Luting agents
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What are the components of composite?
Camphorquinone Glass/ quartz filler particles Dimethacrylates Silane coupling agent Resin - bisGMA allows free radical addition polymerisation
Describe how etch, DBA and composite bonding works?
When you cut a cavity there is formation of the SMEAR LAYER - debris. Etch 37% removes the smear layer and opens up the dentinal tubules, to allow for sufficient penetration of the composite resin. Dentine bonding agent- surface wetting agent. Facilitates bonding of the wet/ inorganic dentine to the dry/ composite via the hydrophilic (bonds to dentine) and hydrophobic (bonds to composite) ends of the DBA molecule Composite resin can then penetrate into the dentinal tubules forming the HYBRID LAYER - comp. bonds via chemical AND micromechanical retention
What is the standard test applied to composite resin?
ISO4049
What are some uses of GI?
Fissure sealants for pre-cooperative children Temporary restoration material Luting agent Buccal/ cervical filling material anterior lesion where sufficient moisture control cannot be achieved for composite placement
Advantages of RMGI over GI?
Longer working time - set on demand as light-cure Increased mechanical strength due to presence of resin particles Lower solubility
Disadvantage of RMGI over GI?
Contains some free monomer - may not be as bio-compatible
What type of cement is panavia and what would you use it for and why?
Dual-cure, self-etch composite resin luting agent that is fluoride-releasing Used for - adhesive resin-retained ridges, MCC Contains 10-MDP - facilitates bonding to metal
How is an emax crown/ onlay prepped and what cement is used for bonding?
Prepped in the lab with 10% hydrofluoric acid Requires etch and bond and silane coupling agent Dual-cure composite e.g. NX3/ nexus
What type of cement is Aquacem and what would you use it for?
GIC luting cement - offers mechanical bonding rather than chemical Used for permanent cementation of MCC and conventional bridges
Give an example of a cement you would use for cementing a provisional protemp restoration?
Temp-bond - ZOE cement
What type of cement is nexus/ NX3 and what would you use it for?
Dual-cure composite resin Porcelain inlay/ onlay, fibre-post, veneer, composite inlay
How must metal restorations be prepared in the lab?
They must be sandblasted
What are the functions of acid etch?
Removal of smear layer to unblock dentinal tubules Increases surface roughness - creates microscopic spaces within enamel - for micromechanical adhesion De-mineralises dentine surface, exposing collagen network
Explain how porcelain metal fused alloys are stronger than all ceramic/ all porcelain?
Porcelain is brittle and is prone to microcracks which leads to failure Alloys are ductile and can withstand large forces
What luting agent would you use to cement a metal post and core?
GIC
What cement for veneer?
Light-cure resin cement with DBA and silane coupling agent OR Dual-cure composite for thicker veneers
What cement for a fibre-post?
Dual-cure composite & DBA
What cement for MCC?
GIC
What cement for Zirconia crown?
GIC
What type of restorations can you cement with a dual-cure composite cement?
Fibre post Composite inlay/ onlay Porcelain inlay