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Management of a Large Mucous Retention Cyst at the Time of Sinus Floor Augmentations – A Case Report

October 1, 2014
by Avi Shelemay, DDS, MSc (Perio), FRCD(C); Scott Peterson, DDS


Sinus floor augmentation is widely utilized to augment the bone volume available for placing dental implants in the posterior maxilla. Dr. Hilt Tatum first introduced the procedure in 1974. Since then various modifications to the technique have been introduced and multiple grafting materials were utilized. In principle the procedure consists of creating a window through the lateral wall of the sinus to gain access into the maxillary sinus. Once the window is created the schneiderian membrane is reflected off the inner bony surfaces of the maxillary sinus to expose the floor and medial wall. Bone grafting material is placed into the void created. It is important to maintain the schneiderian membrane intact or ensure that any tears in the membrane are sealed because the membrane helps contain the grafting material. The rate of membrane tears and perforations has been greatly reduced through the use of Piezo surgical devices. When a small perforation or a tear does occur, it can be sealed by using a resorbable collagen membrane.

FIGURE 1. Endodontic failure as sown on a PA of tooth 27 with severe tipping and pneumatization of the maxillary sinus between teeth 25 and 27.

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FIGURE 2. Large mucous retention cyst occupying the left antrum (Panoramic film).

FIGURE 3A. Post-extraction radiograph demonstrating inadequate bone height for a dental implant in the edentulous space.

FIGURE 3B. & 3C. CT scan of demonstrating the extent of the mucous retention cyst in the left antrum.
 

Mucous retention cysts are often incidental findings when Cone Beam CT scans are done in preparation of the sinus lifts. They appear as rounded or dome-shaped opacities on the floor of the maxillary sinus. Most retention cysts either regress or show no significant change in size with time, therefore require no treatment; however, in the context of sinus floor augmentation, consideration must be given to their management. Small retention cysts can be left alone, provided that their displacement superiorly during the sinus floor augmentation will not block the maxillary sinus ostium. The maxillary ostium is an opening, connecting between maxillary sinuses and the nasal cavity. It is part of the ostiomeatal complex, providing drainage from the maxillary, frontal and eithmoidal sinuses into the middle meatus. Obstruction of any of these interconnected passages results in stagnation of secretion that may then become infected or perpetuate infection of the maxillary sinus. Alternatively, small to medium size retention cysts can be removed, leaving an opening in the Schneiderian membrane. Provided the cyst is not too large, the opening left behind can be sealed using a collagen membrane.

FIGURE 4. Pre-operative view of the edentulous site demonstrating facourable buccal-palatal ridge width.

FIGURE 5. Full thickness flap reflection exposing the lateral wall of the left maxillary sinus.

Larger retention cysts cannot be left alone, since their displacement superiorly during sinus floor augmentation is more likely to obstruct the maxillary ostium. Removing large retention cysts pose greater difficulty in sealing a sizable opening in the schneiderian membrane. This case report presents another option: reducing the size of the cyst by aspirating the fluid content of the cyst in conjunction with the sinus lift procedure.

FIGURE 6. Window in the lateral wall of the antrum, exposing the Schneiderian membrane.

FIGURE 7. Sinus curettes used to start the reflection of the Schneiderian membrane.

FIGURE 8A. & 8B. Aspiration of the cystic fluid through the Schneiderian membrane. Approximately 3cc of cystic fluid aspirated.
 

A 58-year-old patient presented with endodontic failure of tooth 27 (left maxillary second molar). The tooth had poor prognosis and extraction was recommended. The adjacent tooth 26 has been missing for years, and tooth 27 drifted mesially, closing the space completely. Review of a panoramic radiograph revealed a large mucous retention cyst in the left maxillary
sinus. The cyst extended superiorly from the floor of the sinus approximately 2.1cm. Tooth 27 was extracted uneventfully. Following four months of healing, a CT scan of the area revealed good ridge width and 2mm alveolar bone height in the edentulous site. The mucous retention cyst measured approximately 15mm superiorly from the floor of the sinus. Following a review of treatment options with the patient, the patient elected to proceed with an implant-supported crown as a means of replacement of the missing tooth. Staged sinus floor augmentation followed by implant placement after six months of healing.

FIGURE 9. View of the Schneiderian membrane after aspirating of the cystic fluid. The small puncture hole created with the 27 guage needle can be seen.

FIGURE 10. Placement of collagen membrane in to the antrum to seal the perforation in the Schneiderian memebrane and help support it to facilitate bone graft placement.

FIGURE 11. The collagen membrane is in position, supporting the Schneiderian membrane.
FIGURE 12. Layered approach to bone grading the maxillary sinus. Cortical particle are first introduced superiorly, followed by cancellous layer and a final cortical layer in the window.

The patient was placed on amoxicillin 500mg three times a day for one week, starting one day pre-operatively. Following administration of local anesthesia, full thickness flap was reflected to expose the lateral wall of the sinus at the missing tooth position. Round osteotomy was prepared utilizing a piezo device, exposing the Schneiderian membrane. A 10cc syringe with a 27 gauge needle was used to penetrate the schneiderian membrane and into the cystic cavity. Approximately 3cc of clear serum-like fluid was aspirated, before the schneiderian membrane was reflected from sinus floor and up the medial wall. Collagen membrane (BioMend®) was used to help and support the reflected membrane prior to placement of the bone graft into the space created. Large size particles (1-2mm) mineralized allogeneic bone (Puros®) was used. Cortical particles were placed first in the superior aspect, followed by cancellous particles. A final layer of cortical particles was placed to close the window. A second collagen membrane was placed over the window, and the buccal flap was sutured to achieve passive primary closure.

FIGURE 13. Second collagen membrane placed over the window.

FIGURE 14. Primary closure utilizing PTFE and chromic gut sutures.

Panoramic radiograph taken immediately post-operatively demonstrated good containment of the bone graft material. The patient was discharged home with routine post-operative instructions, including specific ‘sinus precautions’: sneezing through the mouth and no nose blowing.

FIGURE 15. Immediate post-operative panoramic radiograph demonstrating shrinkage of the mucous retention cyst and good containment of the bone graft at the edentulous space.

FIGURE 16. 2 weeks post-operative view, demonstrating favourable healing with primary closure.

The patient was seen in three weeks for suture removal. She reported minimal swelling and no bruising. She did not experience congestion, or any other sinus related symptoms. Pain management consisted of ibuprofen for the first two to three days. Intra-oral assessment revealed primary closure and no swelling or inflammation. A second follow-up occurred two months post-operatively, revealing uneventful healing. Panoramic radiograph taken at that visit revealed good containment of the bone graft, the sinus was clear and the residual cyst appear to have shrunk more relative to immediate post-operative panoramic radiograph.

FIGURE 17. 2 months post-operative panoramic radiograph demonstrating further shrinkage the mucous retention cyst and partial remodelling of the bone graft.

CONCLUSION
Aspiration of the fluid content of mucous retention cysts in the maxillary antrum present a more conservative option than removing the cysts, particularly when the size of the cyst is large. It remains to be seen whether the cysts recur and to what extent or size. OH


Dr. Shelemay maintains a private practice in Ottawa limited to periodontics and implant surgery, and is involved in implant training for dentists through LITE (liveimplant.com). Dr. Shelemay is a Fellow of the Royal College of Dentists of Canada in Periodontology. He obtained his DDS f
rom the University of Toronto in 1996, and subsequently completed a one year internship at Mount Sinai Hosptial. Dr. Shelemay completed his MSc degree and specialty training in Periodontology at the University of Toronto in 2002. Dr. Shelemay can be reached at avishelemay@me.com.

Dr. Peterson maintains a private practice in Kingston, Ontario focusing in surgery, including a special interest on implant related surgeries. He graduated from University of Western Ontario in 1986, followed by a one-year internship at St. Joseph’s and University hospitals in London, Ontario. During this year he was a member of the Prosthetic teaching team at University of Western Ontario dental school.  He has been a student of dental surgery through a vast array of continuing education. Dr. Peterson has been teaching hands on courses for small groups for the past ten years. LITE (Live Imlant Training and Education) was created in Collaboration with Dr.Shelemay three years ago.

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