Revising Failing Implant-Retained Prosthetics

One exciting application of this advanced technology is the ability to revise former implant reconstructions that are ailing or failing. A critical aspect of the surgical precision that 3D planning offers is the ability to discover new sites for implant placement. In highly compromised situations, locating potential bone sites that were formerly undetectable on two-dimensional radiographs can create new possibilities for the next phase of treatment. Oftentimes, identification of these new sites can mean the difference between the success of a future prosthesis or the progressive failure of an aging one.

Together with 3D CBCT diagnosis, thorough evaluation of the edentulous sites, and the development of improved implant dimensions, the clinician can create new treatment options for patients with ailing dental implants. The following case provides an excellent example of the ways in which implant dentistry has advanced to provide revised treatment options for the compromised dental implant patient.^3-5

An 88-year-old female patient presented to the office with preexisting maxillary and mandibular fixed dental prostheses. This treatment, which had been completed in Europe 18 years earlier, had provided a relatively successful prosthetic solution to her edentulous condition. Both the maxillary and mandibular prostheses were screw-retained, acrylic hybrid designs that were fabricated with an underlying supportive metal framework.

A comprehensive dental examination was completed. The patient explained that she had grown increasingly unhappy with the esthetic appearance of the maxillary prosthesis. In addition, although she had been compliant with hygiene recalls in the past, which required complete disassembly of each prosthesis for access to perform the hygiene maintenance, she was becoming weary of this necessity because she was aging and having to deal with additional medical problems.

The examination revealed concerns with the overall stability of the maxillary prosthesis. Pterygoid and zygomatic implants had originally been placed to retain the maxillary prosthesis. The pterygoid implants had never been loaded because of chronic tissue irritation and the fact that their location made it difficult for the patient to access and clean the area; therefore, the zygomatic implants and four additional anterior implants were utilized to retain the prosthesis. The zygomatic implants had experienced significant bone loss over time. The upper left zygomatic implant demonstrated a 21-mm probing depth, and the upper right zygomatic implant had a 12-mm periodontal pocket. Both exhibited purulence and bleeding on probing. Because the patient was medically compromised due to cardiovascular disease, breast cancer, emphysema, diabetes, and a hip replacement, it was determined that the zygomatic implants were a potential source of infection that presented a considerable medical risk.

Structurally, the maxillary prosthesis exhibited severe occlusal wear, delamination, staining, and microleakage. The prosthesis also possessed the inherent defects associated with resin materials, requiring disassembly for routine dental hygiene and repairs of fractures and chips. The palatal location of the zygomatic implants and the design of the prosthesis resulted in significant palatal impingement, making it impossible to keep the area free of debris and biofilm and creating compromises in comfort and phonetics (Figure 1 and Figure 2).

Although the mandibular hybrid prosthesis also showed signs of aging, the patient did not have complaints associated with this prosthesis. The supporting implants were all well osseointegrated and showed no signs of failure. The patient's chief complaints were associated with the maxillary prosthesis (Figure 3).

Attention was focused on efforts to create a new prosthesis for the maxillary arch. The failing zygomatic implants presented a health hazard and required removal or burial. Considerations for additional implant support were imperative given the loss of the zygomatic implants. One possibility was to utilize short implants for the remaining areas that had limited vertical bone height and width. New implant designs featuring shorter lengths and smaller dimensions have been shown in the literature to be an effective treatment option with long-term success.^6-9

Using digital planning software, CBCT scan data was evaluated to determine the current condition of the underlying osseous structures and implants. The findings were favorable, revealing several potentially sound implant sites. Six potential implant sites were identified to provide evenly distributed support for the future prosthesis. Although the implant trajectories varied in orientation, the divergent implant access points could be corrected with the use of a cemented prosthesis (Figure 4 and Figure 5).

The maxillary prosthesis was removed, and the preexisting implant sites were confirmed. Impressions were taken for the fabrication of a new provisional restoration that would be retained by the four preexisting anterior implants and delivered at the end of the surgical appointment. The zygomatic implants were evaluated and confirmed to be significant sources of infection. The left zygomatic implant was in communication with the nasal cavity and suppurating. The right zygomatic implant, which could be probed to about two-thirds of the fixture length, was also bleeding and suppurating. Attempts to recover these implants using reverse torque were unsuccessful. After each implant was reduced to a subosseous level using carbide burs and the surrounding peri-implant tissues were debrided, the palatal tissues were approximated and sutured using chromic gut. The implants would remain unloaded and submerged beneath the tissue. Next, the preexisting abutments on the pterygoid implants were removed and replaced with cover screws, and then the implants were buried. A total of four additional implants were placed in locations that were preselected during the CBCT evaluation. This created an opportunity for a balanced load distribution of the implant-supported prosthesis for good mechanical stability and effective, less complicated hygiene maintenance (Figure 4 and Figure 5).¹⁰

A new, screw-retained provisional restoration was placed on the four preexisting implants to best serve the patient during the osseointegration phase of the four newly placed implants. Six months were allotted for complete osseointegration of the new implants. During this time, the submerged zygomatic implant sites healed uneventfully, demonstrating complete closure of the palatal tissues.

The patient's provisional restoration was developed from a diagnostic wax-up that improved upon the deficiencies found in the preexisting maxillary prosthesis (Figure 6). The healing phase allowed this prototype of the final restoration to be evaluated for maximum esthetics, function, and comfort. Once osseointegration was achieved, the restorative phase followed.

The final restorative design included a thin milled titanium bar with an overlying zirconia prosthesis to compensate for spatial limitations while providing strength and screw-retention for retrievability (Figure 7 through Figure 11).^11,12

Due to its strength and esthetics, zirconia has become a well-established, viable restorative material, and it is also well-suited for the fabrication of implant-retained full-arch prostheses.^13-17 Combining the strength of the zirconia with feldspathic porcelain veneering further maximizes the overall esthetic outcome (Figure 12 through Figure 16).¹⁸

Following treatment, the patient received detailed training regarding the provision of home care and committed to daily biofilm removal with her toothbrush, daily water irrigation with an antibacterial solution, and 12-week visits with the dental hygienist. She expressed her gratitude for the lack of infection and improvements in esthetics, function, and ease of maintenance (Figure 17 and Figure 18).

Patients with failing dental implant reconstructions can often benefit from emerging 3D technologies that have the capability to find new bony sites for additional support. In addition, previously failing older implant prostheses can be redesigned and executed with the aid of 3D technology and sound restorative designs.

Jacinthe M. Paquette, DDS
Private Practice
Newport Beach, California

Cherilyn G.
Sheets, DDS
Private Practice
Newport Beach, California

Cherilyn G.
Sheets, DDS
Private Practice
Newport Beach, California

David L.
Guichet, DDS
Private Practice
Orange, California