We present the clinical case of a 65-year-old patient with an implant-supported dentoalveolar rehabilitation on implants in the upper arch, placed in 2010, on which he referred pain, mobility and suppuration. After an orthopantomography, we observed a severe generalised perimplantitis in the upper arch, affecting all implants (Figure 1). It was explained to the patient that it was not possible to perform a bone regeneration of the lost tissues.

Under local anaesthesia, we disassembled the dentoalveolar hybrid prosthesis. It was only fixed by two implants that showed lower mobility. Periodontal curettage was performed in all areas adjacent to the lost implants and preprosthetic surgery to favour the closure of tissues with nonresorbable suture. A provisional complete prosthesis was placed during tissue healing time. Two months later, tissue healing was complete and no clinical signs of inflammation or pain were observed (Figure 2).

Given the degree of severe bone resorption after perimplantitis, the manufacture of an SI was planned as an alternative to the reconstruction of the upper maxilla with bone grafts, bilateral sinus lifts and subsequent placement of endosseal implants or surgery with zygomatic implants. With this type of reconstructions, it is also possible to perform an immediate load on the structure at the same time of the surgery.

For this purpose, intraoral photographs were made and the complete prosthesis of the patient was used for the different planning tests. First, the double scanning technique was used, adding different radiopaque markers with gutta percha in the prosthesis¹⁰ (Figure 3). Then, the scanning was obtained with a conical beam computerized tomography (CBCT), (Planmeca ProMax 3D, Helsinki, Finland), both the prosthesis and the patient with his prosthesis stabilized with a silicone bite registration (Figure 4). In addition, an intraoral scan of the patient’s prosthesis was performed. From this, a personalized structure was designed subperiosteal sintered in Titanium (Ti-6-4) (Custom 3D®) with 6 Multi-Unit® type connections (Branemark, Nobel Biocare) and fixed with osteosynthesis screws in the higher density and volume areas of the malar bone and upper jaw (Figure 5 and 6). At the same time, with the STL digital test of the planning of the mesh, and with the scanning of our complete prosthesis, the laboratory technician made an implantosupported rehabilitation milled in polymethylmethacrylate (PMMA) with Multi-Unit® type titanium interfaces for immediate loading (figures 7 and 8).

The surgical procedure was performed under general anaesthesia and nasotracheal intubation. A supracrestal incision and detachment of a maxillary flap of total thickness was made (Figures 9 and 10). The boundaries of the dissection were both infraorbital ridges, both laterally malar bodies and the anterior half of the hard palate caudally. In addition, a customized cutting guide was used so that the SI was completely in direct contact with the bone (Figure 11) and the mesh was fixed with the different 1.5 mm osteosynthesis screws in the nasal and zygomatic buttresses (KLS Martin, Freiburg, Germany) (Figure 12). The closure was performed with nonresorbable suture. Finally, the PMMA provisional rehabilitation was screwed for the immediate load, with a torque of 20 N on the implants (Figures 13-15).

Two months later, with the soft tissues healed around the connections (Figure 16), a new intraoral scanning was made of the implants and the provisional prosthesis for future restoration. A FRI type passivity test (rigid impression splint) was manufactured with an aluminium structure to assess the correct fit on the implants (Figure 17). For implant-supported rehabilitation, a sintered structure was made in chrome-cobalt with machined bases covered with acrylic resin teeth from Bredent® (Figures 18-21).

The patient has been checked every six months this year, performing X-rays and cleaning the structure, without finding any prosthetic or periodontal complications.

Implantological rehabilitation in patients with severe maxillary atrophies has always been a challenge for the surgeon11. The progress in diagnosis and planning, the improvement in regeneration techniques and the design of materials, represent an improvement in the resolution of these complex cases. However, complications may arise in these surgeries, increasing the morbidity, time and cost of the treatment for the patient¹².

The SI were widely used in the mid-50s, until the appearance of endoosseous implants, due to the ease of placement and rehabilitation¹³. However, the new technologies in titanium additive printing and 3D planning return to SI its role as a viable therapeutic alternative in severe maxillomandibular atrophies. The use of high-quality imaging tests and 3D planning programs allow to represent a patient’s residual bone volume with submillimetre accuracy. These data allow us to generate a virtual bone model, with which to adapt accurately the SI to the pre-existing anatomy¹⁴.

In 2009, Kusek published a clinical case of a rehabilitation on SI using CAD/CAM technology for the manufacture of a sterolythographic model in epoxy resin that was subsequently sent to the laboratory for the casting of structures¹⁵. In recent years, the additive technique of laser sintering for the manufacture of various structures in titanium and chromium-cobalt, is the one being used to process these subperiosteal implants.

In 2016, Cohen et al. published an in vitro study on the biological behaviour of SI structures produced in Ti6Al4V, using laser sintering and post-machining on different surfaces (SL)¹⁶. It demonstrated a high bone-implant contact, with a vertical growth histologically and histomorphometrically demonstrated.

In 2017, Mommaerts exposes a new design for the SI, using osteosynthesis screws fixed in the maxilla and malar zones, and various transmucosal connections are housed in the structure to screw the temporary or permanent prosthesis, using a digital protocol for this¹⁷.

The Cerea et al.¹⁸ retrospective clinical study includes the largest number of rehabilitated patients with this technique. It was performed on 70 patients with a two year follow-up. The maxilla and jaw of these patients were partially or totally rehabilitated with subperiosteal implants manufactured on laser sintered structures and a subsequent electropolishing process, making the surfaces completely smooth. The survival rate of the implants was 95.8% and the main postsurgical complications were pain, discomfort and swelling. There was an 8.9% rate of prosthetic complications.

In 2020, Mangano et al.¹⁹ published a study of 10 patients with mandibular atrophic posterior sectors. These were rehabilitated with SI manufactured on laser sintered structures and subsequent decontamination and sterilization with organic acids. Within a year, no implants had been lost and all complications were minor.

Today, SI rehabilitation has improved significantly due to the great advances in digital planning and CAD/CAM. Although more studies are needed, it is an alternative tool in cases of complex surgeries with large atrophies with the possibility, in addition, to perform an immediate load.