Angled screw channels for screw retained implant crowns?

Nobel Angled Screw Channel Crown

Screw retained implant crowns are all the rage in dentistry. Cementable implant crowns fabricated over screw retained abutments are "out" according to most dental experts since screw retained crowns are more retrievable( they can be easily unscrewed and removed from the mouth without destroying an implant crown.).

The problem is not all implants are placed in a way that allows the screw hole for an implant crown to be placed in an appropriate place on it's occlusal surface. Having the access hole come out of the buccal of a crown could end up with a buccal composite filling in an area where esthetics maybe important.

When this happens, one solution is to use a custom cadcam abutment ( usually made from titanium or zirconium) and have a crown fabricated over it that can be cemented on. This solution can solve a few different problems for implants placed in a less than ideal angulation or in edentulous areas where interproximal contacts are not in alignment with that of the implant. In these situations a custom implant abutment acts like a custom post that can its angulation corrected so that it corrects this problem and allows a placement of an esthetic crown with good contacts to adjacent proximal teeth.This solution can  less than ideal for short implant crowns, since the cemented crown maybe more prone to come off after cementation ( due to there is insufficient length of the abutment to insure crown retention after cementation).

To better address this issue, implant companies have come out with angled screw channel implant crowns. These utilize cad cam computerized programs that can alter where the screw hole can be altered by as much as 25 degrees from the actual angulation of an implant. Since many implants are placed where the bone is optimal, many implants are placed with a buccal or lingual orientation which had previously cause the screw hole to be placed too buccal or lingual for traditional implant crowns.

I have tried this new technology with implant crowns from three different manufacturers ( Neoss, Nobel Biocare, and Staumann) They all seem to work and can be made with Zirconium crowns. I believe the Neoss and the Straumann can utilize  lithium disilicate crowns as well since they use a titanium sleeeve that is luted by the lab to the computer milled crown. The Nobel product is not luted to its titanuim sleeve, but instead has an ingenius design that allows the crown and the titanium part to be screwed into the implant simultaneously without the need for any luting of the crown to a titanium part.

Three part Nobel Biocare Crown ( crown, screw and titanium base)


All require specialized drivers that must be ordered prior to insertion since the normal drivers will not work. These drivers come in various lengths and care should be taken to order the proper length for your patients situation.

Lab sent me driver that was too long to be used in my patient's mouth!

I just inserted  a Srtaumann angulated screw channel crown  and evidently the lab didn't use Straumann genuine parts. When I inserted it, my angulated driver didn't work properly with this crown. I am still waiting for the lab to send me the proper driver! If my experience is representative, be prepared for unexpected glitches when doing one of thee new angulated implant crowns.  Be prepared to waste a little time while learning how to incorporate this new design into a dental practice. I suggest dentists reach out to their implant representative prior to fabrication of one of these new implant crowns. Also make sure to ask for genuine manufacturer's parts and figure out what length driver to order.




from Ask Dr. Spindel - http://lspindelnycdds.blogspot.com/2020/03/angled-screw-channels-for-screw.html - http://lspindelnycdds.blogspot.com/

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