dental

2. FORCES
ACTING ON
REMOVABLE
PARTIAL
DENTURES

3. Fibers of periodontal ligament are
arranged such that their resistance to
vertical forces is much greater
than that to horizontal forces
Tissues are adapted toTissues are adapted to
receive and absorb forcesreceive and absorb forces
within their physiologicalwithin their physiological
tolerancetolerance

4. POSSIBLE
MOVEMENTS
OF THE
PARTIAL
DENTURE

5. I- Tissue-ward movementsI- Tissue-ward movements
II- Tissue-away movementsII- Tissue-away movements
III- Horizontal movements:III- Horizontal movements:
A) Lateral movementsA) Lateral movements
B) Antero-posterior movements.B) Antero-posterior movements.
IV- Rotational movementsIV- Rotational movements
At least four possible movements of
the partial dentures exist

6. Vertical forces acting in gingival direction tending
to move the denture towards the tissues
I- Tissue-ward movementsI- Tissue-ward movements

7. Vertical forces acting in gingival direction tending
to move the denture towards the tissues
I- Tissue-ward movementsI- Tissue-ward movements

8. • Mastication, Swallowing And Aimless
Tooth Contact. Biting Forces
They occur during
• P.D. should be designed to resist this
movement by providing adequate
supporting components
•This function of the partial denture is called
“Support”

9. • The
Resistance to
Tissue Ward
Movement
Support
• Distribute the Forces Over the Supporting
Sttructure
• Transferring
Occlusal
Stresses to
the
Supporting
Oral
Structures

10. Distribute the Forces Over the
Supporting Structure

11. II- Tissue-away movementsII- Tissue-away movements
Vertical forces acting in an occlusal direction
tending to displace and lift the denture from
its position

12. Tissue-away forces occur due to
The action of muscles acting along the
periphery of the denture
•This function of the partial denture is called
“Retention”
Gravity acting on upper dentures or by
sticky food adhering to the artificial teeth
or to the denture base.

13. Resistance to
movement of
the denture
away from its
tissue
foundation
(resistance of
a denture to
dislodgment)
Retentio
n

14. This Function Is Mainly Provided By:
1-Mechanical Direct Retainers, Which
Engage Undercuts On Abutment
Teeth
2-Attachments.
3- physiologic forces on polished
surfaces of denture bases
4- physical forces on fitting
surfaces of denture bases

15. Horizontal movementsHorizontal movements
A) Lateral movementsA) Lateral movements
Horizontal forces developed when the
mandible moves from side to side
during function while
the teeth are in contact
Lateral movements have a
destructive
effect on teeth leading to
tilting, breakdown of the
periodontal ligament and
looseness of abutment teeth.

16. Bracing
to Lateral
Movemen
t of the
Partial
Denture
Resistance

17. This Function Is Mainly Provided By:
Bracing clasp armsplaced at or above
the survey line of the tooth.
Minor connectorsin contact with axial
(vertical) surfaces of abutment teeth
Proximal plates
Adequate extension of the flanges

19. Horizontal movementsHorizontal movements
B) Antero-posterior movementsB) Antero-posterior movements
There is natural tendency for the
upper denture to move forward
and for the lower to move
backward.
Horizontal forces which occur during forward
and backward movement of the mandible
during function while the
teeth are in contact

20. Horizontal movementsHorizontal movements
B) Antero-posterior movementsB) Antero-posterior movements
Forward movement of the upper denture could
be resisted by:
Anterior natural teeth.
Palatal slope.
Maxillary tuberosity.
The natural teeth bounding the edentulous space.
The backward movement of the lower denture
could be resisted by:
The slope of the retromolar pad.
The natural teeth bounding the saddle area.
Proximal plates.

21. From:From:
• Guide planesGuide planes
• Bracing clasp armsBracing clasp arms
•Reciprocation I barReciprocation I bar
• Lingual platesLingual plates
• RestsRests
• Denture basesDenture bases
Active I-barActive I-bar
ReciprocationReciprocation
I-barI-bar
BRACING AND STABILITYBRACING AND STABILITY

24. I- Tissue-ward movementsI- Tissue-ward movements
II- Tissue-away movementsII- Tissue-away movements
III- Horizontal movements:III- Horizontal movements:
A) Lateral movementsA) Lateral movements
B) Antero-posterior movements.B) Antero-posterior movements.
IV- Rotational movementsIV- Rotational movements
At least four possible movements of
the partial dentures exist

25. IV- Rotational movementsIV- Rotational movements
Rotational movements are due to
the variation in compressibility of
supporting structures, absence of
distal abutment at one end or more
ends of denture bases, and /or
absence of occlusal rests or
clasps at any end of the base

26. Periodontal ligamentPeriodontal ligament
(0.25mm)(0.25mm)
MucosaMucosa
(2.0mm)(2.0mm)
Different Displacement Between PDL &Different Displacement Between PDL &
MucosaMucosa

28. 1-Rotation of the extension denture
base around transverse fulcrum axis:

29. Class I Lever:
fulcrum: between E and R
E
R
Free end
saddle
partial
denture
without
indirect
retention

30. 1-Rotation of the extension denture
base around transverse fulcrum axis:
A) Rotation of the denture base towards
the ridge around the fulcrum axis joining
the two main occlusal rests

31. 1-Rotation of the extension denture
base around transverse fulcrum axis:
B) Rotation of the denture base away
from the ridge around the fulcrum axis
joining the two main occlusal rests

32. Class I Lever:
fulcrum: between E and R R X d1= E X d2
Direction of lever arm: E opposite R

33. Components of
Removable
Partial Denture
That Are Used
to Reduces the
Tendency for a
Removable
Partial Denture
to or Rotate in
an Occlusal
Direction
About the
Fulcrum Axis
Indirect
Retention

34. when force is directed against unsupported end of
beam cantilever can act as first class lever Torque
on the abutment tooth
F

35. A rigid major connector.
Balanced contact between
upper and lower teeth.
Broad base coverage
This movement is counteracted by :
Providing adequate bracing

37. THANKTHANK
YOUYOU