Biomechanical evaluation of different fixation systems after Le Fort I osteotomy in polyurethane models of unilateral clefts

We compared the stability of three different titanium plate-and-screw fixation systems after Le Fort I osteotomy in polyurethane models of unilateral clefts. Thirty-six models were divided into 3 groups. In the first group, we adapted standard Plates 1 mm thick with 2.0 mm screws and placed them bilaterally on the zygomatic buttress and the piriform rim. In the second group, we did the same and added Plates 0.6 mm thick with 1.6 mm screws between the standard 2 mm miniplates on both sides. In the last group, we placed Plates 1.4 mm thick with 2.0 mm screws bilaterally on the maxillary zygomatic buttress and piriform rim. Each group was tested in the inferosuperior (IS) and anteroposterior (AP) directions with a servo-hydraulic testing unit. In the IS direction, displacement values were not significantly different up to 80 N, but between 80 and 210 N, those in the 2 × 1.4 mm group were better. In the AP direction, displacement values were not significantly different up to 40 N, but between 40 and 180 N, they were better in the standard with 1.6 × 0.6 mm group and the 2 × 1.4 mm group. When normal biting forces (90 - 260 N) in the postoperative period are considered, the greatest resistance to occlusal loads was seen in the 2 × 1.4 mm group. In the others, the biomechanical properties were better in the AP direction.