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Biomechanical Basis Of Orthodontic Tooth Movement

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INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com

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•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 &Orthopedics www.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

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STRUCTURES INVOLVED IN TOOTH MOVEMENT • PDL • ALVEOLAR BONE • TOOTH

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COMPONENTS OF PDL • CELLULAR ELEMENTS – UNDIFFERENTIATED MESENCHYMAL CELLSFIBROBLASTS AND OSTEOBLASTS • TISSUE FLUID – DERIVED FROM VASCULAR SYSTEM

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ALVEOLAR BONE • CORTICAL PLATE

• CANCELLOUS BONE

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TOOTH • CEMENTUM • FIBRES OF PERIODONTAL LIGAMENT

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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 www.indiandentalacademy.com


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 www.indiandentalacademy.com


• CHARACTERISTIC OF PIEZOELECTRICITY- QUICK DECAY RATE • PRODUCTION OF AN EQUIVALENT SIGNAL OPPOSITE IN DIRECTION WHEN FORCE IS RELEASED

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

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FORCE APPLIED ON THE TOOTH ALTERATION IN BLOOD FLOWE IN PDL FORMATION AND RELEASE OF CHEMICAL MESSENGER

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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 www.indiandentalacademy.com


FORCE MAGNITUDE

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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 www.indiandentalacademy.com


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 www.indiandentalacademy.com


REMODELING OF BONE • FRONTAL OR DIRECT RESORPTION • UNDERMINING OR INDIRECT RESORPTION

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TYPES OF TOOTH MOVEMENT TIPPING

TRANSLATION

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• ROOT UPRIGHTING

• ROTATION

• EXTRUSION

• INTRUSION www.indiandentalacademy.com


Optimum force for orthodontic tooth movement • • • • • •

Type of movement Tipping Bodily movement Root uprighting Rotation Extrusion Intrusion www.indiandentalacademy.com

Force(g/cm2) 35-60 70-120 50-100 35-60 35-60 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

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• 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 www.indiandentalacademy.com


• 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

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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 www.indiandentalacademy.com


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

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www.indiandentalacademy.com Leader in continuing dental education

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Biomech of tooth movemnt/ dental implant courses by Indian dental academy