73- Combined RPD. Precision attachments. Classification.

specific

• attachment

• precision attachment

• intracoronal/extracoronal attachment

• semi-precision attachment

• ridicular and intraradicular stud type attachments

• bar-type precision attachment

attachment

Mechanical device for fixation, retention, and stabilization of a prosthesis

precision attachment

1. A retainer consisting of a metal receptacle (matrix) and a closely fitting part (Patrix) that are factory made; the matrix is usually contained within the normal or expanded contours of the crown on the abutment tooth or dental implant and the Patrix is attached to a Pontic or the removable dental prosthesis framework.

2. An interlocking device, where one component is fixed to an abutment and the other is integrated into the removable dental prosthesis in order to stabilize and/or retain it.

Precision rest: prefabricated, ridged metallic extension (patrix) in FDP or RDP that fits intimately into box-type rest seat or keyway (matrix) portion of a precision attachment in a restoration

• factory made

• types - intracoronal or extracocornal

intracoronal/extracoronal attachment

Intracoronal - prefabricated attachment for support and retention of a RDP. The male and female components are attached within normal contour of abutment tooth.

Extracoronal - prefabricated attachment for support and retention of a RDP. The male and female components are attached outside thenormal contour.

semi-precision attachment

laboratory fabricated rigid metallic extension (patrix) of a FDP RDP that fits into a slot-type keyway(matrix) in a cast restoration, allowing some movement between the components.

Ridicular and intra-radicular stud type attachments:

• Connected to a root preparation.

• Female or male is soldered / cаst to a root cap coping.

• Some stud type attachments are directly cemented to prepared root without requiring a cast coping.

• Improve easier oral hygiene and enhance crown-root ratio due to the low profile.

• Can be utilized with an implant.

Locks / Interlock: device connecting a fixed unit or a RDP to another fixed unit.

Hinge attachments:

• W type: used mainly for bridge restorations.

• T-U type: used mainly for single crowns.

  (Combination between model cast clasp and attachment; for lower RPD only; one hinge attachment on every side; symmetrical atrophy of the alveolar ridges.)

Bar type precision attachment

• Main Components:

  • a bar element

  • a rider

• For different bar designs various patterns with different cross-sections are usable:

  • Parallel bar

  • Snap bar

  • Resilient snap bar

  • Dolder bar:

    • Has an oval section

    • 3 possible movements:

      • Vertical translation

      • Sagittal rotation

      • Frontal rotation

    • Modifications for Dolder bar are two types:

      • Precision type Dolder: (has a metal transverse and a rider.)

      • Semi-precision type Dolder: (the rider is made of plastic and is changeable).