ABO ABO Orthodontic Appliances and Mechanics 3

Question 1

Which factor most directly determines the center of rotation during tooth movement?

Accepted Answer

Moment-to-force (M/F) ratio

Answer

The moment-to-force ratio applied to a tooth determines where the center of rotation is located relative to the center of resistance.

Question 2

Forsus Fatigue Resistant Device (FRD) is classified as which type of appliance?

Accepted Answer

Fixed functional appliance

Answer

The Forsus FRD is a fixed functional appliance that is attached to the orthodontic brackets and delivers a continuous corrective force.

Question 3

The Herbst appliance corrects Class II malocclusion primarily through which mechanism?

Accepted Answer

Mandibular advancement and restraint of maxillary growth

Answer

The Herbst appliance postures the mandible forward continuously, stimulating mandibular growth and restraining maxillary forward development.

Question 4

What is the recommended frequency of archwire changes when using superelastic NiTi wires?

Accepted Answer

Every 6–8 weeks

Answer

Superelastic NiTi wires deliver sustained forces over longer periods, so they are typically changed every 6–8 weeks.

Question 5

A quad helix appliance is used primarily to achieve which treatment goal?

Accepted Answer

Maxillary transverse expansion and molar derotation

Answer

The quad helix is a fixed maxillary expander that widens the upper arch and derotates the upper molars.

American Board of Orthodontics (ABO) Practice Test