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The greatest benefit of implants on movement of partial denture is:
- improving stability (by providing support)
- eg minimizing rotation in Kennedy Cl. I,II
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Among 6 simple mechanics, what are 3 simple mechanic that should be avoid in RPD design?
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3 classes of lever:
- First Class: R F E (F is between R and E)
- Second Class: F R E (F near R)
- Third Class: F E R (F near E)
- F = fulcrum (rest)
- R = resistance (retentive arm)
- E = effort (denture base)
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Movement of deunture around a fulcrum line is resisted by: (3+2)
- For vertical tiss. ward movement:
- 1. Supporting tissue
- 2. Fit of denture base
- 3. Occlusal load
- For the movement away from tissue:
- 1. Retentive clasp on terminal abutment
- 2. Indirect retainer (minor connector and other vertical support elements of framework)
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The rotation about longitudinal axis will be primarily resisted by:
rigidity of major and minor connector.
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The roatation about imaginary vertical axis will be resisted by: (2)
- Reciprocal arm
- Minor connectors that contact vertical tooth surface
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Which Kennedy Class does experience only horizontal movement?
- Class III with sufficient abutment
- The horizontal movement will be resisted by stabilizing components.
Remember: Class I, II, extensive III, extensive IV will experience all 3 movements!
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RPI, RPA and Bar clasp are designed to accommodate fumctonal prosthesis movement. What is the class of movement being concerned? And which parts of the denture act as “effort arm”, “fulcrum”, and “resistance arm”?
- Class I lever
- effort arm: distal extension
- fulcrum: distal rest
- resistance arm: clasp tip (engaging tooth undercut)
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