Measurements

Lateral cephalograms were rendered from the cone beam computed tomography data volumes (0.3 mm voxel size) using the right side of the skull and a portion of the left extending to the medial border of the left orbit. They were oriented on the midsaggital and Frankfort planes and digitized by one examiner using Dolphin Imaging (Patterson Technology, Chatsworth, CA).

The patients were compared to 22 untreated controls matched based on age, sex, molar classification, and pretreatment mandibular plane angle. The controls were drawn from records collected by the University of Montreal Growth Study. Lateral cephalograms were traced and the landmarks were identified.

Seventeen cephalometric landmarks were digitized by the same examiner using standard definitions ( Figure 1 ) from which eight measurements were computed:

• AP skeletal: mandibular protrusion (S-N-B) and chin projection (S-N-Pg)

• Vertical skeletal: mandibular plane angle (S-N/Go-Me) and total anterior face height (N-Me)

• Vertical dental: maxillary molar (U6⊥ANS-PNS), maxillary incisor (U1⊥ANS-PNS), mandibular molar (L6⊥Go-Me), mandibular incisor (L1⊥Go-Me), and overbite

All radiographs were digitized by the same examiner. All linear measurements were adjusted to eliminate magnification. Intra-examiner reliability was measured by replicate analyses of 15 subjects. There were no statistically significant systematic differences; landmark method errors were less than 0.5 mm.

Summary

• Lateral cephalograms were created from cone beam computed tomography data using a 0.3 mm voxel size.
• The right side of the skull and part of the left (to the medial border of the left orbit) were used, oriented on the midsagittal and Frankfort planes.
• Digitization was performed by one examiner using Dolphin Imaging software.
• Patients were compared to 22 untreated controls matched by age, sex, molar classification, and pretreatment mandibular plane angle from the University of Montreal Growth Study.
• Seventeen cephalometric landmarks were traced and identified, enabling the computation of eight key measurements.
• These measurements included:
  • AP skeletal: mandibular protrusion (S-N-B) and chin projection (S-N-Pg).
  • Vertical skeletal: mandibular plane angle (S-N/Go-Me) and total anterior face height (N-Me).
  • Vertical dental: maxillary molar (U6⊥ANS-PNS), maxillary incisor (U1⊥ANS-PNS), mandibular molar (L6⊥Go-Me), mandibular incisor (L1⊥Go-Me), and overbite.
• All linear measurements were adjusted to eliminate magnification, and intra-examiner reliability showed no significant systematic differences, with landmark method errors below 0.5 mm.