1. Indirect retainers assist direct retainers in preventing displacement of the distal extension denture base by functioning through lever action on the opposite side of the fulcrum line. They are most commonly occlusal rests placed on premolars. 2. For indirect retention to be effective, it must be placed some distance from the fulcrum line, usually contacting multiple teeth. It helps stabilize the denture base and reduces stresses on abutment teeth. 3. Indirect retainers have auxiliary functions like preventing tilting of abutment teeth, stabilizing the major connector, and providing early indication of need to reline the denture. Their location and design depends on factors like arch, ab

1. INDIRECT RETAINERS
DR HARSHA R
MDS
Dept Of
Prosthodontics
Navodaya Dental
College

2.  A removable partial denture design derives support from
two main sources.
Periodontally sound teeth
Through properly constructed
Rest contacting well prepared
Rest seat.
In edentulous region,
Residual ridge and associated
Soft tissue with a well adapted
denture base
Disparity provided by two presents distinct challenges in RPD design

3. DEFINITIONS
 Indirect retainer :
the component of a partial removable dental
prosthesis that assists the direct retainer(s) in preventing
displacement of the distal extension denture base by
functioning through lever action on the opposite side of the
fulcrum line when the denture base moves away from the
tissues in pure rotation around the fulcrum line.
(GPT-9)

4.  Indirect retention:
The 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.
(GPT-9)

5. Fulcrum line
1.A theoretical line passing through the point around which a
lever functions and at right angles to its path of movement .
2: An imaginary line, connecting occlusal rests, around which a
partial removable dental prosthesis tends to rotate under
masticatory forces. The determinants for the fulcrum line are
usually the cross arch occlusal rests located adjacent to the
tissue borne components.
(GPT-9)

6.  ROTATION
is that movement of an appliance which may
occur in a vertical direction while its occlusal rests remain in
abutment contact.
 DISPLACEMENT
is that movement of an appliance when the
primary occlusal rests also lose tooth contact.

7. PRINCIPLE OF INDIRECT RETAINER

8. THE NEED FOR INDIRECT
RETENTION
 Not all removable appliances are in need of indirect retention.
 IN CLASS III, SHORT SPAN CLASS IV
occlusal rest - prevent movement toward basal structures
direct retainer – prevent to a limited degree, movement away
from the supporting structures
no rotation can take place.

9.  In Kennedy class I, II and long span class IV

10. PRE-REQUISITES FOR INDIRECT RETAINER
 periodontally sound teeth.
 They should contact as many teeth as possible to reduce the
possibility of moving teeth by the application of excessive
force.
 Extension of the denture base on mucosa is effective provided
the mucosa is firm.
 They can only function in conjunction with direct retainer
(clasps). Indirect retainer by itself does not provide retention.
 Indirect retainers are best made of cast alloy, so that they fit
teeth accurately and appear as unobtrusive as possible.

11. FULCRUM LINES AND INDIRECT RETENTION
 The term “fulcrum line” was used by Prothero to designate an
imaginary line extending through the occlusal rest areas of the
principal abutments (those supplying the major retention).

12.  For these definitions to be valid, the principal abutment teeth must
have rests on them.
This is not always true, since some partial dentures do not have a rest
on the principal abutment tooth but on the next tooth in the arch.

14. INDIRECT RETENTION
a second fulcrum line is produced

15.  When a second fulcrum line is produced by indirect retention ,
the prosthesis rotates about the primary fulcrum line if the
denture base is forced tissue ward, and about the secondary
fulcrum line if the denture base is lifted off the tissue .
PF SF

16. LOCATION OF INDIRECT RETAINER
 IDEAL POSITION
longest right angle projection from the fulcrum line ending in a
definite seat on a suitable tooth.
 An indirect retainer can be effective only if it is placed some
considerable distance anterior to the direct retainers.

20. INDIRECT RETENTION WITH MESIAL AND DISTAL
RESTS.
 A mesial rest, in conjunction with retention located distally on an
abutment tooth, reduces the need for indirect retention as compared
with a distal rest associated with retention that is located mesially on an
abutment tooth.
Force E tends to move the removable partial
denture away from the tissue by rotating it
around the mesial rest. As this rotation
occurs, the retentive clasp arc engages the
retentive area thus resisting movement.

21. Figure illustrates a distal rest with retention supplied by a retentive arm
located on the mesiobuccal surface of the tooth. Force E tends to move
the removable partial denture away from the tissue by rotating it around
the distal rest (A). As this rotation occurs, the retentive clasp arm is
disengaged from the retentive area and offers no resistance to
movement.

22. FACTORS INFLUENCING THE EFFECTIVENESS
OF INDIRECT RETENTION
 Distance from the fulcrum line

23. The objective is to increase the distance between the direct and
indirect retention as much as feasible.

24. DIFFERENT FORMS OF INDIRECT
RETAINERS
 Indirect retainer can be divided on the basis of their position in
mouth.
 A further division occurs on the basis of tissue on which
retainer rests.
 In the upper jaw either it can be teeth or the tissue where as in
the lower jaw only teeth can be used for this purpose.

25. Position Tissue on
which retainer
rests
Type of indirect retainer
1. Anterior Tooth Anteriorly placed occlusal arm or
incisal rest.
Continous clasp and its
modification.
Palate Palatal arm.
Anterior palatal bar.
2. Posterior Tooth Posteriorly placed occlusal rest.
Palate Posterior palatal bar or
extension of palatal plate.

26. OCCLUSAL REST
 The most commonly used indirect retainer is an auxillary
occlusal rest located on the occlusal surface.
 In the mandibular class 1 arch the location is on the mesial
marginal ridge of the first premolar on each side of the arch.

27.  The ideal position of the indirect retainer is perpendicular to
the fulcrum line that is mostly vicinity of the central incisors,
which are too weak and have lingual surfaces that are too
perpendicular to support a rest.

28.  The bilateral rest on the first premolar are quite effective even
though they are located closer to the axis of rotation
 Rest on the premolar is not only effective without jeopardizing
the weaker single rooted tooth but also interference with the
tongue is far less. The minor connector can be placed in the
embrasure between the canine and premolar rather than
anterior to the canine.

29.  Indirect retainer for class 2 partial dentures is placed on the
marginal ridge of the premolar on the opposite side of the arch
from the distal extension base.
 Bilateral rest are seldom indicated except when an auxillary
occlusal rest is needed to support the major connector or
when the prognosis of the distal abutment is poor and
provision is being considered for later conversion to class1
partial dentures.

30. CANINE EXTENSIONS FROM OCCLUSAL
RESTS
 A finger extension from the premolar rest is placed on the
prepared lingual slopes of the adjacent canine. Such an
extension is used to increase the indirect retention by
increasing the distance of resisting elements from the fulcrum
line

31. CANINE RESTS
 INDICATION
 When the mesial marginal ridge of the first premolar is too
close to the fulcrum line.When the teeth are overlapped, that
fulcrum line is not accessible the adjacent canine may be
used.
 Such a rest may be made effective by placing minor connector
in the embrasure anterior to the canine either curving back on
to the prepared lingual rest seat or extending to the mesio
incisal rest.

32. INCISOR REST
 The root form, root length, inclination of the tooth and the ratio
of the length of the clinical crown to the alveolar support must
be considered in determing the site and form of rest placed on
incisor.
 Incisal rests are placed at the incisal angles of the anterior
teeth. It is placed generally in enamel

33. CINGULUM BARS
(CONTINUOUS CLASP AND LINGUOPLATE)
 The first continuous clasp was made by Dr. J. Wright Beach of
Buffalo and was used to stabilize a lingual bar.
 It acted in the capacity of an indirect retainer. Dr. Beach called
his appliance the “wrought continuous interdental support.

35. ANTERIOR PALATAL BAR

36. MODIFICATION AREAS
 The occlusal rest on the secondary abutment in class 2 partial
dentures may serve as indirect retainer.
 This depends on distance of the secondary abutment from the
fulcrum line.
 The anterior abutment on the tooth-supported side is a
secondary abutment securing to support and retain one end of
the tooth supported segment as well as adding horizontal
stabilization to the denture

38. RUGAE SUPPORT
 Some clinicians consider the coverage of rugae area of the
maxillary arch as a means of indirect retention because the
rugae area is firm and usually well situated to provide indirect
retention for class1 situation

39. AUXILLARY FUNCTIONS OF
INDIRECT RETAINER
 It reduces antero-posterior tilting leverages on the
particular abutment.
 This is particularly important when an isolated tooth is
being used as an abutment ‘a situation that should be
avoided whenever possible.
 The proximal contact with the adjacent tooth prevents such
tilting of the abutment as the base lifts away from the
tissues.

40. AUXILLARY FUNCTIONS OF INDIRECT
RETAINER
 Contact of its minor connector with axial surfaces aid in
stabilization against horizontal movement of the denture.
Such tooth surfaces when made parallel to the path of
placement may also act as auxillary guiding planes.
 Indirect retainer act as vertical stops for the anterior portion
of the denture, thus preventing food from forcing the major
connector onto the underlying soft tissues.

41. AUXILLARY FUNCTIONS OF INDIRECT
RETAINER
 Anterior teeth supporting indirect retainer are stabilized
against lingual movement. It may act as auxillary rest to
support a portion of major connector.
 Example; a lingual bar may be supported against settling
into the tissues by the indirect retainer acting as an
auxillary rest.

42. AUXILLARY FUNCTIONS OF INDIRECT
RETAINER
 Prevents settling of the major connector - in the absence of
the indirect retainer there is upward movement of the distal
extension base which is accompanied by the downward
movement of the major connector causing impingement of
the soft tissues.
 By preventing the downward movement of the partial
denture, the indirect retainer force the direct retainer to
activate when movement away from the basal seat is
attempted by extension bases.

43. AUXILLARY FUNCTIONS OF INDIRECT
RETAINER
 It may provide the first visual indication for need to reline
the partial denture. Deficiencies in the basal seat support
are manifested by the dislodgement of the indirect retainer
from their prepared rest seat.
 It helps to stabilize the major connector against the vertical
and lateral forces and decrease the stresses on the
principal abutment teeth by transmitting forces to other
teeth in the arch.