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Dental Materials Test 1
Dental Materials Test 1
96
Biology
Graduate
09/28/2010

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Term
renkiology
Definition
study of x-ray
Term
retrognatic
Definition
retruded jaw
Term
prognathic
Definition
protruding jaw
Term
bleaching
Definition
stripping teeth of enamel leads to tooth sensitisation
Term
matter
Definition

material substance that occupies space and has weight

 

divisions (atom, molecule, compound), properties (chemical and physical) and states (solid, liquid, gas)

Term
solids
Definition
crystalline lattice structure
Term
amorphous
Definition
definite shape but no fixed anatomical position
Term
liquid
Definition
tendency to chere, and defined by container
Term
gas
Definition
moves like liquid, expands indefinitely
Term
stress
Definition

internal resistance to external force being place on an object;

measured in F/Area units; PSI or Pascals (N/m2)

measurable quantity

 

Term
compressive stress
Definition
forces on an object are directed toward one another
Term
tensile stress
Definition
forces are directed away from one another (pull apart)
Term
shearing stress
Definition
forces on an object are directed in such a manner to twist, rotate or deform the object by sliding one part parallel to the other (harmful to the human dentition)
Term
strain
Definition

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Term
ultimate strength
Definition
maximum stress before fracture; stress-strain curve is at its highest point
Term
plastic/permanent deformation
Definition
the object will never return to initial state
Term
yield strength
Definition

falls around the deformation range; "when the object gives."; atomic cracks form after ultimate strenght

 

industry standard giving manufacturer a range as to when the material tends to fail; 0.2% offset below the linear portion of the stress-strain curve

Term
toughness
Definition
measured at its point of fracture
Term
elstic modulus (Young's Modulus)
Definition
measure of materials stiffness; stress/strain until no longer proportional
Term
proportional limit
Definition
stress proportional to strain; at stresses that exceed the proportional limit the object no longer retains its orginal shape
Term
maximum flexibility
Definition
strain associated with stress at the proportional limit
Term
maximum flexibility
Definition
strain associated with stress at the proportional limit
Term
plastic deformation
Definition
small but permanent dimensional change
Term
brittle
Definition
low ductility; less stress to achieve deformation
Term
ductility
Definition
ability of a material to withstand permanent deformation under tensilee stress without fracture
Term
malleability
Definition
ability of a material to withstand permanent deformation under compressive stress without fracture; predominate in metal; metallic component
Term
% elongation
Definition
amount of deformation a material can withstand without rupture when a tensile stress is applied
Term
% compression
Definition
amount of deformation a material can withstand w/o rupture when a compressive stress is applied
Term
Poisson's ratio
Definition
ratio of axial to lateral strain within the elastic range; reduction of cross-section is proportional to the elongation during elastic deformation
Term
temperature
Definition
degree of hotness or coldness measured on a definite scale
Term
heat of fusion (L)
Definition

heat in calories, or joules, required to convert 1 g of a material from solid to liquid state at the melting temperature

 

L=Q/m (Q = total heat absorbed)

Term
thermal conductivity (K)
Definition
transmission of heat; quantity of heat in calories of joules, per second passing through a body 1-cm thick with a across section of 1 cm2 when the termpature difference is 1 celsius degree
Term
specific heat
Definition
quantity of heat needed to raise the temperature of 1 g of the substance 1 degree
Term
thermal diffusivity
Definition

measure of transient heat flow and is defined as the thermal conductivity, divided by the product of the specific heat;

 

rate at which body with a non-uniform temperature approaches equilibrium

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o   Delta = K / (Cpr) mm2/sec

 

Term
linear coefficient of thermal expansion
Definition

measure of change in length per unit lenght when the temperature is raised 1 degree higher

 

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o   (DL/L)/( Dt)

 

Term
transmission
Definition
light passes completely through an object
Term
reflection
Definition
light not allowed to pass at surface or incompletely below surface
Term
absorption
Definition
light entering does not leave
Term
metamerism
Definition
colors under a fluorescent light source differ under a natural light source
Term
flourescene
Definition
: emission of visible light as a result of absorption of radiation from some other source
Term
galvanic shock
Definition
2 dissimilar metal placed in oral cavity can create a battery cell; galvanic cell can cause galvanic shock
Term
face-centered space lattice
Definition
composes gold, copper, silver, and platinum
Term
hexagonal close-packed space lattic
Definition
Zn structure (anti-oxidants are rust protectors)
Term
creep
Definition
permanent deformation under constant load in crystalline materials
Term
flow
Definition
permanent deformation under constant load in amorphous materials
Term
resilience
Definition
area beneath the linear portion of the stress-strain curve; energy to deform material permanently
Term
toughness
Definition
total area under the stress-strain curve; energy to cause fracture
Term
hardness
Definition
material resistant to identation
Term
KNOOP test
Definition
standard hardness test; 172-130 degree elongated diamond used for micro-identation tests; thin plastic/metal sheets; brittle materials
Term
BHN, Brinnell Hardness Tester
Definition
metals and alloys; fixed ball diameter and fixed load; 1.6 mm ball diameter - load of 123 N; force/area
Term
vickers hardness tester (VHN)
Definition
136 degree diamond pyramid; measures small areas, very hard materials; Vickers can be altered
Term
rockwell hardness test
Definition
developed as a rapid method of determing hardness, the superficial method is used to measure hardness of plastics used in dentistry; place load on plastic and make measurement
Term
barcol hardness test
Definition
studies depth of cure of resin composites; spring loaded needle 1 mm in diameter
Term
shore A hardness test
Definition
shore A durometer used to measure relative hardness of elastomers
Term
nano-identation
Definition
used to measure the properties of microphase (0.1-5000 mg)
Term
rheology
Definition
study of flow of liquids; in relation to viscosity; viscosity decreases rapidly as temperature is increased
Term
adhesion
Definition
bonding between unlike materials
Term
cohesion
Definition
bonding between similar materials
Term
adhesive
Definition
material used as a binding agent
Term
adherend
Definition

surface to which the adhesive is applied

 

greater the surface energy of the adherend, the more readily the adhesvive reacts with the adhesive

Term
surface wetting
Definition
ideal adhesive has a contact angle that approaches, but can never attain zero degrees
Term
surface tension
Definition
reduction in surface tension of all liquids as the temperature is increased
Term
detergents
Definition
reduce the surface tension in water
Term
adsorption
Definition
surface attachment of molecules; 2 substances cohere, two unlike substance adhere
Term
absorption
Definition
substance absorbed diffuses into solid material and not noted of a concentration of molecules at the surface
Term
sorption
Definition

absorption and adsorption taking place at the same time

 

water absorbed on the surface and absorbed into the body of the material

Term
capillary rise
Definition
penetration of liquids into narrow crevices is known as capillary action (flowable composite)
Term
penetration coefficeint
Definition
rate of penetration of a liquid into a crevice
Term
isolated capillaries
Definition
adhesion of liquid bridges between solids; isolated capillaries from reservoir
Term
sealants
Definition
placed on the posterior of children's dental caries; also placed on adult teeth
Term
gypsum
Definition
calcium sulface dihydrate
Term
plasters
Definition
fluffy, porous, least dense
Term
hydrocal
Definition
dental stone
Term
densite
Definition
densest of the raw gypsum; strongest and least amount of water required to make product set
Term
Type I
Definition

impression plaster; inelastic material; requires different fillers and retarders, used with patients with no undercut areas

water/poser ratio: 50 cc water/100 grams

 

Term
Type II
Definition
plaster of parish; made through open kettle method; weaker than stone
Term
dental stone
Definition

occurs under steam or autoclave pressure in presence of water;

alpha hemihydrate, made w/ water/powder: 30 cc water/100 gram

Term
type III
Definition
dental model stone, makes didagnostic cast; maxillary and mandibular replica of patient's mouth
Term
type IV
Definition
die stone; 20 cc water/100 grams type IV
Term
type 5
Definition
high-strength dental sotne; 18.62 cc water/100 gram
Term
algenate
Definition
impression material used today
Term
spatulation
Definition
longer, more rapidly the gypsum is mixed the shorter the setting time
Term
water temperature
Definition
warmer the water, decreases the setting tme
Term
room temperature
Definition
higher temperature, reduces setting time
Term
setting expansion
Definition
all gypsum products expand during setting (0.1 to 0.3 percent)
Term
initial setting time
Definition
measured by Vicat penetrometer
Term
final setting time
Definition
time-time at which the material can separate from the impression without fracture
Term
compressive strenght
Definition
shows relatively high compressive strenght; brittle procuts
Term
zn oxide
Definition
eugenol impression paste
Term
catalyst paste
Definition
eugenol
Term
base paste
Definition
ZnO; setting runs to conclusion
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