## 4 Discussion
Thus, although limited in its extent, this case series is the first systematic report of this possible complication in the setting of a common surgical pre-prosthetic procedure. Maxillary sinus augmentation is a successful and frequently used pre-prosthetic technique for augmentation of the dedentulous posterior maxilla [17]. However, there are well-known possible complications, including sinus membrane perforation, bleeding, infection, and resorption of the graft [18; 19]. Perforation of the Schneiderian membrane is the most common operative complication during sinus floor augmentation, and the incidence varies between 20% and 44% during the lateral window approach [18]. Another potential complication of sinus floor augmentation is SuCC. Initially, postoperative maxillary cysts were not related to sinus floor surgery. In general, this type of cyst was first reported by [PERSON] in 1927 [20] and emerged as a common lesion in Japan, accounting for 19.5% of all oral cystic lesions. Subsequently, these cystic lesions were defined as \"surgical ciliated cysts of the maxilla\" [21], with only a few cases being reported in the English-language literature [2; 22]. They can arise as a late complication of Caldwell-Luc operation for the treatment of maxillary sinusitis; however, the frequency of SuCC in this setting has seemed to decline since the introduction of endoscopy as an alternative conservative procedure. Other cases have occurred following mid-face orthognathic surgery [23] or genioplasty [24]. The SuCCs from our files occurred in the fifth to seventh decade of life, which is similar to the range reported in previous studies [4; 13; 14; 15; 16]. All our cysts were diagnosed up to three years following sinus floor augmentation, while three of the five cysts from the literature being diagnosed 5, 9, and 10 years following sinus floor surgery [13; 14; 15]. The dimension of the SuCCs reported by us were 1-1.5 cm in their greatest diameter. [PERSON] et al. [4] and [PERSON] et al. [16] reported similar cyst dimensions, diagnosed 6 months and 3 years after sinus floor augmentation, respectively. In contrast, [PERSON] [13] described a larger lesion, exceeding 4 cm in diameter, diagnosed five years following sinus floor augmentation. SuCCs, in general, can enlarge and expand with time, resulting in bone defects and thinning and perforation of the sinus walls to the point that they might mimic a malignant process [22; 25]. This emphasizes the importance of the follow-up, which can aid in identifying smaller lesions and curb progressive bone destruction caused by cyst expansion. In two of our cases (#1 and #3), the two implants involved in the cystic lesion were explanted, although it was reported that involved implants may not need to be explanted during the SuCC enucleation [14]. Despite the very few reports of SuCC following sinus floor augmentation, the possibility of occurrence may not be negligible, especially in view of the proposed formation process related to Schneiderian membrane entrapment. Mucosal entrapment can be caused by Schneiderian membrane tear, which is the most common complication of sinus floor augmentation [26; 27]. Perforations can occur due to inadequate surgical technique, the presence of septae, thin membranes, sinus pathology, sinus augmentation redo after failure, and overfilling at the time of graft placement [28]. In addition, an overestimation of approximately 2.5-fold in the assessment of the thickness of the Schneiderian membrane on CBCT images compared to the histological value has been reported [29]--a finding that could also increase the intraoperative risk of damaging the membrane. There is conflicting information in the literature regarding the effect of Schneiderian membrane perforation on postoperative infection and graft failure. Several studies have shown correlations between membrane perforation and acute sinusitis or graft infection [30; 31], whereas others have shown no association between membrane integrity and infection [32].