Composite material Flashcards
Resin modified GIs, GI
hydrophobic (water based)
self-adhesive
no adhesive required
Compomers, Composite resin
hydrophobic (resin based)
Not self adhesive - requires adhesive
Dental composite matrix phase
continuous phase
- monomer resin
- initiators
dental composite dispersed phase
discontinuous phase
- glass fillers
- colorants
Monomer functional groups
monomethacrylates
dimethacrylates
monomethacrylates
linear chains - soft - can melt easily
dimethacrylates
branched and crosslinked - rigid, don’t melt easily.
Composite monomers
difunctional methacrylates
form highly crosslinked rigid networks
Monomers in composite
potentially estrogenic - tegma, BIS-GMA, TEGDMA
Silicate glasses influence
strengthen (rule of mixtures, more filler = more strength) Optical properties (color, translucency) Radiopacity
Filler surface
glass has hydrophilic surface
- silica tetrahedrons
- surface hydroxyl groups
- attract water molecules
- inhibits wetting of surface with monomers (hydrophobic)
Silane coupling agent
silane coupler - gets hyrophilic glass into composite
- improve composite properties
- adheres filler to resin phase
- primer
- MPS
Abrasive
non-contact wear - foods abrade polymer
Attrition
occlusal contact wear - higher stresses, lead to polymer microfracture
Improved wear from
smaller, softer particles
Crystalline (original) filler
quartz - radiolucent, very hard and abrasive
Non-crystaline (glasses)
modified to improve characteristics
-softer, additives to make glass radiopaque, more crushable, need to have it wear with resin**
GI
acid base rxn
Composites
free radical rxn
Dentin as substrate
initial preps likely to encounter tubular dentin
Smear layer inhibits good adhesion
ground bits of HA, collagen, bacteria, salivary proteins Inhibits resin penetration into dentin
Etchant
inorganic acid - 35% Phosphoric acid
completely remove smear layer and plugs
demineralizes surface dentin
leaves a collagen rich surface with numerous pores
Primer
primarily hydrophilic monomers - water, alcohol, acetone barrier
Adhesive
hydrophilic/hydrophobic mix
Hybrid layer
interdiffusion zone - resin and collagen
interpenetration zone
Curing lights
halogen
plasma arc lights
argon lasers
LED (the norm)
LEDs
peak output ideal for CQ. Power intensity similar to highest QTH but lower than laser and xenon arc
LED curing units
small, compact and light weight battery powered and cordless long bulb life power output narrow (negative) Tip design limited (negative)
Curing composite
degree of conversion - % double bonds converted, usually 65%
Depth of cure - 1mm = 65%, 2mm = 45%, 3mm to 4 mm = 15%.
Light intensity is proportional to the
distance squared.
Acute angle symbol
starts low ends high
sun symbol
high output light - faster overall.
