In italiano, per favore

Educational Tool
Published on 10/12/96

ANTERIOR AND CANINE RETRACTION: BIOMECHANIC CONSIDERATIONS

Lorenzo Franchi and Turi Bassarelli

Test Questions

1. Indicate a disadvantage of canine retraction with sliding mechanichs.

a. Extrusion of posterior teeth
b. Friction between wire and bracket
c. Pain

2. Indicate an advantage of canine retraction with closing loop mechanics.

1. Fast tooth movement.
2. Pain free.
3. Predictable force system.

3. Which one of these can be considered as a principal characteristic to describe a spring for closing loop mechanics?

1. Minimum moment.
2. Load-deflection rate.
3. Spring configuration.

4. The moment to force ratio applied at the bracket controls the center of rotation of tooth movement.

1. Yes.
2. No.

5. Which is the ideal type of tooth movement during canine retraction?

1. Translation.
2. Uprighting.
3. Tipping.

6. Which type of tooth movement does a M/F ratio of 18 mm at the bracket of a canine with average root length and normal alveolar bone height produce?

1. Tipping.
2. Uprighting.
3. Translation.

7. Which is the most important factor that controls the type of tooth movement induced by a retraction spring?

1. The moment applied at the bracket.
2. The force applied at the bracket.
3. The M/F ratio applied at the bracket.

8. Which of these statements is true?

1. A spring with low load-deflection rate generates costant force levels during retraction.
2. A spring with low load-deflection rate is more difficult to activate.
3. A spring with high load-deflection rate allows for better control of force levels during activation.

9. The increase in the height of a vertical loop of a retraction spring lowers the M/F ratio.

1. Yes.
2. No.

10. The eccentric displacement of the vertical loop of a retraction spring to the canine leads to an increase in the M/F ratio at the bracket of the tooth.

1. Yes.
2. No.

11. Which is the most important disadvantage in displacing the vertical loop of a retraction spring from the center of interbracket distance to the canine?

1. Tipping of the canine.
2. Intrusion of the canine.
3. Extrusion of the canine.

12. The placement of helices in a vertical loop of a retraction spring primarily influences the M/F ratio.

1. Yes.
2. No.

13. What is the "pre-activation" of a retraction spring with a vertical loop?

1. The placement of bends (angulations) in the horizontal arms of the loop.
2. The extraoral activation of the spring.
3. The placement of helices at the angles between the horizontal and the vertical arms.

14. A spring with pre-activations theoretically can generate any possible M/F ratio.

1. Yes.
2. No.

15. Indicate which of these statements about "T" loop configuration in a retraction spring is true.

1. The M/F ratio is always higher than the height of the loop.
2. The effect of adding horizontal wire lengths gingivally is much greater on M/F ratio than on load-deflection rate.
3. It raises the M/F ratio while simultaneously reduces the load-deflection rate.

ANSWERS

1. b
2. c
3. b
4. b
5. a
6. b
7. c
8. a
9. b
10. a
11. c
12. b
13. a
14. a
15. c

HOME VJO 3

HOME VJO