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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
Biologic electricity
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
Biologic electricity
Blood flow
Microfractures MicrofracturesOccur within bond, these accumulate
affecting the microenvironment
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Local control
Biologic electricity
Blood flow
Microfractures
Prostaglandins
Cytokines
Cyclic amp
OsteoclastsOsteblasts
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Local control (+systemic)
Biologic electricity
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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What happens depends on:
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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What happens depends on:
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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What happens depends on:
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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Orthodontic force duration
Ideal
Intermittent
Interrupted
Light continuous forceAchievable with fixed appliances
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Orthodontic force duration
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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Orthodontic force duration
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
Orthodontic adverse affects
Minimal effect
transient inflammatory response
can cause loss of vitality:
compromised teeth
excessive force
inappropriate movement
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Pulp
Root
PDL Bone
Orthodontic adverse affects
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
Orthodontic adverse affects
Minimal transient damageUnless:
excess force maintained
existing periodontal disease
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Pulp
Root
PDL Bone
Orthodontic adverse affects
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
When to use what appliance....
Tipping
Rotation
ExtrusionIntrusion
Removable
Springs / Screws
(Individual or groups of teeth)
Accidental!!
FABP
(Groups of teeth)
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Bodily movement
When to use what appliance....
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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