Single narrow-diameter implant-supported dual-unit cantilever restorations for consecutive missing teeth in the anterior mandible: a 3D finite element analysis

Objective·To evaluate the applicability of dual-unit cantilever restorations supported by a single narrow-diameter implant for consecutive missing teeth in the anterior mandibular region.Methods·A simplified mandibular anterior jaw model and a dual-unit cantilever model supported by a single narrow-diameter implant were constructed. The dimensions of the mandibular anterior bone block were set to 20 mm (length), 5 mm (width), and 15 mm (height). The narrow-diameter implant used was the Axiom 2.8 two-stage implant, 2.8 mm×10 mm, paired with a 2.5 mm straight abutment. Based on calculations, the edentulous gap ranged from 5.8 mm to 11.6 mm, leading to the creation of seven crown models with mesiodistal widths of 5.8, 6.8, 7.8, 8.8, 9.8, 10.8, and 11.8 mm. The implant, crowns, and jaw model were assembled using Siemens Nx 12.0 software, and the data were imported into Ansys Workbench 18.0 for finite element analysis. A vertical load of 100 N and a 30° oblique load were applied to simulate occlusal forces. The Von-Mises stress on the implants, as well as the maximum compressive and tensile stresses in the cortical bone and the maximum tensile stress in the cancellous bone, was analyzed to investigate stress distribution under varying cantilever lengths.Results·The implant neck region exhibited the highest stress concentration. As the cantilever length increased, the peak Von-Mises stress on the implants, the maximum tensile stress in the cortical and cancellous bones, and the maximum compressive stress in the cortical bones all increased progressively. However, all stress values remained within physiological limits. The peak Von-Mises stress ranged from 141.52 MPa to 707.17 MPa, below the implant′s ultimate tensile strength of 930 MPa. The maximum tensile stress in the cortical bones (with a peak of 60.82 MPa in the 11.8 mm group) was below the cortical bone′s tensile strength limit of 100‒130 MPa. The maximum compressive stress in the cortical bone (with an absolute maximum value of 129.39 MPa in the 11.8 mm group) was below the cortical bone′s compressive strength limit of 170 to 190 MPa (absolute values). The maximum tensile stress in the cancellous bone ranged from 0.84 MPa to 4.70 MPa, which was below or close to its ultimate tensile strength of 2‒5 MPa.Conclusion·Dual-unit cantilever restorations supported by a single narrow-diameter implant may represent a viable treatment option for consecutive missing teeth in the anterior mandibular region.