ABO Cephalometric Analysis and Radiographic Interpretation 2

Question 1

In Steiner cephalometric analysis, what is the normal value for the SNB angle?

Accepted Answer

80°

Answer

The normal SNB angle is 80° (±2°), representing the anteroposterior position of the mandible relative to the cranial base.

Question 2

The Wits appraisal is performed by measuring the distance between which two projected points?

Accepted Answer

A and B points projected perpendicularly onto the functional occlusal plane

Answer

The Wits appraisal drops perpendiculars from A and B points to the functional occlusal plane, measuring the distance between those projected points (AO and BO).

Question 3

In Tweed's diagnostic triangle, what is the ideal value for the IMPA (Incisor-Mandibular Plane Angle)?

Accepted Answer

87°

Answer

Tweed's ideal IMPA is 87° (with FMA = 25° and FMIA = 68°), reflecting a slightly proclined lower incisor relative to the mandibular plane.

Question 4

In Downs' cephalometric analysis, what does the Y-axis (Sella-Gnathion to Frankfort Horizontal) primarily indicate?

Accepted Answer

Direction and pattern of mandibular growth

Answer

The Y-axis angle (normal ~59–66°) indicates the direction of mandibular growth, with lower values suggesting forward growth and higher values suggesting downward-backward growth.

Question 5

The cephalometric landmark A point (Subspinale) is defined as which point on the maxilla?

Accepted Answer

Deepest point on the curvature of the maxillary alveolar process between ANS and prosthion

Answer

A point is located at the deepest concavity on the anterior surface of the maxillary alveolar process, between the anterior nasal spine and the upper incisor.

American Board of Orthodontics (ABO) Practice Test

American Board of Orthodontics (ABO) Practice Test

ABO Cephalometric Analysis and Radiographic Interpretation 2