Tensile strength of Co-Cr and Zr substructures on titanium abutments with different geometries

This study aimed to evaluate the effects of different abutment geometries, abutment materials (Cobalt–Chromium and Zirconium), and cement types on the tensile strength of cement-retained implant-supported restorations in vitro. A total of 240 BioHorizons implant analogues (5.7 mm diameter) were used and initially divided into two groups based on the material: Cobalt–Chromium (Co–Cr) and Zirconium (Zr) (n = 120). Each material group was further divided into four subgroups according to abutment geometry (n = 30): Group C (no preparation), Group P (one wall), Group A (adjacent two walls), and Group O (opposite two walls). Subsequently, each geometry subgroup was divided into three subgroups (n = 10) according to the cement type: adhesive resin cement (ARC), and self-adhesive resin cement (SARC), resin-modified glass ionomer cement (RMGIC). Tests were carried out using a universal testing machine with a 0.5 mm/min crosshead speed. Two-way Anova statistical test was performed with post-hoc Tukey test, with 0.05 significance. In the zirconia groups, Group O showed the highest retention (ARC: 695.27 ± 201.67 N; SARC: 507.01 ± 80.00 N; RMGIC: 389.42 ± 139.60 N), with significant pairwise differences between ARC–SARC, ARC–RMGIC, and SARC–RMGIC. In the metal groups, ARC achieved the highest values, particularly in Group P (928.27 ± 167.81 N) and Group C (822.15 ± 295.65 N). RMGIC yielded the lowest retention in most geometries, differing significantly from ARC in all geometries and from SARC in Groups P and C. Abutment geometry had minimal influence on ARC and SARC in metal substructures (p > 0.05 for most comparisons) but significantly affected RMGIC retention (Group O vs. P, C ). Retention of implant-supported restorations is strongly influenced by abutment geometry. Combining favorable geometry with high-performance cements in clinical practice is important.