Angled screw channels for screw-retained implant crowns?

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 its 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 may be 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 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 may be more prone to come off after cementation ( due to there is the 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 Straumann) 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 sleeve that is luted by the lab to the computer milled crown. The Nobel product is not luted to its titanium sleeve, but instead has an ingenious 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.

source:

lspindeldds.com

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