A 52-year-old man presents with progressive jaw protrusion and widening of tooth spacing over the past 8 years. On examination, the structure marked **A** in the diagram is prominently enlarged. He also reports that his wedding ring and shoes no longer fit. Laboratory investigations reveal elevated IGF-1 levels and failure of growth hormone suppression on oral glucose tolerance test. MRI pituitary shows a 1.8 cm sellar mass. Which of the following best explains the mandibular changes observed at **A**?