## 1 Introduction  
Dental implants have revolutionized the rehabilitation of both the function and the form of missing teeth of partial/complete edentulous patients eligible for fixed rehabilitation with high long-term predictability with a literature success rate of over 95% [1, 2]. The literature shows that dental implants now have excellent long-term survivability and success in replacing missing teeth, improving chewing performance, esthetics, and biomechanics in partially or totally edentulous patients [3]. The more recent insights and state-of-the-art dental implants have produced innovative engineering strategies to improve the success rate according to the material composition of the fixture [4, 5], the micro- and macro-geometry [6, 7], the optimal surface roughness, and the interface with the surrounding tissues to improve the osseointegration process [8], avoid bacterial biofilms infection [9; 10] and risks factor of peri-implantitis [11; 12]. Today, dental implant supports have a success rate above 97% for 10 years [4; 13]. However, the loss of teeth causes bone atrophy, especially in the posterior maxilla, increasing the difficulty of placing the fixture [14; 15]. In fact, extraction of teeth in the maxillary posterior region causes a volumetric reduction of the bone ridge that is often accompanied by a coupled pneumatication of the maxillary sinus cavity with a consistent bone height reduction and the need for a regenerative approach for dental implant positioning [16; 17]. In fact, teeth extraction in the maxillary posterior region causes a pneumatization of the maxillary sinus with bone height reduction. So, after the loss of teeth, there may be insufficient bone for implant placement [18] that could require a subsequent regenerative technique with an increase in the failure rate of fixtures positioned in the posterior region of the maxilla [19]. [PERSON] et al. reported a dental implant success rate in the grafted site of 88.1%, consistently lower than the success rate in the case of fixtures positioned in native bone sites [20]. A maxillary sinus augmentation is extensively used to restore sufficient bone volume in the posterior maxilla, allowing for the placement of fixtures [21; 22]. In fact, implants inserted in combination with transcrestal techniques have obtained high survival rates even in the presence of residual bone height <5 mm, even if this surgical approach seems to be more appropriate and predictable in narrow rather than in wide sinuses [23; 24]. For maxillary sinus augmentation, several bone substitutes have been successfully purposed in literature, such as autologous, heterologous, and alloplastic grafts [25]. In bone regeneration procedures, the autologous bone substitutes are considered the optimal material according to their osteoconductive, inductive, and osteogenic properties. For this purpose, the preferential intra- or extra-oral donor sites are obtained by the iliac crest, mandible branch block, maxilla tuber process, calvarial graft, and tibial graft [26]. Before sinus lifting, it is important to evaluate the health of the sinus with cone beam computed tomography CBCT (Vatech(r) Ipax 3D PCH-6500, Fort Lee, NJ, USA) to exclude any pathology in the maxillary sinus, such as pseudo cyst, sinusitis, osteoma and the needs of eventual endoscopic procedure to support sinus ventilation [27]. In fact, the diagnostic exclusion of contextual upper respiratory atopy, inflammation, presence of nasal or paranasal polyps, and distress should be considered performing sinus lifting procedures [28]. In literature, very few studies described dental implant procedures in the presence of sinus osteoma [29], while no scientific articles described a coupled regenerative approach in this particular clinical occurrence. Paranasal sinus osteoma represents a very rare clinical occurrence, with an incidence ranging between 0.014% and 0.43% [30]. The purpose of the present case report was to describe a rare case of sinus osteoma used for implant support and review the relevant literature.