properties of dental materials da 122 dental materials
TRANSCRIPT
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Properties of Dental Materials
DA 122 Dental Materials
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Council on Dental Materials, Instruments, and Equipment
Subgroup of the American Dental Association
Sets standards and specifications that all dental materials must meet
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Acidity 1. affect oral tissues:
Changing acidity levels determines use of products in oral cavity
2. acidity of materials may cause irritation to gingival tissue or damage to pulp
Ex. Mountain Dew!!
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Adhesion Chemical or
physical force or attraction that holds unlike substances together
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Biting Forces
Stress
Strain
Tensile
Ductility
Compressive
Malleability
Shearing
Bruxism
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Stress and Strain Stress:
reaction of an object to resist external force
Strain: Enough stress
placed on an object to cause change or deformation
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Tensile Pulls and stretches
a material Tensile stress and
strain causes structure to be elongated
Ex. Tug-of-war
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Tensile Strength
Resistance to a pulling force
Important quality of dental materials
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Ductility Ability of material
to withstand forces of tensile stress without failing
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Malleability Ability of a material
to withstand compressive stresses without fracturing
Capable of being reshaped or flattened
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Shearing Slides one part of
material parallel to another, in back and forth motion
Ex. Cutting with scissors
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Biting Forces
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Bruxism
Grinding of teeth
Example of shearing
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Corrosion
Tarnish: reactions of saliva and metal to cause dullness and discoloration
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Dimensional Change
Shrinkage or expansion of dental material or other substance
Distortion Disfigurement Deformation(remember the 3 D’s!)
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Distortion
Mis-shaped, twisted out of proper or normal shape
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Deformation
Distortion or disfigurement
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Prevention of dimensional changes
Distortion, disfigurement and deformation are all undesirable changes
Occur when dental materials are mishandled
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Elasticity
Capable of maintaining or returning to normal size and shape after having been stretched
EX. Rubber bands
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Flow
To move in a manner similar to a liquid stream
To creep or slump Ex.
Compare water and honey
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Galvanism
Electrical shock resulting when two dissimilar metals contact one another in the mouth
Oral fluids act as a carrier between the two metals
Ex. Biting on a piece of tin foil with an amalgam restored tooth
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Hardness
Resistance of material to scratch or indent “hard as a rock”
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Microleakage
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Retention
Means by which materials and surfaces are held in place 1. mechanical retention 2. chemical retention
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Mechanical Retentionsurfaces are prepared to hold materials in place
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Chemical Retention
Chemical reaction between tooth surface and material
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Bonding Process Process by which
materials adhere firmly or hold together
Dentistry uses bonding agents to bond dentin and enamel with restorative materials
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Solubility www.twinkiesproject.com/solubility.html
Ability/rate of material to dissolve in fluid
Important if material is going to be exposed to the saliva and might dissolve and expose tooth structure
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Thermal Properties
Relate to temperature (i.e. heat)
1. thermal conductivity/sensitivity
2. thermal expansion
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Thermal Conductivity
Ability of a material to feel, transmit, or react to heat
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Thermal Expansion Reaction of
material with heat to cause expanding or contracting
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Exothermic Properties
When a dental material releases heat when it sets Example: pour dental models in gypsum-
heats as it sets
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Viscosity
Ability of a liquid to flow
Thicker material: Less flow More viscous
Olive oil
Thinner material: More flow Less viscous
Vinegar
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Wettability
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Key Terms Activity
Using index cards make key terms for the properties of dental materials
Copyright 2012 Porter and Chester Institute, Inc. All rights reserved