I-bar Removable
Partial Dentures
introduction
• RPI stands for :
• R : rest
• P : plate ( proximal )
• I : I bar clasp
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Direct retainers
• It is that component part of a RPD that is used to retain and
prevent dislodgement, consisting of clasp assembly or a
precision attachment – GPT
TYPES OF DIRECT RETAINERS
INTRACORONAL
RETAINERS
External attachments
Internal attachments
Bar attachments
Special attachments
EXTRACORONAL
RETAINERS
Occlusally approaching
Gingivally approaching
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clasps
Types on the basis of design
circumferential or Akers clasps :
Simple circlet
Reverse circlet
Fish hook or hairpin
Embrassure clasp
Multiple circlet
Ring clasp
Combination clasp
Vertical projection or Bar or
roach clasps:
T clasp
Modified T clasp
Y clasp
I clasp and I bar
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i-bar
removable
partial
dentures
It is a special type of
removable partial
denture Designed by
Kratochvil in 1963 To
reduce tooth contact
of the retainer
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DIRIEIRENCE BETWEEN IBAR RPD & REGULAR RPD
I-BAR RPD
REGULAR RPD
1. Mesial rest ( instead of
1. Distal rest
distal rest. In other words,
the rest is on proximal
side away from
edentulous space)
2. Occlusally approaching
retainer is used
2. I- bar retainer is used for
direct retention
3. Normal guide planes
3. Long guide planes
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Design concept
• I-Bar Partial denture component :
1. Rest
2. Proximal plates
3. Major connectors
4. Minor connectors
5. Denture base connectors
6. retainers
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Mesial rest
• Function of rest
(a) Provide vertical support against occlusal forces and
(b) Control the relationship of the prosthesis to supporting
structures
• In order to Perform this function
Rest must be of sufficient
bulk To withstand direct occlusal force and also the indirect
force that they are subjected to as fulcrum points
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Proximal plates
• Additional proximal plate on distal surface.
• The proximal plate covers the guide plane from marginal ridge to the tooth tissue junction
and extends onto the attached gingiva for 2mm.
Advantages:
• Provides horizontal stability.
• Reunites & stabilizes the arch
•
retention because of parallelism and because dislodgement is limited to the path of
insertion.
• Protects the tooth-tissue junction by preventing food impaction and because of mental
coverage in the area
• Provides good reciprocation
• Distributes occlusal force throughout the arch
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i-bar
• Retention in most partial denture clasps is achieved with
retentive arm that engages an undercut on an abutment
tooth.
• I-bar provides retention against vertical displacement, But
this retention is augmented considerably by the parallelism
of guide planes that, in most situations, limit displacement to
the path of insertion.
• The arm is long and tapering with a half-round cross section.
• The tip which flexes, engages an undercut at the height of
mesio-distal contour.
• Proper positioning of l-bar allows the tip to move passively
into the mesial embrassure space when the extension base
recieves occlusal loading .
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Advantages & disadvantages
• Advantages of I-bar configuration:
1. Because tooth contour is not altered food accumulation
against the tooth surface is minimized.
2. I-bar is passive in relation to the abutment tooth except against
vertical displacing forces
• Disadvantages:
1. Reduced retention
2. Less horizontal stability than other retentive elements.
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RPI-SYSTEM INTRODUCTION
• RPI is a modified I-bar retainer system
• Krol devised it in 1973.
• All the components of the I-bar assembly were modified significantly
to fulfill Krol's design.
• Principle of Krol's design was - "Stress control with minimal tooth &
gingival coverage"
• The speciality of these dentures is that the direct retainer is modified
such that the retentive and reciprocal units of the clasp act in the
mesio-distal direction (in conventional design the retentive &
reciprocal units act buccolingually).
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Modification of
each component of
I-bar retainer
required to form
RPI system
MESIAL REST
MODIFICATION
PROXIMAL PLATE
MODIFICATION
I-BAR
MODIFICATION
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Modification of each component
MESIAL REST
MODIFICATION
I-BAR
MODIFICATION
• The mesial rest extends only into the
triangular fossa even in molar
preparations.
• The tip of the I-bar is modified to have
a pod-shape in order to allow more
tooth contact.
• The canine rests are circular, concave
depressions prepared on the mesial
marginal ridge.
• It is placed more mesially so that it
shifts towards the mesial embrasure
space under occlusal load and
increases reciprocation.
• It does not cover the entire marginal
ridge
• The I-bar is designed to compensate
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PROXIMAL PLATE
MODIFICATION
• One of the major disadvantages of the I-bar denture was the
excessive tooth contact produced b the extra long proximal plate.
• Krol introduces 3 modifications to the proximal plate.
• Any one of these modifications may be followed while designing an
PI retainer.
The 3 different design modifications of the proximal plate are:
1. Design modification I
2. Design modification Il
3. Design modification III
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PROXIMAL PLATE
DesignMODIFICATION
Design
Design
modification
I
modification
II
modification
III
• Here the proximal
plate is designed to
extend from the
marginal ridge to the
junction between the
middle & cervical third
of tooth (remember in
an I-bar retainer the
proximal plate
extends about 2mm
across the tooth
tissue junction )
• Here the proximal
plate is designed to
extend along the
entire length of the
proximal surface of
the abutment with a
minimum tissue relief.
• A relief is provided
near the gingival
margin at tooth tissue
junction.
• This allows the
• Here, the proximal
plate is designed to
contact just about 1
mm of the gingival
third of the guiding
plane of the
abutment tooth.
• The purpose of
reducing the length
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of the proximal plate
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