Evaluation of Mandibular Fixation Techniques Using Monocortical Plates After Mandibular Setback Surgery

Area of Science:

• Orthognathic Surgery
• Maxillofacial Reconstruction
• Skeletal Class III Correction

Background:

• Skeletal Class III malocclusion often requires orthognathic surgery, specifically sagittal split ramus osteotomy (SSRO), to correct jaw discrepancies.
• Mandibular fixation techniques are crucial for stabilizing bone segments post-SSRO, influencing surgical outcomes and long-term stability.
• Understanding the biomechanical effects of different fixation methods is essential for optimizing patient results and minimizing complications.

Purpose of the Study:

• To compare the effects of three different monocortical plate fixation techniques on mandibular segment stability following SSRO in skeletal Class III patients.
• To evaluate the rotational stability of the proximal segment and the positional changes of the pogonion (chin) based on fixation methods.

Main Methods:

• A prospective study involving 93 skeletal Class III patients undergoing SSRO.
• Patients were divided into three groups based on fixation: Group 1 (4-hole miniplate, 1 proximal/2 distal screws), Group 2 (4-hole miniplate, 4 screws), Group 3 (sliding plate, 2 proximal/1 distal screws).
• Cone-beam computed tomography (CBCT) scans were analyzed at immediate postoperative, 6 months, and 12 months to assess segment rotation (yaw, roll, pitch) and pogonion displacement (horizontal, vertical).

Main Results:

• Group 1 demonstrated significantly greater counterclockwise rotation of the proximal segment at 6 and 12 months postoperatively compared to Groups 2 and 3 (p < 0.05).
• Group 1 also showed significantly less anterior and superior displacement of the pogonion at 12 months (p < 0.01).
• The findings suggest that the three-screw fixation in Group 1 may provide a fulcrum effect, limiting undesirable clockwise rotation of the distal segment.

Conclusions:

• The fixation technique using a four-hole miniplate with one proximal and two distal screws (three-screw fixation) appears to offer superior rotational stability for the proximal segment after SSRO in skeletal Class III patients.
• This fixation method resulted in more favorable pogonion positioning, indicating better control over mandibular repositioning.
• The study highlights the importance of screw placement and number in achieving stable mandibular fixation and predictable outcomes in orthognathic surgery.