Torsion resistance of the Ball Head System screw and screwdriver for angled screw channels on implant prosthetics.

The primary objective of this study was to determine the torsion resistance of the Ball Head System (BHS) screw and screwdriver set at 0o, 20o and 30o angulations. Secondarily, to compare the BHS set with the 1.3 mm hexagonal screwdriver system (HexS) at 20o and analyze the condition of the BHS after 10 and 30 iterations with 30 N·cm torque at 30o angulation. A workbench made from type 4 plaster with 6 steel implant replicas (external hexagon 4.1 mm) inserted at 0o, 20o and 30o angulation was designed. An analogical torque meter was used. The deformations produced on the whole set were examined by Field Emission Scanning Electron Microscopy. A descriptive analysis was performed. The maximum torque performance for BHS at 30o angulation was 54±12 N·cm. Most screws could be removed despite the deformations produced. At 20o angulation, the BHS set achieved an average torque resistance of 67±12 N·cm, while the HexS failed at 45±2 N·cm. Although the iterations performed at 30 N·cm torque and 20o angulation produced some deformations on BHS sets, these could be tightened and unscrewed. The BHS allows tightening at a torque of up to 54 N·cm. Under the same conditions, BHS showed more torque resistance than HexS. Deformation of BHS sets was directly related to the number of iterations.