# Prosthodtic Considerations for Customized Subperiosteal Implants: A Consensus Report
## 1 Introduction  
Customized subperiosteal implants (CSIs) were introduced in the 1940s as a treatment option for the rehabilitation of edentulous jaws and mandibles. Subsequently, they fell into disuse due to the development of important complications [1]. Indeed, the great majority of patients treated with first-generation CSIs had poor outcomes and low short- to medium-term survival rates. Nowadays, technological advances, such as computed tomography (CT), digital planning software and additive manufacturing by direct metal laser sintering, have allowed a new generation of CSIs to be manufactured with greaterprecision and better clinical outcomes. Indeed, the current devices are more biocompatible, have an improved fitting and are more stable, thus reducing the likelihood of developing complications [1, 2, 3, 4].  
These devices are specifically adapted to the anatomy of the patient and are indicated in cases where conventional endosseous dental implants are not feasible due to severe bone resorption. Other options such as zygomatic implants or major bone augmentation techniques are also available, but these treatments are usually technically demanding and time-consuming and have been associated with complications.  
CSIs are indicated in patients with insufficient bone to place conventional dental implants, as in type V and VI extreme bone atrophies [1, 5]. Furthermore, they are indicated for patients who refuse complex reconstructive techniques, or are unwilling to have removable prostheses. Thus, CSIs can be considered as an alternative to zygomatic implants [6] or endosseous implants requiring advanced bone grafting [2], or to correct severe defects after surgery in oncological patients [7]. CSIs are not recommended in patients with severe systemic pathologies or who are under therapies that contraindicate surgical procedures [6].  
The reduced postoperative morbidity is among the main advantages of CSIs, since the surgical procedures are usually faster and simpler in comparison with more invasive options like bone reconstruction surgeries [1, 2]. At present, CSIs are usually applied in patients with dedentulous resorbed maxilla, and can be loaded immediately. This is an important feature, since the patients can recover their aesthetics and function immediately after the surgical procedure, and this in turn improves their quality of life [2].  
Following completion of the restorative treatment, patients should undergo supportive therapy appointments every six months. These appointments are essential for the assessment of oral health status, the identification and management of risk factors and indicators, and the professional removal of plaque and biofilm from around the abutments and the implant-supported prosthesis [6].  
Despite their benefits, CSIs also pose significant challenges. Complications related to implant stability, integration with surrounding tissues, soft tissue dehisences and associated infections can occur. Other uncommon adverse events, such as CSI structural fractures associated with an inaccurate diagnosis or bone resorption due to infections, have also been reported [8]. The available literature contains limited long-term data regarding the success and complication rates for the new generation of CSIs and CADCAM prosthetic rehabilitations. Two studies report clinical data until 6 years of follow-up [2, 8]. A previous consensus paper about CSIs published by the current authors [6] addressed several clinically relevant topics but did not provide an in in-depth analysis of the main prosthodonic considerations or the prevention and management of complications associated with the prosthesis, which remain under-reported in the current literature. Due to the lack of standardized protocols for prosthetic rehabilitation, the aim of this paper was to provide a structured state-of-the-art review of the prosthodonic factors related with CSIs and to provide clinical guidelines to support decision-making and improve treatment outcomes.