A RETROSPECTIVE MULTICENTRIC STUDY OF 56 PATIENTS TREATED WITH 92 PTERYGOID IMPLANTS FOR PARTIAL/ FULL ARCH IMPLANT SUPPORTED FIXED REHABILITATION: IMPLANT AND PROSTHESIS SUCCESS RATE

Osseointegrated implantology represents a reliable treatment solution to solve edentulism in jaws (1) in daily clinical practice. Insufficient bone amount and closeness to important anatomical landmarks could prevent implant placement. Each anatomical area is characterized by features and limitations (bone quality and quantity, nerve course, maxillary sinus cavity), which certainly conditioned/impacted this surgical procedure. Among all, the atrophic posterior maxilla represents a critical and demanding area in the patient’s rehabilitation through the insertion of integrated bone implants (2, 3) since it often lacks both in height and in thickness, thus preventing the placement of implants without adjunctive strategies (4). The presence of the maxillary sinus, an inadequate bone in terms of quality or amount, a large fatty marrow space or the rare presence of cortical bone covering the alveolus represent some of the critical aspects that surgeons could meet during the surgical approach. Regenerative techniques such as maxillary sinus elevation, block grafts, or Customized Bone Regeneration allow bypassing these anatomical criticalities, even if they are not free from long healing periods or donor site morbidity (5-8). In implant surgery, it is mandatory to minimize patients’ morbidity, especially if implant patients are getting older. Consequently, therapeutic, surgical procedures must be tailored to them and their ingrained features, systemic diseases, pharmacological therapies, and functional sinus impairment due to sinus lift augmentation (9). According to the current guidelines, daily clinical practice should consider the most cost-effective treatment equal to clinical efficacy. Although surgical reliability is well documented, there is still disagreement on clinical and prosthetic primacy techniques. Some suggest it could be a good practice to go beyond these critical issues, using shorter and wider diameter implants to reach a high bone implant surface contact (10, 11). Furthermore, biomechanical considerations such as the intense chewing forces acting in the atrophic posterior maxilla should not be forgotten. Ideally, a prosthetic cantilever should be avoided for this aspect (12): several complications could occur, such as screw and framework fracture, marginal bone loss or implant osteointegration loss. In the case of severe atrophic patients, the search for native bone can be extended beyond the anatomical limits of the oral cavity. So remote anchorage solutions could involve the pterygomaxillary complex composed of the maxillary tuberosity, the pyramidal process of the palatine bone and the pterygoid pillar. Pterygoid implants are typically placed in this zone to rehabilitate patients affected by severe maxillary atrophy (13). Bone availability in the maxillary tuberosity is highly variable and is based mainly on the adjacent maxillary sinus pneumatization amount. In 1989, Tulasne (14) introduced implant placement in the pterygoid region to overcome anatomical limitations due to atrophic alveolar bone. The pterygoid implant entails the fixture penetrating three specific osseous structures: maxillary tuberosity, the pyramidal process of the palatine bone and pterygoid pillar, and if it reaches osteointegration successfully, it offers support and stability to the final cantilever-free prosthesis. It significantly differs from tuberosity implant usually placed in the tuberosity region (mainly composed of 3 or 4 types of cancellous bone at the most distal portion of the maxillary alveolar process) and rarely with an angulation above 10 degrees. The pterygoid implants are usually placed with an angulation of 30 – 60 degrees relative to the horizontal maxillary plane, and they could offer support in partial and full arch prosthetic fixed rehabilitation. This anchorage satisfies surgeons and patients due to the time-consuming surgical strategy and favourable cost-benefit ratio. The aim of this study consists of the surgical and prosthetic success rate evaluation concerning the pterygoid implants placed (with a minimum torque of 45 Ncm) to support fixed partial or full arch rehabilitation without a cantilever. Its proposal consolidates the literature evidence with our shared experience, whose data were analyzed and interpreted according to a characteristic descriptive statistical analysis.

In the case of severe atrophic patients, the search for native bone can be extended beyond the anatomical limits of the oral cavity. So remote anchorage solutions could involve the pterygomaxillary complex composed of the maxillary tuberosity, the pyramidal process of the palatine bone and the pterygoid pillar. Pterygoid implants are typically placed in this zone to rehabilitate patients affected by severe maxillary atrophy. This study's aim consists of the surgical and prosthetic success rate evaluation concerning the pterygoid implants placed to support fixed partial or full arch rehabilitation without a cantilever. All team members designed and conceived this retrospective multicenter study (performed in three different clinical offices) to evaluate the reliability and predictability of this anatomically guided surgical tecnique without immediate loading. The study was successful with 100 per cent surgical success and all torque values >=45 N/cm considered as a threshold value. The series comprised 56 people who underwent 92 procedures. The male-to-female ratio was close to one (27 men, 29 women). The mean age (± SD) was 64.0±9.3 years (range 41-85 years). Only one prosthetic failure was recorded in a woman aged 67 years receiving a full arch pterygoid implant. Pterygoid implants supported by fixed rehabilitation represent a reliable strategic solution for treating severe atrophic posterior maxilla.