Biomaterials Flashcards
What are the main material categories?
Metal, Ceramic, Polymer —-composite = polymer + ceramic
Define Biomaterials
Materials used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissues without causing any harm or negative effects.
ie- materials used to replace body parts
Give examples of synthetic biomaterials.
composite, silicone impression material
Give examples of natural biomaterials.
alginate, hydrocolloids
Give examples of tissue-engineered biomaterials.
stem cells, replacement tissues
What is meant when talking about a materials structure?
bonds, anatomic arrangement, composition, defects
What is meant when talking about a materials properties?
physical, chemical, mechanical, degradation, biologic
What are the general mechanical concepts of metals?*
hard
ductile = tough
strong
What are the general mechanical concepts of ceramics?*
hard
brittle
strong
What are the general mechanical concepts of polymers?
soft
ductile = tough
weak
What are the general processing characteristics of metals and ceramics?
high processing temperatures - Thus used for more indirect processes (casting a crown)
What are the general processing characteristics of polymers?
low processing temperatures - Thus, used for more direct processes. (heavy and light body for a crown impression)
True or False - Metallic bonds are not directional
True
How many electrons are in the outer shell of a metal element?
1,2, or 3
True or False - Electrons are tightly bound to the nucleus of a metallic element.
False
What happens to a metal once it cools down from being heated to a molten metal?
crystallization of the metal occurs and forms grains (groups of crystals)
What are some characteristics of gold?
most noble metal most ductile and malleable metal melts at 1063 degrees C not tarnished by air or water not soluble in HCl, H2SO4, or HNO3 can be etched by aqua regia
Is pure gold a good metal to produce a crown?
No, it would need to be mixed with alloy elements.
What is a metal alloy?
A mixture of 2 or more metals
What are some examples of metal alloys used in the oral cavity?
metal crowns
amalgam
Characteristic of metal alloy
Less ductile than a pure metal, but it is stronger
What are some examples of ceramics used in the oral cavity?
all ceramic crowns, cements, gypsum, denture teeth
What are some characteristics of ceramic?
ionic and covalent bonds
directional bonding
What is an ionic bond?
one atom is an electron donor and another is an electron acceptor (a complete transfer of valence electrons)
What is a covalent bond?
a sharing of electrons between two atoms
Are covalent or ionic bonds stronger?
covalent
What are the 3 most common ceramics in dentistry?
SiO2, Al2O3, K2O
What is the building block of ceramics?
The SiO4 tetrahedron
What are the types of microstructure a ceramic can have?
crystalline or noncrystalline
What is an example of a crystalline ceramic?
Quartz or crystobalite
What is an example of a noncrystalline ceramic?
amorphous silicate glass
What microstructure do most dental materials have?
semicrystalline or polycrystalline
What are gypsum and zinc phosphate?
aqueous cements
What are some characteristics of polymers?
covalent bonds
high molecular weight
long molecules composed of nonmetallic elements
What are some common uses for polymers in dentistry?
making provisionals (temp crowns)
adhesives (tray adhesive)
restoratives
registration material (blu-bite)
What are some ways to process a polymer?
light activation
initiation of a monomer
propagation or termination of a free radical
What is the formation of a polymer?
liquid(monomer) to solid (polymer) through polymerization
What are the 4 stages of a chain reaction polymerization?
activation, initiation, propagation, termination
What occurs during the activation stage?
the free radical is activated
What occurs during the initiation stage?
the free radical binds with the monomer leaving a double bond opening
What happens during the propagation stage?
chain growth, volume decrease, and shrinkage
What are two monomer functional groups?
monomethacrylates
dimethacrylates
Describe the structure of monomethacrylates.
linear chains
Describe the structure of dimethacrylates.
branched and crosslinked
Are polymerization reactions fast or slow to complete?
They are usually quick and can generate heat.
What are some characteristics of direct restorations?
less preparation, one visit to complete, often do not last as long
What are some characteristics of indirect restorations?
More preparation, expensive, longevity, multiple visits to complete
What biomaterial(s) is/are typically an indirect approach to restoration?
metals and ceramics (high processing temperatures) EXCEPT: amalgam and cements
What biomaterial(s) is/are typically a direct approach to restoration?
polymers (low processing temperature) EXCEPT indirect composites
What is a composite?
mixture of metal and/or a ceramic and polymer
What is “ rule of mixture”?
a weighted mean used to predict the properties of composite.
What is density?
weight/volume
What is specific gravity?
density of a material/density of water
What is the density order of metals, ceramics, and polymers beginning with the most dense?
metal, ceramic, polymer
What does a base need to be place under an amalgam restoration?
amalgam is a thermal conductor - heat from the environment can conduct through the amalgam and irritate the pulp, causing sensitivity to the patient
Does a composite restoration need a base?
no, composite has a low thermal conductivity
True or False - Color has 4 dimensions
False - it has 3
What are the 3 dimensions of color?
Hue, Value, Chroma
What is Hue?
a dimension of color that involves the wavelength
What is Value?
a dimension of color that involves the intensity and brightness of an object
What is Chroma?
a dimension of color that involves the purity and density of an object
Describe metamerism.
when two colors appear the same color under one light source, but look different under another light source
