Flashcards in Introductory Deck (31)
What does the structure of Dental materials influence?
What are dental composites used for?
Used as restorative filling materials and also available for special tray construction
What is the definition of a composite?
A combination of materials in which the individual components retain their identity and which possess different properties to the components acting alone
What does a dental resin composite consist of?
What does a fibre reinforced material consist of?
-fibres of high strength and modulus
-embedded/bonded to a matrix
What are dental reinforced materials used for?
-construction and reinforcement of denture bases
-inlays and onlays
-crowns and bridges
-posts to reinforce and restore root canal treatment
What are the Legal requirements relating to the prescription of laboratory made dental appliances?
Statement of manufacture offered to all patients receiving dental appliance
What does the legal certificate include?
-patients name and confirmation made for them
-prescribers name and registered address
-technicians name and registered address
-Description of the appliance
-confirmation meets legal standards
What happens if the certificate is not offered?
MHRA enforce directive and failure to offer is a criminal offence
What makes the oral environment hostile?
-loading of 6Kg
-On/off cyclical forces- fatigue
-temperature fluctuations in microsecond
what does the periodontal ligament act as in the mouth?
acts as a shock absorber and permits both vertical and bucco lingual displacement
What materials are used by the dental team?
Describe tensile laboratory test.
Force applied to elongate rod
Describe compressible laboratory test.
-opposite of tensile
-not recommended for brittle materials
When is diametral tensile strength used?
When materials are too brittle for conventional tensile techniques
-splits equally in half
How do you calculate strain?
change in length/original length
how do you calculate stress?
F(N) / A(mm2)
What are the units of strain?
what is modolus?
Measure of stiffness of a material
Describe the linear part strain / stress graph
-the linear region is when stress and strain are equal and this can calculate modulus
how can you tell the resilience on the stress/ strain graph?
The small shaded triangle
how can you tell the toughness on the stress/strain graph ?
whole graph shaded in
Describe surface hardness indentor
Dimensions are measured and expressed as a number,:
-high numbers are low hardness
what are the two types of shear bond force?
Adhesive- two areas cleanly separate
cohesive - if the strength of bond is bigger than the material only some of the material separates
What is used to measure surface roughness?
What is thermal diffusity?
The rate at which the temperature will rise in a material when heat is applied to its surface (high rate of diffusity preferred)
what is rheological properties?
The study of materials flow properties
-rate of viscosity and how it varies with time and rate of shear
What are the 3 types of rheological properties?
Dilatant- viscosity increases with applied pressure
Newtonian- viscosity stays the same with applied pressure
Pseudoplastic - viscosity decreases with applied pressure