Introduction Flashcards
What are the material categories?
Composite, ceramic, metal, and polymer
What kind of material are composite resin and glass-ionomer?
Polymer-ceramic
Are there metal-polymers in dentistry?
No
How are dental materials characterized?
By the structure, properties, applicability, requirements, aesthetics, handling properties, and patient satisfaction
What are examples of suboptimal materials used early in history?
Copper, tin, bronze, and gold
What are materials used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissue?
Biomaterials
Can bio materials cause harm or a negative reaction?
No
What are examples of synthetic biomaterials
Composites and silicone impression material
What are examples of natural biomaterials
Alginate and hydrocolloids
What are examples of tissue-engineered biomaterials
Stem cells, replacement tissues (grow tooth from bud)
Properties of metal
Hard, ductile (bend w/o breaking), strong
Properties of ceramics
Hard, brittle, strong
Properties of polymers
Soft, ductile, weak
Which materials have high processing temperatures?
Metals and ceramics
Which material has a lower processing temperature?
Polymers
Which material tend to be used as direct process materials?
Polymers
How are metals used in dentistry?
Cast metal crowns, implants, metal-ceramic crowns, endo treated teeth
How many electrons do metallic elements have in their outer shell?
1-3
Are electrons tightly or loosely bound to the nucleus in a metal bond?
loose
What does is mean that electrons have free mobility in metallic bonds?
thermal and electrical conductivity, ductility-bend without breaking
What is the microstructure of metals?
polycrystalline structures - single phase-single composition
formation of grains upon cooling
How many metals are mixed in metal alloys?
Two or more
Where are metal alloys used in dentistry?
cast crowns and amalgam fillings
Are metal alloys more or less ductile?
Less ductile and stronger (resists forces)
Why are noble metals used?
To resist reformation and impede dislocations
AKA makes defects less prone to failure
What are examples are solid solution hardening metals?
Gold, silver, palladium, and platinum
True or False
The larger the grain size of the metal, the better the mechanical properties?
False
The smaller the grain size the better the mechanical properties
What is the microstructure of ceramic?
crystalline (long range order) or noncrystalline (short rang or no long range)
What is the microstructure of most dental ceramics?
semicrystalline or polycrystalline
What is the microstructure of dental porcelain?
glass w/ some crystalline residuals )noncrystalline or amorphous silcate glass)
What is the building block of dental procelain?
silicon tetroxide
how is dental procelain processed?
sintering or melt at high temperatures
define sinter
make a powered material (coalesce) into a solid or porous mass by heating
withOUT liquefication
What are some characteristics of polymer bonds?
Covalent bonds, high MW, and long molecules (composed of C,O,N,H)
How do polymers derive their strength?
entanglement and cross-linking or long chains
What are the 4 steps of directpolymerization
Light activation of initiator
Initiation of monomer
Propagation of free-radical
Termination of free-radical
What is the result of activation of the initiator molecule using light?
generates free radical
How is the monomer initiated?
The free radical reacts with the monomer, opening a double bond through electron transfer to free radical, producing a radical monomer
How is polymerization terminated?
There are no longer sites for the radical to react or run out of monomer
Does a polymer change phase during polymerization?
Yes, the monomer is in a liquid state while a polymer is generally solid
Define activation
free radical initiation via a specific wave length of light
Define initiation
free radical combines with monomer, opening double bond
One word definition of propagation
Growth
Effects of propagation
chain growth
decreased V
shrinkage
What is the structural difference between monomethacrylates and dimethacrylates
mono- forms linear chains that are dntangled
di- double amount of double bonds available allow for a branched and cross-linked chain
Does branching and cross-linking increase or decrease mechanical properties and longevity?
increases
What is the speed of polymerization once initiated?
Fast
Does polymerization generate heat?
Yes
What does “in vivo” mean?
direct placement into oral cavity
Why can polymers be used in vivo?
low viscosity stable specific trigger for initiation rapid setting initation can occur at room temperature
Are metal and ceramic able to be used in vivo?
No, they are used indirectly because of high processing temperatures
EXCEPT : amalgam and cements
How are polymers used in dentistry?
temporary crowns, adhesives, restoratives, and impression materials
what are the goals of composite resins?
to achieve some intermediate properties between the two material types (mixture of HA and collagen)
Define rule of mixture
by knowing the phase in the structure of any material and its interfacial interactions, it is possible to predict the overall properties
**know the ratio
What are the materials in dental composite resins?
dispersed phase (glass filler for hardness) matrix phase (monomer resin) photoinitiatior (acitvate polymerization)
what is the purpose on silane coupling agents?
to bond resin and fillers to each chemical to improve mechanical properties
How does increasing filler VOLUME affect the property of composite?
increase strength, increase modulus (stiffness), increase viscosity, decrease shrinkage
How does increasing filler SIZE affect the property of composite?
increases surface roughness
What is the average filler amount? why?
75-80 wt % to produce high strength and stiffness
Give the material structures
atomic arrangement
bonding
composition
defects
What are examples of atomic arrangement?
crystalline (grains) vs non-crystalline (glassy)
What types of bonding are there?
primary - metallic, ionic, covalent
secondary - van der waals, hydroen
What are the 2 aspects of composition?
elements and phases
What are two types of defects?
macroscopic (pores) and atomic scale (microflaws)
What are two mass properties?
density and specific gravity
define density
weight/unit volume
Which materials have the highest and lowest densities?
High = metal Low = polymers
Define specific gravity
relative density or the density of a material/ density of water
Define thermal expansion
a thermal property where most things contract when cold and expand when hot
Define heat flow
a thermal property, measuring the conduction of heat
Do insulators have high or low eat flow
Low
Do metals have high or low conductivity
High
Do composites have high or low thermal conductivity?
Low
What does it mean if a metal has high electrical properties?
it conducts electricity
What is the significance of electrical properties?
corrosion of metal and galvanic reaction
Do composite or ceramics conduct electricity?
No
Define optical properties
its color, translucency, gloss, and surface
determines how light rays interact w/ surface
How many dimensions do colors have?
3
hue (color)
value (intensity)
chroma (pureness)
What is metamerism
two objects of the same color are perceived as different because of different reactions with different light sources
