Friday, November 22, 2013
By providing greater clinician control over the fabrication of restorations and a reduced turnaround time, CAD/CAM dentistry has certainly revolutionized the in-office experience for dentists and patients.
These benefits are not achieved through the sacrifice of quality, but rather by utilizing a more efficient process. A similar example is comparing regular mail to email. Both can get the same message across, but one is far faster, and more functional. Like email, CAD/CAM dentistry also offers increased functionality. With today’s chairside CAD/CAM systems we are no longer limited to single tooth restorations, but have the ability to make custom abutments or bridges.
This is a case in which we made a custom, implant-supported fixed partial denture provisional. We had already placed implants at the positions of teeth #19, 21 and 23. The patient still retained teeth #20 and 22. These teeth already had root canals, and had a very poor prognosis.
The model used for this case with soft tissue and the compromised teeth removed.
The first step was to acquire a fixture level impression. We did this with a traditional impression since it allowed us to quickly fabricate a model with soft tissue. Non-indexing temporary abutments were ordered for the Osseospeed implants from DENTSPLY Implants. These were quickly trimmed back so they did not interfere with occlusion. Teeth #20 and 22 were drilled off the model and ovate pontic spaces were created.
Non-indexing temporary abutments are added to the model.
The temporary abutments are trimmed back and the model is ready for scanning.
That model was scanned with the CEREC Omnicam, and margins were drawn at the base of the abutments. The exact placement of the margin in this case was not crucial considering it would be filled in later.
The model is scanned and the margins are marked.
The provisional bridge was designed and milled from a TelioCAD block. The screw accesses on the abutments were temporarily filled with wax to prevent any seepage of resin to the screw. The milled bridge was then placed back over and luted to the abutments using Perfectemp provisional material.
The temporary bridge was designed in the CAD software and sent to the mill.
The milled temporary bridge is placed back on the model and cemented to the abutments.
The screw holes were quickly found and the entire bridge with attached abutments was removed from the model. The gap at the margin was filled with flowable composite material, and polished before delivery.
Gaps at the margins are filled with flowable composite.
The entire process took about one hour, and most of that was waiting for the abutment to mill. The case did not have to be sent out to an outside lab which would have taken more time and added additional cost.
The temporary bridge ready for seating.
The completed temporary bridge seated.
Eventually, the goal would be to complete this type of case without having to use a physical model. Imagine if we could improve on the workflow in this way: A scanbody—such as the ScanPost from Sirona—is placed intraorally over the implants. These function in the same way as an impression coping for traditional impression materials. On the acquired digital model, we can edit and remove the teeth to be extracted. We also can digitally view the position of the implant. The case would be designed and milled in the same way, but designed instead to sit on an implant supported base, such as a TiBase. These would need to be non-indexed in the case of a bridge. The milled provisional could be attached to that, and be ready to go. Further, when it came time for a final impression, you would only need to grab a secondary scan of the tissue contours to show where healing has altered the tissue profile since you already know the position of the implants.
This would be an important advancement for cases in which a provisional is needed over an implant placed immediately after extraction, especially in the esthetic zone.
Have a comment on the case or something to add to a digital dentistry wishlist of your own? Drop a comment below!