ABO ABO Orthodontic Appliances and Mechanics 1 — Questions and Answers
Question 1: Which bracket prescription is characterized by built-in torque, tip, and in-out values to reduce the need for wire bending?
- Begg bracket
- Edgewise bracket
- Preadjusted edgewise bracket (Correct answer)
- Ribbon arch bracket
Correct answer: Preadjusted edgewise bracket
The preadjusted edgewise (straight-wire) bracket incorporates built-in torque, tip, and in-out compensations to minimize wire adjustments.
Question 2: What is the primary purpose of a transpalatal arch (TPA) in orthodontic treatment?
- To advance the mandible
- To maintain molar width and prevent molar rotation (Correct answer)
- To expand the maxillary arch
- To intrude the upper incisors
Correct answer: To maintain molar width and prevent molar rotation
A transpalatal arch connects the upper molars across the palate to maintain their transverse position and prevent unwanted rotation.
Question 3: In the Tip-Edge bracket system, teeth are allowed to tip freely in which phase?
- Finishing phase
- Detailing phase
- Initial leveling phase (Correct answer)
- Retention phase
Correct answer: Initial leveling phase
During the initial leveling phase of Tip-Edge mechanics, teeth tip freely to correct vertical and horizontal discrepancies before torquing.
Question 4: Which type of headgear produces the greatest restriction of maxillary forward growth?
- Cervical-pull headgear
- Straight-pull headgear
- High-pull headgear (Correct answer)
- Reverse-pull (facemask) headgear
Correct answer: High-pull headgear
High-pull headgear directs force superiorly and posteriorly, providing the greatest restriction on forward maxillary growth.
Question 5: What is the function of a Nance holding arch?
- To distalize upper molars
- To prevent mesial drift of upper molars after premolar extraction (Correct answer)
- To correct a posterior crossbite
- To retract the upper anterior teeth
Correct answer: To prevent mesial drift of upper molars after premolar extraction
The Nance holding arch uses a palatal button to resist mesial movement of upper molars, preserving space after premolar extraction.
Question 6: Which auxiliary is most commonly used on an edgewise appliance to produce root torque in the upper incisor region?
- Lingual arch
- Torquing auxiliary
- Utility arch (Correct answer)
- Reverse curve of Spee wire
Correct answer: Utility arch
A utility arch bypasses the premolars and canines to apply intrusion and torque forces directly to the incisors.
ABO ABO Orthodontic Appliances and Mechanics 1
Which bracket prescription is characterized by built-in torque, tip, and in-out values to reduce the need for wire bending?