enamel and dentine bonding agent Flashcards
what is bonding?
the process of attaching two materials together.
why do we use a bonding agent?
prevent Microleakage
prevent Recurrent caries
prevent Marginal staining
what are the main ingredients of bonding agents
Methacrylate resin
Gluteraldehyde – desensitiser
Acetone – has an attraction to moist surfaces, allows resin to penetrate water on dentine or in dentinal tubules.
makes up 60% of agent forces resin into etch pattern
Water
Photoinitiators i.e camphorquinone and stabilisers (starts polymerisation of the resins when the blue light is applied)
what is in the resin primer of the bond?
HEMA – Hydroxy Ethyl Methacrylate Resinin a solvent -acetone
High viscosity, purely a resin creates the HYDROPHILIC LAYER – more water tolerating monomers
what is in the bond? - creates the resin over the primer
Bis–GMA or TEGDMA
Bis-GMA- Bisphenenol-A-glycidyl Dimethacrylate
TEGMA – Triethylene glycol Dimethacrylate
Results in a Hydrophilic & Hydrophobic Layer which creates a Hybrid Layer
what are properties of bonding agent?
immediate, permanent, high strength bond
Minimise microleakage
Prevent recurrent caries and staining
Shelf life
Compatible with dental tissues
Lack of sensitisation
what is the hybrid layer consisted of?
The layer of resin + collagen fibrils is
the hybrid layer.
why do you only lightly dry after rinsing the etch off? before applying bond
collagen fibrils can collapse and occlude the dentinal tubules
what does etching prime and bonding do?
etch removes the smear layer removes some hydroxyapatite crystals
prime- causes collagen rehydration allows sticking to occur
bond- produces the hybrid layer and tags into dentine
what does light curing create?
resin tags- Locks the restoration by micromechanical retention
wetting helps spread the bond evenly what can poor wetting cause?
causes beading of the
liquid e.g. water on a waxed car
