Effect of Access Channel Sealing and Superstructure Material on Abutment-Implant Screw Stability After Cyclic...

Screw loosening remains a common mechanical complication in implant-supported restorations; however, the combined effect of sealing and superstructure materials on abutment screw stability warrants further investigation.

This study evaluated the influence of access channel sealing material and superstructure material on abutment-implant screw stability after thermomechanical cyclic loading. Forty-eight Straumann analog-abutment assemblies restored with monolithic zirconia or resin nano-ceramic (Cerasmart) crowns were assigned to two sealing protocols: Polytetrafluoroethylene (PTFE) + composite or polyvinyl siloxane (PVS) putty (n = 12). After 750,000 off-axis cycles, reverse torque values (RTV) were analyzed using two-way analysis of variance (ANOVA) and Tukey's HSD, with effect sizes calculated (α = 0.05).

A significant interaction between restorative material and sealing protocol was observed (p = 0.0170; η² = 0.116). Superstructure material showed no significant influence on RTV (p = 0.8368), whereas sealing protocol had a significant main effect (p = 0.0499). RTVs were highest for zirconia + PVS putty (36.33 ± 4.53 Ncm) and lowest for zirconia + PTFE (29.32 ± 6.30 Ncm), while the Cerasmart groups showed intermediate values. Post hoc analysis confirmed higher RTV for zirconia + PVS compared with zirconia + PTFE (p = 0.0138).

Access channel sealing materials showed a material-dependent influence on abutment screw stability. Silicone-based sealing improved torque maintenance in zirconia, indicating that rigid restorative materials may be more sensitive to sealing material selection. In contrast, Cerasmart showed comparable RTV regardless of sealing protocol, suggesting that resilient restorative materials may reduce the influence of sealing on preload maintenance.