Group 2 (Post-Radiation) Subjects who were previously treated with radiotherapy with or without chemotherapy (induction or concurrent). Treatment will have included the following: 1) unilateral maximum mandible dose of ≥ 60 Gy and a gradient of dose across the mandible of ≥ 20 Gy, 2) oncological cure and now in disease surveillance; and 3) no clinically diagnosed ORN at the time of enrollment.