Conical hybrid connection was used in this study as it was proven that the conical hybrid demonstrated the best stress distribution [20]. This connection has a conical union between the implant fixture and the abutment. In the conical abutment, lateral force is resisted by the taper design of the Morse taper connection. Thus, the stress concentration is resisted by the side-wall contact surface of its taper design. This stress concentration increases at the apical end of the side-wall contact surface where the implant fixture is thicker. This thickness might provide more resistance to the force, especially the off-axis loading force (as in case of angled abutment). Thus, in abutments with conical hybrid connection design, the screw is not the only source of resistance to loading force, as it is in abutments with an internal hexagonal design [21, 22].

In this study, abutment screws were tightened to 30 Ncm according to the manufacturer’s instructions with digital torque gauge. Application of the optimum torque to the implant–abutment complex is critical for long-term successful prosthetic implant restoration. Applied torque develops a force within the screw called preload [23].

Ten-minute interval was left after the first torque application, and all screws were retightened to the same tightening torque (30 Ncm) with the same digital torque gauge to compensate for the preload loss due to settling effect of the screw thus ensure achieving optimal preload as only 10% of the initial torque is transformed into preload, where the remaining 90% is used to overcome the friction between the surface irregularities [23].

The results of this study indicated that there is some torque loss after applying two insertion torques with a 10-min interval before any loading as RTVs were less than 30 Ncm. This finding matches previous studies that reported initial torque loss after 2–10 min [4, 9, 10]. Although there was an increase in %RTL before loading in every group, loosening of screws could not be detected clinically. This may indicate that the remaining tightening torque would serve clinically for a longer period.