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Biomekanik Pergerakan Gigi

Ortodonti

Dr. I.B.Narmada. drg., Sp.Ort(K)
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Physiology/Anatomy

Movement/ForcesOrthodontic force Appliances

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What is needed?

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What is needed?

Tooth

Healthy periodontal ligament

Bone

Applied force

Tooth movement is dependant upon physiology of

the Periodontal ligament and Bone - i.e. Turnover

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Tooth Means of force application /delivery

Otherwise inactive

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Removeable Appliances

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Periodontal Ligament Fibres transmit forces applied to the tooth Viscostatic damping of force

Cells within PDL

Fibroblasts

Osteoblasts

Osteoclasts

Undifferentiated cells

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The Periodontium

Orthodontic force Changes in the supporting structure.

Periodontium is a connective tissue organ covered byepithelium, that attaches the teeth to the bones of the jaws andprovides a continually adapting apparatus for support of teethduring function.

4 connective tissues

Two fibrous- Lamina propria of the gingiva.

- Periodontal ligament

Two mineralized-Cementum-Alveolar bone

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Gingiva

Circular

Dentogingival

Dentoperiosteal

Transseptal fibres (Accesory fibres)

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PDL

Connective tissue interfaceseparating the tooth from thesupporting bone.

Heavy collagenous supporting

structure- 0.5mm aroundApart from fibres-

Cellular elements-mesenchymal, vascular & neural

Tissue fluids

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PDL

Constant remodeling- fibres, bone & cementum.

Principal fibres -

1. Alveolar crest group2. Horizontal group

3. Oblique group

4. Apical group

5. Transseptal group

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Role of PDL

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Physiologic tooth migration

Migration- teeth carry fibresystem

Remodeling of PDL andalveolar bone.

Resorptive surface &

depository surface
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Bone Role of Bone in the body Structural

Metabolic

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Alveolar bone

Surrounds the tooth CEJ-Lamina dura

Bundle bone- alveolar bone proper.

Volkmanns canals vascular communication with

marrow spaces. Renewed constantly functional demands.

Age- size & number of marrow spaces

Mesial & distal movement spongiosa: extraction

space- Rapid Labially- lingually- caution

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BoneStructural:

Cortical bone

slow turnover

Metabolic:

Trabecular boneconstant turnover

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Bone TurnoverControl is by systemic and local factors Osteclastsderived from perivascular cells

Osteblastsderived from monocytes

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Kidney -

P04 excretion

Ca++ resorption

Bone - Metabolic Role (systemic control)

Ca++

Serum Ca++

Serum

PTH

Vit D(1,25 DHCC)

Bone short term:

Ca++ from bone fluid

long term:

Resorption

Deposition

Gut -Ca binding

Ca absorption

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Local control Biologic electricity

Blood flow

Microfractures

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Local control

Biologic electricity

Blood flow

Microfractures

1. Pietzoelectric effect (v. short duration)

Bending of collagen and bone

results in e-'s moving within

crystal lattice

No signal = bone atrophy2. StreamUg potential

Movement of ground substance

results in a potential difference

+ve on compression

-ve on tension

Affects cell permeability

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Local control


Blood flow

Microfractures

Sustained pressure

Alters blood flow in PDL

flow in tension

flow in compression

Affects biochemical environment

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Local control


Blood flow

Microfractures MicrofracturesOccur within bond, these accumulate

affecting the microenvironment

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Local control


Blood flow

Microfractures

Prostaglandins

Cytokines

Cyclic amp

OsteoclastsOsteblasts

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Local control (+systemic)


Blood flow

Microfractures

Prostaglandins

Cytokines

Cyclic amp

OsteoclastsOsteblasts

Systemic ControlPTH

vit D

Calcitonin

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Resorption and Deposition

of bone

Tooth movementForce

Tooth

PDL/Bone

Biological electricityBlood flow

Microfractures

Osteoblasts (tension)

Osteoclasts (compression)

Line of Force

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Theories of tooth movement

Pressure- Tension theory

Fluid Dynamic theoryBien Squeeze- Film effect

Oxygen tension

Bone bending theory

Neither incompatible nor mutually exclusive

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Pressure-tension

Sandstedt (1904), Oppenheim (1911),and Schwarz (1932).

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What happens depends on: Level of force

Duration of force

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What happens depends on: Level of force

Duration of force

Heavy force/short duration1-50Kg / less than 1 sec

Force absorbed by bone bending = Pain(Pietzoelectric effect)

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What happens depends on:

Level of force

Duration of force

Heavy force/short duration1-50Kg / less than 1 sec

Force absorbed by bone bending - Pain

(Pietzoelectric effect)

Heavy force/long duration

1-50Kg / continuous

1-2 secs -PDL fluid displaced2-3 secs - PDL tissues compressedpain

Hours-days - cellular necrosis within bone

- hyalanised (acellular layer)

Removed by osteoclasts, tooth movement in

steps - Undermining Resorption

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Level of force

Duration of force

Light force/short durationless than 1 Kg / less than 1 sec

Force absorbed by PDL - no effect

(PDL is actively stable - 5-10g)

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Level of force

Duration of force

Light force/short durationless than 1 Kg / less than 1 sec

Force absorbed by PDL - no effect

(PDL is actively stable - 5-10g)

Light force/long durationless than 1Kg / continuous

Progressive tooth movement occurs

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Level of force

Duration of force

Orthodontic forcesExcessive = pain + undermining resorption

Ideal = socket remodeling

In reality - some undermining resorption occurs

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Simplest orthodontic movementOccurs about centre of resistance

(1/3 from root apex)

Forces are high at apex and alveolar crest,reduce to zero at centre of resistance

Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

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Simplest orthodontic movementOccurs about centre of resistance

(1/3 from root apex)

Forces are high at apex and alveolar crest,reduce to zero at centre of resistance

Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Force - 50-75g

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Force distribution & Type of tooth

movement

Optimal force-The amount of force& the area ofdistribution

The force distribution varies with the type of tooth

movement Tipping -

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Bodily movementAll of PDL is uniformly loaded

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Bodily movementAll of PDL is uniformly loaded

Force : 100-150g

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Force distribution & Type of tooth movement

Bodily tooth movement-uniform loading of the teeth is

seen.

To produce the same pressure-same biologic response-force required is twice

Intermediate forces- part tipping/translating

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Rotary movement

Theoretically need high force

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Rotary movement

Theoretically need high force

BUT

Tipping occurs =

excessive compression of PDL

Force - 50-100g

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Vertical movement

Need to produced

tension in fibres of

PDL

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Vertical movement

Need to produced

tension in fibres of

PDL

Force - 50g

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion Vertical movementForces concentrated at root apex

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Orthodontic force

Tipping

Translation

Rotation

Extrusion

Intrusion

Force - 50g

Vertical movement

Forces concentrated at root apex

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Force distribution & Type of tooth movement

Intrusion-very light forces-concentrated in a small area

Stretch- principal fibres

Extrusion-Only areas of tension

Light forces- could loosen teeth considerably

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Optimum forces for various tooth

movements-Proffit

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Orthodontic force duration

Ideal

Intermittent

Interrupted

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Ideal

Intermittent

Interrupted

Light continuous forceAchievable with fixed appliances

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Ideal

Intermittent

Interrupted

Force decays between adjustmentse.g. Removable appliance springs

Initially force is too high, decays to ideal,then to zero

Results in undermining resorption, which

repairs between visits

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Ideal

Intermittent

Interrupted Force only present when appliance worne.g. HeadgearHeavy force used, needs at least

12hours/day for tooth movement to occur.

Optimal 14-16 hours/day

250g/side for anchorage

450g/side for distal movement

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Pulp

Root

PDL Bone

Orthodontic adverse affects

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Pulp

Root

PDL Bone


Minimal effect

transient inflammatory response

can cause loss of vitality:

compromised teeth

excessive force

inappropriate movement

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Pulp

Root

PDL Bone


Some resorption of root occurs

usually repaired by cementum

Repairs occur during rest periods

BUT permanent damage occurs to root apex

commonly lose 1-2 mm root length

At risk: distorted apices

thin rootscompromised teeth

excess force

history of previous idiopathic resorption

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Pulp

Root

PDL Bone


Minimal transient damageUnless:

excess force maintained

existing periodontal disease

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Pulp

Root

PDL Bone


Minimal transient damage

BUT: loose 1/2 -1 mm of alveolar crest

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Bodily movement

When to use what appliance....

Tipping

Rotation

ExtrusionIntrusion

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Bodily movement


Tipping

Rotation

ExtrusionIntrusion

Removable

Springs / Screws

(Individual or groups of teeth)

Accidental!!

FABP

(Groups of teeth)

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Bodily movement


Tipping

Rotation

ExtrusionIntrusion

Fixed

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Adv: All tooth movements possible

Disadv: Patient co-operation

Oral hygiene

Anchorage

Require skilled operator

Cost ?

Adv / Disadv

Adv: Cheap

Oral hygiene

Anchorage

Simple to use? Patient co-operation ?

Better tolerated ?

Disadv: Limited tooth movements (tipping)

NOT simple to use

Removable: Fixed:

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Physiology of tooth movement

Biomechanics of achieving tooth movement

Review of available appliances

Summary

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