C&B Semi-precision/extracoronal attachments


Semi-precision partial dentures are retained in the mouth by means of mechanical interlocking
components. A specially shaped extension of the partial denture fits into or on to a complementary
receiving area or projection of a natural tooth that has been crowned. The components fit snugly and
consist of a semi-rigid metal to other surface interface, which may also be metal or some other resilient
material such as nylon.

Extracoronal Precision attachments are normally resilient to allow free movement of the
prosthesis to distribute potentially destructive forces or loads away from the abutments to
supportive bone and tissue. Three distinctive movements are defined in function: (1) hinge, (2)
vertical, and (3) rotational. The fewer abutments remaining, and the weaker the abutments are,
the greater the need for resiliency or free movement to direct the forces away from the abutments
to the supportive bone and tissue via the base of the prosthesis.

Advantages of semi-precision/extracoronal partial dentures:

  • A cosmetically enhanced cast partial denture as compared to
    conventional cast partial dentures which utilize cast clasps
  • Blends in with the conformity of remaining natural teeth
  • Functions with a more even pressure on remaining natural teeth than conventional partial dentures
  • Less tooth reduction is required for the crown than with an intracoronal attachment.
    Also, the crown can be made an ideal width since it does not have to accommodate an
    intracoronal attachment.
  • Extracoronal precision attachments are typically easier to insert and remove. These are
    ideal for patients with limited manual dexterity, or the prosthesis has a difficult path of
    insertion and removal.
  • Intracoronal females in retaining crowns will collect food and present problems when the
    patient attempts to seat the intracoronal retained prosthesis. Extracoronal attachments do
    not present this problem.