minor connectors, rests & rests seats in prosthodontics

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Minor connectors Rests & Rest seats

Minor connectorsRests & Rest seats Presented by:Dr. Mujtaba AshrafMDS IIDept of Prosthodontics

Contents:Minor ConnectorsFunctionsForm and locationTissue stopsRests and Rest SeatsRole of Rests in Control of Prosthesis MovementForm of the Occlusal Rest and Rest SeatLingual Rests on Canines and Incisor TeethIncisal Rests and Rest Seats2Dr Mujtaba

Minor Connectors3Dr Mujtaba

DefinitionThe connecting link between the major connector or base of a partial removable dental prosthesis and the other units of the prosthesis, such as the clasp assembly, indirect retainers, occlusal rests, or cingulum rests. GPT8

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Connects components to the major connectorDirect retainerIndirect retainerDenture base

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Functions of Minor ConnectorsUnification and rigidityTransfers functional stress to the abutment teeth. This is a prosthesis-to-abutment function of the minor connector.Transfers the effects of the retainers, rests, and stabilizing components throughout the prosthesis. This is an abutment- to-prosthesis function of the minor connector.6Dr Mujtaba

Occlusal forces applied to the artificial teeth are transmitted through the base to the underlying ridgetissue if that base is primarily tissue supported. Occlusal forces applied to the artificial teeth are also transferred toabutment teeth through occlusal rests. The minor connectors arising from a rigid major connector make possiblethis transfer of functional stress throughout the dental arch.

forces applied on one portion of the denture may be resisted by other components placed elsewhere in thearch for that purpose. A stabilizing component on one side of the arch may be placed to resist horizontal forcesthat originate on the opposite side. This is possible only because of the transferring effect of the minor connector,which supports that stabilizing component, and the rigidity of the major connector.6

Form and locationSufficiently bulky to be rigidShould be located in the embrasureThe deepest part of embrasure should be blocked

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1.otherwise the transfer of functional stresses to the supporting teeth and tissue will not beeffective. At the same time, the bulk of the minor connector should not be objectionable.

2. least noticeable to the tongue.3. to avoid interference during placement and removal, and to avoid any wedging effect on thecontacted teeth.7

Should be thickest towards lingual surface and tapering towards the contact area.

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Types of minor connectorsMinor connectors that join clasp assemblies to major connectors

Minor connectors that join indirect retainers or auxiliary rests to major connectors-Stewart

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Minor connectors that join denture bases to major connectors

Minor connectors that serve as approach arms for vertical projection or bar-type clasps-StewartTypes of minor connectors

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Minor connectors that join clasp assemblies to major connectorsJoin clasp assemblies to major connectors must be rigid, because they support the active components of the removable partial denture, the retentive clasps.

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Support the rests, which prevent vertical movement of a prosthesis toward the underlying tissues.These minor connectors should be broad buccolingually, but thin mesiodistally.

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easier to place a prosthetic tooth in a natural position.12

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.

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Minor connectors that join indirect retainers or auxiliary rests to major connectorsThese minor connectors should form right angles with the corresponding major connectors, but junctions should be gently curved to prevent stress concentration

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Minor connectors that join denture bases to major connectorsThese 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.These components must provide minimal interference with the arrangement of artificial teeth.15Dr Mujtaba

In maxillary distal extension bases, it must extent to cover the tuberosity, andIn mandibular distal extension bases it should extend two-third the length of residual ridges,

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Only to provide appropriate mechanical support16

Minor connectors that join the denture base to the major connector may be described as follows

Open/ Lattice construction Mesh construction Bead, wire, or nail-head components on a metal base17Dr Mujtaba

Open/ Lattice constructionOpen construction consists of longitudinal and transverse struts that form a ladder-like network.

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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.19Dr Mujtaba

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 leads to the denture base to fracture.

Transverse struts also must be positioned to facilitate the placement of artificial teeth.

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.20Dr Mujtaba

Advantages of open constructionUsed for multiple teeth replacementProvides strongest attachment of acrylic resinFacilitates rebasing and relining21Dr Mujtaba

Mesh constructionA 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.

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DrawbackDuring 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 penetration and a weak attachment to the framework.

Also interfere with the arrangement of prosthetic teeth.The smaller the openings in this minor connector, the weaker the attachment.

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Bead, wire or nail-head constructionBead, nail-head, or wire components are often used in conjunction with metal denture bases.

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Its is indicated on short-span, tooth supported with well healed ridges.

The primary advantage of a metal base is related toimproved hygiene and thermal stimulation.

DisadvantagesInclude difficulty in adjusting and relining cast metal bases.Furthermore, the attachment of resin is relatively weak.25Dr Mujtaba

Tissue stopUsed in all distal extension partial dentures using lattice work or mesh retention.Provide stability and prevent distortion to framework during packing of acrylic resin.Engage buccal and lingual slopes for stability.

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Cast stop26

Made by removing approximately 2 square mm of the relief wax used to create space beneath the lattice work or mesh from the point where the posterior end of minor connector crosses the centre of the ridge.During waxing this little depression is waxed as a projection of latticework or mesh.

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ReliefMechanical retention of denture base resinAllows the acrylic resin to flow under the constructionRelief wax is placed in the edentulous areas of 1 mm

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Finish LinesThe planned junction of different materials. (GPT-8)

In RPDs it denotes the junction of acrylic resin denture bas and metal major connector.InternalExternalIf they are located on the outer surfaces of major connectors, they are called external finish lines.If they are positioned on the inner or tissue surfaces, they are termed internal finish lines.29Dr Mujtaba

Internal finish lines are formed as a result of relief wax placed on the edentulous ridges of a master cast prior to duplication.The relief wax (24 to 26 gauge) creates an elevated area on the resultant refractory cast. The margins of the relief wax establish internal finish lines in the completed metal framework. The margins of the relief wax should be sharp and well defined.

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External finish lines also must be sharp and should be slightly undercut to help lock the acrylic resin to the major connector.The internal angle formed at the junction of the major or and minor connectors should be less than 90 degrees.

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Less than 90 degree For improve mechanical retention for acrylic resin components. Internal finish line = butt joint31

When viewed from an occlusal perspective, the external finish line should follow an arc established by the lingual surfaces of the remaining teeth.This permits the development of contours that are not irritating to the patient.The contour of the external finish line should be consistent with the contours of the major connector. Transition from the external finish line to a denture base should be smooth and flowing.32Dr Mujtaba

Approach Arm Minor connectorThis serves as an approach arm for a bar clasp, supports a direct retainer and engages an undercut from the gingival margin.Only minor connector tha