Abstract
Large antral pseudocysts of the maxillary sinus (APCs) may hamper the elevation of the Schneiderian membrane during sinus grafting and may impair osteo-meatal complex patency after sinus augmentation. Therefore, these should be removed prior to or at the time of sinus grafting. This study presents a new technique that combines enucleation of large APCs during sinus grafting via a lateral approach with preservation of the Schneiderian membrane periosteal layer. Twelve patients underwent a sinus graft via lateral approach during the years 2004–2012. Simultaneous APC removal was achieved through a small additional bony access, preserving the integrity of the periosteal layer of the Schneiderian membrane. Nineteen implants were inserted at the time of sinus augmentation or during a second stage. Prosthetic rehabilitation was started at 4–6 months after implant placement. No patient developed surgical complications or APC recurrence. The survival rate of implants and related prostheses was 100% over a mean follow-up of 50 months (range 12–96 months) after completion of the prosthetic restorations. This technique may represent an effective procedure to achieve APC removal at the time of sinus grafting, preserving the integrity of the Schneiderian membrane periosteal layer.
The use of oral implants for prosthetic restoration of the edentulous posterior maxilla can be difficult or impossible when maxillary sinus expansion occurs in combination with a relevant reduction in the residual alveolar ridge height. Sinus floor augmentation via a lateral approach is a very well documented procedure to restore adequate bone volume in the posterior maxilla, allowing the placement of dental implants of adequate dimensions. Dental implants placed in grafted sinuses have shown excellent survival rates, consistent with those obtained for implants inserted in native bone.
Sinus grafting via a lateral approach consists of creating a bony window on the lateral wall of the maxillary sinus, elevating the Schneiderian membrane, and grafting the sub-sinus space with either autogenous bone, allografts, xenografts, alloplastic materials, or mixtures of these grafting materials. Although elevation of the sinus membrane modifies the maxillary sinus anatomy, it has been shown that this procedure does not affect sinus function in a significant way, as a limited part of the sinus is involved.
The sinus membrane is organized in three different layers: a thin band of periosteum (loosely adherent to the internal aspect of the sinus bony walls), a respiratory ciliated pseudostratified columnar epithelium (facing the sinus lumen), and a fine connective tissue layer (interposed between periosteum and epithelium). Clearance of the maxillary sinus is accomplished by the function of the respiratory epithelium. A mucous fluid is secreted by the sinus mucosa and is mobilized towards the sinus ostium by the ciliary movements, achieving drainage into the middle nasal meatus. To safeguard this sinus drainage through the osteo-meatal complex, the sinus floor elevation must preserve the patency of the ostium.
When sinus grafting is performed on non-pathological sinuses, no significant risk of ostium obstruction or sinus dysfunction has been reported, due to the very cranial position of the ostium. In contrast, when sinus grafting is performed in the presence of a pathological condition that significantly reduces the sinus lumen, the risk of ostium obstruction after sinus elevation may be increased. Such an occurrence may cause stasis of the mucous secretions within the sinus, eventually leading to a sinus infection.
Among the different pathoses that may affect the maxillary sinus, antral pseudocysts (APCs) represent a very common and benign clinical condition. These are found in approximately 7% of the adult population, are located primarily over the sinus floor, and are totally asymptomatic in the majority of patients. Their detection is usually fortuitous, following a routine radiographic assessment that reveals a typical well defined ‘dome-shaped’ radiopaque lesion. In the absence of clinical symptoms (which represents the most common condition), treatment is usually unnecessary. Furthermore, lesions regress spontaneously in approximately 30% of patients.
When patients are scheduled for sinus elevation and grafting, the presence of a small APC arising from the sinus floor rarely represents a significant contraindication to the procedure, as the risk of complications during surgery (such as membrane perforation) or after surgery (such as obstruction of the ostium) is very low. However, a large APC (occupying at least a third of the sinus volume) may interfere with membrane mobilization and impair osteo-meatal complex patency after completion of the grafting procedure. Such occurrences may respectively promote iatrogenic membrane perforation and sinus clearance dysfunction. Membrane perforations may be followed by contamination of the grafting material and/or its dispersion into the maxillary sinus, potentially leading to an inflammatory foreign body reaction and/or sinus infection. Ostium obstruction may lead to mucus accumulation within the maxillary sinus, loss of sinus ventilation, and sinus infection. Severe complications can potentially arise from this event, as the infection may extend towards other paranasal sinuses, the orbit, and even the cranial cavity. Therefore, the removal of large APCs prior to or during a sinus grafting procedure may be recommended.
Several approaches to sinus grafting in the presence of large APCs have been described, including removal of the pseudocyst via an intraoral approach followed by sinus grafting in a second stage, simple suctioning of the cystic liquid during sinus grafting, and removal of the pseudocyst with transnasal functional endoscopic sinus surgery (FESS).
The aim of this study was to describe the removal of large APCs at the same time as sinus floor elevation and grafting with a double intraoral approach. This approach allows the pseudocyst to be removed without violating the integrity of the Schneiderian membrane.
Materials and methods
Over an 8-year period (2004–2012), 12 systemically healthy patients (seven males and five females; mean age 40.8 years, range 21–55 years) presenting with edentulism of the posterior maxilla and a relevant reduction of the residual alveolar ridge height (<6 mm) were scheduled for maxillary sinus floor elevation via a lateral approach in order to allow the placement of oral implants. However, all patients presented with a large APC, involving at least a third of the maxillary sinus – a potential contraindication to sinus grafting for the reasons mentioned above.
Initial screening of these patients included: (1) evaluation of the residual dentition and periodontal status, (2) intraoral photographs, (3) panoramic and peri-apical radiographs (obtained by means of a Rinn film holder), (4) preoperative impressions, study models, and manufacturing of a diagnostic wax-up to optimize the final prosthetic restoration, and (5) computed tomography (CT) of the maxillofacial complex extended towards the cranial base, in order to include the osteo-meatal complex, the orbits, and the other paranasal sinuses.
Patient selection
Inclusion criteria were the following: (1) systemically healthy patient, (2) age over 18 years, (3) edentulism of the posterior maxilla combined with an expanded maxillary sinus and a residual alveolar ridge height <6 mm, (4) absence of significant vertical or horizontal resorption of the residual alveolar bone crest, with favourable inter-maxillary vertical and horizontal relationships, and (5) radiographic evidence of a well-defined ‘dome-shaped’ radiopaque lesion involving at least a third of the maxillary sinus, attributable to a large APC.
Exclusion criteria were the following: (1) compromised systemic health, (2) alcohol and smoking habit (>20 cigarettes per day), (3) severe liver or renal disease, (4) non-compensated diabetes, (5) current or past use of oral or parenteral bisphosphonates, (6) history of radiotherapy in the head and neck area, (7) antiblastic chemotherapy at the time of the first visit, (8) congenital or acquired immunodeficiency, including HIV, (9) autoimmune diseases of the oral mucosa including oral lichen planus, autoimmune blistering mucocutaneous diseases, and lupus erythematosus, (10) inadequate oral hygiene, (11) active periodontal disease at the time of first visit, (12) history of periodontal disease that had resolved less than 6 months prior to the first visit, and (13) non-compliance.
Surgical protocol
All patients were treated under local anaesthesia in sterile conditions by the first author. Preoperative patient preparation included (1) professional oral hygiene 2 weeks prior to surgery, (2) local antisepsis with 0.2% chlorhexidine mouthwashes starting 3 days before surgery, and (3) antibiotic prophylaxis with 2 g of oral amoxicillin and clavulanate, administered 1 h before surgery. Only one patient, who was allergic to penicillin derivatives, was treated with oral miocamycin 1200 mg, administered 1 h before surgery.
The surgical procedure started with a midcrestal incision in the edentulous site with mesial and distal vertical releases. The elevation of a full-thickness flap was extended more cranially as compared to a standard sinus grafting procedure, to provide sufficient bone exposure for the creation of an additional bony access for pseudocyst removal. A standard bony window was outlined with a diamond bur assembled on a straight hand-piece or piezoelectric instrument (Piezosurgery Touch Professional; Mectron s.p.a., Carasco, Genoa, Italy). The dimensions and shape of the window varied according to surgical needs and local anatomy. Particular care was taken not to tear the sinus membrane. Prior to membrane mobilization and sinus grafting, a small round-shaped additional bony access (2–4 mm diameter) was made with a round bur, approximately 10 mm above the cranial margin of the conventional sinus lift osteotomy, facing the anterior-lateral edge of the lesion. An intentional perforation of the membrane through the additional bony access allowed the underlying lesion, located between the periosteal and the epithelial layers of the sinus membrane, to be approached. As expected, a natural separation of the two anatomical layers had already resulted from the hydrostatic pressure generated by the liquid accumulated in the pseudocyst during its expansion.
Preliminary suction of the liquid was performed with a fine 23- or 25-gauge needle to significantly reduce the pseudocyst volume and simplify its removal. The ‘collapsed’ walls of the lesion were herniated through the small additional bony access with a fine suction tip and clamped with a tissue pliers. Slow enucleation was then achieved with gentle outward traction. The integrity of the periosteal layer of the Schneiderian membrane remaining over the sinus elevation site was verified constantly through the standard osteotomy created for sinus grafting. The surgical procedure was completed following the standard protocol for sinus grafting via a lateral approach. Briefly, the sinus membrane (periosteal layer) was elevated progressively with dedicated curved elevators, taking care not to tear it. Careful irrigation of the sinus lumen with sterile saline solution was performed through the micro-access to identify any leakage of liquid into the underlying sub-sinus cavity created for the grafting procedure. The sub-sinus space was then filled with a particulate xenogenic bone graft (bovine bone mineral, Bio-Oss; Geistlich Pharma AG, Wolhusen, Switzerland). A resorbable xenogenic collagen membrane (Bio-Gide; Geistlich Pharma AG) was positioned to cover the bony window and to stabilize the graft particles. Finally, the mucoperiosteal flap was released to obtain a tension-free closure with 4–0 sutures. Seven patients who presented with a residual alveolar bone height over 3 mm (therefore sufficient to guarantee primary implant stability) received 11 implants at the time of sinus elevation. The five remaining patients, who presented with a residual alveolar bone height insufficient to guarantee primary stability, received a total of eight implants 7–9 months later, after consolidation of the graft ( Table 1 ). All implants achieved very good primary stability in these five patients. Three different implant systems were used: (1) Straumann Implant System (Straumann AG, Basel, Switzerland); (2) Astra Tech Implant System (Dentsply International, York, PA, USA); (3) Nobel Biocare Implant System (Nobel Biocare, Zurich, Switzerland).
| Patient | Sex | Age, years | APC location | Date of surgery | Implant placement | Number of implants | Implant size, mm | Implant system | Prosthetic loading | Follow-up (months) |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | M | 37 | Left | 5/2005 | 2/2006 | 2 | 4.1 × 10 | Straumann | 7/2006 | 84 |
| 2 | M | 55 | Right | 11/2005 | Simultaneous | 2 | 4.1 × 10 | Straumann | 5/2006 | 96 |
| 3 | M | 47 | Left | 9/2006 | Simultaneous | 1 | 4.1 × 10 | Straumann | 3/2007 | 84 |
| 4 | F | 45 | Right | 10/2007 | Simultaneous | 1 | 3.75 × 10 | Nobel Biocare | 1/2008 | 60 |
| 5 | M | 29 | Left | 4/2008 | 11/2008 | 2 | 3.75 × 10 | Nobel Biocare | 4/2009 | 48 |
| 6 | M | 47 | Right | 7/2008 | Simultaneous | 1 | 4.0 × 10 | Dentsply Astra | 11/2008 | 48 |
| 7 | F | 49 | Right | 2/2009 | 11/2009 | 1 | 4.1 × 10 | Straumann | 4/2010 | 36 |
| 8 | M | 24 | Right | 4/2009 | 12/2009 | 1 | 4.1 × 10 | Straumann | 5/2009 | 48 |
| 9 | F | 45 | Left | 2/2010 | Simultaneous | 2 | 4.0 × 10 | Dentsply Astra | 6/2010 | 36 |
| 10 | M | 51 | Right | 11/2010 | Simultaneous | 2 | 4.0 × 10 | Dentsply Astra | 4/2011 | 24 |
| 11 | F | 21 | Left | 9/2011 | Simultaneous | 1 | 4.1 × 10 | Straumann | 1/2012 | 24 |
| 12 | F | 40 | Left | 5/2011 | 12/2011 | 1 | 4.1 × 10 | Straumann | 4/2012 | 12 |
| Average | 40.8 | 50 |
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