Brainscape's Knowledge GenomeTM

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


See full index

Fixed Pros II > Biomechanics > Flashcards

Biomechanics Flashcards

1
Q

what is a simple FPD for

A

-1 or 2 missing teeth
- 2 abutments

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

what is a complex FPD for

A
  • 3 or more missing teeth
  • missing canine
  • 1,3 or greater than three abutments
  • splinted, pier, cantilever
  • non parallel abutments
  • combined anterior and posterior FPD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are most failures in FPDs are due to

A

biomechanical factors

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

what biomechanical factors cause FPD failure

A
  • caries
  • gingival inflammation
  • poor framework design
  • poor occlusion
  • material failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what problems are caused by bending and deflection

A
  • fracture of porcelain
  • connector breakage
  • retainer loosening and subsequent caries
  • unfavorable tooth or tissue response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the relationship between deflection and length of a bridge

A

the deflection is directly proportional to the cube of the length of its span

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

what is the law of beams

A

deflection = load (length)^3/ 4e (width)(height)^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the relationship between deflection and height of the bridge

A

deflection varies inversely by the cube of its height (thickness)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the types of rigid connectors

A

cast or soldered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the minimum height requirement for metal connectors

A

3-4mm x 3-4mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the minimum height x width requirement for ceramic/zirconia connectors

A

4mm x 4mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

use a bridge material with ______

A

high yield strength

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

what is yield strength

A

an indication of maximum stress that can be developed in a material without causing plastic deformation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

if concerns exist with connector strength use:

A

an adhesive cement for increased retention on abutments

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

occlusal force on pontics can cause ______ torque

A

mesial-distal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

forces at an oblique angle or outside the center of the restoration cause _____

A

F-L torque around M-D axis of rotation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

grooves/boxes ____ resistance to dislodgement

A

increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

place boxes/grooves _______ to the movement around the axis of rotation

A

perpendicular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what things help with retention and resistance in a retainer

A

wall length/ occlusal convergence / geometric resistance form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

pontics lying outside the inter abutment axis act as a _____ causing ____

A

lever arm; torque movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

how do you gain additional resistance in opposite direction from the lever arm

A

axial grooves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

where would you place axial grooves to gain the additional resistance in preps in the anterior

A

buccal and lingual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what torquing direction do bridges in the anterior move

A

out and up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what torquing movement do bridges in the posterior want to move

A

up and towards each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

is the maxillary canine or mandibular canine more favorable for a canine pontic

A

mandibular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

why are maxillary pontics not favored

A

forces inside the arch push the pontic buccally and are weak from tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

why are mandibular canine pontics favored

A

forces outside the arch act to seat the pontic and are strong from compression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

how many additional teeth can you replace if you are replacing a canine

A

none

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what should you treatment plan if you have a canine and 2 contiguous teeth

A

restore with implants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is another name for double abutments

A

splinting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what do double abutments do

A

help stabilize the prosthesis by distributing forces over more teeth but does not necessarily increase retention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what cases are double abutments good for

A

periodontally weakened teeth

33
Q

what are the criteria for secondary abutments

A

-root surface area and crown to root ratio must equal to the primary abutments
- secondary retainers must have greater than or equal to retention of primary retainers
- long crown length and adequate interproximal space for connectors

34
Q

what is a pier abutment

A

an edentulous space on both sides of a lone free standing abutment

35
Q

is the physiologic tooth movement direction and amount the same from anterior and posterior

A

no

36
Q

cause of failure in pier abutments is most often a:

A

loosened retainer

37
Q

what are the causes of a loosened retainer

A
  • prosthesis flexure creating movement of teeth
  • tensile stresses between terminal retainers and abutments; intrusion of abutments under loading
  • differences in retentive capacities between abutments relative to size
38
Q

where are stresses concentrated in pier abutments

A

around the abutment teeth and between retainers and abutment preps

39
Q

slight movement in non-rigid connectors can minimize:

A

the transfer of stress from the particularly loaded segment to the rest of the FPD

40
Q

where should a non-rigid connector be placed and why

A

on the distal side of the retainer on a middle abutment because the movement in a mesial direction will seat the key into the keyway

41
Q

why should the non-rigid connector not be placed on the mesial side of the middle abutment

A

mesially directed movement will un seat the key

42
Q

what are the main problems with pier abutments

A

loosened retainers and decay

43
Q

what are the indications for non-rigid connectors

A
  • pier abutment FPD
  • long span FPD with multiple abutments
  • non-parallel abutments- tipped molar
  • planning for failure
44
Q

what are the contraindications for non rigid connectors

A
  • long span FPD with two abutments
  • excessively mobile teeth
    -unopposed teeth
45
Q

when are non-rigid connectors used

A
  • long span FPD with multiple abutments
  • combined anterior and posterior FPDs
46
Q

what type of framework must be used in non rigid connectors

A

metal framework

47
Q

long axes of abutment teeth should converge by no more than _____

A

25-30 degrees

48
Q

tilted molar abutments are generally ____- abutments

A

poor

49
Q

how should a tilted molar abutment be prepared and what does this cause

A

mesial wall must be over-reduced/ overtapered but this decreases resistance

50
Q

what might be an issue with the distal adjacent tooth with a mesially tipped molar

A

the distal adjacent tooth may intrude on the path of insertion

51
Q

how can the distal adjacent tooth intruding on the path of insertion of a FPD insertion be corrected

A

-mesial surface may need re-contouring or restoration or extraction
- orthodontic uprighting or 3rd molar extraction

52
Q

why can occlusal reduction not always be the same as clearance needed

A

it allows for longer axial wall length because retention can be compromised with tilted molar abutments

53
Q

an FPD distributes forces favorably by:

A

directing forces in the long axis of the abutment teeth

54
Q

non-axial loading (horizontal) often leads to:

A

proximal crestal bone loss

55
Q

what does molar uprighting do

A
  • places abutment in better position for preparation
  • distributes forces under loading through long axis of tooth to help prevent/eliminate mesial bony defects
  • enables replacement of optimum occlusion
56
Q

how long does ortho take prior to bridge placement

A

1-2 years

57
Q

describe a proximal half crown

A
  • does not involve the distal wall
    -3/4 crown rotated 90 degres
58
Q

when are proximal half crowns used

A

-tilted molar abutments
- caries free distal surface
- low incidence of caries
- even marginal ridge height
- short span length

59
Q

full coverage crown compensates for:

A

discrepancy in paths of insertion

60
Q

must ______ molar to accomodate for the thickness of coping and crown

A

over-reduce

61
Q

why would you do copings and crowns

A
  • design for failure
  • protect tooth
62
Q

when are cantilevers primarily used

A

for patients contraindicated for implants

63
Q

why are cantilevers not used often

A
  • must remove tooth structure on two teeth
  • occlusal forces create guarded prognosis
64
Q

what are the criteria for cantilever

A

replace only 1 tooth and have at least 2 abutments

65
Q

what are the criteria for abutment teeth for a cantilever

A
  • long roots with good configuration
  • long clinical crown
  • resistance form for preparations occlusal-cervical height for connectors without impinging on interdental papilla
  • favorable crown: root ratio and healthy periodontium
66
Q

cantilever pontic without abutment root directs occlusal forces:

A

apically putting both vertical and lateral forces on abutments

67
Q

where is it most ideal to do cantilever and why

A

lateral incisor because it is often not in occlusion

68
Q

when replacing the lateral incisor with a cantilever what tooth should be used as the solo abutment and why

A

canine because it has a long root, esthetics are easier, occlusal forces are more lateral and therefore protect the pontic

69
Q

where can a rest be placed for a lateral incisor cantilever

A

on mesial of pontic against a rest prep in a restoration in the distal of the central incisor or slight wrap around of proximal contact

70
Q

what is necessary for the canine when it is being used as an abutment for a lateral incisor

A

good clinical crown and good orthodontic position

71
Q

what should the abutment design be for a cantilever replacement of first premolar

A
  • use full veneer retainers on the 2nd premolar and 1st molar
  • limit occlusion on the pontic
  • mesial rest used to support premolar cantilever pontic
  • either cemented or bonded
72
Q

whats the biggest problem with cantilever premolars

A

occlusion

73
Q

why can caries develop under rest seats

A

inadequate cleansability

74
Q

what is the prognosis for first molar replacement with cantilevers and why

A
  • unfavorable prognosis
  • extreme leverage forces generated by posterior position
  • occlusal forces place tensile stress on secondary retainer
75
Q

what are the criteria for first molar replacement with cantilevers if absolutely necessary

A
  • pontic size small such as a premolar
  • light occlusal contact, no excursive contact
  • pontic and connector needed maximum O-G height for rigidity
  • good crown: root ratio of abutment
  • clinical crowns - maximum preparation length and resistance form
76
Q

what is the prognosis for central incisor replacement and why

A

unfavorable
- lateral incisor abutment is a weak abutment because of root shape and occlusal forces
- severe vertical overlap because of occlusal forces
- repeated de-cementation with this case because of occlusal forces

77
Q

what are the other options to replace a maxillary central incisor

A
  • conventional bridge
  • single implant
  • RPD
78
Q
A

Fixed Pros II (13 decks)

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