General idea about removable partial dentures definitions and categories. major and minor components of RPD, retainers and its design

1. Presented by
Rusul N (Assistant Lecturer)
Aseel A. R. (Lecturer)
Zydoon Hassan(Assistant Lecturer)
Karbala university collage of
dentistry, Department of
prosthdontics
PARTIAL DENTURE

2. • Partial denture: a dental prosthesis that restores one or more but
not all of the natural teeth and/or associated parts and that is
supported in part by natural teeth and/or the mucosa.
• Partial denture construction: the science and techniques of
designing and constructing partial dentures.

3. •Types of Partial dentures
1-RPD
2-FPD

4. Indication for removable partial denture:

5. RPD is generally avoided in the following cases:
• -Patient with large tongue which tends to push the denture way.
• 2-Patient attitude:mentally retarded patients cannot maintain a
removable prosthesis.
• 3-Poor oral hygiene

6. • denture retention: the resistance in the movement of a denture
away from its tissue foundation especially in a vertical direction 2:a
quality of a denture that holds it to the tissue foundation and/or
abutment teeth.

7. • denture stability: the resistance of a denture to movement on its
tissue foundation, especially to lateral (horizontal) forces. A quality
of a denture that permits it to maintain a state of equilibrium in
relation to its tissue foundation and/or abutment teeth.
• Support: Resistance to movement towards the tissues or teeth
• denture supporting structures: the tissues (teeth and/or
residualridges) that serve as the foundation for removable partial
or complete dentures.

8. Components of a typical removable partial
denture
• 1. Major connectors
• 2. Minor connectors
• 3. Rests
• 4. Direct retainers

9. • 5. Stabilizing or reciprocal components (as parts of a clasp
• assembly)
• 6. Indirect retainers (if the prosthesis has distal extension
• bases)
• 7. One or more bases, each supporting one to several
• replacement teeth

10. Major Connectors
• The unit of a removable partial denture that connects the various
parts of the denture. Its principal functions are to provide
unification and rigidity to the denture

11. Requirements:
•are made of an alloy compatible with oral tissue
•are rigid & provide cross arch stability through the
principle of broad distribution of stress.
• should be free of movable tissue

12. • Bony and soft tissue prominences should be avoided during
placement and removal.
• Relief should be provided to prevent its settling into areas of
possible interference, such as inoperable tori or elevated median
palatal suture
• Major connectors should be located and/or relieved to prevent
impingement of tissue that occurs because the distal extension
denture rotates in function

13. Maxillary Major Connectors:
•1-Sigle palatal strap:
• Indication: CLIII or CLIII mod I
• Disadvantage:1-Cannot be used to connect anterior replacement.
• 2-Relief may be required over bony midline areas in some instances to
prevent fulcruming over the overlying soft tissue.
• 3-posterior border should end before the junction of the soft & hard
palate to avoid discomfort.

14. Single palatal bar(posterior palatal bar):half oval cross section
• Indications:in CLIII cases when only one or two teeth are to be
replaced on each side & the teeth anterior or posterior to the space
can bear the load.
• Disadvantage:less than 8mm width is referred to as a bar the most
objectionable because of discomfort.

15. •Palatal plate-type connector
• also called anatomic replica palatal major connector
• Indication:
• 1-CLI
• 2- long distal extension cases & excessive ridge resorption.
• 3-the primary abutments are periodontally involved, requiring
maximum stress distribution.
4-flabby tissue or where there is a shallow palatal vault this
connector also provides greater stability and stress distributing
characteristics.

16. • -Combination Anterior-Posterior Palatal Strap: closed horse
shoe
• -Indications:1-CLII Mod I long edentulous area &CLIV cases.
• 2-large inoperable tori.
• 3-when anterior & posterior abutment teeth are widely separated.

17. • 5-Combination Anterior& posterior bar major connectors:
• 1-CLVI case.
• 2-long edentulous span in CLII Mod I.
• 3-when anterior & posterior teeth are widely separated.
• 4-large inoperable tori.
• 5-patient wants to avoid complete palatal plate.

18. • 6-U-shaped Or "Horse-Shoe palatal connector
• sIndications: 1-large inoperable tori. 2-several anterior teeth to
be replaced.

19. Mandibular Major Connectors: Tongue space
• Tongue space
• Periodental prob
• Functional impression

21. 2-Linguopalate ( lingual palate)

22. Indications
• 1-there is no space for lingual bar. Lingual frenum high,
ioperable tori.
• 2-when most of posterior teeth are lost& additional indirect
retention is required.
• 3-when one or more incisor teeth have to be replaced in the
future the teeth added by attaching retention loop to them.
• 4-stabilize periodontally weakened teeth act as splint.
• 5-CLI cases in which the residual ridges have undergone
excessive resorption, lingual plate will engage the remaining
teeth to resist horizontal rotation.
• 6-step back design(modification of lingual plate) used in case
of spaced anterior teeth.

23. -Subligual bar
• Indications: it can be used if the sulcus depth too little & a lingual
bar cannot be placed with at least 4mm clearance from the free
gingival margin

25. Cingulum bar
• thin narrow3mm metal strap located on cingula of anterior teeth,
scalloped to follow interproximal embrasures with inferior &
superior borders tapered to tooth surfaces. Originates bilaterally
from the rest of adjacent principle abutment. Cannot be used when
anterior teeth tilted lingually or there is wide diasthema because of
metal display. has the disadvantage of food trap & periodontal
problems.
• Indications: when a lingual plate or sublingual bar is indicated but
the axial alignment of the anterior teeth is required excessive
blockout of interproximal undercuts.

26. Labial bar:
• half pear shaped with bulkiest portion inferiorly located on the
labial & buccal aspects of the mandible, superior border located at
least 4mm inferior to labial & gingival margins, inferior border
located at the juncture of attached & unattached mucosa.
• Indications:1-when lingual inclinations of remaining teeth cannot be
corrected, preventing placement of lingual bar.
• 2-inoperable lingual tori or tissue undercut.

28. Part2
other component of
RPD

29. Minor Connectors
• A unit of a partial denture which connects other components
(e.g. direct retainer, indirect retainer, denture base, etc.) to
the major connector.
Functions
1. Provide unification and rigidity
2. Provide stress distribution by transferring stresses from the
major connector to other parts of the partial denture and from
the partial denture to the abutment teeth
3. Act as bracing elements through contact with guiding planes
opposing the retentive arms.
4. Maintain a path of insertion via contact with guiding planes

31. Finishing line:
the junction between metal & plastic portions of a RPD. An internal
finish line is on the internal or tissue surface & is formed while
preparing a cast for dublication. An external finish line is on the
polished surface of a denture & is formed in the wax pattren
Vertical finishing line
Horizontal finishing line

32. Rests and Rest Seats
• Rest: A rigid component of a removable partial denture which rests on
the occlusal, lingual or incisal surface of a tooth to provide vertical
support for the denture. Although a rest is a component of a direct
retainer (retentive unit, clasp assembly), the rest itself is classified as
a supporting element due to the nature of its function.
• Rest seat: the prepared portion in a tooth or restoration created to
receive the occlusal, incisal, cingulum, or lingual rest
• function:
1-maintains component in their planned position.
2-maintains established occlusal relationships by preventing settling of
the denture.
3-ptrevents impingement of soft tissue.
4- directs & distributes occlusal load to abutment.

33. Types of Rest
• Occlusal rest
Conventional occlusal rest
Extended occlusal rest
Interproximal occlusal rest
Internal occlusal rest
• Lingual rest (cingulum)
• Incisal rest
• Implant as a rest

34. direct retainer
A direct retainer is any unit of a removable dental prosthesis that
engages an abutment tooth or implant to resist displacement of the
prosthesis away from basal seat tissue. it is ususally composed of 1)
retentive arm, 2)reciprocal (bracing) element arm, 3)rest and 4)minor
connector.
• Requirement of direct retainer:
• Support
• Reciprocity
• Stability
• Retention
• Encirclement of greater than 180 of the tooth.
• Passivity

35. Types of Direct Retainers
1.the intracoronal retainer (precision attachment.)
the intra-coronal retainer is either cast or attached totally within
restored natural contours of an abutment tooth . it's typically
composed of the prefabricated machined key and key way , with
opposing vertical parallel walls , which serve to limit movement
and resist removal of the partial denture through frictional
resistance usually regarded as an internal or a precision
attachment.

36. B. Extra coronal retainer
• Clasps designed without movement accommodation
• It also named subrabulge clasp or occlusally approach clasp since it
approach the retentive undercut from the occlusal direction.
• Types of Circumferential clasps:
• Circumferential (Circle or Akers) clasp
• The ring clasp
• The embrasure clasp
• Back-action Clasp
• Multiple Clasp.
• Half and half clasp
• Reverse-action Clasp.(hair pin)

37. The embrasure clasp
• Indication
• In the fabrication of an unmodified Class II or Class III partial
denture, no edentulous spaces are available on the opposite side of
the arch to aid in clasping
• Back action Clasp
• used on premolar abutment anterior to the edentulous space

38. • Reverse-action Clasp.(hair pin)
• Advantages:
a. Allows use of undercut adjacent to edentulous space
• Disadvantages:
a. Almost impossible to adjust
b. Non-esthetic
c. Difficult to fabricate so the upper portion of the retentive arm
clears the opposing occlusion
d. Covers extensive tooth surface and acts as a food trap
e. Insufficient flexibility on short crowns due to insufficient clasp arm
length

39. 2) Clasps Designed to Accommodate Functional
Movement (RPI, RPA, and Bar Clasp)
• Bar type
• a.The bar clasp is a cast clasp that arises from the
partial denture framework and approaches the
retentive undercut from gingival direction
• b. Retentive clasps are identified by shape of
retentive terminal, i.e. T, Y, L, I, U, and S.
• Contraindications:
• a) deep cervical undercuts - food trap or
impingements result
• b) severe soft tissue or bony undercuts
• c) insufficient vestibular depth for approach arm
• d) pronounced frenal attachments in area -
impingement

40. The RPI clasp
• The rest is located on the mesio-occlusal surface of
premolar and mesiolingual surface of canine.
• The proximal plate (essentially wider minor
connector) is located on a guiding plane on th distal
surface of the tooth. On premolar the proximal
plate should be extended lingually so the distance
between the proximal plate and mesio-occlusal rest
less than mesodistal width of the tooth.
• Contraindications to the R.P.I. Clasp
• 1. Insufficient depth of the vestibule. (The inferior
border of the I-bar must be located at least 4 mm.
from the gingival margin.)
• 2. No labial or buccal undercut on the abutment
• 3. Severe soft tissue undercut
• 4. Disto-buccal undercut (less than 180° encircle

41. RPA clasps
• Mesial rest concept clasps have been
proposed to accomplish movement
accommodation by changing the fulcrum
location the RPA consist of [rest, proximal
plate, Akers] the Akers is used instead of I bar
which arises from the proximal plate and end
in mesiobuccal undercut , it used when there
is insufficient vestibular depth or sever tissue
under cut.
• Some advantages are
• (1) its interproximal location, which may be
used to esthetic advantage.
• (2) increased retention without tipping action
on the abutment.
• (3) less chance of accidental distortion
resulting from its proximity to the denture
border.

42. Part3 indirect
retainer and design
principles of RPD

43. Indirect retainer
• Is the component of R.P.D. that assist the direct retainers 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.

45. Principles of Partial Denture Design
• 1. Utilize what's present.
• 2. Plan for the future
• 3. Minimize framework elements whenever possible.
• Cingulum rests can be designed to join proximal plates, rather than
having separate minor connectors, whenever possible.

46. • First step in the RPD design is Surveying
• What is Surveying?
Surveying the cast include:
1-analysing the cast. 2- surveying the teeth.
3-surveying the soft tissue contour on the cast.
-OBJECTIVES

47. • Objectives of Surveying:
• 1.Locating soft tissue undercuts
• 2. Contouring wax patterns
• 3. Machining parallel surfaces
• 4. Blocking out undesirable undercuts
• 5. Placing intracoronal retainers
• 6. Recording the cast position

48. •Denture Bases
• Use broad tissue base support.
• 2. Distal extension bases should be extended to the retromolar
pads and the maxillary tuberosities as these structures provide
comfort and a peripheral seal for retention.

49. • Direct Retainers
Minimize requirements for direct
retention
• .Design retentive clasps tips to be
ideally placed in the gingival 1/3
• Consider caries susceptibility.
• The height of tooth
• If no retentive undercut can be found it
is possible to prepare a small retentive
area on the tooth.

50. • Indirect Retainers
• Class I and Class II partial dentures often require indirect retainers.
These should be as far from the primary fulcrum line as possible
(90°), and placed on the opposite side of the fulcrum line from the
denture base. They are normally not required for tooth-borne RPD’s.
• Major Connectors
• 1. Assess tori, height of floor of mouth, frenal attachments.
• 2. The posterior extensions of a maxillary distal extension framework
should point to hamular
• notches.
• 3. Major connectors should have smooth continuous contours that
flow into other elements of
• the partial denture.

51. • Minor Connectors
• Where a cingulum rest is not adjacent an embrasure minor
connector to an occlusal rest, cross the free gingival margin directly
– do not use an embrasure minor connector. Cover the entire rest
seat preparation, but do not wrap these minor connectors into
embrasures

52. • Distal Extension Case Considerations:
• 1. Use stress releasing direct retainers in distal extension cases.
There are three axes of rotation for these partial dentures. If
abutment teeth are locked into the frameworks they
• can be torqued in many directions. Stress-relieving clasps allow for
some release of the teeth to minimize torquing potential.