Table 1 Cephalometric variables used in this study

SNA°

Angle formed by the sella-nasion line and line N-point A

Anteroposterior position of the maxilla in relation to the skull base

SNB°

Angle formed by the sella-nasion line and line N-point B

Anteroposterior position of the mandible in relation to the skull base

ANB°

Differences between the SNA and SNB angles

Relation between maxilla and mandible

SN-OP°

Angle formed by the sella-nasion line and the occlusal plane

Inclination of the occlusal plane in relation to the skull base

SN-PP°

Angle formed by the sella-nasion line and palatal plane

The degree of the maxilla inclination in relation to the anterior cranial base

PP-MP°

Angle formed by the palatal plane and mandibular plane

Relates the maxilla to the mandible in the vertical plane

SN-GoGn°

Angle formed by the sella-nasion line and mandibular plane

Inclination of the mandibular plane in relation to the skull base

1.NA°

Angle of inclination of the upper incisor in relation to the NA line

Extent of anterior inclination of the upper incisor

1-NA (mm)

Linear distance between the most salient point of the buccal side of the upper incisor and the NA line measured perpendicularly to the latter

Extent of anterior inclination of the upper incisor

1.NB°

Angle of inclination of the lower incisor in relation to the NB line, which determines the extent of anterior inclination of the lower incisor

Extent of anterior inclination of the lower incisor

1-NB (mm)

Linear distance between the most salient point of the buccal side of the lower incisor and the NB line measured perpendicularly to the latter

Extent of anterior inclination of the lower incisor

Overjet (mm)

Horizontal distance between incisors edges

The degree of overjet

Overbite (mm)

Vertical distance between incisors edges

The degree of overbite

SPAS (mm)

the thickness of the airway behind the soft palate along a line parallel to the Go-B point plane

Obstruction of superior posterior airway space

PAS (mm)

Linear distance between a point at the base of the tongue and another point on the posterior wall of the pharynx, both measured by the extension of a line from point B to point Go

Obstruction of posterior airway space

MP-H (mm)

Linear distance between H, the most anterosuperior point of the hyoid bone, and the mandibular plane measured perpendicularly to the latter

Risk of occlusion, that increases directly with the distance

C3-H(mm)

Linear distance between C3 and H, where C3 is the most anteroinferior point of the third cervical vertebra

Risk of occlusion, that increases inversely with the distance