Aim: Frankfurt horizontal and Sella-Nasion lines are the most widely accepted and used landmarks in cephalometric analysis. This study investigates the use of the Orbito-Condylion line extending from the Orbitale to the Condylion as a novel horizontal line for substituting the Frankfurt horizontal line. Similarly, the evaluation of the Orbito-Basion line as an alternative to the Sella-Nasion line in cephalometric analysis was done. We evaluated the reproducibility of the new horizontal lines and measured the angle between the Orbito-Condylion line and the Frankfurt line; and the angle between the Sella-Nasion and Orbitale-Basion line.
Methods: This investigation was carried out on 30 individuals. The Porion, Orbitale, Condylion, Sella, Nasion, and Basion were identified and marked. The angles between the orbito-meatal line (inferior orbital rim to the Porion; the Frankfurt line) and the Orbito-Condylion line (inferior orbital rim to the Condylion) were measured. Likewise, the angles between the Sella-Nasion line (center of sella tursica to Nasion) and the Orbito-Basion line (inferior orbital rim to Basion) were measured.
Results: Significant interobserver and intraobserver bias did not exist. The mean angle between the Frankfurt line and Orbito-Condylion line was 0.5°±2.27° and the mean angle between the Sella-Nasion line and Orbito-Basion line was 3.48°±3.11°.
Conclusion: This study showed the new lines have good reproducibility, reliability, and efficacy. The Orbito-Condylion and Orbito-Basion lines are reliable, reproducible, and easily identifiable, and has the potential as novel standard horizontal lines to supersede or complement the Frankfurt line and Sella-Nasion line in anthropological studies and clinical applications.