Major Connectors, Minor Connectors, Rests, and Direct Retainers

Flashcards covering key vocabulary and concepts from the lecture notes on removable partial dentures, focusing on major and minor connectors, rests, and direct retainers.

Cast Stop

A small area at the free end of the minor connector that should contact the master cast to prevent bending during the packing and processing of acrylic resin.

Bead Retention

Achieved by placing resin beads on the appropriate segments of the wax pattern, investing the completed pattern, eliminating the pattern materials via heat application, and casting the framework.

External Finish Lines

These are located on the outer surfaces of major connectors.

Internal Finish Lines

These are positioned on the inner or tissue surfaces.

Internal Finish Lines

Result from relief wax placed on the master cast prior to duplication.

External Finish Lines

These should be slightly undercut to help lock the acrylic resin to the major connector. The internal angle formed at the junction of the major and minor connectors should be less than 90 degrees.

Approach Arms for Vertical Projection or Bar-Type Clasps

These are the only minor connectors that are not required to be rigid and support direct retainers (clasps).

Rests

The components of a removable partial denture that transfer forces down the long axes of the abutment teeth.

Rest Seats

The prepared surfaces of the teeth into which rests fit.

Rest

Serves as a vertical stop for the prosthesis and minimizes vertical displacement of the prosthesis, preventing injury to the soft tissues.

Rest

Maintains the retentive clasp in its proper position.

Primary Rest

A rest that is part of a retentive clasp assembly.

Auxiliary Rest/Secondary Rest

A rest that is responsible for additional support or indirect retention.

Auxiliary or Secondary Rests

Used as indirect retainers in extension base removable partial dentures (Class I, Class II, and long-span Class IV applications). These rests are placed anterior or posterior to the axis of rotation to prevent the extension bases from lifting away from the underlying ridges.

Occlusal Rests

Seated on the occlusal surfaces of posterior teeth.

Lingual or Cingulum Rests

Seated on the lingual surfaces of anterior teeth, usually maxillary canines.

Incisal Rests

Seated on the incisal edges of anterior teeth.

Occlusal Rest Seat

The outline form of this rest seat should be roughly triangular, with the base of the triangle located at the marginal ridge and the rounded apex directed toward the center of the occlusal surface.

Occlusal Rest Seat

This rest seat should occupy one third to one half the mesiodistal diameter of the tooth and approximately one half the buccolingual width of the tooth.

Occlusal Rest Seat

The floor of this rest seat must be inclined slightly toward the center of the tooth; the enclosed angle must be less than 90 degrees.

Occlusal Rest Seat

The deepest part of this rest should be located near the center of the mesial or distal fossa.

Occlusal Rest

This rest must be at least 0.5 mm thick at its thinnest point and 1.0 to 1.5 mm thick where it crosses the marginal ridge.

Lingual or Cingulum Rests on Maxillary Canines

The normal morphology facilitates preparation of this type of rest seat with minimal tooth reduction.

Lingual or Cingulum Rest Seat

The form of this rest seat should be V-shaped when viewed in cross section.

Lingual Rest Seat

The preparation should display a relatively upright lingual wall originating at the cingulum and extending incisally, and a wall inclining labiogingivally toward the center of the tooth.

Incisal Rests

Less desirable than lingual rests; if a cast restoration is planned for an anterior abutment, this rest is never indicated.

Incisal Rest Seat

This rest seat should appear as a small, V-shaped notch located approximately 1.5 to 2.0 mm from the proximal-incisal angle of the tooth.

Direct Retainers

These components of a removable partial denture engage abutments and resist dislodging forces.

Intracoronal Direct Retainer

Resides within the normal contours of an abutment and functions to retain and stabilize a removable partial denture.

Extracoronal Attachments

Consists of closely fitting components termed matrices and patrices and are located outside the normal clinical contours of abutment crowns.

Retentive Clasp Assembly

A metal clasp arm that displays a limited amount of flexibility that allows the tip of the retentive clasp to pass over the greatest diameter of an abutment and contact its surface as it converges apically.

Path of Insertion and Removal

The path along which the prosthesis will be inserted and removed from its fully seated position.

Height of Contour

The greatest diameter of the tooth.

Prothero's Cone Theory

A conceptualization where the contours of a clinical crown resemble two cones sharing a common base.

Suprabulge

The portion of an abutment that converges toward the occlusal or incisal surface.

Infrabulge

The portion of the clinical crown that converges apically from the height of contour.

Retentive

A tooth surface residing apical to the height of contour.

Retentive

The area or location may also be designated as undercut relative to the height of contour.

Suprabulge Clasp Arm

Approaches the undercut region of an abutment from an occlusal or incisal direction.

Infrabulge Clasp Arm

Approaches the undercut region from an apical direction.

Rest

Vertical support for the prosthesis, rests on the occlusal surfaces of premolars and molars, the cingula of maxillary canines, or the incisal edges of mandibular incisors. It resists displacement of the prosthesis toward the supporting tissues and transmits functional forces parallel to the long axes of the abutments.