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  • !

    DR. LUMA NASSRAT

    ASSISSTANT LECTURER, DEPARTMENT OF PROSTHODONTICS COLLEGE OF DENTISTRY

    TIKRIT UNIVERSITY

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    RPD LEC.8 | PROSTHODONTICS | 24-12-2018

    Minor Connectors 3RD GRADE

    LEC. 8

  • Minor Connectors

    Definition:

    • Any rigid component that links between the major connector or base of RPD

    and other components of the prosthesis.

    • Or: The portion of a PD framework that supports the clasp and the occlusal

    rest.

    Rigidity is an important characteristic of all minor connectors as it aids in force

    distribution. So, any bending or deformation will lead to concentration of forces.

    Function:

    1. Primary function is to join units of the prosthesis and denture base to the

    major connector.

    2. Transfer functional stresses to abutment teeth.

    3. Transfer the effect of the retainers, rests & stabilizing components to the

    prosthesis.

    4. Distribute stresses on the edentulous ridge to the ridge & remaining teeth.

    Types of minor connectors:

    There are four categories of minor connectors. They may be

    described as follows:

    1. Minor connectors that join clasp assemblies to major Connectors.

    2. Minor connectors that join indirect retainers or auxiliary rests to major

    connectors.

    3. Minor connectors that join denture bases to major connectors.

    4. Minor connectors that serve as approach arms for vertical projection/bar-type

    clasps.

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  • 1. Minor Connector joining Clasp Assemblies to Major Connector:

    They must be rigid, because they support the active components of the

    removable partial denture, the retentive clasps. They also support the rests,

    which prevent vertical movement of a prosthesis toward the underlying tissues.

    As a result, minor connectors must have sufficient bulk to ensure rigidity, yet

    they must be positioned so they do not irritate the oral tissues.

    Most minor connectors that support clasp assemblies are located on

    proximal surfaces of teeth adjacent to edentulous areas. These minor

    connectors should be broad buccolingually, but thin mesiodistally. The resultant

    shape makes it easier to place a prosthetic tooth in a natural position.

    In many instances, a clasp assembly must be positioned on a tooth that

    is not adjacent to an edentulous space. When this occurs, a minor connector

    should be positioned in the associated lingual embrasure. This results in a

    sufficient bulk of metal without encroaching on the tongue space. Hence, the

    minor connector may be rigid yet unobtrusive.

    A minor connector should never be positioned on the convex lingual

    surface of a tooth where its bulk will be evident.

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  • 2. Minor Connector joining Indirect Retainers or Auxiliary Rests to

    Major Connectors:

    They should form right angles with the corresponding major

    connectors, but junctions should be gently curved to prevent

    stress concentration. As previously noted, minor connectors

    should be positioned in lingual embrasures to disguise their bulk

    and promote patient comfort.

    !

    3. Minor Connector joining Denture Base to Major Connectors:

    Described as follows:

    1. Open construction.

    2. Mesh construction.

    3. Bead, wire, or nailhead components on a metal base.

    These minor connectors must be strong enough to anchor a denture base to

    the removable partial denture framework. They must be rigid enough to resist

    fracture and displacement. In addition, these components must provide

    minimal interference with the arrangement of artificial teeth.

    In the maxillary arch, a distal extension base must extend the entire length

    of the ridge and should cover the tuberosity. Consequently, the minor

    connector should be extended as far posteriorly as is practical. In many

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  • instances, the minor connector may extend beyond the most prominent portion

    of the tuberosity. In other cases, the minor connector must be terminated

    anterior to this area.

    In the mandibular arch, a distal extension base must cover the retromolar

    pad. Therefore, the minor connector should extend two-thirds the length of the

    edentulous ridge. This provides adequate support and retention for the

    associated resin base.

    1.Open Construction

    Open construction consists of longitudinal and transverse struts that form a

    ladder-like network. Placement of the longitudinal and transverse struts is a critical

    factor in prosthetic tooth arrangement.

    In the mandibular arch, one longitudinal strut should be positioned buccal to

    the crest of the ridge and the other lingual to the ridge crest. In the maxillary arch,

    one longitudinal strut should be positioned buccal to the ridge crest. The border of

    the major connector generally will act as the second longitudinal strut. Positioning of

    a longitudinal strut along the crest of the ridge must be avoided. This not only

    interferes with the placement of artificial teeth, but also predisposes the denture

    base to fracture.

    Transverse struts also must be positioned to facilitate the placement of

    artificial teeth. When there is adequate room for the placement of teeth, the number

    of cross struts is not critical. When vertical space is minimal, improperly placed struts

    may create difficulties in tooth placement. Ideally, transverse struts should be

    designed to pass between the necks of the artificial teeth. This aids in tooth

    arrangement and often results in improved esthetics.

    During the framework fabrication process, those areas of a master cast that are

    to feature open retention must be relieved using an appropriate thickness of wax.

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  • Relief provides space between the completed minor connector and the tissues of the

    residual ridge. The space permits an acrylic resin to encircle the longitudinal and

    transverse struts, thereby providing retention for the denture base.

    Open construction can be used whenever multiple teeth are to be replaced.

    Studies have shown that this form of minor connector provides the strongest

    attachment of acrylic resin to the removable partial denture framework. It also

    facilitates relining and rebasing of removable partial dentures.

    !

    2.Mesh Construction

    A mesh minor connector may be compared to a rigid metallic screen*.

    Channels that pass through the connector are intended to permit acrylic resin

    penetration. This allows resin encirclement of the minor connector and mechanical

    retention of the denture base. Relief and border extension for a mesh minor

    connector should be identical to those described for open construction.

    The main disadvantage is the difficulty it presents during the packing of acrylic

    resin. Increased pressure is needed to force resin through the small holes in the

    minor connector. Insufficient packing pressure may result in inadequate resin

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    Screen*: الشبكة المعدنیة في الشبابیك التي تستعمل لمنع دخول الحشرات.

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  • penetration and a weak attachment to the framework. Studies have shown that the

    smaller the openings in this minor connector, the weaker the attachment.

    Mesh construction also may interfere with the arrangement of prosthetic teeth.

    Mesh must cover the entire ridge crest and cannot be limited to those areas between

    the necks of artificial teeth. As a result, the ridge lap areas of artificial teeth may

    require significant reduction to facilitate proper arrangement. When restorative space

    is minimal, this reduction may be significant and may result in compromised

    esthetics.

    Mesh construction may be used whenever multiple teeth are to be

    replaced. Nevertheless, open construction is preferred.

    !

    ➢ Tissue Stoppers (Cast Stops):

    When providing relief under the RPD framework, there is a difference between

    tooth-supported RPD and distal extension RPD, as in the latter the minor

    connector is supported from one end so it may bend under load and acrylic

    packing and processing. To prevent this a small area the free end of the minor

    connector should contact the master cast. This area that resembles a small

    square metal projection is termed as tissue stopper or cast stops. Formed

    by removing a (2×2 mm.) of relief wax.

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    !

    3.Beads and nail heads:

    They are often used in conjunction with metal denture bases. The metal bases

    are cast to fit directly against the underlying soft tissues. Hence, no relief is provided

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