Test #2

Question 1

Flush Plane

Answer 1

• pretty much an end to end class II relationship of the primary molars
• considered to be “normal”
• after eruption of permanent teeth, the leeway space allows mandibular teeth to come forward into class I relationship

Question 2

mesial step

Answer 2

• mandibular molar is mesial to the flush plane

- If it is greater than 1 mm, they have an increased chance of developing a class III relationship

Question 3

distal step

Answer 3

• mandibular molar is distal to the flush plane

- if the patient has this, they have a 100% chance of developing a class II relationship

Question 4

Tooth’s center of resistance

Answer 4

about halfway up the root, but depends on periodontal support

Question 5

vertical distance from the bracket to the center of resistance (CR) is…

Answer 5

about 10 mm

Question 6

“moment”

Answer 6

tendency to rotate

Question 7

the center of resistance moves how during a force?

Answer 7

the CR only moves in the direction of the force, (usually not up or down)

Question 8

what is the formula for the magnitude of a moment?

Answer 8

M=Fd,
unit is g-mm
-F=magnitude of the force and d is the perpendicular distance of the Force from CR

Question 9

A COUPLE always causes..

Answer 9

pure rotation around the center of resistance, regardless of its location on the tooth
-and it produces a pure moment

Question 10

1st order view

Answer 10

viewed in the occlusal plane
-in-out bends
causing buccal-lingual movement and
rotation called “rotation”

Question 11

2nd order

Answer 11

-viewed from the facial or lingual
-up-down bends
causing vertical movement and
rotation called “tipping”

Question 12

3rd order

Answer 12

Viewed from the mesial or distal

-torquing bends causing buccal-lingual rotation called “torque”

Question 13

What is the Moment/Force ration to get pure translation?

Answer 13

10/1

Question 14

what is a couple?

Answer 14

• two equal and opposite non-colinear forces
• when 2 equal forces are applied in opposite directions, they both contribute a tendency to rotate but the forces to move the tooth are cancelled out

Question 15

if the moment to force ratio is 0 what occurs?

Answer 15

tipping (rotation from a buccal or lingual view), but the center of rotation will be above the center of resistance

Question 16

what is the M/F ratio that puts the center of rotation at the apex of the root?

Answer 16

7/1

Question 17

during pure translation, where is the center of rotation?

Answer 17

at “infinity” because there is no center of rotation

Question 18

if the M/F ratio is 13/1, what occurs?

Answer 18

the root will move in the direction of the root, while the crown stays.
-the center of rotation is at the crown

Question 19

what is the M/F for pure rotation?

Answer 19

M/F=undef, the center of rotation is at the center of resistance

Question 20

what type of device/appliance is used for simple attachment?

Answer 20

a button or hook,

-a bracket can also be used for simple forces, but can also do more complicated stuff

Question 21

if a wire has a higher slope what properties does it have?

Answer 21

higher slope (E=modulus of elasticity)=increased stiffness

Question 22

lower slope (modulus of elasticity)=

Answer 22

increased springiness

Question 23

what is the “strength” of a wire?

Answer 23

strength=the max FORCE that a wire can deliver before deforming or breaking

Question 24

what is the “range” of a wire?

Answer 24

range=the maximum deflection a wire can undergo before deforming (or breaking)

Question 25

what were the three materials discussed that are used for wires?

Answer 25

• stainless steel
• beta-titanium
• nickel titanium

Question 26

rank the wire materials in order of stiffness, from most stiff to least

Answer 26

• stainless steel
• beta-titanium
• nickel titanium

Question 27

how does changing the diameter of the wire affect the stiffness?

Answer 27

• increasing the diameter affects stiffness by the change in diameter to the 4th power
• thus doubling the diameter makes it 16 times stiffer

Question 28

how does changing the length of a wire affect its properties?

Answer 28

• increasing the length of the wire affects the springiness to the third power
• doubling the length of a wire makes it 8 times springier

Question 29

E is proportional to …. (formula)

Answer 29

d^4/l^3

Question 30

what is anchorage?

Answer 30

resistance to unwanted tooth movement

Question 31

increasing anchorage…

Answer 31

involves increasing the resistance to unwanted tooth movement

Question 32

reciprocal anchorage (reciprocal tooth movement)

Answer 32

-two (equal) teeth or sets of teeth move equally in the desired directions

Question 33

the anchorage value of a tooth is roughly equal to what?

Answer 33

root surface area

Question 34

“stationary” anchorage

Answer 34

making one side undergo a hard tooth movement while the other has easy movement

• translation vs crown movement
• crown movement vs root movement

Question 35

what are some of the ways/devices that you can increase anchorage?

Answer 35

• headgear
• Nance (palatal) appliance
• interarch elastics
• ortho TADs

Question 36

class II elastics

Answer 36

the posterior portion of the elastic is on mandibular teeth

Question 37

class III elastics

Answer 37

the posterior portion of the elastic is on the maxillary teeth

Question 38

what is an ortho TAD(s)

Answer 38

• temporary anchorage device(s)
• DIRECT and INDIRECT
• like the screw into the alveolar bone with the spring and wire attached to it

Question 39

when is the only time that a tooth will undergo pure rotation?

Answer 39

when M/F=undef,

-I think it’s when there is only a moment