Lec 3: Components Flashcards
Resistance to removal from the tissues or
teeth.
Retention
Resistance to movement in a horizontal
direction (anterior-posteriorly or mesio- laterally.
Stability
Resistance to movement towards the
tissues or teeth.
Support
- The unit of a removable partial denture that connects the parts of one side of the dental arch to those of the other side.
- Its principal functions are to provide unification and rigidity to the denture.
Major connector
- A unit of a partial denture that provides retention against dislodging forces.
- Commonly called
a ‘clasp’ or ‘clasp unit’ and is composed of four elements, a rest, a retentive arm, a reciprocal arm and a minor connector.
Direct retainer
- A unit of a partial denture that connects other components (i.e. direct retainer, indirect retainer, denture base, etc.) to the major connector.
- The principle functions of minor connectors are to provide unification and rigidity to the denture.
Minor connector
4 components of a clasp unit?
retentive arm
reciprocal arm
rest
minor connector
A unit of a Class I or II partial denture that
prevents or resists movement or rotation of the base(s) away from the residual ridge.
Indirect retainer
The indirect retainer is usually composed
of one component, which is the?
Rest
- The unit of the denture that rests on the foundation tissues and to which prosthetics teeth are attached.
- Attaches the prosthetic teeth to the denture base retention minor connector which attaches the base to the major connector.
Denture base
- Are artificial teeth used on a denture to substitute for natural teeth.
- By substituting for missing natural teeth, it provide esthetics and masticatory functions.
Prosthetic teeth
A major connector unites all other
components of a partial denture so that the partial denture acts as one unit.
Unification
– By unifying all elements of a partial
denture the major connector can distribute functional loads to all abutment teeth, so that no one abutment is subjected to extreme loading.
– Unification of the direct retainers with the denture bases aids in distributing forces between both the teeth and the mucosa.
Stress distribution
- By uniting one side of the arch to the other bracing elements on one side of the arch can aid in providing stability to the other.
- This can aid in dissipating twisting and torqueing forces.
Cross-arch stabilization (counterleverage)
– Necessary to ensure that the partial denture functions as one unit.
– If the denture flexes, stress distribution and cross arch stabilization can be compromised since different portions of the denture can move independent of the others.
Rigidity
Major connectors should not enter into undercut areas unless tissue impingement can be avoided by changing the selected path of insertion or by using minor undercut blockout.
Non-interference with soft tissues
This can be minimized by locating the margins of the connectors at the prescribed distance from the free gingival margin and by taking care that the presence of minor connectors, clasp arms and major connectors does not create “traps” or large concavities where food can collect.
Food impaction
– The margins of the major connector should have a smooth transition from connector to tissue so as to minimize the obtrusiveness.
– All line angles and edges should be smooth and rounded.
– Borders should not be placed in locations where they might interfere with speech.
– Bulk should be reduced enough so as not to interfere with speech or appearance, yet thick enough to ensure rigidity.
Unobtrusive
This is the most commonly used mandibular major connector.
It should be used whenever possible unless there are advantages that can be obtained from another major connector.
Lingual bar
Lingual bar:
Shape:
– ___ on tissue side
– convex or ____ on tongue side
– 1/2 pear shape, with thin edge toward teeth
Size:
– occluso-gingival width = ?
– thickness = ?
Position:
– The inferior border should be as low as the ________ and tissue reflections of the floor of the mouth will permit, as determined by observing functional movements of the tongue.
– The superior border should be
at least _____ below the free gingival margin. For hygienic reasons the superior border should still be kept as far from
the gingival margin as possible.
shape:
flat = tissue
tear-drop = tongue
1/2 pear shape
size:
occlusogingival = 4mm
thickness = 1.5-2mm
position:
inferior border = low as lingual frenum
superior border = 3mm below FGM
- Consists of a lingual bar plus an extension over the cingulum of anterior teeth.
- This mandibular major connector should only be
considered in those rare instances where a lingual bar cannot be used. - Occurs when there is a high floor of
the mouth, a prominent lingual frenum or lingual tori that would be impinged upon by a lingual bar, if it was made with adequate height and distance from the free gingival margin. - Also advocated for extensive distal extension cases with severe vertical resorption of ridges (i.e. little resistance to horizontal rotational tendencies).
Lingual plate
- Must be prepared at each end of the anterior segments of the lingual plate.
- This prevents excessive forces being directed facially by movements of the distal extension base.
Vertical stop/rest area
- The connector consists of a lingual bar plus a secondary bar resting above the cingulum of the anterior teeth.
- The secondary bar supposedly acts as an indirect retainer and performs a role in the horizontal stabilization of periodontally-involved teeth.
- The performance of these functions is questionable. Additionally, this major connector can create a food trap between the two bars.
- The use of this type of connector is not encouraged.
Continuous bar retainer / Kennedy bar / Double lingual bar
Major connectors in the upper arch should terminate ________ or more from the gingival crest tissues.
6 mm