A practical approach to determining screw preload in dental implant systems

A practical and novel technique used both in testing and in practice when tightening dental implant screw systems is described for determining the preload implant screw systems, which differs from traditional tightening procedures that are based solely on the application of a predetermined manufacturer specified torque value. Preload is the critical quantity for a reliable joint: about 90% of tightening torque goes into overcoming friction and the remaining amount, approximately 10%, goes into preload. Because of the heavy dependence of torque on friction, the actual preload achieved is subject to large variability of up ±35%, depending on surface conditions (dry, wet, or contaminated). Current methods of testing for preload require complex equipment such as load cells, strain gauges, or finite element analysis. This practical technique integrates tightening torque with removal torque value measurements and screw geometry to determine preload. This information subtracts out the friction components, thereby accounting for differences in surface conditions and reducing the need for multiple test conditions.