Influence of different customized abutment materials on stress distribution of different internal implant-abutment connections: finite element analysis.

backgroundLimited research evaluates how the type of implant-abutment connection and the material of the abutment together affect the biomechanical behavior of load transfer within both the implant components and the surrounding bone under axial and oblique loading conditions. This 3-dimensional (3D) finite element analysis (FEA) study aimed to provide biomechanical insights to assist clinicians in choosing optimal connection designs and abutment materials, enhancing implant longevity and clinical outcomes.

methodsTwo internal implant-abutment connections were modeled in 3D: model (S), which is a star-shaped tube-in-tube design, and model (H), which is a Morse taper combined with an internal hex, both intended to support a mandibular first molar crown and its associated bone geometry. Four abutment materials (Titanium grade V/Ti, Co-Cr, soft-milled Co-Cr-Mo/Co-Cr-S, and zirconia/Zr) were examined using both connection designs. Each crown was subjected to two loading protocols: (1) 200 N vertically was applied at six occlusal points, and (2) 100 N obliquely (at 45º) was applied to three occlusal points on the buccal bevel of the buccal cusp. FEA was performed to analyze the maximum and minimum principal stresses and strains on the peri-implant bone, as well as the von Mises stresses on the implants, abutments, screws, and crowns.

resultsPrincipal stresses and strains were predominantly concentrated in the crestal cortical bone. Under axial loading, stress values were similar across connection types. The highest stress was observed in the H (Zr) model (15.683 MPa) and the lowest in S (Ti) (14.265 MPa). Oblique loading caused higher compressive stresses, peaking at 99.06 MPa in the H (Co-Cr) model. In cancellous bone, stresses were lower, ranging from 0.12888 MPa for H (Ti) to 0.21535 MPa for S (Zr). The highest cortical strain was observed in S (Co-Cr) under oblique loading conditions, measuring 6700 με. Conversely, all models exhibited reduced cancellous elastic strain values, with the maximum strain recorded at 1200.0 με in the S (Co-Cr) axially and 980.0 με in the S (Co-Cr) obliquely. The von Mises stress was localized at the implant and abutment necks, with peak implant stress attaining 135.0 MPa in the S (Co-Cr) model under oblique loading. Titanium abutments demonstrated the lowest stress values consistently across various loading conditions. All models exhibited minimal directional screw deformation (3.897 µm axial; 1.257 µm oblique), demonstrating mechanical stability.

conclusionsStar-shaped tube-in-tube and hybrid Morse taper with internal hex connections showed similar stress patterns, with values below the titanium alloy's yield strength and safe bone stress levels. Oblique loading, however, produced cortical strains above the safe limit. Zirconia, Co-Cr, and soft-milled Co-Cr-Mo abutments had moderate stress distribution, while titanium showed the most favorable profile. Both connections caused minimal screw deformation, suggesting low loosening risk.