| Measurement | Definition |
| U6-U6 (mm) | Intermolar width was measured as the distance between the right and left mesiolingual cusps of the first molars at the gingival margin |
| U5-U5 (mm) | Interpremolar maxillary arch width measured between the left and right secondpremolar at the gingival margin |
| U4-U4 (mm) | Interpremolar maxillary arch width measured between the left and right first premolar at the gingival margin |
| U3-U3 (mm) | Intercanine maxillary arch width measured between the left and right canines at the gingival margin |