Introduction To Dental Materials Flashcards
Who invented the visible light curing unit?
Dart and namcek 1981
What was the name of the first dental light curing unit?
ICI dental occlusin
What are dental composites used for?
Restorative filling material
Special tray construction
What does a dental resin composite consist of?
Resin
Filler
Coupling agent
What are fibre reinforced materials?
Light weight
Strong
Used for bulletin proof vests
Used as a type of composite
What are fibre reinforced materials made up of?
Kevlar fibres
Fluoroelastomer rubber
What makes the mouth a hostile environment?
Loading of up to 6kg
On/off cyclical forces- fatigue
Chemicals
Temperature fluctuation
What vertical displacement forces are permitted in the periodontal ligament?
25-100 um
What are the Bucco lingual displacement permitted?
56-108um
What size of force intrudes the tooth?
1N
What size of force flexes bone and causes pain?
15N
What ph fluctuations occur within the mouth?
2-12
What materials are used by the dental team?
Gypsum materials (plaster) Waxes Alloys Polymers Ceramics
What does tensile mean?
Capable of being bent, shaped or drawn out
What is strain?
Change in length/ original length
What unit is strain measured in ?
Strain has no units
What is stress expressed as?
MPa
A is mm2
F is Newtons
What does compressive mean?
The ability to compress- not recommended for brittle materials
What is diamentral tensile strength?
Useful for brittle materials where conventional tensile not applicable
How many points to diamentral tensile strength?
2
How is diamentral tensile strength measured?
2F / pieDL ( diameter, length)
What does flexural mean?
The highest stress experienced at moment of rupture.
How is flexural strength measured?
3FL/ 2bd2
What is ductility?
The potential for material to be drawn out into a wire
What does modulus give?
A measure of stiffness
What is a measure of resilience?
The energy absorbed by material undergoing plastic deformstion up to elastic limit
What is a measure of toughness?
Total amount of energy a material can absorbs to point of fracture
What makes a material tough?
High measure of toughness
What makes a material brittle?
Low measure of toughness
How is fatigue measured?
Application of cyclic loading for a defined number of cycles.
What measures surface hardness?
An indentor
What does a large number on the indentor indicate?
Low hardness
What does a small number on the indentor indicate?
High hardness
What is sheer bond strength?
The amount of force required to break the bond between material and tooth surface
Adhesive failure
Cohesive failure
What is impact strength?
Quoted in units of energy
Measure of the force required to fracture
What is surface roughness measured by?
Profilemeter
What does the Profilemeter do?
Assesses surface characteristics
What does a high reading on the Profilemeter mean?
High reading the rougher the material
What is thermal conductivity?
Rate of heat transfer through a material (K)
What is specific heat?
Energy required to heat up a material (Cp
What is thermal diffusity?
The rate that temperature will rise in a material when heat is applied to its surface ( D )
How is thermal diffusity measured?
Thermal conductivity / specific heat
What are rheological properties?
Study of viscosity
What does dilatant mean re. Rheological properties?
Viscosity increases with applied pressure
Wha t does Newtonian mean re. Rheological properties?
Viscosity remains constant with applied pressure
What does pseudoplastic mean re. Rheological properties?m
Viscosity decreases with applied pressure and unless set increases when pressure decreases
What does corrosion mean?
Defines the chemical reactivity of metals and alloys
What is camphorquinone?
Widely used visible light photo initiator
