How does cement choice affect screw stability in implant-supported restorations with different abutment angulations? An in vitro study

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OBJECTIVE: To investigate the influence of cement type on the abutment-screw stability of single implant-supported restorations with different abutment angulations. MATERIALS AND METHODS: Fifty CAD/CAM implant-supported monolithic zirconia crowns simulating an upper premolar were divided into four groups (n = 10) according to the type of retention (SC: screwed, Cem: cemented), cement (TC: temporary, DC: definitve cement) and abutment angulation (SA: straight, AA: angulated abutment). Temp Bond NE and a self-adhesive resin cement (RelyX) were used for temporary and definitive cementation, respectively. All samples were subjected to dynamic loading with thermocycling in a chewing simulator (6336 cycles, 5 -55 °C, 98 N, 1.2 million cycles). Pre- and post-loading reverse torque values (RTVs) were measured using an electronic screwdriver, and the reverse torque differences (RTD) were thereafter calculated. The Kruskal-Wallis and Mann-Whitney tests were used for the statistical analysis. RESULTS: Among test groups, the lowest RTD was seen in group Cem_AA_DC (2.12 ± 2.06Ncm), whereas the highest was found in group Cem_SA_TC (3.16 ± 0.18 Ncm). Statistically significant differences were seen between the screwed (SC_SA) and all cemented groups except Cem_SA_TC (p = 0.089). Among the cemented groups, no significant difference was observed between straight and angulated abutments, nor between temporary and permanent cement types. CONCLUSION: Definitive cementation, particularly in angulated abutments, was associated with higher torque retention compared to screw-retained or temporary cemented restorations. CLINICAL IMPLICATION: Definitive cementation may contribute to improved screw stability of implant restorations, especially in angulated abutments, compared with temporary or screw-retained designs, highlighting the potential impact of retention method and cement choice on long-term mechanical performance.

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