Influence of Two Types of Connections in Driver-Retention Screw Assembly

Rehabilitation with implant-supported prostheses has reached high success rates. However, mechanical failures are still reported, mainly in retention screws of abutments in single implant-supported crowns; which is designed to be the weakest structure and the first component to fail under overloading. In this sense, the aim of this in vitro study was to evaluate the influence of different joint designs (square or hexagonal) on resistance to deformation of driver-retention screw assembly of 3 commercial brands (Neodent, Singular, and Sin). A total of 42 retention screws from 3 commercial brands were used. The samples were divided into 2 joint groups, square (SQU) and hexagonal (HEX), and separated by commercial brands. Several components (implants and abutments) with standard platform (4.1 mm in diameter) were used. The resistance to deformation of the driver-retention screw assembly was measured using an accurate digital torque wrench for all commercial brands (Neodent [NEO], Singular [SGL], and Sin [SIN]) and joint designs (square or hexagonal). It was found no statistically significant difference (P <0.05) among the brands evaluated. On the other hand, square screws showed higher resistance to torsion than hexagonal screws; regardless the commercial brand.