Effects of abutment geometry, cement type and amount on cement extrusion in cement‑retained implant‑supported restorations: an in vitro study

This in vitro study systematically evaluated the combined effects of abutment geometry, cement type, and cement amount on cervical cement extrusion in cement-retained implant-supported restorations. A total of 40 abutments (20 cylindrical, 20 tapered) and zirconia crowns were allocated to eight groups ( n = 5 per group) according to a 2 × 2 × 2 factorial design. The factors were abutment geometry (cylindrical vs. tapered), cement type (resin‑modified glass ionomer vs. self‑adhesive resin cement), and cement amount (standard vs. excess). After cementation, the percentage of cement-covered areas was quantified using standardized digital images, and extruded cement weight was determined gravimetrically before and after cleaning procedures. Data was analyzed using three-way ANOVA and post hoc comparisons (α = 0.05). Abutment geometry and cement amount significantly affected both extruded cement weight and cement-covered area ( P < 0.001), whereas cement type showed no significant main effect. Excessive cement applications markedly increased extrusion, while cylindrical abutments exhibited lower cement extrusion than tapered abutments. A significant interaction between abutment geometry and cement amount was observed for extruded cement weight ( P = 0.022), indicating that the effect of cement amount differed between the two abutment geometries. Within the limitations of this in vitro study, cement amount had the greatest effect on cement extrusion outcomes, followed by abutment geometry, whereas cement type showed no significant main effect. Controlling cement amount and considering abutment geometry may represent potential strategies for reducing cement extrusion under controlled conditions.