Mechanical Stability Of Lefort I Osteotomy With Mortise-Tenon Fixation

To evaluate the mechanical stability of maxillary advancement after LeFort I osteotomy using absorbable plates with tenon-and-mortise structures. Three finite element models were developed: Model 1 (absorbable plates), Model 2 (absorbable plates with tenon-and-mortise), and Model 3 (titanium plates). Simulated occlusal forces were applied, and displacements of nasal-palatine (NP) and posterior nasal spine (PNS) points were analyzed. Clinical data from 45 patients (21±3 years) treated at the Stomatology Hospital of China Medical University (2017-2023) were collected, with 15 patients in each fixation group. Preoperative, 3-day, and 6-month CT scans were used to measure NP and PNS distances to horizontal, sagittal, and coronal planes. Results showed that Model 2 had lower NP (0.4/0.02 mm) and PNS (0.5/0.015 mm) displacements compared to Model 1 (NP: 0.6/0.12 mm; PNS: 0.5/0.11 mm) and Model 3 (NP: 0.33/0.055 mm; PNS: 0.16/0.1 mm). Mises stress was lower in Model 2 than Model 1. Clinically, Model 2 and Model 3 showed no significant displacement differences (P>0.05), while Model 1 had significant vertical and anterior-posterior displacement (P<0.05). Tenon-and-mortise-assisted absorbable plates provide comparable stability to titanium plates, outperforming absorbable plates alone, especially under posterior tooth loading. This method offers a viable alternative to titanium fixation.