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Functional Appliance — MFDS Part 1 MCQ

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ModerateOrthodontic PrinciplesFunctional ApplianceMFDS Part 1

A 12-year-old patient at the pubertal growth spurt has an 8 mm overjet and a skeletal Class II division 1 relationship caused predominantly by mandibular retrusion. There is no transverse maxillary discrepancy. Which orthodontic appliance is most appropriate to posture the mandible forwards during growth as the initial phase of treatment?

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Correct answer: C — Twin Block functional appliance

A Twin Block is a removable functional appliance that postures the mandible forwards and is commonly used in growing patients with a Class II relationship caused predominantly by mandibular retrusion. Correction reflects a combination of skeletal and dentoalveolar changes rather than purely skeletal growth modification. A fixed appliance alone primarily aligns and coordinates the dentition; it does not independently posture the mandible forwards. The passive removable appliance described would not provide functional mandibular advancement. Cervical-pull headgear applies extra-oral force mainly to the maxillary dentition and maxilla, while rapid maxillary expansion treats a transverse maxillary discrepancy, which is specifically absent here.

Reference: Pacha MM, Fleming PS, Shagmani M, Johal A. The skeletal and dental effects of Hanks Herbst versus twin block appliances for class II correction in growing patients: a randomized clinical trial. European Journal of Orthodontics. 2024;46(1):cjad065. https://pubmed.ncbi.nlm.nih.gov/37930325/