The aim of this study will to evaluate the root resorption after RME by hyrax and hybrid hyrax appliances by using of cone beam computed tomography .

Inclusion Criteria:

1. skeletal maxillary transvers deficiency
2. unilateral or bilateral posterior crossbite
3. negative buccal corridor
4. patient with good oral hygiene
5. patient with no previous orthodontic treatment
6. no systemic disease

Exclusion Criteria:

1. craniofacial congenital anomalies
2. a history of periodontal disease
3. incomplete treatment records