American Board of Orthodontics (ABO) Practice Exam

What are common etiologies associated with the hyperdivergent phenotype?

1. Digit sucking and abnormal muscle function

2. Frequent thumb sucking and abnormal dental alignment

3. Inherited skeletal patterns and dental malocclusions

4. None of the above

The correct answer is: Digit sucking and abnormal muscle function

The hyperdivergent phenotype is characterized by increased vertical growth of the face, which often results in specific skeletal and dental characteristics. Among the common etiologies associated with this phenotype, digit sucking and abnormal muscle function play significant roles. Digit sucking can lead to changes in oral and facial musculature, affecting how the maxilla and mandible relate to each other. This prolonged habit can result in altered lip and tongue posture, which can contribute to an open bite or other vertical discrepancies that characterize the hyperdivergent profile. Moreover, abnormal muscle function can impact growth patterns and force distribution in the craniofacial region, leading to a tendency toward increased vertical dimension. While some other options mention factors like dental alignment and inherited patterns, they do not directly convey the influence of digit sucking and muscle function on the hyperdivergent phenotype. The presence of these factors demonstrates a clear relationship with the skeletal growth patterns associated with hyperdivergence.