67 - Principles of retainers and pontic construction.

section

• what is retainer

• what is direct retainer?

• what is an attachment?

• what is a clasp assembly

• components of clasp assembly

• what is rest seat

• what is occlusal rest

• wat is indirect retention

• what is pontic

• types of pontic designs

• factors when deciding pontic design

• requirements of pontics

• what is retainer

part that seats on the retainer (abutment) tooth.

• what is direct retainer?

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

what is an attachment

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

what is 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 clasp assembly

Components of the clasp assembly include: -

• Clasp

• Reciprocal clasp arm

• Cingulum

• Incisial or occlusal rest

• Minor connector

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.)

• what is rest seat

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

• what is occlusal rest arm

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

• wat is 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.

• what is pontic

suspended member of a fixed partial denture that replaces missing tooth or teeth. Usually connected to retaining crowns which fit onto abutment teeth.

Pontic types:

• Modified ridge lap

• Saddle

• Ovate

• Bullet

• Hygienic

saddle (ridge lap)

• has full contour buccal and lingual to edentulous ridge.

• Advantage: full contour gives a nice facial and lingual aesthetics.

• Disadvantage: difficult for cleaning especially under the pontic therefore homecare is difficult.

modified ridge lap

• Full contour on buccal side but on lingual side part of the saddle is missing, so tissue contact is only 1mm lingual to the crest of the edentulous area.

• Advantage: provides adequate facial esthetic and increases hygienic access to gingiva of pontic for cleaning. •

• Disadvantage: decreased lingual contour and increased possibility of food entrapment.

Hygienic

• Totally open access under the Pontic for hygiene.

• Advantage: 3mm space between gingiva and pontic giving easier access for hygiene and decreasing possibility of food entrapment.

• Disadvantage: No aesthetics due to lack of facial and lingual contour. → Only for distal teeth

Ovate

• Egg shaped end that protrudes into a concavity in the edentulous tissue.

• Option for frontal teeth.

• Advantage: super aesthetics due to mimicked papillary form which is usually lost post-extraction due to bone loss. •

• Disadvantage: requires a wide ridge to perform → possible need for ridge increase surgery.

Bullet

• Comes to a pointy area like the more pointed end of an egg which challenges the tissue.

• Advantage: increased hygienic access to buccal and lingual surfaces. Can be used against a variety of ridges.

• Disadvantage: decreased aesthetics due to lack of full contour on facial and lingual area.

Main factors when choosing pontic design

Three main factors to consider deciding on which Pontic shape and restorative material to use:

• Edentulous ridge:

  • Shape

  • Width

  • Current condition

• Aesthetic considerations

• Patient homecare

requirements of pontics

• should challenge gingiva where indicated by pontic design to prevent food entrapment under the Pontic.

• should be as smooth as possible especially on the gingival surface to reduce the amount of plaque.