Retention performance of conometric concept versus cement-retained implant restorations: an in vitro study

A novel conometric abutment system has been developed to retain implant-supported restorations through frictional engagement, eliminating the need for screws or intraoral cementation. This study aimed to evaluate the retentive performance of this conometric system in comparison with a cement-retained restoration and to investigate the influence of thermocycling aging and abutment diameter on retention force. A total of 96 dental laboratory analogues with corresponding abutments and caps were used. Specimens were allocated into four groups according to retention mechanism (conometric Cm or glass ionomer cement GIC) and abutment diameter (3.3–4.5 mm). Caps were either positioned using a dedicated fixation tool (Cm) or definitively cemented with glass ionomer cement (GIC). Half of the specimens were tested immediately, while the remaining half underwent thermocycling (5–55 °C, 10,000 cycles). Retention force was determined using a universal testing machine in a pull-out test. Data were analyzed using three-way ANOVA followed by Tukey post hoc tests to assess the effects of retention system, abutment diameter, and aging condition. Immediate retention forces were significantly higher for the Cm group (124.81 ± 66.42 N) compared with the GIC group (60.30 ± 27.39 N). Thermocycling significantly increased retention in the Cm group (185.40 ± 60.94 N) while reducing retention in the GIC group (48.00 ± 24.32 N). Abutments with a smaller diameter (3.3 mm) exhibited higher retention forces than wider abutments (4.5 mm). The conometric abutment system demonstrated favorable immediate and long-term retention, supporting its potential as an alternative to cement-retained single-unit implant restorations.