Direct Retainers (Part I) Flashcards
RPD retention resists::
Dislodging forces
Mechanical retention from retaining elements on abutment teeth:
Primary retention
Retention due to the intimate contact of minor connector with guid planes:
Secondary retention
Retention due to the intimate contact of denture base & maxillary major connector with underlying tissues:
Secondary retention
RPD component used to retain and prevent dislodgment:
Direct retainer
What are the two types of direct retainers?
- Intracoronal
- Extracoronal
Type of direct retainer characterized by internal precision attachment (key/keyway):
Intracoronal
What type of direct retainer is considered the most esthetic?
Intracoronal
What are the disadvantages to an intracoronal direct retainer?
Requires crown, complex fabrication & high maintenance
What type of direct retainer is more commonly used?
Extracoronal
Type of direct retainer characterized by a clasp assembly:
Extracoronal
What are two types of clasps?
- Suprabulge
- Infrabulge
Type of clasp in which the retentive arm approaches undercut from above the survey line:
Suprabulge
Suprabulge clasps may also be referred to as:
Circumferential, Akers, circlet
Type od clasp in which the retentive arm approaches undercut from below survey line:
Infrabulge
An infrabulge clasp may also be referred to as:
Bar clasps
What type of direct retainer is seen in the following image?
Intracoronal
What type of direct retainer is seen in the following image?
Extracoronal
What type of clasp is seen in the following image?
Suprabulge
What type of clasp is seen in the following images?
Infrabulge
Label the following components of the supra-gingival clasp assembly:
(Top to bottom)
Rest
Reciprocal clasp
Retentive clasp
Proximal plate
Label the types of clasps seen in the following image:
A) Suprabulge clasp
B) Infrabulge clasp
A properly constructed suprabulge or infrabulge clasp assembly must incorporate the following components: (4)
- a rest
- a retentive clasp
- a reciprocal element
- one or more minor connectors
Label the following parts of the clasp assembly:
A) Retentive clasp arm
B) Rest
C) Minor connector
D) Reciprocal arm
Label the following components:
A) Direct retainer
B) Rest
C) Reciprocal arm
D) Direct retainer
E) Reciprocal plate
Component of the clasp assembly that lies on occlusal, lingual or incisal surface and functions to precent tissueward movement of clasp:
Rest
What is the function the rest component of a clasp assembly?
Prevent tissueward movement of clasp
Label each type of rest seen in the following image:
(Left to right)
Occlusal rest, Cingulum chevron rest, lingual ball rest, incisal rest
Where might the rest component of a clasp assembly lies on?
- Occlusal surface
- Lingual surface
- Incisal surface
Rigid component of a clasp assembly that is above the heigh of contour:
Reciprocal components
Reciprocal components of the clasp assembly include:
- Reciprocal clasp
- Lingual plate
- Proximal plate
- Guide plate
(minor connectors)
What clasp assembly component is seen in the following image?
Reciprocal components
Clasp assembly component characterized by the rigid portion, above the height of contour; proximal 2/3:
Retentive clasp arm
Clasp assembly component characterized by the flexible portion, below the height of contour; distal 1/3; provides direct retention:
Retentive terminal
What is the function of the retentive terminal?
Provides direct retention
Clasp assembly component that is described as rigid, and functions to join the body of clasp to the framework:
Minor connector
The arrow in the following image is pointing to the:
Minor connector
Clasp assembly component that is a component of a bar clasp that connects the clasp to the framework and is described as the flexible minor connector:
Approach arm
What clasp assembly component is seen in the following image?
Approach arm
List the six clasp assembly components:
- Rests
- Reciprocal components
- Retentive clasp arm
- Retentive terminal
- Minor connector
- Approach arm
What are the six requirements of a clasp assembly?
- Support
- Stability
- Encirclement of more than 180 degrees
- Reciprocation
- Passivity
- Retention
What do we mean when we say “support” is a requirement of a clasp assembly?
What component provides this?
Resists vertical movement toward tissue; rests
What do we mean when we say “stability” is a requirement of a clasp assembly?
What component provides this?
Resists horizontal displacement; all areas above the survey line & all rigid components of direct retainer
What do we mean when we say “Encirclement of more than 180 degrees” is a requirement of a clasp assembly?
Describe?
Prevents tooth from moving away from the clasp; may be continuous or broken; minimum of 3 points used
What requirement of clasp assembly is represented in the following image?
Encirclement of more than 180 degrees
What requirement of clasp assembly is NOT met in the following image?
Encirclement of more than 180 degrees
When discussing the “reciprocation” requirement of clasp assembly, the reciprocal component must contact tooth at:
Same time or sooner than retentive clasp
When discussing the “reciprocation” requirement of clasp assembly, the reciprocal component must remain in contact while:
Retentive tip passes over height of contour
When discussing the “reciprocation” requirement of clasp assembly, the reciprocal component must resist:
Retentive tip lateral forces
When discussing the “reciprocation” requirement of clasp assembly, this requires ______ to pathogenicity of insertion
Parallel surface
In the following image, the red arrow is pointing at:
Reciprocal clasp
What do we mean when we say “Passivity” is a requirement of a clasp assembly?
Components of direct retainer exert no force when fully seated
What do we mean when we say “Retention” is a requirement of a clasp assembly?
Resists displacement of RPD away from supporting tissues
What area of the clasp assembly serves to satisfy the “retention” requirement of the clasp assembly?
Area below the survey line; ideally in the gingival 1/3
Where does the clasp arm tip need to be in order to satisfy the “retention” requirement of clasp assembly?
Terminal 1/3 below survery line
