Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

partial removable > biomechanics of design > Flashcards

biomechanics of design Flashcards

1
Q

Biomechanics
*def?
* RPD implication?

A
  • Application of mechanical engineering
    principles in the living organism
  • Mechanical forces exerted on RPD during functional & parafunctional mandibular movements should be properly directed to the supporting tissue to elicit the most favorable response.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

RPD Supporting Structures

A

alveolar bone
teeth/PDL
mucosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q
  • Alveolar bone provides support via:
A

– Abutment teeth & periodontal ligaments
– Residual ridges through soft tissue covering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q
  • Teeth better able to tolerate vertical forces:
A

down long-axis
– More PDL fibers activated
to resist force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q
  • Deleterious forces on teeth:
A

– off-axis, torque, horizontal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Excess force on alveolar support may result in:

A

– Mucosal ulcerations
– Bone resorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Forces Acting on RPD

A
  • Vertical (Dislodging)
  • Horizontal (Lateral)
  • Vertical (Seating)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what forces do these resist?

Requirements of RPD

A
  • Retention:
    –Resistance to dislodging (vertical)
  • Stability:
    –Resistance to horizontal forces
  • Support:
    –Resistance to vertical seating (vertical)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q
  • Retention
A

Resistance to Vertical
dislodging forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q
  • RPD components involved with retention
A

– Direct retainer: Retentive clasp
– Indirect retainer
– Proximal plates (Friction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q
  • Stability:
A
  • Stability: Resistance to horizontal, lateral,
    or torsional forces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q
  • RPD components involved with stability
A

– Minor connectors
– Proximal plates
– Lingual plates
– Denture bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

importance?

  • Support:
A
  • Support: Resistance to vertical seating force and this is most important to oral health.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

RPD components involved with support

A

– Rests
– Major connectors: Maxillary tooth-tissue supported RPD
– Denture bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Reciprocation:

A
  • Reciprocation: is the means by which one part of a restoration is made to counter the effects created by another part.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
  • RPD’s true reciprocation can only be achieved how?
A
  • RPD’s true reciprocation can only be achieved if the reciprocating element touches the tooth before the retentive clasp.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q
  • Tooth-supported RPD
A

– Abutment teeth support RPD
– Class III & IV RPD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q
  • Tooth-tissue supported RPD
A

– Denture base is supported
by both teeth & residual ridge
– Class I, II, long-span IV RPDs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q
  • Class III RPDs best resist _______ forces
A
  • Class III RPDs best resist functional force
20
Q

where are rests?

occlusal loading of class 3 cases

A
  • With occlusal loading, vertical seating forcesdirected down tooth long axis
    – Occlusal rests adjacent to edentulous area
21
Q

counteracted with?

vertical dislodgement of class 3

A

*Limited vertical dislodgement
–Counteract through retentive clasp & proximal plates

22
Q

horizontal forces of class 3

A

*Limited horizontal forces on Class III RPD

23
Q
  • Class I, II, & long-span IV RPDs
    –Subject to greater?
    –support from?
    –rotational movement?
A
  • Class I, II, & long-span IV RPDs
    –Subject to greater stress
    –Combination of tooth & soft tissue
    support
    –RPD extension movement permits
    rotational movement around fulcrums in
    3 planes
24
Q

Rotation in Sagittal Plane around
Horizontal Plane Fulcrum

A
  • Fulcrum through rests closest to
    edentulous areas
  • Inferior-superior denture base
    movement of the distal end
  • Occurs with:
    – Vertical seating force
    – Vertical dislodgement
    force
25
Q

components involved?

Resistance to Rotation Around
Horizontal Fulcrum

A

done with retention (Direct retainer, Indirect retainer, Proximal plates) and support (Rests, Major connector (Maxillary), Denture base)

26
Q

Rotation in Vertical Plane through
Longitudinal/Sagittal Fulcrum

A
  • Fulcrum through crest of ridge
  • Rocking or side-to-side movement over the crest of the ridge
27
Q

components involved?

Resistance to Rotation Around
Longitudinal Fulcrum

A
  • Stability: resistance to rotation around
    ridge crest
    –RPD components involved: Rigid connectors, Clasps, Denture base
28
Q

Rotation in Horizontal Plane through
Vertical Fulcrum

A
  • Fulcrum at center of dental arch
  • Horizontal twisting results in buccolingual movement of RPD
29
Q

involved components?

Resistance to Rotation Around
Vertical Fulcrum

A
  • Stability: resistance to horizontal
    movement
    –RPD components involved
  • Minor connectors, Proximal plates, Rigid portions of clasps, Lingual plates, Denture base
30
Q

Extension RPD Rotation through
Horizontal Fulcrum: RPD functions as a _______
* Can result in? why?

A
  • RPD functions as a lever
  • Can result in deleterious effects on
    teeth–Magnified loading forces
31
Q

what lever classes do we see with RPDs

A

1 and 2, 2 is more desireable/ less destructive
usually not a factor with tooth supported RPDs

32
Q

Effect of Rest/Retentive Clasp Positions on lever action

A
  • Class I lever occurs during rotation around horizontal fulcrum line through terminal rests. (Rotation toward ridge)
  • Retentive clasp should NOT be anterior to terminal rest fulcrum line.
    – Detrimental torquing forces applied to
    abutment.
33
Q
  • Distal rest/Distal Guide Plate/Distal extension RPD:
A

NO GOOD CLASS I LEVER
– Circumferential clasp tip anterior to rest/ fulcrum.
– Circumferential clasp moves occlusally during function.
– Directs detrimental distal torquing force to abutment

34
Q
  • Mesial rest/Distal Guide Plate/Distal extension RPD:
A

CLASS II LEVER, BETTER
– Circumferential clasp tip slightly posterior to rest/fulcrum.
– Circumferential clasp moves more mesially during function.
– Clasp tip tends to move into deeper undercut
* Produces less leverage on abutment than with distal rest.

35
Q

SOLUTIONS?

Class II arch with posterior modification space.

A

Class I Lever occurs when abutment with retentive clasp anterior to horizontal fulcrum line/axis of rotation (AR) in
During RPD rotation toward ridge,
anterior clasp produces detrimental
torquing force on this abutment.

solutions:
1. No clasp
2. Clasp in less undercut
3. Non-retentive clasp (tip not in undercut)
4. Wrought wire clasp

36
Q

potentila disadvantages

without indirect retention what occurs

A
  • NO Indirect retention
    – Class I Lever occurs with Vertical dislodgement forces. (Rotation at horizontal fulcrum)

– Disadvantages
* Allows greater vertical dislodgement to occur.
* Potential for tissue impingement under mandibular major connector.

37
Q

advantages

Indirect Retainer present

A

– Class II Lever occurs with Limited Vertical
dislodgement

– Advantages
* Vertical dislodgement limited
* Potential for tissue impingement by major connector reduced

38
Q
  • Class III RPD
    –fulcrums or levers?
    – Design by?
A

– No fulcrums or levers
– Design by convenience

39
Q
  • Class I, II & long-span IV RPDs (Extension RPDs)
    – Consideration of?
    – Potential Levers?
A

– Consideration of rotation toward & away from residual ridge at Horizontal fulcrum
– Potential Class I & II Levers

40
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth

A
  1. Length of extension span
  2. Quality of Support Ridge
  3. Flexural qualities of clasp
  4. Clasp design
  5. Abutment tooth surface
  6. Occlusal Harmony
41
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth
1. Length of extension span

A

– Correlates to length of lever effort arm

42
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth: quality of ridge support

A

– Broad ridge better support than thin, knife-edge ridge
* Better resistance to both vertical & horizontal force

43
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth
3. Flexural qualities of clasp

A

– More flexible, less stress transmitted to abutments
– More flexible, less horizontal stability
– More flexible, more stress transmitted to residual ridge

– Flexural qualities determined by:
* Clasp length & diameter
* Clasp material

44
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth
4. Clasp design

A

– Clasp passive when completely seated
– Reciprocal arm contacts tooth before
retentive tip passes height of contour
* Neutralize stress from retentive tip

45
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth
5. Abutment tooth surface

A

– Gold greater frictional resistance to clasp arm movement than enamel
* Greater stress on gold restored tooth

46
Q

Factors Influencing Magnitude of Stress
Transmitted to Abutment Teeth: occlusal harmony

A

– A disharmonious occlusion may generate horizontal forces
– When magnified by the factor of RPD leverage, these forces may be destructive to abutment teeth & residual ridges

47
Q

Stress Control by RPD Design

A

Forces exerted through RPD can be widely distributed, directed, & minimized by the selection, the design, & the location of the RPD components, in conjunction with the development of harmonious occlusion.

partial removable (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions