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.

a Fast tooth movement.

b Pain free.

c Predictable force system.

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

a Minimum moment.

b Load-deflection rate.

c Spring configuration.

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

a Yes.

b No.

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

a Translation.

b Uprighting.

c 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?

a Tipping.

b Uprighting.

c Translation.

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

a The moment applied at the bracket.

b The force applied at the bracket.

c The M/F ratio applied at the bracket.

8. Which of these statements is true?

a A spring with low load-deflection rate generates costant force levels during retraction.

b A spring with low load-deflection rate is more difficult to activate.

c 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.

a Yes.

b 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.

a Yes.

b 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?

a Tipping of the canine.

b Intrusion of the canine.

c Extrusion of the canine.

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

a Yes.

b No.

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

a The placement of bends (angulations) in the horizontal arms of the loop.

b The extraoral activation of the spring.

c 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.

a Yes.

b No.

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

a The M/F ratio is always higher than the height of the loop.

b The effect of adding horizontal wire lengths gingivally is much greater on M/F ratio than on load-deflection rate.

c It raises the M/F ratio while simultaneously reduces the load-deflection rate.