IN THE NAME OF GOD

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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

 

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Implant body size:A biomechanical and esthetic

rationale

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

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

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The natural tooth roots

indicator for width implant

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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For You’r

Attention