ABO Orthodontic Appliances and Mechanics Flashcards

What material property allows nickel-titanium wires to return to their original shape after deformation?

Answer: Superelasticity

Nickel-titanium wires exhibit superelasticity (pseudoelasticity), allowing them to undergo large deformations and return to their original form.

A Class II elastics configuration runs from the upper canine to the lower first molar. What is the primary skeletal effect?

Answer: Mandibular advancement and/or maxillary retrusion

Class II elastics apply a forward force on the lower arch and a backward force on the upper arch, promoting mandibular advancement and/or maxillary retrusion.

Which wire sequence is correct when beginning fixed appliance therapy?

Answer: NiTi → TMA → stainless steel

Treatment typically begins with flexible NiTi for initial leveling, progresses to TMA for detailing, and finishes with stainless steel for torque and finishing.

What is the purpose of placing a step bend mesial to an upper molar tube?

Answer: To prevent the molar from tipping mesially (anti-tip bend)

A step bend mesial to the molar tube creates an anti-tip effect that resists mesial tipping of the molar during space closure.

Self-ligating brackets differ from conventional brackets primarily because they:

Answer: Use a sliding mechanism instead of ligatures to engage the archwire

Self-ligating brackets use a built-in clip or door to engage the archwire, eliminating the need for elastic or wire ligatures.

Which type of force system is produced by a T-loop spring during space closure?

Answer: Force and moment system

A T-loop spring produces both a force (to close space) and a moment (to control tipping/torque of teeth) simultaneously.