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x-ray of dental implantby Luis M. Benitez D.M.D

How long should we wait for the second tightening of the screw?

After delivering the prosthesis for a dental implant restoration, subsequent tightening of the prosthetic screw is a common clinical practice. This is because following the initial tightening of the screw, embedment relaxation occurs and results in loss of preload. After a waiting period, subsequent tightening can substantially alleviate this loss of preload. Because a majority of embedment relaxation occurs after the screw is first tightened, the loss of screw preload following the second tightening is mitigated.

It is a common practice to tighten the prosthetic screw and wait 5 minutes before tightening the screw to the recommended torque setting again. While 5 minutes is not an extensive waiting time it may be more or less time than is necessary. If the initial loss of preload happens in a shorter interval, then the screw can be tightened for a second time sooner, completing the prosthetic delivery with less interruption.

A simple study using different titanium prosthetic screws purchased directly from the implant manufacturers where the tightening interval was determined by measuring preload loss over time for various implant prosthesis components, showed the following

1. The elapsed time for greater than 90 % of the total preload loss to occur was no greater than 30 seconds in any instance.

2. In most instances, a second tightening of the screw regained most of the preload lost after the initial screw tightening.

This data suggest that a waiting period of 30 seconds is adequate before tightening the screw a second time. Please refer to graph

I hope this comes handy for our restorative team…

line chart Preload Loss Over First Minute
line chart Preload Change