Sella landmark variability and its effect on the Angles SNA and SNB: a comparative study

ABSTRACT Objective: To determine intra- and inter-observer precision in Sella (S), Nasion (N), point A and B identification. Additionally, to determine how it can interfere with angular measurements of SNA and SNB by orthodontists and dentomaxillofacial radiologists. Methods: Twenty digital lateral cephalometric radiographs were evaluated by five orthodontists and five dentomaxillofacial radiologists. Results: Differences in linear and angular measuremts were assessed. Intra- and inter-observer agreement was evaluated. Intra- and inter-observer reproducibility of the horizontal and vertical components of the S landmark identification (ICC: 0.75/0.90). Orthodontists tended to produce larger SNA (-0.18º), while SNB angle had a tendency to be smaller (0.55º). In general, SNA angle was smaller (DMFRs: -0.308º and orthodontists: -0.092º), and SNB presented with larger values (DMFR: 0.078º and orthodontists: -0.074º). Conclusion: Identification of the Sella landmark revealed a better agreement amongst dentomaxillofacial radiologists. Orthodontists, however, showed a larger variability in S identification and, consequently, the SNA and SNB angles drifted significantly.