Which option defines the NAPg angle in retrognathism of the lower jaw?

Which option defines the NAPg angle in retrognathism of the lower jaw?

• A. More than norm
• B. 180º
• C. Less than norm
• D. 170º

Answer: (A)

The NAPg angle measures how far back the mandible sits in relation to the cranial base, by the angle formed between the line from nasion to A-point and the line from A-point to pogonion. When the lower jaw is retrognathic, pogonion sits further posteriorly, so the A–pogoniion segment tilts more backward relative to the nasion–A line. This increases the angle at A, making the NAPg angle larger than its normal value. So describing it as greater than normal best captures retrognathism of the mandible. Smaller angles would imply a more forward-positioned mandible, which isn’t the case here.

The NAPg angle measures how far back the mandible sits in relation to the cranial base, by the angle formed between the line from nasion to A-point and the line from A-point to pogonion. When the lower jaw is retrognathic, pogonion sits further posteriorly, so the A–pogoniion segment tilts more backward relative to the nasion–A line. This increases the angle at A, making the NAPg angle larger than its normal value. So describing it as greater than normal best captures retrognathism of the mandible. Smaller angles would imply a more forward-positioned mandible, which isn’t the case here.