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

Abstract 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 CemAADC (2. 12 ± 2. 06Ncm), whereas the highest was found in group CemSATC (3. 16 ± 0. 18 Ncm). Statistically significant differences were seen between the screwed (SCSA) and all cemented groups except CemSATC (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.