CT Cone Beam not only gives us three-dimensional images of spectacular quality, less radiation, better access to patients than the conventional CT, it also gives us an excellent manipulation of the image through software. This manipulation gives the disadvantage that we lose the standardization of the patient’s position; standardization that through the years had been accepted as oriented natural head position.

Forty-two patient were included, all patient had a bimaxillary Ct cone beam taken (i-CAT). Determination of the clinical true horizontal on oriented natural head position was used with HOLTA system which utilize spirit levels. The orientations lines of the i-Cat machine were aligned through the marks previously described. Both the position of the pt and the calibration of the instrument were tested by Shapiro-Wilk test and t -test with p value of 95%. Determination the accuracy of the instrument calibration was performed on the absolute differences of values.

The average difference was 1.3° and standard deviation was 0.9° for HOLTA system. In the sagital view angle the average was 0.33° with a standard deviation of 1.4° and the angle in the coronal view was 0.078° with a standard deviation of 1.6°.

Shapiro-Wilk test showed p = 0.19 for the HAB angle and p = 0.096 for the angle HAC, tending 0.

This study demonstrate that the ONHP is reproducible on the CT cone beam, and the HOLTA system is a accurate method to transfer the true horizontal line to the patient.

Conflict of interest: None declared.