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Biomechanics of dental implants Part 1

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hello everyone welcome to prostohub and

myself Dr Jones now so today we are

going to start off with a new topic that

is biomechanics of dental implants

the contents include introduction

natural tooth versus implant biomechanics

biomechanics

the different types of loads that is

applied under implants the stress strain

relationship and hook slow

the first delivery and failure

mechanisms fatigue failure scientific

rationally for Implant design single

tooth implant by mechanics biomechanics

and Candy liver processes and framework

as well as Misfit the treatment planning

based on biomechanical risk factors and

finally the conclusional references so

before getting into detail I request

everyone to please do like and share my

channel and if you like this video

please do share it among your friends

and if you have any queries topic

suggestions feedbacks you can comment

below this video or you can mail me at

this mail ID so let's start

into the introduction to biomechanics is

defined as the process of analysis and

determination of loading and deformation

of bone in a biological system that is

it is a response of the biologic tissues

to the applied lobes and biomechanics

comprises of all kinds of interaction

between the tissues and organs of the

body and the forces acting on them and

we know that dental implants function to

transfer the load to the surrounding

biological tissues and so the primary

functional design objective of an

implant is to manage these biomechanical

loads in order to optimize the implant

supported processes function and it is

very important to understand and apply

these biomechanical principle in each

and every stage that is from the

planning stage up to the final

prosthetic restoration and ignoring them

inevitably can lead to failure

next let us see natural tooth versus

implant biomechanics so in detail about

this we have already discussed in our

implant occlusion session so some of the

points are natural tooth it's anchored

into the bone by flexible periodontal

ligament and which is the viscoelastic

shock absorber which reduces the amount

of stress transmitted to the boat

whereas in case of implant there is no

PDL it is rigidly fixed by functional

ankylosis and the concentration of

stresses in implant mainly occurs at the

Crystal region now again when there is a

premature conduct or an occlusal trauma

there is precursor signs in case of

natural teeth that is a cold sensitivity

where faces pits drift away and tooth

mobility and these precursor signs are

reversible that is they can be corrected

by occlusal adjustment or a reduction in

force magnitude which will reduce the

stress magnitude whereas in case of

implant the initial reversible signs and

symptoms of trauma are totally absent

and these stresses can result in bone

micro fracture bone loss which

ultimately leads to Mechanical failure

of the implant components next the

elastic modulus of a tooth is closer to

the Bone than any of the currently

available dental implant biomaterial

whereas in case of implant it differs by

5 to 10 times from the surrounding bone

structure in case of elastic modulus now

the greater the difference in this

flexibility between the two material

greater will be the potential relative

motion generated between the two

surfaces and the endoster region

next the proprioceptive information

relayed by teeth and implant also

differs in quality that is the tactile

sensitivity is high for natural tooth

that is it can sense up to 10 micrometer

particles and it delivers a rapid sharp

high pressure that triggers the

proprioceptor mechanism whereas in case

of implant the tactile sensitivity is

less that is it can detect only up to 25

micrometer particles and implants

deliver a slow dull pain that triggers a

delayed reaction if any

the next the surrounding bone of natural

tooth is developed slowly and gradually

in response to these biomechanical loads

whereas in case of implant the bone

formation is performed by the dentist in

a much more rapid and intense fashion

next is about the lateral Force so when

there is a lateral force or natural

tooth it is dissipated rapidly away from

the crust of the bone towards the apex

of the tooth that is the fulcrum to the

lateral forces at the apical third and

this mechanism reduces the crystal loads

and when there is a lateral Force there

is a rapid primary movement of 56 to 1

or 8 micrometer in case of natural teeth

whereas in case of implant the lateral

Force gets concentrated at the Crystal

region this is because there is no

primary rapid movement of the implant

only it exhibits a secondary movement

that is only up to 10 to 15 micrometer

this again causes concentration of

stress at the Crystal region so whenever

there is an occlusal trauma the tooth

moves to dissipate these stresses and

strains and after the offending trauma

is eliminated tooth returns back to its

original position within the limits of

magnitude of movement that has taken

place whereas in case of implant

Mobility can take place under occlusal

trauma but when the offending trauma is

eliminated an implant rarely returns

back to its original position but

instead its failure occurs so these are

some of the points in under natural

Truth Versus implant biomechanics to

know in detail you can watch the implant

occlusion Session One

the loads applied on implants so excess

load on an Osteo integrated implant may

result in mobility of the supporting

device or it may fracture an implant

component or body so under function

there is occlusal load whereas when

there is absence of function perioral

forces can happen that is a frequent

horizontal loads and also mechanical

loads on abutment due to a non-passive

processes so biomechanics help us to

understand such physiologic and

non-physiologic load and we can

determine which type of load renders

more risk and the goal of treatment

planning should be to minimize and

evenly distribute a mechanical stress in

implant system and continuous bone

now let us see the three basic methods

of loading in an implant so loading

simply means applying a force to an

object and there are three basic methods

of loading in biomechanics first one is

compression which involves a stress that

compacts the structure so compression

compacts the structure whereas tension

it involves pulling the structure apart

and finally Shear involves pushing the

structure eccentrically and the

torsional loading involves twisting of a

structure however when seen in cross

section torsional loading is essentially

the same as Shear for an individual unit

of the structure so these different

means of loading substantially impact

the way a structure behaves and for

bones these loading characteristics

produces different but predictable

fracture patterns that is the

compressive forces compresses an object

whereas tensile forces pulls the objects

apart and Shear Force is on implant

causes sliding now let us see the

features of compression

so these compressive forces tends to

push the mass towards each other and it

maintains Integrity of bone in plant

interface and this is the one which is

accumulated best that is cortical bond

is strongest under compression and the

Siemens retention screws implant

components and won't implant interfaces

can accommodate greater compressive

forces than tensile or Shear forces and

so compressive forces should be the

dominant one in implant prosthetic occlusion

occlusion

so the compressive forces

helps to maintain the Integrity of bone

implant interface whereas the tensile as

well as Shear forces tends to distract

or disrupt such an interface so Shear

forces are most destructive that is

cortical bone is weakest to accommodate

Shear forces

so these forces should be less whereas

compressive forces should be the

dominant one in plant prosthetic occlusion

next let us see the stress strain

relationship so what is stress and

strain they are terms used to describe

the ability of an object to withstand

external forces so when a force is

applied to a material the internal

structure of the material undergo

certain changes which is calculated by

formula Force per unit area and that is

called as stress whereas the deformation

of material caused by the external force

is called as string now a relationship

is needed between the applied stress

that is imposed on the implant and

surrounding tissue and the subsequent

deformation which is given by the stress

strain curve and here comes the

significance of Hook's law so what is

Hook's Loop hooke's load dictates that

stress is directly proportional to

straight so here

you can see that initially

so initially in this graph

this obeys the hook slope that is stress

is directly proportional to strain

and once a certain strain is reached the

material begins to deform so here you

can see once the certain strain is

reached the material begins to deform

and it will no longer assume its

original shape when the stress is

released and this point is called as the

yield point

so here you can see up to this stage the

material shows elastic Behavior but

after the yield point the material shows

plastic behavior and at the end this

point is called as the failure point

where fracture or failure of the

material occurs

so hook slow is the basis for predicting

the biomechanical properties of implants

so hooke's law states that stress and

strain are directly proportional and

that is seen at the initial portions of

a number defines the relationship

between stress and strain for a given

material during this linear aspect of

the stress strain curve and that is the

Young's modulus of elasticity so stress

is equal to modulus of elasticity into

strength so basically the modulus of

elasticity of the Young's moduli

describes the elasticity of a material

and it is calculated by dividing stress

by straight or visually it is the slope

of the line created under stress strain

curve through the elastic portion of the

curve and components with high moduli

are stiff like stainless steel on the

other hand low mode line means soft

materials like ultra high molecular

weight polyethylene which is used in Orthopedics

Orthopedics

so as per the stress trained

relationship once a particular implant

system is selected the only way for an

operator to control the strain

experienced by tissue is to control the

applied stress or change the density of

bone around the implant so we have

already said in the previous slide that

closer the modulus of elasticity of the

implant to the biological tissue the

less the relative motion at the implant

tissue interface next let us understand

the manner in which forces are applied

to the dental implant restoration and

also the failure mechanism these are

important to avoid complications so here

comes the importance of moment or Torque

so what is moment.torque it is the force

which tends to rotate a body

so in addition to axial Force there is a

moment on the implant which is equal to

the magnitude of force multiplied by the

perpendicular distance between the line

of action of the force and the center of

the implant so in this picture you can

see that this is the

line of action of force this is the

perpendicular distance

and here the moment of torque is

calculated by the formula f multiplied

by D that is the distance between line

of action and center of implant

multiplied by the magnitude of force now

the moment loads can be destructive in

nature and may result in implant bone

interface breakdown bone resorption

screw loosening and bar or Bridge fracture

now there are three clinical coordinate

axes and a total of six moments May

develop about the three clinical

coordinate axis so here you can see in

the picture they are foreign

so these are the three clinical

coordinate axes and a total of six

moments May develop around these and

these moment Lots induce micro rotations

and stress concentration at the crest of

the alveolar Ridge at the implant to

tissue interface and which leads

inevitably to Crystal bone loss and

there are also three clinical moment

arms in implant industry that is

occlusal height can deliver length and

occlusal width now let us see these

among the three clinical moment arms the

first one that is the occlusal height

which serves as the moment arm for Force

components directed along the

ratiolingual axis and mesial distal axis

now the force component along the

vertical axis it's not affected by the

occlusal height because there is no

effective moment R so when there is a

force that is direct along the vertical

axis the perpendicular distance between

line of action of force and center of

implant is zero and so there is no

effective moment arm however the lateral

loads can introduce significant moment arms

arms

and in case of division a bone the

initial moment arm at the Crest is less

than that of division C or D bone

because the crown height its greater in

division C or D both so the treatment

planning must take into account this

initially compromised by mechanical environment

next the second clinical momentum that

is cantilever link so cantilever or

horizontal offset we have already

discussed in detail in our implant

protective occlusion session three so we

know that cantilever processes are the

ones which are fixed at only one end and

cantilever extensions or offset loads

from rigidly fixed implant results in

large moment load so here is a picture

that illustrates two implants that are

placed 10 millimeter apart

so these are two implants place 10

millimeter apart and the cantilever

distance is 20 millimeter so

when there is an when there is a

situation like this when two implants

are designed 10 millimeter apart

Splendid with a cantilever of 20

millimeter when a force of 25 lbs is

applied on the cantilever it is resisted

by 50 lbs force on the measal implant

and the distal implant which act as a

fulcrum has got a force of 75 lbs so

here it is a condition that is similar

to class 1 liver and the mechanical

advantage is calculated to be 2. so to

know in detail you can watch the session

3 of implant protective occlusion and

another greatest determinant for the

length of cantilever is the magnitude of

force so patients with severe bruxism

should not undergo restoration with any

other important determinant is the

anterior posterior spread so this is the

distribution distance between the most

anterior and most posterior implant so

this is called as the anterior posterior

spread and greater the anterior

posterior spread smaller the resultant

loads on the implant system from the

cantilevered forces because of the

stabilizing effect of the anterior

posterior distance so as per mesh the

amount of stress

will be less when you increase the

anterior posterior spread that is forced

by area when the area increases the

force decreases so in biomechanically

compromised environments such as poor

quality bone The Strain to the crystal

bone can be reduced by increasing the

anterior posterior spread of the implant

and an anterior posterior spread that

minimizes the distal cantilever and

establishes well distributed four point

stability will probably contribute to

both implant as well as prosthetic

success and clinical experiences suggest

that distal candle liver should not exceed

exceed

2.5 times the anterior posterior spread

now let us see the recommendations by

Mish so candle liver length is

determined by the amount of stress

applied to the system

and generally distal candle liver should

not exceed 2.5 times the anterior

posterior spread patients with para

function should not be restored by

cantile liver regardless of other factors

factors

Square Earth form involves smaller

anterior posterior spread between

splintered implant and should have

smaller length cantilever and tapered

Arch form

can be restored with larger anterior

posterior spread and large cantilever design

the next clinical moment arm is occlusal

width so widening the occlusal table

greater will be the force developed to

penetrate a bolus of food and also a

restoration that mimics the occlusal

anatomy of natural teeth often results

in offset load and also there is

increased risk of porcelain fracture so

wide occlusal table increases the moment

arm for any offset or closer load and so

in order to reduce the rotation or

facial lingual tipping you can either

narrow the occlusal table or adjust the

occlusion to provide more Centric contacts

contacts

so to summarize a vicious destructive

cycle can develop with the moment loads

which can result in Crystal bone loss so

once there is a crystal bone loss

automatically the occlusal height

increases and once this occlusal height

moment arm increase there is increased

facial lingual micro rotation and

rocking which again causes more stress

to the crustal bone which results in

Crystal bone loss so unless the bone

increase in density and strength this

cycle continues and results in implant

failure if this biomechanical

next is fatigue failure which is

characterized by Dynamic cyclic loading

conditions so there are four fatigue

factor that significantly influence the

likelihood of fatigue failure in implant

industry and they are biomaterials macro

geometry Force magnitude and number of

loading Cycles so we have to discuss

this in detail and we will be continuing

this in our next session

so thank you all for watching my video

please do like share and subscribe my

channel if you are finding these videos

useful and if you have any queries topic

suggestions or feedbacks you can comment

below this video or you can mail me at

this mail ID so it's buy from Pro Soha

until the next session thank you all

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