10th Class

Question 1

_______ is the research and analysis of the mechanical properties of living tissues and non-living objects that affect those living tissues.

Answer 1

Biomechanics

Question 2

The analysis of the non-living component simply follows _______ mechanical principles.

Answer 2

Newtonian

Question 3

, the biomechanical properties of living or non-living tissue are more complicated and often not thoroughly understood?

Answer 3

Living tissue more complicated

Question 4

Newton’s three “Laws of Motion” describe the relationship between
the _______ acting on an object and the _____ of that object,
which form the basis for classical mechanics.

Answer 4

external forces; motion

Question 5

Mechanics is the branch of physics concerned with the behavior of
objects when subjected to _____ or _______

Answer 5

forces; displacements

Question 6

What is Newton’s first law?

Answer 6

A body at rest remains at rest, and a body in motion continues to move in a straight line with a constant speed unless and until an external unbalanced force acts upon it.

Question 7

What is Newton’s second law?

Answer 7

The rate of change of momentum of a body is directly proportional to the impressed force and takes place in the direction in which the force acts.

Question 8

What is Newton’s third law?

Answer 8

Whenever A exerts a force on B, B simultaneously exerts a force of the same magnitude and in the opposite direction on A.
“For every action, there is an equal and opposite reaction”

Question 9

_____ is an influence that may cause an object to change its velocity (accelerate).

Answer 9

force

Question 10

It may be experienced as a lift, a push, or a pull, and it has a magnitude and a direction and hence is mathematically represented by a _____

Answer 10

vector

Question 11

The actual acceleration of the body is determined by the _______ of all forces acting on it.

Answer 11

vector sum

Question 12

A vector is a concept characterized by a ______ and a _______.

Answer 12

magnitude; direction

Question 13

_____ is a vector quantity defined as the rate of change of the momentum of
the body that would be induced by that force acting alone.

Answer 13

Force

Question 14

A ____ has only a magnitude.

Answer 14

scalar

Question 15

A scalar has only _____

Answer 15

Magnitude

Question 16

Orthodontic forces are described by their what 3 things?

Answer 16

magnitude, point

of application, and direction.

Question 17

The ______ of the force is defined by the line of action and the sense (arrowhead).

Answer 17

direction

Question 18

The ______ of the force is depicted by the length of the line using an arbitrary scale

Answer 18

magnitude

Question 19

Using the ______ as the horizontal reference of

an orthogonal coordinate system.

Answer 19

occlusal plane

Question 20

The calculations of magnitude and direction of the
components can be carried out geometrically by using
_____ methods

Answer 20

trigonometric

Question 21

The ______ describes all the forces involved and allows for
analysis and calculation of resultant forces on a tooth or a group of
teeth.

Answer 21

force system

Question 22

______ forces depicted as vectors can be added
together to calculate the resultant by using the
parallelogram method or by addition of their
components in a reference system.

Answer 22

Concurrent

Question 23

The ______ method used to derive resultant forces
entails drawing the two concurrent forces (F1 and F2) to
scale at appropriate angulations.

Answer 23

parallelogram

Question 24

The diagonal of this parallelogram from the point of force
application, when measured and converted using the
specified scale, gives the _______ of the resultant (R).

Answer 24

magnitude

Question 25

Forces have what 4 things?

Answer 25

* Line of action. * Direction. * Magnitude. * Point of application.

Question 26

Force application in orthodontics is analyzed in relation to the ________ of a tooth or group of teeth.

Answer 26

Centre of Resistance | C of Res.

Question 27

______ is the point on the tooth where if a force is | applied will result in bodily movement or translation.

Answer 27

C of Res

Question 28

C of Res is located on the ______ of the tooth approx. | 30% from the alveolar crest.

Answer 28

long axis

Question 29

C of Res is located on the long axis of the tooth approx. | ___ % from the alveolar crest.

Answer 29

30%

Question 30

The center of resistance is a constant point for any given tooth and depends on what 4 things?

Answer 30

* The root length * Thickness * Bone * Periodontal ligament

Question 31

•The point around which the tooth rotates

Answer 31

Center of Rotation

Question 32

The location of the center of rotation is dependent on the_______ applied to the tooth

Answer 32

force | system

Question 33

This force system to determine center of rotation is considered as the _________

Answer 33

Moment to Force | ratio (M/F)

Question 34

_____ is the tendency for a force to produce rotation or tipping of a tooth. -determined by multiplying the magnitude of the force (F) by the perpendicular distance (d) from the center of resistance to the line of action of this force.

Answer 34

Moment

Question 35

_____ is a system having two parallel forces of equal magnitude acting in opposite directions

Answer 35

Couple

Question 36

Every point of a body to which a couple is applied is under a rotational effect in the ____ direction and magnitude.

Answer 36

same

Question 37

T/F: A couple can never move the center of resistance, and with a couple the center of rotation and the center of resistance will always be coincident.

Answer 37

True

Question 38

A couple causes an object to ________ | regardless of the point of application.

Answer 38

rotate around its center of resistance

Question 39

Two forces ____ in magnitude and _____ in direction.

Answer 39

equal; opposite

Question 40

Perhaps the simplest way to determine how a tooth will move is to consider: •The ratio between the moment created when a force is applied to the crown of a tooth. (moment of the force MF) •The counter-balancing moment generated by a couple within the bracket. (moment of the couple MC)

Answer 40

MC/MF ratio

Question 41

MC/MF = 0 | What happens?

Answer 41

•Uncontrolled tipping (tooth rotates around center of resistance)

Question 42

0 < MC/MF < 1 | What happens?

Answer 42

•Controlled tipping (inclination of tooth changes but the center of rotation is displaced away from the center of resistance, and the root and crown move in the same direction).

Question 43

MC/MF = 1 | What happens?

Answer 43

•Bodily movement(equal movement of crown and root).

Question 44

MC/MF > 1 | What happens?

Answer 44

•Torque (root apex moves further than crown)

Question 45

•The simplest form of orthodontic movement is tipping. •Tipping movements are produced when a single force is applied against the crown of a tooth. •When this is done, the tooth rotates around its “center of resistance”. •Force applied at the bracket causes crown to move one way, and the root the other. •Centre of Rotation (C of Rot) point around which the tooth is located at C of Res.

Answer 45

Uncontrolled tipping

Question 46

To control the M of the F, we must introduce another MOMENT produced by a ______ which acts in opposition to the M of the F.

Answer 46

COUPLE

Question 47

Further increasing the Moment of the Couple completely counters the M of the F and moves the C of Rot to infinity => _____

Answer 47

Translation

Question 48

Increasing the M of the Couple to exceed the M of the F moves the C of Rot to the incisal edge => ________

Answer 48

palatal crown torque.

Question 49

Involves moving the C of Rot away from the C of Res. •Accomplished by applying a Moment of a Couple to counter the Moment of the Force.

Answer 49

Controlled tipping

Question 50

If the force passes through the center of resistance of the tooth, the tooth will move ________ •The center of rotation goes to the infinity. •In this movement the moment caused by the arch wire is compensating for the moment of the force.

Answer 50

bodily or translate.