Introduction to Dental Materials Science
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what clinical stages does the behaviour of dental materials affect?
selection, preparation, placement, performance, patient expectations
what mark indicates that a material is safe to use?
CE mark
what are the different options for restorative materials?
amalgam, composites, glass ionomer cements, compomers, porcelain
what are the main types of impression materials?
impression compound, impression paste, hydrocolloids, elastomers
what type of impression material is alginate?
hydrocolloid
what are the different types of elastomers?
polysulphides, polyethers, silicones
what are the different types of metals/alloys?
amalgam, cobalt chromium, titanium, gold, stainless steel
what are the different groups of properties a material can have?
mechanical, chemical and physical
what does force applied to the material cause?
stretch/compress, deform, fracture
what are the different types of force?
compressive (vertical forces pushing material together), tensile (horizontal forces pulling material apart) and shear (force coming from one side pushing the material)
on the stress strain curve where is the proportional limit?
where the slope ends and starts to curve
on the stress strain curve what is the elastic modulus?
the angle between the slop and the strain
on the stress strain curve what is the fracture stress?
the end of the entire line at the curve
what are the mechanical properties of enamel?
brittle, hard, strong and rigid
what type of force is the tooth subjected to when biting
compressive
what type of force is experienced when grinding/chewing?
frictional
what type of force removes materials which are adhered to enamel
shear forces by mastication
what are the different ways that materials fail?
fracture, hardness, abrasion, abrasion resistance, fatigue, creep, deformation, de-bond, impact
how does a material fracture?
biting forces gradually increased to fracture point
describe the hardness test
an indentor with a 100g mass is applied to one spot on the material
how does abrasion occur?
tooth grinds/slides along the opposing tooth surface so the tooth surface is abraded
what occurs due to fatigue?
when repeated loads are applied, small flaws in a material grow allowing fracture when only a relatively small force is applied
what is creep?
repetitive forces cause dimensional change
what causes permanent deformation?
releasing stress that is greater than the materials elastic limit