Re-torquing implant crowns or abutments?

Decreased preload of the prosthetic screw is a known phenomenon, especially after a period of loading. Whether this loss translates to a clinical requirement to retorque the screw is debatable, and may largely depend on the prosthetic connection, number of implants splinted together, etc. In any case, it is prudent to retorque prosthetic screws after a period of waiting, which in my practice is 1 minute. Here is a link to a fairly recent systematic review on this topic, where the authors mention the technique of retorquing the prosthetic screw after a period of loading towards the end of the article: http://www.medicinaoral.com/medoralfree01/aop/54374.pdf

Joseph has provided a reference to a good article. The message is really that internal fittings have less problems and probably do not need screws tightened after 1 week, albeit as Joseph said, I think most of us would check the screw tension a minute of so after initial tightening (just before we finalise the crown insertion – eg before we place a resin in the screw access cavity). Over the years, I found that internal fittings crowns did not have problems except with Astra EV implants - but this was solved when I decided to tension the screws 5 N more than recommended (problem solved immediately). I was so happy when internal fixture implants came on the market – for so many reasons.

I was once informed by an implant company that the way they define the maximum torque to be applied is that it should not be more than 25% of the failure load. Well, after having a few loosen (we call this becoming a "clicker") we started tightening the screws tighter than the recommended torque. That helped and we have less problems with "clickers" now. However, we do have some patients that seem able to loosen the retaining screw no matter how hard we may tighten it down. This is almost invariably in mandibular first molar situations.

maybe with older external hex etc....but with today's internal connections and torque wrenches, once at placement, and then again 1 min after is sufficient. IMO -implant direct rep

There is a lot of nonsense about screw mechanics in dentistry- the number 1 prosthetic complication in single crown restorations. I have been studying this in the form of a survey conduct on nearly 400 dentists. Few realize how the screw actually works, very few can explain how Hooke's law relates to preload. None know about the ISO (international Standard Organization) 6789 applicable to all torque wrenches- that states torque devices must be calibrated at least yearly, more frequently if exposed or stored in extreme conditions (Autoclaving !) No one calibrates torque devices that is a major reason screw loosening occurs- the device is mis-used and mis-read. Storage of the device is an issue, cleaning correctly and maintenance- even with the beam wrench is problematic. Clinicians should understand concepts of mechanical engineering- these have already been worked out decades ago - we make things up - like wait 10 minutes between retorque (or a minute !!) no science in those concepts- Look at how racing car wheels are tightened- less than 5 seconds- you don't see the mechanics wait a minute and retighten ! Interestingly- Costco tires calibrates their wrenches every day and logs- we don't- they are more mechanically minded than we are- very poor !