Two-piece versus single-piece patient-specific titanium subperiosteal implants in atrophied edentulous mandibles: A finite element analysis

Abstract

Statement of problem: Subperiosteal implants (SPIs) are considered a viable treatment option in patients with highly resorbed ridges if extensive bone grafting or other more invasive procedures are not indicated. Traditionally, SPIs were designed in a single-piece fashion, while two-piece SPIs were introduced recently. However, there are no studies in the current dental literature that compared between the two designs.

Purpose: This three dimensional finite element analysis (3D FEA) was conducted to compare the differences in the biomechanical behavior of two SPI designs: the single-piece and the two-piece SPI framework design.

Materials and methods: The study simulated a clinical situation of 2 interforaminal SPI frameworks; a single-piece titanium SPI framework placed on one side of the mandible versus a two-piece titanium SPI framework placed on the contralateral side. The frameworks were restored with a cement-retained SPI framework-supported prosthesis with a shortened dental arch on a total of 4 upstanding abutments, and opposed by a maxillary removable tissue-supported complete denture. The 3D surface model was produced from a multi-slice computed tomographic scan of a patient with an edentulous mandible. The study involved two simulations with unilateral oblique force of 50 N being applied on the prosthesis at the buccal inclines of the lingual cusp of the mandibular second premolar at an angle of 30°. Simulation 1 represented oblique right-side loading on the working side that harbored the single-piece SPI framework, while simulation 2 represented oblique left-side loading on the working side that harbored the two-piece SPI framework. Outcomes included peri-implant stresses, von Mises stress in frameworks, fixation screws, and overlying prosthesis as well as the total deformation of fixation screws.

Results: Stress values at the peri-implant bone, on fixation screws as well as the total deformation of fixation screws were fairly comparable for both SPI framework designs. However, the von Mises stress values recorded for the framework in simulation 2 (left loaded side corresponding to the two-piece SPI framework side) was more than double the von Mises stress values recorded for the framework in simulation 1 (right loaded side corresponding to the single-piece SPI framework side), 150.09 MPa and 60.74 MPa, respectively.

Conclusion: Within the limitations of the current study, and from a biomechanical perspective, stress values in both designs were comparable except for the frameworks, where the single-piece SPI framework design demonstrated superiority over the two-piece SPI framework design.