Is it easy/possible to achieve passive fit with the twin conical Non-hex connections?

Is it easy/possible to achieve passive fit with the twin conical Non-hex connections (if not using cement retained or screwmentation technique)?

Robert Salisbury comments:

The true answer is joining two or more splinted abutments direct to conicals are technically impossible have them seal at the same time. The reason is they are tapered more than the actual implant allowing them to slip veryically while torquing. The way to prevent this is to put on a multi unit abutmrnt individually and then take an impression at the abutment flat top level. The additional vertical space is then hopfully at the right height fir the material strengh.

Think two brass compression fittings used in plumbing to seal two pieces together.
Steeper conicals slip more than shallow wider conicals.
The additional factor is the rotational wobble of the abutment implant interface.

Connical bone level implants are exactly that. Then the collar is in the abutment.
Some implants already have the collar ion them.
Placing a collar implant or conical implant uses similar type understanding if the biological width.
This is why you may hear that people sink the bone level subcrestal or sink the collar of the tissue level impmant. Simply because the Boner level is not at the right starting point to begin with.

Hope that helps.

Emil Svoboda comments:

Passive fit has little to do with abutment design, but rather the difference in the accuracy and alignment of the parts that are to be joined. The problem with the screw-in prosthesis installation technique is that the precision and accuracy of the prosthesis does not match that of the machined parts. The tolerances of the finished prosthesis is much higher (perhaps 60 to 150 microns plus) while the tolerances for error of the machined parts are about plus/minus 5 microns or so).

Hence the embedded high precision connectors are misaligned with their intended implant-connections in the mouth and cannot achieve a passive fit in the mouth. The error is expressed in the implant-abutment and/or abutment prosthesis connector joints. These are risk factors for peri-implant disease.

On the other hand, it is a lot easier to install abutments optimally to matching implants, one at a time. Now the abutment fits are optimized, and the Prosthesis Dimensional Error (PDE) will be expressed as open, overhanging and overextended margins, and submarginal cement … at the abutment margin level. Unfortunately the Chamfer and like margins were not designed to tolerate expected PDE. The Reverse Margin System was designed to prevent submarginal cement and tolerate PDE. Use it and optimize the fit of parts and eliminate the above risk factors for peri-implant disease. Great treatment for your patient - see Chamfer Margin Showdown … at :slight_smile: