in the name of god
DESCRIPTION
IN THE NAME OF GOD. Implant body size: A biomechanical and esthetic rationale. Presented by:Dr.m.akouchakian Supervised by: Dr. Mansour Rismanchian And Dr.saied Nosouhian Dental of implantology Dental implants research center Isfahan university of mediacal science. - PowerPoint PPT PresentationTRANSCRIPT
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IN THE NAME OF GOD
m.akouchekian 1
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Implant body size:A biomechanical and esthetic rationale
Presented by:Dr.m.akouchakian
Supervised by: Dr. Mansour Rismanchian
And Dr.saied Nosouhian
Dental of implantology
Dental implants research center
Isfahan university of mediacal science
m.akouchekian 2
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m.akouchekian 3
Implant body size:A biomechanical and esthetic
rationale
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The initial treatment plan for implan dentistry:
include the ideal implant size(based primarily
on biomechanic and esthetic considerationse)
primarily:existing bone volume in height,
width and length determined The size of
implant
Introduction
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1) The prothesis first is planned
2) The patient force factors are considered to evaluated
the magnitude and type of force
3) The bone density is evaluated in the regions of the
potential implant sites
4) The key implant positions and the implant number
are selected
5) The next consideration is the implant size
Ideal treatment plan sequence
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1) The character of the applied forces
2) The functional surface area over
which the load is dissipated
The implant size directly affects the functional
surface area
Biomechanical load management based on:
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Although several conditions may cause crestal bone
loss, one of these may be prosthetic overload.
Excessive loads on an osteointegrated implant may
result in mobility of the supporting device, even after
a favorable bone-implant interface has been obtained.
Character of forces applied to implantStress and strain
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Excessive loads on the implant result in
increased strain in the bone
Microstrains on the bone may affect the bone
remodeling rate ,which result in bone loss
The amount of bone strain is directly related to
the amount of stress applied to the implant-
bone interface
Character of forces applied to implantStress and strain
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1) Type
2) Magnitude
3) Duration
4) Direction
5) Magnification
Five distinct forces factors
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The magnitude of bite force varies as a function of
anatomical region and state of dentition(10 to 350
Ib)
The magnitude of force is greater in molar region,
less in canine area and least in incisor region
The average bite forces increase with parafunction
(approach 1000 Ib)
Force magnitude
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Under ideal condition, the teeth come together
during swallowing and eating ( less than 30
minutes)
In parafunctional habits, teeth may be in contacts
in several hours each day
Increase in force duration directly increases the
risk of fatigue damage to cortical bone (e.g, shin
splints in runners)
Force duration
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Although fatigue damage to alveolar bone has not yet
been reported in the literature.
Roberts et al. Report:
the bone around an implant may be remodeled at a
rate of 500% each year after loading, compared with
normal trabecular physiologic remodeling around a
tooth of 20% to 40% per year
The dramatic increase in remodeling rates may eventually
lead to fatigue damage and resultant bone IOSS.
Force duration
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Three type of forces may be imposed on
dental implants:
1) compression
2) tension
3) shear
Force type
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Bone is strongest when loaded in
compression, 30% weaker when subjected
to tensile and 65% weaker when loaded in
shear
Force type
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An attempt should be made to limit shear
forces on bone
Increased width of implant:
1) decrease offset loads and
2) Increase the amount of the implant-bone
interface
Force type
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The forces to an implant body are typically
greatest at the crestal bone interface
Angled loads to the implant produce angled loads
to the crest module of the implant
the direction of the load has a significant effect
on the magnitude of compressive and lateral load
components.
Force direction
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By increasing the angle of the load by only 6
degrees , the lateral load is increased by 233%
Force direction
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Angled loads increase the amount of shear loads to the bone
The implant should be inserted perpendicular to the curve of wilson
and spee
The anatomy of the mandible and maxilla places significant
constraints
Bone undercuts further constrain implant placement and thus load
direction imposed on the implant
The premaxilla is 12 to 15 degrees off the long axis of load
To decrease the effect of angled load on the implant , the implant
may be increased in diameter
Force direction
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Force magnification
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1) Cantilevered prosthesis
2) Crown height greater than normal
3) Parafunction
Force magnification
increases the stress
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D4 bone may be more than 10 times weaker
than D1, and 70% weaker than D2 bone
Implant failure rates are 35% in D4 bone
The most important factor to decrease stress:
1) increase in implant number=> increases the
effective surface area=> decreases stress
2) increase implant size
Force magnification
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Stress = Force / Surface area
To decrease stress:
1) the force must decrease
2) surface area must increase
Increase in implant size is beneficial to
decrease stress
Surface area
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The length of the implant is directly related to the overall implant
surface area
A 10 mm cylinder implant:
increases surface area 30%> 7 mm implant
20%< 13 mm long implant
Rationale for longer implant length
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A common axiom has been to place an implant as long as possible
The length of implant corresponds to the height of available bone
The available
in the anterior mandible:
1) bone height is greater
2) Bite forces are lower
3) bone density is greater
The posterior have less bone height and the implant cannot engage
the dense opposing cortical plate
ThePosterior maxilla associated with the highest failure rate because
less height and less dense
Rationale for longer implant length
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Implants longer than 15 mm provide greater
stability under lateral loading
Increasing the length beyond a certain dimension
may not reduce force transfer proportionately.
Rationale for longer implant length
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The length of the implant in favorable bone
quality and crown height may range from 10 to
15 mm,and 12 is usually ideal
length of 12 mm:usually ideal under most patient
force and bone density conditions
15 mm :suggested in softer bone types
Rationale for longer implant length
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All implant lengths exhibited 80% to 100%
of the stress in the crestal 40% of the
implant length
Rationale for longer implant length
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1) Overheating because preparation a longer osteotomy(D1,D2)
2) Threaded implant may not readily engage the denser bone of the
apical cortical plate(D3,D4)
3) Implant threads may strip along the rest of osteotomy especially in
D3 or D4 bone
4) Excessively long implants do not transfer stress to the apical region
(most of the stresses are transmitted within the crestal 7 to 9 mm of
bone )
5) Advanced surgical procedures may be needed (nerve repositioning
and sinus graft)
6) The apical end of implant will not benefit from the sinus bone graft
Disadvantages of longer implants
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The posterior region of jaws usually have
the least height of existing bone and have
higher bite forces
Under some clinical conditions, stress
transfer patterns may be similar between a
short and a longer implant
Rationale for shorter implant length
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1. Less bone grafting in height a) Less time for treatmentb) Less cost for treatmentc) Less discomfort
2. Less surgical risk of :a) Sinus perforationb) Paresthesiac) Osteotomy trauma from heatd) Damage to adjacent tooth root
3. Surgical ease:a) decreased inter arch spaces b) Less inventory/ cost
Advantages of short implants
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In the majority of articles, implants 10 mm or
smaller have increased failure rates
Implants shorter than 10 mm had a survival rate
of 81.5% whereas longer implants had higher
than 95%
Disadvantage of short implants
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The failures associated with short
implants, often occurred after prosthetic
loading (especially within the first 12 to 18
months)
the surgical success was not affected by
implant length
Disadvantage of short implants
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1) Higher bite forces
2) Low bone density in the region
3) Increased crown height
4) Implant design considerations
Why the posterior short implants have higher failure rate
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The softer the bone:
the greater the implant
body length and diameter
suggested
IDEAL IMPLANT SIZE
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Over several decades, implants have gradually
increased in wide(scialom were less than 2 mm wide)
Branemark first introduced an implant body diameter
of 3.75 mm
The larger diameter implants were primarily used to
improve emergence profile
The wide diameter implant presents surgical, loading
and prosthetic advantages
Implant diameter
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1) Surgical rescue implant
2) Failed implant /immediate
3) Tooth extraction/immediate
Surgical advantages
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Because occlusal stress to the implant interfere
at concentrated at the crest of ridge , width
appears more important than height
1) Increased surface area
2) Compensate unfavorable patient force factors
3) In cantilevers , reduce the risk of overload
4) Compensate for poor bone density
5) Enhance surface for short implants
Loading advantages
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1) Improve emergence profile
2) Decrease screw loosening
3) Minimize component fracture
4) Facilitate oral hygiene(decrease
interproximal space)
Prosthetic advantages
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1) Bone trauma- drill sequence
2) Decreased facial bone thickness may lead to
recession (Because closer than 1.5mm to the
adjacent teeth or facial or palatal bone )
3) Increased surgical failure rate
4) May too close to adjacent tooth, PDL
encroachment
5) Stress shielding: the implant is so wide that strain
may be too low to maintain bone
Disadvantages of wide diameter implants
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In anterior:implant should not be wider than 5
mm
in the posterior:implant should not be greater
than 6 mm(when adequate mesiodistal space is
present and force magnitude is also observed)
When larger diameter implants can not be used
in the molar region , two 4 mm implants for each
molar should be considered
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PDL complex is a very effective organ that distributes
occlusal loads along the entire root surface
The smallest diameter roots are in the mandibular anterior
region
The canines have a greater surface area than premolars,
because they receive a lateral loads more than premolars
Natural teeth
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The maxillary molars have more roots than
mandibular molars (because the maxillary
posterior region has the least bone density)
Natural teeth
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Natural teeth
m.akouchekian 43
The natural tooth roots
indicator for width implant
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1) The diameter of natural teeth in 2 mm below the CEJ.
the implant body should not be as wide as the
natural tooth or clinical crown it replaces =>The
emergence contour and interdental papilla can not
be established properly
2) Implant should be at least 1.5mm from the adjacent
teeth
When in doubt, smaller size diameter implant should
be selected
Anterior tooth replacement
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When implants are adjacent to each other,
a minimum distance of 3mm is suggested
The size dimension of two adjacent anterior
implants should most often be reduced
compared with single implant
Multiple anterior implants
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1) The implant dimension should correspond to the
natural tooth(2mm below the CEJ)
2) The implant should be at least 1.5 mm from the
adjacent teeth
3) The implant should be at least 3 mm from
adjacent implant
4) The implant should be at least 4 mm in diameter
Implant size selection criteria in posterior maxilla
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the mandibular incisors and the maxillary lateral
incisor: 3- to 3.5-mm diameter
the maxillary anteriors, premolars in both
arches,and canine:4-mm diameter implants
The molars:5- or 6-mm diameter
The implant dimension in question is the size of
the crest module, not the implant body
dimension
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1) When the diameters of molar implants do
not provide sufficient surface area
2) Very soft bone types
3) Unfavorable force factors (i.e,
parafunction)
4) Multiple adjacent posterior teeth are
missing
The number of implants should be increased :
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m.akouchekian 49
For You’r
Attention