# Prosthodtic Considerations for Customized Subperiosteal Implants: A Consensus Report
## 4 Discussion  
Customized subperiosteal implants (CSIs) are an interesting solution for the prosthetic rehabilitation of patients with severe bone atrophy, where traditional approaches such as endosseous dental implants are not feasible [13]. CSIs sit directly on the bone surface and are screwed into anatomical buttress areas, thus avoiding structures such as the maxillary sinus, which might reduce the complications rate in comparison with zygomatic implants [8]. These devices have been successfully used in cases of bone augmentation failure [12,16] or after oncological surgery [16,17]. A recent systematic review [18] including data from 227 patients recorded a high short-term survival rate of 97.8%, with a median follow-up time of approximately two years. However, several limitations and complications associated with CSIs have been described in the literature. Some patients might present with soft-tissue inflammation that can be reverted by improving the oral hygiene or by changing the prosthetic design. Several reports have stated that soft tissue dehiscences leading to CSI exposure are common findings. On the other hand, CSI mobility is considered a major complication since it usually leads to implant failure, especially in patients with insufficient bone support. Finally, mechanical complications like the fracture of the prosthetic components or of the CSI structure can also appear [2,8]. The use of CSIs allows patients to restore functions such as chewing, phonation and swallowing, and also improves aesthetics, even in challenging cases with major defects [2,13]. Oral health-related quality of life (QoL) is a relevant outcome parameter in implant dentistry, since it takes into account the impact of treatments on different dimensions of patient life. A multicenter study [19] evaluated the quality of life of 40 patients rehabilitated with CSIs, showing very positive outcomes. Indeed, the results of the Oral Health Impact Profile (OHIP-14) questionnaire and of the visual analogue scales (VASs), measuring the patient's self-reported perception on aesthetics, comfort, masticatory function, phonation, hygiene and general satisfaction, were positive. Interestingly, the authors suggested that the improved prosthesis retention might play a crucial role, since most of the included patients had previously explored other treatment options or required multiple visits for adjustments and prosthetic relining. On the other hand, the impact of CSIs on the quality of life of the patients might also be related to the fact that these devices allow for an immediate loading protocol, thus limiting impairment of their social and working activities [16]. The customized design of these implants allows for a precise and passive fit on the remaining bone, optimizing both the initial stability and functional load distribution through robust structures [2,16]. To this end, the accuracy and quality of the preoperative CT scan is key to fabricating accurate and stable CSIs. For this reason, some authors recommend removing all teeth and/or implants prior to the CT scan, in order to avoid the presence of radiographic artifacts [14]. Moreover, the materials used in CSIs are non-ferromagnetic and are generally considered MRI-safe, although their presence may cause artifacts that could reduce the image quality. An osteotomy to remove remaining residual alveolar bone using surgical guides is an important step that should be carefully planned preoperatively. [PERSON] et al. [7]recommend osteectomies that are 3 mm in depth and 4 mm in width, starting apical to the mucogingival line. Proper placement and sizing of the osteectomies will allow for the correct seating of the CSI, close to the basal bone, which may reduce postsurgical bone remodeling [14]. This surgical maneuver reduces the risk of dehiscences around the CSI abutments, facilitates tissue management and may decrease CSI fatigue [14; 15]. A retrospective study reported a mean resorption rate of <0.5 mm in the crestal and in the supporting flap areas after one year of loading [20].