In cases with severe posterior bone atrophy, Pro Arch is a solution that helps the patient achieve a fixed rehabilitation. Straumann Guided Surgery and the coDiagnostiX® planning software can produce predictable results in cases with complex bone anatomy, or where implants are placed so as to obtain planned multi-unit angulation. With CARES® Visual we can obtain a precise framework fit on the original components, which is fundamental for the final rehabilitation.

Initial situation

A 70-year-old female in good general health presented at a private practice with an edentulous maxilla and partially edentulous mandible seeking a complete mouth rehabilitation. Conditions in the maxilla allowed satisfactory retention of a new complete denture which was accepted by the patient, while the mandible exhibited severe atrophy of the hard and soft tissues in the posterior regions and hopeless teeth in the frontal area, as observed clinically and confirmed by a CT scan (Fig. 1).

Treatment planning

Bone quality in the mandible allowed placement of four implants in the anterior region, with both lateral implants tilted, and did not allow any implants to be placed in the distal area. For these reasons a Pro Arch concept was chosen as a treatment modality. As bone conditions in the mandible were very difficult in terms of correct implant placement, it was decided to place them with the help of a surgical guide. The planning included several steps. First, the hopeless teeth in the mandible were to be extracted, following delivery of a complete immediate denture, as they did not offer any stable support for a surgical guide. Six weeks later, due to the lack of keratinized tissue in the premolar regions, apical repositioning and a free gingival graft were performed (Fig. 2). After 1.5 months the denture was relined with a mixture of barium sulfate and resin, transforming the denture into a radiological stent (Fig. 3). Another CT scan was recorded with the stent in the mouth (Fig. 4). The stone cast of the stent was poured (Fig. 5), giving us the actual clinical picture of the mucosa, and both cast and stent were scanned to obtain their STL files. Using the coDiagnostiX^® planning software, the radiopaque saddle of the stent and the STL scan were matched, which also allowed the stent to be matched with a cast as positive and negative, thus giving us the soft tissue volume. Implants were planned in a prosthetically-driven manner at sites #34, 32, 42, 44, with corresponding Screw Retained Abutments (Fig. 6). Because of an open-flap procedure due to the lack of keratinized tissue and the placement of long implants (all BLT 4.1x12 Roxolid^®, SLA^®), it was decided to make two surgical guides: first, a mucosa-supported guide only for drilling the Template Fixation Pins (Fig. 7), second, a pin-supported guide for fully guided implant placement (Fig. 8). The software can be used to choose an SRA in implant planning. Also, we can plan abutment placement with the engraving of implant rotation markers on the guide. This planning helps us stop at the right moment in terms of rotation at the very end of implant placement. We planned to convert the denture into an immediate temporary fixed restoration, with delivery of the final restoration in three months after implant placement.

Surgical procedure

On the day of surgery two bites were taken: first with the guide for the pins for stable drilling (Fig. 9), then with the existing prosthesis (Fig. 10), for its correct conversion into an immediate restoration. The first mucosa-supported guide was used for drilling the sites for Template Fixation Pins (Fig. 11). Next, the guide was removed, the flap was raised, and the second guide was fixed with the pins at the corresponding sites (Fig. 12). Implant beds were prepared (Fig. 13-14) and Straumann BLT implants placed with a torque setting of more than 35 Ncm, following the protocol to allow correct subsequent SRA placement (Fig. 15-16). Bone around the implants was prepared with Bone Profilers for the same reason (Fig. 17). The crest was flattened (Fig. 18-19), SRA abutments were screwed to 35 Ncm (Fig. 20) and covered with healing caps, and the wound was sutured (Fig. 21).

Prosthetic procedure

Provisional restoration

On the same day of the surgery, the existing denture was converted into an immediate temporary fixed restoration by adjusting it on temporary abutments directly in the mouth (Fig. 22), and an impression was taken as a double check. The restoration was tightened to 15 Ncm (Fig. 23). In 10 days, the sutures were removed, the control CT scan was recorded (Fig. 24), and the results were assessed with the coDiagnostiX^® evaluation tool.

Final restoration

Two months after the implant placement impressions were taken, the precision was checked with a verification Fig (Fig. 25-26). The vertical dimension of the provisional prosthesis was followed when mounting the casts in the articulator (Fig. 27-28). The analog set-up was tried in (Fig. 29), then scanned by the Straumann^® 7 Series scanner together with the model. The framework on Variobase^® abutments for SRA was designed in CARES^® Visual following the set-up anatomy (Fig. 30), then milled from titanium (Fig. 31). The passive fit of the framework was checked, and it was then veneered with resin with the denture teeth in place (Fig. 32-33). Variobase^® abutments were cemented into the prosthesis, and the final restoration was tightened to 15 Ncm (Fig. 34). Screw holes were closed with Teflon™ tape and composite.

Treatment outcomes

This case shows how digital technologies help achieve good results in complex surgical conditions and facilitate immediate predictable temporization. It demonstrates that correct prosthetically-driven implant planning results in a satisfactory final restoration.

Acknowledgments

Laboratory procedures

Framework: Alexandr Dolgolaptev
Veneering: Vyacheslav Bakaev.