CLASP RETAINED REMOVABLE PARTIAL DENTURES

COMPONENT PARTS OF A REMOVABLE PARTIAL DENTURE • Retentive Arm • Bracing or Reciprocal Arm or Plate • Rest • Minor Connector • Major Connector • Grid Retention Areas • Tissue Stop • Indirect Retainer • Denture Base • Denture Teeth

Cast RPD Framework Components • Major Connector • Minor Connectors • Clasp Assembly • Retention for Replacement Teeth

Cast RPD Framework Components • MAJOR CONNECTOR

• A

major connector

is the part of a RPD that connects the components on one side of the arch to the components on the opposite of the arch.

Major Connector Requirements • Rigidity • Should be contoured • Should avoid circumjacent structures • Minimum bulk

Maxillary Major Connectors • Palatal Strap • Anterior Posterior (A-P) Palatal Strap • Palatal Plate • Palatal Bar • U-Shaped (Horseshoe) Palatal Connector

Palatal Strap

Palatal Strap

A-P Bar

• Palatal bar is defined as being 8mm or less in width.

• A palatal strap is greater than 8mm in width • OBVIOUSLY,THIS IS NOT

BRAIN SURGERY

Palatal Plate

Strap or Bar ?

Anterior edge should follow contour of rugae

A-P Strap or Bars ????

Maxillary framework should be 6mm from free marginal gingiva, if this is not possible than the framework should end on teeth.

Maxillary Major Connectors • Palatal Strap • Anterior Posterior (A-P) Palatal Strap • Anterior Posterior (A-P) Palatal Bar • Palatal Plate • Palatal Bar • U-Shaped (Horseshoe) Palatal Connector

Mandibular Major Connectors

Mandibular Major Connectors • Lingual Bar • Lingual Plate • Double Ling Bar (Kennedy Bar) • Labial Bar • Swinglock

Mandibular Major Connectors Lingual Plate Lingual Bar

• The superior border of a lingual bar should be at LEAST 4 mm below the free marginal gingiva.

Lingual Bar and Lingual Plate

Indications For Use Of A Lingual Plate • For stabilization of periodontally involved teeth.

• In Class I situations in which residual ridges have undergone excessive vertical resorption.

• When the lingual frenum is high or the space available between the gingival margin and the floor of the mouth is <8 mm.

• Lingual bar approximately 4mm + 4mm clearance from free marginal gingiva = 8mm and want no impingement of lingual frenum.

Indications for use of a Lingual Plate, continued • When the patient has found a lingual bar objectionable in the past • When the future replacement of one or more incisor teeth will be facilitated by the addition to the lingual plate.

Lingual plates must always terminate in a prepared rest seat and never on an inclined surface.

Labial Bar

Double Lingual Bar or Kennedy Bar

Palatal torus U Shaped

Swing Lock Major Connector Or Clasp???

Mandibular Major Connectors • Lingual Bar • Lingual Plate • Double Ling Bar (Kennedy Bar) • Labial Bar • Swinglock

Cast RPD Framework Components • MAJOR CONNECTOR • MINOR CONNECTORS

•

Minor connectors

components.

are those components that serve as the connecting link between the major connector and the other • Many times a minor connector will be continuous with a lingual or palatal plate rather than a distinct element.

Retentive Arm Reciprocal Arm

APPLICATION OF CLASP ASSEMBLY TO TOOTH

•

Minor connectors

may play a critical role by serving as a connector for

indirect retainers

that minimize the rotation of free end saddles.

• An

indirect retainer

that assists the direct retainer in preventing displacement of is that part of an RPD

distal extension denture bases

by resisting lever action from the opposite side of the fulcrum line.

rest within the rest seat that prevents the displacement.

It is the

Indirect retention

• The ideal position for an indirect retainer is at a right angle to the fulcrum and located on the strongest tooth.

Cast RPD Framework Components • MAJOR CONNECTOR • MINOR CONNECTORS

Cast RPD Framework Components • Major Connector • Minor Connectors • Clasp Assembly

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

• Clasps are made up of a retentive arm, a reciprocal or bracing arm, and a rest.

CLASP ASSEMBLY

Clasp • Retentive Arm • Bracing or Reciprocal Arm or Plate • Rest • Minor Connector

Clasps •

Retentive Arm (Direct Retainer)-

which is the

ONLY

that touches the tooth place.

BELOW

that component of an RPD used to retain or prevent dislodgement. The terminal third of portion of the casting the height of contour therefore, it must move over the height of contour for the RPD to go to

It must flex or the tooth move

.

Clasps •

Reciprocal Arm

and removal.)

-stabilizes the tooth by being in contact with the opposing side of the tooth during the entire period of the retentive arm deformation. (

Its movement over the height of contour during insertion

BRACING 2 o Bracing: – Cross arch bracing • location of retentive arms on the same side of the teeth on opposite sides of the arch.

RETENTION (pp84-93) • Angle of convergence-THE UNDERCUT Size and Distance • Length of the clasp arm • Diameter of the clasp arm • Cross sectional form of clasp arm • Material used for clasp arm-CrCo vs Gold • Uniformity of retention-across the arch

Dental Retainers •Clasps –Cast •Suprabulge •Infrabulge –Wrought wire •Attachments •Intracoronal •Extracoronal

Stress breaking • Aim - reduce torquing force on distal abutment teeth

Stress breaking Mesial Rest - Wrought Wire

RPI

REST PLATE I-BAR

• Don’t get hung up on names of clasps; learn the principles, the names will change.

MADDEN CLASP

Failure to cover the retromolar pad