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Chapter 5
Direct Polymeric Restorative Materials
59
Architecture
Undergraduate 1
06/23/2013

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Term
What are polymers?
Definition
materials made of large, long molecules formed by chemically reacting monomers
Term
What is polymerization
Definition
chemical reaction linking monomer together to form a polymer
Term
What are thermoplastic polymers?
Definition
can be heated and shaped, remelted and reprocessed
Term
What are thermoset polymers?
Definition
-cross-linked structure
-Cannot be heated and molded, need to be in final shape when polymerization occurs.
Term
What are some examples of thermoset polymers?
Definition
dental resins/composites are thermoset polymers
Term
What do heat activated acrylic resins use as the initiator? The activator?
Definition
-benzoyl peroxide as the initiator
-heat is the activator (powder/liquid system)
Term
What usually requires heat activated acrylic resins?
Definition
denture bases
Term
What do chemically activated acrylic resins and composite materials commonly use as the initiator and activator?
Definition
initiator- BPO
activator- a variety of chemicals (tertiary amines)
Term
What are chemically activated materials?
Definition
usually a powder and liquid mixed together
Term
What are chemically activated materials used to create?
Definition
temp crowns, impression trays, orthodontic retainers
Term
How do light activated work?
Definition
activator absorbs light and then reacts with the initiator (dental composites)
Term
How does Dual-cure activated work?
Definition
set by chemical reaction and light
Material that cannot be reached by light sets by chemical rx
Term
What does an inhibitor do?
Definition
destroys free radicals delaying polymerization allowing for more working time
Term
What is a commonly used inhibitor?
Definition
hydroquinone
Term
are polymers with unfilled resins suitable for restorative use?
Definition
no
Term
Why aren't polymers with unfilled resins suitable for restorative use?
Definition
1.polymerization shrinkage
2.coefficient of thermal expansion
3.strength and abrasion resistance of polymeric materials
Term
polymerization shrinkage
Definition
polymers shrink – bonding materials reduce gaps in restoration
Term
Coefficient of thermal expansion:
Definition
unfilled resins = 2 to 10 times greater than tooth structure
Term
Strength and abrasion resistance of polymeric materials:
Definition
unfilled resins unable to withstand occlusal forces
Term
How are plastics useful for a cavity prep?
Definition
Plastics are useful because they can be placed in a cavity prep and molded and shaped in the mouth
Term
Who developed the first dental composites?
Definition
Dr. Raphael Brown
Term
What are fillers?
Definition
strong ceramic materials added to polymer (silica and glass materials)
Term
What do silane coupling agents do?
Definition
Enables adhesive materials to bond ceramic restorations to tooth structure
Term
BLANK improve strength, have low thermal expansion
Definition
fillers
Term
What happens if all filler particles are not properly wetted by liquid monomers?
Definition
voids and gaps between the filler molecules result
Term
Are most composites light activated?
Definition
yes
Term
What are the components of dental composites?
Definition
-matrix
-fillers
Term
What is the matrix of a dental composite?
Definition
-polymer (bis-GMA) or a similar monomer
Term
What is the diluent?
Definition
organic chemical added to the matrix to control the viscosity of the final product
Term
What does the matrix do? What is bad about it?
Definition
-it is the phase that polymerizes to form a solid mass and bonds to the tooth surface
-weak and absorbant
Term
What are fillers? What do they do?
Definition
-engineered glass materials mixed with polymer to form a paste
-improve strength
Term
Filler size
Definition
larger particles make a rougher surface
Term
Evolution of fillers
Definition
evolved into softer particles that stay embedded in matrix
Term
Filler content(amount of filler)
Definition
when filler content increases shrinkage decreases when polymerized
Term
What are polymerization systems used for?
Definition
the convert the matrix filler paste to a solid composite material
**used by all dental composites**
Term
Chemically activated polymerization systems
Definition
2 paste systems
Limited amount of working time
Term
What are light activated working materials? What is the working time determined by?
Definition
-single paste mixed by manufacturer
-light source can damage eyes
-working time determined by user (have virtually replaced chemical activated
Term
What are macrofilled composites? Particle size? Filler content?
Definition
-quartz material
-particle size 10-25 um
-filler content is 70-80% by weight
Term
What is a down side to macrofilled composites? What are they used for?
Definition
-Rougher causes greater plaque accumulation and staining
-Not used anymore except in ortho
Term
What is the size of microfilled composites?
Definition
.03-.5 um particle size
40-50% filler (silica)
Term
What are some good things about microfilled composites?
Definition
-Polish very smooth and lustrous
-Increased thermal expansion and low strength
-Good for class V restorations because of high MOE
-Flex with tooth
Term
What are hybrid composites?
Definition
wider range of particle sizes
.5-1 um in size (.1-3 um)
75-80% filler content by weight
Term
What are some good things about hybrid composites?
Definition
-strong, polish well
-used for many restorations
Term
What are nano sized particles?
Definition
improved hybrid composites that have improved strength and shrinkage
-100 times smaller than the thickness of a human hair
Term
How can a restoration be made to look more natural?
Definition
Layering materials with different shades and translucencies
Term
What are opaque materials used for?
Definition
to prevent underlying color from showing through
Term
What kind of situations are composites good for?
Definition
Low to moderate stress situations. Not good for cusp replacement.
Term
Why are ceramic restorations so expensive?
Definition
have to be made outside of the mouth
Term
What are some factors effecting the placement of composites?
Definition
-depth of cure
-incremental addition
Term
How does the depth of cure effect the placement of composites?
Definition
-thickness of material to be cured
-Pulpal irritation occurs if composite material nearest pulp is not fully cured.
Term
WHat is incremental addition?
Definition
placing composites in layers allowing for shrinkage toward the tooth
Term
What are the first 5 steps in placing a composite restoration?
Definition
1.Diagnose lesion
2.Determine shade(s) needed
3.Isolate area to be treated
4.Cut the preparation
5.Determine the need for a liner
Term
What are steps 6-13 of placing a compositre?
Definition
6.Etch, prime, place, and cure adhesive
7.Incrementally place and cure composite
8.Finish
9.Check for interproximal contacts
10.Examine for voids and marginal defects
11.Polish
12.Remove rubber dam
13. Check occlusion
Term
How do composites feel to an explorer?
Definition
Feel a bit softer than enamel to a sharp explorer
Term
How does the filler material of composites effect how they look radiographically?
Definition
make them raiopaque
Term
How do glass ionomer materials compare esthetically to composites? What do they release?
Definition
-Esthetics are inferior to composite materials
-Release fluoride
Term
What are glass ionomer products used for?
Definition
Base/liner products and cements under crowns
Term
What are some things to take into account when selecting restorative materials?
Definition
1.Method of cure (light or chemical cured)
2.Patient’s desire for esthetics
3.Strength required by location of restoration
4.Handling characteristics
Term
What is crazing?
Definition
surface cracks formed in a glass ionomer from dehydration
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