Which appliance is used to influence jaw position by promoting mandibular advancement?

• A. twinblock appliance
• B. adams crib
• C. roberts retractor
• D. luxator

Answer: (A)

Functional appliances influence jaw relationships by guiding the mandible forward during growth. They work by holding the lower jaw in a forward position so the muscles and joints adapt and skeletal changes can occur, helping to correct a retrusive mandible and reduce overjet.

The twinblock achieves this with two acrylic blocks on the upper and lower arches that interlock. When the patient bites, the blocks position the mandible forward and maintain that forward posture during function. This forward positioning encourages forward growth of the mandible and remodeling at the temporomandibular joints, which is especially beneficial in growing patients with Class II malocclusion. Its design also allows the mandible to move through a functional range, making it effective and relatively comfortable, which supports better compliance.

Adams crib is a habit-breaking appliance used to stop thumbsucking or tongue thrusts, not to advance the jaw. Roberts retractor and luxator are instruments used for soft-tissue retraction and tooth extraction, respectively, and do not influence jaw position.