REMOVABLE PARTIAL DENTURES IN PROSTHODONTICS

A removable partial denture (RPD) is a denture for a partially edentulous patient who desires to have replacement teeth for functional or aesthetic reasons and who cannot have a bridge (a fixed partial denture) for any reason, such as a lack of required teeth to serve as support for a bridge (i.e. distal abutments)

1. REMOVABLE PARTIAL
DENTURE

RPDs are components of prosthodontics
( branch of Dentistry) pertaining to the
restorations and maintenance of oral
function, com poe appearance, and
health of | the( pt) by replacement the
missing teeth and craniofacial tissues

„with artificial substitute

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The Basic Objectives of
prosthodontic Treatment

. Elimination of oral disease.
, Preservation of the health and

relationship of the teeth, and the
health of the oral and para-oral
structure.

. Restoration of oral function (comfort,

esthetic, speech).

3. Consequences of Tooth Loss

Aesthetics

Speech.

Drifting, tilting, over-eruption.
Loss of masticatory efficiency.
Loss of vertical dimension.
Deviation of mandible.

Loss of alveolar bone.

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P.D may:

Give support to periodontally diseased teeth.
Restore vertical facial dimension.

Prevent T.M.J problems.

Prevent tooth drifting or over eruption.
Stimulate non-used tissues.

Support collapsed structure (muscles of lips
and cheeks).

Prevent attrition of remaining teeth.

Improve oral hygiene by preventing stagnation
of food in disused areas.

5. Classification Of Partially
Edentulous Arches

= The most familiar classification are those
proposed by Kennedy, Cummer, and
Bailyn, Beckett, ...

= The recent classification has been
proposed for partial edentulism that is
based on diagnostic criteria.

6. 3.

Requirement Of an Acceptable
Method Of Classification

It should permit immediate visualization

of the type of partially edentulous arch.

It should permit immediate
differentiation b/w tooth- supported and
the tooth and tissue-supported.

Universally acceptable.

7. Kennedy Classification

= 4 basic classes.

m Edentulous areas other than those
determining the basic classes were
designated as modification spaces.

Class I : Bilateral edentulous areas located
posterior to the natural teeth.

Class II : A unilateral edentulous area
posterior to the remaining natural teeth.

8. Kennedy Classification

Class III: Unilateral edentulous area with
natural teeth remaining both ant and post
to it.

Class IV : A single, but bilateral (crossing
the midline), edentulous area located
anterior to the remaining natural teeth.

9. Principal Advantage

= It permits immediate visualization of the
partially edentulous arch and allows easy
distinction b\w tooth-supported versus
tooth-tissue supported prostheses.

10. Applegate's Rules for Applying
the Kennedy Classification

Rule 1 : The classification should follow, not
precede extractions.

Rule 2 : If a 3 molar is missing and not to
be replaced, it is not considered in the
classification.

Rule 3 : If a3rd molar is present and not to
be used as an abutment, it is not
considered in the classification.

11. Applegate's Rules

Rule 4 : If a 2% molar is missing and not to
be replaced, it is not considered in the
classification.

Rule 5 : The most posterior area always
determines the classification.

Rule 6 : Edentulous areas other than those
determining the classification are referred
to as modifications and designated by
their No.

12. Applegate's Rule

Rule 7 : The extent of the modifications is
not considered, only the No. of additional
edentulous areas.

Rule 8 : There are no modification in Class
IV.

13. Principal Of Partial Denture
Design

Stresses acting on RPDs are transmitted
to the teeth, and to the tissues of the
residual ridges.

The stresses, which tend to move the PD
in different directions are:

. Masticatory stress( Tissue ward movt).
. Gravity( Tissue away movt).

. Sticky food pull the denture occlusaly
(Tissue-away movt).

14. 4. Muscles and tongue tend to displace
denture from its foundation.

5. Intercuspation of the teeth may tend to
produce horizontal and rotational
stresses unless occlusal is adjusted.

15. Properly Constructed PD Must
:Have

i. Support: Resistance to vertical seating
forces( provided by teeth and mucosa).

2. Retention: Resistance to vertical
displacing forces.

3. Stability( bracing) resistance to
horizontal and lateral displacement.

= All the above should be within the
physiological limits of the tissue involved.

16. Designing Support

. Tooth support: When abutment teeth available

at both ends of the denture base( bounded
saddle). It most commonly obtained by
occlusal rests.

. Mucosa support: (mucoperiosteum covering
residual alveolar bone). It allows varying
degree of displacement.

The amount of displacement( tissue ward
movt) will depend on:

The amount of pressure applied.
The nature of the mucosa (thickness).

17. 3. Area covered by the denture( the wider
the area the less the displacement).

4. Fit of the denture base.

5. Type of impression( anatomical,
functional, or selective pressure).

c. Tooth-mucosa support: ( Bilateral free
end saddle).

= Posterior tissue support, and anterior
tooth support.

18. Designing Retention

™ Retention should be designed to counter act
dislodging forces( sticky food, muscle at
periphery of the denture, intercuspation,
gravity).
= Retention is gained by mechanical means
1. direct retainers:
a. Intercoronal( clasps).
b. intracronal(percision attachment).
2. Indirect retainers.

19. = Physical factors( cohesion, adhesion,
atmospheric pressure, surface tension). it
play a minor role RBD.

20. Designing Bracing and Stability

= Bracing( providing resistance to lateral
movt.of RBD).

= Causes of tipping, rocking and
rotation of P.D.

3. Quality of supporting structure.

21. 2. The tissue-ward movt. Of the free end
base create an axis of rotation around
which this appliance is rotated.

This axis of rotation is called a fulcrum line
(it is imaginary line extending between
the two main abutment.

22. How to counteract lateral shifting?

i. Bracing the sides of the teeth by means
of rigid clasp arms.

2. Use of continuous bar resting on the
lingual surfaces of the natural standing
teeth.

23. Se O

Components Of RPDs

Major connectors.

Minor connectors.

Rests.

Direct retainers.

Stabilizing or reciprocal components
(part of clasp assembly).

Indirect retainers( if prosthesis has distal
extension).

24. Major Connecters

= Major connector is component of the PD
which connect all parts of the prosthesis
directly or indirectly.

= It provides the cross-arch stability to help
resist displacement by functional stresses.

25. Characteristics Of Major Connectors

1.

Made from material compatible with oral
tissue.

It is rigid.

Doesn't alter the natural contour of the
lingual surfaces of the mandibular
alveolar ridge or of the palatal vault.
Doesn't impinge on oral tissue in
(insertion, withdrawal. Or in function).

26. 6. Cover no more tissue than is absolutely
necessary.

7. Doesn't contribute to the trapping of food
particles.

8. Has support from other elements of the
frame work to minimize rotation in
function.

9. Contribute to the support of the
prosthesis.

27. oo CN 7

a

Mandibular Major Connectors

Lingual bar.

Linguoplate.

Sublingual bar.

Lingual bar with cingulum bar (continuous
bar).

Cingulum bar (continuous bar).

Labial bar.

Lingual bar and Linguopslate are most
common used.

28. 1. Mandibular lingual Bar

Indication: Where sufficient space exist

b/w elevated alveolar lingual sulcus and

the lingual gingival tissue.

Location:

. Half-pear shaped, with bulkiest portion
inferiorly.

Superior border tapered, located at least

4mm inferior to gingival margin.

29. 4. Inferior border located at site of the
alveolar lingual sulcus where the pt’s
tongue is elevated.

= Finishing line: Butt-type joints with minor
connector for retention of denture base.

30. .2Mandibular Sublingual Bar

“It is modification of lingual bar used when
the existing space not allow placement of
lingual bar.

= The shape remain the same but placement
is inferior and posterior to site of lingual
bar.

31. = Contraindication:

Remaining natural anterior teeth severely
tilted toward the lingual.

= Characteristics and location:

4. Half-pear shaped same like the lingual
bar except that the bulkiest portion is
located to the lingual and the tapered
portion is toward the labial.

32. 2. The superior border of the bar should be
at least 3mm from the free gingival
margin of the teeth.

3. The inferior border is located at height of
the alveolar lingual sulcus when the pt‘s
tongue is elevated.

4. Functional impression is most.

u Finishing line: Butt-type joints with minor
connectors for retention of denture base.

33. .3Mandibular Linguoplate

Indication for use:
No sufficient space for lingual bar.

. The residual ridge undergone a vertical
resoption which offer minimal resistance
to horizontal rotation.

Periodontally weakened teeth.

5. When future replacement of one or more

incisor teeth will be facilitated.

34. Characteristics and location:
Half-pear shaped with bulkiest portion located.

Thin metal apron extending superiorly to
contact cingulum of ant. Teeth.

Apron extended interproximally to the height
of contact points.

Inferior border at ascertained height of the
alveolar lingual sulcus where the pt’s tongue
is slightly elevated.

35. .4Mandibular Lingual Bar with
(Continuous Bar( Cingulum Bar

= Indication for use:

2. When Linguoplate is indicated but the
axial alignment of ant. Teeth prevent .

3. When wide diastema b/w mandibular
ant. Teeth.

36. Characteristics and location:

. Shaped and located same as lingual bar.
. Thin, narrow(3mm) metal strap located
on a cingula of anterior teeth. Scalloped
to follow interproximal embrasures.

. Originated bilaterally from incisal, lingual,
or occlusal rests of adjacent principal
abutment.

37. Mandibular Labial Bar .5

Indication for use:

. When a lingual inclination of remaining
MPM and incisors teeth cannot be
corrected.

. Severe lingual tori cannot be removed.
. Severe tissue undercut.

38. Characteristics and location:

Half -pear shaped with bulkiest portion
inferiorly located on the labial and buccal
aspect of the mandible.

Superior border tapered to soft tissue.
Superior border located at least 4mm inferior
to labial and buccal gingival margins and more
if possible.

Inferior border located in the labial buccal
vestibule.

39. Maxillary Major Connectors

A. Single palatal strap

3.
Ar

5:

Characteristics and Location:
Anatomic replica form.

Ant. Border follow the valleys b/w rugae at
right angle to median suture line.

Posterior border at right angle to median
suture line,

Strap should be 8mm wide.

Confined with in an area bounded by the four
principal rests.

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SINE IE

. Single Broad Palatal Major
Connector

Indication:

Class I.

V or U shaped palate.
Strong abutments.

6 remaining ant teeth.
No interfering tori.

41. = Characteristics and location:

2. Anatomic replica form.

3. Anterior border following valleys of rugae
and at right angle to median suture line
and extending anterior to occlusal rests
or in direct retainer.

42. 3. Posterior border located at junction of
hard and soft palate. And extended to
pterygomaxillary notches.

43. C. Anterior-posterior Strap

a
3:
4.

Indication:
Class I and II.

Long edentulous span class IIMOD 1
arches.

Class IV.
Palatal tori.

44. Characteristics and location:

Parallelogram shaped and open in center

portion.

Relatively broad(8-10mm) ant. And post.

Palatal strap.

. Lateral palatal strap (7-9mm) parallel to
curve of arch. 6mm from gingiva of

remaining teeth.

45. 4. Anterior palatal strap; ant border not
placed further interiorly than ant rests and
never closer than 6mm to lingual gingival
cervices.

46. D. Complete Palatal Coverage

Indication for use:

3. Situation in which only some or ant teeth
remains.

4. Class II arch with large posterior
modification space and some missing
anterior teeth.

47. 3. Class I arch with 1-4 PM and some or all
ant teeth remaining, abutment support is
poor, residual ridge extremely resorbed,
direct retention is difficult to obtained

4. No tori.

48. Characteristics and location:

Anatomic replica form supported anteriority by
rests seats.

Palatal Linguoplate supported anteriorly and
designed for the attachment of acrylic resin
extension posteriorly.

Contact all of the teeth remaining in the arch.
Posterior border, terminates at the junction of
the hard and soft palate, extended to hasmular
notch areas.

49. D. U-shaped Palatal Major Connector

m Is used only in which inoperable tori
extended to the posterior limit of the hard
palate.

™ It is the least favorable design of all
palatal major connector( lack rigidity).

50. Rests and Rest seats

= Vertical support provided by rests
(occlusal, incisal, or cingulum).

= Rests located on properly prepared tooth
surface .

= The prepared surface of an abutment to
receive the rest is called the rest seat.

51. Cal ge Lo le

The primary purpose of the rest is to provide
vertical support for PD. It also does the
following:

Maintain components in planned position.
Maintained established occlusal relationship.
Prevent impingement of soft tissue.

Direct and distribute occlusal loads to
abutment teeth.

52. Form Of Occlusal Rest and Rest
Seats
1. The outline form of the occlusal rest
should be rounded, triangular shaped

with the apex toward the center of
occlusal surfaces.

2. It should be as long as it is wide. The
base is 2.5mm for M and PM.

3. Reduction in marginal ridge is 1.5mm.

53. 4. It should be concave and spoon shaped
(no sharp edges or line angle).

5. The angle formed by the occlusal rest and
the vertical minor connector from which
its originate should be less than 90*.

54. Extended Occlusal Rest

= In mesially inclined abutment the rest
extend more than one half of the mesio-
distal width.

= In severely tilted abutment the extended
occlusal rest may take the form of an only
to restore the occlusal plane.

55. = Interproximal Occlusal rests.

= Intra-coronal Rest: It is used for both occlusal
support and horizontal stabilization.
Horizontal stabilization is derived from the near
vertical walls of this type of rest seat.

= The form of the rest should be parallel to path of
placement, slightly tapered occlusaly, and
slightly dove-tailed to preve3nt dislodgement
proximally.

56. = The main advantages of the internal rest
are that it facilitates the elimination of the
visible clasp arm.

57. Direct Retainer

It is a clasp or attachments applied to an
abutment tooth for the purpose of holding RPD
in position.

Classification:

Extracronal direct retainer) casted clasp,
wrought wire clasp).

a/ Occlusaly approaching clasp
(circumferential)

b/ Gingivally approaching clasps (Bar clasps)

58. 2. Intracronal direct retainer( attachments):
a/ Internal attachment.
b/ External attachment.
c/ Special attachment.

= Component parts of the clasp:

1. Retentive terminal 2. Retentive arm

3. Reciprocal arm 4. Occlusal rest

5. Shoulder 6. Body 7. Minor connector

59. Height of contour: is greatest convexity
of tooth.

The basic principle of clasp design is
encirclement to obtain more than 180* of
continuous contact.

Types of cast Circumferential clasps:
Simple circlet clasp: widely used, tooth
supported PD, approach the undercut
from edentulous space. Not used for
distal extension.

60. 2. Reverse clasp.

3. Multiple circlet clasp( combination of two
circlet clasps).

4. Embrasure clasp

5. Ring clasp; no buccal undercut. Isolated
abutment, lingually tipped molar, from
disto- buccal to disto-lingual undercut.

6. Hairpin clasp. when undercut is near to
edentulous space.

7. Combination clasp.

61. = Bar clasp: Composed of two parts
( Gingivally approaching and retentive
tip)

2. Approach arm: It is a minor connector.
Semi circular in cross section, cross the
gingival margin at right angle.

3. Retentive terminal : it should end below
undercut.

62. Advantages:

2.
3.

Easy to insert and difficult to remove.

More aesthetic, cover less tooth
structure.

Types of Bar clasps:

. T-Bar clasp.
. Y- Bar clasp.

I- Bar clasp.

63. Indirect Retainer

= Apart of RPD which assists the direct
retainers in preventing displacement of
distal extension denture base by
functioning through lever action on the
opposite side of the fulcrum line.

64. = Types of indirect retainer:

2. Auxiliary occlusal rest, most frequently
used, located far as possible from distal
extension base, placed perpendicular to
the mid point of the fulcrum line. If this
perpendicular line ends on the incisal
area it is a voided, instead it transfers to
PM in both sides.

65. 2. Canine extension from occlusal rest,
finger like extention(lug seat) from the PM
rest is placed on the lingual slope of
adjacent canine.

3. Canine rest.

4, Continuous bar retainers and Linguoplate.

66. Denture Base

Denture base defined as that part of a
denture which rests on the oral mucosa
and to which teeth are attached.

Ideal requirements:

. Accurate tissue adaptation with minimal
change in volume.

. Thermal conductivity.

. Sufficient strength to resist fracture or
distortion under function.

67. 4. Cleansability.

5. Ability to be relined if necessary.
6 Cost effective.

7. Low specific gravity.

8. Ability to achieve a good finish.

68. as WS |

Types of denture base:

Acrylic

Metal.

Combination.

Acrylic Resin denture base; mainly used
for distal extension PD- attached to the
frame work by minor connector-with
1.5mm thick to have a adequate
strength.

69. Advantages:

. Anterior teeth can be replaced at their
original position (aesthetic level).
Restore the contour of the edentulous
ridge.

Brings out the normal contour of the lip
and cheeks.

Can be relined.

70. Disadvantages:

. May break on usage.

. Tend to accumulate mucous deposits
and food debris.

. Soft tissue irritation.

5. Allergy.

71. aw + | |

Metal denture base: mainly used for tooth
supported PD.

Advantages:

Accurate tissue adaptaion( better retention).
Easy to clean.

Strong even in thin section.

Heat conductivity( physiologic tissue
stimulation).

72. Se Se

Disadvantage:

Difficult to trim and adjust.

Over extension can injure the soft tissue.
Poor aesthetic.

Difficult to reline and rebase.