force system and tissue response to forces in

8/6/2019 Force System and Tissue Response to Forces In

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FORCE SYSTEM AND TISSUE RESPONSE

TO FORCES IN ORTHODONTICS AND

DENTOFACIAL ORTHOPEDICS

Dr. Vergel John P. Ercia


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MALOCCLUSIONARE TREATED

IRRESPECTIVE OF THE APPLIANCE

EMPLOYED BY THE PURPOSEFULALTERATION OF THE FORCES

WITHIN THE CRANIOFACIAL

REGION


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INHERENT NATURAL FORCES

Originating from action ofthe muscles ofmastication ANTERIOR COMPONENT OF

FORCE - resultant forcetransmitted through theintercuspation of teethduring occlusal function

SWALLOWING

Originating within theteeth ERUPTION

MESIAL DRIFTINGTENDENCY


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Originating from the CIRCUMORALMUSCULATURE

TONGUE

LIPS

CHEEKS

Equilibrium theory variety of forces act on the

teeth from many directions in varying amountsand duration, tooth positions remain relativelystable


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Equilibrium theory varietyof forces act on the teethfrom many directions invarying amounts and

duration, tooth positionsremain relatively stable

2 most impt factors in theequilibrium of teeth

a. Resting pressure of the

lip, cheeks and tongueb. Forces produced by

metabolic activity in theperiodontium


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SUMMARY OF FORCES

COMPONENT INTENSITY DURATION

Forces of occlusion Very High Very Short

Lip and/or Tongue Pressure

Swallow High Short

Speech Low Short

Rest Low Long

Forces of Eruption Very Low Long


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ABNORMAL FORCES

Tongue Thrusting

Digital Sucking

Occlusal dysfunction

Traumatic occlusion

bruxism


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THERAPEUTICALLY INTRODUCED

FORCES

To alter tooth position

Permit changes in the mandibular position

To affect craniofacial morphology or growth


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THERAPEUTICALLY INTRODUCED

FORCES

Orofacial forces maybe altered by

Neuromuscular conditioning

Functional appliances which modify and redirect

the patients own neuromuscular conditioning

Fixed orthodontic appliances which have stored

within them intentional forces controlled by the

clinicians


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CLASSIFICATION OF THERAPEUTICALLY

EMPLOYED FORCES

Natural

energy generated by thecontraction of jaw andfacial muscles maybe

transferred throughfunctional appliances todirect the eruption of teeth,impede eruption or movean erupted teeth

Functional appliances arealso used to condition,

strengthen or redistributemuscle forces against the

jaws and dentition


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CLASSIFICATION OF THERAPEUTICALLY

EMPLOYED FORCES

Biomechanical

Are artificial clinically

induced forces whose

energy is derivedprimarily from contrived

mechanical devices


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STRATEGIES FOR CONTROLLING FORCES

IN CLINICAL PRACTICE

Elimination of unwantedforces HABIT CONTROLAPPLIANCE

Redistribution of natural

forces FUNCTIONALAPPLIANCE

Stimulation or strengtheningof natural forces- eg. Lipbumper, vestibular shieldand labial pads ofFRANKELAPPLIANCE

Introduction of artificialforces


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ANCHORAGE

Word used in orthodontics to mean resistance

to displacement

2 elements of an orthodontic appliance Active elements concerned with tooth movement

Resistance elements provides the resistance

(ANCHORAGE) that makes tooth movements

possible


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THERE IS AN EQUAL AND

OPPOSITE REACTION TO EVERYACTION

NEWTONS THIRD LAW


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ALL ANCHORAGE IS RELATIVE AND

ALL RESISTANCE IS COMPARATIVE


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CLASSIFICATION OF ANCHORAGE

According to manner of force

application

Simple anchorage

resistance to tipping

Stationary anchorage resistance to bodily

movement

Reciprocal anchorage two

or more teeth moving in

opposite directions andpitted against each other by

the appliance usually equal

and opposite


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According to the jaws

involved

Intra maxillary anchorage

established in the same jaws

Intermaxillary anchorage

distributed to both jaws


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According to the site ofanchorage Intraoral anchorage is

established within the

mouth that is utilizing theteeth, mucosa or otherintraoral structures

Extra oral- anchorageestablished outside theoral cavity

Cervical Occipital

Cranial

facial

Muscular


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According to the number of

anchorage

Simple or primary anchorage

Compound anchorage

Reinforced anchorage


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CONTROL OF ANCHORAGE

Securing anchorage as far as possible outside

the teeth themselves

Selecting larger numbers of teeth in theresistance parts of the appliance

Varying the amount ,direction and manner of

force application between active and resistance

elements


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ORTHODONTIC APPLIANCEIS A

SYSTEM STORING AND DELIVERINGFORCES AGAINST THE TEETH,

MUSCLES OR BONE CREATING

REACTION WITHIN THEPERIODONTAL LIGAMENT AND

ALVEOLAR BONE THAT CAUSES

MOVEMENTS OF THE TEETH ORALTER BONE MORPHOLOGY OR

GROWTH


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INTRODUCTION

Mechanics-is the discipline that describes the

effect of forces on bodies.

Biomechanics-study of mechanics as it affects

the biologic systems.

Application of mechanics to the biology of tooth

movement.


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INTRODUCTION

Orthodontic tooth movement Force on the teeth.

Knowledge of mechanical principles and governing

forces- necessary for the control of orthodontic

treatment. Basis of orthodontic treatment-clinical application of

biomechanic concepts

Proper mechanical force system = medications

Treatment success.


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TYPES OF TOOTH MOVEMENTS

Tipping crown and root are moved in oppositedirections around a center of rotation within a root

Translation (bodily) the crown and the root are going inthe same direction at the same time

Rotation circular motion around the long axis of thetooth as when the buccal cusp is going distally andlingual cusp mesially

Intrusion movement of tooth into the alveolus

Extrusion movement of the tooth out of the alveolus Torque movement of the tooth without movement of

the crown


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TERMS AND DEFINITIONS

Centre of Mass- All objects (finite) behave as if theentire mass is concentrated onto a single point.

Applicable in force - free state

Behaviour- Predictable if forces acting in relation to

this point is known.


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Centre of Gravity- objects subject to

gravitational force

Cmass / Cg - Balance point


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Centre of Resistance- analogous to the Cmass

for restrained bodies. Function of a body in a system of constraints-supporting tissues.


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Cres depends on-1. Root length & Morphology

2. Number of roots

3. Level of alveolar bone support


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Various authors differ in the estimation of Cres.

Methodology.

For single rooted teeth-

At 50% of root length-Proffit,Nikolai

B/w 50%-33% of root length-Smith and Burstone

At 33% of root length-Burstone

B/w 25%-33% of root length-Nanda

The Cres of facial bones, entire arches of

teeth, or segments can also be estimated


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Multirooted teeth-

Maxillary anterior dentiton

Cres - maxillary anterior teeth-distal to lateral

incisor-NandaIncorporation of lateral incisors-small distal

shift,canines- significant distal movement -

Burstone & Sachdeva

Mutirooted-close to bifurcation of the roots Nanda

Trifurcation-Upper I molar- Worms, Isaacson andSpeidel


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Cres of -maxilla-slightly inferior to orbitale-

Nanda

Postero-superior ridge of the pterygomaxillary

fissure registered on the median sagittalplane-Tanne et al


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Determination of the centers of resistance of all theindividual teeth and groups of teeth

Conclusions-

1. Longer the root, the more apically placed was theCres.

2. The Cres of all teeth were slightly apical to thecentroid of the teeth.

3. The Cres of Mand. Premolars lie at the same level,Cres of I Max. Premolar is more apical to that ofthe II premolar.


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4. The Cres of the maxillary and Mandibular molar

lies at the tri/bifurcation respectively.

5. Intrusive forces on groups of teeth-Cres shifts

posteriorly as more number of teeth were includedin the segment.

6. For retractive forces on groups of teeth-Cres shifts

coronally as more number of teeth were included

in the segment.


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Precise location-not known, conceptual awareness

needed.

Relationship of force systems to Cres of tooth-typeof tooth movement


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Centre of Rotation- a

point around which an

object rotates.

-The geometric point

about which no

movement occurs

Point around which an object seems to have rotatedas determined from its initial and final positions.


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Method for determining centre of rotation


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Can be at any point

ON or OFF the tooth

If there has been no

rotation-infinity

If tooth has followedan irregular path-

several centers of

rotation


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CENTER OF RESISTANCE IS A TERM

USED IN ORTHODONTIC BIOMECHANICS

IN PLACE OF A CENTER OF MASS ORCENTER OF GRAVITY

Single rooted teeth long axis of the tooth

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to the way from the alveolar crest tothe apex

Multirooted teeth apical to the furcation


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CENTER OF ROTATION THE POINT AT

WHICH A BODY SEEMS TO HAVE ROTATED

The center of resistance of a tooth is fixed

and not changed by orthodontic forces butthe manner of force application can be

chose to determine the instantaneous center

of rotation


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RESPONSE OF DENTAL TISSUES TO

ORTHODONTIC FORCES

Tooth sufficient duration and intensity, path ahead is

not blocked by the occlusion or another tooth

Dental pulp

Mild force hyperaemia

Severe force partial or total pulpal degeneration

Cementum resorption usually occurs in the apical

portion of root

Enamel no change Gingiva inflammation with mild edema of the marginal

gingiva


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ORTHODONTIC FORCES

Alveolar bone Bone resorption on the area of pressure

(OSTEOCLASTIC ACTIVITY)

Bone deposition on the area of tension (OSTEOBLASTIC

ACTIVITY) Periodontal membrane

TENSION SIDE stretching of the periodontal fibersstimulates osteoblastic activity on the surface of

alveolar wall PRESSURE SIDE the principal fibers attached to the

alveolar wall are disconnected as resorption takesplace


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ORTHODONTIC FORCES


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ORTHODONTIC FORCES


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FACTORS IN TOOTH MOVEMENT

Manner of force application the amount,

duration and direction of force maybe

combined in various manners according to the

intent of the orthodontist and the appliance

Continous force

Dissipating force

Intermittent force/interrupted

Functional forces


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FACTORS IN TOOTH MOVEMENT

Amount of force application varies with the type of tooth movement

Duration of force application

The periodontal ligament must have recovery period to replenish the bloodsupply to the ligament and to promote cell proliferation

Heavy force of short duration matbe less damaging than light continous force

Direction of force application Occlusal function

Orthodontic movements are countered by the intertcuspation during occlusalfunction resulting in jiggling and often hypermobiliuty

Age

The biologic response to orthodontic forces in adult is slower than in a child

The removal of occlusal forces is important in adult tooth movement and there isa need for light forces with longer period of rest between adjustments


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TISSUE RESPONSE TO ORTHODONTIC

MOVEMENT

Initial response

Compression of periodontal vessels

area of the compressed periodontal ligament becomes

cell free Secondary response

Widened periodontal space

Resorption of bone

Proliferation of osteoblasts presages the appearance ofosteoid tissue on the tension side then followed by newbundle bone


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MOVEMENT

Root resorption

Are more likely to be seen when heavy forces are activefor too long period on a small rooted teeth

Translation, torque and intrusion are movements thatare most likely to cause root resorption

Micro resorption local, superficial,confined to thecementum and routinely repaired

Progressive resorption involves decreasing amountsof the apical end of the root

Idiopathic resorption resorption not related to theorthodontic forces


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MOVEMENT

OPTIMAL FORCE


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MOVEMENT

OPTIMAL FORCE Pressure areas Cellular proliferation within a few days

Osteoclasts migrate into the PDL from blood vessel

Resorption of bone and remodelling of PDL fibers

Tension areas Stretching of PDL fibers

Cellular proliferation of fibroblasts and osteoblasts

Increase in length of PDL fibers

Deposition of osteoid

Remodelling and reattachment of PDL fibers andcalcification of osteoid into mature bone


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MOVEMENT

HEAVY FORCE


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MOVEMENT

HEAVY FORCE Pressure areas Capillary blood vessels are crushed resulting in death of cells in PDL

(hyalinization)

In areas adjacent to the hyalinized sections of PDL cellular proliferationoccurs

Resorption occurs deep to hyalinized area from cancellous boneoutwards toward lamina dura of PDL (undermining resorption)

Tooth movement occurs

Tension areas

Stretching of PDL fibers

Cellular proliferation of fibroblasts and osteoblasts

Increase in length of PDL fibers Deposition of osteoid

Remodelling and reattachment of PDL fibers and calcification of osteoidinto mature bone


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CONTROLLED ALTERATION OF

CRANIOFACIAL GROWTH


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force system and tissue response to forces in

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