Please enable JavaScript.
Coggle requires JavaScript to display documents.
Introduction to Dental Materials (Can be classified as (Metals and alloys,…
Introduction to Dental Materials
Can be classified as
Metals and alloys
Polymers
Ceramics
Composites
Uses
Preventive (pit and fissure sealants)
Restorative (amalgam, CR, ceramics)
Auxillary (used for fabrication of prosthesis
Properties
Mechanical
overcome biting forces
390-800N in molar region, 155N in incisor region
2 types of forces
Compressive (pushing)-- highest in enamel
Tensile (Pulling)-- highest in dentine, very weak in dentine
Shear (sliding)
Physical
Overcome saliva
Biological
Accomodate living tissues
Stress and Strain
Stress-Strain Curve
Proportional limit: point at which material deviates from law of proportionality between stress and strain
Elastic limit: point at which object starts to permenantly deform
Definitions
Strain: change in shape and size of body
Stress: Force developed within the body
Can be tensile, compressiveor shear
Elasticity
Definitions
Elastic limit:
greatest stress to which a material can be subjected such that it will return to its original dimensions
Ultimate Tensile Strength
: max stress material can withstand before failure
Resiliance:
energy absorbed when material is stressed elastically
Toughness:
Total energy absorbed by the structure before failure
HARDNESS IS THE ABILITY TO WITHSTAND SCRATCHING
Elastic modulus:
indication of stiffness (constant of proportionality between stress and strain)
Physical Properties
Thermal Properties
Thermal Conductivity:
heat passing through a body of 1cm thickness and 1cm2 cross sectional area where temp diff is 1 degree
Specific heat
: heat needed to raise temp of 1g of material by 1 degree
Thermal Diffusivity
: thermal conductivity/ density
Thermal Expansion
: change in length for 1 degree change in temp
Linear Coefficient of Thermal Expansion:
change in unit length per unit length of material for 1 degree change in temp (this is the cause of microleakage)
Heat of Fusion:
heat required to convert 1g from solid to liquid
Electrical Properties
Galvanism:
generated electrical current patient can feel
Corrosion:
dissolving of metals
Optical Properties
Colour
Translucency
Surface Texture
Metamerism:
change in colour due to change in light source
Others
WETTABILITY: measure of affinity of a liquid for solid
high contact angle --> low wettability --> hydrophobic
low contact angle --> high wettability --> hydrophilic
Solubulity: tendancy to dissolve in water
Porcelain/ ceramics are the least soluble
Sorption: uptake of fluids
Rheological Properties
Intro
Studies the flow and deformation of matter
Important for working and setting time
Working time:
period during which material can be manipulated without thickening taking place
Setting time
: time when material has reached given degree of rigidity
Flow and Viscocty
Flow:
deformation under load (i.e. its own load)
Viscocity
: internal friction or resistance of fluid