This document provides information on the management of Kennedy's Class III classification. It begins with definitions of relevant terminology. It then discusses the history and evolution of removable partial denture (RPD) design. Key biomechanical considerations for RPDs are explored, including the principles of levers, inclined planes, and wedges. The document outlines the essential steps in RPD design, including considerations for direct and indirect retention, rests, connectors, and occlusion. Design specifics for Class III RPDs are covered. The document concludes with a brief literature review of two studies on Class III RPDs.

1. Presented by:
Dr. Jehan Dordi
2nd Yr. MDS
MANAGEMENT OF KENNEDY’S CLASS III
CLASSIFICATION
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2. CONTENTS
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• Terminologies
• Introduction
• History
• Principles of designing
• Biomechanical considerations
• Essentials of partial denture design
• Designing of class III
• Review of literature
• Summary
• Conclusion
• References

3. TERMINOLOGIES
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• RPD- A removable denture that replaces some teeth in a partially edentulous
arch; the removable partial denture can be readily inserted and removed from
the mouth by the patient.
• Biomechanics- An application of the principles of engineering design as
implemented in living organisms.
• Direct retention- retention obtained in a removable partial denture by the use of
clasps or attachments that resist removal from the abutment teeth.
• Indirect retention- the effect achieved by one or more indirect retainers of a
removable partial denture that reduces the tendency for a denture base to move
in an occlusal direction or in a rotational path about the fulcrum line

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• Clasp- the component of the clasp assembly that engages a portion of the tooth
surface and either enters an undercut for retention or remains entirely above the
height of contour to act as a reciprocating element; generally it is used to
stabilize and retain a removable partial denture.
• Rest- a rigid extension of a removable partial denture that contacts the occlusal,
incisal, cingulum, or lingual surface of a tooth or restoration, the surface of
which is commonly prepared to receive it
• Major connector- the part of a removable partial denture that joins the
components on one side of the arch to those on the opposite side
• Minor connector- the connecting link between the major connector or base of
a removable partial denture and the other units of the prosthesis, such as the
clasp assembly, indirect retainers, occlusal rests, or cingulum rests

6. INTRODUCTION
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• The design process is a series of steps that leads toward a solution of the
problem and includes;
• Identifying a need,
• Definition of the problem,
• Setting design objectives,
• Developing a design rationale,
• Devising and evaluating alternative solutions, and
• Providing the solution.
• Authorities in the field of removable partial denture design may differ on their
approach in developing the design of each individual prosthesis.
• There is however, complete agreement that the correct design incorporates
proper use and application of mechanical and biological principles.

8. HISTORY – EVOLUTION OF RPD DESIGN
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• 1711 - First description of RPD was by Heister - he carved a block of bone to fit the
mouth.
• 1728 - Pierre fauchard father of modern dentistry described construction of lower
RPD using two carved blocks of ivory joined together by metal labial and lingual
connectors.
• 1846 - Retentive clasps were first discussed by Mouton.
• 1880 - First maxillary RPD using palatal connector was by balkwell.
• 1899 - Bonwill introduced clasping abutments with gold circumferential clasps.
• 1913- Roach introduced wrought wire clasp

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• 1914- Infra bulge clasp was first mentioned by Henrichsen
• 1970 - Infrabulge clasp did not gain popularity until Roach promoted this
concept. Prothero coined the term “fulcrum line”
• 1970 to present – Investigative and research years

11. Biomechanical Classification Of Removable Partial
Denture
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This is based on the nature of the supporting tissues.
• In tooth borne abutment teeth border edentulous space and all the forces are
transmitted through the abutment teeth to the bone. Class III belongs here.

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• In tooth mucosa borne functional forces are transmitted through abutment teeth
and mucosa to the bone. Class 1,2,4 belong to this grp.
• In mucosa borne regardless of natural teeth present support is derived entirely
from the muco-osseous segment. Most commonly interim or transitional
prosthesis belong to this category.

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• Class I, II and IV RPD are subjected to greater stresses because their support
is a combination of tooth and soft tissue.
• Hence in order to achieve methods to control forces acting on RPD we must
know development of these forces.

15. BIOMECHANICAL CONSIDERATIONS
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16. Simple machine
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1. Lever
2. Wedge
3. Inclined plane
4. Screw
5. Pulley
6. Wheel and axle

17. Lever
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• A lever is a rigid bar supported somewhere along its length. It may rest on the
support or may be supported from above.
• There are three types of levers

18. CLASS I
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• A class-1 lever has its fulcrum located somewhere between the effort and the
resistance.
• In cantilever type of RPD where there is distal extension if there is bone
resorption of the residual alveolar ridge under the distal extension, it will result
in an effort leading to first order lever movement along the fulcrum line

19. CLASS II
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• With a class-2 lever, the fulcrum is at one end, the effort is at the other end and
the resistance is in the middle.
• Seen as indirect retention in removable partial denture

20. CLASS III
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• In a class-3 lever, the fulcrum is at one end and the effort is applied between the
fulcrum and the resistance.
• Usually seen in the tooth supported RPD. Upon consuming sticky food, the food
exerts pulling effort on the prosthetic teeth while the natural teeth and retainers
exert counteracting forces from both sides.

21. Inclined Plane
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• Forces against the inclined plane may result in deflection of that which is
applying the force or may result in the movement of the inclined plane .Neither
of these results are desirable.
• An angle greater than 90 degrees will not yield the desired axial loading and
will produce an inclined plane effect.
• This inclined plane effect can produce slippage of the prosthesis away from the
abutment teeth and can cause orthodontic movement of abutment teeth, with
concurrent pain and bone loss.

22. Wedge
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• A wedge by definition is a solid object with a broad base and its two sides
arising to intersect each other forming an acute angle opposite the base.

23. DESIGN CONSIDERATION
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24. Principles of Design by A.H. Schmidt (1953)
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1. The dentist must have a thorough knowledge of both the mechanical and
biologic factors involved in removable partial denture design.
2. The treatment plan must be based on a complete examination and diagnosis of
the individual patient.
3. The dentist must correlate the pertinent factors and determine a proper plan
of treatment.
4. A removable partial denture should restore form and function without injury
to the remaining oral structure.
5. A removable partial denture is a form of treatment and not a cure.

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Direct Retention
Retentive clasp arm
• Element of partial denture that is responsible for transmitting most of the
destructive forces to the abutment teeth.
• So RPD should be designed to keep clasp retention to a minimum yet provide
adequate retention to prevent dislodgement of denture.

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Qualities of Clasp
• More flexible retentive arm of the clasp, less stress is transmitted to abutment
tooth.
• But as flexibility of clasp increases, both lateral and vertical stresses transmitted
to residual ridge increases.

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Length of clasp
• Flexibility can be increased by lengthening the clasp.
• Clasp length may be increased by using a curved rather than a straight course on
an abutment tooth.

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Material used in clasp construction
• Chrome alloy- greater stress than gold clasp.
• To compensate for this property, clasp arm of chrome alloy are constructed
with smaller diameter.

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Clasp Position
Quadrilateral configuration- class 3
Tripod configuration- class 2
Bilateral configuration- class 1
• Quadrilateral clasping requires direct retainers to be placed at both ends of the
edentulous spaces in a Class III, Modification 1, partially edentulous arch. This
design provides optimal retention and stability for the removable partial
denture.

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• For the Class II, Modification 1, partially edentulous arch, tripodal clasping is
ideal. Direct retainers should be designed to engage abutments adjacent to both
edentulous spaces.
• For a Class I partially edentulous arch, bilateral clasping is indicated. Although
this design does not permit optimal control of harmful forces, it is the best
design for existing conditions

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Frictional control
• A RPD should be designed so that guiding planes are present on as many teeth
as possible.
• Guiding planes are prepared surfaces that are parallel to each other and parallel
to the path the denture takes as it is inserted and withdrawn from the mouth.
• The frictional contact of the prosthesis against these parallel surfaces can
contribute significantly to the retention of the removable partial denture.

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Indirect Retention
• Part of RPD that helps direct retainer prevent displacement of distal extension
denture by resisting the rotational movement of the denture around the fulcrum
line established by the occlusal rests.
• Essential in design of classes I and II partial denture.

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Rests
• Directs forces to long axis of the tooth.
• Floor of the rest seat < 90° - helps it to grasp the tooth and prevent its
migration.
• Occlusal rest – gently rounded.
• Rest must be free to move within the rest seat- permits release of stresses that
will be transmitted to abutment.
• More teeth that bear rest seat, less will be stress placed on each tooth.

34. ESSENTIALS OF PARTIAL DENTURE DESIGN.
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35. FIRST STEP
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• Decide how the partial denture has to be supported.
• If Tooth supported.
Evaluate :
1. Periodontal health
2. Crown and root morphologies
3. Crown to root ratio.
4. Location of tooth in arch.
5. Length of edentulous span.
6. Opposing dentition.
• It should be systemically developed and outlined on an accurate diagnostic casts.

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If tooth and tissue supported.
1. Quality and contour of supporting bone and mucosa
2. Extent to planned coverage of ridge.
3. Type and accuracy of impression registration.
4. Accuracy of denture base.
5. Design characteristics of the component parts of framework.
6. Anticipated occlusal load.

37. SECOND STEP
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Connect the tooth and tissue support units.
These connection is facilitated by designing and locating major and
minor connectors in compliance with the basic principles and concepts.

38. THIRD STEP.
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Determine how the partial denture is to be retained.
Select clasp design that will:
1. Avoid direct transmission of tipping or torqueing forces to the abutment
2. Accommodate the basic principles of clasp design by definitive location of
components parts correctly positioned on abutment tooth surfaces.
3. Provide retention against reasonable dislodging forces.
4. Be compatible with undercut locations, tissue contour and esthetic desires
of the patient.

39. FOURTH STEP
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• Connect the retention units to the support units
FIFTH STEP.
• Outline and join the edentulous area to the already established design
components.

40. VARIOUS FACTORS INFLUENCING DESIGN
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I. Arch relationship.
a. Occlusal relationship of remaining teeth.
b. Orientation of occlusal plane.
c. Space available for restoration of missing teeth.
d. Arch integrity.
e. Tooth morphology.
II. Type of major connector indicated, based on existing and correctable
situations.

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III. If distal extension bases are involved then.
a. Need for indirect retention.
b. Clasp designs that will minimize forces directed towards abutment teeth.
c. Type of base material for later rebasing.
IV. Materials to be used both for framework and for the bases.
V. Type of replacement teeth to be used, influenced by the opposing dentition.

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VI. Need for abutment restoration which may influence the type of clasp arms
to be used.
VII. Patients past experience and reason for making a new denture.
VIII. Response of oral structures to previous stress, the amount of abutment
support remaining.
IX. Method to be used for replacing single teeth or missing anterior teeth.

44. ESSENTIALS OF DESIGN IN CLASS III
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• The design of class III RPD originates on the diagnostic cast so that all mouth
preparations may be planned and performed with a specific design in mind.
Direct retention
• Retention can be achieved with much less potential harmful effect on the
abutment teeth.
• Prosthesis are entirely tooth borne, the transmission of harmful forces to the
abutment and ridges can be minimized.
• The position of the retentive undercut on abutment teeth is not critical.

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Clasps
• Quadrilateral positioning of direct retainers is ideal.
• Tooth & soft tissue contours, esthetics should be considered.
• Type of clasp selected is not critical.
• Bracing arms must be rigid
• Reciprocal elements must be rigid.
Rests
• Rests should be prepared next to the edentulous area.
• Rests should be used to support the major connector and lingual plating.
Indirect retention
• It is usually not required.

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Major connectors
• The simplest connector should be selected.
• The major connector should be rigid.
• It should not impinge on gingival tissue.
• Support from the hard palate should be used in the design of major connector.
• The major connector can be extended onto the lingual surfaces of the teeth to
increase rigidity, distribute lateral stresses, improve indirect retention or
eliminate potential food impaction areas.
• Usually a palatal strap is used, if modification spaces are present
anteroposterior bar can be considered.

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Minor connectors
• They must be rigid.
• They should be positioned to enhance comfort, cleanliness and the placement of
artificial teeth.
Occlusion
• Centric occlusion and centric relation should coincide
• A harmonious occlusion should be established with no interceptive contacts and
with all eccentric movements dictated by or in harmony with the remaining
natural teeth.
• Artificial teeth should be selected and positioned to minimize stresses produced
by prosthesis.

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• Smaller and/or fewer teeth and teeth that are narrower bucco-lingually may be
selected.
• The teeth should be positioned over the crest of the ridge for mechanical
advantage.
• Teeth should be modified to produce sharp cutting edges and ample escape
ways.
Denture base
• Functional type of impression is not required.
• Extent of coverage of residual ridge should be determined by appearance,
comfort and the avoidance of food impaction areas.

50. SUMMARY
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• Retention should not be the prime objective of design instead, efficiency,
esthetics, comfort and preservation should be taken care.
• Simplest type of clasp and connector that will accomplish design objective
should be employed.
• Tooth support should be exploited to the extent that it is available.
• No parts should impinge on free gingival margin.
• All connectors must be rigid.
• Principle of indirect retention should be employed when feasible.
• Harmonious occlusion should be developed.
• The base of the partial denture should be constructed from a functional
impression.

52. CONCLUSION
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• The important factor is that basic principles of designing are not violated.
• Retainer choice, rest placement, connector design are all critical factors.
However, the fact remains that adequate time must be spent in proper diagnosis
and devising a workable treatment plan in terms of patients prosthetic needs and
expectations.
• Once this is achieved the rather mechanical tasks of RPD design can be carried
out to ensure that patients receive the full benefit of our knowledge and skills.

54. REVIEW OF LITERATURE
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55. Shetty PK, Shetty BY, Hegde M, Prabhu BM. Prosthesis for long span Kennedy’s Class III
partially edentulous condition: A case report. Journal of Nepal Dental Association. 2013
Jan;16(1):83.
55
• Shetty et al did a case report on Prosthesis for long span Kennedy’s Class III
partially edentulous condition.
• A 29 years old female with bilateral missing of lower posterior teeth for 7 years
presented for prosthodontic treatment.

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61. Zancopé K, Abrão GM, Karam FK, Neves FD. Placement of a distal implant to convert a
mandibular removable Kennedy class I to an implant-supported partial removable Class III
dental prosthesis: A systematic review. The Journal of prosthetic dentistry. 2018 Jun
1;113(6):528-33.
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• The purpose of this systematic review was to evaluate the current evidence
about the placement of a distal implant associated with a mandibular PRDP to
improve patient satisfaction and the clinical performance of the abutment tooth
and distal implant.
• Two independent prosthetic specialist reviewers conducted this systematic
review.
• The search was performed using selected clinical studies with PRDP associated
with distal implants published in English up to May 2018 from the PubMed and
Cochrane Library databases.

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• A data extraction form was developed to collect general information:
• Authors,
• Title,
• Year of publication,
• Aim of study,
• Level of evidence,
• Number of participants,
• Number of implants used,
• Implant system,
• Implant length and diameter,
• Abutment type,
• Masticatory performance,
• Patient satisfaction,
• Implant mean bone loss,
• Abutment tooth mean bone loss,
• Prosthetic complications,
• Follow-up period, and
• Implant survival rate.

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• The initial electronic search identified 231 studies, and the manual process
identified 15 studies (total of 246 studies).
• After the title and abstract reading and the removal of duplicates, the full texts
of 43 studies were obtained.
• The articles that did not meet the inclusion criteria were excluded (28 studies),
and the data from 15 studies were extracted.
• Seven were retrospective studies, 1 a crossover pilot study, 2 case series, 2
paired clinical studies, and 3 case reports, demonstrating that a high number of
the selected studies were of low methodological quality.
• Nevertheless, the high survival rates for PRDP associated with dental implants
have been described.

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• The following conclusions were drawn from this systematic review:
1. The use of a partial removable dental prosthesis associated with a dental
implant to convert a Kennedy class I to class III dental prosthesis increases
patient satisfaction and masticatory performance and does not impair implant
survival rates.
2. Clinical studies with comparable methodology are still lacking to define
protocols about the use of distal implants associated with PRDP that consider
the abutment tooth survival rate.
3. Long-term, prospective clinical trials are still needed to understand which
implant abutments increase abutment tooth survival rate.

65. REFERENCES
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• Rodney D. Phoenix, David R. Cagna, Charls F. Defreest. Stewart’s Clinical
Removable Partial Prosthodontics. 4th edition.
• Alan b. Carr and David T. Brown. McCracken’s Removable Partial
Prosthodontics. 12th Edition.
• Removable partial denture design. Arthur J Krol, Theodore Jacobson, Fredreick
Finzen. 5th edition
• Robert W. Loney, Removable Partial Denture Manual. 2008
• Indirect retention in partial denture design. J Prosthet Dent 2003, 90, 1-5.
• Evolution of removable partial denture design. Journal Of Prosthodontics 1994,
3,158.
• Mendonca DB, Prado MM, Mendes FA, Borges T de F, Mendonca G, do Prado
CJ, et al. Comparison of masticatory function between subjects with three types
of dentition. Int J Prosthodont 2009;22:399-404.

66. 66
• Chronopoulos V, Sarafianou A, Kourtis S. The use of dental implants in
combination with removable partial dentures: a case report. J Esthet Restor
Dent 2008;20:355-64.
• Praveen M, Chandra Sekar A, Saxena A, Gautam Kumar A. A new approach for
management of Kennedy’s class I condition using dental implants: a case
report. J Indian Prosthodont Soc 2012;12:256-9.
• Bortolini S, Natali A, Franchi M, Coggiola A, Consolo U. Implant-retained
removable partial dentures: an 8-year retrospective study. J Prosthodont
2011;20:168-72.
• Grossmann Y, Levin L, Sadan A. A retrospective case series of implants used to
restore partially edentulous patients with implant-supported removable partial
dentures: 31-month mean follow-up results. Quintessence Int 2008;39:665-71.

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