Digital Workflow to Maximize Your Cone Beam Investment: An Implant Case Study

Monday, November 12, 2012

I often write of how beneficial cone beam is when it comes to implant placement as well as diagnosis of pathology. Forget the vague interpretation of the often quoted “standard of care.” There is no need to have some lawyer define that term. Put simply, a 3-dimensional image is superior to a distorted 2-dimensional image.

For example, depending on the position of the patient in the focal trough, a panoramic image often will distort the height. Further, it completely misses anatomic landmarks such as the depression from a submandibular salivary gland.

But those advantages aside, one of the best uses for 3D imaging is to augment the quality and predictability of the work we do by facilitating guided surgery. Digital tools have made the process even more simplified, without compromising on accuracy. Below is a guided surgical case in which placed two implants in the patient’s upper right quadrant.

Pre-Op Radiograph

This patient had an existing crown on #5 with a previous root canal. We had the digital PA sent to us from another office for the original consultation. The crown had a distal custom attachment for a partial denture which was designed to provide retention and improved esthetics by avoiding the need for a clasp over the canine. I have never found those custom attachments to do well long term, and in this case it eventually snapped the crown off. The crown already had been recemented by the other office.

CEREC digital impression

An intraoral digital scan was done, and here you can easily visualize that attachment. The blue line represents the approximate position of a tooth in the position of #3. The final treatment plan was to extract the failing root at #5, and place two implants at #3 and #5 positions. The final restoration would be a fixed bridge, supported by two custom abutments over the implants. To help treatment plan the position at tooth #3, a virtual tooth was sculpted using the 3D tools in the software.

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The high resolution CEREC digital impression is then exported to the 3D cone beam software where the images are overlaid and fused together. I now have the ability to completely visualize the dimensions of the bone, as well as plan the position of the implant based on the best restorative position, (not necessarily based on where I think I have enough bone). This follows the principle that the restoration guides the position of the implant, not the jaw bone. If you do not have enough bone, then a graft may be a better approach.

Note that I can completely plan the position of the implant, even to the point of placing it within 1mm of the right maxillary sinus. There is no guesswork, or worry of perforation. The entire case is then sent digitally to SICAT, a German company, that will fabricate a surgical guide based on the position of the implants, and will fit perfectly to the 3D digital impression of the teeth.

On the day of the surgery, we removed the root tip. Since the coronal portion fell off right away, we elevated a flap in that area to ensure safe extraction and maximal preservation of bone tissue. For the implant at #3, a trephine tissue punch was used since we had adequate attached keratinized tissue. The implants were placed using the SICAT surgical guide according to the NobelGuide protocol.

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The final position of the implant and healing abutment can be visualized here, and you can see how accurate the placement is compared to the pre-op treatment plan.

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The three dimensional cutaway also shows how accurate the placement is—within 1 mm of the sinus. We had good torque on the implants, and closed #5 area with Gore-Tex sutures. For a provisional, we just added a tooth at #5 to her existing partial denture since the rests on #2 and #6 would keep the pressure off the implant healing abutments.

I have done many of these cases at this point, yet the digital workflow still amazes me. Note that we did not generate a single model to make the highly accurate scan. The workflow and predictability of implant surgery is just simply superior to the guesswork required with 2D imaging.

If you have a case you think would be great to share on Dentalcompare, let us know. Our goal is to highlight the ever-evolving world of dentistry, and the clinicians who are making it all happen.

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