If the mandible is positioned more posteriorly, how is the SNB angle affected?

When the mandible is positioned more posteriorly, the SNB angle, which is the angle formed between the sella-nasion line (SN) and the line connecting the sella to the Gonion (B point or point B), decreases. This decrease occurs because, as the mandible moves backward, the position of point B (the most anterior point on the symphysis of the mandible) shifts in a way that reduces the angle between the SN line and the line connecting the sella to point B.

The relationship of the mandible to the anterior cranial base is crucial in determining the SNB angle. As the mandible retracts or is positioned more posteriorly, the point B moves closer to the SN line, resulting in a smaller angle. This is particularly relevant in orthodontic assessments where understanding the positional relationships of the jaws impacts treatment planning and outcomes. An understanding of these changes is essential for interpreting cephalometric measurements accurately, as they provide insights into skeletal relationships and the potential for growth or treatment effects.