of zinc polycarboxylate
Work time is much shorter
pH of the liquid is 1.7 which is neutralised by the powder
The cement does not bond with noble metals when the model or vacuum is contaminated
What are 3 examples of temporary materials which will last 3-4 days
Zinc oxide eugenol
Zinc oxyphosphate
Zinc polycarboxylate
What are 3 examples of temporary materials which last 6 months
GICs
RMGICs
Compomers
What are 2 key features of GICs
They can bond to enamel and dentine
They release fluoride from the glass component of the cement
What are GICs composed of
Glass
Polyacid
Water
Tartaric acid
What are the 3 main components of GIC glasses
Silica
Alumina
Calcium fluoride
Why is the glass composition limited to the central region of the phase diagram for GICs
To maintain translucency
What does tartaric acid do
Affects the working and setting times of GICs
What are the 3 stages of the GIC setting process
Dissolution
Gelation
Hardening
What happens during dissolution of GICs
The solution or water mixed with powder causes the acid to dissolve and react with the outer glass layer leaving a silica gel
When does final translucency and colour become apparent after GIC placement
24 hours
How long does it take for a GIC to fully physically and mechanically set
1 month later
What happens during gelation of GICs
Initial GIC is set due to calcium ions reacting with acid carboxyl groups
What happens during the hardening phase
Aluminium ions after 30 mins provide final strength via strong cross linking
Water binds to silica gel around glass particles
Glass particles in silica gel within the cross linked polyacrylic acid matrix
What are resin modified GICs (RMGICs)
Are hybrid glass ionomers primarily functioning as glass ionomer cements with a small amount of added resin typically hydroxyethylmethacrylate (HEMA)
What are 4 disadvantages of GICs
Low early strength
Susceptibility to erosion
Slow setting phase
Risk of desiccation
What are 6 advantages of RMGICs
Command set by visible light
Between wear resistance
Lower solubility
Early high compressive and flexural strength
Good polishability
Ability to retain polish
