SNA Angle — MFDS Part 1 MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: A — The anteroposterior position of the maxillary apical base relative to the anterior cranial base
The SNA angle is formed by the Sella–Nasion and Nasion–Point A lines and assesses the anteroposterior position of the maxillary apical base relative to the anterior cranial base. Therefore, A is correct. The relationship between the maxillary and mandibular apical bases is assessed by ANB, not SNA, so B is incorrect. Maxillary incisor inclination requires a dental measurement such as the upper incisor to maxillary plane angle, excluding C. Vertical skeletal relationships are assessed using measurements involving the maxillary, mandibular or cranial-base planes, excluding D. Dental-arch width is a transverse model or scan measurement, not an SNA measurement. SNA should be interpreted with other findings because cranial-base inclination and landmark position can influence its value.
Reference: Hammad T, et al. Effect of maxillary and mandibular extrusion arches on dentoskeletal changes in adults with anterior open bite: a quantitative analysis. Figure 3 cephalometric definitions. Angle Orthodontist. 2023;93(1):26–32. https://pubmed.ncbi.nlm.nih.gov/36066246/