bds2 intro to dental materials Flashcards
questions to ask regarding treatment plan for removal of caries and restoration
which material is suitable
how to use material
explain the options to the patient
select the material
the behaviour of dental materials affects which stages of the clinical episode, explain why
selection - best type
preparation - cavity design and tooth surface
placement - technique
performance - quality of fit and longevity
patient expectations - aesthetics and durability
what does the CE mark indicate
that a material is safe provided you use it for the designated purpose
list some common restorative materials
amalgam
composites
glass ionomer cements
composers
porcelain
which impression material is a hydrocolloid
alginate
which impression material is an elastomer
polysulphides
polyethers
silicones
features of composite resin in restorations
initially will flow out of the cartridge (low and high viscosities exist)
sets within margins and hardens
what is the negative replica of impressions materials
the recorded dentition - ie initial impression
describe the features of impression materials
flows into tray with low viscosity and undergoes a setting reaction to become firm and stable
what is the positive replica of an impression
gypsum - the “fake” teeth
what can happen to a material when forces are applied
stretch or compression depending on the force
deformation either temporary or permanent
fracture
calculation for stress
force / unit area
what are the units for stress
pascals
what is strain
change in length / original length
what is Youngs modules discussing
elasticity
what is the definition of Youngs modulus
elastic (Youngs) modulus is equal to stress over strain
FS
fracture stress
PL
proportional limit
mechanical property terms
hard vs soft
strong vs weak
rigid vs flexible
brittle vs ductile
what is the typical biting force
500 to 700N
biting force in kg
50-70kg
what kind of force is biting
compressive
force directions for compression
force going up and force going down
force directions for tensile
stretching to create fracture - pulling in opposite directions
force directions for sheer
one force acting sideways
what does tensile force do to dimension
change
what is stress measured in
mega pascals
describe what happens with forces to the tooth during grinding and chewing
tooth slides along the surface of the other, frictional forces are experienced
the tooth surface may be abraded, loss of layers of enamel
why is it important that materials adhere to enamel
otherwise the enamel would be removed by masticatory forces
what to consider when choosing restorative materials
what treatment options are there
what material suits each procedure
will that material suit the patients needs and requirements
what’s the design of amalgam
undercut
what is the design of composite resin
minimal
what is the retention type of amalgam
mechanical
what is the retention type of composite resin
adhesive
what are the benefits of an undercut design
keeps the material in place
what are the key features required for materials when filling the cavity
the material must be pliable, fit the shape of interest, and set to form hard, strong material
what is the failure mechanism of a fracture
large force causes catastrophic destruction of materials structure
what is the failure mechanism of hardness
ability of surface to resist indentation
what is the failure mechanism of abrasion
material surface removal due to grinding
what is the failure mechanism of abrasion resistance
ability to withstand surface layers being removed, so compromising surface integrity
what is the failure mechanism of fatigue
repetitive small stresses cause material fracture
what is the failure mechanism of creep
gradual dimensional change due to repetitive small forces
what is the failure mechanism of deformation
applied stress causes permanent changes in materials dimensions but does not fracture it
what is the failure mechanism of debonding
applied forces sufficient to break the material to tooth bond
what is the failure mechanism of impact
large, sudden force causes fracture
what is abrasion
when the tooth grinds along the opposing tooth surface or restorative material at its surface. the surface is abraded and there is loss of material surface layers, causing a roughened surface
how are most failures brought about
when repeated loads are applied, small flaws in a material grow and this allows the fracture when only a relatively small force is applied
what is creep
repetitive forces causing dimensional change
what results in permanent deformation
releasing stress that is greater than the elastic limit
how is debonding used in orthodontics
to remove the appliance, shear force is applied to separate the bracket/bonding material from the tooth surface
main chemical properties for dental materials
setting mechanism
setting time
corrosive potential
main physical properties for dental materials
viscosity
thermal conductivity
thermal expansion
density
radiodensity
elements of the oral environment that can impact dental material behaviours
saliva
temperature variations
pH variations
oral bacteria
