What is the cause of the functional form of malocclusion Class III by Angle?

What is the cause of the functional form of malocclusion Class III by Angle?

• A. Excessive growth of mandible
• B. Excessive growth of maxilla
• C. Maxillary hypoplasia
• D. Forward mandibular shift

Answer: (D)

At the heart of a functional Class III malocclusion is a forward shift of the mandible during closure, caused by occlusal interferences. In these cases, the jaw moves forward to achieve maximum intercuspation, so the patient appears Class III in the habitual bite even though the underlying skeletal base may be normal or not severely prognathic. This makes the malocclusion “functional” rather than true skeletal; the mandible isn’t permanently positioned forward when the jaw is in centric relation. That forward mandibular shift is what creates the reversible, functional Class III presentation. If the occlusion were free of interferences and the mandible could seat in centric relation, the skeletal relationship wouldn’t be a fixed Class III. In contrast, excessive growth of the mandible or maxillary hypoplasia would produce a true skeletal discrepancy (mandibular prognathism or maxillary deficiency, respectively) visible even without any functional shift, not the transient, occlusion-driven shift seen in the functional form. Excessive maxillary growth alone would alter the relationship differently and wouldn’t explain a jaw that only shifts forward during closure.

At the heart of a functional Class III malocclusion is a forward shift of the mandible during closure, caused by occlusal interferences. In these cases, the jaw moves forward to achieve maximum intercuspation, so the patient appears Class III in the habitual bite even though the underlying skeletal base may be normal or not severely prognathic. This makes the malocclusion “functional” rather than true skeletal; the mandible isn’t permanently positioned forward when the jaw is in centric relation.

That forward mandibular shift is what creates the reversible, functional Class III presentation. If the occlusion were free of interferences and the mandible could seat in centric relation, the skeletal relationship wouldn’t be a fixed Class III.

In contrast, excessive growth of the mandible or maxillary hypoplasia would produce a true skeletal discrepancy (mandibular prognathism or maxillary deficiency, respectively) visible even without any functional shift, not the transient, occlusion-driven shift seen in the functional form. Excessive maxillary growth alone would alter the relationship differently and wouldn’t explain a jaw that only shifts forward during closure.