Managing Zygomatic Implant Failure With Pterygomaxillary Implant and Sinus Floor Elevation: A Technical Note

Abstract

This report describes a safe and staged protocol for managing the failure of a zygomatic implant complicated by severe sinusitis, using a pterygomaxillary implant and subsequent sinus floor elevation with intermediate implant placement. A 67-year-old male presented with a failed right zygomatic implant and refractory sinus infection 11 months after full-arch maxillary rehabilitation. After sectioning the zygomatic implant at the inferior border of the zygomatic arch, the authors inserted a pterygomaxillary implant and subsequent sinus floor elevation with intermediate implant placement to support a new restoration. The protocol successfully resolved the sinus infection and maintained prosthetic function throughout treatment. The final prosthesis, supported by the pterygomaxillary implant, the new intermediate implant, and the remaining stable implants, demonstrated good stability at the 1-year follow-up. Further long-term studies are needed to comprehensively evaluate the protocol’s efficacy and stability.

Rehabilitating the severely atrophied maxilla with implants is challenging, often necessitating complex bone graft procedures for axial implant insertion. Advancements in graftless treatments¹ have paved the way for minimally invasive therapy by using tilted implants,^2,3 which have comparable success rates and marginal bone loss to straight implants in full-arch rehabilitation.^4,5

In 2008, Bedrossian proposed a pragmatic treatment plan for the edentulous maxilla following a graftless approach, in which the alveolar bone supporting the maxillary anterior teeth is designated as zone 1, while the premolar region is considered zone 2, and the molar region zone 3.⁶ Since then, patients with adequate bone in zones 1 and 2 but bone deficiency in zone 3 due to large pneumatized maxillary sinuses have benefited from posteriorly tilted implants along the anterior wall of the maxillary sinus. For patients with bone deficiencies in zones 2 and 3, zygomatic implants facilitate immediate loading. Although full-arch rehabilitation achieves high success rates, failures occur. While conventional implant failures can be managed by removal and replacement, managing failed zygomatic implants remains challenging, with no standardized treatment protocol.⁷

Pterygomaxillary implants are implants placed in the maxillary retromolar region. By utilizing the bone in the tuberosity and pterygoid plate, these implants can achieve excellent stability and a high success rate with minimal invasiveness.^8,9 They help eliminate cantilevers and enable immediate loading. However, the extremely distal position of pterygomaxillary implants may result in a long, unsupported prosthetic span when connected to anterior implants, potentially compromising long-term prosthesis stability. Therefore, after zygomatic implant failure, an intermediate implant support is often necessary.

Herein, we describe a step-by-step solution for managing zygomatic implant failure in full-arch maxilla rehabilitation by using pterygomaxillary implants and a sinus floor elevation procedure.

CASE PRESENTATION

A 67-year-old man, a nonsmoker with no relevant systemic conditions and no known drug allergies, underwent full-arch implant rehabilitation of the maxilla using 2 TiUnite surface zygomatic implants (Brånemark System Zygoma TiU 50 mm; Nobel Biocare, Zurich, Switzerland) engaging the zygomatic bone in the posterior region with ZAGA 1 classification¹⁰ and 3 conventional implants (I5 4.2*16; AB Dental Implants, Ashdod, Israel) in the anterior maxilla (sites #12, #21, and #24). Eleven months after the final restoration, the patient presented with suppuration and clinical signs of peri-implantitis around the right zygomatic implant, along with continuous pyorrhea and headache. Cone beam computed tomography (CBCT) revealed severe bone resorption around the neck of the right zygomatic implant; the infection extended into the ethmoid, frontal, and sphenoid sinuses (Fig. 1). Despite antibiotic therapy and local rinsing, the symptoms persisted. After discussing with the patient, we reached a consensus to remove the failed zygomatic implant. As the patient refused an implant-supported overdenture, additional implants were planned for the right maxilla to support a fixed full-arch rehabilitation.

FIGURE 1.

Cone beam computed tomography shows bone resorption around the implant neck and diffuse sinus inflammation. (A) Panoramic view. (B)Buccopalatal view.

Surgical Procedure: Stage I

Given the presence of active infection, amoxicillin/clavulanic acid (1 g, TID) and metronidazole (500 mg, TID) were administered orally, starting 24 hours preoperatively and continuing for 7 days.

The existing prosthesis was removed. Under local anesthesia, a full-thickness mucoperiosteal flap was elevated to expose the zygomatic implant site and pterygomaxillary area. Preoperative planning with specialized software (Simplant Pro 17.01; Dentsply Sirona, Charlotte, NC) confirmed the angulation and trans-sinus trajectory of the planned pterygomaxillary implant. To prevent Schneiderian membrane perforation due to insufficient bone volume in the tuberosity, we created a bony window mesial to the implant site to elevate the Schneiderian membrane. Subsequently, the implant (Active 4318; Nobel Biocare) was inserted at a 70-degree angulation relative to the Frankfurt horizontal plane with an insertion torque of 45 N·cm, to allow immediate provisionalization (Fig. 2).

FIGURE 2.

Trans-sinus pterygomaxillary implant at the pterygomaxillary region. (A) Flap raise. (B) Insertion pathway. (C) Sinus membrane raise and pterygomaxillary implant insertion (white arrow: zygomatic implant; blue arrow: crestal window; green arrow: pterygomaxillary implant).

Using a large carbide bur, we partially removed the lateral wall of the maxillary sinus along the direction of the zygomatic implant placement to expose the extracorporeal portion of the implant. The zygomatic implant was then sectioned at the inferior border of the zygomatic arch using a high-speed turbine, and the implant was removed. Following implant removal, examination revealed a circumferential bone defect around the former implant neck, with partial absence of the lateral sinus wall. Subsequently, the area was irrigated with copious saline solution to remove titanium debris and secretions from the local tissues (Fig. 3). Finally, the wound was closed tightly with sutures. Postoperative CBCT scans demonstrated the ideal positioning of the pterygomaxillary implant and removal of the superior segment of the zygomatic implant. Postoperatively, the patient was instructed to report weekly on whether symptoms of sinusitis had alleviated. One month postoperatively, subjective symptoms of sinus inflammation had completely resolved. Three months postoperatively, CBCT revealed that the patient’s maxillary sinus showed normalized sinus membrane thickness, without persistent edema or thickening, compared with those captured on the immediate postoperative scan (Fig. 4). Following consultation with an otolaryngologist, it was confirmed that sinus floor elevation surgery could proceed.

FIGURE 3.

Failed zygomatic implant removal. (A) Lateral wall of the maxillary sinus. (B) Zygomatic implant section. (C) Zygomatic implant removal. (D) Sinus irrigation.

FIGURE 4.

Postoperative cone beam computed tomography immediately and 3 months later after zygomatic implant removal. (A) Immediate postoperative radiograph. (B) Three-month follow-up radiograph.

Surgical Procedure: Stage II

Amoxicillin/clavulanic acid (1 g, BID) was administered orally, starting 24 hours preoperatively and continuing for 7 days. A split-thickness flap was elevated at the site of the bony defect to minimize the risk of a large membrane perforation. The Schneiderian membrane was then elevated and repaired using a collagen membrane (15×20 mm, Haiao Biofilm; ZH-Bio, Yantai, China). The sinus cavity was grafted with particulate xenograft (1 g, Bio-Oss 0.5–1 mm; Geistlich, Wolhusen, Switzerland) and a resorbable collagen membrane (25×25 mm, Geistlich Bio-Gide) to cover the lateral window. Subsequently, the flap was sutured to achieve primary closure and facilitate uneventful healing (Fig. 5). Postoperative CBCT showed no effusion or air-fluid level within the maxillary sinus, with the bone graft appearing dense and achieving a vertical height of ∼13 mm at implant site #15.

FIGURE 5.

Schneiderian membrane repair and sinus floor elevation. (A) Intraoral view before the surgery. (B) Flap raise and sinus membrane dissection. (C) Sinus membrane repair with collagen membrane. (D) Sinus graft. (E) Collagen membrane protection. (F) Wound closure (white arrow: bone defect after zygomatic implant removal; blue arrow: crestal window created during pterygomaxillary implant insertion).

Surgical Procedure: Stage III

Six months after sinus augmentation, the surgical site at the right maxillary second premolar region was re-entered for implant placement. CBCT revealed significantly increased bone density and stable bone volume within the maxillary sinus. As an aseptic elective procedure, a standard prophylactic regimen of amoxicillin/clavulanic acid (1 g) was administered orally 1 hour preoperatively. Under local anesthesia, a full-thickness mucoperiosteal flap was elevated. The osteotomy was prepared sequentially according to the manufacturer’s protocol, and an intermediate implant (FX4010 SW; Dentium SuperLine II, South Korea) was inserted along an axis perpendicular to the occlusal plane with a final insertion torque of 35 N·cm. A transmucosal healing abutment (5.5×5 mm) was then connected to guide soft tissue healing. The flap was adapted and sutured. The postoperative healing was uneventful, without signs of infection, membrane exposure, or implant mobility.

Prosthetic Rehabilitation

Four months later, the patient received his final restoration (porcelain-fused-to-resin teeth arranged on a titanium framework). At the 1-year follow-up, the prosthesis and implants showed good stability (Fig. 6).

FIGURE 6.

Final restorations for the maxillary full arch. (A) Immediate postoperative radiograph. (B) One-year follow-up radiograph.

DISCUSSION AND CONCLUSIONS

Studies have confirmed a high success rate of zygomatic implants for severely atrophic maxillae; however, complications may still occur.^11,12 The most common biological complication associated with zygomatic implants is sinusitis. In most cases, conservative management can be used to control sinus inflammation in affected patients. However, if conservative treatment is ineffective, the unresolved inflammation may track retrograde along the implant. In this case, the intrasinus placement (ZAGA 1) likely enabled this pathway, resulting in total bone loss at the implant neck.¹³ In this situation, removing the zygomatic implant should be considered. Complete removal is an intricate and risky procedure, leading to the common practice of sectioning the zygomatic implant at the base of the zygomatic bone.

Two options can be adopted following zygomatic implant failure. The first option is to place a new zygomatic implant following a “double zygomatic” design; however, this requires excellent surgical skills, as the new zygomatic implant will have an unideal platform location restricted by the zygomatic anatomy. Furthermore, re-entry into an infected field carries a risk of recurrent infection and places the new implant at a potentially compromised site. In this context, the present case demonstrates an alternative, staged protocol. The use of a pterygomaxillary implant has 2 advantages. First, its engagement of dense bone ensures high primary stability, which is a prerequisite for the immediate loading protocol that facilitates rapid functional restoration. It then provides a stable distal abutment, transforming the prosthesis from a cantilevered design into a splinted bridge and reducing the risk of implant mechanical complications.

The primary challenge of the pterygomaxillary implant in this patient was the severely deficient bone volume in the tuberosity region. Therefore, a crestal window technique was performed to carefully detach the sinus floor membrane, ensuring the integrity of the Schneiderian membrane during pterygomaxillary implant placement. This maneuver prevented a membrane perforation that could have complicated subsequent sinus floor elevation and helped preserve adequate alveolar bone height around the implant neck for long-term osseointegration, reducing the risk of potential late-stage failure.

The staged nature of this protocol is a key strength. The sequence—placing the pterygomaxillary implant to secure the prosthesis; removing the failed zygomatic implant after confirming the good primary stability of the pterygomaxillary implant; allowing time for soft-tissue healing and resolving sinus pathology; performing sinus floor elevation to regenerate bone; and placing an intermediate implant—manages biological and technical risks. By separating the procedures, cumulative surgical trauma at any stage is minimized, permitting each site to heal under optimal conditions. Sinus floor elevation served a dual purpose: it created the bone volume necessary for placing a more favorably positioned intermediate implant and was essential for repairing the sinus ostium and restoring healthy sinus physiology.

Given the stability of the 4 remaining implants, the patient opted for a transitional prosthesis, partially reusing the original restoration owing to financial considerations. This highlights the practical flexibility of the approach, as it can be adapted to patient-specific circumstances. The successful 1-year follow-up indicates that this combination of a pterygomaxillary implant for distal support and a sinus floor elevation with a subsequent standard implant for intermediate support creates a biomechanically acceptable support for the final prosthesis. This distributes occlusal forces more evenly than the original configuration, potentially enhancing the long-term prognosis.

This study has limitations. First, this is a single case report. All findings and conclusions are derived from a single, complex clinical case; consequently, the results cannot be generalized to broader populations. Second, the follow-up duration is limited. The 1-year follow-up period, although sufficient to demonstrate procedural feasibility and observe short-term outcomes, is inadequate for assessing the long-term survival rate of the implants, the stability of the grafted bone, and the sustained health of the maxillary sinus. Therefore, studies with larger sample sizes and extended follow-up durations are warranted to validate the generalizability of this protocol and evaluate its long-term efficacy and stability.

This report outlines a feasible, cautious, and methodical protocol that leverages the benefits of a pterygomaxillary implant to provide immediate distal support, followed by a subsequent sinus floor elevation and standard implant placement to achieve optimal final prosthetic support. This approach mitigates surgical risks by avoiding immediate reimplantation in an infected site, provides flexibility in the surgical plan, and leads to a successful and patient-satisfactory rehabilitation.