Table 1.

Variable Definitions

Variable	Definition
Transversal distances (mm)
Nasal cavity width	The greater width of the nasal cavity lower third measured in parallel to the horizontal plane
Palatal root distance width	Dental arch width measured at the most apical level of the palatal roots parallel to the horizontal plane
Maxillary width	Maxillary width at the level of the hard palate parallel to the horizontal plane
Palatal alveolar crest width	Maxillary width at the level of the interpalatal alveolar crest parallel to the horizontal plane
Buccal alveolar crest width	Maxillary width at the level of the buccal alveolar crest parallel to the horizontal plane
Arch width	Dental arch width measured at the level of the buccal cusp points parallel to the horizontal plane
Tooth inclination	Angle between lines passing through the buccal and lingual cusp tips of the first molars
Dental model analysis (mm)
6-6 width	Intermolar width measured at the level of the cusp tips
5-5 width	Inter–second premolar width measured at the level of the cusp tips
4-4 width	Inter–first premolar width measured at the level of the cusp tips
3-3 width	Intercanine width measured at the level of the cusp tips
Arch length	Arch length measured perpendicularly in the horizontal plane from a line connecting the mesial aspects of the first permanent molars to the mesial edge of the right permanent incisor
Arch perimeter	Arch perimeter measured by the sum of four segments connecting the mesial aspect of the right first permanent molar to the mesial aspect of the left first permanent molar