biomechanics of tooth movement - dr karandishdrkarandish.ir/studenthandouts/biomechanics of...
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BIOMECHANICS OF TOOTH MOVEMENT
Dr Karandish DDS, MS
Fellowship of Lasers in dentistryFellowship of Medical educationFellowship of researchFellowship of electronic learning
In the Name of Allah
The Compassionate
The Merciful
CONTENTS Introduction to
biomechanics Phases of tooth
movement Theories of tooth
movement Biologic control of tooth
movement Effects of force
magnitude
Effects of force distribution & types of tooth movement
Effects of force distribution & force decay
Anchorage control
References
Ch. 18 کتاب ملی
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Force
The force must have the right characteristics such as the magnitude and duration ---- it must meet certain threshold.
Force
contact noncontact
Force
point distributed
force
external internal
Force Types
Light, continuous forces Never declines to zero
Interrupted forces Declines to zero
Intermittent forces Declines to zero
Couple Force
Addition
Biomechanics of Tooth Movement
Center of Resistance --- A point on the tooth around which the tooth shall move. For most teeth, COR is ½ way between the apex and the crest of the alveolar bone.
Center of mass vs center of resistance
Center of Rotation --- The point around which rotation occurs when an object is being moved.
Force and Couple Force
Is applied by orthodontic appliances. Induces tipping, translation, intrusion, extrusion and/or
rotation. Couple
Two forces of opposite directions and with non-overlapping points of application.
Translation of teeth occurs in response to appropriate force couples.
Force Magnitude (Level)
In the range of 10 to 200 grams. Varies with the type of tooth movement. Light, continuous forces are currently considered to be
most effective in inducing tooth movement. Heavy forces cause damages and fail to move the teeth.
Force Duration
Threshold --- 6 hrs per day. No tooth movement if forces are applied less than 6 hrs/d. From 6 to 24 hrs/d, the longer the force is applied, the
more the teeth will move.
Eruption Active Passive
Lateral drifts Physiological Due to loss of adjacent teeth
Orthodontic tooth movement
Types of Tooth Movement
Types of Tooth Movement
Intrusion Extrusion Tipping Translation Rotation
Any questions???
For the slide presentation you can visit:
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Now let’s trace and discuss biomechanics of different tooth movements
Anchorage
Newton’s law: for every action, there is reaction.
Defined as “resistance to unwanted tooth movement.”
The “anchorage value” of any tooth is roughly equivalent to its root surface area. Thus, molars and canines generally have higher anchorage values than incisors and bicuspids.
Anchorage types
Reciprocal anchorage Reinforced anchorage Stationary anchorage Cortical anchorage
Face bow
Both units move roughly equal distance.
Exemplified by closing a diastema between two central incisors.
Face Bow
Reinforced anchorage•Unit A has substantially more anchorage value than Unit
B. Thus, Unit A moves little but Unit B moves a lot.•Exemplified by retracting anterior teeth to close an
extraction space by using posterior teeth as a reinforced anchorage unit.
Unit BUnit A
Bone anchorage
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Thanks for Your Attention
Any Questions?