Cephalometrics in Orthodontics: 3D vs 2D Radiographs

Cephalometrics in Ortho

• Replacing 2D with 3D CBCT, allowing for a multi-aspect view (x, y, z format) of the entire craniofacial structure with one radiograph.

Cephalometric Landmarks and Planes

• Cephalometric landmarks are points used in precise evaluation of 2D measurements like length, width, or height.
• Global acceptance of cephalometric landmark definitions and associated linear and angular measurements is essential for standardized classification and discussion of growth, development, and treatment outcomes.

Hard Tissue Landmarks

• Sella point (S): Center of Sella turcica.
• Orbitale (Or): The lowest point on the inferior margin of the orbit.
• ANS (Anterior Nasal Spine): Sharp median process formed by the forward prolongation of the two maxillae at the lower margin of the anterior aperture of the nose.
• PNS (Posterior nasal spine): The most posterior point at the sagittal plane on the bony hard palate.
• A point: The most posterior point on the curve of the maxilla between the anterior nasal spine and supradentale.
• B point: The deepest point of the anterior alveolar bone recess of the mandible.
• Pogonion (Pog): The most anterior part of the chin.
• Gnathion (Gn): Most anteroinferior point on the contour of the bony chin symphysis.
• Menton (Me): Most inferior point on the symphysis of the mandible in the median plane.

Soft Tissue Landmarks

• Convexity: The intersection of soft tissue nasion–subnasale line (N ′ Sn) and the subnasale–soft tissue pogonion line (SnPg ′).
• The angle of facial convexity: Angle formed between the glabellasubnasale line (GSn) intersecting with the SnPg ′ line.
• In females, a more convex profile is considered esthetically pleasing, while straighter profiles are generally preferred for males.

Ricketts E-Line

• Ricketts E-line (esthetic plane): Drawn from the tip of the nose to Pg ′.
• Ideally, the upper lip is about 4 mm behind this reference line, while the lower lip lies about 2 mm behind it.

Cephalometric Planes

• Horizontal planes:
  • SN Plane: Connecting the midpoint of sella turcica with nasion, representing the cranial base.
  • Frankfort Horizontal Plane: Passing through porion and orbitale.
  • Maxillary Plane: Passing through anterior nasal spine and posterior nasal spine.
  • Occlusal Plane: Passing through occlusal surface of 1st molars and incisal edge.
  • Mandibular Plane: Passing through gnathion, pogonion, and menton.
• Other points:
  • Gonion (Go): Midpoint of the angle of the mandible.
  • Articulare (Ar): Intersection of the lateral radiographic image of the posterior border of the ramus with the base of the occipital bone.
  • Basion (Ba): The most inferoposterior point on the anterior margin of the foramen magnum.
  • Glabella: The height of curvature of the bone overlying the frontal sinus.
  • Porion (Po): A point located at the most superior point of the external auditory meatus.
  • Pterygoid Point (Pt): Intersection of the inferior border of the foramen rotundum with the posterior wall of the pterygomaxillary fissure.

Soft Tissue Landmarks

• Trichion (Tri): Hairline.
• Soft tissue Glabella: The most prominent midline point in the midsagittal plane between the eyebrows.
• Subnasale (Sn): The point at which the columella (nasal septum) merges with the upper lip in the midsagittal plane.
• Stomion (St): The contact point between the upper and lower lip at the mouth slit.
• Soft tissue menton (Me’): The most inferior point on the soft tissue chin.
• In an ideal lower third, subnasale to stomion (St) comprises the upper third, while menton to stomion (or the top of the lower lip) make up the lower two-thirds.