the study is discarded by the sponsor.

The aim of this prospective, multicentric, randomized, open-label study is to assess the efficacy of the removable Twicare® as mandibular propulsive appliance in children aged from 7 to 12 years old in the course of their orthodontic treatment, showing its noninferiority with the removable Herbst. One untreated group will be included to control the internal validity of the study as recommend in noninferiority trials. Patients will have a follow-up every two months during 6 to 12 months as planned in routine care.

A large number of functional appliances, mandibular advancement activators with various designs, fixed or removable, are used in Class II malocclusion correction; one of the largest means being used is the Herbst. These appliances can be individualized, made to measure by the prosthetist or standardised (on market). A new medical device, EC marked and marketed since 2011, the Twicare®, can be used as positioner, growth activator, but also for lingual re-education.

There are numerous publications comparing the activators' effects or the appliance effects on mandibular growth, but none have studied the Twicare®. The aim of this study is to assess the efficacy of this specific removable appliance in mandibular advancement in Class II skeletal in children aged from 7 to 12 years old. The appliance will be compared with the Herbst and one untreated group will be included to control the internal validity of the study as recommend in noninferiority trials.

Patients will have a follow-up every two months during 6 to 12 months until the Class I occlusion is achieved. A lateral cephalogram and a dental silicon impression will be performed at the beginning (T0) and at the end of the treatment (T1) in order to evaluate cephalometric measurement changes, ANB, overjet and canine and molar class evolutions. The data collected at the beginning and at the end of the treatment will be analyzed and compared aware from patient, treatment and time, in order to assess the Twicare® noninferiority compared to the Herbst and to confirm the superiority of these two appliances versus observation. We will study, in parallel, the nasal ventilator function as well as comfort, compliance, tolerance and acceptability of the device via an auto-questionnaire.

Inclusion Criteria:

• Children with Class II division 1 malocclusion
• Overjet ≥ 4 mm,
• ANB > 4°,
• Good cooperation (motivation and good dental hygiene),
• Incisors width compatible with the available Twicare® appliance sizes, according to the manufacturer recommendations.
• Written Informed Consent of the Child,
• Affiliated to health insurance,
• Parents able to receive informed consent and to express their approval for their child to take part in this investigation.

Exclusion Criteria:

• Non well-balanced periodontal disease,
• Temporal-mandibular dysfunction,
• Severe bruxism noctural episodes,
• Known allergy or intolerance to one of the activators' components.
• Foreseeable follow-up difficulties,
• Minor under guardianship,
• Simultaneous participation to an interventional study.