SNA Angle
Pronunciation: S-N-A angle
Also written as: SNA — Sella–Nasion–A point Angle
A cephalometric measurement expressing the antero-posterior position of the maxilla relative to the cranial base, with a normative value of approximately 82°.
Full Definition
The SNA angle is formed at the nasion by lines connecting the sella turcica (S), nasion (N), and A point (the deepest point on the anterior maxillary contour). It quantifies how far forward or backward the maxilla is positioned relative to the cranial base: values above the norm indicate maxillary prognathism, values below indicate maxillary retrognathism. SNA is a core measurement in virtually all cephalometric analysis systems and is reported in all lateral cephalogram analyses in orthodontic case records. Editors should render the abbreviation in all capitals without periods (SNA, not S.N.A.) and ensure it is distinguished from the companion measurement SNB (mandibular position) and ANB (jaw-to-jaw relationship).
Usage
Usage note: Render as 'SNA' (no periods, all caps). Always present alongside SNB and ANB for full skeletal classification. Normative value (~82°) should be stated when contextualising findings for a lay or mixed readership.
In Context
- "The cephalometric report recorded an SNA angle of 85°, confirming mild maxillary prognathism." — Cephalometric analysis report
- "Tables 2 and 3 use both 'SNA' and 'S-N-A'; standardize to 'SNA' throughout per the journal's abbreviation convention." — Manuscript editing note