Author's Note: This is Part 2 in my series on preexisting implants in full-arch reconstructions. The introduction article, “How to Use Preexisting Implants in Redesigning a Full-Arch Reconstruction,” was published first, and you can also read Part 1 in Digest.
Nowadays it is quite common to receive patients who have preexisting dental implants. This is no longer a novelty, and it will only become more common in the years to come.
The challenge in these situations is being able to navigate quickly and to provide the patient with acceptable solutions when they are dissatisfied with their preexisting ones. It's important to become an active listener to patients' concerns, desires and ultimately their treatment expectations.
Generally, it is recommended to wait 4-6 months to validate the esthetic, functional and structural performance of the prototype provisional restoration, as well as the motivation and hygiene of the patient before embarking on the fabrication of a definitive prosthesis at higher cost.
In this case, the patient presented one year after insertion of the prototype prosthesis, ready to continue with treatment.
After a thorough evaluation the following distinctive aspects were evident:
- Impeccable hygiene.
- Adequate structural integrity (minimal wear, absence of fractures).
- Very high motivation and gratitude from the patient.
As we were getting ready to proceed, it was important to consider the different potential design options for the patient:
- Titanium framework with denture teeth (conventional fixed-hybrid solution).
- Screw-retained, metal-ceramic prosthesis, with crowns cemented in the four maxillary incisors to compensate for the poor angulation of the implants and the exit of the screw access channel on the midfacial aspect of the anterior teeth (ISFDP).
- Screw retained Zr prosthesis with crowns cemented in four maxillary incisors (ISFDP).
Financially, a titanium bar with denture teeth would be the least costly of all three options, but the challenge with this design was the esthetic management of the obliteration of the screw access hole in the midfacial aspect of the three anterior teeth with composite resin and its eventual maintenance.
Once it was thoroughly explained to the patient, along with the inherent advantages that a ceramic restoration poses over utilizing denture teeth on a titanium bar, it was decided to make a CAD/CAM monolithic Zr framework with four cemented crowns on top of the four maxillary incisors.
Conceptually, we could manufacture the definitive prosthesis with a minimum number of additional steps, essentially, scan the prototype, make the design of the zirconium framework, using the previous information and fabricate CAD/CAM restorations with relative ease.
The only additional step here was to make an open tray analog impression of the implants, to fabricate a master cast.
Once the models, implant abutments and prototype had been digitized (Figures 1-3), as previously mentioned, the accesses to the implant screws in the anterior implants were located on the buccal area (Figure 4). It was decided to make individual crowns on the four incisors to cover the access holes to the screws and solve the esthetic problem.
With the zirconium framework, the four anterior crowns were designed (Figure 5) and milled, leaving minimal space for facial layering and, at the same time, gingival ceramic in the Zr framework (Figures 6-8).
Once the final prosthesis was finished, the titanium inserts were carefully cemented following adhesive cementation protocol using resin cement (Figure 9).
During the insertion appointment, it is necessary to validate the following elements (Figure 10):
- Ensure passive fit of the prosthesis
- Verify occlusion
- Validate that there is adequate space for hygiene
- Screw torquing protocol
- Obliterate access channels
- Cementation of the crowns
Once the passive seating of the prosthesis has been validated and the occlusion has been verified, as well as adequate access to hygiene, the screw-tightening protocol will be carried out, which consists of the following steps:
- Use new screws
- Use a calibrated torque wrench to ensure proper torque values
- Apply sequential torque, which allows you to avoid the embedment relaxation effect and ensure the appropriate pre-load on the screws. This guarantees that there will not be screw loosening problems later
- Once this phase is finished, the access holes are obliterated using Teflon tape and cementing is carried out
- Generally, a temporary cement can be used, when the geometry in the design of the structure provides ideal resistance and retention forms (length of the walls as well as the degree of convergence of the same), otherwise a resin-based cement can be used, which would eliminate the “retrievability” of the crowns if the framework needs to be removed in the future
As the following figures show, this restorative design successfully provided all the esthetic and functional goals sought out by the patient and our practice team — an esthetically pleasing fixed solution that provides adequate lip support in a sagittal view, a transitional line that is perfectly concealed underneath the lip, adequate hygiene access, and a structurally robust material that withstands the force of mastication (Figures 11-14).
The case presented illustrates an expedited process of converting an implant-supported removable design into a fixed design utilizing digital technology to design and manufacture not only the prototype provisional restoration but the definitive ceramic solution as well.
Ricardo Mitrani, D.D.S., M.S.D., is a member of Spear Resident Faculty.