Abstract
BACKGROUND: 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. METHODS: 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. RESULTS: 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 ). CONCLUSIONS: Retention of implant-supported restorations is strongly influenced by abutment geometry. Combining favorable geometry with high-performance cements in clinical practice is important.