Which cephalometric plane is defined by the Porion (Po) and Orbitale (Or)?

Which cephalometric plane is defined by the Porion (Po) and Orbitale (Or)?

• A. Sella-Nasion Plane
• B. Frankfort Horizontal Plane
• C. Palatal Plane
• D. Mandibular Plane

Answer: (B)

The Frankfort Horizontal Plane is defined by the Porion and Orbitale. Porion is the upper point on the external auditory meatus and Orbitale is the lowest point on the infraorbital rim. This plane is used as a primary reference in cephalometrics because, when the head is in natural head position, it runs approximately horizontal, providing a stable baseline to orient measurements of skeletal and dental relationships. The other planes are defined by different landmarks—Sella-Nasion by Sella and Nasion, Palatal by ANS and PNS, and Mandibular by Gonion and Menton—so they are not defined by Po and Or.

The Frankfort Horizontal Plane is defined by the Porion and Orbitale. Porion is the upper point on the external auditory meatus and Orbitale is the lowest point on the infraorbital rim. This plane is used as a primary reference in cephalometrics because, when the head is in natural head position, it runs approximately horizontal, providing a stable baseline to orient measurements of skeletal and dental relationships. The other planes are defined by different landmarks—Sella-Nasion by Sella and Nasion, Palatal by ANS and PNS, and Mandibular by Gonion and Menton—so they are not defined by Po and Or.