Cone-Beam Computed Tomography-Based Three-Dimensional McNamara Cephalometric Analysis.

ABSTRACT

This article introduces a method that extends the McNamara cephalometric analysis to produce 3-dimensional (3D) measurement values from cone-beam computed tomography images. In the extended method, the cephalometric landmarks are represented by 3D points; the bilateral cephalometric landmarks are identified on both sides of the skull; the cephalometric lines, with the exception of the facial axis, are represented by 3D lines; the cephalometric planes, with the exception of the facial plane, are represented by planes; the effective mandibular length, the effective midfacial length, and the lower anterior facial height are measured as 3D point-to-point distances; the nasion perpendicular to point A, the pogonion to nasion perpendicular, the upper incisor to point A vertical, and the lower incisor to point A-pogonion line are measured each as components of a vector; the facial axis angle is measured as a line-to-plane angle; and the mandibular plane angle is measured as a plane-to-plane angle. As a result, the method provides real effective lengths of the maxilla and mandible on both sides of the skull; real height of the lower anterior face; directed distances from the point A to the nasion perpendicular, from the pogonion to the nasion perpendicular, from the left and right upper incisor to the point A vertical, and from the left and right lower incisor to the point A-pogonion line for both the lateral and posteroanterior views of the skull; and real angles of the facial axis and the mandibular plane. Additionality, the method enables the identification of craniofacial asymmetries.