Exam 3: Resin Composites Flashcards
procedure of composite restorations
- caries removed and etched with acid
- adhesive is applied
- resin placed in increments or in bulk
- resin cured
main component of resin composites
dimethacrylate monomer
dimethacrylate provides…
polymerization mechanism and thus setting mechanism
a solid that contains two or more distinct constituent materials at the
microlevel
composite
4 essential components of composite materiasl
- organic polymer matrix
- inorganic filler particles
- coupling agent
- initiator/accelerator system
limitations of composite
-shrinkage on polymerization
shrinkage on polymerization leads to…
- stresses at bonded interfaces
- lack of marginal adaptation
- microleakage
function of inorganic filler in composite
reinforcement, radiopacity, control of shrinkage, enhance mechanical properties
coupling agents are typically…
silane compounds
minor components in composite include…
pigments, polymerization stabilizers, UV absorbers
bis-GMA is a monomer with…
- 1 methacrylate at each end
- a rigid central part to provide mechanical properties
main drawback of bis-GMA
high viscosity
why does shrinkage occur in polymerization?
molecules have to approach their neighbors to form
chemical bonds
The ______ that are produced during setting of dimethacrylate resins produce
_______
cross-linking reactions, volumetric shrinkage
approaches to low shrinkage resins
- low shrink methacrylate monomers
- silorane chemistry
methacrylate monomers have _________
Increased distance between the methacrylate
silorane chemistry utilizes
ring-opening polymerization
inorganic fillers…
___ strength on compression
___ surface hardness/wear resistance
____shrinkage
increase, increase, decrease
inorganic fillers…
contribute to _____
____ control of exothermic heat
may ____ confer radiopacity
esthetics/translucency, increase, increase
The filler is _____ than the resin.
stronger and more rigid
Silanes are relevant to the long-term _____ of the composite
hydrophobicity
inorganic filler variables
filler composition, filler content, filler particle size
filler composition made by grinding process, rough surface and hard to obtain/maintain smooth surface, very hard
crystalline silica or quartz mineral
filler composition that has very poor handling if used alone, modified w pre-polymerized resin, excellent polishability
fused silica
filler composition made by grinding to desired particle size, limited on how fine grind can be
glasses (Barium or Strontium glass)
filler composition that is approximately spherical particles, good polishability
sol-gel filler (zirconia-silica)
size of macrofillers; type
100-10um; crystalline silica/quartz mineral
size of small/fine fillers; type
10-0.1 um; melted glass
size of microfillers; type
0.1-0.01um; agglomerated
size of nanofillers; type
0.1-0.005um; zirconia/silica
classification of composites based on flow properties (by incr. viscosities)
sealants, flowable, anterior, universal, packable
sealants are based upon _______ and contain ______.
dimethacrylates resins, none or small amounts of inorganic
fillers
flowable composites have ______ and are mostly used for _______, sometimes as ____
shear thinning property, anterior/cervical restorations, sealants
anteriors are mostly _______, used in Class ___ restorations for its ____ properties
microfilled composites, Class III and IV, esthetics
universal/multipurpose are _______ composites, have good ______ and very good
hybrids and nano; polishability; mechanical properties
universal/multipurpose composites can be used in ______
anterior or posterior restorations
Packable composites are almost completely out of the market because…
they did not match the
desired initial handling properties
challenges of bulkfill composites…
polymerization shrinkage, viscosity, depth of cure
attempts to approach viscosity in bulkfill
- heating composite
- incorporating agents to modify viscosity
attempts to approach depth of cure in bulkfill
-germanium-based initiator that has a different absorbance spectrum
attempts to approach polymerization shrinkage
-introduce monomers that minimize stresses acting as modulators
Resin composites that can be used for restorations using a single increment
bulk-fill composites
