Table 1 Definitions of the parameters measured in the study

Skeletal measurements

FZS (Frontozygomatic suture)

Distance (mm) between the two points located at the edges of the zygomatic process of the frontal bone measured in the coronal section

ZMS (Zygomaticomaxillary suture)

Distance (mm) between the two points located at the superior edges of ZMS measured in the coronal section

NW (Nasal width)

Distance (mm) at the widest portion of the nasal aperture parallel to the hard palate

PM-NW and M-NW were measured in both upper first premolars (PM) and first molars (M) in the coronal section, respectively

NPF (Nasopalatine foramen)

Distance (mm) between the points located at the greater diameter of the nasopalatine foramen, bilaterally, measured in the axial section

GPF (Greater palatine foramen)

Distance (mm) between the points located at the posterior cortical of the greater palatine foramen, bilaterally, measured in the axial section

MPS ( Midpalatal suture gap)

Distance (mm) of midpalatal suture gap at upper central incisors apical level, measured in the axial section, immediately after expansion (T1)

Dentoalveolar measurements

MW(Maxillary width)

Distance (mm) of maxillary width tangent to the hard palate

PM-MW and M-MW were measured on both upper first premolars (PM) and first molars (M) in the coronal section

IDW (Interdental width)

Distance (mm) between the right and left buccal cusp tips

PM-IDW and M-IDW were measured on both upper first premolars (PM) and first molars (M) in the coronal section

DI (Dental inclination)

Angle (°) between the line passing through the palatal cusp tip and palatal root apex, and the vertical line perpendicular to the hard palate measured on upper first molars in the coronal section

Periodontal measurements

BBPT(Buccal bone plate thickness)

The shortest distance (mm) between the buccal cortical plate and the buccal root surface

PM-BBPT, M-BBPT (Mesial and Distal root) were measured on upper first premolars and mesial and distal first molars roots

PBPT(Palatal bone plate thickness)

The shortest distance (mm) between the palatal cortical plate and the palatal root surface

PM-PBPT and M-PBPT were measured on upper first premolars and palatine first molars roots