SNA Angle
Pronunciation: ess-en-ay angle
Also written as: SNA — Sella-Nasion-Point A
A cephalometric angle measured from sella to nasion to point A that quantifies the anteroposterior position of the maxilla relative to the cranial base.
Full Definition
The SNA angle is formed by three cephalometric landmarks: sella (S), nasion (N), and point A (the deepest point on the anterior maxillary alveolar contour). A normative value of approximately 82° (±2°) is used as a benchmark; values above this suggest maxillary prognathism, while values below indicate maxillary retrusion. Editors must ensure consistent use of degree symbols and correct landmark notation. The SNA angle is routinely reported alongside the SNB angle to characterise the sagittal jaw relationship. It is closely linked to, but should not be confused with, the ANB angle, which expresses the difference between SNA and SNB.
Usage
Usage note: Always include the degree symbol (°) when reporting numerical values; distinguish clearly from 'SNB angle' and 'ANB angle' in cephalometric results tables.
In Context
- "The patient's SNA angle of 78° confirmed maxillary retrusion as the primary component of the Class III relationship." — Cephalometric analysis report
- "Post-treatment SNA angles were compared with pre-treatment values to quantify maxillary advancement following facemask therapy." — Clinical trial results section