For the treatment planning and subsequent follow-up in orthognathic surgery is very important to use standardized tools. Today we use images from a Cone Bean scanner which cannot resort to the usual references radiographs as natural head position or the true horizontal taking from a plumb.

Aim: To compare image files obtained by volumetric scanner pre surgical orthognathic patients with and without default orientation of these images.

Out of 30, pre surgical patients, 15 patients were randomly selected. They underwent the same surgical planning protocol, which includes a volumetric scanner; using an Icat FOV of 22 mm. For all the patients clinical true horizontal was transfer to his face using the Holta method, so the marked references are captured by the scanner.

DICOM files obtained with the manipulation of the image done as usual by the X-ray technician based on anatomical and arbitrary decisions were taken into nemoscan software for usual cephalometric tracings.

The horizontal reference being given by the software was used to measure 5 angles using nasion.basion, sella.nasion, Frankfort plane, SNP-SNA and mandibular plane.

The same files were used to repeat this study; only this time one operator uses the true horizontal marked clinically by Holta method to orientate the imaging according to it.

Statistically significant differences between the groups of this study were found for all the angles measured.

In this study, Holta method used to determine the true horizontal, proved more reliable guide than the simple arbitrary assessment of the scanner operator.

Conflict of interest: None declared.