A simple assessment used by the author includes an algorithm that evaluates four elements: the absolute transverse measurement; the curve of Wilson; tooth-arch requirements (crowding); and the inclination of the buccal segments. By using this calculator, the surgical-orthodontic team can be aided in the decision whether a case can be treated by segmentation of the maxilla during OGS or that a SARPE is needed prior to orthodontic level and alignment.

Instructions: Measure the central fossa of the upper maxillary 1st molar compared to the distal buccal cusp of the lower mandibular 1st molar (or measure the relationship in the predicted (final) class I molar occlusion).