Definitions of Terms Anterior Cranial Base: The distance from Nasion (N) to Sella (S). Skeletal Class of the Mandible: The combina-tion of the size, position and rotation of the mandible relative to the anterior cranial base. Balance is a Class I, retrognathic a Class II, and prognathic a Class III. Skeletal Division of the Maxilla: 1) Position: Forward to the anterior cranial base Division One; back of the anterior cranial base Division Two. 2) Length: Balanced in length relative to the length of the anterior cranial base Division One; short rela-tive to the length of the anterior cranial base Divi-sion Two. Dental Division: The angle of the upper incisor relative to the Frankfurt Horizontal Plane. An angle of 115 degrees is a Division One; under 115 degrees a Division Two; over 115 degrees is a Division Three. (1)(2) Functionally-Influenced Bone: Bone that devel-ops from the ectoderm forming dermal bone such as the body of the maxilla and the upper and lower dental alveolar ridges. Fig. 2 Genetically-Driven Bone: Bone that develops from the mesoderm forming chondral bone such as the mandible and the long bones of the body.(2) Cephalometric Terms & Land Marks: (Fig. 2) Orbitale (Or): The lowest point on the inferior boney margin of the orbit. Porion (Po): The external skeletal auditory meadius. Frankfurt Horizontal Plane (FH): The black hori-zontal plane tangent to the top of Po tangent to Or. Point (T): The apex of the pterygomaxillary fisher. T-Vertical Plane: The black vertical plane passing through Point-T and perpendicular to the Frankfurt Horizontal Plane. Sella (S): The center of Sella Turcica. Nasion (N): The most anterior point on the nasal frontal suture. Point (A): The anterior junction of the alveolar process and the body of the maxilla. Point (B): The anterior junction of the alveolar process and the corpus of the mandible. A-T Length: The length of the maxilla projected on the Frankfurt Horizontal Plane. www.orthodontics.com July/August 2010 33
Journal of the American Orthodontic Society July-August 2010/Buyer's Guide: Page 33
