Metallic, Ceramic and Polymeric Biomaterials Flashcards
physical properties of metals
shininess - luster
higher density
conducts heat and electricity
ductile
malleable
high melting point
chemical properties of metals
easily lose electrons, electro-positive elements
metals like to react/have reactive surfaces
loss of mass (some corrode easily)
metal alloys
a metal made from mixing two or more metallic elements to optimize materials properties
biocompatibility of metals
involves the acceptance of an artificial implant by the surrounding tissues and by the body as a whole
why are metals a great choice for implanting into the body
do not irritate surrounding structures
no excessive inflammatory response
do not stimulate immuno-reactions
do not cause cancer
adequate mechanical properties: strength, stiffness, fatigue properties and density
stainless steel biomaterials
favorable combination of mechanical properties, corrosion resistance, cost effective and ease for manufacturing
strong
ductile
biocompatible
cobalt-chrome alloys
high specific strength, high corrosion resistance and good wear resistance
metal framework for dental partials
titanium alloys
most attractive metallic materials for biomedical applications
used for implant devices replacing failed hard tissue
should be free of vanadium and aluminum
amalgam pros
low cost, easy to use, high strength and durable
Zn acts as an oxygen scavenger
long service life
posterior load-bearing locations
resistance to fracture
low margin to leakage over time
amalgam cons
color does not match tooth
somewhat brittle
subject to corrosion and galvanic action
does not help retain weakened tooth structure
concern about waste disposal
mercury in amalgam
unique properties to make it an important component of dental amalgam contributing to its durability
characteristics of gold
weak, soft, flexible, malleable, ductile
resists corrosion and tarnish
has high density
has high melting temperature
has low thermal coefficient of thermal expansion
ceramic biomaterials
an inorganic, non-metallic, crystalline oxide, nitride or carbide material fired at high temperature
used for: metal crowns, partial dentures, all ceramic crowns, inlays/veneers, ceramic denture teeth
form hard, brittle materials due to strong intramolecular bonds
porcelain ceramic biomaterials
family of ceramics composed of kaolin, quartz, and feldspar
porcelain jacket crowns, low-strength and generally limited to anterior teeth
feldspar
main ingredient of dental porcelain
crystalline and opaque
has a colour between grey/pink
has fusion temp ~1150C, depending on purity
impurities impart colour, undesirable
manufacturing of dental porcelains
mixture decomposes to form a glass amorphous phase and crystalline consisting of leucite
mixture is cooled in water to cause mass to shatter - produces frit glass
metal oxides are added to modify colour
glass materials
formed by heating of dry mixtures into a viscous state
then rapidly cooled to prevent crystallinity
glass properties
strong
hard - resists scratched and abrasions
elastic
chemical corrosion-resistant
thermal shock-resistant - withstands intense heat or cold
heat-absorbent - retains heat
optical properties - light
electrical insulting - resists electric current
polymeric biomaterials
a large molecule composed of many smaller repeating units
used for: complete or partial dentures, impression trays, temporary crowns, maxillofacial prostheses
natural polymer
derived from nature
rubber, starch
synthetic polymer
manufactured in a lab, generally with petroleum-based materials
MMA, polystyrene
addition polymers
consecutively adding monomers
polysaccharides
condensing polymers
joining two monomers with elimination of water/acid/alcohol
rearrangement polymers
undergoes rearrangement during polymerization
biodegradeable
from sources like: cellulose, chitin/chitosan
agar
linear polymer
made of two polysaccharides - agarose and agaropectin
linear repeating unit of agarobiose
reversible hydrocolloid
used as dental impression materials
converting monomers to polymers
polymerized chains have molecular weights thousands of times greater than their monomer constituents so the chemical and physical properties of polymers are distinct
cross-linking of polymers
can have very different stability if polymer network is linked together which has two (or more) double bonds that can participate in free radical polymerization
cross-linking of polymers results in
increased rigidity
increased temperature resistance
improved wear
reduced susceptibility to organic solvents
homopolymers
only contain one type of starting monomer
copolymers
when using two monomers for free-radical polymerization
composites
a material with two or more distinct substances
polymers + ceramics
organic resin is a matrix (continuous phase), and hard, ceramic filler particles (discontinuous phase)
synthetic resins are used as restorative materials due to the following properties
insoluble in the oral environment
tooth-like appearance/color
insensitive to dehydration
easily manipulated
relative low cost
