Few studies have demonstrated the reliability of biodegradable osteosynthesis systems in orthognathic surgery; however, studies on the use of biodegradable osteosynthesis systems after mandibular osteotomy, including sagittal split ramus osteotomy (SSRO), are limited. This pilot study aimed to compare the safety and skeletal stability after segmental fixation using curved titanium and box-type biodegradable systems in SSRO for mandibular prognathism. Patients who underwent SSRO for correction of mandibular protrusion with malocclusion between September 2024 and March 2025 were included. After conventional SSRO, the bilateral segments were fixed using curved 6-hole titanium plates (Ti group) or 6-hole box-type biodegradable plates (Bi group). Lateral and frontal cephalograms and computed tomography images were obtained before (T0), 5±2 days after (T1), and 6±1 months after surgery (T2). In the Ti group, although the absolute change in the ramus plane and gonial angles from T1 to T2 was -2.3±5.1 and 3.6±7.4 degrees, respectively, no significant change was observed in any of the measured angles. In contrast, in the Bi group, significant changes from T1 to T2 were observed in the mandibular plane (4.8±2.3 degrees), ramus plane (-5.7±4.0 degrees), and gonial angles (8.8±4.2 degrees). The changes in the vertical and horizontal positions of point B, menton and pogonion were not significantly different between the 2 groups. The results of this pilot study with a small sample size suggested that in patients undergoing SSRO, bone segmental fixation using 6-hole box-type biodegradable plates may provide acceptable short-term skeletal stability and safety. Since definitive comparisons require larger prospective studies, further prospective studies with larger sample sizes are warranted.