Biomech of Tooth Movemnt-Ortho / orthodontic courses by Indian dental academy

Biomechanical Basis Of Orthodontic Tooth Movement

www.indiandentalacademy.com


INDIAN DENTAL ACADEMY

Leader in continuing dental educationwww.indiandentalacademy.com

•Introduction•Components of P.D.L•P.D.L & Bone response to orthodontic force•Force Magnitude•Theories of tooth movement•Effects of force magnitude•Force Distribution & Types of tooth movement•Force Duration & Force Decay•Orthodontic & Orthopedic Force•Adverse Effect Of Orthodontic Force•Skeletal Effects Of Orthodontic Force•Biomechanics In Removable ,Fixed &Orthopedicswww.indiandentalacademy.com

INTRODUCTION

• ORTHODONTIC TREATMENT IS BASED ON THE PRINCPLE THAT IF PROLONGED PRESSURE IS APPLIED TO A TOOTH, TOOTH MOVEMENT WILL OCCUR AS THE BONE AROUND THE TOOTH REMODELS


STRUCTURES INVOLVED IN TOOTH MOVEMENT

• PDL • ALVEOLAR BONE • TOOTH


COMPONENTS OF PDL

• CELLULAR ELEMENTS – UNDIFFERENTIATED MESENCHYMAL CELLS- FIBROBLASTS AND OSTEOBLASTS

• TISSUE FLUID – DERIVED FROM VASCULAR SYSTEM


ALVEOLAR BONE

• CORTICAL PLATE

• CANCELLOUS BONE


TOOTH

• CEMENTUM • FIBRES OF PERIODONTAL

LIGAMENT


PDL AND BONE RESPONSE TO SUSTAINED

ORTHODONTIC FORCE • HEAVY FORCE – LEADS TO RAPIDLY

DEVELOPING PAIN, NECROSIS OF CELLULAR ELEMENTS WITHIN THE PDL

• LIGHT FORCE – COMPATIBLE WITH SURVIVAL OF CELLS WITHIN PDL AND A REMODELLING OF TOOTH SOCKET


THEORIES OF TOOTH MOVEMENT

• BIOELECTRIC THEORY – TOOTH MOVEMENT ATLEAST IN PART TO CHANGES IN BONE METABOLISM CONROLLED BY ELECTRIC SIGNAL THAT ARE PRODUCED WHEN ALVEOLAR BONE FLEXES AND BENDS

• PIEZOELECTRICITY IS OBSERVED IN CRYSTALLINE STRUCTURE – PRODUCES A FLOW OF ELECTRIC CURRENT AS ELECTRON ARE DISPLACED FROM ONE PART OF CRYSTAL LATTICE TO ANOTHER


• CHARACTERISTIC OF PIEZOELECTRICITY- QUICK DECAY RATE

• PRODUCTION OF AN EQUIVALENT SIGNAL OPPOSITE IN DIRECTION WHEN FORCE IS RELEASED


PRESSURE TENSION THEORY

• RELIES ON CHEMICAL RATHER THAN ELECTRICAL SIGNAL, AS THE STIMULUS FOR CELLULAR CHANGES


FORCE APPLIED ON THE TOOTH

ALTERATION IN BLOOD FLOWE IN PDL

FORMATION AND RELEASE OF CHEMICAL MESSENGER


FORCE MAGNITUDE

• FORCE IS DEFINED AS AN ACT UPON A BODY THAT CHANGES OR TENDS TO CHANGE THE STATE OF REST OR THE MOTION OF THAT BODY

• FORCE – 3 COMPONENTS MAGNITUDE DIRECTION SENSE


FORCE MAGNITUDE


EFFECTS OF FORCE MAGNITUDE

HEAVY SUSTAINED PRESSURE

GREATER THE REDUCTUION IN BLOOD FLOW THROUGH COMPRESSED AREAS OF BLOOD FLOW

VESSELS ARE TOTATTLY COLAPSED

NO BLOOD FLOW www.indiandentalacademy.com

LIGHT CONTINOUS FORCE APPLIED TO THE TOOTH

BLOOD FLOW TO THE PARTIALLY COMPRESSED PDL

DECREASES THE FLUID FROM PDL SPACE

AFTER FEW HOURS CHANGES IN CHEMICAL ENVIROMENT

CHANGES IN CELLULAR ACTIVITY(INCREASED LEVEL OF CYCLIC AMP – SECOND MESSENGERS )

CELLULAR CHANGES AFTER 4HOURS OF SUSTAINED PRESSURE


RECENT STUDIES

• PROSTAGLANDIN LEVEL INCREASES IN PDL AFTER APPLICATION OF FORCE

• PROSTAGLANDIN IS AN IMPOTANT MEDIATOR FOR CELLULAR RESPONSE

• PROSTOGLANDIN IS RELEASED WHEN CELLS ARE DEFORMED FOR TOOTH MOVEMENT

• PLAY A MAJOR ROLE IN CELLULAR DIFFERENTIATION – OB, OC, FB, FC


REMODELING OF BONE

• FRONTAL OR DIRECT RESORPTION

• UNDERMINING OR INDIRECT RESORPTION


TYPES OF TOOTH MOVEMENT

TIPPING

TRANSLATION


• ROOT UPRIGHTING

• ROTATION

• EXTRUSION

• INTRUSION www.indiandentalacademy.com

Optimum force for orthodontic tooth movement

Type of movement Force(g/cm2)• Tipping 35-60• Bodily movement 70-120• Root uprighting 50-100• Rotation 35-60• Extrusion 35-60• Intrusion 10-20


Definitions• Force: A load applied to an object that will tend to

move it to a different position in space.• Center of resistance: A point at which resistance to movement can

be concentrated for mathematical analysis.• Moment: A force acting at a distance to the center of

resistance. M=F x d


• Couple: Two forces equal in magnitude and

opposite in direction• Center of rotation: The point around which rotation

actually occurs when an object is being moved


• Moment to Force ratio During movement requires both a force

to move a tooth in desired direction, and a couple to produce the necessary counter balancing moment for control of root position


Effects of force duration and force decay• Continuous – Force maintained at some

appreciable fraction of the original from one patient visit to the next.

• Interrupted – Force level decline to zero between activation

• Intermittent – Force level decreases to zero intermittently, when the orthodontic appliance is removed by the patient and returns to the original level sometime later


Adverse effects of the orthodontic force

• Mobility and pain related to orthodontic treatment

• Effects on the pulp• Effects on the root structure• Effects of treatment on the height of

alveolar bone



www.indiandentalacademy.comLeader in continuing dental education

Biomech of Tooth Movemnt-Ortho / orthodontic courses by Indian dental academy

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