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