lec 2Principles and essential of RPD design pptx - د.رضوان

PRINCIPLES AND ESSENTIAL OF REMOVABLE PARTIAL DENTURE DESIGN

BY
Assis.Prof.Radhwan Himmadi Hasan
2018
2/26/2018
Assis.Prof.Dr.Radhwan H. Hasan
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• Basic Considerations

• Biomechanics at play within the oral cavity must be taken into consideration and the denture design must be made in accordance, to counteract the mechanical forces/stress acting within the oral cavity.
• Forces to consider:
• Vertical – Displacing
• - Dislodging forces
• Horizontal forces
• Torsion
2/26/2018
Assis.Prof.Dr.Radhwan H. Hasan
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lec 2Principles and essential of RPD design

2/26/2018

Assis.Prof.Dr.Radhwan H. Hasan
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• Biomechanics and Types of RPD

• Most common mechanical forces at play:
• Lever principle (all Kennedy Class I and II cases)
• Inclined principle (all rest and retainers)
• Wheel and axle principle (rotation)

• Tooth supported- (all Kennedy Class III dentures)
• Tissue supported (Kennedy Class I & II dentures)
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Assis.Prof.Dr.Radhwan H. Hasan
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• Wheel & Axle Principle

• Lever and Fulcrum Principle
• Inclined plane principle
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Assis.Prof.Dr.Radhwan H. Hasan
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Possible movements of partial denture.
Tooth –tissue supported partial
denture:

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Assis.Prof.Dr.Radhwan H. Hasan
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Tooth supported partial denture:

Movement :
Toward tissues resisted by rest on abutment teeth
Away from tissue resisted by retentive clasp arm
Horizontal movement resisted by stabilizing components

Rotation relatively non existent

Assis.Prof.Dr.Radhwan H. Hasan
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Assis.Prof.Dr.Radhwan H. Hasan
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Assis.Prof.Dr.Radhwan H. Hasan
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• I-bar system (RPI system)

• Modified type of roach clasp designed to reduce tooth contact
• R –Rest P -Proximal plate I -I-bar clasp.

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• I-bar system (RPI system)

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Assis.Prof.Dr.Radhwan H. Hasan
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• I-bar system (RPI system)

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Assis.Prof.Dr.Radhwan H. Hasan
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Assis.Prof.Dr.Radhwan H. Hasan
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N.B.:

The cingulum Rest is preferable to an incisal Rest ??
because:
• - placed closer to the center of rotation of the abutment, thus reducing its tendency to tipping
• - More esthetic .
• - Less bothersome to tongue .
•