occlusal,lingual and incisal rest & rest seat preparation - RPD - prosthodontics.

2. 1) Denture base
2) Artificial teeth
3) Connectors
4) Retainers
5) Supporting rest
1
2
3
4
5

4. Rest:Rest:
extensions of a Partial Denture, Placed in Rest Seats,
Which are prepared on either the Occlusal, Lingual
surfaces or Incisal edges of the teeth, providing Support
to the Partial Denture

5. Rest seat:Rest seat:
portion of a tooth prepared to receive a rest

6. Functions Of The RestsFunctions Of The Rests
1-Support(the main function):
resist displacement towards denture supporting
structures which will prevent impingement of gingival
tissues adjacent to the abutment

7. 2-maintain the components of the dentures in their
positions and prevents spreading of clasp arm

8. 3-Distributing the Occlusal Load
4-May Act As Indirect Retention

9. 4-Direct food away from tooth
contact and embrasure area

10. 5-improve the existing occlusion

11. Types of restTypes of rest
i. Occlusal rest{ molars- premolar}
ii. Lingual rests{ cingulam of canines}
iii. Incisal rests {canines-incisors}
iv. Embrasure Hooks

12. A rigid extension of a RPD that contacts the occlusal
surface of a posterior tooth or restoration,
a rest seat specially prepared to receive it.
A-Occlusal RestA-Occlusal Rest

13. Types of occlusalTypes of occlusal restrest
A- conventional
B-other forms: 1. Box-shaped O.R.
2. Extended O.R.
3. Onlay O.R.
4. Inter proximal O.R.
5. Embrasures O.R.
6. Internal O.R.

14. Partial denture
without occlusal
rest is called gum
stripper

15. Requirements of Rest SeatRequirements of Rest Seat
PreparationPreparation
1- Should be rounded triangular
outline form, the base of the triangle
at the marginal ridge and its rounded
apex is towards the center of the
tooth

16. 2-The marginal ridge is lowered approximately 1.5
mm for base metal alloy (permit sufficient bulk(
Mesiodistally from 1/3 to½
Buccolingually ½ the distance between cusp tips

17. 3-The angle between the minor connector and the rest
should be less than 90˚
1-To prevent Slippage of the Prosthesis Creating an
Orthodontic Like Force
2-To direct the forces Along the Long Axis of the tooth

18. 4-the rest seat may be papered in either
saucer shape or box shape
Saucer shape(spoon) used more than box in cases of :
•free end saddle
•bounded cases having weak abutments

19. 5-Rest seats are prepared in sound enamel, or in
crowns and inlays
Fluride gel applied to abutment

20. Requirements of occlusal RestRequirements of occlusal Rest::
1.Should have sufficient thickness
of metal to prevent breakage
especially over the marginal ridge.
2.It should fit the rest seat
accurately with beveled margins,
preventing food stagnation or
impaction.

21. 3.It must not raise the vertical dimensions of occlusion

22. 4-In bounded partial denture: placed in the near zone
of the occlusal surface to edentulous area
In free end partial dentures: placed in the far zone of
the occlusal surface to decrease torque action on
abutment tooth

23. use of amalgam
restoration to
support an occlusal
rest is less due to
its tendency to
creep and flow
under pressure

24. B-other formsB-other forms
1-Box shape1-Box shapeIndication
a cast gold restorations
a strong periodontally healthy abutment a

25. Advantage
1.If made deep it will provide guide surfaces to
control the path of insertion of the dentures
2.Prevent lateral movement of denture
3.Provide increased denture retention

26. 2-Tipped molar2-Tipped molar
(Mesially inclined mandibular molar)
•The rest should be designed to prevent further tipping,
It must direct forces down the long axis of the tooth by
either of one of these ways :

27. 1. Additional occlusal rest in distal fossa

28. 2. A rest preparation that extended from the mesial
marginal ridge to the distal triangular fossa to
minimize further tipping

29. box shaped
less used in
bounded
cases

30. 33--onlayonlay
•An enlarged occlusal rest covering the entire occlusal
surface and extending buccally and lingually
•Retained by mechanical or adhesive means .

31. Functions:
1-support ( resist tissue award force(
2-improvement of occlusion by increasing the reduced
vertical dimension ( correction of occlusion bite(
3-minimize lateral component of the force
4-splinting ( in case of periodontally weak teeth(

32. Advantages:
1-direct the force along the long axis
2-promote RPD stability
3-minimize tipping of tooth
3-restore occlusal plane

33. 3-interproximal O.R.3-interproximal O.R.
•They are prepared as individual occlusal rest seats ,
except that the preparations must be extended
further lingually than the ordinarily accomplished .
• used to avoid interproximal wedging , additionally
will shunt food away from contact points

34. Preparation:
1-should avoid weakening or eliminating contact points
2-provide adequate bulk for strength.
3-occlusion should not be altered

35. Onlay Cast in
gold or chrome
cobalt

36. 44--EmbrasureEmbrasure restrest
Two simple circle clasps joined together fashioned on
the two abutment teeth.

37. Functions:
1-bridge gap between teeth
2-prevent food impaction between the space teeth

38. 55--Internal restInternal rest
Indicated for bounded partial denture that totally
tooth supported

39. Advantage:
1-support come from floor of the rest
2-Lateral stabilization from parallel wall
3-Retention from lingual clasp
4-esthetics( buccal clasp(

41. II- Lingual RestsII- Lingual Rests::
A- Cingulum Rest ( inverted V Rest(.
B- Ball Rest.
C- Canine Ledge.

42. A- Cingulam RestA- Cingulam Rest (inverted Rest(inverted Rest((
Def. a portion of RPD ; placed in an enamel seat at the
cingulam or just Incisal to it.
Indication:
•no posterior tooth to place an occlusal rest .
•commonly used on the maxillary canines
•Rarely on lower anterior; due to less thickness of enamel

43. **the most satisfactory
preparation is that placed on a
prepared seat in a cast
restoration.
**when preparing a cingulam
rest in a cast restoration ; the
rest seat should be planned and
done on the wax pattern before
casting the restoration.

44. Specification of Cingulum Rest Seat:
1-A rounded inverted V shaped preparation
)half – moon shaped(.
2-All sharp angles & undercuts should be eliminated.
3-The rest seat is broadest at the center and merges
as it approaches proximal surfaces

45. B- Canine ledgeB- Canine ledge::
-A step-like preparation ; placed on the mesial or distal
halves of the lingual surfaces of the maxillary canine.
-The ledge rest seat should be perpendicular to the
long axis of the tooth.
-All undercuts & sharp line angles should be avoided.

46. C- Ball RestC- Ball Rest::
Def: cingulam ball rests with rounded outline; placed on
the mesial or distal halves on the lingual surfaces of all
anterior teeth.
-BALL rest permits rotational movements to occur
during function of tooth-mucosa born RPDs.

47. III- Incisal RestIII- Incisal Rest::
Def.: a rigid extension of a RPD , placed
at the Incisal angles of anterior teeth on
prepared rest seats.
-commonly used as auxiliary rest or as
indirect retainers.
-More applicable on mandibular teeth
due to lack of adequate thickness of
enamel on the lingual surface.

48. -A saddle shaped preparation , and the notch should
extend onto the facial surface to prevent the tooth
from moving labially.

49. N.B.:
The lingual Rest is preferable to an incisal Rest??
because:
1.- placed closer to the center of rotation of the abutmen
thus reducing its tendency to tipping
2.- More esthetic .
3.- Less bothersome to tongue .

50. IV- Embrasure HooksIV- Embrasure Hooks::
Def.: rests placed in embrasures between natural teeth
extending slightly over the buccal or labial surface but
never extend below the survey line.

51. Advantages:
-provide support.
-splinting of natural teeth.
-resistance to lateral and antero-posterior movement.
-may act as indirect retainer.
Disadvantages:
-poor esthetics.
-wedging action on teeth.

52. preferred site for a
rest , is the occlusal
surface of a molar
If anterior tooth , a
canine is preferred over
an incisor
In absence of canine ,
multiple lingual rests are
prepared on anterior
teeth.

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