A comparative analysis of efficacy of torque limiting devices provided by different dental implant manufacturers

Abutment screw loosening is a frequently reported prosthetic complication that has been linked to the achieved preload, wear of the components of the connection and micromotions or deformation under occlusal load. Inadequate fit and tightness of the implant-abutment interface can cause fracture or the creation of a gap with predisposition to its bacterial colonization. The aim of this research was to assess the accuracy of three mechanical torque-limiting devices provided by different dental implant manufacturers. This study was designed as an in vitro model. Torque wrenches effective values and the evaluation of fixture-abutment microgap were evaluated. The actual torque of the wrenches was analyzed by setting five unused torque limiting devices for each manufacturer at 15, 20 and 25 Ncm; each wrench performed twenty measurements at 15, 20 and 25 Ncm respectively. For gap analysis, three groups of fixtures (each one of twenty implants with related abutments), from three different companies, were examined. Each group was divided into two equal subgroups (ten implants with related abutments), which were tightened using a torque of 20 and 25 Ncm respectively. The study showed that all wrenches examined exert a torque lower than the one set and indicated on the wrench. The error range varies from a minimum of 11% (seen on A wrench set to a value of 20 Ncm) to a maximum of 29.3% (seen on B wrench set to a value of 15 Ncm). All the examined wrenches were able to assure, at 25Ncm, the absence of microgap at the fixture-abutment interface. The accuracy of the mechanical limiting torque devices differed from different manufacturers. The clinician should know the range of wrenches imprecision of the own dental implant system to applicate more precise tightening force for prosthetic screw to prevent mechanical complications.