Dental Materials - Complete denture acrylics Flashcards

1
Q

Define denture base

A

Part of the denture which rests on oral mucosa and teeth are attached

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2
Q

What properties should denture bases have (3)

A

Retentive, stable, supportive

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3
Q

5 functions of denture bases

A
Aesthetic
Support and retain artificial teeth
Support lips and cheek
Stimulate underlying tissues
Eliminate undesirable food
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4
Q

Requirements of ideal denture base material (8)

A
Natural appearance
Easy processing
Easy to clean
Easy to repair
Inexpensive and long shelf life
Biocompatible
Resistant to bacterial contamination
Radio-opaque 
Heat transfer
Adequate mechanical properties (strength, stiffness, hardness, toughness)
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5
Q

Why should denture bases material be radio-opqaue?

A

Can be seen on X-ray if swallowed

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6
Q

What is the most common material used as a denture base?

A

Acrylic denture base - PMMA

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7
Q

Composition of PMMA

A

Powder and liquid
Powder = polymer
Liquid = monomer

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8
Q

4 stages of polymerisation

A

Activation
Initiation
Propagation
Termination

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9
Q

Denture processing problems

A

Porosity

Strains

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10
Q

List 3 types of porosity

A

Polymerisation shrinkage = contraction porosity
Volatilisation of monomer = gaseous porosity
Granular porosity

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11
Q

Cause and manifestation of contraction porosity

A

Insufficient material or pressure

Porosity throughout denture

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12
Q

Cause and manifestation of gaseous porosity

A

Vaporization of monomer during processing

Porosity in localised area (thicker parts)

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13
Q

Cause and manifestation of granular porosity

A

Incorrect polymer:monomer ratio

Porosity appears in thin sections - white frosty appearance)

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14
Q

What types of processing strains can occur?

A

Warpage, crazing, distortion

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15
Q

What problems can occur when a patient cleans the acrylic denutre?

A

Brush and paste = scratching and abrasion - (hardness of material)

Soaking = oxygenating cleanser and water temperature

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16
Q

Advantages of PMMA

A

Aesthetics
Easy and cheap
Low density

17
Q

Disadvantages of PMMA

A
Low strength and toughness
Susceptible to distortions
Prone to discolouration
Low thermal conductivity
Radiolucent
18
Q

Strength

A

Ability to withstand applied load without plastic deformation or failure

19
Q

Toughness

A

Ability to absorb elastic energy and deform plastically before fracturing

20
Q

Types of adverse reactions to PMMA

A

Irritant contact dermatitis
Oral lichenoid reactions
Contact urticaria