The Basic Principles
Of Definitive RPD
Design To Achieve
successful
prosthesis.
APRIL 17
Studend ID: 19008901
Authored by: NOOR AL AMISHAT
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INTRODUCTION
A. DEFINITIONS
1.Removable Partial denture: A removable prosthesis that replaces
one or more, but not all of the natural teeth and supporting
structures. It is supported by the teeth and/or the mucosa.
2. Interim denture (provisional; temporary): A denture used for a
short interval of time
3. Retention: Resistance to removal from the tissues or teeth
4. Stability: Resistance to movement in a horizontal direction
(anterior-posteriorly or medio-laterally
5. Support: Resistance to movement towards the tissues or teeth
6. Abutment: A tooth that supports a partial denture.
7. Retainer: A component of a partial denture that provides both
retention and support for the partial denture
B- PLAN THE RPD BEFORE BEGINNING ANY OTHER
TREATMENT
A provisional RPD design, produced at the initial treatment planning
stage, we should
• Survey, tripod, heights of contour
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• Draw design on surveyed cast
• Design approved before any treatment started:
o Affects direct restorations
o Can influence need for/preparations for crowns
o Insures RPD can be completed successfully
o NO EXCEPTIONS
THE TYPES OF RPDS DESIGN ARE BASED ON KENNEDYS CLASSIFICATION
C- COMPONENTS OF A PARTIAL DENTURE AND THEIR
FUNCTIONS
1. Major Connector: The unit of a removable partial denture that connects the parts of
one side of the dental arch to those of the other side.
It's principal functions are to provide unification and rigidity to the denture.
2. Minor Connector: A unit of a partial denture that connects other components to the
major connector.
The principle functions of minor connectors are to provide unification and rigidity to
the denture.
3. Direct Retainer: A unit of a partial denture that provides retention against
dislodging forces. A direct retainer is commonly called a 'clasp' or 'clasp unit' and is
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composed of four elements, a rest, a retentive arm, a reciprocal arm and a minor
connector.
4. Indirect Retainer: A unit of a Class I or II partial denture that prevents or resists
movement or rotation of the base(s) away from the residual ridge. Composed of
one component, a rest.
5. Denture Base: The unit of a partial denture that covers the residual ridges and
supports the denture teeth
2- LITERATURE REVIEW
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we learned about removable partial denture prosthesis and its
components and their function in this prosthesis as well as the
definition of each component and how the provisional RPD design is
produced at the initial treatment planning stage
A- DESIGN PRINCIPLES FOR REMOVABLE PARTIAL DENTURES
General Principles
- Minimize framework elements  more hygienic
- Obtain good base adaptation  better stress distribution
- Use what is present (e.g. existing rest seats)
- Plan for the future (e.g. designing for continued use of RPD framework if a critical
abutment is lost; placing rest seats, guide planes and undercuts on crowns to allow
fabrication of an RPD later)
- Never plan an RPD using a single cast alone. You can’t assess abutment mobility,
compressibility of mucosa, the level of the floor of the mouth, prominent frena, or
occlusion. Use mounted models and assess these features intraorally as you plan and
check your design.
– ALWAYS PLAN THE RPD FIRST, prior to beginning treatment
B- HOW THESE PRINCIPLES ARE APPLIED ACCORDING TO EACH
COMPONENT TO ACHIEVE ITS FUNCTION
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Rest Seats/ Rests
Ensure sufficient depth, especially at junction of the rest & minor connector (1.5mm
minimum)
Tooth Borne (Kennedy Class I & II)
– place rests adjacent to edentulous space (both ends)
Tissue/Tooth Borne (Kennedy Class I & II)
- mesial rest preferred
- distal rest preferred when:
- abutment is rotated
- plunger cusp/heavy centric contact on mesial
- large restoration on mesial
Incisal rests/rest seats
- don’t use
- poor esthetics
- more tilting/torquing forces (long lever arm from center of rotation)
Cingulum rests/rest seats
- use composite build up, if no prominent cingulum
- ensure sufficient clearance from opposing occlusion for maxillary cingulum rests
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Occlusal rests/rest seats
1.5 mm of clearance from opposing occlusion (critical at junction of rest & minor
connector)
- line angle of the marginal ridge should be rounded
- deepest part should be located centrally (positive)
Indirect Retainers
- 90° from fulcrum line & as far away from primary abutment as possible
- none required on tooth borne (Cl III & IV) cases
- canine is usually the most anterior tooth used for indirect retention
Direct Retainers
- Kennedy Cl III & IV (Tooth Borne)
- Clasp of choice: cast circumferential
- if can’t use cast circumferential next to edentulous space, use double embrasure
- Kennedy Cl I & II (Tooth & Tissue Borne)
- For posterior abutments, or any tooth needing stress release:
- Clasp of choice: RPI (mesial rest, distal proximal plate and I-bar)
- If can’t use an I-bar in vestibule then use an RPA retainer
- If can’t use a mesial rest then use Combination Clasp
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- if eliminate a direct retainer for esthetics, plan more retention with other features (soft
tissue coverage, longer
Mandibular Major Connectors
Lingual Bar whenever possible (less tissue coverage - hygiene)
Lingual Plate if:
- high floor of mouth
- tori
- frenum
- terminate at FGM
Tissue relief – mandibular major connector (29-30 gauge relief) to avoid tissue
impingement
Maxillary Major Connectors
*No tissue relief
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*Tooth borne (Class III & IV):
Palatal Strap
*Tooth & Tissue borne (Class I & II):
A-P Strap whenever possible
Full Palatal Strap
Anterior Strap (Horseshoe)  only if inoperable torus is present
Other Principles of Design:
Design drawings – absolute accuracy
- RED – wrought wire, undercut position, circled tripod marks
- BLUE – everything else
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CONCLUSION: GREATER ATTENTION SHOULD BE PAID
TO RPD DESIGN PRINCIPLES THAT MINIMIZE THE RISKS
OF TISSUE INJURY AND PLAQUE ACCUMULATION IN
ACCORDANCE WITH MODERN CONCEPTS OF
PREVENTIVE DENTISTRY
SUMMARY: THIS REPORT SPOKE ABOUT THE BASIC
PRINCIPLES TO ACHIEVE THE PERFECT PARTIAL
DENTURE
IN MY OPINION PLANNING THE RPD SHOULD BE THE
FIRST STEP, IN CASE THERE IS ANY MODIFICATIONS TO
ABUTMENTS NEEDED
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REFERENCES:
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