Indian Dental Academy: will be one of the most relevant and exciting
training center with best faculty and flexible training programs
for dental professionals who wish to advance in their dental
practice,Offers certified courses in Dental
implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic
Dentistry, Periodontics and General Dentistry.
3. RPI is a modified I-bar retainer system.
It was devised by Krol in 1973.
All the components of the I-bar assembly were
modified significantly to fulfill Krol’s design.
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4. Principle of Krol’s design was
“stress control with minimal tooth and gingival
coverage”
His concept is intended to minimize plaque
accumulations that may endanger the health of teeth
and their vesting structures.
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6. MODIFICATION OF EACH COMPONENT
OF THE I-BAR RETAINER REQUIRED TO
FORM A RPI SYSTEM
†Mesial rest modification
†Proximal plate modification
- Modification I
- Modification II
- Modification II
†I-bar modification
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7. Mesial rest preparationMesial rest preparation:
In molars the mesial rest extends only into
triangular fossa.
The canine rests are circular, concave depressions
prepared on the mesial marginal ridge. It does not
cover the entire marginal ridge.
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8. Proximal plate modifications:Proximal plate modifications:
One of the major disadvantages of the I-bar
denture was the excessive tooth contact produced
by the extra long proximal plate.
Krol introduced three modifications to the
proximal plate. They are
- Design modification I
- Design modification II
- Design modification III
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9. Design modification I ::
The proximal plate is
designed to extend along the
entire length of the proximal
surface of the abutment with
a minimum tissue relief.
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10. Bar clasp assembly in which
guiding plane (GP) and proximal
plate (PP) extend entire length of
proximal tooth surface.
Physiologic relief is required to
prevent impingement of gingival
tissues during function.
Extending proximal plate to
contact greater surface area of
guide plane direct functional
forces in horizontal direction, thus
tooth (teeth) are loaded more than
edentulous ridge
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11. Design modification II :Design modification II :
The proximal plate is
designed to extend from the
marginal ridge to the junction
between the middle and
cervical third of the tooth.
Where as in I-bar retainer the
proximal plate extends about
2mm across the tooth tissue
junction.
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12. Bar clasp assembly in which
guiding plane (GP) and
proximal plate (PP) Extends
from marginal ridge to
junction of middle and
gingival thirds of proximal
tooth surface.
The decrease in amount of
surface area contact of
proximal plate on guiding
plane more evenly
distributes functional force
between tooth and
edentulous ridge.
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13. Design modificationDesign modification
III :III :
† The proximal plate is
designed to contact just
about 1mm of the gingival
third of the guiding plane of
the abutment tooth.
† The purpose of reducing
the length of the proximal
plate is to improve the
gingival health. www.indiandentalacademy.com
14. Bar clasp assembly in which
proximal plate (PP) contacts
approximately 1 mm of gingival
portion of guiding plane (GP).
During function, proximal plate
and I – bar clasp arm are
designed to move in
mesiogingival direction,
disengaging tooth. Lack of
sustained contact between
proximal plate and guiding
plane distributes more
functional force to edentulous
ridge
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15. I-bar modification:I-bar modification:
† The tip of the I-bar is
modified to have a pod shape
in order to allow more tooth
contact.
† It is placed more mesially so
that it shifts towards the
mesial embrassure space
under occlusal load and
increases reciprocation.
† The I-bar is designed to
compensate for the decreased
encirclement, {tooth contact},
provided by the proximal
plate and mesial rest.
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16. ADVANTAGES :
Minimal tooth coverage.
Hence these dentures are easy to maintain
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17. RPARPA System
R - Rest
P - Proximal Plate
A -Aker’s clasp
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18. R P AR P A
This is a modification of the
RPI retainer, again devised by
Krol in 1976.
The I-bar in the RPI system
could not be used for patients
with soft tissue undercuts and
high frenal attachments.
In such cases the I-bar of the
RPI retainer is replaced with
an Aker’s {circumferential}
clasp to form the RPA
retainer.
Frontal view
Occlusal viewwww.indiandentalacademy.com
19. Advantages :
Easier to grasp for removal of prosthesis .
It can be used in case of large tissue
undercuts, high frenum etc.
Indicated when bar clasp is contraindicated
and desirable undercuts is located in gingival
3rd of tooth away from distal extension area.
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20. Successful use of the system requires
careful analysis of each component for
the function that it provides and
thoughtful execution of the system in
the abutment preparation.
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21. Mc Cracken’s Removable partial denture prosthodontics. 11th edition,
2004.
Stewart, Rudd and Kuebker – Clinical Removable partial prosthodontics-
third edition
Stewart, Rudd and Kuebker: Clinical Removable denture prosthodontics.
2nd edition, 2001.
Davenport, Basker and Heath :A color atlas of removable partial dentures,
1st edition, 1980.
McCrackens ,Removable partial prosthodontics, 8th edition.
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22. THANK YOUTHANK YOU
For more details please visit
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