The aim of this prospective study is to analyze the postoperative paresthesias experienced in patients who undergo bilateral sagittal split osteotomies (BSSO) using an ultrasonic saw, versus a reciprocating saw. Patients included in the study are ages 15-45 scheduled to undergo BSSO surgery at the University of California, San Francisco. One side of the patient's mandible will be instrumented with either the Stryker Sonopet ultrasonic saw or traditional reciprocating saw, while the other side will receive the remaining intervention (determined via randomization on the day of surgery). Patient paresthesias will then be analyzed on each side for 3 months postoperatively (at postoperative days: 1, 7, 14, 28, and 84). Sensory examinations will be carried out by blinded examiners using von Frey hairs and two point discrimination testing. Patients will also subjectively rate their sensation on each side. The results will then be analyzed to determine if patient paresthesias, including the severity and duration, differed depending on which instrument was used, the ultrasonic or reciprocating saw.