Zygomatic implant placement with flapless computer-guided surgery: a proposed clinical protocol

The aim of the present report is to describe a procedure for zygomatic implant placement using image-guided implant surgery. This is an innovative technique and includes a new clinical approach to provide the direction to guide drilling.

The ethical committee of the University of Genoa approved the study. All patients had clinical indications of severe maxillary atrophy (Class 4 Cadwood-Howell). A total of 25 implants were placed, of which 17 were in the premaxilla, 7 in the zygomatic area, and 1 in the pterygoid bone. The treatment was performed in 2 phases. The first phase included cone-beam acquisition to exclude sinus disease and evaluate the anatomy of the residual premaxillary bone in 3 dimensions. The success of osseointegration achieved by the primary implants (PIs) was confirmed after temporary loading and before proceeding with the second phase, in which all patients were scheduled for zygomatic implants. A total of 3 or 4 regular platform MK III implants (17 in all) were placed in the premaxilla using conventional implant surgery. A model within the analogs of the PIs was prepared (master model), taking a conventional impression. Next, a radiologic template was prepared on the same master model and stabilized on the PIs, using dedicated prosthetic components. The guide was screwed onto the PIs during computed tomography acquisition to determine a fixed and repeatable position of the guide. In the second phase, after routine planning, a mucosa-supported stereolithographic SurgiGuide with sleeves for the zygomatic implants and the corresponding stereolithographic model, including the mucosa, were received from the manufacturers. The guide was repositioned on the master model to replace the sleeves for the PIs in the same position. With an original customized surgical kit, including an innovative intrasinus device, we next simulated surgery on the stereolithographic model to determine and control the direction of the osteotomies and the final depth of drilling. The SurgiGuide was anchored onto the PIs before the zygomatic osteotomy, after which flapless surgery was performed to place the zygomatic implants according to the plan.

Two PIs in the premaxillary area failed (and were replaced before the zygomatic step). No zygomatic implants failed. The follow-up examinations at 4 to 39 months showed good esthetic, phonetic, and functional results.

The results of the proposed surgical procedure appear to be encouraging. Although it is difficult to achieve the correct driven angle of osteotomies for zygomatic implants, in all patients we achieved correct zygomatic positioning, in agreement with previous planning. Additional research and randomized clinical trials are needed to assess the predictability of the procedure.