[A critical analysis of the SNA, SNB and ANB angles in assessing orthodontic treatments].

The purpose of this longitudinal cephalometric study was to evaluate the influence of growth changes at nasion (N) on the position of the reference line NSL and consequently on the measurements of the angles SNA, SNB and ANB. Lateral head films from 46 orthodontically treated patients were evaluated over an average period of 3.7 years. The NSL reference line was defined with respect to growth changes at the N-point: A: no consideration of growth; B: consideration of growth in the sagittal plane; C: consideration of growth in the sagittal and vertical planes. The results showed that growth changes at nasion had a decisive influence on the position of the reference line NSL and thus also on the angles SNA, SNB and ANB. In order to avoid misinterpretations in the evaluation of orthodontic treatment results the growth changes at nasion must be taken into consideration.