Test Your Knowledge on Cephalometrics

Cephalometrics: Key Concepts and Terminology

• Cephalometrics is a diagnostic tool used in orthodontics to assess skeletal relationships and plan treatment.

• Various reference planes and points are used in cephalometric analysis, such as the Frankfort horizontal plane, S-N plane, sella-nasion point, and pogonion.

• The ANB angle measures the anteroposterior relationship between the maxilla and mandible, with a normal value of 2 degrees.

• The SNA angle assesses the position of the maxilla relative to the cranial base, while the SNB angle does the same for the mandible.

• The FMA angle measures the rotation of the mandible, with a value of 25 degrees indicating backward rotation.

• The Y-axis is a growth axis that indicates the direction and amount of facial growth.

• Different cephalometric analyses, such as Down's analysis, Steiner analysis, and Tweed's analysis, can be used to evaluate skeletal relationships and malocclusions.

• Cephalometric radiographs can assess vertical and transverse discrepancies, dental arch perimeter, and incisor position and angulation.

• Skeletal convexity is determined by joining specific points on the face, such as the glabella, prosthion, and supramentale.

• The nasal width/length ratio is a cephalometric measurement used to assess nasal aesthetics.

• Skeletal maturity can be assessed using hand wrist radiographs or by evaluating the development of specific bones, such as the clavicle or cervical spine.

• Cephalometric analysis is a crucial part of orthodontic treatment planning and can help assess the severity of malocclusions and predict treatment outcomes.Cephalometric Analysis and Treatment Options

• The Bolton cephalometer was devised in either 1930, 1927, 1931, or 1946.

• The mandible plane angle ranges from 17-30 degrees.

• The medial confluence of stress lines on the medial surface of the ramus that represents the arcial growth of the surface of the mandible is called the Pm Point.

• In a long face syndrome patient with increased lower facial height, the palatal plane inclination will be downward anteriorly.

• In a 5-year-old child with a smaller chin, distal step 2nd molar relation, narrow width of maxilla, normal SNA angle, decreased SNB angle, and low FMA angle, treatment options include waiting and watching for six years, using Klohen head gear to treat maxillary protrusion, using a FR II appliance, or using a Twin block appliance.

• The interincisal angle between deciduous incisors is 150 degrees.

• According to Ricketts esthetic plane, the lower lip lies 1 mm posterior to the plane.

• In Tweed’s analysis, if FMA is 35 degrees, the FMIA angle should be 65 degrees.

• When the core of the mandible rotates forward by 15 degrees, the mandibular plane angle decreases only by 2-4 degrees on average.

• The occipital pull chin cup can be used to treat mild to moderate mandibular prognathism and Class II skeletal cases.

• The occlusal plane is not used as a reference plane in Archial cephalometric analysis.

• In McNamara analysis, the Sella-Nasion plane and anatomic Frankfort horizontal plane are used as a reference plane.

Bonus Question:

• The possible cause of reverse overjet in a 9-year-old boy with a mild Class III skeletal pattern and reverse overjet, with SNA of 80 degrees and SNB of 82 degrees, is both forward displacement of mandible due to occlusal prematurities and a forward pattern of mandible growth.
• The appliance of choice for treatment would be the Delaire’s face mask, which would result in a backward and downward rotation of mandible.
• Other treatment options include using a chin cup, surgical orthodontics after growth of mandible is over, or using a reverse twin block.