Obstructive Sleep Apnea syndrome (OSA) shows a 10% morbidity rate in children with a higher rate between the ages of 3 and 5. Generally speaking, its prevalence is underestimated. Furthermore, detecting OSA remains difficult due to its particular physiopathology. The decrease in nasopharyngeal airway dimensions is the most common etiology. This decrease is related to soft tissues as well as maxillomandibular abnormalities. The aim of the study is to show that reducing sleep apnea in children remains possible when inducing rapid palatal expansion and mandibular advancement using the Yookid™ system. The Yookid™ system associates a mandibular advancement appliance and repositioning of the patient during sleep.