2.1. Cephalometric Parameters

The investigation of the Herbst appliance effects at the dental and skeletal levels was performed on lateral cephalograms using the modified SO (sagittal occlusion) Pancherz's cephalometric analysis.

This analysis was carried out by transferring the lines occlusal line (OL) and occlusal perpendicular line (OLp) through the Sella from pretreatment lateral cephalogram to the posttreatment lateral cephalogram by superimposing skeletal stable structures of the anterior cranial base. Modified SO Pancherz's cephalometric analysis included the following parameters, that are not considered in traditional SO Pancherz analysis: skeletal divergence, skeletal class, and lower incisor inclination (Figure 1).

Modified SO Pancherz analysis. Reference points and lines: Sella (S), Nasion (N), subnasal (A), pogonion (Pg), Gonion (Go), Menton (Me), articular (Ar), anterior nasal spine (ANS), maxillary incisal (Is), mandibular incisal (Ii), lower incisal apex (API), posterior occlusal (OCLP), maxillary molar (Ms), mandibular molar (Mi), occlusal line (OL), and occlusal line perpendicular (OLP).

Cephalograms were performed with teeth in centric occlusion, with relaxed lips and head oriented parallel to the floor according to the Frankfurt plane.

For each patient of the test group, two lateral cephalograms were included: pretreatment (T1) and posttreatment (T2).

Cephalometric analysis was performed by a single operator using Delta-Dent® software (Orthopiù SRL).