The evaluation of pathologic fracture risk and residual bone height in unicortical and bicortical mandibular corpus defects: A 3D finite analysis

Objective

Mandibular bone defects are a common problem and difficult to manage. A defected area mostly left to heal spontaneously. It doesn’t have a definite protocol in the literature, when the area will be left to heal spontaneously or when supported with materials such as plates, screws, grafts, especially in intermediate-sized defects. In this study, it was aimed to determine by examining the areas where the stresses due to chewing forces are concentrated on the mandible bone and the risk of fracture in intermediate size unicortical and bicortical defects.

Material and Methods

The all defect models which was the residual bone heights were 6, 8, 10 mm in mandibular corpus region were created. Two different loading scenarios were applied anterior and defected premolar side. Von Mises, Pmax and Pmin stresses in models were evaluated by three-dimensional finite element analysis method.

Results

The study found higher stress accumulation on the buccal anterior side of defects in both unicortical and bicortical models, with the most stress concentrated at the buccal corners. Under Loading 1, bicortical defects with 10 mm residual bone height showed slightly higher stress accumulations than unicortical defects, while bicortical defects with 8 and 6 mm residual bone height exhibited significantly higher stress values. Under Loading 2, stress accumulations in bicortical defects were higher than in unicortical defects, with bicortical defects at 6 mm residual bone height showing almost double the stress values. Pmax stress values were higher in bicortical defects under both loadings, especially when the residual bone height decreased. Pmin stress values were comparable in unicortical defects but were higher in bicortical defects, particularly at 6 mm residual bone height, under both loading conditions.

Conclusion

This study was presented that mandibular resistance decreases significantly when residual bone height is less than 10 mm for bicortical defects and less than 8 mm at unicortical defects. In these conditions it may need supported with materials to prevent fractures. However, in vivo and in vitro studies are necessary for definitive conclusions.