IMPLANTS-Biomechanics.ppt

perio

1. RUBINA IBRAHIM
II Year PG Student
Department of Prosthodontia

2. Definition
Processofanalysisanddeterminationofloadingand
deformationofboneinabiologicalsystem.
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
ReactiveBiomechanics
Anyprosthesisthatincreasesimplantloading.

4. Therapeutic Biomechanics
Processofremediatingeachbiomechanicalfactorinorderto
deiminishimplantoverlaoding

5. Interrelated Factors
Analyzedduringdiagnosisandtreatmentplanningand
maintainedinastateofequilibrium.
 Biomechanics
 Occlusion
 Esthetics

6. Methods of Analysis
Finite element analysis –Siegele 1989, Chelland 1991
Determinedthedistributionandconcentrationofstrainand
deformationwithinimplantandstatedthatforcedistributionto
surroundingboneoccursatcrestalboneandlevelofthirdscrew
thread.

7. Birefringence Analysis
Done on plastic model utilizing polarized monochromatic light.
Load Measurement : Lundreg 1989, Montag 1991
PrecisedataaboutforcesexertedonImplanttosupporting
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
Anyapplicationofenergy,eitherinternalorexternaltoa
structure,thatwhichinitiates,changesorarrestsmotion.
RelatedFactors
 Magnitude
 Duration
 Type
 Direction
 Magnification

9. Magnitude
Anatomicregionandstateofdentition.
Craig,1980
Molar - 390–880N
Canine - 453N
Incisor - 222N
Parafunction- 1000Psi
Colaizzi,1984
Completedenture- 77–196N
Carlsson&Haraldson,1985
Denturewithimplant- 48–412N

10. Duration
Mastication- 9mt/daywith20to30psi
Swallowing- 20mt/daywith3to5psi
Type
Compressive,TensileandShear
Cowin1989
Bone- Strongest-Compression
- 30%weaker-tension
- 65%weakest–shear
Compressiveforce- Maintainintegrity
Tensileandshear- Disruptsintegrity

11. Direction
On centric vertical contact
Angleload Axialload
Greatertensile&shearstress Greatercompressive
stress
Misch1994
30%offsetload–Decreasescompressivestrength–11%
-Decreasestensilestrength–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
Productofinclinedresultantlineofforceanddistancefrom
centerofrotation.
Torque = ForcexDistance
Naturaltooth- Apical1/3
rd
Chelland,1991
Implant-Firstthirdscrewlevel.
Force
 Vertical-towardssupportingbone
 Lateral-awaysupportingbone–Createsleverarm-
torque

14. FORCE DISTRIBUTION
Chelland1991, Weinberg,1994
Reiger1990 Implant
Naturalteeth Rigidlyfixed
Periodontalligament Stiff
Flexion Concentratesatcrestalbone
Evenforcedistribution &1
st
3threadlevel
Increase
Rootlength–increaseinsurfacearea-betterforcedistribution.
Implantlength–Initialmobilization
&

15. FORCE DISTRIBUTION PRINCIPLES
SystemComponents
 Verticalelement–toothorimplant
 Connectingelement
 Supportingmedium–periodontalligamentorbone

16. FlexibleMedium

17. StiffMedium

18. FlexibleandStiffMedium

19. DIFFERENTIAL MOBILITY
Qualitativedifferencebetweentheflexionofperiodontal
ligamentandstiffnessofosseointegration.
Micromovement
Naturalteethwithgoodbone
Willmovelaterallyapproximately0.5mm
Measuredocclusally.
MicronMovement–Weinberg,Rangert,1994
Implantcanmovelaterally0.1mmorlessmeasured
occlusally.

20. NaturalTeeth Implant
Periodontalligament-flexion Rigidlyfixed–stiff
Evenforcedistribution Concentrationatcrestalbone
0.5µmmovement 0.1µmmovement
Shockabsorber Rigid
Reducesthemagnitudeof Increasesthemagnitude
stress
Occlusaltrauma– Nosuchwarningsignsonly
Signsofcoldsensitivity, bonemicrofracture
Wearfacets,Pits,Driftaway
&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
 Contactwithfirststagecoverscrewandsecondstage
permucosalextension.
 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,
 Eliminateposteriorcontactduringprotrusionandlateral
excursion.
 Prosthesiscomeincontactonlyduringintercuspation.

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
 Naturaltooth–permanentlycementedsubstructure
telescopiccrown
 Implantsupportedprosthesis–overcrown,copingwith
temporarycement
Tend to Loosen
To eliminate, permanent cementation rather than fixed retrievability

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

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

30. FOUR CLINICAL VARIANT WITH IMPLANT LOADING
Includes
 Cuspalinclination
 Implantinclination
 HorizontalImplantOffset
 ApicalImplantOffset

31. CuspalInclination
Increasein10°increased30%torque
ImplantInclination
Increasein10°Increased5%torque

32. HorizontalImplantOffset
Increasein1mmincreased15%torque
ApicalImplantOffset
Increasein1mmIncreased5%torque

33. StaggeredImplantOffset–Rangert1993
Staggered buccal and lingual offset
Tripod Effect
Compensates torque
Implantplaced1.5mmbucalandlingualfromcentrelineto
achieveTripodism.

34. Weinberg1996
Inmaxilla,lingualoffset-increased24%torque
Buccaloffset-Decrease24%torque
Maxilla - Tripod–increasein24%torque
Mandibular- Tripodism
Maxilla - Asfarasbucally

35. Weinberg,1996
Inposteriorworkingside,occlusion.Producesbuccally
inclinedresultantlineofforceonmaxillaandlinguallyinclined
resultantlineofforceonmandible.
Reduces 73% of torque in mandible

36. THERAPEUTIC BIOMECHANICS
 Decreasecuspalinclination
Itreducesthedistancebetweenimplantandresultantlineof
force.

37.  Crossocclusion
Buccolingualrelationcrossocclusion
Reduces horizontal implant offset
Reduces torque

38.  ImplantPosition
Implantheadasclosetocenterlineofrestoration–
Reduceshorizontaloffset.

39. PHYSIOLOGIC VARIATION –CENTRIC RELATION
Kantor,Calagna,Calenza,1973.
Centricrelationrecordshowphysiologicvariationof±
0.4mm
Weinberg1998
Occlusal anatomy modified to 1.5mm horizontal fossa
Produce vertical resultant line of force within expected range of
physiologic variation.

40.  AnteriorVerticalOverlap
Steepverticaloverlap Lesssteep
ExtremeTorque LessTorque

41. BIOMECHANICS AND RESORPTION PATTERN
PosteriorMandible
Boneresorbsalongrootinclination
Therefore,posteriormandible–boneresorblingually
ReactivelyBiomechancis
Lingualpositionofrestoration+
Buccalimplantplacement-increasedtorque

42.  Therapeutically
Canbedoneby
 Reducedcuspinclination
 Implantheadclosetocentrelineofrestoration
 Angulatedabutment-parallelism

43.  PosteriorMaxilla
Reactively
 Restrictedmaxilla
 Locationofsinus
 Buccalcorticalplatefracture
 Unfavourablebiomechanics

44. Therapeutically
 Cuspalinclination–reduce
 Headofimplantclosetocenterofrestoration
 Angled/custom–reangulatedabutment
 Crossocclusion
 1.5mmhorizontalfossa.

45. AnteriorMaxilla
Reactively
Esthetically- LabiallyProclined
- Steepverticaloverlap

46. Therapeutically
 Lingualhorizontalstop–redirecttheforceasverticallyas
possible.
 Angledabutment
 Implantheadclosetocenterofrestoration

47. COMPLETE EDENTULISM AND BIOMECHANICS
 Screwlooseningnotcommonthesepatients
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
 Increaseinsurfacearea
 Limitedboneheight
 Uponremovaloffailedstandardsizeimplant
 Widerimplant - Abutmentscrew2.5mm-
Largersize–tighterjoint–
overallstrengthincreases

49. BONE DENSITY AND BIOMECHANICS
Density ∞ Strength
∞ Amountofcontactwithimplant
∞ Distributionanddissipationofforce
Misch1995
 FEMstudy–stresscontourisdifferentforeachbone
density.
Withsameload
D1 - Crestalstressandlessermagnitude
D2 - Greatercrestalstressandalongimplantbody
D4 - Greateststressandfartherapically

50. BONE DENSITY AND TREATMENT PLAN MODIFIER
 Prostheticfactors
 Implantnumber
 Implant–Macrogeometry
 Implant–Design
 Coating
 Progressiveloading

51. PROSTHETIC FACTOR
Asdensitydecreases,biomechanicalloadshouldalso
decreased
 Shortenedcantileverlength
 Narrowoclusaltable
 Offsetloadminimized
 RP
4>FP
1,FP
2,FP
3,removalatnight
 RP
5–forcesharedbysofttissue
 Forcedirectedalonglongaxisofimplant

52. ImplantNumber
IncreaseinnumberIncreaseinfunctionalloadingarea
ImplantMacrogeometry
Length
 D1 - 10mm
 D2 - 12mm
 D3 - 14mmwithV-shapedthreadscrew
DensitydecreasedLengthincreased

53. Width
 Increaseinwidth–increaseinsurfacearea
 1mmincreases30%increaseinsurfacearea
 D3&D4widerimplants
ImplantDesign
 Smoothcylindricalimplant–shearforceatInterface–
CoatingwithHA/Titanium
 Titaniumalloy(Ti-6Al-4V)exhibitbestbiomechanical,
biocompatible,corrosionresistance.
Coating
 Increasedbonecontactarea
 Increasedsurfacearea

54. ProgressiveLoading
Misch1990
Gradualincreaseinocclusalloadseparatedbyatime
intervaltoallowbonetoaccommodate.
Softertheboneincreaseinprogressiveloadingperiod.
Protocol
Includes,
 Time
 Diet
 OcclusalContacts
 ProsthesisDesign

55. Time
Twosurgicalappointmentsbetweeninitialimplantplacement
andstageIIuncoverymayvaryondensity.
 D1 - 5Months
 D2 - 4Months
 D3 - 6Months
 D4 - 8Months
Diet
 Limitedtosoftdiet–10pounds
 Initialdeliveryoffinalprosthesis-21pounds

56. OcclusalMaterial
Initialstep–noocclusalmaterialplacedoverimplant
Provisional–Acrylic–lowerimpactforce
Final-Metal/Porcelain
Occlusion
 Initial - Nooclusalcontact
 Provisional- Outofocclusion
 Final - Atocclusion

57. ProsthesisDesign
Firsttransititional–Noocclusalcontact
Nocantilever
Secondtransititional-Occlusalcontact
withnocantilever
Finalrestoration-Fineocclusaltableandcantilever

58. SINGLE TOOTH IMPLANT AND BIOMECHANICS
 Requiresgoodbonesupport
 Controlofocclusalleverparalleltolongaxis
 Accessfororalhygiene

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
 Activezone
 Occlusalloadingparalleltolongaxis

62. Cantilever Prosthesis and Biomechanics
 Itresultingreatertorquewithdistalabutmentasfulcrum.
 MaybecomparedwithClassIleverarm.
 Mayextendanteriorthanposteriortoreducetheamountof
force
Itdependsonstressfactors
 Parafunction
 Crownheight
 Impactwidth
 ImplantNumber

63. Archform
English1993–APSpread
 Cantileverlength=APspreadx2.5
 Tapering - canineandposteriorimplantswith
anteriorcantilever
 Square - Anteriorimplantwithposterior
cantilever

64. TaperingOvoidSquare
LessdenseboneAnteriorcantileverwithprosthesisDistal
implants,placedtoincreaseAP-spread.
Maxilla-moreimplantsrequiredthanmandible

65.  Sufficientboneheightexisttoplacelongimplant,
 Avoidcontactoncentralincisorsduringprotrusion,labial
excursionandmaximumintercuspation
CANTILEVER FIXED PARTIAL DENTURE

66.  Groupfunction-lateralmovement
 Avoidloadingoncanine
 Lateralguidanceprovidedbycentralandlateralincisor

67. Twoimplantsupportingafirstmolarand2
nd
premolarwith
1
st
premolarcantileverActivecuspeliminatedcaninepalatal
structures.

68. Threeimplantsplacedwith Twoimplantsrisky
2
nd
premolarascantilever and/orcontraindicated

69. MANDIBULAR FLEXURE
Picton1962
 Statedthatmandibularmovetowardsmidlineonopening
Becauseofexternalpterygoidmuscleonramusofmandible
 Medialmovementoccurdistaltomentalforamenand
increasesasitapproachesramus.
James1980&Burch1982
 Movement - 0.8mm - 1
st
molar
1.5mm - Ramusarea

70. FLEXION
Implant - Naturalteeth - mandible
0.1mm 0.5mm 10to20times
CompletecrossarchsplintingofposteriormolarMandibleflexion
Lateralforce
 Bonelossaroundimplant
 Lossofimplantfixation
 Materialfracture
 Unretainedrestoration
 Discomfortonopenings

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 directlyrelated to implantwidth
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 side\groove-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