Major Minor Rest Direct Indirect Retainers

1. Major and Minor Connectors,
Rest and Rest Seats, and
Direct and Indirect Retainers
Ammar G. Salem KHBMS 4th Year

3. Major Connectors
They unit the major parts of the RPD framework
prosthesis
It provides cross-arch stability to help resist
displacement by functional stresses

4. Should not
substantially alter
the natural
contour of lingual
surface or palatal
vault
It should be
uniform for better
stress distribution
Guidelines Regarding Major Connector
Rigidity Relief
Uniformity Contour
Flexible Major
connector is
ineffective and
detrimental
Avoid impinge on
gingival tissue,
bony or soft
tissue prominence
01 02
04 05
Should not
contribute to food
trapping
Design
Cleansing
Reuqire proper
shape, thickness
and location
03
06

5. Mandibular Major Connectors
Lingual Bar
Linguoplate
Sublingual Bar
Lingual Bar with Cingulum Bar
Cingulum Bar
Labial Bar

7. Lingual Bar
Most common used.
● Cross-section is half pear shaped.
● Tapered superiorly and bulk inferiorly.
● Recommended placement as inferior as
possible.
It is recommended that superior border is
minimum 4mm below gingival margin.

8. Linguoplate
Need terminal rest at each end.
It should be contoured to follow nature of teeth
and embrasures.
Overlapped teeth need lingual proximal surfaces
recontouring.
● High frenum attachment, slightly elevated
floor.
● Class I with excessive vertical resorption.
● Stabilization of periodontally weakened teeth.
● When future replacement is expected.

9. Design of Mandibular Major Connectors
Step 4
Connect basal seat
area to inferior and
superior borders of
major connector and
add minor connectors
to retain acrylic resin
denture base.
Step 2
Outline the inferior
border of major
connector
Outline the superior
border of major
connector
Step 3
Step 1
Outline basal seat
areas

11. Cingulum Bar and cingulum with lingual
bar
when Linguoplate indicated but lack axial
alignment of anterior teeth, in case of excessive
block-out of interproximal undercuts must be
made.
● Located slightly above or on cingula.
Acceptable esthetic in wide diastema than
Linguoplate.

12. Labial Bar
In case of extreme lingual inclination of remaining
lower premolar and incisor teeth.
● Can be avoided by recontouring or reshaping
by means of crowns.
Also when lingual tori is inoperable.

13. Swing Lock Design
Consist of labial bar connected to major
connector by a hinge at one end and a latch at the
other end and supported by multiple rests and
stabilized by Linguoplate and retention by struts.
● Contraindicated in: poor oral hygiene, lack of
plaque control, shallow labial vestibule, high
frenum.
● Indicated in missing key abutments (canine),
unfavorable tooth and soft tissue contours,
teeth with questionable prognosis.

14. Maxillary Major Connectors
Single palatal strap
Combination anterior and
posterior palatal strap
Palatal plate
U shaped plate
Signle palatal bar
Anterior posterior palatal bar

15. Single palatal strap
In bilateral tooth supported particularly when short
spaces are posteriorly positioned.
In Class II with cross-arch attachment by
extracoronal retainers or internal attachments.

16. Anterior-Posterior palatal Strap
Almost any design of Class II and Class IV
● Anterior component better to avoid rugae
coverage, posterior to crest or in the valley.
● Posterior component should be flat, minimum
width 8mm, avoiding tongue interference and
anterior to vibrating line.
● Should form square, rectangular form.

17. Palatal Plate
Require anatomic replica and uniform thickness.
● Used in Class I when last abutment is canine
or 1st premolar with excessive vertical ridge
resorption.
● Two or more edentulous areas.
In form of complete plate or partial plate.

18. Palatal Plate

19. Design of Maxillary Major Connectors
Step 1 Step 2
Outline primary
stress bearing areas
Outline non-bearing
areas
Step 3
Outline connector
areas
Step 4 Step 5
Selection of
connector type
Unification

21. U-shaped Palatal Connector
Least desirable.
● In case of large inoperable torus and
replacement of multiple anterior teeth.
It lacks rigidity, fail to support well, and bulkiness
hinder the tongue.
Should be supported by rests and being away
from gingival tissue.

22. Single Palatal Bar
Highly objectionable.
Need bulk and being centered.

23. Minor Connectors
They connect the major connector to other
components of framework.
(prosthesis to abutment function): transfer
functional stress to abutment teeth and
underlying tissue.
(abutment to prosthesis): transfer effect of
components throughout prosthesis.

24. Minor Connector: form and location
Bulk Convex surface
For rigidity
When contacts axial
surface of abutment
In embrasure
For tongue
interference
Pass vertical Tapering
Should cross abrupt
Toward contact area

25. junctions should be strong butt joint without much bulk.
Angle not more than 90 degrees.
Open latticework/ladder type is preferred.
On mandible extending 2/3rd length of residual ridge,
while on maxilla extending entire length.
On mandible should extend buccally and lingually to
minimize distortion of resin during processing.
Denture base minor connector

26. • Integral part for retention of acrylic resin bases.
• Provide stability for framework during transfer and
processing.
• Prevent distortion during resin processing.
Tissue Stop minor connector

27. • Medial extent depends on later extent of major
connector.
• Too far medial position alter the natural contour.
• Too far buccal position make difficult to create
natural contour of acrylic resin on lingual surface
of artificial teeth.
• Best line is 2mm medial to imaginary line
contacting lingual surfaces of missing posterior
teeth.
Finishing Lines of minor
connector

28. Rest and Rest Seat
Any component that provide vertical support on
tooth surface for denture.
Must be rigid
Can be:
Occlusal – Lingual - Incisal

30. Occlusal Rest
● Conventional.
● Extended.
● Interproximal
● Internal

31. Guidelines
● Outline rounded triangular
with apex toward center of
occlusal surface.
● The base at marginal ridge
at least 2.5mm.
● Lower marginal ridge to
permit bulk of metal (1.5mm)
● Floor seat should be apical
to marginal ridge, concave
spoon shaped.
● Angle between rest and
vertical minor connector not
less than 90 degrees.

32. Extended occlusal rest
Recommended in Class II modification 1 and Class
III where most posterior abutment is mesially
tipped molar.
● > half of mesiodistal width.
● 1/3rd of buccolingual width.
● Minimum 1mm thickness of metal.
Purpose to minimize tipping and ensure forces to
long axis of abutment.

33. Interproximal occlusal rest
Similar to occlusal rest seats with exception of
lingual extension.
● Avoid reducing or eliminating contact points.
● Analyze possible interocclusal interference.
● Avoid creation of vertical groove.

34. Internal occlusal rest
Entirely supported by cast retainers.
● Provide support and stabilization.
● Form parallel to path of insertion, slightly
tapered occlusally, and dovetailed.
● Only for tooth supported RPD.
Eliminate visible clasp arm buccally and enable
rest to more favorable location.

35. Rest Preparation
First altering
proximal tooth then
start rest
preparation
Large round bur used
to lower marginal
ridge and establish
outline form
Smaller round bur
used to deepen the
floor

36. Lingual Rest
Used for support an indirect retainer or auxiliary
rest.
● Canine preferred.
● Preferred over incisal rest due to proximity to
center of rotation which reduce tipping.
Maybe placed at cingulum or just incisal to it.

37. Preparation of lingual rest
● At junction of gingival
and middle 3rd.
● Apex incisally.
● Prepared by inverted
cone diamond with
progress to smaller
taper stones with round
ends
● Avoid enamel undercut.
● Floor seat toward
cingulum rather than
axial wall.
Slight rounded V

38. Lingual Rest
● Especially for mandibular
canine due to too steep
lingual inclination.
● Using Cr-Co rest seats
cemented by resin
cement.
On cast crown

39. Incisal rests
Must be placed at incisal angles and used as
auxiliary rest or indirect retainers.
● Least desirable.
● Applicable to mandibular canine.
● Preferrable to ¾ crown.

40. Preparation of Incisal rest
● Form rounded notch at
incisal angle.
● Deepest portion is apical
to incisal edge.
● Notch should be beveled
labially and lingually.
● 2.5mm wide.
● 1.5mm deep.

41. Direct Retainers
Components which resist movement away from
the teeth/tissue.
Greatly influenced by stability and support
provided by other components.

42. Basic Principles of Clasp Design
● Principle of encirclement: >180 degrees in greatest
circumference of the tooth.
● Engagement in two forms:
○ Continuous contact (circumferential clasp)
○ Discontinuous contact (bar clasp)

43. Basic Principles of Clasp Design
● Occlusal rest should prevent movement of clasp
arm toward cervical direction.
● Each retentive terminal should be opposed by
reciprocal terminal.
● Clasp retainers on abutment adjacent to distal
extension bases should act as stress breakers by
design or construction.

44. Basic Principles of Clasp Design
● Retentive clasps should be bilaterally opposed to
control path of removal and stabilize against
rotational movement.
● Path of escapement for each retentive clasp
terminal must be other than parallel to path of
removal.

45. Basic Principles of Clasp Design
● The amount of retention should be always minimum
necessary to resist reasonable dislodging forces.
● Reciprocal elements should be at junction of
gingival and middle 3rd of abutment, while the
terminal retentive arm placed in gingival 3rd of
crown.

46. Reciprocal Arm
● Resist movement in response to deformation of
the retainer arm as it engages a tooth height of
contour.
● Aid in stabilizing against horizontal movement.
● May act as indirect retainer only when it rests on
suprabulge surface of abutment anterior to fulcrum
line.

47. Types of Direct Retainers
Intracoronal Extracoronal
Uses mechanical
resistance to
displacement
through
components
placed to external
surface of
abutment
Maybe cast or
attached within
restored natural
contours of
abutment

49. Principal forms of extracoronal retainer
Clasp retainer Interlocking
Most common.
Retain through
flexible clasp arm
engaging external
sruface of abutment
in area cervical its
greatest convexity.
Attahcments
engages tooth
contour to resist
occlusal displacment
spring loaded device
Clips or Rings
Flexible clips or rings
engaging rigid
component that is
cast or attached to
external surface of
abutment.

50. Clasp Assembly
Reciprocating
Arm
For stabilization
against horizontal
movement
Retentive
Arm
Engages a tooth
undercut
Minor
connector
From which clasp
originate
Principal
Rest
Direct stress
along long axis of
tooth

51. Clasp Assembly

52. Types of Clasp Assemblies
Designs to
accommodate
functional movement
RPI
RPA
Bar Clasp: T, modified T, I, and Y
Designs without
movement
accommodation
Circumferential clasp
Ring Clasp
Embrasure Clasp

53. RPI and RPA
They address class I lever changing fulcrum point.
It belongs to mesial rest concept.
To avoid harmful tipping and torquing on abutment
either:
- Change fulcrum location (mesial rest concept)
- Use of flexible arm (wrought wire)

54. RPI
RPI consist of:
- MO rest with minor connector into ML
embrasure not contacting adjacent tooth.
- Distal guiding plane from marginal ridge to
junction of middle and gingival 3rd
- I bar in the gingival 3rd of buccal of abutment.

55. RPA and Bar clasp
Used instead in case:
- Exaggerated buccal or lingual tilts.
- Severe tissue undercut.
- Shallow buccal vestibule.
Bar clasp classified by shape:
- T
- Modified T
- I
- Y

56. Bar clasp
Indications:
- Small degree of undercut in cervical 3rd.
- Abutment teeth for tooth supported or
modification areas.
- Distal extension base.
- Esthetic considerations.
Alternatives:
- Mesial originating ring clasp
- Cast clasp
- Wrought wire clasp
- Reverse action clasp

58. Combination Clasp
Reducing the effect of class I lever in distal extension by
using flexible component in resistance arm.
- Wrought wire retentive arm
- Cast reciprocal arm originating gingivally from denture
base.
- When mesial undercut exist and I bar not indicated.
Indications:
- Maximum flexibility desired.
- Weak abutment and bar contraindicated.
- Desired retention not predictable (adjustability)
- Esthetic over cast clasp.

59. Combination Clasp
Advantages:
- flexibility.
- Adjustability.
- Esthetic.
- Coverage minimum tooth surface (line contact).
- Less likely to have fatigue failure.
Disadvantages:
- Extra-step.
- Distortion by careless handling.
- Less stabilization in suprabulge tooth.
- Distort with function.

60. Circumferential Clasp
First consideration in all cast clasp.
Disadvantages:
- More tooth surface covered.
- May increase the occlusal surface of the tooth.
- Its half round form prevents its adjustment.
Consist of buccal and lingual arms.
Common error is using both terminal retentive ends.

61. Ring Clasp
Nearly encircle all tooth.
When proximal undercut cannot be approached.
ML undercut on lower molar due to proximity of occlusal
rest and cannot be approached by bar due to lingual
inclination.
Should never be used as unsupported ring.
Should be supported with struct on non-retentive side or
auxiliary rest.
Maybe used in reverse on abutment anterior to tooth
supported edentulous area.

62. Embrasure Clasp
In unmodified CII and CIII where no edentulous opposite
side.
Should not eliminate the contact.
It is recommended to be protected with crowns, due to
high percentage of fracture.
Need double occlusal rests.
Two retentive clasp arms and two reciprocal arms,
bilaterally or diagonally opposed.

63. Other types of retainers
Lingual
retention with
internal rests
Near verticla walls of
internal rests
providing
reciprocation against
lingual retentive arm.
With tooth supported
only on anterior
abutment

64. Internal attachments
Advantages
over
extracoronal
Eliminate visible
retentive and
supportive
components
Better vertical
support
Disadvantages
Require prepared
abutments and
castings.
Require complicated
lab and clinical
procedure
Difficult to repair and
replace
Cost
Wear with
progressive loss of
frictional resistance

65. Indirect Retainers
Provide retention for distal extension base when
dislodge from its basal seat, providing leverage
advantage and consists of one or more rests,
supporting minor connectors and proximal plates
adjacent to edentulous areas.

66. Indirect Retainer
Most effective location is as far as possible from distal
extension base, at area perpendicular to fulcrum line.
Using mostly canine and mesio-occlusal of 1st premolar.

67. Factors influence effective IR
1. Establish seating of principal occlusal rest on primary
abutment teeth. Total displacement of rest will cause
no rotation about fulcrum line.
2. Distance from fulcrum line considering: length of distal
extension, location of fulcrum line, how far IR is placed
from fulcrum line.
3. Rigidity of connectors supporting IR.
4. Effectiveness of supporting tooth surface. Avoid
inclined teeth and weak teeth.

68. Forms of IR
Cingulum bars
and
linguplates
Canine
extensions
from
occlusal
rests
Occlusal rest
Canine rest
Rugae
Support

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