Dr. Waseem Mushtaha Al azhar university Gaza Lama El Banna

1. INDIRECT RETAINERS
Dr. Waseem Bahjat Mushtaha
PhD in prosthodontics

2. Definition:
Indirect retainer:
It is a component of a tooth mucosa borne RPD,
which is placed on the opposite side of the
fulcrum line assisting the direct retainer in
preventing displacement of an extension base
through mechanical leverage.
Fulcrum line:
An imaginary line between the two occlusal rests on
the terminal abutment about which the denture
rotates when the base moves away from the
residual ridge

4. Principle of indirect retention:
-In the case of a distal extension base rotational
movement around the fulcrum line, either towards
the tissue or away from the ridge, may occur as
forces are applied.
-The vertical component of rotating motion towards
the ridge can be controlled by stable denture base
support.
-Sticky foods. muscle action and gravity in maxillary
dentures may exert a pull and tend to lift the
denture base away from the ridge. This vertical
component of force occurs in the direction away
from the ridge is counteracted by the indirect
retainers

9. Factor influencing the effectiveness of indirect retainers:
1-The effectiveness of direct retainer:
The direct retainer should hold the main rests in their seats. If
total displacement of the rest occurs, there would be no
rotation about the fulcrum, and no indirect retention.
2-Distance from the fulcrum line:
As the distance between the indirect retainer and the fulcrum
line increase the indirect retention increase.
3-Rigidity of the connectors:
All the connectors must be rigid for the indirect retainer to
function properly.
4-Support for the indirect retainer:
Tooth inclines. should never be used to support indirect
retainer. It must be placed in a definite rest seat on which
slippage or tooth movement cannot occur.

10. Forms of indirect retainers:
1-Auxiliarv occlusal rest:
The most commonly used indirect retainer is an
auxiliary occlusal rest placed far away from the
extension base as much as possible. For class I
arch, bilateral rests on the mesial marginal ridge of
the first premolars are used . For class II arch. The
indirect retainer is placed on the marginal ridge of
the first premolar on the opposite side of the distal
extension base . For long class IV, indirect
retainers are placed posterior to the fulcrum line
on molars as much posterior as possible.

14. 2-Canine extension from occlusal rest:
A finger extension from, a premolar rest placed on
prepared lingual slope of adjacent canine serves as
indirect retainer . This method is used when a first
premolar must serve as a primary abutment.
3-Canine rest:
Cingulum or incisal rests on canine are used as
indirect retainer when the mesial marginal ridge of
the first premolar is too close to the fulcrum line.
This indirect retainer is more effective if the minor
connector is placed in the embrasure anterior to
the canine.

18. 4-Cingulum bars (continuous bars) and lingual plates:
The indirect retainers in case of cingulum bars and lingual
plates are actually the terminal rests in the form of
auxiliary occlusal rests or canine rests.
5-Modification areas:
In class n modification (1) RPD, the fulcrum line extends
between the abutment adjacent to the distal extension base
and the most distal abutment on the tooth-supported side.
The rest on the anterior abutment on the tooth supported
side acts as indirect retainer in addition to its supporting
function.
6-Rugae support:
The rugae area is firm and well situated to provide indirect
retention for the distal extension base . However, the tissue
support is less effective than posterior tooth support and
rugae cover is undesirable if it can be avoided.