Nobel Replace 'loosening'

[thewhitelab]

I have a client who uses Nobel Replace and unfortunately on a few cases we have had screw loosening? i am using all original parts and i send new screws with each case? also i understand the importance of occlusal excursions? very frustrating.......any ideas? thanks

 

[doug]

I'm gonna go with...did the doc make sure to torque it properly?

 

[amadent]

at the risk of sounding rude - witch this is not ment to be
is your DR torquing them down properly
you said you are sending new screws are you sending intra- oral screws or lab screws

Greg Amendola MDT

 

[BruceQuality]

Ditto...

I'm gonna go with...did the doc make sure to torque it properly?

That would be the first question to ask. Some docs don't seem to understand the importance of torqing properly. Our implant dept. has to explain it to one about once a week it seems. They don't like the idea of spending the money on torque wrenches, but they need to. It has been shown that the strongest man is only able to finger tighten one of these screws about a third to half of what they need to be torqued to. Very telling!!

Good luck!

 

[JohnWilson]

If he is using a torque wrench please make sure you are aware of the following info.

Make sure you do not have :

Premature contact on incline planes
Wide occ tables
Poor or point contacts to the marginal ridges.

You want to shoot for :

Minimal cantilever on free end units,

Meaning if you have a unit to restore in the first molar region and the fixture is more mesial turn it into a small molar or a 3rd bicuspid to eliminate off axis load.

You have to really remember when you stack the glass or wax in your occlusial contact that implants do not move like natural teeth do. If you routinely equilibrate your models for standard crown and bridge and build your crown into occlusion often times this gives you some freedom for the unit to not have premature occ contact , even if the docs staff doesn't make the best of temps. However since there is no PDL for implants they are rigid and you most allow for the adjacent dentition to compress when determining occ contact to the opposing.

 

[thewhitelab]

Thank you for your rapid response, I also should of mentioned it is mainly anterior crowns

 

[Ncm]

Is the doctor doing mainly metal abutments or Zirconia abutments also? With metal abutments (gold or Titanium) we can make the abutment as thin as we need it and not have to really worry about Dr's breaking the abutment when torquing, the screws on the other hand is another issue. I have had some Dr's that have overtorqued the screws and the screw head broke, and then your there trying to explain to the doctor how to remove the broken screw.

Reason i asked if the Dr is using Zirconia abutments; is if the Dr hasnt been torquing them properly and the zirconia abutments have been designed to thin, the abument may fracture after the proper torque.

Also if the Dr is doing multiple units , preferably in areas where esthetics are not a major issue, try recommending to splint the units to minimize screw loosening.

For some of our doctors, weve gone ahead and bought torque wrenches and when a Dr doesnt have one , we have them put down a full payment on the cost of the drivers to use it, they just pay shipping and handling. If they dont return it or they decide to keep it, the investment on the driver isnt lost.
Hopefully some of those ideas help out.

 

[Tunajoe]

Make sure the doc's torque wrench is calibrated....

 

[doug]

Thank you for your rapid response, I also should of mentioned it is mainly anterior crowns

I'm sticking with my first post, not torqued properly.

 

[24kt k9]

Tighten the screw to the proper Ncm and wait a couple of minutes then retighten to the same Ncm's. You will notice the screw has backed down a few Ncm's This is especially true with gold screws.

aka golden dog

 

[SiKBOY]

Tighten the screw to the proper Ncm and wait a couple of minutes then retighten to the same Ncm's. You will notice the screw has backed down a few Ncm's This is especially true with gold screws.

aka golden dog

you might be stretching the threads by doing this because of the soft gold. I think the screws are only meant to be used once. By doing this you are ultimately using the screw twice.

 

[Xydorf]

However since there is no PDL for implants they are rigid and you most allow for the adjacent dentition to compress when determining occ contact to the opposing.

Couldn't have said it better myself. Exactly what Misch speaks about in his books. I had the same problems with my small implant bridges before I:

1. Purchased a machine torque "wrench" from W&H and calibrated it to tighten the screws to 35ncm

2. Eliminated all interferences (sp?) in medio- and laterotrusion, and only allowed a light contact in IP. I also tell the lab nowadays to please eliminate the contacts before they send the job to me, so that I dont have to take the chairtime to do it myself.

Very nice to hear that some Lab Techs consider these aspects. Wish there were more of that kind

Regards,

Dr. John Barksenius DDS, Sweden

 

[Joshua]

It's a little different than using the screw twice. The initial loss of torque is thought to be due to "settling effect" - surface imperfections (roughness) are smoothed as the surfaces are clamped together from the initial tightening, with a resulting loss of preload. By waiting 10 minutes for this settling effect to occur and tightening to the desired torque a second time you can counter this loss of preload. This, along with some of the other above suggestions, might help.

BTW, there's not much about settling effect in the literature, but I did find this:
ler et al J Oral Implantol 2003 29(5) 242-5.

 

[saltydoc]

I work as a clinical assistant (see my own patients) at a prosthodontic office two days per week and there are usually two common causes:

1. Heavy occlusion (including incline planes as John Wilson mentioned)
2. Bruxism

The later is treated with a night guard.

 

[aidihra]

I received a case yesterday that had been in the mouth for 4 years. There was a pfm crown cemented on an Nobel Biocare Replace Select implant abutment and everything came out of the mouth in one peice. A hole was drilled from the occlusal and the Dentist can now screw it back into the patients mouth as if it was a screw-retained case.