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
how does conventional GIC and RMGIC bond to tooth
can bond to both enamel and dentine without need for bonding agent
bond occurs via carboxyl groups in GIC acid and CA ions from hydroxyapatite
some manufacturers recommend a conditioner (polyacrylic acid) prior to placement
how does amalgam bond to tooth
doesnt bond
is mechanically retained via cavity preparations incorporating undercuts
what are the two components that make up conventoional glass ionomer cements
acid(liquid) - polyacrylic
base (powder) - aluminium , silica and calcium fluoride
3 phases of conventional glass ionomer cement setting
Dissolution - dissolving of the glass powder in acid
Gelation - initial setting, Ca ions bind with carboxyl groups
Hardening - final setting , Al ions further cross link
dual vs tri curing RMGIC
dual - acid base reaction like conventional + light activation
tri - acid base, light and redox
setting reaction of amalgam
AgSn3 + Hg - AgSn3 + Ag2Hg3 + Sn7Hg9
AgSn3 = gamma phase = strongest
vitapex
paste consisting of calcium hydroxide and iodoform used in endodontics
what are probes used for
depends on type
straight dental probe - caries detection point focus , retraction etc
BPE probe - BPE
PCP12 probe - periodontal pocket charting
what are excavators used for
caries excavation , amterial removal
what are flat plastics used for
manipulation of shapeable filling materials
why do we use water with ultrasonic scaling
water acts as a coolant , high vibrations can cause friction that may lead to pulpal damage via heat transfer
what makes up RMGIC
liquid - polyacrylic acid, tartaric acid , HEMA (monomer), photoinitiator
powder - aluminium , silica, calcium fluoride
