MECHANICAL CONCEPTS IN ORTHODONTICS

Question 1

load on an object causing it to move in direction of application

Answer 1

FORCE

Question 2

→ Newtowns
→ grams or ounces

Answer 2

FORCE

Question 3

balance point of a free body where all mass of an object is concentrated

Answer 3

CENTER OF GRAVITY OR MASS

Question 4

point on the body where a single force (at this point) results in translation

Answer 4

CENTER OF RESISTANCE

Question 5

pint through which an applied force must pass for an object (tooth) to move linearly without rotation

Answer 5

CENTER OF RESISTANCE

Question 6

1-2 mm apical to the bifurcation along the long axis of the tooth

Answer 6

Multirooted Tooth

Question 7

1⁄3 to 1⁄2 of the length of the root from the crest of the alveolar bone along the long axis of the tooth

Answer 7

Monorooted Tooth

Question 8

point about which the object circles around a certain point

Answer 8

CENTER OF ROTATIO

Question 9

T/f

CENTER OF ROTATION controlled with couple and force

Answer 9

T

Question 10

used to create bodily movement

Answer 10

CENTER OF ROTATION

Question 11

CENTER OF ROTATION location:

Answer 11

o at the center of resistance
o apical to it
o at the root apex
o infinity

Question 12

product of force times the perpendicular distance from point of force application and center of resistance (Cres)

Answer 12

MOMENT

Question 13

longer roots have center of resistance more ____ located

Answer 13

apically

Question 14

unit of MOMENT

Answer 14

: gm-mm

Question 15

force will tend to translate and rotate around the object around Cres

Answer 15

MOMENT

Question 16

tendency for a force to produce rotation or tipping of a tooth

tendency to tilt or rotate

Answer 16

MOMENT

Question 17

ortho tooth movement is not applied on the center of the rotation of the tooth but it is delivered through the crown

Answer 17

MOMENT OF THE FORCE (𝑀𝑓)

Question 18

T/f

MOMENT OF THE FORCE (𝑀𝑓), not pure linear movement but some rotational movement (moment of the force) will be present

Question 19

two equal, opposite, noncollinear but parallel forces separated at a distance

Answer 19

COUPLE

Question 20

two forces equal in magnitude but opposite in direction and parallel to each other

Answer 20

COUPLE

Question 21

T/f

overcome the moment WILL force applied to the crown

Answer 21

T

Question 22

T/f

decrease the magnitude of the moment → apply force closer to the center of resistance

Answer 22

T

Question 23

T/f

in orthodontics:
o impractical to apply the force directly to the root

o similar effect could be achieved by constructing a rigid attachment that projected upward from the crown

Answer 23

T

Question 24

T/f

ROTATION requires a couple

Answer 24

T

Question 25

Movement of tooth around its own center of resistance

Answer 25

Rotation

Question 26

T/f forces passing through the center of resistance do not produce a moment, because the distance to the center of resistance is zero; hence, the tooth does not rotate

Answer 26

T

Question 27

A _____ archwire fitting into a rectangular bracket slot on the tooth is most widely used because the entire force system can be produced with a single wire

Answer 27

rectangular

Question 28

T/f in orthodontics, equivalent force systems produce the same effect if the force system was placed at the center of resistance or at the crown (bracket/tube)

Answer 28

T

Question 29

US wire dimensions: thousandths of an ____ European wire dimensions: in ____

Answer 29

inch millimeters

Question 30

COMMON TOOTH MOVEMENTS Translation Tipping (Uncontrolled) Tipping (Controlled) Torque

Answer 30

10 - 20 gms 35- 60 gms 50 - 100 gms 100- 150 gms

Question 31

• Crown and root apex moves in the same distance and the same horizontal direction • requires the most orthodontics force to achieve

Answer 31

Translation

Question 32

tooth moves in the same amount in the same direction force through the center of resistance or through the whole alveolar bone surface one area of tension and one area of pressure

Answer 32

TRANSLATION (BODILY MOVEMENT)

Question 33

Movement of crown but root apex position is maintained •Crot at root apex

Answer 33

Controlled Tipping

Question 34

Root apex and crown move in opposite directions •Crot below Cres (near each other)

Answer 34

Uncontrolled Tipping

Question 35

• displacement of the tooth from the socket in the direction of eruption • Only areas of tension

Answer 35

Extrusion

Question 36

•movement into the socket along the long axis of the tooth •difficult to accomplish

Answer 36

Intrusion

Question 37

force is applied at the bracket and an even larger couple is applied to prevent tipping of the crown caused by the force

Answer 37

ROOT MOVEMENT (TORQUE)