Figure 6. Definitions of arch width variables. Intercanine width (ICW), distance between the cusp tip of right and left maxillary canines; interfirst premolar width (IP1W), distance between the cusp tip of right and left maxillary first premolars; intersecond premolar width (IP2W), distance between the cusp tip of right and left maxillary second premolars; interfirst molar width (IM1W), distance between the mesiobuccal cusp tip of right and left maxillary first molars; intersecond molar width (IM2W), distance between the mesiobuccal cusp tip of right and left maxillary second molars.