properties of dental materials da 122 dental materials

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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