Statement of the problem: Quadrangular zygoma implants establishes an anterior maxillary canti-lever or a pseudo-Class III maxillo-mandibular relationship, secondary to posterior implants positioning into the zygoma, producing severe detrimental axial occlusal forces with anterior screws loosening, fractures and implants failure. Placing a fifth zygoma in the anterior maxillary area creates an ideal biomechanical design.
Materials and method: 30 patients (ages 29–66 average 47.5) underwent zygoma fixtures insertions to treat severe maxillary atrophy and be rehabilitated with hybrid dentures. The patient group treated with quadrangular were 5 and 25 with pentagonal. All patients were provisionally rehabilitated at the time of surgery and definitive prosthesis were installed within 2 months. A metallic structure was used to unite all the implants across arch, and either acrylic or porcelain dental fabrication were made. The fifth zygoma fixture was inserted from the alveolar bone, through the piriform rim into the infraorbital rim, anterior to the ocular globe and lacrimal duct.
Results: 2/5 patients treated with the quadrangular design had repetitive episodes of loosening and fracture screws, requiring the placement of the fifth anterior zygoma implant to eliminate the severe anterior maxillary prosthetic canti-lever. All patients showed satisfaction, even those who needed a secondary surgery to place the fifth zygoma fixture.
Conclusions: Patients with severe maxillary atrophy also concur with a pseudo-Class III maloclussion indicating the use of the pentagonal design to ideally distribute the masticatory forces along the metallic structure without cantilever.
Conflict of interest : None declared.