Lec 2: Biomechanics Flashcards

1
Q

Application of mechanical principles on biological tissues while studying the biology from a functional viewpoint and then using these principles to design a stable prosthesis.

A

Biomechanics

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2
Q

Types of stress acting on an rpd

A
  1. Vertical
    a) Displacing Force
    b) Dislodging Force
  2. Horizontal
  3. Torsion
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3
Q

The RPD and their associated structures are subjected to various forms of stress. Their ability to resist them depend on:

A

1) Direction, duration, magnitude and frequency of the stress (force) being applied onto the denture and denture bearing areas.

(2) Capacity of these areas to resist these forces / stress.

(3) Changes due to resistance over time.

(4) The type of resistance generated:
a) Tooth based
b) Tooth and Tissue based

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4
Q

Contributes mainly to resisting Horizontal Stress (direct retainers).

A

Tooth based resistance

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5
Q

Contributes to resisting Vertical Stress and Torsion (major connectors and indirect retainers).

A

Tooth-tissue based resistance

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6
Q

Factors contributing to the amount of stress on the rpd

A
  1. The Length of Edentulous Span (example: Kennedy Classification III usually exhibit no lever action).
  2. Quality of Ridge Support (example: Wider ridges disperse more stress due to the Snow Shoe Principle).
  3. Quality of Oral Mucosa (example: Healthy mucosa are able to withstand much greater force than weak flabby mucosa).
  4. Clasp Design (flexibility, length and material used).
  5. Occlusal Harmony
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7
Q

6 principles of mechanical forces

A

lever
wedge
inclined plane
screw
pulley
wheel and axle

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8
Q

3 mechanical force principles considered within oral cavity

A
  1. lever
  2. inclined plane
  3. wheel and axle (rotation)
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9
Q
  • In cantilever type of Removable Partial Denture, where there is Distal Extension.
  • If there is bone resorption of the residual alveolar ridge under the distal extension
A

First order lever action

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10
Q
  • Usually seen in the tooth supported RPD.
  • Upon consuming sticky food, the food exerts pulling effort on the prosthetic teeth while the natural teeth and retainers exert counteracting forces from both sides.
A

Third order lever action

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11
Q
  • Seen wherein the rest will “slip off’ the rest seat.
  • However, flattening the rest seat will aid in the retention of the direct retainer on the tooth surface and resist horizontal forces.
A

Inclined plane principle

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12
Q

The partial denture can rotate along 3 planes? and alone 3 axes?

A

planes:
sagittal
frontal
horizontal

axes:
sagittal
vertical
horizontal

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13
Q

The basis of the principle is to distribute stress/forces onto as large an area as possible in order to counteract the stresses applied to a partial denture.

A

Snow show principle

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14
Q

In order to overcome the forces acting against the RPD, the prosthesis must take full advantage of all the primary and secondary stress bearing areas.

Ex. Buccal shelf area are the primary stress bearing areas in the mandible because of their position on the occlusal plane. Not extending the denture to the shelf area will result in displacing forces and horizontal forces during mastication.

A

Snow shoe principle

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