Inclusion Criteria:  For the Working Group;  Absence of a syndrome or disease affecting the craniofacial and general systemic condition Patients who have applied for treatment due to the need for orthodontic treatment Adequate radiographic and three-dimensional dental model records before treatment Bilateral posterior crossbite Absence of anterior crossbite Absence of loss of lower and upper first permanent molars and eruption of all 4 permanent molars  For the Control Group;  Absence of a syndrome or disease affecting the craniofacial and general systemic condition Patients who have applied for treatment due to the need for orthodontic treatment Adequate radiographic and three-dimensional dental model records before treatment Absence of posterior and anterior crossbite Absence of loss of lower and upper first permanent molars and eruption of all 4 permanent molars  Exclusion Criteria:  Presence of a syndrome and disease affecting the craniofacial and general systemic condition Absence of radiographic and dental model records Losing any of the lower or upper permanent first molars Presence of anterior crossbite