Skeletal and Dental Changes with Hyrax-type Rapid Maxillary Expander Anchored to Permanent Versus Deciduous Molars

Inclusion Criteria: * Patient coming to the dental clinic for a first orthodontic consultation in mixed dentition * Patient aged 6 to 12 years * Patient with a transverse maxillary deficiency requiring rapid maxillary expansion * Presence of 1st permanent molars "6" and 2nd deciduous "V" molars with sufficient root length Exclusion Criteria: * Syndromic patients (all syndromes combined: cleft lip, etc.) * Patient with V or 6 with decays (or with major root resorption) * Patient with oral hygiene non compatible with orthodontic treatment * Failure to obtain informed written consent * No affiliation to a French national medical health system * Patient with a legal protection measure