The patient had an implant placed in the region of upper central incisor 6 months ago. Now when trying to seat the crown it goes well until I try to torque it with torque wrench. The abutment screw engages when I screw it manually with a hand held driver until there is resistance and I can’t go on more. But as soon as I use the torque wrench the crown starts rotating a little bit. The internal hex position looks the same as on the model. The stability is good. No other symptoms.
What might be the reason? Could the internal hex get damaged? Doesn’t look like it though. Could the interproximal contacts somehow block the correct path of insertion by a slight margin?
Assuming everything that you say is correct and the fixture is not rotating due to loss of integration then the most likely cause is the use of copycat/knock off/inexpensive/aftermarket components. That is unless the fixture itself is something from a non-reputable company. I am convinced that all titanium implant fixtures, regardless of manufacturer, will successfully integrate at roughly the same rate but the difference between the good and the bad is in the precision craftsmanship at the prosthetic connection. Mixing parts regardless of compatibility claims and/or cutting corners with cheap components can and will cause this to occur. My suggestion would be to utilize a good lab that will use genuine manufacturer parts and pieces and help them out by using good stuff in the patient’s mouth.
I actually thought the same thing, but I always tend to look firstly for flaws in my activities. If it were for the implant rotation then the patient would have felt pain during torquing, right? Is it possible to damage internal hex by torquing in such situation?
I think anything is possible but cheap stuff is a big problem and the most likely culprit. Unfortunately a lot of the large commercial labs use aftermarket stuff and we are unaware or likely don’t care as long as the price is right and profit margin is safe. I know for me personally I recommend all of my referrals use a local lab out of Nashville called Mid South Dental Lab to eliminate this possibility. Yes I believe that your patient would have let you know, in a rather loud fashion, if the fixture was turning…
I think lab technicians are a lot like the dentist’s that they work with and are not opposed to trying a new product to improve the bottom line. If you ever care to look into it you will discover that there are as many options for aftermarket implant parts as there are composite resins and bonding agents. Probably a newer better and cheaper option was presented by a silver tongue salesperson and there you have it. I think it would be beneficial to check with your lab and make sure that they are using OEM parts and not some discount warehouse brand components as I honestly believe that this can make a huge difference. Not all labs are willing to deviate from their low cost low quality model so it is worth looking into.
did you take a PA to make sure the crown is fully seated? also a pic of the implant platform will indicate if the internal hex is damaged. and does the crown also rotate on the model when you torque (20Ncm) the abutment screw on the model (dont torque too high b/c the analogs are usually aluminum)? Did you also ask the lab which company did they order the abutment from? is it prefab or a cast custom abutment? what implant system are you using? post some pics would help us analyze your problem also. I usually don’t like to blame part problem when something is not fitting. as my dad tells me when we are playing golf “it’s not the arrows, it’s the Indians”
but abutments fabricated by the original company does go through more rigorous QC. i’ve visited Implant Direct HQ where they fabricate parts. it’s quite impressive. so if i use stock abutments. i usually include stock abutment fabricated by the company with my impressions.
Numerous studies ( finite element analysis ) report that when compared to OEM vs Generic or third party abutments the rotational misfit is greater , thus resulting the screw/abutment loosening. Statistical analysis say that the tolerance for misfit cannot be greater than 2 degree. If the third party parts can match this, you may be safe.
The same can be applied to tools/driver tips for implants. I have purchased a few of the generic universal torque wrench kits with multiple drivers to fit most every fixture and while they work they are not anywhere near as tight with the tolerance as the OEM drivers. Using these tools is like using a cheap end wrench from Wal Mart rather than a good quality Snap-On wrench and can lead to stripping out the hex head of the screw. If we just use good stuff and hold our lab accountable for also using good stuff a lot of issues can be eliminated. I guess in the end we get what we pay for…
We had a screw up where we told the lab that the implant was a size smaller that than the correct size. Had a similar problem, the abutment did not engage the hex.
You are correct and “we” should hold ourselves accountable for making sure the lab has the appropriate information so that they can use OEM parts for our cases. Unfortunately with all of the aftermarket stuff out there it can be difficult, if not impossible, for labs to track down the appropriate components. I have always preferred to make the labs job as easy as possible by providing them with the make and model of every screw which is further simplified by using screws from well known and established manufacturers.
To further compound the situation, a local lab got a parts milling machine, so his interest in non-OEM parts is high. With labs, you Hopefully get what you ask for.
I would encourage anyone interested to check out MiD-South Dental Lab out of Brentwood, TN. The owner, David, is a 3rd generation dental lab technician and the stuff coming out of this facility is second to none. I have no personal or financial affiliation with them but ever since being introduced nearly 10 years ago I have suggested their services to multiple referrals and never a negative review from any of the folks that I work with. I am sure that every area has a quality lab like this one but I know for a fact that he uses only OEM components and the end product is outstanding. Just a suggestion and I promise it will eliminate at least one variable…