A new version of designing partial denture in terms of Bio-kinetic. Actually this chapter consists a lot of information, however, it was edited in time limits. Thanks to Primary authors.

1. Statics of Partial Dentures
Professor Dr. Kyaw Tint
B.D.S.(IDM), M.D.Sc.(UDM), Ph.D(TMDU)
Dip.Med.Ed (UOPH) ,Cert. in Higher Education(IIE,USA)
Attached to IADR, JBI, PFA
1st
September 2018, Grand Han Thar Hospital

3. • Statics is the study of the equilibrium of forces
acting on a rigid body
• In statics, rigid bodies are structures that
deform so little when loaded by forces that the
points of application of force undergo minimal
displacement
• Equilibrium refers to the state when a rigid body
is at rest or in uniform motion

4. force is characterized by
• Magnitude, number, and unit (eg, 30 N)
• Direction, represented by the vector arrow,
in which the tip points the direction and the
length represents the measure of forc
• Position of the line of action on which the
force can be moved

5. Forces that have a common line of action can be
combined by simple addition or subtraction.
The resultant force lies on this same line of action.

6. If two forces are not parallel
but have a common point of
application, the resultant
force is determined by
means of a parallelogram of
forces
The resultant of
several nonparallel
forces is determined
by means of a
polygon of forces

7. If a force acting
on a tooth is not
in the direction
of the tooth axis
or runs at a
distance from
the axis, a torque
acts on the tooth

8. In multiple-rooted teeth, eccentric forces can be
absorbed to a certain degree. In tilted teeth,
forces encountered have disastrous effects
when they produce torques that tip the tooth

9. • In equilibrium,
any force (action force or input force) causes a
counterforce (reaction force or output force) that is
equal and in the opposite direction (Newton’s third
law).

10. 1.Stable equilibrium exists
when a body seeks to return
to its initial position if
displaced by external forces.
2. Neutral equilibrium exists
when any displacement
brings the body into a new
equilibrium position.
3.Unstable equilibrium
exists when a body tries to
leave its original position.

11. • In a statically indeterminate system, the
equilibrium conditions are insufficient to
calculate support reactions;
• In a statically determinate system, the
support reactions can be ascertained
from its equilibrium conditions alone

12. Forces Acting on the
Residual Dentition
• When constructing partial dentures, it is
important to ensure that the remaining
teeth are not exposed to any eccentric
action of force by the retainers.
• Sagittal Force
• Transverse Force
• Vertical Masticatory Force
• Spring Force and Friction

13. Mixed Support
• If a free-end saddle has mixed support,
the mechanical system is no longer at rest
and can no longer be calculated by statics
methods.
• For this purpose, kinetics analysis criteria
should be used

14. • Mucosa-borne dentures can be
interpreted as rigid bodies that rest on
floating bearings or springs; all
compressive, tensile, shearing, and tipping
forces will tilt, twist, displace, or tip the
rigid body
• This is a statically indeterminate system.

15. A clasp denture for restoring a free-end
saddle is always a statically indeterminate
system because it has mixed support

17. Different
periodontal support areas are formed
• Polygonal support areas for alternating
edentulous spaces
• Square (trapezoidal) support areas
• Triangular support areas
• Linear supports
• Punctiform supports

18. Triangular support area
Square support area
Polygonal support area

19. If denture is supported by one tooth, result in
the saptial axes, A line between two rests
always represent the axis of rotation.

20. An axis of rotation also arises when the
support line divides the denture body

21. Visco-elastic bedding
• The compressibility of the mucosa is also
influenced by the shape of the support:
- Parts that are subject to punctiform loading
will sink more deeply (up to 3 mm) than
- Edges with linear loading (up to 2 mm),
- Extensive saddle areas undergo relatively little
sinking (up to 0.5 mm)
• Therefore, viscoelastic bedding of the denture
should be assumed

22. Spring Force and Friction
Spring force = Spring constant ×
Spring deflection (or)
F = c × s
Friction force = Friction coefficient ×
Normal force (or )
F = μ × Fn
ClaspsHooke’s Law

24. Action and Resistance Levers
AL= Action lever RL= Resistance Lever Arm

25. If the teeth on a denture are set up slightly outside the alveolar ridge
on the vestibular side, lever effects may occur, and the denture may
be tipped off.
The distance from the point of force application to the center of the
alveolar ridge is regarded as the action lever arm.
Clasping the denture on the opposite side of the jaw counteracts the
tipping as a resistance lever arm.

26. Design Planning Criteria
• Analysis of static relationships
• Analysis of physiologic conditions
• Cost-effectiveness analysis
• Support, Connector, Saddle
• Asthetics, Comfort, Efficiency, Hygiene

27. Analysis of static relationships
• Try to get complete periodontal support
• Defined retentive forces of anchoring elements
• One clasp with occlusal support, close to saddle
• Denture design must actively support to
residual dentition through splinting

28. Analysis of physiologic conditions
• Observe the principles of periodontal hygiene
• Design denture frameworks to be stable, slim,
and clear of the periodontium and tongue
• Make handling and cleaning easy for the patient
• Allow for the possibility of periodontal treatment
• Avoid using a diversity of materials.
• Use biocompatible materials.
• Relate esthetic concerns to the patient’s needs

29. Cost-effectiveness
analysis
• Choose simple and effective anchoring
elements
• Use of prefabricated structural components
• Reasonable technical effort and materials
• Aftercare, reparability, and extension
possibilities etc…

30. Residual Dentition Situations and
Design Descriptions

31. Design 1

32. • All of the remaining teeth undergo coronal
restoration, and teeth that are close
together are subject to primary splinting.
• The edentulous gaps are fitted with
closed, intracoronal parallel attachments,
and the free-end gap is fitted with a T-
attachment and a double-arch shear
distributor.
As a result, secondary splinting of the
abutment teeth is achieved

33. Static, Advant: & Disadvant:

34. STATICS
•The statics of a partial denture that is combined with
rigid anchoring and supporting elements are balanced.
•The free-end saddle may only sink by means of the
periodontal resilience of the abutment teeth.
•All of the masticatory forces are transferred to the
periodontium.
•The denture sits absolutely firmly, the periodontal
hygiene conditions are favorable, and the result is a
reliable long-term restoration

35. Advantages
• Secure, firm seating in the mouth
• Rigid denture–residual dentition connection
• No mucosal loading
• Worn parts can be replaced
• Excellent esthetic quality
• Favorable conditions for periodontal
hygiene due to intracoronal placement of
attachments

36. Disadvantages
• If artificial and natural teeth are unbalanced,
there is a risk of permanent overloading of the
abutments
• misleads people into demanding too much
from the restoration
• handling of this construction is problematic
• This denture is not a good value for the
money

37. Design 1: Model cast-clasp denture

38. Statics, Advantage&Disadvantage
• S: Polygonal support, full clasping
• A: Most cost-effective, easy to handle
• D: - Mechanical loading to Enamel of
abutments, plaque accumulation
- Need to prepare guiding plane

39. Design 1: Alternative solutions 1
For esthetic reasons, the canines and first premolars
on both sides are fitted with Bonwill clasps. The static
relationships are comparable if the anterior rests close to the
saddle are placed so they can tilt when the free-end saddle is
loaded.

40. Design 1: Alternative Solutions 2
Fixed partial denture
to which a double-arch
circular notch at the
free-end saddle is
created for the shear
distribution arm of a
monoreducer,
More expensive

41. Design 2

42. Design 2: Alternative
solution
closed parallel
attachments
together with
double-arch
circular notches
with shear
distributors at the
free-end saddles

43. Design 3
To identify the rest points
The rest points establish
the path of the clasps

44. An anterior palatal strap or a
sectioned plate may be designed,
but it does not meet the
requirement for tongue clearance.
The pressure and fricative field is
covered and may impede
tongue function (eg, phonetics
and taste); in addition, the device
is less comfortable to wear.
The shaping of the denture
framework allows for
periodontal Hygiene and
tongue clearance

45. Full clasping of the
remaining teeth offers
good splinting effects,
providing the horizontal
positional stability
The diagonal tipping
line establishes four
resistance levers,
which are active
against the action lever
on the free-end saddle
The esthetics are
deficient, and
periodontal hygiene
is adequate

46. Design 3: Alternative Solution
14-pontic partial denture in
which the free-end pontics
are supported on at least one
implant placed in the gap
A fixed partial denture from the right
second molar to the left first premolar
is supplemented by a monoreducer in
the free-end area, which is secured
via a lock attachment and supported
by a double-arch shear distributor in a
circular notch

47. Please take a break…..

48. A given force can be resolved if the magnitudes of the single forces
are known. To do this, a polygon of forces is constructed by drawing arcs of
circles at the origin and at the tip of the force being resolved, along with the
radius of the components. The intersection of the arcs establishes the apices
of the components