perio

1. RUBINA IBRAHIM
II Year PG Student
Department of Prosthodontia

2. Definition
Process of analysis and determination of loading and
deformation of bone in a biological system.
Role
Natural tooth and implants anchored differently in bone
The loading of teeth, implant and peri implant bone of prosthetic
superstructure
Optimize the clinical implant therapy

3. Types
 Reactive
 Therapeutic
Reactive Biomechanics
Any prosthesis that increases implant loading.

4. Therapeutic Biomechanics
Process of remediating each biomechanical factor in order to
deiminish implant overlaoding

5. Interrelated Factors
Analyzed during diagnosis and treatment planning and
maintained in a state of equilibrium.
 Biomechanics
 Occlusion
 Esthetics

6. Methods of Analysis
 Finite element analysis – Siegele 1989, Chelland 1991
Determined the distribution and concentration of strain and
deformation within implant and stated that force distribution to
surrounding bone occurs at crestal bone and level of third screw
thread.

7.  Birefringence Analysis
Done on plastic model utilizing polarized monochromatic light.
 Load Measurement : Lundreg 1989, Montag 1991
Precise data about forces exerted on Implant to supporting
bone.
Complicated - invivo Invitro- valuable
 Bond strength between implant and bone : Schmitz 1991
Done it by test of shearing, expulsion and torsion.

8. FORCE
Definition
Any application of energy, either internal or external to a
structure, that which initiates, changes or arrests motion.
Related Factors
 Magnitude
 Duration
 Type
 Direction
 Magnification

9. Magnitude
Anatomic region and state of dentition.
Craig, 1980
Molar - 390 – 880N
Canine - 453N
Incisor - 222N
Parafunction - 1000Psi
Colaizzi, 1984
Complete denture - 77 – 196N
Carlsson & Haraldson, 1985
Denture with implant - 48 – 412N

10. Duration
Mastication - 9mt/day with 20 to 30 psi
Swallowing - 20mt/day with 3 to 5 psi
Type
Compressive, Tensile and Shear
Cowin 1989
Bone - Strongest - Compression
- 30% weaker - tension
- 65% weakest – shear
Compressive force - Maintain integrity
Tensile and shear - Disrupts integrity

11. Direction
On centric vertical contact
Angle load Axial load
Greater tensile & shear stress Greater compressive
stress
Misch 1994
30% offset load – Decreases compressive strength – 11%
- Decreases tensile strength – 25%

12. Magnifying Factors
Applied Load  Torque
Includes,
 Extreme angulation
 Cantilevers
 Crown height
 Parafunction
 Bone density
Crown height - Increase in 1mm – 20% increase in torque.
With same load,
D1 Bone - Accommodate
D4 Bone - Cannot accommodate

13. Torque / Moment Load / Bending Load
Product of inclined resultant line of force and distance from
center of rotation.
Torque = Force x Distance
Natural tooth - Apical 1/3rd
Chelland, 1991
Implant - First third screw level.
Force
 Vertical - towards supporting bone
 Lateral - away supporting bone – Creates lever arm -
torque

14. FORCE DISTRIBUTION
Chelland 1991, Weinberg, 1994
Reiger 1990 Implant
Natural teeth Rigidly fixed
Periodontal ligament Stiff
Flexion Concentrates at crestal bone
Even force distribution & 1st 3 thread level
Increase
Root length – increase in surface area - better force distribution.
Implant length – Initial mobilization
&

15. FORCE DISTRIBUTION PRINCIPLES
System Components
 Vertical element – tooth or implant
 Connecting element
 Supporting medium – periodontal ligament or bone

16. Flexible Medium

17. Stiff Medium

18. Flexible and Stiff Medium

19. DIFFERENTIAL MOBILITY
Qualitative difference between the flexion of periodontal
ligament and stiffness of osseointegration.
Micro movement
Natural teeth with good bone
Will move laterally approximately 0.5mm
Measured occlusally.
Micron Movement – Weinberg, Rangert, 1994
Implant can move laterally 0.1mm or less measured
occlusally.

20. Natural Teeth Implant
Periodontal ligament - flexion Rigidly fixed – stiff
Even force distribution Concentration at crestal bone
0.5µm movement 0.1µm movement
Shock absorber Rigid
Reduces the magnitude of Increases the magnitude
stress
Occlusal trauma – No such warning signs only
Signs of cold sensitivity, bone microfracture
Wear facets, Pits, Drift away
& mobility

21.  Elastic modiolus similar to bone 5-10times different
Therefore, with same load
Increase stress,
concentrates at crestal
bone
Surrounding bone formed childhood Forms rapid and intense
Lateral force – exert Lateral force exert
Movement No movement
Dissipates to apex Concentrates at crestal
bone

22. Forces acting on Implants
 Occlusal loads during function
 Para functional habits
Passive Loads
 Mandibular flexure
 Contact with first stage cover screw and second stage
permucosal extension.
 Perioral forces
 Non –passive prosthesis.

23. TRAUMATIC FORCES OR IMPLANT OVER LOADING
 Non passive prosthesis
 Parafunction
 Initial contact during maximum intercuspation
 Labial stresses generated during eccentric movements.
Therefore,
 Eliminate posterior contact during protrusion and lateral
excursion.
 Prosthesis come in contact only during intercuspation.

24. FORCE DISTRIBUTION IN MULTIPLE IMPLANT PROSTHESIS
Splinting
 Natural tooth – Periodontal ligament – forced distribution
 Implant – stiff – no force distribution and only concentration at
crestal bone

25. FORCE DISTRIBUTION IN COMBINED PROSTHESIS
 Supported by both natural teeth and implants
 Mode of attachment
 Flexible
 Stiff
 Flexible – internal attachment
 Stiff – when terminal abutments are implants

26. FLEXIBLE ATTACHMENT
 Tooth supported prosthesis – Female attachment
 Implant supported prosthesis – Screw retained
Flexion Occurs
Not Deleterious

27. STIFF ATTACHMENT
 Natural tooth – permanently cemented substructure
telescopic crown
 Implant supported prosthesis – over crown, coping with
temporary cement
Tend to Loosen
To eliminate, permanent cementation rather than fixed retrievability

28. DIAGNOSTIC FACTORS IN COMBINED PROSTHESIS
Standard Prosthesis design
Internal attachment placed in distal of natural tooth
Differential mobility
Natural tooth cannot support implant
Increase in lever arm
Increase Torque

29. Recommended Prosthesis Design
One cantilever pontic from each segment
Flexible internal attachment
Drifting apart of segment
Decreased Torque

30. FOUR CLINICAL VARIANT WITH IMPLANT LOADING
Includes
 Cuspal inclination
 Implant inclination
 Horizontal Implant Offset
 Apical Implant Offset

31. Cuspal Inclination
Increase in 10°  increased 30% torque
Implant Inclination
Increase in 10°  Increased 5% torque

32. Horizontal Implant Offset
Increase in 1mm  increased 15% torque
Apical Implant Offset
Increase in 1mm  Increased 5% torque

33. Staggered Implant Offset – Rangert 1993
Staggered buccal and lingual offset
Tripod Effect
Compensates torque
Implant placed 1.5mm bucal and lingual from centre line to
achieve Tripodism.

34. Weinberg 1996
In maxilla, lingual offset - increased 24% torque
Buccal offset - Decrease 24% torque
Maxilla - Tripod –increase in 24% torque
Mandibular - Tripodism
Maxilla - As far as bucally

35. Weinberg, 1996
In posterior working side, occlusion. Produces buccally
inclined resultant line of force on maxilla and lingually inclined
resultant line of force on mandible.
Reduces 73% of torque in mandible

36. THERAPEUTIC BIOMECHANICS
 Decrease cuspal inclination
It reduces the distance between implant and resultant line of
force.

37.  Cross occlusion
Buccolingual relation  cross occlusion
Reduces horizontal implant offset
Reduces torque

38.  Implant Position
Implant head as close to center line of restoration –
Reduces horizontal offset.

39. PHYSIOLOGIC VARIATION – CENTRIC RELATION
Kantor, Calagna, Calenza, 1973.
Centric relation record show physiologic variation of ±
0.4mm
Weinberg 1998
Occlusal anatomy modified to 1.5mm horizontal fossa
Produce vertical resultant line of force within expected range of
physiologic variation.

40.  Anterior Vertical Overlap
Steep vertical overlap Less steep
Extreme Torque Less Torque

41. BIOMECHANICS AND RESORPTION PATTERN
Posterior Mandible
Bone resorbs along root inclination
Therefore, posterior mandible – bone resorb lingually
Reactively Biomechancis
Lingual position of restoration +
Buccal implant placement - increased torque

42.  Therapeutically
Can be done by
 Reduced cusp inclination
 Implant head close to centre line of restoration
 Angulated abutment - parallelism

43.  Posterior Maxilla
Reactively
 Restricted maxilla
 Location of sinus
 Buccal cortical plate fracture
 Unfavourable biomechanics

44. Therapeutically
 Cuspal inclination – reduce
 Head of implant close to center of restoration
 Angled / custom – reangulated abutment
 Cross occlusion
 1.5mm horizontal fossa.

45. Anterior Maxilla
Reactively
Esthetically - Labially Proclined
- Steep vertical overlap

46. Therapeutically
 Lingual horizontal stop – redirect the force as vertically as
possible.
 Angled abutment
 Implant head close to center of restoration

47. COMPLETE EDENTULISM AND BIOMECHANICS
 Screw loosening not common these patients
Implant placed across and around arch
Cross splinting
Lateral forces –Vertical force
Tripodism
Excellent resistance to bending

48. WIDER IMPLANTS
Developed by Dr.Burton Langer
Advantages
 Increase in surface area
 Limited bone height
 Upon removal of failed standard size implant
 Wider implant - Abutment screw 2.5mm -
Larger size – tighter joint –
overall strength increases

49. BONE DENSITY AND BIOMECHANICS
Density ∞ Strength
∞ Amount of contact with implant
∞ Distribution and dissipation of force
Misch 1995
 FEM study – stress contour is different for each bone
density.
With same load
D1 - Crestal stress and lesser magnitude
D2 - Greater crestal stress and along implant body
D4 - Greatest stress and farther apically

50. BONE DENSITY AND TREATMENT PLAN MODIFIER
 Prosthetic factors
 Implant number
 Implant – Macrogeometry
 Implant – Design
 Coating
 Progressive loading

51. PROSTHETIC FACTOR
As density decreases, biomechanical load should also
decreased
 Shortened cantilever length
 Narrow oclusal table
 Offset load minimized
 RP4 > FP1, FP2, FP3, removal at night
 RP5 – force shared by soft tissue
 Force directed along long axis of implant

52. Implant Number
Increase in number  Increase in functional loading area
Implant Macrogeometry
Length
 D1 - 10mm
 D2 - 12mm
 D3 - 14mm with V-shaped thread screw
Density decreased  Length increased

53. Width
 Increase in width – increase in surface area
 1mm increases  30% increase in surface area
 D3 & D4  wider implants
Implant Design
 Smooth cylindrical implant – shear force at Interface –
Coating with HA / Titanium
 Titanium alloy (Ti-6Al-4V) exhibit best biomechanical,
biocompatible, corrosion resistance.
Coating
 Increased bone contact area
 Increased surface area

54. Progressive Loading
Misch 1990
Gradual increase in occlusal load separated by a time
interval to allow bone to accommodate.
Softer the bone  increase in progressive loading period.
Protocol
Includes,
 Time
 Diet
 Occlusal Contacts
 Prosthesis Design

55. Time
Two surgical appointments between initial implant placement
and stage II uncovery may vary on density.
 D1 - 5 Months
 D2 - 4 Months
 D3 - 6 Months
 D4 - 8 Months
Diet
 Limited to soft diet – 10 pounds
 Initial delivery of final prosthesis-21 pounds

56. Occlusal Material
Initial step – no occlusal material placed over implant
Provisional – Acrylic – lower impact force
Final - Metal / Porcelain
Occlusion
 Initial - No oclusal contact
 Provisional - Out of occlusion
 Final - At occlusion

57. Prosthesis Design
First transititional – No occlusal contact
No cantilever
Second transititional - Occlusal contact
with no cantilever
Final restoration - Fine occlusal table and cantilever

58. SINGLE TOOTH IMPLANT AND BIOMECHANICS
 Requires good bone support
 Control of occlusal lever parallel to long axis
 Access for oral hygiene

59. When space exceeds 12mm
When space less than 12mm

60. When space exceeds 8mm with limited width
Should not be placed off center

61. Posterior Triangular Zone
 Active zone
 Occlusal loading parallel to long axis

62. Cantilever Prosthesis and Biomechanics
 It result in greater torque with distal abutment as fulcrum.
 May be compared with Class I lever arm.
 May extend anterior than posterior to reduce the amount of
force
It depends on stress factors
 Parafunction
 Crown height
 Impact width
 Implant Number

63. Arch form
English 1993 – AP Spread
 Cantilever length = AP spread x 2.5
 Tapering - canine and posterior implants with
anterior cantilever
 Square - Anterior implant with posterior
cantilever

64. Tapering  Ovoid  Square
Less dense bone  Anterior cantilever with prosthesis  Distal
implants, placed to increase AP-spread.
Maxilla - more implants required than mandible

65.  Sufficient bone height exist to place long implant,
 Avoid contact on central incisors during protrusion, labial
excursion and maximum intercuspation
CANTILEVER FIXED PARTIAL DENTURE

66.  Group function - lateral movement
 Avoid loading on canine
 Lateral guidance provided by central and lateral incisor

67. Two implant supporting a first molar and 2nd premolar with
1st premolar cantilever  Active cusp eliminated  canine palatal
structures.

68. Three implants placed with Two implants  risky
2nd premolar as cantilever and /or contraindicated

69. MANDIBULAR FLEXURE
Picton 1962
 Stated that mandibular move towards midline on opening 
Because of external pterygoid muscle on ramus of mandible
 Medial movement occur distal to mental foramen and
increases as it approaches ramus.
James 1980 & Burch 1982
 Movement - 0.8mm - 1st molar
1.5mm - Ramus area

70. FLEXION
Implant - Natural teeth - mandible
0.1mm 0.5mm 10 to 20 times
Complete cross arch splinting of posterior molar  Mandible flexion
 Lateral force
 Bone loss around implant
 Loss of implant fixation
 Material fracture
 Unretained restoration
 Discomfort on openings

72. FATIGUE FAILURE
 Characterised by dynamic cyclic loadind
 Depends on – biomaterial
geometry
force magnitude
number of cycles

73. Biomaterial
 Stress level below which an implant biomaterial can be
loaded indefinitely is referred as endurance limit.
Ti alloy exhibits high endurance limit
Number of cycles
Loading cycles should be reduced
To eliminate parafunctional habit
To reduce occlusal contacts

74. Implant geometry
 Resist bending & torsional load
 Related to metal thickness
 2 times thicker – 16 times stronger
Force magnitude
Arch position( higher in posterior & anterior)
Eliminate torque
Increase in surface area

75. IMPLANT DESIGN & BIOMECHANICS
 Ti alloy offers best biomechanical strength & biocompatability
 Bending fracture resistance factor
Wall thickness = (outer radius)4_ (inner radius)4
 If outer diameter increases by 1mm & inner diameter unchanged
33% increase in bending fracture resistance
 If inner diameter decreases by 1mm & outer diameter unchanged
20% increase in bending fracture resistance

77. Thread pitch Thread depth

78. Depth –distance between major & minor diameter of thread

79. Implant macrogeometry
Smooth sided cylindrical implants – subjected to shear
forces
Smooth sided tapered implants – places compressive
load at interface
Greater the taper – greater the compressive load delivery
 Taper cannot be greater than 30 degree
Implant width
Increase in implant width – increases functional surface
area of implant
Increase in 1mm width – increase in 33% of functional
surface area

80. Implant length
Increase in length –Bicortical stabilisation
Maximum stress generated by lateral load can be dissipated by
Implants in the range of 10-15mm
Softer the bone –greater length or width
Sinus grafting & nerve re-posititioning to place greater implant length
Resistance to lateral loading

81. Crestal module design
Smooth parallel sided crest –shear stess
Angled crest module less than 20 degree-
-Increase in bone contact area
-Beneficial compressive load
Larger diameter than outer thread diameter
-Prevents bacterial ingress
-Initial stability
-Increase in surface area

82. Larger diameter & angulated crestal module design

83. Surface Coating
-Titanium plasma spray
-Hydoxyapatite coating
Advantages
-Increase in surface area
-Roughness for initial stability
-Stronger bone – implant interface
Disadvantages
-Flaking and scaling upon insertion
-Plaque retention
-Nidus for infection
-Increased cost

84. IMPLANT PROTECTED OCCLUSION
 Occlusal load transferred within physiologic limit
 Misch,1993
width of occlusal table directly related to implant width
 Narrow occlusal table with reduced buccal contour permits
sulcular oral hygiene
 Restoring occlusal anatomy of natural tooth
-offset load
-complicated home care

85. Narrow occlusal table + reduced
Buccal contour permits oral hygiene,
Axial loading & reduces fracture
Posterior crest of maxilla medial to
Mandibular crest

86. Apical Design
Round cross-section do not resist torsional load
Incorporation of anti –rotational feature
-Vent hole- bone grow the hole
-resist torsion
-Flat sidegroove - bone grow against
-places bone in compression

87. Maxillary lingual cusp & contour reduced
Reduce offset load from opposing natural tooth
Mandibular buccal cusp - in width & height

89. Occlusal material
Porcelain,resin,gold
Porcelain - esthetics, chewing efficiency
Gold - Impact force,chewing efficiency,fracture
resistance,wear,interarch space,accuracy
Acrylic - Esthetics , impact force,static load

90. IMPLANT ORAL REHABILITATION
Constitutes
 Muscle relaxation
Absence of articular inflammation
Stable condylar position
Creating organic occlusion
Absence of pain in stomatognathic system

91. Organic occlusion components
Correct vertical dimension
Maximum intercuspation in centric relation
Adequate incisal & condylar guidance
Stable bilateral posterior occlusal relation in equilibrium with
long axis of implant
Absence of prematurities
Absence of interferences in eccentric movements

92. Bruxism patients
Education & informed consent to gain co-operation in
eliminating parafunction
Use of night guard
- anterior guided disooclusion
- posterior cantilever out of occlusion
- soft night guard releived over
implant
Soft tissue supported prosthesis
- soft tissue tend to early load the
implant & hence relieved over it
Removable partial denture over healing abutment
- 6mm hole diameter through metal is
prepared

93. Final prosthesis
- narrow occlusal table
- centric occlusal contact aligned parallel to long axis
Important criteria
- additional implant
- greater diameter implant

94. CONCLUSION
Biomechanics is one of the most important consideration
affecting design of the framework for an implant bone
prosthesis.It must be analysised during diagnosis &
treatment planning as it may influence the decision
making process which ultimately reflect on the longevity of
implant supported prosthesis

95. Bibliography
Implant & restorative dentistry- Martin Dunitz
Atlas of tooth & implant supported prosthesis-Lawrence A.
Weinberg
Atlas of oral implantology- A.Norman Cranin
Contemprorary implant dentistry – Carl Misch
Branemark implant system- John Beumer
ITI dental implants- Thomas G.Wilson
Implant prosthodontics- Fredrickson
Dental implants- Winkelmann
Oral rehabilitation with implant supported prosthesis
- Vincente