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Occlusal Plane to Mandibular Ramus (Xi) Sign Direction in Custom Measurement
yanidia00
Hello,
I am creating a custom Ricketts analysis and I am having difficulty reproducing a measurement, Occlusal Plane to Mandibular Ramus (Xi).
According to the Ricketts definition, the value should be:
Positive (+) when the occlusal plane is above Xi.
Negative (-) when the occlusal plane is below Xi.
Using the custom measurement:
Type: distance_A_BC_signed
Point A: Xi
Point B: Anterior occlusal point
Point C: Posterior occlusal point
The distance magnitude appears to be correct, but the sign is reversed. The measurement seems to calculate Xi relative to the occlusal plane instead of the occlusal plane relative to Xi.
For example, in my test case the occlusal plane is clearly above Xi, but WebCeph returns -2.3 mm instead of +2.3 mm.
I have also tested several other measurement types (distance_A_to_B_perp_CD_signed, distance_AB_along_CD, etc.) without success.
Is there a recommended custom measurement setup to reproduce the original Ricketts definition correctly, including the sign direction?
Thank you.