The investigators performed this study to compare the rigidity outcomes for minimally invasive fixation of edentulous mandibular parasymphyseal fractures without flap creation using Herbert screws with a dynamic navigation system and the conventional two-plate method.

The investigators implemented an in-vitro study design, and 20 polyurethane edentulous mandibular models covered with flexible plastic to simulate the gingiva were used. Parasymphyseal fractures were created in all models using a reciprocal saw. In the study group, the fracture segments in each model were planned to be fixed using two 30-mm Herbert screws. The Herbert screws were placed using a screwdriver with the dynamic navigation system guiding the process. In the control group, to simulate open reduction, the fracture fragments were fixed using two 4-hole straight titanium plates and 6-mm titanium screws. All mandibular models on the prepared platform were attached to the biomechanical testing machine. They were subjected to a continuous linear compression until plastic deformation occurred. Displacement resistance was measured once for every model when the displacement reached 1, 3, 5, 10, and 15 mm. Furthermore, the maximum breaking forces that the models could withstand before deformation were measured. Data were analyzed using independent samples t-test. A value of p < .05 was considered statistically significant.

Manual examination of the models did not reveal any mobility between the fragments. In all evaluated displacement steps, the models fixed using Herbert screws showed significantly higher resistance to mechanical loading compared to the models fixed using parallel miniplates.

In present study, parasymphyseal fracture of edentulous mandible models were fixed successfully using Herbert screws with the dynamic navigation system. The results of this study may encourage future clinical studies.