Table 1 Definitions of the landmarks in the study

U6c

Mesiobuccal cusp tip of the maxillary first molar

U6r

Mesiobuccal root apex of the maxillary first molar

U5c

Buccal cusp tip of the maxillary second premolar

U5r

Root apex of the maxillary second premolar

U3c

Cusp tip of the maxillary canine

U3r

Root apex of the maxillary canine

U2c

Midpoint of maxillary lateral incisor’s incisal edge

U2r

Root apex of the maxillary lateral incisor

U1c

Midpoint of maxillary central incisor’s incisal edge

U1r

Root apex of the maxillary central incisor