Biomechanical Considerations In Implant Dentistry.pdf

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1. AmrElkhadem
Lecturer-Prosthodontics
Cairo university
BIOMECHANICAL
CONSIDERATIONS IN
IMPLANT DENTISTRY

2. OUTLINE
•Anatomicalandfunctionaldifferencesbetweenrootform
implantsandteeth
•Load,overloadanditsconsequences
•Biomechanicalriskfactors:
1.Patientrelatedfactors(functional&para-functionalloads,bonequality
&quantity&morphology)
2.Implantrelatedfactors(Length,Diameter,Number,Distribution&Tilt)
3.Prosthesisrelatedfactors(Loadingtime,Prosthesismaterial,Prosthesis
height,Cantileverextensions,Prosthesisfit,Occlusion)
•Joiningteethtoimplants“thedilemma”
•Summary&takehomemessage

3. NATURAL ROOT VSROOT FORM IMPLANT
•Periodontal ligament
•Root surface area
•Multi-rooted teeth
and tooth cross
section

4. THE LIGAMENT
•Theligamentallowsforslightadaptiveand
compensatorymovements.
•Itallowsforapicalpropagationofthestressesupto
theapex(rootlengthhasagreatvalue)

5. SURFACE AREA
•Therootsurfaceis
relativelyasmooth
taperedcomparedto
threadedrootsurface

6. MULTI ROOTS
•Posteriorteetharemultirooted.
Therootcervixisusually
elliptical.Implantshaverounded
crosssectionusuallynarrower
thanthecounterpartroot

7. INTRAORAL LOADS
•Occlusalloads
•Loads from perioral musculature
•Loads from mandibular flexure

8. OCCLUSALLOADS
•Perpendicular to occlusalplane
•Short duration (5-10 mins/day)
•Males > females
•Natural teeth: 470N canine –
723N 2
nd
molar
•Complete dentures 50-60N
•Implant supported Overdenture
112-196 N

9. PERIORAL FORCES
•Mainlyduringswallowing
•Moreconstant(20min/day)
•Lightermagnitude(15-20%of
occlusalload)
•Horizontal

10. MANDIBULAR FLEXURE
•Occursduringmouthopeningandprotrusion
•Averageforce25-50Nappliedatthecondylar
neck
•Causesarchnarrowingandmedialrotationof
thesuperiorborder
•Effectiveonlywhenanteriorandposterior
implantsarerigidlyconnectedbilaterally

11. ARE LOAD GOOD OR BAD?
Loads applied within the physiologic tolerance of bone
and mechanical tolerance of the artificial components are
well accepted but the problem exists when the load
exceeds these tolerances

12. Consequences of overload
Biological
complications
Early
loading
failure
Marginal
bone loss
Mechanical
complications
Prosthesis
related
Abutment
related
Implant
related

13. EARLY LOADING FAILURE
•Anintegratedimplantthatfail
shortlyafterloading
•Manifested6-18monthsafter
loading
•Causedbyexcessiveloadingat
thebone-implantinterface
•Itisusuallyanasepticfailureand
notrelatedtoperi-implanttissue
inflammation

14. MARGINAL BONE LOSS
Causes:
1)Flap reflection
2)Osteotmy
3)The need to re-establish
the biologic width
4)Peri-implantitis
5)Overloading

15. FROST MODEL FOR BONE RESPONSE TO STRESSES

16. MECHANICAL COMPLICATIONS
Prosthesis
related
complications

17. Screw loosening
Screw fracture
Abutment fracture

18. Implant body
fracture

19. THE INCIDENCE OF THE COMPLICATIONS
•Mechanicalcomplicationsaremorecommonthanbiologicalones
•Formechanicalcomplicationsremovableoverdenturesusually
possesmorecomplicationsthanfixedrestorations
•Forfixedrestorationsacrylicveneerfracture,andscrewloosening
arethemostcommonformswhileimplantbodyfractureistheleast

20. THE WEAK LINK (A PART OR AN INTERFACE?)

21. RISK FACTORS
•Biomechanicalriskfactors:
1.Patientrelatedfactors(functional&para-functionalloads,bone
quality&quantity&morphology)
2.Implantrelatedfactors(Length,Diameter,Number,Distribution
&Tilt)
3.Prosthesisrelatedfactors(Loadingtime,Prosthesismaterial,
Prosthesisheight,Cantileverextensions,Prosthesisfit,
Occlusion)

22. I.PATIENT RELATED RISK FACTORS
A.Functional and Para-functional loads
B.Bone quality, quantity and morphology

23. FUNCTIONAL LOAD (OCCLUSALFORCES)
•Theforcemagnitudevaries
frommalestofemalesand
amongindividuals
•Forcesdeliveredfromnatural
dentition>implantsupported
dentures>completedentures
2 implants when opposed by CD 4 implants when opposed by natural
teeth

24. PARAFUNCTIONALHABITS
a)Clenching
b)Bruxism
c)Tongue thrusting

25. a)CLENCHING:
•Ahabitthatgeneratesconstant
forcesexertedfromoneocclusal
surfacetoanotherwithoutany
lateralmovement
•Symptoms includemuscle
tenderness,andsometimestooth
sensitivity
•Theevidentintraoralsignsinclude
cervicalabfractions,restorative
materialfatigue,toothfremitus,and
scallopedtongueborder

26. a)CLENCHING:
•Precautions:
1.Use additional implants preferably with greater diameter
2.During healing relief the temporary removable dentures over the covering
mucosa to avoid pressure necrosis that cause soft tissue dehiscence over
the implant
3.If the natural canine exist plan for canine protected occlusion
4.If the canine is to be restored with an implant or a ponticplan for mutually
protected occlusion
5.Construct a night guard relieved over the implant after restoration

27. b)BRUXISM:
•Isthehorizontalnonfunctionalgrindingof
teeth
•Theforcesmayoccurwhilethepatientis
awakeorasleep
•Theforcemagnitudeisincreased4-7times.
Forcedurationextendstoseveralhours
•Bruxismcanbeclassifiedasmildmoderate
andsevereaccordingtotheseverityof
wear
•Musclepain,abfractions,limitationofmouth
openingmaybeassociated

28. b)BRUXISM:
•Thesideeffectsaremorethanclenching
duetothegenerationoflateralforces
•Severebruxersarecontraindicatedfor
placingimplants
•FormildandmoderatetheuseofSRSis
recommendedtotrybreakingthehabit
•Increasethenumberanddiameterof
implantsused
•Anightguardisindicatedtoeliminate
nightbruxismafterrestoration

29. c)BONE QUALITY:
According to Lekholm& Zarbbone is classified into four qualities from 1-4
according to its density (1985)
In1988Mischproposedfourbone
densitiesaccordingtothe
macroscopicarchitecture:D1,D2,
D3D4

30. •Radiographicallybonequalityis
classifiedaccordingtotheradio
densityinHUinto:
D1:>1250
D2:850-1250
D3:350-850
D4:150-350
D5:<150

31. •Themodulousofelasticityofthe
bonedependsonitsdensity.It
rangesfrom15,000tojust150
Mpafromthehighesttolowest
density
•Thedevelopedmicrostrainwill
consequentlydifferbetween
differentbonequalitiesunder
thesameload
•Forthisreasonimplantfailure
reportedinpoorqualitybone
mightreach30-45%insome
clinicalreports

32. •When planning implants
in poor quality bone:
1)Increasethenumberof
implants
2)Rigidlysplintimplants
3)Uselongerandwider
implants
4)Avoidforcemagnifiersas
cantileverextensions

33. d)BONE QUANTITY & MORPHOLOGY
•Theavailableisdefinedbytheremainingheight,
with,thicknessandangulationinrelationtothe
occlusalplane
•Atwood1963classifiedtheresidualridgeinto6
classesfromItoVI
•Misch&Judy1985classifiedtheedentulous
ridgeintodivisionsA-Dwithspecialreferenceto
deficiencieinheightandwidth

34. •Withtheadvancementofridgeresorptionan
unfavorablebiomechanicalsituationdevelops
because:
Thedecreaseinbonewidthlimitthediameterof
implantsused
Thepatternofresorptionusuallyshiftthebone
volumelingualtotheidealpositionputtingthe
implantlongaxisinanoffsetpositiontotheocclusal
loads

35. •Withtheadvancementofridgeresorptionan
unfavorablebiomechanicalsituationdevelops
because(cont):
Thedecreaseinboneheightlimitthenumber
ofimplants,implantlength,andincreasesthe
CHS.Itmightcauseunfavorableimplant
distributionwiththedevelopmentofcantilever
situations

36. Surgically or prostheticallydriven
Use the available and
compromise the bio-
mechanics and esthetics
Go for site development so that
the implant is placed in the best
biomechanical situation
The biomechanical risk versus the
risk of surgical failure and
complications
The total cost and time of
treatment

37. II.IMPLANT RELATED RISK FACTORS
1)Implant length
2)Implant diameter
3)Number of implants
4)Implant distribution
5)Implant tilt

38. a)IMPLANT LENGTH
•Lengthofimplantsvaryfrom5mmto40-50mmin
zygomaticimplants
•Theprimaryadvantageoflongimplantsisto
assureprimarystabiiltyallowingforimmediate
loading
•Longimplantsthatengagethecrestalcortexand
thebasalcompactboneallowingfor“bicortical
stabilization”

39. DOES IMPLANT LENGTH AFFECT STRESS DISTRIBUTION IN INTEGRATED
IMPLANTS?

42. ARE SHORT IMPLANTS SUCCESSFUL?
“Survivalofshortimplantsisimprovedwithgreaterimplantlength,placementinthe
mandiblecomparedwiththemaxilla,andinnonsmokers”.JEvidBasedDentPract.2012
Sep;12(3Suppl):189-91
•Datafrom1980-2009,1353article
•Filteredto28prospectivecohortstudiesand1RCT,2611shortimplantsintheidentified
studiesranginginlengthfrom5.0mmto9.5mm
•Thefocusofthereviewwastodetermine2yearsurvivalrateofshort(<10mm)implants
•Subgroupanalyseswherethesubgroupsincludedindividualimplantlengths,smoking,implants
inthemandibleversusmaxilla,andboneaugmentationprocedures.
Conclusion:
a)Thetwoyearsurvivalrangefrom93-99%
b)Theestimateddatashowedatendencyforimprovedsurvivalratewithincreasingimplant
length,implantplacementinthemandiblecomparedwiththemaxilla,andforimplantsplaced
innonsmokers

43. DOES IMPLANT LENGTH AFFECT MARGINAL BONE LOSS?
“A systematic review on marginal bone loss around short
dental implants (<10mm) for implant-supported fixed
prostheses”. Clin Oral Implants Res.2013 Aug13
•Data from 2006 to 2012 in English. One observer only
•Meta analysis results showed that that short dental implants
(<10mm) had similar peri-implant MBL as standard implants
(≥10mm) for implant-supported fixed prostheses

44. b)IMPLANT DIAMETER
•Thisreferstothediameteratthecrestmodulearea
•Implantsaregenerallyclassifiedasnarrow,regularand
wideplatformimplants
•AstheimplantwidthincreasetheF/Adecreases(better
stressdistribution)
•Asthediameterincreasesthebodybulkincreaseswhich
allowforbetterenergyabsorptionandlessmechanical
complication

45. “Influence of implant length and diameter on stress distribution: A finite
element analysis” J ProsthetDent 2004;91:20-5

47. MINIIMPLANTS

49. DOES MINI-IMPLANTS WORK?
“Miniimplantsfordefinitiveprosthodontictreatment:asystematicreview”
JProsthetDent.2013Mar;109(3):156-64.
Datafrom1974-2012,1807titlefilteredto9.1RCT,2prospective,and6
retrospective.Themajorityofminiimplantswereplacedbyusingaflaplesssurgical
techniqueinthemandibularanteriorregiontosupportanoverdenture.
Conclusion:
a)thefirstyearISRof94.7%ofminidentalimplantsappearsencouraging,butthe
true1-yearsurvivalrateisunknown
b)Insufficientinformationaboutfailuresafterthefirstyearmakesitdifficulttodraw
conclusionsaboutthemedium-termsurvivaloftheseimplants.Currently,thereis
noevidenceforthelong-termsurvivalofminiimplants.

50. c)NUMBER OF IMPLANTS:
•Oneofthemostcontroversial
issues(Overengineeringversus
economicplans)

51. 2 implants to restore 1 missing wide molar

52. Problems:
•Cost
•Invasiveness
•Too close implant (esthetics, bone loss)

53. BranemarkNovum

54. All on 4 strategy

55. ARE THERE ANY GUIDE LINES FOR THE NUMBER OF IMPLANTS TO BE
USED?
Ante'sLaw(1926):"Therootsurfaceareaoftheabutmentteethhastoequalorsurpassthatoftheteeth
beingreplacedwithpontics"
An implant is not a tooth. There are no evidence based guidelines for how many number you
should use

56. d)IMPLANT DISTRIBUTION:
Skalakpointedouttotheimportanceofspreadingtheimplantsaswideas
possiblesothattheloadareconfinedwithintherestorationavoidingcantilevers
TheAPdistance:the
distancefromthemost
anteriorimplanttotheline
joiningthemostposteriorones

57. Adequate AP spread Anterior implant concentration
Posterior implant concentrationPoor AP spread

58. STAGGERED IMPLANTS
•Whenplacingmultipleadjacentimplantssomeclinicians
recommendoffsetplacementtominimizetheeffectof
buccolingualtipping

59. GUIDELINES FOR IMPLANT POSITIONS AND DISTRIBUTION
•Alwaysplaceimplantsatbothendsof
theedentulousspacetominimizeor
eliminatecantilevers
•Avoiddesigningrestorationswith
morethan2posterioradjacentpontics
toavoidunfavorablebendingoflong
beams
•Tryalwaystoplaceimplantsinthe
strategiclocation(canineandfirst
molar)
•Designyourcasewiththewidest
possibleAPspread
??

60. e)IMPLANT TILT
•Itwasalwaysrecommendedtoplace
implantssothattheloadspass
throughtheirlongaxis.
•Tiltingimplantsisthoughtto
accentuatestressesaroundthe
implantsbyincreasingthelateral
componentofforces
•Tiltedimplantswasusuallythought
asanerrorrelatedtopoorclinical
experience

61. INTENTIONAL IMPLANT TILTS
Have been described as a viable solution when anatomical limitations
prevent axial placement
To what
extent is it
safe?

62. CAN TILING PROVIDE A BIOMECHANICAL ADVANTAGE?

63. III.PROSTHESIS RELATED FACTORS
a)Loading time
b)Prosthesis material
c)Prosthesis height
d)Cantilever extensions
e)Prosthesis fit
f)Occlusion

64. a)LOADING TIME
•The problem exist due to stability dip (2-6) week
•Loss of primary stability due to remodeling which increases
micromotion

65. IS IMMEDIATE LOADING SUCCESSFUL?
•What type of loading (Functional or not)?
•What type of restorations?

66. PRECAUTIONS TO IMPROVE SUCCESS OF IMMEDIATELY
LOADED IMPLANTS
•Usegreaternumberofimplants
•Longerimplantswillprovidemoreinitial
stability
•Usemicroroughenedimplantsurfacethat
acceleratebonehealing
•Splinttheimplantsrigidly
•Keepitoutofocclusionifpossible(ifnot
assureclearanceduringlateralexcursions)
•Nocantileverextensions

67. b)PROSTHESIS MATERIAL
Resilient material (shock absorber) versus stiff materials ???????

68. Stiff material.
All the car is affected
No area of maximal damage
Resilient material
The maximal damage is concentrated at the impact
The driver is kept safe

69. •Stiff framework absorb and distribute the
stress in a more uniform pattern allowing for
load sharing
•Resilient materials will concentrate the
stresses at the site of load application

70. c)CANTILEVER EXTENSION:
•Cantilever are undesirable but usually
inevitable situations
•Cantilevers are force magnifiers that
cause bending moments
•The moment depends mainly on the
cantilever length

71. ARE THERE GUIDELINES FOR THE PERMISSIBLE CANTILEVER LENGTH?
•There is a consenusabout the necessity of keeping
cantilever extensions short
•No evidence based guidelines
•Some authors defined 10-12 mm as acceptable
•Other linked the length to the AP spread (1:1 or
1:1.5)
•Mischsuggested a ratio of 1:2.5 when all other
stress factors are low

72. d)PROSTHESIS HEIGHT (CHS)
•It is a vertical force magnifiers (vertical
cantilever)
•As the crown height increases the tipping
tendency increases

73. PRECAUTIONS FOR EXCESSIVE CROWN HEIGHT
•Removable overdenuresare better solution
•Use greater number of implants and splint them

74. e)PROSTHESIS FIT
•The lack of passive is a high risk situation
•The non passive restoration exerts continuous lateral force on the supporting
implants

75. f)OCCLUSION
•Implantsarenotasforgivingasteeth
•Occlusaltraumaduetopremature
contactwasreportedtocauselossof
6of8implantsinexperimental
animals
•Forfixedrestorationitis
recommendedtoprovide30microns
ofocclusalclearanceaboveimplant
restorationtocompensateforvertical
displacementoftheadjacentteeth
duringheavybiting

76. SUMMARY OF HIGH RISK FACTORS
1.Type IV bone quality
2.Parafunctions
3.Long cantilever
4.Immediate loading
5.Non passive restorations
6.Occlusalprematurity

77. COMBINING TEETH TO IMPLANT????
•What is the problems anticipated? Why?
•Possible solutions suggested in the literature regarding the type
of prosthesis, type of connection, mechanical design
considerations?
•Is there any evidence
Prepare a review on tooth to implant
connection. Delivery date “Week 9”