L1 properties of dental materials Flashcards
4 classes of dental materials
- Metals
- Ceramics
- Polymers
- Composites
[mcpc]
3 categories of dental materials
- Preventive
- Restorative
- Auxiliary
category of dental materials
- Cement, coating, or restorative materials
- Either seals pits and fissures OR releases a therapeutic agent
(e.g. fluoride and/or mineralizing ion), to prevent or arrest the demineralization of the toot structure
preventive
category of dental material
- Metallic, ceramic, metal-ceramic, or resin-based
- To replace, repair, or rebuild teeth and/or enhance
esthetics
restorative
category of dental material
- Fabricate dental prostheses, appliances, and indirect restorations
- These substances DO NOT constitute part of these devices or restorations
- Not all materials exists inside the oral cavity after using them (e.g. gypsum products to make a diagnostic cast)
longevity of dental materials
- temporary / short-term: days-weeks
- intermediate.moderate: months
- long-term: years
agencies that certify dental materials
- National Bureau of Standards (National Institute of
Standards and Technology-NIST) - ADA - American Dental Association on Scientific Affairs
(from 1928) - ISO - International Standards Organization
- FDI - Federation Dentaire International
property
- Free of agents that can elicit hypersensitization or an
allergic response from both the dentist and the patient - not teratogenic (fetus-harming) & carcinogenic (cancer-forming)
biological
property
- Based on the ways in which substances interact,
combine, and change at the molecular level, as
governed by their outer orbital electrons
chemical
[adsorption/absorption]
1. Process wherein liquid or gas molecules ADHERE firmly to the surface of solid or liquid
2. Process wherein liquid or gas molecules PENETRATE into the solid material
adsorption; absorption
[diffusion/osmosis]
- Random motion of MOLECULES; net flow: high to low conx
- Diffusion of SOLVENT; net flow: low to high conx
diffusion; osmosis
Extent to which a material will dissolve in
a given fluid
solubility
ideal cement: ___ solubility, ensuring it
remains intact + resistant to degradation
in the oral environment
low
Loss of material from the surface due to
chemical degradation with mechanical
action
erosion
Surface discoloration on metal
tarnish
- Metal is attacked by natural agents such as air and liquid (rusting)
- This is why noble metals is used (gold, palladium, titanium)
corrosion
Measure of how well heat is
transferred through a material by the
conductive flow
thermal conductivity
Rate of heat flow is proportional to __ & __
area & temp gradient
SPEED with which a TEMPERATURE CHANGE will spread through an object when one surface is heated
thermal diffusivity
___ has the highest the greatest thermal conductivity and diffusivity
gold
LENGTH CHANGE per unit of the original length when temperature is raised by 1 C
COEFFICIENT OF THERMAL EXPANSION (CTE)
___ has the greatest coefficient of thermal expansion
inlay wax
IF COEFFICIENT OF THERMAL EXPANSION IS ___ = MATERIAL IS MORE SUSCEPTIBLE TO TEMPERATURE CHANGES
high
- High coefficient of thermal expansion means the material
more prone to distortion
process of heating and cooling
percolation
process of heating and cooling
percolation
The difference in charges within one tooth forms the electrical
mechanism
electrical
- When the patient feels a sudden sharp sensitivity or pain
- Happens because there is an interaction between two different
metals
galvanism / galvanism shock
physical – color & optical effects
- The amount of light that is absorbed by the material
- When the material allows light to pass through it even slightly, it is then considered as translucent
opacity
physical – color & optical effects
3 dimensions of color:
VALUE - gray scale
HUE - dominant color/wavelength
CHROMA - degree of saruration
physical – color & optical effects
- Natural tooth structures absorb light at
wavelengths too short and not visible to
the human eye/we cannot see - The energy absorbed is then converted into a light of higher wavelength and therefore becomes a source of light
fluorescence
physical – color & optical effects
- Depends on the amount of x ray energy absorbed by an object
radiopacity
Study of the deformation and flow characteristics of
matter under stress, whether solid or liquid
rheology
rheological property
- Resistance to fluid flow
- It is controlled by internal frictional forces within the liquid
viscosity
rheological property
- The slow deformation of a material when
it has completely set - Time-dependent plastic strain of
material under a static load
creep
- Higher creep = slower deformation
overtime even when it is already set
rheological property
- Slow deformation of a material when it has not yet set
- Measure of its potential to deform even under small static load
flow
rheological property
- Substances that become less viscous / flowy when subjected to shear stress (shaken, stirred, squeezed, patted,
vibrated)
THIXOTROPIC
FLUIDS
rheological property
- Resistance to flow increases as the rate of deformation (shear strain rate) increases
- More rapid stirring = more viscous
overtime
dilatant fluids
rheological property
- Opposite to dilatant fluids
- More rapid stirring = less viscous overtime
- More easy to flow
PSEUDOPLASTIC FLUIDS
Characterizes a material’s resistance to elastic
deformation, plastic deformation, or fracture under an
applied force
mechanical
Newton’s third law of motion
every action there is
an opposite reaction (thus, cusps have opposite forces
on the opposing teeth)
- Measure of the ability of a material to resist
indentation, abrasion, or wear - affected by STRENGTH, PROPORTIONAL LIMIT, DUCTILITY
hardness
- Relative deformation of an object due to stress
- Change in length per unit length
- May be elastic (reversible), plastic (irreversible) or both
strain
- Relative stiffness or rigidity of a material which is measured by stress-strain curve slope
- Ability of a material to resist elastic deformation under load ⭐️
elastic modulus
flexibility
___ - the stress above which a material will not
recover to its original state when the force is removed
(beyond elastic strength)
___ - ability of the material to resist bending,
making it more rigid
elastic limit; flexural strength
- amount of energy absorbed by a structure when it is stressed
to its proportional limit - Materials with larger elastic area in the stress strain plots has
higher ___ (resistance to deformation)
resilience
- Subsequent failure of a material when subjected to
intermittent stresses over a period of time. - Use of material causing defects and microcracks but does not break readily
fatigue
ability of a material to sustain a large
permanent deformation under a TENSILE LOAD
without rupture
ductility
Ability of a material to sustain considerable permanent deformation without rupture under COMPRESSION
malleability
Total amount of elastic and plastic deformation energy required to fracture a material and it is a measure of the resistance to fracture
toughness
resistance of brittle materials to
crack propagation under and applied stress
resistance toughness
toughness depends on __ & __
strength & ductility
relative ability of a material to sustain plastic deformation before fracture of the material occurs
brittleness
Relative ability of a material to sustain plastic
deformation before fracture of the material occurs
brittleness
Predicts the behavior of material
STRESS-STRAIN CURVE
