Which of the following cephalometric parameters suggest skeletal class III malocclusion?

 # Which of the following cephalometric parameters suggest skeletal class III malocclusion?

1. ANB is less than 0 degree

2. SNA= 84 degrees

3. SNB=82 degrees

4. Wit’s appraisal shows point A before point B

5. FMA is 40 degrees (INICET 2025)

A. 1, 4 and 5

B. 1 and 3

C. 2, 4 and 5

D. 3, 4 and 5

The correct answer is B. 1 and 3. 

Explanation:

• 1. ANB is less than $$\begin{gathered} 0 \\ degrees: \end{gathered}$$ A negative ANB angle indicates that point B (mandible) is anterior to point A (maxilla), which is a classic sign of skeletal Class III malocclusion.

• 3. SNB=$$\begin{gathered} 82 \\ degrees \end{gathered}$$: While the average SNB is around 80 degrees, an SNB of 82 degrees indicates a more protrusive mandible relative to the cranial base, which is consistent with a Class III tendency (especially if SNA is normal or reduced). In contrast, SNA=84 degrees (option 2) suggests a protrusive maxilla, which is typically seen in Class II, not Class III.

• 4. Wit’s appraisal shows point A before point B: This indicates a Class II skeletal relationship, where the maxilla is anterior to the mandible. For Class III, point B would be anterior to point A.

• 5. FMA is $$\begin{gathered} 40 \\ degrees \end{gathered}$$: FMA (Frankfort Mandibular Plane Angle) indicates the vertical growth pattern. A high FMA (40 degrees is significantly high) suggests a vertical growth pattern or an open bite tendency, but it does not directly indicate a sagittal Class III relationship.