Orthodontic Biomechanics Flashcards
What are the 3 laws of motion?
- Law of inertia.
- Law of acceleration.
- Law of action and reaction.
What is the 1st law of motion: the law of inertia?
- An object at rest will remain at rest…
- Unless acted on by an unbalanced force
and
- An object in motion will continue with constant speed and direction
- Unless acted on by an unbalanced force
What is the 2nd law of motion: law of acceleration?
- An object acted upon by an unbalanced force will accelerate in the direction of the force
- The ball accelerates only while your foot is in contact with the ball
What is the third law of motion: law of action and reaction?
For every action there is an equal and opposite reaction
What are mechanics?
The science that deals with the action of forces on the form and motion of bodies
What are the characteristics of a force?
- magnitude
- direction
- sense
What is the center of resistance?
- Also known as center of gravity
- Point in which an object or body is in equilibrium
What is the movement of a free body?
Relationship of the line of action of the force with the center of resistance
What is a constrained body?
- A tooth is a constrained body.
- The center of resistance will vary with alveolar height
What is moment?
Measure of the tendency of a body to rotate around a point or axis perpendicular to any given plane
What are examples of simple forces?
- Pull (tension)
- Push (pressure)
- Extrude
- Intrude
What are the different force systems in ortho?
- Point of application of the force: almost always at the crown level
- Direction of the force (3 planes of space)
- Amplitude of the force (varies)
Point of application of the force: almost always at the _______ level
crown
In orthodontics, a simple force applied to the crown of a tooth will result in ________ of the crown
tipping
The crown will tip in the direction of the force, the apex will tip…
in the opposite direction
What is done when a tooth needs movement more than a simple force?
- Translation
- Rotation
What is a couple?
Two forces equal in magnitude and opposite in direction act on an object
What is the result of a couple?
- pure moment, since translatory effect of the forces cancel
- The object will spin around its center of resistance (rotation)
Couples result in…
all rotation
no translation
What is translation?
bodily movement
a combination of a simple force and a moment of force to obtain translation
In orthodontics, _________ is often the movement of choice
translation
