Implant therapy is a steadfast and versatile mode of treatment. Although dental technology, restorative materials and implant designs have evolved over the years, the basic concept behind implant-retained fixtures remains the same. As evidenced by the case that follows, today’s materials and technology can be used to restore implants that were placed decades ago.
The patient is a 69-year-old female with fully edentulous maxillary and mandibular arches. Prior to her original dental implant treatment, she had been wearing complete upper and lower dentures for over 30 years. Her chief complaint was that she could no longer tolerate removable dentures, as they were suddenly triggering severe gagging. Hence, she had not been wearing them, was having difficulty eating, and began to experience health challenges due to subsequent changes in her diet.
Based on her needs, wants and desires, the treatment plan called for the placement of eight implants in the maxilla to retain a ceramic-metal prosthesis cemented over fixed abutments. Five implants were placed in the mandible, and a screw-retained ceramic-metal prosthesis was attached to five Steri-OssTM PME Transmucosal Abutments (Nobel Biocare; Yorba Linda, Calif.). The implants were Steri-Oss machined titanium flat-tops with non-engaging connections.
After 23 years of function, one of the distal cantilevers of the mandibular prosthesis fractured, and the patient returned for examination and consultation. The panoramic radiograph revealed no measurable crestal bone loss and exhibited evidence of the left distal cantilever fracture (Fig. 1). Clinical examination revealed healthy pink, stippled soft tissue.
The patient stated that she wanted a new mandibular prosthesis. Though there would be some difficulty in doing so, as the implants were placed many years ago and the necessary parts to restore them would be difficult to locate, it was decided that every effort should be made to replace the original restoration.
An extensive search through the practice’s old implant parts inventory turned up five compatible implant transfer copings and five analogs.
Treatment began with the removal of the screw-retained bridge and the PME Transmucosal Abutments (Figs. 2a, 2b). Then, the five direct screw-in transfer copings were placed, and a closed-tray impression was taken using medium-body impression material (Fig. 3). After removing the impression tray and transfer copings, the impression copings were attached to the implant analogs and carefully seated back into the impression (Figs. 4a, 4b). The patient’s interocclusal records and impressions were then sent to Glidewell Laboratories in Newport Beach, California, for design and fabrication of the replacement prosthesis.
The original PME Transmucosal Abutments were placed back onto the mandibular implants, and the patient’s old prosthesis was screwed into place, providing the patient with adequate dental function during the course of treatment.
Due to changes in the patient’s soft tissue over the years, it was determined that utilizing custom abutments along with a cement-retained prosthesis would offer the best emergence profile, satisfy the patient’s esthetic demands and maximize support for the peri-implant soft tissue. Five compatible, straight abutments were located and sent to the lab so they could be modified in order to connect the new prosthesis to the implants.
The laboratory technician attached the straight abutments to the analogs in the master model and modified the abutments to receive a cement-retained all-zirconia prosthesis (Fig. 5). Then, the laboratory designed a replacement prosthesis using specialized CAD/CAM software, and fabricated an acrylic composite prosthesis for try-in and verification of fit, occlusion and esthetics (Figs. 6, 7).
Upon try-in, a 2 mm reduction in height was made to the anterior portion of the prosthesis. A new interocclusal record was taken, and the case was returned to the lab for fabrication of the final prosthesis. The final appliance was a 12-unit bridge fabricated from BruxZir® Solid Zirconia (Glidewell Laboratories) to ensure maximum durability and esthetics.
After receiving the final prosthesis from the lab, the abutments were transferred into correct position in the patient’s mandibular arch using abutment positioning jigs and torqued into place to 35 Ncm (Fig. 8). Lastly, the final 12-unit BruxZir implant bridge was cemented onto the abutments (Fig. 9). The patient was extremely happy with and thankful for the final prosthesis, which effectively restored comfort, function and esthetics to her mandibular arch.
In the decades since the patient’s implants were placed, implant therapy has seen countless advancements. Implant designs and treatment protocols have come a long way. Restorative materials are stronger than ever. Nonetheless, the basic concept of implantology remains unchanged. While CAD/CAM technology played a key role in the fabrication of the patient’s replacement prosthesis, the foundation of the restoration endures, and continues to provide effective oral function more than 23 years after the implants were placed.