Comparison of screw and plate osteosynthesis in advancement genioplasty: a finite element analysis study.

PURPOSE

The purpose of this study was to evaluate the distribution of stresses in screw and plate fixation systems during simulated advancement genioplasty using finite element analysis.

MATERIALS AND METHODS

A cone-beam computed tomography image of a patient was used to create three-dimensional virtual models of mandibular bone. Chin advancement of 8 mm was simulated following a horizontal osteotomy of the chin in a computer-aided design program. The distal segment was stabilized with two titanium mini-screws placed bilaterally in the first model and a single 4-hole titanium pre-bent chin plate placed centrally in the second model. The plate was fixed with four mini-screws, two in the proximal and two in the distal segment. All fixative appliances were submitted to 15 N force applied backwards to the lingual surface of the chin parallel to the occlusal plane and 7 N force applied upwards to the buccal surface of the chin perpendicular to the occlusal plane. The distributions of von Mises stresses and deformations in bone and titanium materials were evaluated.

RESULTS

In the screw fixation system (22.52 MPa) higher stress values were observed compared to the plate fixation system (13.71 MPa). The deformation value was higher for the screw fixation system (0.021 mm) than the plate fixation system (0.0007 mm).

CONCLUSION

In advancement genioplasty, fixation with a single pre-bent centrally placed chin plate showed slightly better stabilization than fixation with two bilaterally placed bicortical screws. The stress values were within the physical strength limits of bone and titanium for both systems.