6. RPD Retainers Flashcards
1
Q
What is an RPD retainer?
A
- Any type of device used for stabilization or retnetion of a prosthesis
- Keep the RPD in place at rest and during fucntion
2
Q
Primary retention is provided by?
A
direct retainers
3
Q
Secondary retention is prvided by? What is secondary retention?
A
- Provided by major connectors and bases
- Adhesion
- Cohesion
- Border seal
4
Q
Objective of retainers? (4)
A
- Retention
- Horizontal Stabilization
- Support
- Reciprocation
5
Q
Retainers: Where is horizontal stabilization? (2)
A
antero-posteriorly: proximal plates
laterally: reciprocal arm
6
Q
Retainers: How do we achieve support?
A
Occlusal rest
7
Q
Retainers: what is reciprocation and how is it achieved? (2)
A
- Counterbalance of lateral forces during insertion
- Reciprocal arm
8
Q
What are the different types of retainers? (2)
A
- Direct
- Indirect
9
Q
Characteristics of direct retainers? (2)
A
- Retain at the very place where they are
- Oppose to all movements
10
Q
What are the types of retention mechanism for direct retainers? (2)
A
- Clasp
- Frictional
11
Q
Characteristics of indirect retainers? (3)
A
- Passive
- Oppose to rotation around fulcrum line
- At a distance where they are
12
Q
What do circumferential retainers consist of? (2)
A
- Minor connector (rigid)
- Retentive system
- Body of the retainer
13
Q
What does the retentive system of the circumferential retainer consist of? (4)
A
- Occlusal rest
- Body
- Reciprocal arm
- Retentive arm
14
Q
Circumferential retainers: Body of the retainer ?
A
Body of retainer joins many elements
15
Q
Circumferential retainers: Body of the retainer functions? (3)
A
- Stabilization
- Connection
- Guide the path of insertion
16
Q
Circumferential retainers: Body of the retainer connection function? (2)
A
- Arms (clasps) and occlusal rest
- Extension of the minor connector
17
Q
Bar/contact point retainers: What does the proximal plate act as?
A
Acts as the reciprocal arm and body of the retainer at the same time
18
Q
Bar/contact point retainers: What does the proximal plate do? (5)
A
- Limits and guides the insertion and removal path of the denture
- improves stability
- friction retention
- reciprocation
- reduces embrasures
19
Q
Where is the occlusal rest placed?
A
- At occlusal surface of the tooth
- Over marginal ridges and fossae
20
Q
Where is the occlusal rest put when they limit bounded edentulous space?
A
Occlusal rest must be near the space
21
Q
Where is the occlusal rest put when they limit free-ended edentulous areas?
A
Occlusal rest must be far from the space
22
Q
Occlusal rest must be _____ to comply with its functions
A
Rigid
23
Q
Functions of the occlusal rest? (3)
A
- Support
- Prevention of tooth movements
- Help keep VD and occlusion
24
Q
How does the occlusal rest help with support?
A
Prevents denture from embedding into the soft tissues
25
What movements does the occlusal rest help to prevent? (3)
- Rotations
- Migrations
- Inclinations
26
What should be the shape of the occlusal rest? (2)
- Rounded and slightly triangular
- Spoon shape
- Same width and length
27
Describe the thickness of the occlusal rest
Adequate thickness: importance of the articulator
28
What should the width of the occlusal rest be?
of 1/2 to 1/3 of the distance between cusps
29
Angle between body-minor connector and occlusal rest must be... (2)
Less than 90 degrees
| coaxility of forces
30
If the occlusal rest is made at the anterior teeth then... (2)
- Its better to have it at the canines than at the incisors
| - Better if they rest over the cingulum than the incisal edge
31
Circumferential retainers provide? (3)
- Retention
- Reciprocation
- Stabilization
32
Circumferential retainers clasp arms? (2)
- Retentive clasp arm
| - Reciprocal clasp arm
33
Retentive clasp arms: What determines the amount of retention? (3)
- Cervical convergence angle
- How deep the retentive arm goes below the undercut area
- Flexibility of the retentive arm
34
Retentive clasp arms: Cervical convergence angle? (3)
- Path in insertion
- Shape of the tooth
- Survey line
35
How deep the retentive clasp arms goes below the undercut area: undercut gauges? (3)
- Measure the horizontal depth of the undercut
- Rest over the survey line and at a point below it
- Gauges of 0.25, 0.5 and 0.75
36
Retentive clasp arms: how deep the retentive arm goes below the undercut area is influenced by?
The cervical convergence angle
37
What does length of the retentive clasp arms do to flexibility?
Length of arm increases flexibility
38
What does the diameter of the retentive clasp arms do to flexibility?
Smaller diameter = more flexibility
39
What does shape of the section of the retentive clasp arms do to flexibility?
Circular section = more flexibility
40
What does the manufacturing technique of the retentive clasp arms do to flexibility? (2)
- Wrought wire = more flexibility
| - Cast
41
Where are the reciprocal clasp arms located?
Over the survey line
42
The reciprocal arms counterbalance...
forces made by retentive arms when crossing the survey line
43
Reciprocal arms require a flat surface parallel to...
the path of insertion
44
Design principle of circumferential retainers: encirclement?
- more than 180 degrees
| - ideally 3/4 = 270 degrees
45
First 4 design principles of circumferential retainers?
1. encirclement
2. occlusal rest for support
3. rigid reciprocal arm over survey line
4. same amount of retention for all abutment teeth
46
5-8th design principles of circumferential retainers?
5. minimum efficient possibile retention: 0.25mm
6. all the retentive arms through lingual or buccal surfaces
7. Passivity
8. Tapered retentive arm
47
Circumferential retainers: Why are the retentive arms through lingual or buccal surfaces?
To prevent torsion
48
How does a circumferential retainer display passivity?
Retentive portion of retentive arm must be inactive after placement
49
How is the circumferential retainer arm tapered?
Only last third is under the survey line
50
9 th and 10th design principles for circumferential retainers?
9. Tip ends at line angles not at the center of the surface
| 10. At a minimum of 2mm of the gingival margin
51
Another name for Akers clasp? (2)
- E clasp
| - Ney's n.1 clasp
52
Akers clasp arms?
- Come up from the body of the retainer
| - final 1/3 of the arm is more flexible
53
Akers clasp has a ________ section
half-pipe
54
Main indication of akers clasp?
Bounded edentulous areas
55
Ackers clasp advantages? (4)
- Embrace whole perimeter of tooth
- Stability
- Force spread
- Reciprocation
56
Ackers clasp disadvantages? (2)
- Inability to avoid deep undercuts
| - not aesthetic at anterior teeth
57
Why can't an ackers clasp avoid deep undercuts?
Because its only flexible at the final 1/3 of the retentive arm
58
What is another names for the reverse ackers clasp?
Reverse E clasp
59
Whats the difference between an akers clasp and reverse akers clasp?
Same retainer as an akers but it faces the edentulous area
60
What is another name for a bonwill clasp? (2)
- Double akers clasp
| - Embrasure clasp
61
When do we use a buch and carmona clasp? (2)
- Reduces food retention
| - Used over a modified crown
62
What is another name for a C clasp? (2)
- Hair pin clasp
| - Reverse action clasp
63
When do we use a C clasp? (2)
when an undercut area is next to:
- The minor connector
- The occlusal rest
64
What do we use a single continuous arm clasp for?
Dont know
65
When do we use the nally-martinet clasp?
in free ended edentulous areas
66
What do we use the back action clasp for?
For posterior isolated teeth
67
What do we use a ring clasp for?
For posterior isolated teeth
68
What do we use multiple clasp for?
Dont know
69
What are the types of bar clasa?
- Roach clasps
- RPI
- RPA
70
What are the types of roach clasps? (4)
- I-bar
- Y-bar
- T-bar
- Modified T-bar
71
What do roach clasps have? (3)
- Occlusal rests
- Reciprocal arms
* just like circumferential retainers
72
What are bar clasps called?
Infrabulge clasps
73
Why are bar clasps called infrabulge clasps?
Because their retentive arm comes up from below height of contour (survey line)
74
Indications for bar clasps?
Adjacent to edentulous area
75
How do roach clasps achieve their great flexibility? (2)
- Circular section
| - Long retentive arm
76
Roach clasps in comparison to circumferential clasps? (3)
- Less support
- Less stability
- Less encirclement
77
Roach clasps and undercut areas?
They can reach deeply undercut areas
78
Roach clasps and forces?
transmit milder forces due to the flexibility
79
Where does the I-bar clasp contact the tooth?
Contacts tooth at only one single point
80
Difference with all the bar clasps?
Ask
81
What does RPI stand for?
- Rest
- Proximal plate
- I-bar clasp
82
How far away should the RPI from the soft tissues?
3-6mm
83
What is the advantage of the RPI? (2)
- More esthetic
| - Minimum tooth and gingival contact
84
What is the disadvantage of an RPI?
Less encirclement
85
What are the contraindications of the RPI? (4)
- Shallow vestibule
- Frenulum
- Tooth greatly inclined buccaly
- Tissue undercuts
86
What does RPA stand for?
- Rest
- Proximal plate
- Akers clasp
87
When do we use an RPA? (5)
when the RPI is contraindicated:
- Shallow vestibule
- Frenulum
- Tooth greatly inclined buccaly
- Tissue undercuts
88
Where is the fulcrum line in free-ended biomechanics?
At the most posterior occlusal rests
89
What happens with everything behind the fulcrum line?
Will move towards the tissues
90
What happens with everything in front of the fulcrum line?
will tend to separate from teeth
91
What is a wrought wire clasp? (4)
- Not cast retainers
- Prefabricated
- great elasticity
- Acceptable retention and reciprocation
92
Wrought wire clasp indication? (2)
- Tissue supported RPD
| - Bad periodontal support of remaining teeth
93
What is a frictional retainer?
- The closely fitting fiting part (female matrix) is usually within the normal or expanded contours of the crown of the abutment tooth
- Metal receptacle (male PATRIX) is attached to a pontic or denture framework
94
What are frictional retainers more commonly known as?
Attachments
95
Frictional retainers are used for...? (3)
Combined prostheses:
- Fixed partial denture
- RPD
96
What is an indirect retainer?
Assists the direct retainer in preventing displacement of the distal extension denture base by functioning through level action on the opposite side of the fulcurm line when the denture base moves away from the tissues in pure rotation around the fulcrum line
97
What does an indirect retainer do in free-ended RPDs?
Prevents rotation around fulcrum line
98
An indirect retainer is more effective...
Farther away from fulcrum line
99
What type of RPD do we use an indirect retainer for?
Tooth-tissue supported
100
Where is the best place to put an indirect retainer?
- Better at a premolar than at a canine
| - Better at a canine than at an incisor
101
How are indirect retainers classified? (2)
- Rests
| - Major connector
102
How are indirect retainers classified by rests? (2)
- Occlusal rests
| - Incisal rests
103
How are indirect retainers classified by major connector?
- Any maxillary MC forward of fulcrum line
| - Lingual plates and double lingual bars
104
If an indirect retainer has to be located at an incisor... (3)
- Better over the cingulum
- Rests over incisal edges are unaesthetic
- Better over several incisors
105
If a major connector is located infront of the fulcrum line...
They act as an indirect retainer
106
If there is an upper diastema the major connector ends at...
the palatal rugae
107
Along with lower major connectors, these also operate as indirect retainers...
What do they need? (3)
- Lingual plate
- Double lingual bar
*Need cingular rest seats
108
Indirect retainer effectiveness? (2)
- Good seats - axial forces
| - Maximum distance from fulcrum line
109
Indirect retainers function? (3)
- Prevent movements of free-ended bases
- Reduce oblique forces over abutment teeth
- Should be passive at rest and active at function
