69 - REMOVABLE PARTIAL DENTURES - ELEMENTS

sections

• what is rpd

• elements of rpd

• what are the mandibular major connectors

• what are maxillary major connectors

• characteristics of major connectors

• what are minor connectors

• retainer, direct retainer

• attachment

• clasp assembly

• clasp, retentive/reciprocal clasp arm, occlusal rest

• rest seat

• occlusal rest arm

• indirect retention

• denture base

• what is rpd

any prosthesis teeth that replaces some teeth in a partially dentate arch. It can be removed from the mouth and replaced at will, also called dental partial prosthesis.

• elements of rpd

Elements of RPDs:

• Major connector

• Minor connector

• Direct retainer

• Indirect retainer (class I and II RPDs only)

• Replaced teeth

• Base

• what are the mandibular major connectors

• Major connector: part of partial removable dental prosthesis that joins components on one side of the arch to those on the opposite side

• Lingual bar— six gauge half-pear shape approximately 4 mm in height with superior border at least 3 mm from the free gingival margins (fgm). The bar is pear shaped in cross section with the thickest part along the inferior border.

• Labial bar — form and usage are the same as the lingual bar but placed buccally (labially) due to severe lingual inclination of the remaining teeth.

• Lingual plate — used when fgm to floor of mouth is less than 7 mm or when anteriors are mobile and their longevity is questionable. Superior border is placed at the junction of incisial and middle thirds.

• what are maxillary major connectors

• Major connector: part of partial removable dental prosthesis that joins components on one side of the arch to those on the opposite side

• Complete (or modified) palatal plate:

  • Complete palatal plate: posterior border must not interrupt movable tissue.

  • Modified palatal plate: anterior border ends in valley of rugae not less than 6 mm from fgm.

  • Wide application to all classifications, but mostly to class I and II.

  • Provides maximum support as plate rests on tissue, as do all maxillary major connectors.

• Anteroposterior Palatal strap:

  • Used where torus precludes use of palatal plate, provided a minimum of 5 mm exists between the posterior aspect of the torus and the vibrating line.

• (Mid)palatal strap:

  • Used mainly in class III situations - width of strap varies to suit the clinical situation.

• Anterior Palatal strap

• characteristics of major connectors

1. Made from an alloy compatible with oral tissue.

2. Rigid and provide cross-arch stability through principle of broad distribution of stress.

3. Do not interfere and not irritating to tongue.

4. Do not substantially alter natural contour of lingual surface of mandibular alveolar ridge or palatal vault.

5. Do not impinge on oral tissue when the restoration is placed, is removed, or rotates in function.

6. Cover no more tissue than is absolutely necessary.

7. Do not contribute to retention or trapping of food particles.

8. Have support from other elements of the framework to minimize rotation tendencies in function.

9. Contribute to the support of the prosthesis.

• what are minor connectors

connecting link between major connector or base of a partial removable dental prosthesis and other units of prosthesis, such as clasp assembly, indirect retainers, occlusal rests, or cingulum rests.

main function:

• Transfers functional stress to abutment teeth.

• Transfers effects of retainers, rests, and stabilizing components throughout prosthesis.

requirements:

• Must be rigid to distribute stress between linked components

• Must not impinge on underlying mucosa; tissue relief (30ga.) Needed in the mandibular arch.

• Mucosal surface is highly polished to prevent plaque accumulation.

usage:

• Minor connector and rest junction must be at least 1.5 mm thick

• Try to place interproximal

• Joins major connector at a right angle

• Should be located at least 5 mm from other vertical components

• retainer, direct retainer

• Retainer: part that seats on the retainer (abutment) tooth.

• Direct retainer: component of a partial removable dental prosthesis used to retain and prevent dislodgment, consisting of a clasp assembly or precision attachment.

• attachment

• mechanical device for achieving fixation, retention, and stabilization of a prosthesis.

• clasp assembly

part of an RPD that acts as a direct retainer and/or stabilizer for the prosthesis by partially encompassing or contacting an abutment tooth.

Components of the clasp assembly include:

• Clasp

• Reciprocal clasp arm

• Cingulum

• Incisial or occlusal rest

• Minor connector

• clasp, retentive/reciprocal clasp arm, occlusal rest

• Clasp: component of the clasp assembly that engages a portion of tooth surface and either enters an undercut for retention or remains entirely above the height of contour to act as a reciprocating element.

• Retentive clasp arm: part of clasp assembly that enters an undercut for retention.

• Reciprocal clasp arm: component of clasp assembly specifically designed to provide reciprocation by engaging a reciprocal guiding planes. Contacts action of clasp during removal and insertion of a partial removable dental prosthesis.

• Occlusal rest: rigid extension that contacts occlusal surface of a tooth or restoration, occlusal surface of which may have been prepared to receive it. (Modifications: incisial, lingual, and cingulum rest.)

• rest seat

prepared recess in a tooth or restoration created to receive the occlusal, incisial, cingulum, or lingual rest.

• occlusal rest arm

minor connector used to attach an occlusal rest to a major part of a removable partial denture.

• indirect retention

effect achieved by one or more indirect retainers of a partial removable denture prosthesis that reduces the tendency for a denture base to move in an occlusal direction or rotate about the fulcrum line.

Assists direct retainer(s) in preventing displacement of distal extension denture base by functioning through lever action on the opposite side of fulcrum line when denture base moves away from tissues in pure rotation around fulcrum line.

• denture base

• part of a denture that rests on the foundation tissues and to which teeth are attached.

Replaced teeth:

• Functions:

  • Prevent migration of the remaining teeth

  • Restore Masticatory efficiency

  • Retain proper interarch space

  • Maintain esthetics of a normal facial contour

  • Achieve distinct enunciation

• Types of materials:

  • Acrylic (on class IV RPD, the standard type used for RPDs and CDs)

  • Porcelain (rarely used because difficult to set)

  • Metal: gold and chrome