Component Parts of A Partial Denture Copyright by Prosthodontic Department, UDM

1. Dr. Khin Than Kyi
Associate Professor
Dept. of Prosthodontics

2. • saddles
• Connectors
• Direct Retainers (clasps)
• Indirect retainers
• Occlusal and incisa rests

3. • Part of a denture which carries the artificial teeth
• Tooth borne or mucosa-borne and different
saddles may occur in the same denture
• Tooth borne saddles are made in metallic alloy
• Mucosa-bone saddles constructed metal or acrylic,
for reason of economy
• The periphery of the denture in the saddle region
should always reach to the functional depth of the
sulcus

4. • A major connector is part of a denture which joins
one saddle to another, a minor connector joins a
clasp, rest or indirect retainer to a saddle
• Major connector Palatal plates and bars
Lingual plates and bars
Labial plates and bar

5. • Should be as thin as possible with the required
strength and should be dammed along free
anterior and posterior borders in order that
– the tongue may pass from mucosa to denture
without encountering an edge
– Food particles may not collect under the
denture
• This damming must not be too deep or too broad
because mucosa covering the bone is rather thin

6. • wider and thinner in section than bars
• transfer some of the occlusal load to the palate
• nonmetallic denture base material is used in
economic point
• do not worry the tongue if thicker

7. • it covers more tissue than a bar

8. • Always made of alloy and should be as thin as
possible commensurate with strength They must
fit the palatal tissue accurately
• In mucosa-bone dentures if may be necessary to
form a relief on the cast
• The position of a palatal bar will very according to
the position of the saddle areas to be connected
and will be in the posterior third of the palate,
middle third or the anterior third

9. • A posterior palatal bar is the most suitable
– is less conspicuous to the tongue
– Fulfils the function of an indirect retainer
– Areas less frequently associated with bony
prominences or with thin mucosa
• A middle palatal bar can seldom act as an indirect
retainer

10. • An anterior palatal bar can be used in conjunction
with a posterior bar to increase the rigidity and
strength of the denture
• It can also act as an indirect retainer and as link to
an anterior saddle from posterior saddles

12. • may be made of acrylic or alloy
• cast alloy plates should copy the anatomical form
of the lingual surface of the teeth and mucosa and
if made thin, are delightfully smooth to the tongue
• act as indirect retainers and provide good bracing
against lateral load

13. • usually made of metal and are used to connect two
lower saddles or one lower saddle with a clasp on
the opposite side
• should be placed midway between the gingival
margins of the teeth and the highest functional
position of the floor of the mouth
• Cast lingual bar is the most satisfactory type

14. • Tissue relief is provided during construction of the
bar by swaging metal foil over the surface of the
cast

15. • Lack of space between the functional position of
the floor of mouth and gingival margins
• Undercut lingual alveolar process
• Lingually inclined teeth
A continuous clasp also known as a continuous
bar, positioned on the cingulae of the incisor teeth
to act as an indirect retainer or supplementary
rest

16. • avoiding coverage of gingival margins but not well
tolerated by the tongue

17. • is an improvement on the lingual bar
- lies in the anterior lingual sulcus,
but more difficult to make
- act as rigid major connector

18. • - kidney shaped in section
- the lingual sulcus is relieved
with 0.06 mm metal foil to avoid
any trauma against the lingual
tissues

20. • always made of cast alloy but are not use as they
tend to worry the patient's lips
• used when lingual inclination of the standing
teeth, presence of excessive lingual under cuts or
problems such as torus mandibularis
• made as broad and as thin as the sulcus depth and
strength

21. • a component of a removable partial denture that
assists the direct retainers in preventing displacem
ent of the distal
extension bases by functioning through lever
action on the opposite side of the fulcrum line
when the denture base attempts to move an
occlusal direction or in a rotational path about the
fulcrum line”( GPT 9)

22. • So called because it retains in position some part
of a denture remote from itself
• It works on the principle of the counter balance
• This principle can be employed in partial dentures
whenever a free end saddle is present and cannot
be retained adequately by the clasp fitted to the
abutment tooth

23. It shifts the fulcrum line away from the
point of application of the force, there by
counteracting the lifting force and
stabilizing the denture

24. • Reduces the antero-posterior twisting leverage
• Helps stabilization
• Acts as a guiding plane
• May act as auxiliary rest to support major
connector
• It counteracts horizontal force by providing
support and stability to the denture

25. • Indirect retainers are best made of cast alloy as
part of a major connector so that they fit the teeth
accurately and appear as unobtrusive as possible
• An occlusal or incisal rest or various parts of a
denture may act as an indirect retainer

26. The important points are :
- They should be used only in periodontally sound
teeth
- The should contact as many teeth as possible to
reduce the possiblity of moving teeth by the
application of excessive forces
- Extension of the denture base on mucosa are
effective provided the mucosa is firm
- The can only function in conjunction with direct
retainers (clasps)

28. • The forces acting on the occlusal surface of a partial
denture must be absorbed by the alveolar bone
• If the area of mucosa covered by the denture is sufficiently
large, forces will be absorbed by the soft tissue and
transmitted to the bone
• If the area of a partial denture is small, the force applied to
unit area of the soft tissue will be above its tolerance and
pain and ulceration will ensue with destruction of hard and
soft tissue

29. • Transferring the occlusal loads to the bone are
required
• The parts of the denture which transmit the loads
to the teeth are called supporting elements or rests
• The main function of rest is to transfer some or all
of the clenched and masticatory loads to the
natural teeth

30. • Other 4 important functions are
- act as contact points and prevent food packing
between the denture and the natural tooth
- maintain clasps in their correct position and
prevent them sinking and pressing into the
gingival tissues
- act as indirect retainers
- assist in bracing against lateral movement

32. • These are made to fit into a mesial or distal fossa
on the occlusal surface of a tooth
– They must fit the tooth accurately in order to
minimize the collection of food debris beneath
them and also to locate them correctly in
relation to the tooth
– They must be strong enough to bear all normal
masticatory and clenched loads without
deformation

33. • They must not interfere with the occlusion
• They must transmit the stress down the long axis
of the tooth without damage to the periodontal
membrane
• They must be at right angles or less to the long
axis of the tooth

34. • Lie on the palatal or lingual surface of anterior teeth
• They are often unsatisfactory because the shape of
the palatal surfaces of most teeth is not suitable to
carry a rest
• Rest seats must be prepared in most anterior teeth
• The rest must not interfere with the occlusion,
particularly in lateral and protrusive positions
• Cingulum rest can be used on maxillary canines or
central incisors and mandibular canines

35. • Rest seats on anterior teeth may be cut on the
incisal edges, in the semilunar shape occurpying
only the lingual part of the incisal edge
• On maxillary laterals and mandibular incisors,
where the incisal edges are thin, effective support
is gained by notching the mesial or distal corner to
create a rest seat about 1 mm wide and 1mm deep
• The rest must not interfere with occlusion

36. A partially edentulous mouth has undercut areas
which result from
• The naturally bulbous shape of the crowns of the
teeth
• The long axes of the teeth are inclined at an angle
to a vertical taken from the occlusal plane
• The soft tissue and underlying bone being inclined
at an angle to a vertical taken from the occlusal
plane

37. Rigid denture bases and the rigid parts of clasps will
not pass into undercuts
An undercut - an area which is out of contact with
any vertical dropped from a given
horizontal
Surveying is the determination of the
undercut areas on the cast by using
surveyors
Such undercut areas are found in the maxillary labial
and tuberosity region, lingual alveolar region of the
mandible

39. • It enables undercuts to be accurately blocked out on
the cast to the acrylic procession or alloy casting of
the denture, so that of the base not fill the undercuts
and prevent the denture from being inserted
• It marks the most bulbous part of a tooth which is to
carry a clasp This enables to place the rigid part of
the clasp above the undercut area and the flexible
arm which retains the denture into the undercut

40. • It will demonstrate undercut areas which can be used for
the retention of the denture
• It enables these parts of the denture base which fit against
the crown of the teeth to be placed above the survey line,
that the denture fits snugly against the tooth and prevent
food stagnation
• It permits the dentist and technician to design a denture
with one path of insertion, so that all saddles and clasps
are related to this predetermined path, and not as
individual units

41. • It will demonstrate undercut areas which can be used
for the retention of the denture
• It enables these parts of the denture base which fit
against the crown of the teeth to be placed above the
survey line, that the denture fits snugly against the tooth
and prevent food stagnation
• It permits the dentist and technician to design a denture
with one path of insertion, so that all saddles and clasps
are related to this predetermined path, and not as
individual units

42. • It enable the dentist and technician to measure,
with undercut guages, the horizontal depth of an
undercut below the survey line marked on a tooth
and determine the type of clasp to be used and the
material of which it is constructed

43. • Partial dentures obtain their retention mainly
from clasp (direct retainers) attached to the
denture which embrace natural teeth and hold the
denture in place
• A clasp consists of a resilient metal projection
from the denture which grips the natural tooth
and retains that part of the denture, to which it is
attached, in its functional position

44. 2 main types
• Encircling or occlusally approaching clasps
• Projection or gingivally approaching clasps

45. • These consists of two arms which encircle the
tooth on opposite side and are in contact with it
along their whole length, gripping it at their
extremities.

46. • These differ from the encircling type by not being
in contact with the tooth along their whole length
and by approaching the undercut area from the
gingival aspect

47. • The encircling clasp is superior to the projection
type They are
– The rigid part of the clasp which is in contact
with the tooth provides valuable bracing for the
denture against lateral movement
– It holds the minimum of food debris in contact
with the teeth

48. • The value of projection clasp is
– They can be used in situations unfavourable to
the use of encircling clasps
– Any degree of flexibility can be obtained by
lengthening the arm
– They are often less conspicuous
– They can be placed in the area of the greatest
undercut
– They can be used as stress breakers

49. • The selection of the clasp mainly depends on the
type of survey line Other factors are
– The position of the tooth
– The occlusion of the teeth
– The appearance

50. • Encircling clasps
• Two-arm encircling clasp
– The normal arm can be employed whenever the
tooth to be clasped is adjacent to an edentulous
space and the survey line on that part of the
tooth nearest to the space allows rooms for the
rigid part of the clasp
– The flexible terminals of the clasp travel for as
long a distance as possible in the undercut area

52. Two-arm encircling clasp. The tip should travel in
the undercut area for as long a distance as possible.

53. – The recurve arm clasp the length of the arm is
increased by curving in on itself
– The length of the retentive terminal to be
increases and brings it nearer to the denture so
providing superior retention
– The length of the rigid part is also increased and
provides excellent bracing

54. Recurved arm encircling clasp

55. • Only one arm is flexible, the other arm or
reciprocal, being formed by an extension of the
denture
• The formed of the single arm may be normal or
recurved

56. One-arm clasps reciprocated by
mucosaborne denture base

57. • employed on isolated teeth
• it provides excellent bracing

58. Ring clasp

59. • This is similar to the ring clasp except that it is
attached to the denture by a mean of strut placed
anterior or posterior to the saddle on the lingual
or palatal side

60. Back action clasp with occlusal rest.
Clasp is attached to denture at A

61. • This clasp is a completely encircling clasp with no
free flexible terminal
• It provides retention by gripping the undercut
areas in proximal embrasures of tooth

62. Diagram of Jackson crib clasp reciprocated
by denture base

63. • This clasp has two forms
• The first consists of a round wire which has been
fused at the end to form a ball
• The second is a small triangular wedges or two
clasp arms
• This clasp are employed when no edentulous gaps
exists between the teeth

64. Ball-ended interdental clasp,
usually made of wrought alloy

65. Interdental clasps, usually cast, either ending in
a wedge or spreading into two buccal arms

66. • It is used when the survey line indicates that no
room exists for the rigid part of an encircling clasp
and yet there is a large undercut area
• On canine and incisor

67. T-shaped projection clasps on anterior teeth
(diagrammatic).

68. T-shaped projection
(gingivally-approaching) clasps

69. • This clasp is useful when the survey line dips to
the gingival margin on the buccal aspect of the
totoh of molars

70. U-shaped projection clasp

71. • This clasp is usually employed on premolar or
canine when the survey line is extremely small

72. L-shaped projection clasp

73. • This clasp is used when a tooth exhibits only a
small undercut area mesially or distally

74. C-shaped projection clasp

75. • This clasp is used when the slope of the tooth
surface is no undercut area exists
• This clasp gives a very positive retention and need
not be restricted to teeth which exhibit no survey
line
• Tooth bone denture require clasps at the ends of
all saddles

76. • When only two clasps are used, a straight line
joining them should bisect the denture as nearly as
possible
• If a denture would tend to rock about two clasps,
then a third clasp should be added and the father
it is away from the other two the better

77. Ball and socket projection clasp

78. • Molars
• Premolars
• Canines
• Incisors

80. Location of clasps

81. Location of clasps:
Kennedy class upper

82. • The rigid portion must be on the occlusal side of
the survey line
• At least part of the flexible portion must rest in an
undercut area
• The flexible portion must not fit more deeply into
an undercut area than its elastic or proportional
limit will permit

83. • The tip of the clasp must remain in contact with tooth
• Any pressure must be opposed by equal ie, a clasp
must never press on one side only of an unsupported
tooth
• The clasp together with its rigid opponent or
reciprocal, must embrace more than half the
circumference of the tooth
• Unless fitted with an occlusal rest the clasp must not
rest too near the gingival margin

84. 1. Clean
2. Minimum friction
3. Highly flexible
4. Easily constructed
5. Suitable for cases requiring several clasps
6. Do not transmit every movement of the pressure
to the tooth

85. 1. Accurate fitting
2. Easily varied in thickness
3. Easily formed to act as a rigid bracing or
reciprocal
4. Easily include an occlusal rest
5. Can be cast as part of denture base