In deep occlusion, which cephalometric angle tends to decrease?

In deep occlusion, which cephalometric angle tends to decrease?

• A. SNA
• B. IMPA
• C. ANB
• D. FMA

Answer: (D)

FMA reflects vertical growth pattern by measuring the angle between the Frankfort horizontal and the mandibular plane. In a deep bite, the vertical dimension is reduced (a hypodivergent pattern), so the mandible sits with a flatter plane relative to the cranial base. This makes the mandibular plane closer to Frankfort, decreasing the FMA. In contrast, open bite usually shows a higher FMA due to a steeper mandibular plane. SNA and ANB describe anteroposterior relationships, and IMPA reflects incisor inclination, which are not the primary vertical indicator here. So the angle that tends to decrease in deep occlusion is the FMA.

FMA reflects vertical growth pattern by measuring the angle between the Frankfort horizontal and the mandibular plane. In a deep bite, the vertical dimension is reduced (a hypodivergent pattern), so the mandible sits with a flatter plane relative to the cranial base. This makes the mandibular plane closer to Frankfort, decreasing the FMA. In contrast, open bite usually shows a higher FMA due to a steeper mandibular plane. SNA and ANB describe anteroposterior relationships, and IMPA reflects incisor inclination, which are not the primary vertical indicator here. So the angle that tends to decrease in deep occlusion is the FMA.