## 4 Discussion
This raises the question of the need for surgical treatment by FESS in favor of a single antibiotic therapy with further follow-up on signs and symptoms (with published references) for the treatment of sinusitis arising after zygomatic implant surgery. Further study is required on the analysis of associated risk factors to establish a prophylactic protocol beforehand, and to identify surgical or conservative responses later, for these cases of sinusitis. Unfortunately, the heterogeneity of the studies and the diagnostic and instrument tools used did not allow for a consistent result concerning this topic. In some cases, risk factors were found to have no relevance in facilitating sinusitis; however, this could not be stated conclusively because of lack of information about diagnosis of the disease and its assessment during the follow-up. For example, smoking and an average age over 52 years could be a predisposing factor for the onset of maxillary sinusitis with the need for close clinical and radiological follow-up. Considering this, the authors believe that the main focus has to be on the diagnostic protocol (radiological, probably) to gain sound information. Starting from here, the association between risk factors, surgical techniques and the onset of sinusitis could be clear, and advice in terms of follow-up and therapeutic strategies could be provided with confidence. Based on the results of this review, an otolaryngological approach should be combined with surgical and prosthetic rehabilitation, due to the occurrence of sinusitis after these kinds of procedures. Presumably, the otolaryngologist would be involved in the diagnostic and follow-up phases, as well as during the surgical procedure when an FESS is appropriate. Given the onset of sinusitis following the placement of ZIs, it may be appropriate to evaluate the feasibility of intraoperative FESS intervention, requiring interventions under general anesthesia. The authors are well aware of the difficulty in designing in vivo clinical studies, especially in heterogeneous cases like those of zygomatic implant surgery; however, performing a diagnosis of the status of maxillary sinus and monitor it during follow-up using instrumental tools is highly recommended. This allows the gathering of unambiguous information. Based on such information, a more predictable protocol could be established for treatment of sinusitis after zygomatic surgery and the potential need for referral to an otorhinolaryngologist. We observed that 8.8% of patients presented maxillary sinusitis with clinical relevance that needed pharmacological or surgical treatment. However, to date, there are no standardized therapeutic protocols described in the literature. In the analyzed papers, we found a heterogeneous approach in treating maxillary sinusitis. Some authors perform FESS in a contextual manner to prevent the onset of sinusitis, while others perform it only in the event of the onset of maxillary sinusitis. In most of the cases, antibiotic treatment was the prime choice. The present study has some limitations due to the nature of the literature reviewed. Most were clinical studies and data about diagnosis, radiology, surgical techniques and therapies were not often reported; this lack of information has to be considered. Because of this, a narrative review was carried out and it was impossible to determine exact guidelines for management of maxillary sinusitis following zygomatic implant surgery. Clinical conditions, the patients' health status and variables related to surgical procedures hindered the establishment of clear and sound guidelines in terms of management and therapy of this peculiar complication. Furthermore, maxillary sinusitis, the focus of the present work, often occurs with other side effects from this kind of surgery, and because of this it is impossible to establish strict protocols.