This was a really interesting case I teamed up with my friend Dr. Rusty Fitton on. Right now, it’s all the rage to restore an edentulous patient by cutting off a ton of bone and restoring them with an All-On-X restoration. However, there’s a lot of value in being able to preserve all that bone when possible and just restore them with old fashioned, crown and bridge dentistry. This was just such a case.
This patient had an ill fitting upper denture opposing natural dentition. The midline was way off and initially I felt there should be some additional length added.
I always preach that you have to start with the end in mind on these complex implant cases so since the existing denture was less than ideal, I wanted to figure out where the teeth belong first. A critical step in these types of cases is to cbct scan the patient (dual scan protocol) at the intended vertical dimension that you want to restore them at.
By doing this, the existing denture can be imported into Blue Sky Plan and used as a point of reference for redesigning the smile. The first step was that I did a new digital waxup in Exocad where I thought the teeth should be. I had Rusty print that model and make a putty matrix on it to transfer it to the mouth. Here are the results. It’s decent at normal smile.
At full smile, I think they’re too long.
Also, the midline is still not quite right
One of the huge benefits of digital is that rather paying $50 a unit for a new waxup, I can just pull the files back into the software and redesign the waxup based on the changes I want to make. The cost is a whopping $0.00. Here is what the redesigned waxup looked like- a little shorter and midline shifted even more. The blue is the initial waxup and the orange is the corrected one.
Now that I’ve finalized the tooth position, it’s time to plan the implant positions backwards from that.
This patient was a rare unicorn in that she had adequate bone everywhere that it was needed to position the implants such that the emergence of the screw positions was lingual to incisal edges and right through the occlusal tables of the posterior teeth.
Now here is where it gets interesting. It’s pretty easy to make a transitional prosthesis when you have a lot of bone reduction and a thick denture to convert into the prosthetic. However, when you’re trying to do it as a traditional bridge, every single millimeter of space counts and precision is critical.
My idea on this case was to actually make the interim bridge become the guide. Here’s how I did it. I opened the bridge in Meshmixer, a free CAD software, and I performed a Boolean subtraction of the guide tube positions from the bridge.
Then, I exported the guide tubes for the Blue Sky Bio Fully Guided Keyless Kit and combined them with the bridge.
In theory, the bridge can now be used as the surgical guide. The obvious problem is that there is so little tissue contact that indexing it becomes near impossible. It would really be a benefit to have a tissue base, similar to a denture base, to index this into position and maximize the contact area of the seating base. So to accomplish that, I created a “guide” directly on the tissue surface that had all the tubes turned off except for the pin tubes.
Now I need to find a way to combine this tissue base with the “bridge guide”. So to start, I open the “bridge guide” and I offset, or inflate it, by 1.5 mm. Then I perform a boolean subtraction of that inflated bridge from the tissue base.
Now import the “bridge guide” again.
Now, it’s beginning to come together…………a full arch “guide” and bridge in one. The only thing that I need to complete is to connect the two objects. This is easily accomplished in Meshmixer by using the select tool to select small areas of the bridge, “transforming” them and pulling them until they contact the tissue base.
This creates a single object that combines the bridge and the tissue base of the guide.
BOOM! This is the end result. It’s a full arch surgical guide that you can pin into place and perform the guided surgery though the guide, place the implants through the guide, seat the prosthetic components through the guide, and perform the pickup through the guide. Once the pickup is complete, the little sacrificial supports can be cut which allows the entire tissue base to fall away leaving the transitional bridge with all the implants connected.
This STL can be printed in crown and bridge resin or milled with a 5 axis mill in PMMA or composite. Finally, I incorporated some articulation pins that allow me to index the maxillary guide/prosthetic to the mandibular teeth. The enables me to create PVS bite matrix to properly position the guide into place before pinning it into it’s definitive position
Finally, I also printed the guide/restoration in NextDent Crown and Bridge Resin on the Moonray S printer.
For the surgery, Rusty will place this into the patient’s mouth, have them bite down into the putty bite to ensure everything is in the right position, then drill his pin holes to pin the guide into place. Once the pins are in place, he can perform guided surgery through the guide/bridge and place all the implants to their final positions.
The prosthetics can be placed and the pickup can be completed without ever removing the guide. Once everything has been picked up, the sacrificial supports can be removed allowing the tissue base to fall away leaving just the final bridge.
This is the first case I’ve ever designed like this but, if successful, this could change the entire paradigm of how we do guided surgery. As our printing materials advance, I feel this will become a preferred workflow when the case is suited to crown and bridge as opposed to a hybrid restoration.
I would love to know what you think. Let me know in the comments!