Test 1

Question 1

•Stress

Answer 1

When force is exerted on a tooth, the tooth creates resistance to counteract the force. The internal force, which resists the applied force, is called

Question 2

Strain

Answer 2

If the stress within an object cannot resist the force, distortion or deformation occurs. The distortion or deformation produced by stress is referred to as

Question 3

Flexural stress

Answer 3

When we chew during mastication, many types of stress are involved and form complex stress combinations. One such combination, tension and compression, is known as
Fatigue failure During mastication, stresses occur repetitively over time causing fractures; this may cause failure of a material. Failures rarely occur in a single-force application, rather they occur when stress is frequently repeated.

Question 4

Force and Stress

Answer 4

•Materials must withstand varying degrees of force or load
•Biting force: Measure of strength of muscles of mastication during normal chewing
–Normal masticatory forces on the occlusal surface of molar teeth:
•Average 90 to 200 pounds per square inch
•Can increase as much as 28,000 pounds per square in on a cusp tip
–Denture wearers apply 40% less force

Question 5

•Compressive force –

Answer 5

squeeze an object posterior teeth/broad occlusal surface and multiple roots.

Question 6

A. Tensile force-

Answer 6

opposite direction or stretched

Question 7

Shearing force-

Answer 7

slide against each other incisors cutting action

Question 8

Torsion or torque

Answer 8

combination of compression and tensile.

Question 9

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•The normal pH of saliva

Answer 9

is 6.2 to 7.0 (neutral); this is fairly neutral but fluctuates during the day. Many materials that are compatible with a neutral environment are not compatible in an acidic one.

Question 10

A soluble material dissolves in fluid.

Answer 10

In the case of the oral environment, saliva is the main solvent. Desirable materials should have a low solubility.

Question 11

Gold and porcelain are retained in the oral environment for many years, because they are insoluble.

Answer 11

Materials that are tooth-colored are more soluble; therefore they do not last as long.

Question 12

Water sorption is the ability to absorb moisture. During placement or over time, most materials react adversely to moisture. Some materials have the undesirable characteristic of water sorption. This absorption of moisture may result in staining or slight enlargement of the material.

Answer 12

Some materials stain as the result of water sorption caused by repeated exposure to coffee, tea, cola, and foods that contain dyes. The breakdown of most dental materials is brought about by moisture, acid, and stress. Materials that are needed to last a long time must withstand this hostile environment

Question 13

Microleakage

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Answer 13

The space between the walls of the preparation and the preparation is called the interface.
•If the interface is not sealed, fluids and microorganisms can penetrate between the tooth surface and the restorative material.
•This seepage of harmful materials, or microleakage, results in tooth postoperative sensitivity, recurrent decay, and marginal staining.

Question 14

Esthetics

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Answer 14

The three components of color result in hue, chroma, and value.
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Question 15

•Hue

Answer 15

•Hue is the dominant color of the wavelength detected. Teeth are seen predominantly in the yellow and brown range.
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Question 16

Chroma

Answer 16

is the intensity or strength of a color.

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Question 17

Value

Answer 17

describes how light or dark a color is.

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Question 18

The color of teeth is also determined by the amount of light that passes through them.

Answer 18

• If light passes easily through a tooth, it is said to be transparent.
• If light is completely absorbed, then the tooth is opaque.
• A combination of the two is typical; the term used is translucent. This life-like quality is called vitality..