Large Grafting Void Resembling a Surgical Ciliated Cyst following Maxillary Sinus Augmentation. Four Case Reports with Histological Observation

Abstract

The cause and pathogenicity of grafting voids following lateral maxillary sinus augmentation (MSA) have not yet been elucidated. The first purpose of this case series is to introduce an unusually large grafting void that radiologically resembles a surgical ciliated cyst (SCC) at the sinus augmented site; the second is to observe the histological findings of these grafting voids. In four patients, MSA was performed using the lateral window technique. An unusually large grafting void appeared on cone-beam-computed tomography (CBCT) taken one week after surgery and except for one patient, there were no clinical symptoms. On CBCT taken six months after surgery, the grafting voids were slightly smaller in size but showed radiographic findings similar to those of SCC. During uncovering, grafting voids were removed through the lateral window site. Histologically, the grafting void was empty or filled with dense connective tissue, and no ciliated columnar epithelium or inflammatory cells were observed. Within the limitations of this case series, the large grafting voids generated after MSA was not converted to SCCs. Rather, they remained scar tissue, which could infringe the sinus bone graft and affect the apical bone support of the implant.

Keywords: complication; grafting void; maxillary sinus augmentation; postoperative maxillary cyst; surgical ciliated cyst.

Figure 1

Case 1. (A) Preoperative panoramic radiography. A severe defect is present in the maxillary right posterior extraction socket, and the height of the residual bone is low; (B) panoramic image of CBCT taken preoperatively. A compromised extraction socket is observed in the right maxillary sinus, and the maxillary sinus membrane is thickened; (C) after the flap was reflected, the granulation tissue in the extraction socket was thoroughly removed. The buccal bone defect was severe. A lateral bone window was prepared for sinus floor elevation; (D) the maxillary sinus bone graft using synthetic bone graft substitute was performed and two implants were installed; (E) the peri-implant defect was additionally filled with a bone graft substitute; (F) resorbable collagen membrane was used to cover the grafting material and the flap was closed; (G) clinical findings 6 months after surgery. Healing was uneventful; (H) After the flap was reflected, the graft void was removed; (I) the removed specimen which was not clearly separated from the surrounding tissue; (J) after insertion of the healing abutment, the flap was closed; (K) Clinical appearance after delivery of the prosthesis.

Figure 2

(A) Histopathological findings of the removed specimen (H-E stain, M-T stain); (B) there were many empty spaces between tissues, and no ciliary clumnar epithelium and inflammatory cells were found; loose connective tissue and woven bone were observed.

Figure 3

(A) Coronal image of the CBCT taken immediately after surgery. There was no perforation of the maxillary sinus membrane and no leakage of the bone graft substitute; (B) coronal image of the CBCT taken one week after surgery. A severely enlarged grafting void was observed above the implant apex, and the ostium was obstructed due to severe membrane thickening; (C) coronal image of the CBCT taken 6 months after surgery. Although the grafting void was reduced in size, it appears similar to the SCC; (D) the radiopacity of the removed grafting void site was increased in the CBCT images taken 6 months after the prosthesis was delivered.

Figure 4

Case 2. (A) On preoperative panoramic radiography, severely atrophied residual ridges were observed in the missing area of the left and right maxillary molars, and the maxillary sinuses were pneumatized; (B) a panoramic image of the preoperative CBCT showed slight thickening of the sinus membrane on the sinus floor.

Figure 5

(A) After flap reflection, the lateral bone window was removed and sinus floor elevation was performed. There was no perforation of the maxillary sinus mucosa. Three osteotomy sites were perparated for implant placement; (B) the maxillary sinus was filled with xenograft material and the removed lateral window bone was repositioned. An implant was also placed. The flap was closed without barrier membrane covering; (C) the repositioned lateral bone window after 6 months of operation was well integrated with the adjacent native bone; (D) the previously repositioned lateral window was separated again to access the remaining large grafting void. The shiny appearance of the inner aspect of the removed specimen is the mucous membrane in contact with the grafting void, and to the left is the lateral window bone; (E) after the grafting void was removed, some perforation of the maxillary sinus mucosa was observed in the maxillary sinus bone graft; (F) after repair with resorbable collagen membrane, synthetic bone graft substitute was filled into the void.

Figure 6

(A) Histopathological findings of the removed specimen (H-E stain). On the left side of the specimen is the cortical layer of the lateral bone window. To the right of the bone is the maxillary sinus bone graft. The empty space on the far right is the grafting void; (B) soft tissue surrounding the grafting void connected to the bone graft was observed; (C) new bone formation was observed in the area adjacent to the lateral window; (D) the soft tissue surrounding the grafting void was dense connective tissue, and no epithelial cells were observed; (E) a large number of fibroblasts were distributed in the dense connective tissue, and no inflammatory cells were observed.

Figure 7

Coronal images of the CBCT were taken at multiple points during the healing process after surgery: (A) an image taken immediately after surgery; (B) an image taken one week after surgery. A large grafting void occurred over the apical half of the implant, and thickening of the maxillary sinus mucosa was also observed; (C) in the image 6 months after surgery, the size of the grafting void was slightly reduced. The void presents with a cystic appearance resembling SCC. The apical bony support of the implant was lost. The grafting void was removed and additional bone grafting was performed; (D) in the CBCT image taken 6 months after the prosthesis was delivered, it can be confirmed that the previous grafting void was replaced with a bone graft substitute.

Figure 8

Case 3. CBCT images taken immediately after maxillary sinus bone graft: (A) On the panoramic image of CBCT, a thickened mucosa on the sinus floor was observed above the bone graft; (B) Coronal image of the CBCT. (C,D) Images of the CBCT taken 6 months after surgery: (C) in the coronal image of the CBCT, large grafting voids with a cystic appearance were observed; (D) a well-defined radiolucent appearance was observed on an axial image of the CBCT.

Figure 9

(A) Six months after surgery, the flap for implant placement was reflected. At this time, the grafting void was accessed through the lateral window site; (B) the specimen was very fibrotic and was removed using a curette. The specimen was not well separated from the surrounding regenerated bone tissue. This may compromise the apical bony support for future implant placement; (C) the surface of the removed specimen was very irregular and no ciliated columnar epithelium was observed; (D) at high magnification, dense fibrotic tissue was observed and there was no infiltration of inflammatory cells.

Figure 10

Case 4. Preoperative panoramic radiography and CBCT scan were performed: (A) the left maxillary sinus was severely pneumatized and had minimal residual bone height; (B) in the maxillary sinus, membrane thickening was confined to the sinus floor and no sinus pathology was observed in the remaining areas.

Figure 11

(A) The ovular lateral window was formed using a surgical round bur on the buccal bone. The Schneiderian membrane was detached from the sinus floor and elevated. No perforation of the Schneiderian membrane occurred; (B) biphasic calcium phosphate was mixed with physiological saline and placed in the maxillary sinus. Three implants were simultaneously placed; (C) six months after the MSA, when the buccal flap was reflected, the buccal bone which was interconnected with the void was removed. Healing abutments were inserted into the implants; (D) gentle debridement and saline irrigation were performed on the removed voided site. The removed site was not refilled with a bone graft substitute.

Figure 12

(A) The removed specimen was fixed in 10% formalin solution for histopathological examination; (B) the specimen was examined after hematoxylin and eosin (H&E) staining. Newly formed bone and void tissue were clearly bordered; (C) new bone formation was found around the bone graft particles, and osteoblasts, osteocytes, and osteoclasts were observed; (D) no new bone formation was observed in the void area. Epithelial cells containing cilia were not observed in the void tissue which consisted only of dense connective tissue.

Figure 13

The coronal image of the CBCT scanned at the #27 implant site was examined: (A) in the image taken immediately after surgery, there was no leakage of bone graft particles; (B) however, a very large grafting void appeared in the image taken one week after surgery; (C) this grafting void showed a cystic appearance in the implant apex, although its size was reduced on CBCT taken after 6 months; (D) in CBCT taken 2 years after the grafting void was removed, the grafting void was replaced with new bone.