The case to be considered is a modified hybrid design with support for acrylic or composite at the gingival and crown preps to receive traditional crown and bridge as the suprastructure. They were unable to fabricate this particular full upper and lower because of the implant brand - Astra is not supported by the Nobel Procera Forte system. The case was further complicated by the combination of fixture and abutment level implants on the same arch.
The doctor’s lab technician wanted to wax up the bar and have it perfectly copy milled rather than have the case virtually designed in CAD software. Copy milling is the technology used by the Nobel Procera Forte system, and the doctor was comfortable with this method, rather than trying a virtual design (which is not available from the Forte). Overall, the complexity of this case required a solution that until recently we did not have available for a CAD/CAM manufactured implant bar.
Fortunately, with our new exclusive US distribution for Compartis ISUS implant bars and bridges, the solution was in our hands, and we were thrilled to take the case.
Copy milling is a standard offering with the ISUS system and since many customers call us wanting to “copy mill” their wax up bar design we are very pleased to be able to provide such restorations. The term copy mill comes from the key duplication business where an existing key is placed on one side of a machine and a blank on the other. As the key is traced by a probe, the other side moves a cutting instrument over the key blank. This creates an exact copy mill of the key. This was exemplified by the Celay milling machine and the term has since been adopted in dentistry.
Today, in most cases the wax up is not a copy mill in the same sense as a key or the Celay system. Instead, wax ups of bars are created, scanned and digitized and then milled from that digitized file. This is an important distinction as it would be difficult to truly “copy mill” such a complex geometric pattern as an implant bar. What’s great about this kind of copy milling for dentistry is the ability to do a true WYSIWYG (what you see is what you get) design which sometimes may be hard to create or visualize on a screen. Additionally, the model work with fixture replicas and abutments are also scanned and the files are merged. Once merged, the exact relation of the bar to the model can be seen virtually just as it would be in real life.
Let’s take a look at the case. The lab sent a very nice wax up of the bar along with the model work. Here we see the models with the abutment replicas as presented to us. All images are thumbnails and can be clicked to enlarge.
Maxillary model with six Astra Tech implant fixture replicas
- Mandibular model with six Astra Tech fixtures and abutment replicas
Since this was not to be an overdenture case, a denture wax up was not necessary. However the lab wanted us to exactly duplicate their wax up. Here are the wax ups provided by the lab on the models.
- Maxillary with hybrid wax up in place
View of mandibular with wax up in place
We evaluated the case and proceeded with scanning of all the parts. Shown below are the scans of the arches (shown with scanning flags) and then with the scanned wax up file. Note, the now digitized
Maxillary with scan flags after scanning
Maxillary scan of prosthetic to be milled perfectly mimics the wax up created by the customer.Mandibular with scan flags
- Lower image again validates the perfectly scanned provided by the customer. This will be a beautifull case!
- You can move the cross section through the entire arch to see the relationship of all the parts.
Currently, the viewer file has been sent to the doctor’s in house lab, and has been approved for milling. We posted these screen shots, but the approval is done through a 3D viewer file. The first time you do an implant bar or bridge with us, you will need to install the ISUS viewer software. This will allow you to open the case files, rotate, zoom, measure and more. If you do not want to install software, we can send you screen shots for approval before milling.
We’ll be posting more images as the case moves forward through the milling phase, through crown and bridge construction and upon insertion. Stay tuned!
