DMS/ optech Flashcards
what impact does filler content have on composites handling characteristics
higher filled = dense
lower filled/ un filled = flowable
self cure vs light cure composites
self cure = 2 pastes (rare)
light cure - 1 paste , blue light activates camphorquinone
cavity base vs liner
base - thick , used to minimise amount of restorative required/ size of undercut
liner - thin coating to offer pulpal protection from chemical and thermal stimuli and microleakage
what products are used for cavity bases and liners
GIC/RMGIC used for both
Zinc oxide based cements - bases
setting calcium hydroxide - liners
setting calcium hydroxide
2 pastes that need mixed (chelation reaction) , GDH uses dycal
used for liners , small pulp caps
alkaline
ZOE products
zinc oxide eugenol
used as bases in deep cavities
shouldn’t be used under composites as can cause discolouration
non setting calcium hydroxide
one paste out a syringe , GDH uses ultracal
used for cleaning canals etc
what components make up composite resins
resin (soft) glass filler particles (hard) camphorquinone (photoinitiator) dimethacrylates (mechanical properties) silane coupling agent (allows intimate contact between filler and resin)
what monomer is commonly seen in the resin in composite
Bis GMA
what does a greater number of filler particles in composite resins result in
greater mechanical properties - increased strength, hardness, rigidity , abrasion resistance
lower thermal expansion and polymerisation contraction shrinkage
total etch vs self etch
total - removes smear layer , washed off
self - incorporates smear layer , not washed off
steps to composite bonding
total etch
- enamel - etch (phosphoric acid) roughens surface
- dentine - etch (phosphoric acid) removes smear layer and decalcifies outermost layer exposing dentinal tubules
prime and bond - primer = bifunctional , hydrophillic end bonds with dentine and hydrophobic end bonds with bond forming micromechanical bonds within tubules (molecular entanglement) creating the hybrid layer
subsequent composite resin applied then chemically bonds with the adhesive.
hybrid layer
resin material penetrating dentinal tubules
smear layer
layer of organic debris present on dentine after surface preparation
what must be done to conventional GIC after it has been placed
must be covered with a protective layer e.g varnich , resin , petroleum jelly
moisture contamination between the gelation and hardening phases allows aluminium ions to seep out resulting in a weaker material
