intro to dental material science
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what is the dental procedure
• examination • diagnosis • treatment plan (which material is suitable, how to use material, explain options to patient, select material)
what is the effect of dental materials
• selection = adequate, best type • preparation = cavity design, tooth surface • placement = technique, increments, curing • performance = quality of fit, longevity • patient expectations = aesthetics, durability
what does the dental material need to have to be safe
• a CE mark = an essential requirement, show material is safe
why just you not assume new materials are good
manufactures are constantly making new materials, but art doesn’t mean that they are better - should read about material before using it
what are different types of restorative materials
• amalgam • composite • glass ionomer cements • compomers • porcelain
what are different types of impression materials
• impression compound • impression paste • hydrocolloids = alginate mainly • elastomers = polysulphides, polyethers, silicones
what are different types of metals/alloys
• amalgam • cobalt chromium • titanium • gold • stainless steel
what are challenges in choosing materials
• so many materials to choose form • constant changes to products and names • range of brands
what is porcelain used for
veneers
what is composite resin
used for restorations • can come in cartridge or nozzle • low to high viscosities available
how do impression materials work
• record dentition in negative replica • flows into trays at low viscosity • undergoes setting reaction - becomes firm, stable • gypsum (dental stone) = gives positive replica
what is PMMA
a denture base material
what are the mechanical properties of the materials
• force applied to material • stress • strain • elastic modulus
what are some mechanical forces materials are subjected to
• biting, chewing, grinding
what may happen to the material from the force applied to it
• stretch/compress = depends on how force is applied • deform/ change shape = temporarily (during application) or permanently • fracture = failure
what types of force can be applied to the material
• compressive = squeeze material • tensile = stretch • shear = object bonded to another surface and apply force along parallel line of object
what is stress
force acting on an area
what is strain
change in length/original length
what is the stress-strain curve
• most materials have one • FS = fracture stress • star = proportional limit (up to here stress and strain are proportional) • elastic modulus is in mega pascals (its the slope)
what is the elastic modulus
• also called Young/s modulus - is the rigidity/stiffness of the material
what are the 4 mechanical properties and their opposites
• hard / soft • strong / weak • rigid / flexible • ductile / brittle
what mechanical properties does enamel have
• hard • strong • rigid • brittle
what is the typical biting force
• is a compressive force applied to upper tooth when biting - typical biting force = 500 to 700N
what type of forces are grinding/chewing
• shear forces • tooth slides along surface of another • frictional forces are applied • shear forces can remove restorations (material needs to adhere to enamel or it will be removed by masticatory forces)