Validity of Pi Angle in Comparison with Various Sagittal Discrepancy Indicators and its Correlation with Size and Position of the Mandible: A Cephalometric Study

To validate Pi angle with other sagittal discrepancy indicators like Beta angle, Yen angle and W angle in skeletal Class I, II and III patients, to correlate the Pi angle with the size and position of the mandible, and to evaluate the reliability of Dolphin imaging software.

One hundred fifty subjects were nominated based on the inclusion criteria and their lateral cephalograms were traced based on their ANB angle, they were placed into skeletal Class I, II and III groups. A-P discrepancy indicators and parameters of the size and position of the mandible were traced manually and digitally.

Pi angle had 85% and 100% accuracy in identifying skeletal Class II and III groups, respectively. Parameters of the morphology of the mandible were found to have statistically significant correlation with Pi angle e.g., mandibular base length (-0.265), SNB (-0.408), articular angle (0.277), facial angle (-0.800), and Y axis (0.728), etc.  When data was compared between manual and digital tracing, there was no difference in the mean values of Pi angle (P=0.87), Beta angle (P=0.73), and Yen angle (P=0.64) between the two techniques, suggesting good accuracy of Dolphin imaging software.

The Pi angle could accurately differentiate the sample into skeletal Class I, II and III groups. A statistically significant correlation was determined between Pi angle and most of the parameters of the size and position of the mandible. It was found that the imaging software Dolphin 3D is dependable to the analysis of cephalometric variables, which are not available in the software.